title: Revolver

text: The term "automatic revolver" has two different meanings, the first being used in the late nineteenth and early twentieth centuries when "automatic" referred not to the operational mechanism of firing, but of extraction and ejection of spent casings. An "automatic revolver" in this context is one which extracts empty fired cases "automatically", i.e., upon breaking open the action, rather than requiring manual extraction of each case individually with a sliding rod or pin (as in the Colt Single Action Army design). This term was widely used in the advertising of the period as a way to distinguish such revolvers from the far more common rod-extraction types.


title: Revolver

text: In the second sense, "automatic revolver" refers to the mechanism of firing rather than extraction. Double-action revolvers use a long trigger pull to cock the hammer, thus negating the need to manually cock the hammer between shots. The disadvantage of this is that the long, heavy pull cocking the hammer makes the double-action revolver much harder to shoot accurately than a single-action revolver (although cocking the hammer of a double-action reduces the length and weight of the trigger pull). A rare class of revolvers, called automatic for its firing design, attempts to overcome this restriction, giving the high speed of a double-action with the trigger effort of a single-action. The Webley-Fosbery Automatic Revolver is the most famous commercial example. It was recoil-operated, and the cylinder and barrel recoiled backwards to cock the hammer and revolve the cylinder. Cam grooves were milled on the outside of the cylinder to provide a means of advancing to the next chamber—half a turn as the cylinder moved back, and half a turn as it moved forward. .38 caliber versions held eight shots, .455 caliber versions six. At the time, the few available automatic pistols were larger, less reliable, and more expensive. The automatic revolver was popular when it first came out, but was quickly superseded by the creation of reliable, inexpensive semi-automatic pistols.


title: Revolver

text: In 1997, the Mateba company developed a type of recoil-operated automatic revolver, commercially named the Mateba Autorevolver, which uses the recoil energy to auto-rotate a normal revolver cylinder holding six or seven cartridges, depending on the model. The company has made several versions of its Autorevolver, including longer-barrelled and carbine variations, chambered in .357 Magnum, .44 Magnum and .454 Casull.


title: Revolver

text: The Pancor Jackhammer is a combat shotgun based on a similar mechanism to an automatic revolver. It uses a blow-forward action to move the barrel forward (which unlocks it from the cylinder) and then rotate the cylinder and cock the hammer.


title: Revolver

text: Revolvers were not limited to handguns and as a longer barrelled arm is more useful in military applications than a sidearm, the idea was applied to both rifles and shotguns throughout the history of the revolver mechanism with mixed degrees of success.


title: Revolver

text: Revolving rifles were an attempt to increase the rate of fire of rifles by combining them with the revolving firing mechanism that had been developed earlier for revolving pistols. Colt began experimenting with revolving rifles in the early 19th century, making them in a variety of calibers and barrel lengths. Colt revolving rifles were the first repeating rifles adopted by the U.S. Government, but they had their problems. They were officially given to soldiers because of their rate of fire. But after firing six shots, the shooter had to take an excessive amount of time to reload. Also, on occasion Colt rifles discharged all their rounds at once, endangering the shooter. Even so, an early model was used in the Seminole Wars in 1838. During the Civil War a LeMat Carbine was made based on the LeMat revolver.


title: Revolver

text: Taurus manufactures a carbine variant of the Taurus Judge revolver along with its Australian partner company, Rossi known as the "Taurus/Rossi Circuit Judge". It comes in the original combination chambering of .45 Long Colt and .410 bore, as well as the .44 Magnum chambering and dual-cylinder .22LR/.22WMR model. The rifle has small blast shields attached to the cylinder to protect the shooter from hot gases escaping between the cylinder and barrel.


title: Revolver

text: Colt briefly manufactured several revolving shotguns that were met with mixed success. The Colt Model 1839 Shotgun was manufactured between 1839 and 1841. Later, the Colt Model 1855 Shotgun, based on the Model 1855 revolving rifle, was manufactured between 1860 and 1863. Because of their low production numbers and age they are among the rarest of all Colt firearms.


title: Revolver

text: The Armsel Striker was a modern take on the revolving shotgun that held 10 rounds of 12 Gauge ammunition in its cylinder. It was copied by Cobray as the Streetsweeper.


title: Revolver

text: As noted, the original Taurus/Rossi Circuit Judge is chambered to use both .45LC cartridges and .410 bore shells. However, it utilizes a rifled, rather than smooth-bore barrel.


title: Revolver

text: The MTs255 () is a shotgun fed by a 5-round internal revolving cylinder. It is produced by the TsKIB SOO, Central Design, and Research Bureau of Sporting and Hunting Arms. They are available in 12, 20, 28, and 32 gauges, and .410 bore.


title: Revolver

text: The Hawk MM-1, Milkor MGL, RG-6, and RGP-40 are grenade launchers that use a revolver action. Because the cylinders are much more massive, they use a spring-wound mechanism to index the cylinder.


title: Revolver

text: A six gun is a revolver that holds six cartridges. The cylinder in a six gun is often called a "wheel", and the six gun is itself often called a "wheel gun". Although a "six gun" can refer to any six-chambered revolver, it is typically a reference to the Colt Single Action Army, or its modern look-alikes such as the Ruger Vaquero and Beretta Stampede.


title: Revolver

text: Until the 1970s, when older-design revolvers such as the Colt Single Action Army and Ruger Blackhawk were re-engineered with drop safeties (such as firing pin blocks, hammer blocks, or transfer bars) that prevent the firing pin from contacting the cartridge's primer unless the trigger is pulled, safe carry required the hammer being positioned over an empty chamber, reducing the available cartridges from six to five, or, on some models, in between chambers on either a pin or in a groove for that purpose, thus keeping the full six rounds available. This kept the uncocked hammer from resting directly on the primer of a cartridge. If not used in this manner, the hammer rests directly on a primer and unintentional firing may occur if the gun is dropped or the hammer is struck. Some holster makers provided a thick leather thong to place underneath the hammer that both allowed the carry of a gun fully loaded with all six rounds and secured the gun in the holster to help prevent its accidental loss.


title: Revolver

text: Six guns are used commonly by single-action shooting enthusiasts in shooting competitions, designed to mimic the gunfights of the Old West, and for general target shooting, hunting and personal defense.


title: Erogenous zone

text: An erogenous zone (from Greek , "érōs" "love"; and English "-genous" "producing", from Greek , "-genḗs" "born") is an area of the human body that has heightened sensitivity, the stimulation of which may generate a sexual response, such as relaxation, sexual fantasies, sexual arousal and orgasm.


title: Erogenous zone

text: Erogenous zones are located all over the human body, but the sensitivity of each varies, and depends on concentrations of nerve endings that can provide pleasurable sensations when stimulated. The touching of another person's erogenous zone is regarded as an act of physical intimacy. Whether a person finds stimulation in these areas to be pleasurable or objectionable depends on a range of factors, including their level of arousal, the circumstances in which it takes place, the cultural context, the nature of the relationship between the partners, and the partners' personal histories.


title: Erogenous zone

text: Erogenous zones may be classified by the type of sexual response that they generate. Many people are gently aroused when their eyelids, eyebrows, temples, shoulders, hands, arms, and hair are subtly touched. Gently touching or stroking of these zones stimulates a partner during foreplay and increases the arousal level. Also, the gentle massage or stroke of the abdominal area along with kissing or simply touching the navel can be a type of stimulation.


title: Erogenous zone

text: Specific zones are associated with sexual response, and include the lips and nipples in addition to areas of the genitals, notably the foreskin and corona of the glans penis, clitoris and rest of the vulva, and perianal skin. The rete ridges of the epithelium are well-formed and more of the nerves are close to the external surface of the skin than in normal-haired skin. These zones have a high density of innervation, and may have an efficiency of wound healing and a capacity to stimulate generalized cerebral arousal.


title: Erogenous zone

text: In these zones, the skin is similar to normal-haired skin and has the normal high density of nerves and hair follicles. These areas include the sides and back of the neck, the inner arms, the axillae (armpits) and sides of the thorax (chest). An exaggerated tickle and anticipatory response are responsible for the heightened sensual response.


title: Erogenous zone

text: Males can be aroused by stimulation to the sides of the glans and penis, upper side of the glans, the foreskin, the front side of the scrotum, the skin between the scrotum and anus perineum, and around the anus. The prostate gland may be stimulated from inside the rectum, such as by anal sex, or by applying pressure on the base of the perineum near the anus.<ref name="Prostate/Hot spot"> (Last updated/reviewed on 28 March 2008)</ref> Men who report the sensation of prostate stimulation often give descriptions similar to females' accounts of G-spot stimulation.


title: Erogenous zone

text: Parts of the vulva, especially the clitoris, are erogenous zones. While the vagina is not especially sensitive as a whole, its lower third (the area close to the entrance) has concentrations of the nerve endings that can provide pleasurable sensations during sexual activity when stimulated; this is also called the anterior wall of the vagina or the outer one-third of the vagina, and it contains the majority of the vaginal nerve endings, making it more sensitive to touch than the inner two-thirds of the vaginal barrel.


title: Erogenous zone

text: Within the anterior wall of the vagina, there is a patch of ribbed rough tissue which has a texture that is sometimes described as similar to the palate (the roof of a mouth) or a raspberry, and may feel spongy when a woman is sexually aroused. This is the urethral sponge, which may also be the location of an area that some women report is an erogenous zone; this is sometimes called "the G-spot." When stimulated, it may lead to sexual arousal, an orgasm, or female ejaculation. The existence of the G-spot and whether or not it is a distinct structure is debated among researchers, as reports of its location vary from woman to woman, it appears to be nonexistent in some women, and scientists commonly believe that it is an extension of the clitoris.


