Abstract:
A cementitious, convex structural block for forming parabolic walls is disclosed. The block utilizes a key and the keyway to facilitate placement and to add strength to the wall. The parabolic shape of the wall increases its compressive strength and when used underground as a seal or stopping in mining applications channels force from blast waves and dammed water into the mine shaft ribs. When constructed from a geopolymer, the block is lighter and has a smaller carbon footprint than cement.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application relates to U.S. Provisional Patent Application 61/600,584 filed Feb. 18, 2012 and U.S. Provisional Patent Application 61/684,176 filed Aug. 17, 2012. The Applicant hereby incorporates the aforementioned US Provisional Patent Applications as if fully set forth herein. 
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     TECHNICAL FIELD 
     Disclosed is a structural block designed for the construction of safe rooms, ventilation control structures, retaining walls, seals, and stoppings. The block is preferably composed of cement or an environmentally friendly, lightweight cementitious material. 
     DEFINITIONS 
     The following definitions are intended to clarify the terminology used herein. 
     Cementitious: having the properties of cement; e.g. a building material which may be mixed with a liquid, such as water, to form a paste which may be pumped or poured into a mold or other cavity, and then cured to form a solid. 
     Drivage: A general term for a roadway, heading, or tunnel in course of construction. It may be horizontal or inclined but not vertical. 
     Geopolymer: an inorganic polymeric material comprised of chains or networks of mineral molecules linked with covalent bonds. 
     Mains (i.e. Main Roadways): Major travel-way of a mine. Starting at the portal and usually continuing to the farthest extent of the mine. 
     Overcast: A structure that channels intake and return air courses through a main roadway intersection. 
     Rib: The side of a pillar or the wall of an entry, e.g. the solid coal on the side of any underground passage. 
     Roadway: An underground drivage. It may be a heading, gate, stall, crosscut, level, or tunnel and driven in coal, ore, rock or in the waste area. It may form part of longwall or board-and-pillar workings or an exploration heading. A roadway is not steeply inclined. 
     Roof: The ceiling of a roadway. 
     Seals: A permanent solid wall built across a mine roadway or shaft. 
     Stopping: A temporary solid wall built across a mine roadway or shaft. A stopping is typically constructed to channel fresh air (intake air) to working areas and channel contaminated air (return air) away from the working area as in the construction of a ventilation control device. 
     BACKGROUND 
     Underground mines must be properly ventilated so as to provide a substantially continuous flow of fresh air of sufficient volume to dilute and remove dangerous particulates like rock and coal dust and toxic gases such as CH 4 , CO, CO 2 , NO x , and SO 2 . These gases are created by the combustion of fuel by engines used underground in various applications and from blasting with explosives. Toxic gases can also be released from the strata itself. Methane, CH 4 , is of particular interest in coal mining since the gas is often found alongside coal deposits and because accumulations of this gas are odorless and can result in underground explosions. 
     Ventilation also plays an important role in the spontaneous heating of coal in an underground coal mine. If the ventilation rate is too high, heat is carried away by convection. If the ventilation rate is too low, the reaction rate becomes oxygen-limited. It has been found that there is an optimum ventilation flow to produce the maximum rate of temperature rise at the critical ambient temperature. Ventilation controls that are well constructed will reduce air contamination, power and fan maintenance costs. 
     The basic principle underlying mine ventilation is that air always moves from high pressure regions to low pressure regions. Therefore, in order to get the air to flow from the intake to the exhaust, the exhaust air must be at a lower pressure than the intake. As fresh air is pulled into the mine, contaminated air must be drawn out. The fresh air and contaminated air streams must be segregated to prevent contamination of the fresh air entering the mine and to ensure that fresh air is maintained at a higher pressure than the pressure at the entrance of the exhaust system where contaminated air and fresh air commingle. 