title: Erogenous zone

text: The lips and tongue are sensitive and can be stimulated by kissing and licking. Biting at the lip can also provide stimulus.


title: Erogenous zone

text: The neck, clavicle area and the back of the neck are very sensitive, and can be stimulated by licking, kissing or light caressing. Some people also like being bitten gently in these areas, often to the point that a "hickey", or "love-bite" is formed.


title: Erogenous zone

text: Some people find whispering or breathing softly in the ear to be pleasurable and relaxing, as well as licking, biting, caressing and/or kissing it especially the area of and behind the earlobe.


title: Erogenous zone

text: The areola and nipple contain Golgi-Mazzoni, Vater-Pacini and genital corpuscles. No Meissner's corpuscles and few organized nerve endings are present. There are concentrations of nerve tissue in the area of ducts and masses of smooth muscle. The hair surrounding the areola adds additional sensory tissue. The mass of smooth muscle and glandular-duct tissue in the nipple and areola block the development of normal dermal nerve networks which are present in other erogenous regions and the development of special end organs. The entire breast has a network of nerve endings, and it has the same number of nerve endings no matter how large the breast is, so that larger breasts may need more stimulation than smaller ones.


title: Erogenous zone

text: Intense nipple stimulation may result in a surge in the production of oxytocin and prolactin which could have a significant effect on the individual's genitals, even to the point that some people of both sexes can achieve orgasm through nipple stimulation alone. Having the chest, breasts and nipples stimulated manually (hands), digitally (fingers, toes) and/or orally (mouth, lips, teeth, tongue) is a pleasurable experience for many people of both sexes.


title: Erogenous zone

text: Many people find stimulation (kissing, biting, scratching, tickling, caressing) of the abdomen to be pleasurable, especially close to the pubic region. It can cause strong arousal in men and women, in some even stronger than stimulation of the genitals. The navel is one of the many erogenous zones that has heightened sensitivity. In a 1982 study of eroticism in dress entitled "Skin to Skin", Prudence Glynn claimed that the waist symbolized virginity and that it was the first place that a man would touch a woman "when indicating more than a formal courtesy".


title: Erogenous zone

text: The navel and the region below when touched by the finger or the tip of the tongue result in the production of erotic sensations.


title: Erogenous zone

text: The skin of the arms, and specifically the softer skin of the inner arms and across the creased mid-arm bend covering the ventral side of the elbow, are highly sensitive to manual or oral stimulation. Caressing with fingers or tongue, more vigorous kneading, and butterfly kissing can initiate arousal and, in some cases, induce clitoral/vaginal orgasm or penile ejaculation without direct contact with the latter areas. The mid-arm bend is especially sensitive due to the thinner skin found there, which makes nerve endings more accessible. Arm sensitivity may be reduced or concentrated to a more narrow range by excessive muscularity or obesity on the one hand, or transformed to uncomfortable tenderness by excessive thinness on the other.


title: Erogenous zone

text: Some consider the armpits to be an erogenous zone, despite the similarity of the axillae (armpits) to normal-haired skin in both the density of nerves and hair follicles. Exaggerated or anticipated digital (fingers, toes) or oral (mouth, lips, tongue) stimulation is believed to be responsible for the heightened sensual response.


title: Erogenous zone

text: If pheromones exist for humans, they would likely be secreted by a mixture of liquid from the apocrine glands with other organic compounds in the body. George Preti, an organic chemist at the Monell Chemical Senses Center in Philadelphia and Winnefred Cutler of the University of Pennsylvania's psychology department, discovered that women with irregular menstrual cycles became regular when exposed to male underarm extracts. They hypothesized that the only explanation was that underarms contain pheromones, as there was no other explanation for the effects, which mirrored how pheromones affect other mammals.


title: Erogenous zone

text: The fingertips have many nerves and are responsive to very light touches, like the brushing of a tongue, light fingernail scratching or teeth stroking. The sides of the fingers are somewhat less sensitive and more ticklish. Both light and firmer touches work well at the junction of the fingers. Human fingertips are the second-most sensitive parts of the body, after the tongue.


title: Erogenous zone

text: Because of the concentration of nerve endings in the sole and digits of the human foot—and possibly due to the close proximity between the area of the brain dealing with tactile sensations from the feet and the area dealing with sensations from the genitals—the sensations produced by both the licking of the feet and sucking of toes can be pleasurable to some people. Similarly, massaging the sole of the foot can also produce stimulation. Many people are extremely ticklish in the foot area, especially on the soles.


title: Time Person of the Year

text: Person of the Year (called Man of the Year or Woman of the Year until 1999) is an annual issue of the United States news magazine and website "Time" featuring a person, a group, an idea, or an object that "for better or for worse ... has done the most to influence the events of the year". "Time" also runs an annual reader's poll that has no effect on the selection, which is made solely by the magazine's editors.


title: Time Person of the Year

text: The tradition of selecting a "Man of the Year" began in 1927, with "Time" editors contemplating the news makers of the year. The idea was also an attempt to remedy the editorial embarrassment earlier that year of not having aviator Charles Lindbergh on its cover following his historic transatlantic flight. By the end of the year, it was decided that a cover story featuring Lindbergh as the Man of the Year would serve both purposes.


title: Time Person of the Year

text: Since the list began, every serving president of the United States has been a Man or Person of the Year at least once with the exceptions of Calvin Coolidge (in office at time of the first issue), Herbert Hoover (the subsequent U.S. president), and Gerald Ford. Most were named Man or Person of the Year either the year they were elected or while they were in office; the only one to be given the title before being elected is Dwight D. Eisenhower, in 1944 as Supreme Commander of the Allied Invasion Force, eight years before his election. He subsequently received the title again in 1959, while in office. Franklin D. Roosevelt is the only person to have received the title three times, first as president-elect (1932) and later as the incumbent president (1934 and 1941).


title: Time Person of the Year

text: Lech Wałęsa and Nelson Mandela were chosen before becoming President of Poland and President of South Africa respectively.


title: Time Person of the Year

text: Before 1999, four women were granted the title as individuals: three as "Woman of the Year"—Wallis Simpson (1936), Queen Elizabeth II (1952), and Corazon Aquino (1986)—and one as half of the "Man and Wife of the Year", Soong Mei-ling (1937). "American Women" were recognized as a group in 1975. Other classes of people recognized comprise both men and women, such as "Hungarian Freedom Fighters" (1956), "U.S. Scientists" (1960), "The Inheritors" (1966), "The Middle Americans" (1969), "The American Soldier" (1950 and 2003), "You" (2006), "The Protester" (2011) represented on the cover by a woman, and "Ebola fighters" (2014). However, the title on the magazine remained "Man of The Year" for both the 1956 "Hungarian Freedom Fighter" and the 1966 "Twenty-five and Under" editions which both featured a woman standing behind a man, and "Men of the Year" on the 1960 "U.S. Scientists" edition which exclusively featured men on its cover. It was not until the 1969 edition on "The Middle Americans" that the title embraced "Man and Woman of the Year".


title: Time Person of the Year

text: In 1999, the title was changed to Person of the Year. Women who have been selected for recognition after the renaming include "The Whistleblowers" (Cynthia Cooper, Coleen Rowley, and Sherron Watkins) in 2002, Melinda Gates (jointly with Bill Gates and Bono) in 2005, Angela Merkel in 2015, "The Silence Breakers" in 2017, Greta Thunberg in 2019 and Kamala Harris (jointly with Joe Biden) in 2020.


title: Time Person of the Year

text: In 2020, to celebrate International Women's Day, "Time" editors released 89 new "Time" covers, each showing women, in addition to the 11 already chosen, as counterparts to the Person of the Year choices from the past century.


title: Time Person of the Year

text: Despite the name, the title is not just granted to individuals. Pairs of people such as married couples and political opponents, classes of people, and inanimate objects have all been selected for the special year-end issue.


title: Time Person of the Year

text: In 1949, Winston Churchill was named "Man of the Half-Century", and the last issue of 1989 named Mikhail Gorbachev as "Man of the Decade". The December 31, 1999 issue of "Time" named Albert Einstein the "". Franklin D. Roosevelt and Mahatma Gandhi were chosen as runners-up.


title: Time Person of the Year

text: Despite the magazine's frequent statements to the contrary, the designation is often regarded as an honor, and spoken of as an award or prize, simply based on many previous selections of admirable people. However, "Time" magazine points out that controversial figures such as Adolf Hitler (1938), Joseph Stalin (1939 and 1942), Nikita Khrushchev (1957) and Ayatollah Khomeini (1979) have also been granted the title for their impact on events.


title: Time Person of the Year

text: As a result of the public backlash it received from the United States for naming Khomeini as Man of the Year in 1979, "Time" has since shied away from using figures who are controversial in the United States for commercial reasons, fearing reductions in sales or advertising revenue.


title: Time Person of the Year

text: "Time"s Person of the Year 2001, immediately following the September 11, 2001 attacks, was New York City Mayor Rudy Giuliani. The stated rules of selection, the individual or group of individuals who have had the biggest effect on the year's news, made Osama bin Laden the more likely choice that year. The issue that declared Giuliani the Person of the Year included an article that mentioned "Time's" earlier decision to select Ayatollah Khomeini and the 1999 rejection of Hitler as "Person of the Century". The article seemed to imply that Osama bin Laden "was" a stronger candidate than Giuliani, as Adolf Hitler was a stronger candidate than Albert Einstein. The selections were ultimately based on what the magazine describes as who they believed had a stronger influence on history and who represented either the year or the century the most. According to "Time", Giuliani was selected for symbolizing the American response to the September 11th attacks, and Albert Einstein selected for representing a century of scientific exploration and wonder.


title: Time Person of the Year

text: In 1941, the fictional elephant Dumbo from the Disney movie of the same name was selected to be "Mammal of the Year", and a cover was created showing Dumbo in a formal portrait style. However, the attack on Pearl Harbor on December 7 pre-empted the cover. The U.S. president Franklin Delano Roosevelt was named Man of the Year for a record third time, although Dumbo's Mammal of the Year profile still appeared on the inside pages of the magazine.


title: Time Person of the Year

text: Filmmaker Michael Moore claims that director Mel Gibson cost him the opportunity to be Person of the Year alongside Gibson in 2004. Moore's controversial political documentary "Fahrenheit 9/11" became the highest-grossing documentary of all time the same year Gibson's "The Passion of the Christ" became a box-office success and also caused significant controversy. Moore said in an interview "I got a call right after the '04 election from an editor from "Time" Magazine. He said,' "Time" Magazine has picked you and Mel Gibson to be "Time"s Person of the Year to put on the cover, Right and Left, Mel and Mike. The only thing you have to do is pose for a picture with each other. And do an interview together.' I said 'OK.' They call Mel up, he agrees. They set the date and time in LA. I'm to fly there. He's flying from Australia. Something happens when he gets home ... Next thing, Mel calls up and says, 'I'm not doing it. I've thought it over and it is not the right thing to do.' So they put Bush on the cover."


title: Time Person of the Year

text: On November 24, 2017, U.S. President Donald Trump, who had been Person of the Year in 2016, posted on the social media network Twitter that "Time" editors had told him he would "probably" be named Person of the Year for a second time, conditional on an interview and photo shoot which he had refused. "Time" denied that they had made any such promises or conditions to Trump, who was named a runner-up.


title: Time Person of the Year

text: In addition to the main Person of the Year list, "Time" has acknowledged other impactful people or groups in other categories.


title: Time Person of the Year

text: "Time" magazine also holds an online poll for the readers to vote for who they believe to be the "Person of the Year". While many mistakenly believe the winner of the poll to be the "Person of the Year", the title, as mentioned above, is decided by the editors of "Time". "Time" continues to annually run an online poll for the "People's Choice", but stresses the decision on whom the magazine recognizes is not made by the poll, but by the magazine's editors.


title: Russian mafia

text: Russian organized crime or Russian mafia (, ), otherwise known as Bratva (), is a collective of various organized crime elements originating in the former Soviet Union. The initialism OPG is Organized Criminal ("prestupnaya" in Russian) Group, used to refer to any of the Russian mafia groups, sometimes modified with a specific name, e.g. Orekhovskaya OPG. Sometimes the initialism is translated and OCG is used.


title: Russian mafia

text: Organized crime in Russia began in the Russian Empire, but it was not until the Soviet era that "vory v zakone" ("thieves-in-law") emerged as leaders of prison groups in forced labor camps, and their honor code became more defined. With the end of World War II, the death of Joseph Stalin, and the fall of the Soviet Union, more gangs emerged in a flourishing black market, exploiting the unstable governments of the former Republics. Louis Freeh, former director of the FBI, said that the Russian mafia posed the greatest threat to U.S. national security in the mid-1990s.


title: Russian mafia

text: In 2012, there were as many as 6,000 groups, with more than 200 of them having a global reach. Criminals of these various groups are either former prison members, corrupt officials and business leaders, people with ethnic ties, or people from the same region with shared criminal experiences and leaders. In December 2009, Timur Lakhonin, the head of the Russian National Central Bureau of Interpol, stated "Certainly, there is crime involving our former compatriots abroad, but there is no data suggesting that an organized structure of criminal groups comprising former Russians exists abroad", while in August 2010, Alain Bauer, a French criminologist, said that it "is one of the best structured criminal organizations in Europe, with a quasi-military operation."


title: Russian mafia

text: The Russian mafia is similar to the Italian Mafia in many ways, the groups' organization and structure follow a similar model. The two groups also share a similar portfolio of criminal activity. The highly publicized Italian Mafia is believed to have inspired early criminal groups in Russia to form Mafia-like organizations, eventually spawning their own version. The Russian mafia, however, differed from the Italians due to their environment. The level of political corruption and arms sales in a post-Soviet Russia allowed for massive expansion and incorporation of many government officials into the crime syndicates. The Russians also dabbled in uranium trading, stolen from the Soviet nuclear program, and human trafficking.


title: Russian mafia

text: The Russian criminality can be traced back to Russia's imperial period, which began in the 1720s, in the form of banditry and thievery. Most of the population were peasants, in poverty at the time, and criminals who stole from government entities and divided profits among the people earned Robin Hood-like status, being viewed as protectors of the poor and becoming folk heroes. In time, the "Vorovskoy Mir" (Thieves' World) emerged as these criminals grouped and started their own code of conduct that was based on strict loyalty with one another and opposition against the government.


title: Russian mafia

text: Joseph Stalin was a crime boss and gangster during the early 1900's. Amid growing violence, Stalin formed his own armed Red Battle Squads. They raised funds through a protection racket on large local businesses and mines. Stalin also established a small group which he called the Bolshevik Expropriators Club, although it would more widely be known as the Group or Outfit. Containing about ten members, three of whom were women, the group procured arms, facilitated prison escapes, raided banks, and executed traitors. (See Early Life of Joseph Stalin)


title: Russian mafia

text: When the Bolshevik Revolution came around in 1917, the Thieves' World was alive and active. Vladimir Lenin attempted to wipe them out, but failed, and the criminals survived into Joseph Stalin's reign.


title: Russian mafia

text: Russian organized crime is also unique in that it does not possess a clearly defined, top-down hierarchy. Unlike the Italian mafias, with their capofamiglia, or the Chinese triads, with their “mountain masters,” the Russian Mafia structural ranking does not include irreplaceable leaders. It would be impossible to take down a few “heads<nowiki>"</nowiki> of the Red Mafia in order to topple the entire organization because they simply do not exist. This gives ROC an invaluable strategic advantage over those attempting to dismantle it.


title: Russian mafia

text: The main difference between Russian and Italian mafia is that Italian mafia uses murders and thefts as the main methods of violence. The Russian mafia groups use extortion, credit card fraud, murder, kidnap, and fuel frauds (Friedman 2000, p. 160-161).


title: Russian mafia

text: During Stalin's reign as ruler, millions of people were sent to "gulags" (Soviet labor camps), where powerful criminals worked their way up to become "vorami v zakone" ("thieves-in-law"). These criminal elites often conveyed their status through complicated tattoos, symbols still used by Russian mobsters.


title: Russian mafia

text: After Hitler's invasion of the Soviet Union during World War II, Stalin was recruiting more men to fight for the nation, offering prisoners freedom if they joined the army. Many flocked to help out in the war, but this act betrayed the codes of the Thieves' World that one must not ally with the government. Those who chose not to fight in the war referred to the traitors as "suka" ("bitch"), and the traitors landed at the bottom of the "hierarchy". Outcast, the "suki" separated from the others and formed their own groups and power bases by collaborating with prison officials, eventually gaining the luxury of comfortable positions. Bitterness between the groups erupted into a series of Bitch Wars from 1945 to 1953 with many killed every day. The prison officials encouraged the violence, seeing it as a way to rid the prisons of criminals.


title: Russian mafia

text: While Hitler’s invasion of Russia during WWII caused countless casualties on the battlefield, it also led to one of more violent periods in the history of Russian organized crime. In 1941, as the German army approached, Stalin desperately looked for ways to bolster the Russian army’s numbers. Turning to the seemingly endless supply of able-bodied men overflowing the gulags and prison system, Stalin promised the vor a chance to win back their freedom by defending Russia against the imminent attack. Joining the army to fight for Stalin (cooperating with the government) was a flagrant violation of the criminal code of honor, yet for many, this offer was too tempting to refuse. Thousands of prisoners signed up to defend against the Nazi threat and regain their freedom; that freedom, however, proved to be only momentary. Following the conclusion of the war in 1945, Stalin reneged on his initial promise, throwing the vor soldiers right back into the gulags that they had so desperately tried to escape. This marked the beginning of what would be known as the “Suki Wars.” Though the prison system had never been a particularly safe haven to begin with, the return to the gulags was a death sentence for the vor who had fought in the Red Army. To the vory v zakone, cooperating with the government was tantamount to treason; therefore, the thieves who had remained in prison saw the actions of the thieves-turned-soldiers as the ultimate betrayal. These “traitors,” called suki, were systematically slaughtered in the gulags as a punishment for their treachery and cowardice. The prison guards did nothing to stop the massacre, and in fact often encouraged the violence, as they viewed it was a quick and cost-effective method for thinning the criminal ranks within the prison system. It is unknown just how many suki were killed during this extermination process, but in 1953, eight million prisoners were finally released. By then, the culture of the Russian criminal underworld had been irreparably altered—no longer did a criminal need to abide by the antiquated rules of the old “Thieves’ World.”


title: Russian mafia

text: Then, in the 1980s, Mikhail Gorbachev loosened restrictions on private businesses, allowing them to grow legally, but by then, the Soviet Union was already beginning to collapse.


title: Russian mafia

text: Also during the 1970s and 1980s, the United States expanded its immigration policies, allowing Soviet Jews, with most settling in a southern Brooklyn area known as Brighton Beach (sometimes nicknamed "Little Odessa"). Here is where Russian organized crime began in the US. The earliest known case of Russian crime in the area was in the mid-1970s by the "Potato Bag Gang," a group of con artists disguised as merchants that told customers that they were selling antique gold rubles for cheap, but in fact, gave them bags of potatoes when bought in thousands. By 1983, the head of Russian organized crime in Brighton Beach was Evsei Agron.