     If shafts are used as the two main airways, the intake airway is called the downcast shaft, and the exhaust airway is referred to as the upcast shaft. Sometimes one shaft can be split to provide both an intake and exhaust airway. If this pressure difference exists naturally between the two airways, then the mine has natural ventilation. Natural ventilation is one of the two methods of ventilating a mine. The other method is mechanical ventilation where fans are used to create the pressure differential. 
     Stoppings are used to prevent contamination of intake air with return air and to direct air to where it is needed so as to keep intake air from short-circuiting to the exhaust before it reaches the working area. Seals are also used to contain water or liquid-like mine wastes (tailings or slurry). Failure of a seal or stopping could result in a disastrous inundation of an underground mine or expose miners to unacceptable risks through the contamination of fresh air with toxic gases. 
     Seals are typically built of concrete blocks, sand fill, or other incombustible material. They are sealed tightly against the floor and ribs (i.e. sides) of a mine roadway so that no air can leak through. Porous stoppings such as concrete block stoppings are usually plastered with a cementitious coating on the high-pressure side to reduce air leakage. 
     Sometimes stoppings have a door, e.g. air-lock, in them to allow miners to pass through. Man doors are not meant to be ventilation controls, but if a man door is propped open it can affect airflow and may cause intake air to short circuit into the return air. 
     Because intake and return air frequently cross paths at intersections within the mine, overcasts and undercasts are used to permit the two air currents to cross without the intake air short-circuiting into the exhaust. Overcasts are like enclosed bridges built above the normal back level of the mine. Undercasts are like tunnels built below the normal floor of the mine. Undercasts are seldom used in a mine because they are apt to fill with water or debris which would severely slow down the flow of air through them. Overcasts are used more often and are typically constructed with planar concrete block walls sealed against the ribs and floor, and with some type of airtight roof made of pre-stressed concrete, railroad ties, metal sheeting or steel beams. Steel and other metals can sometimes be difficult to use underground due to fumes caused from welding causing air contamination. 
     In areas of heavy traffic, such as along long haulage roads, mine doors are usually hung in pairs while being used as ventilation controls. They are used to completely close off a mine passage yet open to allow equipment and people to pass through. Mine doors are generally used to keep air from flowing to areas where it is not needed. Mine doors can also be used to isolate separate splits of air. Mine doors are usually hung in pairs, forming an air lock that prevents unnecessary air flow when one of the pairs is opened. The doors should always be opened and closed one at a time in order to maintain the air lock. Mine doors are always hung so that the ventilating air pressure will push them closed if they are accidentally left open. However, the doors should always be closed after you pass through them. Some doors must be closed manually while others can be closed automatically. 
     Some mines also use fire doors to control airflow in the event of fire. They are usually built at shaft stations and other strategic locations so that if there is a fire they can be closed to serve as a barrier to the fire and contaminated air. In some mines the fire doors will close automatically when the carbon monoxide in the area reaches a certain level. Some mines will also have rollup doors in shop areas which close automatically when a mine fire warning is given. 
     When ventilation controls such as seals, stoppings, overcasts, and undercasts are installed in underground mines, they are required to meet the safety standards specified in 30 CFR 75.333. This safety standard requires that ventilation which includes overcasts, undercasts, shaft partitions, seals, stoppings, and regulators be constructed of noncombustible material. Noncombustible material is defined in 30 CFR 75.301 as a material which when used to construct a ventilation control results in a control that will continue to serve its intended function for one hour when subjected to a fire test incorporating an American Society for Testing and Materials, International, ASTM E-119-88 temperature/time heat input, or equivalent. Additionally, the ventilation control must meet a flexural strength that is equal to or greater than a conventional 20 cm hollow core concrete block stopping. The 20 cm hollow core concrete block with mortared joints has been tested and shown to have a minimum strength of 190 kg/m 2 . ASTM E-72-80 is used to determine the flexural strength. Also, sealants or coatings applied to ventilation controls to reduce air leakage must have a flame spread index of 25 or less. The flame spread index test specified in 30 CFR 75.333 is detailed in ASTM E-162-87. The aforementioned codes, regulations, and specifications are intended to serve as examples only with it being understood that other codes, regulations, and specifications can apply depending on the application and the jurisdiction. 