title: Russian mafia

text: Pauol Mirzoyan was a prime target among other mobsters including rival Boris Goldberg and his organization, and in May 1985 Agron was assassinated. Boris "Biba" Nayfeld, his bodyguard, moved on to employ under Marat Balagula, who was believed to have succeeded Agron's authority. In the following year, Balagula fled the country after he was convicted in a fraud scheme of Merrill Lynch customers, and was found in Frankfurt, West Germany in 1989, where he was extradited back to the US and sentenced to eight years in prison.


title: Russian mafia

text: Balagula would later be convicted on a separate $360,000 credit card fraud in 1992. Nayfield took Balagula's place, partnering with the "Polish Al Capone", Ricardo Fanchiniin, in an import-export business and setting up a heroin business. In 1990, his former friend, Monya Elson, back from a six-year prison sentence in Israel, returned to America and set up a rival heroin business, culminating in a mafia turf war.


title: Russian mafia

text: When the USSR collapsed and a free market economy emerged, organized criminal groups began to take over Russia's economy, with many ex-KGB agents and veterans of the Afghan war offering their skills to the crime bosses. Gangster summit meetings had taken place in hotels and restaurants shortly before the Soviet's dissolution, so that top "vory v zakone" could agree on who would rule what, and set plans on how to take over the post-Communist states.


title: Russian mafia

text: In the 1990s in Russia, as well as in other post-Soviet countries, vast deposits of natural resources and businesses that the state had owned for decades were privatised. Former Soviet bureaucrats, factory directors, aggressive businessmen and criminal organizations used insider deals, bribery and simple brute force in order to grab lucrative assets. Businesses began building their own private armies of security agents, bodyguards and commercial spies. They often simply bought the people and weapons of the former Soviet state, or even those of the current Russian police. Russia's new capitalists spent millions of dollars for protection, buying armor-plated cars, bomb sensors, hidden cameras, bulletproof vests, anti-wiretapping gear, weapons, recruiting veterans of the Afghan and Chechen wars as their bodyguards. However, almost every business in Russia, from curbside vendors to huge oil and gas companies, made payments to the organized crime for protection ("krysha"). Businessmen said that they needed the "krysha" because the laws and the court system were not functioning properly in Russia. The only way for them to enforce a contract was to turn to a criminal "krysha". They also used it to intimidate competitors, enforce contracts, collect debts or take over new markets. It was also becoming increasingly common for Russian businesses to turn to the "red krysha" (the corrupt police who doubled as a paid protection racket). Contract killings were common.


title: Russian mafia

text: The discussion notes that Russian mobsters now operate in more than 50 countries around the world. Their background in a totalitarian country with widespread corruption has resulted in their development of a unique business acumen. Thirty Russian crime syndicates operate in at least 17 cities in the United States. The Red Mafiya is the most brilliant and savage Russian mob organization in the world; the Russian mob virtually controls Russia. In addition, both the Bush and the Clinton Administrations have unwittingly facilitated the Russian mob and the untrammeled corruption of Russia since the fall of the Soviet Union.


title: Russian mafia

text: In early 1993, the Russian Ministry of Internal Affairs reported there were over 5,000 organized crime groups operating in Russia. These groups had an estimated 100,000 members with a leadership of 18,000. Although Russian authorities have currently identified over 5,000 criminal groups in that country, Russian officials believe that only approximately 300 of those have some identifiable structure. 11 organized crime groups in Russia are not nearly as structured as those in the U.S., such as the LCN.


title: Russian mafia

text: It was the period of internationalization of Russian organized crime. It was agreed that Vyacheslav "Yaponchik" Ivankov would be sent to Brighton Beach in 1992, allegedly because he was killing too many people in Russia and also to take control of Russian organized crime in North America. Within a year, he built an international operation that included, but was not limited to, narcotics, money laundering, and prostitution and made ties with the American Mafia and Colombian drug cartels, eventually extending to Miami, Los Angeles, and Boston. Those who went against him were usually killed.


title: Russian mafia

text: Prior to Ivankov's arrival, Balagula's downfall left a void for America's next "vory v zakone". Monya Elson, leader of Monya's "Brigada" (a gang that similarly operated from Russia to Los Angeles to New York), was in a feud with Boris Nayfeld, with bodies dropping on both sides. Ivankov's arrival virtually ended the feud, although Elson would later challenge his power as well, and a number of attempts were made to end the former's life. Nayfield and Elson would eventually be arrested in January 1994 (released in 1998) and in Italy in 1995, respectively.


title: Russian mafia

text: According to FBI reports, the crime boss Semion Mogilevich had alliances with the Camorra, in particular with Salvatore DeFalco, a lower-echelon member of the Giuliano clan. Mogilevich and DeFalco would have held meetings in Prague in 1993.Semion Mogilevich's net worth is estimated to be 10 billion dollar.


title: Russian mafia

text: Ivankov's reign also ended in June 1995 when a $3.5 million extortion attempt on two Russian businessmen, Alexander Volkov and Vladimir Voloshin, ended in an FBI arrest that resulted in a ten-year maximum security prison sentence. Before his arrest and besides his operations in America, Ivankov regularly flew around Europe and Asia to maintain ties with his fellow mobsters (like members of the "Solntsevskaya Bratva"), as well as reinforce ties with others. This did not stop other people from denying his growing power. In one instance, Ivankov attempted to buy out Georgian boss Valeri "Globus" Glugech's drug importation business. When the latter refused the offer, he and his top associates were shot dead. A summit held in May 1994 in Vienna rewarded him with what was left of Glugech's business. Two months later, Ivankov got into another altercation with drug kingpin and head of the "Orekhovskaya" gang, Segei "Sylvester" Timofeyev, ending with the latter murdered a month later.


title: Russian mafia

text: In 1995, the Camorra cooperated with the Russian Mafia in a scheme in which the Camorra would bleach out US$1 bills and reprint them as $100s. These bills would then be transported to the Russian Mafia for distribution in 29 post-Eastern Bloc countries and former Soviet republics. In return, the Russian Mafia paid the Camorra with property (including a Russian bank) and firearms, smuggled into Eastern Europe and Italy.


title: Russian mafia

text: A report by the United Nations in 1995 placed the number of individuals involved in organized crime in Russia at 3 million, employed in about 5,700 gangs.


title: Russian mafia

text: Back in Eastern Europe in May 1995, Semion Mogilevich held a summit meeting of Russian mafia bosses in his U Holubu restaurant in Anděl, a neighborhood of Prague. The excuse to bring them together was that it was a birthday party for Victor Averin, the second-in-command of the "Solntsevskaya Bratva". However, Major Tomas Machacek of the Czech police got wind of an anonymous tip-off that claimed that the "Solntsevskaya" were planning to assassinate Mogilevich at the location (it was rumored that Mogilevich and "Solntsevskaya" leader Sergei Mikhailov had a dispute over $5 million), and the police successfully raided the meeting. 200 guests were arrested, but no charges were put against them; only key Russian mafia members were banned from the country, most of whom moved to Hungary.


title: Russian mafia

text: One person who was not there was Mogilevich himself. He claimed that "[b]y the time I arrived at U Holubu, everything was already in full swing, so I went into a neighboring hotel and sat in the bar there until about five or six in the morning." Mikhailov would later be arrested in Switzerland in October 1996 on numerous charges, including that he was the head of a powerful Russian mafia group, but was exonerated and released two years later after evidence was not enough to prove much.


title: Russian mafia

text: The global extent of Russian organized crime wasn't realized until Ludwig "Tarzan" Fainberg was arrested in January 1997, primarily because of arms dealing. In 1990, Fainberg moved from Brighton Beach to Miami and opened up a strip club called Porky's, which soon became a popular hangout for underworld criminals. Fainberg himself gained a reputation as an ambassador among international crime groups, becoming especially close to Juan Almeida, a Colombian cocaine dealer. Planning to expand his cocaine business, Fainberg acted as an intermediary between Almeida and the corrupt Russian military. He helped him get six Russian military helicopters in 1993, and in the following year, helped arrange to buy a submarine for cocaine smuggling. Unfortunately for the two of them, federal agents had been keeping a close eye on Fainberg for months. Alexander Yasevich, an associate of the Russian military contact and an undercover DEA agent, was sent to verify the illegal dealing, and in 1997, Fainberg was finally arrested in Miami. Facing the possibility of life imprisonment, the latter agreed to testify against Almeida in exchange for a shorter sentence, which ended up being 33 months.


title: Russian mafia

text: The published a website in 2000 containing Philipp Bobkov's MOST Group Security Database along with files from RUOP and other departments and special services.


title: Russian mafia

text: As the 21st century dawned, the Russian mafia remained after the death of Aslan Usoyan. New Mafia bosses sprang up, while imprisoned ones were released. Among the released were Marat Balagula and Vyacheslav Ivankov, both in 2004. The latter was extradited to Russia, but was jailed once more for his alleged murders of two Turks in a Moscow restaurant in 1992; he was cleared of all charges and released in 2005. Four years later, he was assassinated by a shot in the stomach from a sniper. Meanwhile, Monya Elson and Leonid Roytman were arrested in March 2006 for an unsuccessful murder plot against two Kyiv-based businessmen.


title: Russian mafia

text: In 2009, FBI agents in Moscow targeted two suspected Mafia leaders and two other corrupt businessmen. One of the leaders is Yevgeny Dvoskin, a criminal who had been in prison with Ivankov in 1995 and was deported in 2001 for breaking immigration regulations; the other is Konstantin "Gizya" Ginzburg, who was reportedly the current "big boss" of Russian organized crime in America before his reported assassination in 2009, it being suspected that Ivankov handed over control to him.