     The basis for the safety standard of fire endurance and flexural strength relates to concrete block. Concrete block has long been the material of choice for the construction of stoppings and seals. However, the construction of a concrete block stopping is labor intensive and time consuming. Concrete blocks are heavy, a typical 20 cm wide by 20 cm high by 41 cm long hollow concrete block has an average mass of approximately 18 kg, and injuries from carrying and lifting the blocks often result. Developments in material science have resulted in newer, lighter cementitious materials to replace the use of concrete block, particularly for the construction of retaining walls, stoppings, and seals. 
     SUMMARY 
     Provided is a convex, front-to-rear tapered building block formed of a cementitious material, e.g. geopolymer, or cement. The block is preferably pre-cast, but may be cast on-site as needed. The block is primarily intended for use in the construction of mine stoppings or seals by stacking a plurality of blocks in ascending layers between the walls of a mine shaft. The blocks, when assembled, form a parabolic, i.e. arcuate, wall which possesses superior compressive strength against shock waves from explosions as compared to a traditional flat wall, i.e. substantially non-parabolic wall. 
     The block may be formed with annular or semi-annular, e.g semicircular, cylindrical cavities so as to create annular cylindrical channels through blocks stacked within the assembled wall. The channels can include smaller radius pathways through which linear reinforcements may be installed and larger pathways through which larger reinforcements can pass. The annular and semi-annular cavities are also useful to reduce the mass of each block, thus yield more efficient material handling when compared to solid blocks. The annular cavities also add to strength through the formation of internal arch structures. The cylindrical pathways can be filled with a cementitious material for reinforcement so as to create a more permanent structure or “dry stacked” to create a temporary structure which can be subsequently deconstructed and moved for reassembly elsewhere. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a parabolic wall constructed from the subject structural block. 
         FIG. 2  depicts a partial cutaway view of a block assembly with vertical and lateral supports. 
         FIG. 3  depicts a perspective view of a foundation-block embodiment of the subject structural block. 
         FIG. 4  depicts a plan view of the top face of one embodiment of the subject structural block. 
         FIG. 5  depicts a perspective view of one embodiment of the subject structural block utilizing left and right mated blocks. 
         FIG. 6  depicts a plan view of the top surface of the structural blocks of  FIG. 5 . 
         FIG. 7  depicts a perspective view of one embodiment of the subject structural block utilizing left and right mated blocks. 
         FIG. 8  depicts a plan view of the top surface of the structural blocks of  FIG. 7 . 
         FIG. 9  depicts an exploded perspective view of the wall assembly of the structural blocks of  FIG. 3 . 
         FIG. 10  depicts an exploded perspective view of the wall assembly of the structural blocks of  FIG. 5 . 
         FIG. 11  depicts an exploded perspective view of the wall assembly of the structural blocks of  FIG. 7 . 
         FIG. 12  depicts a cross-sectional view of a wall assembly of the subject structural block. 
         FIG. 13  depicts the subject structural block assembled as a parabolic wall with ends embedded in the ribs of a mine shaft. 
         FIG. 14  depicts a plan view of the subject structural block assembled as a parabolic wall with ends embedded in the ribs of a mine shaft and refocusing the energy from a shock wave. 
         FIG. 15  depicts a perspective view of the subject structural block assembled as a parabolic wall as part of a ventilation control device with an air-lock. 
         FIG. 16  depicts a plan view of a safe room and air-lock as part of a ventilation control device in a mine shaft. 
     
    
    
     DETAILED DESCRIPTION 
     Provided is a convex, front-to-rear tapered structural block  100  formed of a geopolymer or similar cementitious material or cement. The block  100  is preferably pre-cast, but may be cast on-site as needed. When properly assembled, the convex blocks  100  form a parabolic wall  80 . The length of a parabolic wall  80  constructed from the block  100  is related to its arc radius and thus the angle measure on the anterior face  10  and the posterior face  15  of the block  100 . 
     A structural block  100  embodiment, as shown in  FIGS. 1-16 , is stackable so as to mate or interlock with other blocks  100  to reinforce any structure assembled therefrom. In one embodiment, the block  100  of the present innovation is made available as a foundation-block  60 , see  FIG. 3 , and a wall-block  40 , see  FIG. 2 . As depicted in  FIGS. 1-2 and 9-12 , the wall-blocks  40  are preferably stacked in vertically ascending horizontal layers atop a bottom layer of foundation-blocks  60  or alternatively wall-blocks  40  and stacked in subsequent horizontal rows on top of each other until the head-blocks  65 , i.e. roof-blocks  65 , can be utilized in the last row abutting the roof  72 . 
     Each wall-block  40  possesses a key  12 , e.g. a lip  12 , extending down from the bottom face  25  of the block  100  from the anterior face  10  back towards the posterior face  15 , preferably at the bottom of the substantially planar anterior face  10  which extends downward in a substantially planar continuation of the face, extending part-way along the substantially planar bottom face  25  toward the posterior face  15  of the block  100 . The block  100  further possesses a keyway  14 , or seat  14 , to receive the key  12 . The keyway  14  is preferably a groove along the joint where the anterior face  10  of the wall-block  40  and the top face  20  of the wall-block  40  meet and is configured to receive the key  12  from the bottom face  25  or base  25  of a block  100  stacked upon the top face  20  of a lower block  100  so as to form a mechanical mating and/or friction fit arrangement. 
     The mating of the key  12  and keyway  14  ensures correct alignment of each block  100  and the integrity of the completed wall  80 . The key-to-keyway mating also aids in the transfer of the load between layered blocks  100 . In one embodiment, the wall-block  40  preferably possesses at least one central aperture  45  running from the top face  20  to the bottom face  25 . One purpose of the central aperture  45  is mass reduction. An additional purpose of the central aperture  45  is to provide a pathway through which a vertical support  33  may pass. Yet another purpose of the central aperture  45  is to provide a passageway which terminates at the floor  74  for introducing a cementitious filling into the wall  80  for reinforcement. The central aperture  45  vertically aligns with a vertical support aperture  37  in the block  100  above and the block  100  below in a staggered block configuration. In a still further embodiment, the blocks  100  possess vertical groove  35  on the each lateral face  30  which are configured to mate with other vertical grooves  35  when stacked next to each other so as to form annular, cylindrical vertical support apertures  37  which extend vertically between the blocks  100 . As depicted in  FIGS. 2 and 9-12 , the vertical support apertures  37  formed by the vertical groove  35  can be utilized for the installation of vertical supports  35  therein. The vertical supports  35  are preferably fabricated from steel. 
     A lateral groove  22  runs across the top face  20  of the block  100  at roughly the same arc radius as the vertical groove  35  and central aperture  45  and with no greater than the same arc angle measure as the anterior face  10  of the block  100  and no less than the arc angle measure of the posterior face  15 . In a preferred embodiment, the width of the lateral groove  22  is approximately 1.5 inches (3.8 cm) and is semi-annular in geometry so as to receive an arc shaped lateral support  24  along the length of the wall  80 . In a preferred embodiment, the lateral supports  24  may be mechanically affixed to the vertical supports  33  by tying with wire or clamping. In some applications, the lateral supports  24  can be welded to the vertical supports  33 . 