title: Russian mafia

text: In the same year, Semion Mogilevich was placed on the FBI Ten Most Wanted Fugitives list for his involvement in a complex multimillion-dollar scheme that defrauded investors in the stock of his company YBM Magnex International, swindling them out of $150 million. He was indicted in 2003 and arrested in 2008 in Russia on tax fraud charges, but because the US does not have an extradition treaty with Russia, he was released on bail. Monya Elson said, in 1998, that Mogilevich is the most powerful mobster in the world.


title: Russian mafia

text: Around the world, Russian mafia groups have popped up as dominating particular areas. Russian organized crime has a rather large stronghold in the city of Atlanta where members are distinguished by their tattoos. Russian organized crime was reported to have a stronger grip in the French Riviera region and Spain in 2010; and Russia was branded as a virtual "mafia state" according to the WikiLeaks cables.


title: Russian mafia

text: In 2009, Russian mafia groups had been said to reach over 50 countries and, in 2010, had up to 300,000 members. According to recordings released in 2015, Alexander Litvinenko, shortly before he was assassinated, claimed that Semion Mogilevich has had a "good relationship" with Vladimir Putin since the 1990s.


title: Russian mafia

text: On 7 June 2017, 33 Russian mafia affiliates and members were arrested and charged by the FBI, U.S. Customs and Border Protection and NYPD for extortion, racketeering, illegal gambling, firearm offenses, narcotics trafficking, wire fraud, credit card fraud, identity theft, fraud on casino slot machines using electronic hacking devices; based in Atlantic City and Philadelphia, murder-for-hire conspiracy and cigarette trafficking. They were also accused of operating secret and underground gambling dens based in Brighton Beach, Brooklyn, and using violence to those who owed gambling debts, establishing nightclubs to sell drugs, plotting to force women associates to rob male strangers by seducing and drugging them with chloroform, and trafficking over 10,000 pounds of stolen chocolate confectionery; the chocolate was stolen from shipment containers. It is believed that 27 of the arrested are connected to the Russian mafia "Shulaya clan" which are largely based in New York. According to the prosecution, the "Shulaya" also has operations in New Jersey, Pennsylvania, Florida and Nevada. According to law enforcement and the prosecution, this is one of the first federal arrests against a Russian mafia boss and his underboss or co-leader.


title: Russian mafia

text: On 26 September 2017, as part of a 4-year investigation, 100 Spanish Civil Guard officers carried out 18 searches in different areas of Malaga, Spain related to Russian mafia large scale money laundering. The raids resulted in the arrests of 11 members and associates of the "Solntsevskaya" and "Izmailovskaya" clans. Money, firearms and 23 high-end vehicles were also seized. The owner of Marbella FC, Alexander Grinberg, and manager of AFK Sistema, a Spanish football club in Malaga, were among those arrested.


title: Russian mafia

text: On 19 February 2018, 18 defendants were accused of laundering over $62 million through real estate, including with the help of Vladislav Reznik, former chairman of Rosgosstrakh, one of Russia's largest insurance companies. The accused stood trial in Spain. The Tambov and Malyshev Russian mafia organisations were involved.


title: Russian mafia

text: Note that these positions are not always official titles, but rather are understood names for roles that an individual performs.


title: Russian mafia

text: In the Russian Mafia, "Vor" (plural: Vory) (literally, "Thief") is an honorary title analogous to a made man in the Italian-American and Sicilian mafia. The honor of becoming a Vor is given only when the recruit shows considerable leadership skills, personal ability, intellect, and charisma. A Pakhan or another high-ranking member of an organization can decide if the recruit will receive such title. When you become a member of the Vor-world you have to accept the code of the Vor v Zakone ("Thief in law").


title: Russian mafia

text: Although Russian criminal groups vary in their structure, there have been attempts to devise a model of how they work. One such model (possibly outdated by now, as it is based on the old style of Soviet criminal enterprises) works out like this:


title: Concrete

text: Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $600 billion in revenue by 2025. This widespread use results in a number of environmental impacts. Most notably, the production process for cement produces large volumes of greenhouse gas emissions, leading to net 8% of global emissions. Other environmental concerns include widespread illegal sand mining, impacts on the surrounding environment such as increased surface runoff or urban heat island effect, and potential public health implications from toxic ingredients. Significant research and development is being done to try to reduce the emissions or make concrete a source of carbon sequestration, and increase recycled and secondary raw materials content into the mix to achieve a circular economy. Concrete is expected to be a key material for structures resilient to climate disasters, as well as a solution to mitigate the pollution of other industries, capturing wastes such as coal fly ash or bauxite tailings and residue.


title: Concrete

text: When aggregate is mixed with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts with the water through a process called concrete hydration that hardens over several hours to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. This time allows concrete to not only be cast in forms but also to have a variety of tooled processes preformed. The hydration process is exothermic, which means ambient temperature plays a significant role in how long it takes concrete to set. Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix, delay or accelerate the curing time, or otherwise change the finished material. Most concrete is poured with reinforcing materials (such as rebar) embedded to provide tensile strength, yielding reinforced concrete.


title: Concrete

text: In the past, lime based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements, (water resistant) such as a calcium aluminate cement or with Portland cement to form Portland cement concrete (named for its visual resemblance to Portland stone). Many other non-cementitious types of concrete exist with other methods of binding aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces, and polymer concretes that use polymers as a binder. Concrete is distinct from mortar. Whereas concrete is itself a building material, mortar is a bonding agent that typically holds bricks, tiles and other masonry units together.


title: Concrete

text: The word concrete comes from the Latin word ""concretus"" (meaning compact or condensed), the perfect passive participle of ""concrescere"", from ""con"-" (together) and ""crescere"" (to grow).


title: Concrete

text: Mayan concrete at the ruins of Uxmal (850-925 A.D.) is referenced in "Incidents of Travel in the Yucatán" by John L. Stephens. "The roof is flat and had been covered with cement". "The floors were cement, in some places hard, but, by long exposure, broken, and now crumbling under the feet." "But throughout the wall was solid, and consisting of large stones imbedded in mortar, almost as hard as rock."


title: Concrete

text: Small-scale production of concrete-like materials was pioneered by the Nabatean traders who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan from the 4th century BC. They discovered the advantages of hydraulic lime, with some self-cementing properties, by 700 BC. They built kilns to supply mortar for the construction of rubble masonry houses, concrete floors, and underground waterproof cisterns. They kept the cisterns secret as these enabled the Nabataeans to thrive in the desert. Some of these structures survive to this day.


title: Concrete

text: In the Ancient Egyptian and later Roman eras, builders discovered that adding volcanic ash to the mix allowed it to set underwater.


title: Concrete

text: Concrete floors were found in the royal palace of Tiryns, Greece, which dates roughly to 1400–1200 BC. Lime mortars were used in Greece, Crete, and Cyprus in 800 BC. The Assyrian Jerwan Aqueduct (688 BC) made use of waterproof concrete. Concrete was used for construction in many ancient structures.


title: Concrete

text: The Romans used concrete extensively from 300 BC to 476 AD. During the Roman Empire, Roman concrete (or "opus caementicium") was made from quicklime, pozzolana and an aggregate of pumice. Its widespread use in many Roman structures, a key event in the history of architecture termed the Roman architectural revolution, freed Roman construction from the restrictions of stone and brick materials. It enabled revolutionary new designs in terms of both structural complexity and dimension. The Colosseum in Rome was built largely of concrete, and the Pantheon has the world's largest unreinforced concrete dome.


title: Concrete

text: Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick.


title: Concrete

text: Modern tests show that "opus caementicium" had as much compressive strength as modern Portland-cement concrete (ca. ). However, due to the absence of reinforcement, its tensile strength was far lower than modern reinforced concrete, and its mode of application also differed:


title: Concrete

text: Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.


title: Concrete

text: The long-term durability of Roman concrete structures has been found to be due to its use of pyroclastic (volcanic) rock and ash, whereby the crystallization of strätlingite (a specific and complex calcium aluminosilicate hydrate) and the coalescence of this and similar calcium–aluminum-silicate–hydrate cementing binders helped give the concrete a greater degree of fracture resistance even in seismically active environments. Roman concrete is significantly more resistant to erosion by seawater than modern concrete; it used pyroclastic materials which react with seawater to form Al-tobermorite crystals over time.


title: Concrete

text: The widespread use of concrete in many Roman structures ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon.


title: Concrete

text: After the Roman Empire collapsed, use of concrete became rare until the technology was redeveloped in the mid-18th century. Worldwide, concrete has overtaken steel in tonnage of material used.


title: Concrete

text: After the Roman Empire, the use of burned lime and pozzolana was greatly reduced. Low kiln temperatures in the burning of lime, lack of pozzolana, and poor mixing all contributed to a decline in the quality of concrete and mortar. From the 11th century, the increased use of stone in church and castle construction led to an increased demand for mortar. Quality began to improve in the 12th century through better grinding and sieving. Medieval lime mortars and concretes were non-hydraulic and were used for binding masonry, "hearting" (binding rubble masonry cores) and foundations. Bartholomaeus Anglicus in his "De proprietatibus rerum" (1240) describes the making of mortar. In an English translation from 1397, it reads "lyme ... is a stone brent; by medlynge thereof with sonde and water sement is made". From the 14th century, the quality of mortar was again excellent, but only from the 17th century was pozzolana commonly added.


title: Concrete

text: Perhaps the greatest step forward in the modern use of concrete was Smeaton's Tower, built by British engineer John Smeaton in Devon, England, between 1756 and 1759. This third Eddystone Lighthouse pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate.