     As an example, the dimensions of a wall-block  50  embodiment as depicted in  FIG. 7 , are (a) a length of 16 inches (40.64 cm) along the left lateral face  31  and the right lateral face  33  including the wall-block body  51  and key  12 , (b) a length of 14.5 inches (36.83 cm) along the along the left lateral face  31  and the right lateral face  32  including the wall-block body  51  but excluding the key  12 , (c) a length of 1.5 inches (3.81 cm) along the left side face and the right side face excluding the wall-block body  51  but including the key  12 , 1.5 inches (3.81 cm), (d) an arc length of 8.35 inches (21.21 cm) along the anterior face  10 , an arc length of 7.3 inches (18.54 cm) along the posterior face  15 , (e) an arc angle of approximately 2°, (f) a height of 5 inches (12.7 cm) along the wall-block body  51 , (g) a 5 inch (12.7 cm) tall key  12  extending 1.5 inches (3.81 cm) anteriorly from the anterior end of the wall-block body  51  and vertically offset down the anterior face  10  of the half-wall-block body  51  approximately 1.25 inches (3.18 cm), (h) a 0.25 inch×0.25 inch (6.35 mm×6.35 mm) top chamfer  43  in the top anterior edge of the wall-block body  41 , and (i) a 0.25 inch×0.25 inch (6.35 mm×6.35 mm) bottom chamfer  44  in the posterior bottom edge of the key  12 . When one wall-block  50  is placed above another wall-block  50 , the bottom chamfers  44  of the top wall-block  50  mates with the bottom chamfer  44  of the bottom block  50 . Ideally the blocks  100  are stacked so as to offset their vertical seams  48 , thus a wall-block  50  will engage two wall-blocks  50  on its top face  20  and two wall-blocks  50  on its bottom face  25 . 
     The aforementioned wall-block  50  embodiment is preferably comprised of two versions, a left-wall-block  55  and a right-wall-block  57 . Each wall-block  50  possesses the same keyway  14 , i.e. seating groove  14 , and key  12  and the same arc angle measure across its anterior face  10 . In a preferred embodiment, the left-wall-block and right-wall-block are substantially half large-wall-blocks  40  which allow the user to adjust the length of the assembled wall without blocking the central apertures  45  and vertical support apertures  37  so as to interfere with the use of vertical supports  33  to reinforce the wall  80 . 
     As an example, the dimensions of a large-wall-block  40  embodiment, as depicted in  FIG. 9 , for use with an 18 ft (5.5 m) wide roadway are (a) a length of 16 inches (40.64 cm) along the left lateral face  31  and the right lateral face  32  including the large-wall-block body  41  and key  12 , (b) a length of 14.5 inches (36.83 cm) along the along the left side face and the right side face including the large-wall-block body  41  but excluding the key  12 , (c) a length of 1.5 inches (3.81 cm) along the left lateral face  31  and the right lateral face  32  excluding the large-wall-block body  41  but including the key  12 , 1.5 inches (3.81 cm), (d) an arc length of 16.7 inches (42.42 cm) along the anterior face  10 , an arc length of 14.6 inches (37.08 cm) along the anterior face, (e) an arc angle of approximately 4°, (f) a height of 5 inches (12.7 cm) along the large-wall-block body  41 , (g) a 5 inch (12.7 cm) tall key  12  extending 1.5 inches (3.81 cm) anteriorly from the anterior end of the large-wall-block body  41  and vertically offset down the anterior face  10  of the large-wall-block body  41  approximately 1.25 inches (3.18 cm), (h) a 0.25 inch×0.25 inch (6.35 mm×6.35 mm) top chamfer  43  in the top anterior edge of the large-wall-block  40 , and (i) a 0.25 inch×0.25 inch (6.35 mm×6.35 mm) bottom chamfer  44  in the posterior bottom edge of the key  12 . When one wall-block  40  is placed above another large-wall-block  40 , the bottom chamfers  44  of the top large-wall-block  40  mates with the bottom chamfer  44  of the bottom large-wall-block  40 . Ideally the large-wall-blocks  40  are stacked so as to offset their vertical seams  48 , thus a large-wall-block  40  will engage two large-wall-blocks  40  on its top face  25  and two large-wall-blocks  40  on its bottom face  25 . 
     As depicted in  FIG. 3 , a foundation-block  60 , i.e. starter block, is substantially identical to a wall-block  50  or large-wall-block  40  without the key  12  for seating. A further embodiment utilizes a head-block  65 , i.e. roof-block  65 , which possesses a key  12  formulated or cured to possess a lower compressive strength relative to the wall-block  50  to allow for settling of a mine roof  72 . 
     As depicted in  FIGS. 13-16 , an underground mine seal or stopping may be by stacking layers of wall-block  40  atop the foundation-block  60 . A cementitious product either identical or similar to the cementitious material from which the blocks  100  are fabricated may be used as a mortar, a coating, and/or a filler. The blocks  100  are mated by key  12  to keyway  14  and form a parabolic wall  80  across a roadway  70 . The ends of the wall  80  terminate in excavated restraining pockets  93  within the ribs  76  so as to redirect and disperse some of the force from a blast wave along the arc of the wall  80  and into the ribs  76 . A parabolic wall  80  is better suited than a flat-faced wall, i.e. a wall whose face is substantially an un-curved planar wall, for withstanding the forces of shock wave from a blast as measured by ASTM E72-80—Section 12, “transverse loading of a vertical specimen.” A parabolic wall absorbs some of the shock wave from a blast but redirects the remainder along the arc length of the parabolic wall  80  and into the ribs  76  of a mine shaft. Ideally, a cementitious coating for sealing covers the surface of the parabolic wall  80  and its joints along the mine shaft walls  76 , i.e. ribs  76 , floor  74 , and roof  72 . 
     The blocks  100  may be utilized to create walls  80  for safe rooms, ventilation control devices, dams, and similar underground structures which require sealing. Such walls  80  can also be utilized to create air- to allow miners to pass from areas of high pressure to areas of low pressure without short-circuiting air flow. Additional uses include the construction of walls, e.g. retaining walls, and other walled civil engineering projects in loose soil. When cast from geopolymers, these blocks  100  have the added advantage of being faster to assemble than traditional concrete blocks due to reduced mass, and result in improved workplace ergonomics and safety. 
     One such useful cementitious material is HySSIL™, a geopolymer available from HySSIL PTY LTD. Geopolymers are chains or networks of mineral molecules linked with co-valent bonds. Hardened geopolymers are x-ray amorphous at ambient and medium temperatures and x-ray crystalline at temperatures &gt;500° C. They are created in an alkaline medium, e.g. (Na, K, Ca) hydroxides and alkali-silicates yielding poly(silicates)-poly(siloxo) types of geopolymers or poly(silico-aluminates)-poly(sialate) types of geopolymers, or in an acidic medium, e.g. Phosphoric acid yielding poly(phospho-siloxo) and poly(alumino-phospho) types of geopolymers. As an example, one of the geopolymeric precursors, MK-750 (metakaolin) with its alumoxyl group —Si—O—Al═O, reacts in both systems, alkaline and acidic. Siloxo-based and organo-siloxo-based geopolymeric species also react in both alkaline and acidic medium. 
     Geopolymer terminology is based on different chemical units, essentially for silicate and aluminosilicate materials, classified according to the Si:Al atomic ratio: 
     Si:Al=0, siloxo 
     Si:Al=1, sialate (acronym for silicon-oxo-aluminate of Na, K, Ca, Li) 
     Si:Al=2, sialate-siloxo 
     Si:Al=3, sialate-disiloxo 
     Si:Al&gt;3, sialate link. 
     See  IUPAC Symposium on Long - Term Properties of Polymers and Polymeric Materials , Stockholm 1976, Topic III: Joseph Davidovits, Solid-Phase Synthesis of a Mineral Blockpolymer by Low Temperature Polycondensation of Alumino-Silicate Polymers. 