title: Concrete

text: A method for producing Portland cement was developed in England and patented by Joseph Aspdin in 1824. Aspdin chose the name for its similarity to Portland stone, which was quarried on the Isle of Portland in Dorset, England. His son William continued developments into the 1840s, earning him recognition for the development of "modern" Portland cement.


title: Concrete

text: Reinforced concrete was invented in 1849 by Joseph Monier. and the first reinforced concrete house was built by François Coignet in 1853.


title: Concrete

text: Concrete is an artificial composite material, comprising a matrix of cementitious binder (typically Portland cement paste or asphalt) and a dispersed phase or "filler" of aggregate (typically a rocky material, loose stones, and sand). The binder "glues" the filler together to form a synthetic conglomerate. Many types of concrete are available, determined by the formulations of binders and the types of aggregate used to suit the application of the engineered material. These variables determine strength and density, as well as chemical and thermal resistance of the finished product.


title: Concrete

text: Aggregates consist of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestone, or granite, along with finer materials such as sand.


title: Concrete

text: Cement paste, most commonly made of Portland cement, is the most prevalent kind of concrete binder. For cementitious binders, water is mixed with the dry cement powder and aggregate, which produces a semi-liquid slurry (paste) that can be shaped, typically by pouring it into a form. The concrete solidifies and hardens through a chemical process called hydration. The water reacts with the cement, which bonds the other components together, creating a robust, stone-like material. Other cementitious materials, such as fly ash and slag cement, are sometimes added—either pre-blended with the cement or directly as a concrete component—and become a part of the binder for the aggregate. Fly ash and slag can enhance some properties of concrete such as fresh properties and durability. Alternatively, other materials can also be used as a concrete binder: the most prevalent substitute is asphalt, which is used as the binder in asphalt concrete.


title: Concrete

text: Admixtures are added to modify the cure rate or properties of the material. Mineral admixtures use recycled materials as concrete ingredients. Conspicuous materials include fly ash, a by-product of coal-fired power plants; ground granulated blast furnace slag, a by-product of steelmaking; and silica fume, a by-product of industrial electric arc furnaces.


title: Concrete

text: Structures employing Portland cement concrete usually include steel reinforcement because this type of concrete can be formulated with high compressive strength, but always has lower tensile strength. Therefore, it is usually reinforced with materials that are strong in tension, typically steel rebar.


title: Concrete

text: The "mix design" depends on the type of structure being built, how the concrete is mixed and delivered, and how it is placed to form the structure.


title: Concrete

text: Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar, and many plasters. British masonry worker Joseph Aspdin patented Portland cement in 1824. It was named because of the similarity of its color to Portland limestone, quarried from the English Isle of Portland and used extensively in London architecture. It consists of a mixture of calcium silicates (alite, belite), aluminates and ferrites—compounds which combine calcium, silicon, aluminum and iron in forms which will react with water. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay or shale (a source of silicon, aluminum and iron) and grinding this product (called "clinker") with a source of sulfate (most commonly gypsum).


title: Concrete

text: In modern cement kilns, many advanced features are used to lower the fuel consumption per ton of clinker produced. Cement kilns are extremely large, complex, and inherently dusty industrial installations, and have emissions which must be controlled. Of the various ingredients used to produce a given quantity of concrete, the cement is the most energetically expensive. Even complex and efficient kilns require 3.3 to 3.6 gigajoules of energy to produce a ton of clinker and then grind it into cement. Many kilns can be fueled with difficult-to-dispose-of wastes, the most common being used tires. The extremely high temperatures and long periods of time at those temperatures allows cement kilns to efficiently and completely burn even difficult-to-use fuels.


title: Concrete

text: Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and makes it flow more freely.


title: Concrete

text: As stated by Abrams' law, a lower water-to-cement ratio yields a stronger, more durable concrete, whereas more water gives a freer-flowing concrete with a higher slump. Impure water used to make concrete can cause problems when setting or in causing premature failure of the structure.


title: Concrete

text: Portland cement consists of five major compounds of calcium silicates and alumninates ranging from 5 to 50% in weight, which all undergo hydration to contribute to final material's strength. Thus, the hydration of cement involves many reactions, often occurring at the same time. As the reactions proceed, the products of the cement hydration process gradually bond together the individual sand and gravel particles and other components of the concrete to form a solid mass.


title: Concrete

text: Due to the nature of the chemical bonds created in these reactions and the final characteristics of the particles formed, the process of cement hydration is considered irreversible, which makes methods of cement recycling prohibitive.


title: Concrete

text: Fine and coarse aggregates make up the bulk of a concrete mixture. Sand, natural gravel, and crushed stone are used mainly for this purpose. Recycled aggregates (from construction, demolition, and excavation waste) are increasingly used as partial replacements for natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted.


title: Concrete

text: The size distribution of the aggregate determines how much binder is required. Aggregate with a very even size distribution has the biggest gaps whereas adding aggregate with smaller particles tends to fill these gaps. The binder must fill the gaps between the aggregate as well as paste the surfaces of the aggregate together, and is typically the most expensive component. Thus, variation in sizes of the aggregate reduces the cost of concrete. The aggregate is nearly always stronger than the binder, so its use does not negatively affect the strength of the concrete.


title: Concrete

text: Redistribution of aggregates after compaction often creates non-homogeneity due to the influence of vibration. This can lead to strength gradients.


title: Concrete

text: Decorative stones such as quartzite, small river stones or crushed glass are sometimes added to the surface of concrete for a decorative "exposed aggregate" finish, popular among landscape designers.


title: Concrete

text: Admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. Admixtures are defined as additions "made as the concrete mix is being prepared". The most common admixtures are retarders and accelerators. In normal use, admixture dosages are less than 5% by mass of cement and are added to the concrete at the time of batching/mixing. (See below.) The common types of admixtures are as follows:


title: Concrete

text: Inorganic materials that have pozzolanic or latent hydraulic properties, these very fine-grained materials are added to the concrete mix to improve the properties of concrete (mineral admixtures), or as a replacement for Portland cement (blended cements). Products which incorporate limestone, fly ash, blast furnace slag, and other useful materials with pozzolanic properties into the mix, are being tested and used. These developments are ever growing in relevance to minimize the impacts caused by cement use, notorious for being one of the largest producers (at about 5 to 10%) of global greenhouse gas emissions. The use of alternative materials also is capable of lowering costs, improving concrete properties, and recycling wastes, the latest being relevant for circular economy aspects of the construction industry, whose demand is ever growing with greater impacts on raw material extraction, waste generation and landfill practices.


title: Concrete

text: Concrete production is the process of mixing together the various ingredients—water, aggregate, cement, and any additives—to produce concrete. Concrete production is time-sensitive. Once the ingredients are mixed, workers must put the concrete in place before it hardens. In modern usage, most concrete production takes place in a large type of industrial facility called a concrete plant, or often a batch plant.


title: Concrete

text: In general usage, concrete plants come in two main types, ready mix plants and central mix plants. A ready-mix plant mixes all the ingredients except water, while a central mix plant mixes all the ingredients including water. A central-mix plant offers more accurate control of the concrete quality through better measurements of the amount of water added, but must be placed closer to the work site where the concrete will be used, since hydration begins at the plant.


title: Concrete

text: A concrete plant consists of large storage hoppers for various reactive ingredients like cement, storage for bulk ingredients like aggregate and water, mechanisms for the addition of various additives and amendments, machinery to accurately weigh, move, and mix some or all of those ingredients, and facilities to dispense the mixed concrete, often to a concrete mixer truck.


title: Concrete

text: Modern concrete is usually prepared as a viscous fluid, so that it may be poured into forms, which are containers erected in the field to give the concrete its desired shape. Concrete formwork can be prepared in several ways, such as slip forming and steel plate construction. Alternatively, concrete can be mixed into dryer, non-fluid forms and used in factory settings to manufacture precast concrete products.


title: Concrete

text: A wide variety of equipment is used for processing concrete, from hand tools to heavy industrial machinery. Whichever equipment builders use, however, the objective is to produce the desired building material; ingredients must be properly mixed, placed, shaped, and retained within time constraints. Any interruption in pouring the concrete can cause the initially placed material to begin to set before the next batch is added on top. This creates a horizontal plane of weakness called a "cold joint" between the two batches. Once the mix is where it should be, the curing process must be controlled to ensure that the concrete attains the desired attributes. During concrete preparation, various technical details may affect the quality and nature of the product.


title: Concrete

text: "Design mix" ratios are decided by an engineer after analyzing the properties of the specific ingredients being used. Instead of using a 'nominal mix' of 1 part cement, 2 parts sand, and 4 parts aggregate (the second example from above), a civil engineer will custom-design a concrete mix to exactly meet the requirements of the site and conditions, setting material ratios and often designing an admixture package to fine-tune the properties or increase the performance envelope of the mix. Design-mix concrete can have very broad specifications that cannot be met with more basic nominal mixes, but the involvement of the engineer often increases the cost of the concrete mix.


title: Concrete

text: Nominal mix ratios are given in volume of formula_1. Nominal mixes are a simple, fast way of getting a basic idea of the properties of the finished concrete without having to perform testing in advance.


title: Concrete

text: Various governing bodies (such as British Standards) define nominal mix ratios into a number of grades, usually ranging from lower compressive strength to higher compressive strength. The grades usually indicate the 28-day cube strength.


title: Concrete

text: Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (pouring, pumping, spreading, tamping, vibration) and without reducing the concrete's quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration) and can be modified by adding chemical admixtures, like superplasticizer. Raising the water content or adding chemical admixtures increases concrete workability. Excessive water leads to increased bleeding or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. Changes in gradation can also affect workability of the concrete, although a wide range of gradation can be used for various applications. An undesirable gradation can mean using a large aggregate that is too large for the size of the formwork, or which has too few smaller aggregate grades to serve to fill the gaps between the larger grades, or using too little or too much sand for the same reason, or using too little water, or too much cement, or even using jagged crushed stone instead of smoother round aggregate such as pebbles. Any combination of these factors and others may result in a mix which is too harsh, i.e., which does not flow or spread out smoothly, is difficult to get into the formwork, and which is difficult to surface finish.


title: Concrete

text: Workability can be measured by the concrete slump test, a simple measure of the plasticity of a fresh batch of concrete following the ASTM C 143 or EN 12350-2 test standards. Slump is normally measured by filling an "Abrams cone" with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive surface. It is then filled in three layers of equal volume, with each layer being tamped with a steel rod to consolidate the layer. When the cone is carefully lifted off, the enclosed material slumps a certain amount, owing to gravity. A relatively dry sample slumps very little, having a slump value of one or two inches (25 or 50 mm) out of . A relatively wet concrete sample may slump as much as eight inches. Workability can also be measured by the flow table test.


title: Concrete

text: Slump can be increased by addition of chemical admixtures such as plasticizer or superplasticizer without changing the water-cement ratio. Some other admixtures, especially air-entraining admixture, can increase the slump of a mix.


title: Concrete

text: High-flow concrete, like self-consolidating concrete, is tested by other flow-measuring methods. One of these methods includes placing the cone on the narrow end and observing how the mix flows through the cone while it is gradually lifted.


title: Concrete

text: Concrete must be kept moist during curing in order to achieve optimal strength and durability. During curing hydration occurs, allowing calcium-silicate hydrate (C-S-H) to form. Over 90% of a mix's final strength is typically reached within four weeks, with the remaining 10% achieved over years or even decades. The conversion of calcium hydroxide in the concrete into calcium carbonate from absorption of CO over several decades further strengthens the concrete and makes it more resistant to damage. This carbonation reaction, however, lowers the pH of the cement pore solution and can corrode the reinforcement bars.


title: Concrete

text: Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained sufficient strength, resulting in greater shrinkage cracking. The early strength of the concrete can be increased if it is kept damp during the curing process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking. The strength of concrete changes (increases) for up to three years. It depends on cross-section dimension of elements and conditions of structure exploitation. Addition of short-cut polymer fibers can improve (reduce) shrinkage-induced stresses during curing and increase early and ultimate compression strength.


title: Concrete

text: Properly curing concrete leads to increased strength and lower permeability and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing or overheating due to the exothermic setting of cement. Improper curing can cause scaling, reduced strength, poor abrasion resistance and cracking.


title: Concrete

text: During the curing period, concrete is ideally maintained at controlled temperature and humidity. To ensure full hydration during curing, concrete slabs are often sprayed with "curing compounds" that create a water-retaining film over the concrete. Typical films are made of wax or related hydrophobic compounds. After the concrete is sufficiently cured, the film is allowed to abrade from the concrete through normal use.


title: Concrete

text: Traditional conditions for curing involve spraying or ponding the concrete surface with water. The adjacent picture shows one of many ways to achieve this, ponding—submerging setting concrete in water and wrapping in plastic to prevent dehydration. Additional common curing methods include wet burlap and plastic sheeting covering the fresh concrete.


title: Concrete

text: For higher-strength applications, accelerated curing techniques may be applied to the concrete. A common technique involves heating the poured concrete with steam, which serves to both keep it damp and raise the temperature so that the hydration process proceeds more quickly and more thoroughly.


title: Concrete

text: "Asphalt concrete" (commonly called "asphalt", "blacktop", or "pavement" in North America, and "tarmac", "bitumen macadam", or "rolled asphalt" in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parking lots, airports, as well as the core of embankment dams. Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. It consists of mineral aggregate bound together with asphalt, laid in layers, and compacted. The process was refined and enhanced by Belgian inventor and U.S. immigrant Edward De Smedt.


title: Concrete

text: The terms "asphalt" (or "asphaltic") "concrete", "bituminous asphalt concrete", and "bituminous mixture" are typically used only in engineering and construction documents, which define concrete as any composite material composed of mineral aggregate adhered with a binder. The abbreviation, "AC", is sometimes used for "asphalt concrete" but can also denote "asphalt content" or "asphalt cement", referring to the liquid asphalt portion of the composite material.


title: Concrete

text: Graphene enhanced concretes are standard designs of concrete mixes, except that during the cement-mixing or production process, a small amount of chemically engineered graphene is added. These enhanced graphene concretes are designed around the concrete application.


title: Concrete

text: Bacteria such as "Bacillus pasteurii", "Bacillus pseudofirmus", "Bacillus cohnii", "Sporosarcina pasteuri", and "Arthrobacter crystallopoietes" increase the compression strength of concrete through their biomass. However some forms of bacteria can also be concrete-destroying. Bacillus sp. CT-5. can reduce corrosion of reinforcement in reinforced concrete by up to four times. "Sporosarcina pasteurii" reduces water and chloride permeability. "B. pasteurii" increases resistance to acid. "Bacillus pasteurii" and "B. sphaericuscan" induce calcium carbonate precipitation in the surface of cracks, adding compression strength.


title: Concrete

text: Nanoconcrete (also spelled "nano concrete"' or "nano-concrete") is a class of materials that contains Portland cement particles that are no greater than 100 μm and particles of silica no greater than 500 μm, which fill voids that would otherwise occur in normal concrete, thereby substantially increasing the material's strength. It is widely used in foot and highway bridges where high flexural and compressive strength are indicated.


title: Concrete

text: Pervious concrete is a mix of specially graded coarse aggregate, cement, water, and little-to-no fine aggregates. This concrete is also known as "no-fines" or porous concrete. Mixing the ingredients in a carefully controlled process creates a paste that coats and bonds the aggregate particles. The hardened concrete contains interconnected air voids totaling approximately 15 to 25 percent. Water runs through the voids in the pavement to the soil underneath. Air entrainment admixtures are often used in freeze-thaw climates to minimize the possibility of frost damage. Pervious concrete also permits rainwater to filter through roads and parking lots, to recharge aquifers, instead of contributing to runoff and flooding.


title: Concrete

text: Polymer concretes are mixtures of aggregate and any of various polymers and may be reinforced. The cement is costlier than lime-based cements, but polymer concretes nevertheless have advantages; they have significant tensile strength even without reinforcement, and they are largely impervious to water. Polymer concretes are frequently used for the repair and construction of other applications, such as drains.


title: Concrete

text: Volcanic concrete substitutes volcanic rock for the limestone that is burned to form clinker. It consumes a similar amount of energy, but does not directly emit carbon as a byproduct. Volcanic rock/ash are used as supplementary cementitious materials in concrete to improve the resistance to sulfate, chloride and alkali silica reaction due to pore refinement. Also, they are generally cost effective in comparison to other aggregates, good for semi and light weight concretes, and good for thermal and acoustic insulation.


title: Concrete

text: Pyroclastic materials, such as pumice, scoria, and ashes are formed from cooling magma during explosive volcanic eruptions. They are used as supplementary cementitious materials (SCM) or as aggregates for cements and concretes. They have been extensively used since ancient times to produce materials for building applications. For example, pumice and other volcanic glasses were added as a natural pozzolanic material for mortars and plasters during the construction of the Villa San Marco in the Roman period (89 BC – 79 AD), which remain one of the best-preserved otium villae of the Bay of Naples in Italy.


title: Concrete

text: Waste light is form of polymer modified concrete. The specific polymer admixture allows the replacement of all the traditional aggregates (gravel, sand, stone) by any mixture of solid waste materials in the grain size of 3–10 mm to form a low-compressive-strength (3–20 N/mm) product for road and building construction. One cubic meter of waste light concrete contains 1.1–1.3 m of shredded waste and no other aggregates.


title: Concrete

text: Sulfur concrete is a special concrete that uses sulfur as a binder and does not require cement or water.


title: Concrete

text: Concrete has relatively high compressive strength, but much lower tensile strength. Therefore, it is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion and shrinks as it matures. All concrete structures crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.


title: Concrete

text: Tests can be performed to ensure that the properties of concrete correspond to specifications for the application.


title: Concrete

text: The ingredients affect the strengths of the material. Concrete strength values are usually specified as the lower-bound compressive strength of either a cylindrical or cubic specimen as determined by standard test procedures.


title: Concrete

text: The strengths of concrete is dictated by its function. Very low-strength— or less—concrete may be used when the concrete must be lightweight. Lightweight concrete is often achieved by adding air, foams, or lightweight aggregates, with the side effect that the strength is reduced. For most routine uses, concrete is often used. concrete is readily commercially available as a more durable, although more expensive, option. Higher-strength concrete is often used for larger civil projects. Strengths above are often used for specific building elements. For example, the lower floor columns of high-rise concrete buildings may use concrete of or more, to keep the size of the columns small. Bridges may use long beams of high-strength concrete to lower the number of spans required. Occasionally, other structural needs may require high-strength concrete. If a structure must be very rigid, concrete of very high strength may be specified, even much stronger than is required to bear the service loads. Strengths as high as have been used commercially for these reasons.


title: Concrete

text: Energy requirements for transportation of concrete are low because it is produced locally from local resources, typically manufactured within 100 kilometers of the job site. Similarly, relatively little energy is used in producing and combining the raw materials (although large amounts of CO are produced by the chemical reactions in cement manufacture). The overall embodied energy of concrete at roughly 1 to 1.5 megajoules per kilogram is therefore lower than for most structural and construction materials.


title: Concrete

text: Once in place, concrete offers great energy efficiency over the lifetime of a building. Concrete walls leak air far less than those made of wood frames. Air leakage accounts for a large percentage of energy loss from a home. The thermal mass properties of concrete increase the efficiency of both residential and commercial buildings. By storing and releasing the energy needed for heating or cooling, concrete's thermal mass delivers year-round benefits by reducing temperature swings inside and minimizing heating and cooling costs. While insulation reduces energy loss through the building envelope, thermal mass uses walls to store and release energy. Modern concrete wall systems use both external insulation and thermal mass to create an energy-efficient building. Insulating concrete forms (ICFs) are hollow blocks or panels made of either insulating foam or rastra that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.


title: Concrete

text: Concrete buildings are more resistant to fire than those constructed using steel frames, since concrete has lower heat conductivity than steel and can thus last longer under the same fire conditions. Concrete is sometimes used as a fire protection for steel frames, for the same effect as above. Concrete as a fire shield, for example Fondu fyre, can also be used in extreme environments like a missile launch pad.


title: Concrete

text: Options for non-combustible construction include floors, ceilings and roofs made of cast-in-place and hollow-core precast concrete. For walls, concrete masonry technology and Insulating Concrete Forms (ICFs) are additional options. ICFs are hollow blocks or panels made of fireproof insulating foam that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.


title: Concrete

text: Concrete also provides good resistance against externally applied forces such as high winds, hurricanes, and tornadoes owing to its lateral stiffness, which results in minimal horizontal movement. However, this stiffness can work against certain types of concrete structures, particularly where a relatively higher flexing structure is required to resist more extreme forces.


title: Concrete

text: As discussed above, concrete is very strong in compression, but weak in tension. Larger earthquakes can generate very large shear loads on structures. These shear loads subject the structure to both tensile and compressional loads. Concrete structures without reinforcement, like other unreinforced masonry structures, can fail during severe earthquake shaking. Unreinforced masonry structures constitute one of the largest earthquake risks globally. These risks can be reduced through seismic retrofitting of at-risk buildings, (e.g. school buildings in Istanbul, Turkey).


title: Concrete

text: Concrete is one of the most durable building materials. It provides superior fire resistance compared with wooden construction and gains strength over time. Structures made of concrete can have a long service life. Concrete is used more than any other artificial material in the world. As of 2006, about 7.5 billion cubic meters of concrete are made each year, more than one cubic meter for every person on Earth.


title: Concrete

text: The use of reinforcement, in the form of iron was introduced in the 1850s by French industrialist François Coignet, and it was not until the 1880s that German civil engineer G. A. Wayss used steel as reinforcement. Concrete is a relatively brittle material that is strong under compression but less in tension. Plain, unreinforced concrete is unsuitable for many structures as it is relatively poor at withstanding stresses induced by vibrations, wind loading, and so on. Hence, to increase its overall strength, steel rods, wires, mesh or cables can be embedded in concrete before it is set. This reinforcement, often known as rebar, resists tensile forces.


title: Concrete

text: Reinforced concrete (RC) is a versatile composite and one of the most widely used materials in modern construction. It is made up of different constituent materials with very different properties that complement each other. In the case of reinforced concrete, the component materials are almost always concrete and steel. These two materials form a strong bond together and are able to resist a variety of applied forces, effectively acting as a single structural element.


title: Concrete

text: Reinforced concrete can be precast or cast-in-place (in situ) concrete, and is used in a wide range of applications such as; slab, wall, beam, column, foundation, and frame construction. Reinforcement is generally placed in areas of the concrete that are likely to be subject to tension, such as the lower portion of beams. Usually, there is a minimum of 50 mm cover, both above and below the steel reinforcement, to resist spalling and corrosion which can lead to structural instability. Other types of non-steel reinforcement, such as Fibre-reinforced concretes are used for specialized applications, predominately as a means of controlling cracking.


title: Concrete

text: Precast concrete is concrete which is cast in one place for use elsewhere and is a mobile material. The largest part of precast production is carried out in the works of specialist suppliers, although in some instances, due to economic and geographical factors, scale of product or difficulty of access, the elements are cast on or adjacent to the construction site. Precasting offers considerable advantages because it is carried out in a controlled environment, protected from the elements, but the downside of this is the contribution to greenhouse gas emission from transportation to the construction site.


title: Concrete

text: Due to cement's exothermic chemical reaction while setting up, large concrete structures such as dams, navigation locks, large mat foundations, and large breakwaters generate excessive heat during hydration and associated expansion. To mitigate these effects, "post-cooling" is commonly applied during construction. An early example at Hoover Dam used a network of pipes between vertical concrete placements to circulate cooling water during the curing process to avoid damaging overheating. Similar systems are still used; depending on volume of the pour, the concrete mix used, and ambient air temperature, the cooling process may last for many months after the concrete is placed. Various methods also are used to pre-cool the concrete mix in mass concrete structures.


title: Concrete

text: Another approach to mass concrete structures that minimizes cement's thermal by-product is the use of roller-compacted concrete, which uses a dry mix which has a much lower cooling requirement than conventional wet placement. It is deposited in thick layers as a semi-dry material then roller compacted into a dense, strong mass.


title: Concrete

text: Raw concrete surfaces tend to be porous and have a relatively uninteresting appearance. Many finishes can be applied to improve the appearance and preserve the surface against staining, water penetration, and freezing.


title: Concrete

text: Examples of improved appearance include stamped concrete where the wet concrete has a pattern impressed on the surface, to give a paved, cobbled or brick-like effect, and may be accompanied with coloration. Another popular effect for flooring and table tops is polished concrete where the concrete is polished optically flat with diamond abrasives and sealed with polymers or other sealants.


title: Concrete

text: Other finishes can be achieved with chiseling, or more conventional techniques such as painting or covering it with other materials.


title: Concrete

text: The proper treatment of the surface of concrete, and therefore its characteristics, is an important stage in the construction and renovation of architectural structures.


title: Concrete

text: Prestressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose tensile stresses experienced in use. This can greatly reduce the weight of beams or slabs, by


title: Concrete

text: better distributing the stresses in the structure to make optimal use of the reinforcement. For example, a horizontal beam tends to sag. Prestressed reinforcement along the bottom of the beam counteracts this.


title: Concrete

text: In pre-tensioned concrete, the prestressing is achieved by using steel or polymer tendons or bars that are subjected to a tensile force prior to casting, or for post-tensioned concrete, after casting.


title: Concrete

text: More than of highways in the United States are paved with this material. Reinforced concrete, prestressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days. For more information see Brutalist architecture.


title: Concrete

text: Extreme weather conditions (extreme heat or cold; windy conditions, and humidity variations) can significantly alter the quality of concrete. Many precautions are observed in cold weather placement. Low temperatures significantly slow the chemical reactions involved in hydration of cement, thus affecting the strength development. Preventing freezing is the most important precaution, as formation of ice crystals can cause damage to the crystalline structure of the hydrated cement paste. If the surface of the concrete pour is insulated from the outside temperatures, the heat of hydration will prevent freezing.


title: Concrete

text: In Canada, where temperatures tend to be much lower during the cold season, the following criteria are used by CSA A23.1:


title: Concrete

text: The minimum strength before exposing concrete to extreme cold is . CSA A 23.1 specified a compressive strength of 7.0 MPa to be considered safe for exposure to freezing.


title: Concrete

text: Concrete may be placed and cured underwater. Care must be taken in the placement method to prevent washing out the cement. Underwater placement methods include the tremie, pumping, skip placement, manual placement using toggle bags, and bagwork.


title: Concrete

text: Grouted aggregate is an alternative method of forming a concrete mass underwater, where the forms are filled with coarse aggregate and the voids then completely filled with pumped grout.


title: Concrete

text: Concrete roads are more fuel efficient to drive on, more reflective and last significantly longer than other paving surfaces, yet have a much smaller market share than other paving solutions. Modern-paving methods and design practices have changed the economics of concrete paving, so that a well-designed and placed concrete pavement will be less expensive on initial costs and significantly less expensive over the life cycle. Another major benefit is that pervious concrete can be used, which eliminates the need to place storm drains near the road, and reducing the need for slightly sloped roadway to help rainwater to run off. No longer requiring discarding rainwater through use of drains also means that less electricity is needed (more pumping is otherwise needed in the water-distribution system), and no rainwater gets polluted as it no longer mixes with polluted water. Rather, it is immediately absorbed by the ground.


title: Concrete

text: The manufacture and use of concrete produce a wide range of environmental, economic and social impacts.


title: Concrete

text: A major component of concrete is cement, a fine, soft, powdery-type substance, used mainly to bind fine sand and coarse aggregates together in concrete. Although a variety of cement types exist, the most common is “Portland cement”, which is produced by mixing clinker with smaller quantities of other additives such as gypsum and ground limestone. The production of clinker, the main constituent of cement, is responsible for the bulk of the sector's greenhouse gas emissions, including both energy intensity and process emissions.


title: Concrete

text: The cement industry is one of the three primary producers of carbon dioxide, a major greenhouse gas – the other two being energy production and transportation industries. On average, every tonne of cement produced releases one tonne of CO into the atmosphere. Pioneer cement manufacturers have claimed to reach lower carbon intensities, with 590 kg of COeq per tonne of cement produced. The emissions are due to combustion and calcination processes, which roughly account for 40% and 60% of the greenhouse gases, respectively. Considering that cement is only a fraction of the constituents of concrete, it is estimated that a tonne of concrete is responsible for emitting about 100–200 kg of CO. Every year more than 10 billion tonnes of concrete are used worldwide. In the coming years, large quantities of concrete will continue to be used, and the mitigation of CO emissions from the sector will be even more critical.