     Silicates and their crystal structures were originally classified based on the concept of the ionic theory by L. Pauling. The fundamental unit is a tetrahedral complex consisting of a small cation such as Si 4+ , or Al 3+  in tetrahedral coordination with four oxygens. The structures involved with geopolymerization are in fact siloxonate/sialate covalent constructs, not ionic. Geo-chemical syntheses are carried out through oligomers (dimer, trimer, tetramer, pentamer) which provide the actual unit structures of the three dimensional macromolecular edifice. 
     Geopolymers are generally comprised of the following molecular units (i.e. chemical groups):
         —Si—O—Si—O— siloxo, poly(siloxo)   —Si—O—Al—O— sialate, poly(sialate)   —Si—O—Al—O—Si—O— sialate-siloxo, poly(sialate-siloxo)   —Si—O—Al—O—Si—O—Si—O— sialate-disiloxo, poly(sialate-disiloxo)   —P—O—P—O— phosphate, poly(phosphate)   —P—O—Si—O—P—O— phospho-siloxo, poly(phospho-siloxo)   —P—O—Si—O—Al—O—P—O— phospho-sialate, poly(phospho-sialate)   —(R)—Si—O—Si—O—(R) organo-siloxo, poly-silicone   —Al—O—P—O— alumino-phospho, poly(alumino-phospho)   —Fe—O—Si—O—Al—O—Si—O— ferro-sialate, poly(ferro-sialate).       

     Generally, geopolymers are developed and applied in 10 main classes of materials:
         Waterglass-based geopolymer, poly(siloxonate), soluble silicate, Si:Al=1:0   Kaolinite/Hydrosodalite-based geopolymer, poly(sialate) Si:Al=1:1   Metakaolin MK-750-based geopolymer, poly(sialate-siloxo) Si:Al=2:1   Calcium-based geopolymer, (Ca, K, Na)-sialate, Si:Al=1, 2, 3   Rock-based geopolymer, poly(sialate-multisiloxo) 1&lt;Si:Al&lt;5   Silica-based geopolymer, sialate link and siloxo link in poly(siloxonate) Si:Al&gt;5   Fly ash-based geopolymer   Ferro-sialate-based geopolymer   Phosphate-based geopolymer, AlPO4-based geopolymer   Organic-mineral geopolymer.       

     As an example: geopolymerization with metakaolin MK-750 involves three phases:
         1. Alkaline depolymerization of the poly(siloxo) layer of kaolinite.   2. Formation of the ortho-sialate (OH) 3 —Si—O—Al—(OH) 3  molecule.   3. polymerization (polycondensation) into higher oligomers and polymers.       

     The geopolymerization kinetics for Na-poly(sialate-siloxo) and K-poly(sialate-siloxo) are slightly different. This is probably due to the different dimensions of the Na +  and K +  cations, K +  being bigger than Na + . Polycondensation into a Na-poly(sialate-disiloxo)albite framework results in the more crystalline structure as shown below. 
     
       
                 
         
             
             
         
      
     
     The geopolymer block  100  of a preferred embodiment has a density of approximately half that of concrete, but with similar durability and higher strength. The lower mass product possesses less embodied energy in its creation, requires less energy to transport than similar ordinary Portland cement concrete blocks, thus generating a cost savings in fuel and a benefit to the environment. The use of recycled fly ash in the preferred geopolymer results in a reduction of CO 2  emissions of approximately 60% and a block cast therefrom embodies approximately 60% less energy in its manufacture than a similar concrete block. The geopolymer block possesses a higher resistance to fire and chemicals as well as greater flexural and compressive strength. The geopolymer may be formulated and/or cured to possess a reduced compressive strength for use with the wall-block  40  laid at the top of the wall  80 , i.e. head-block  65 , in contact with the roof  72  to allow for some roof  72  convergence along the top layer. 
     A geopolymer formed block  100  has the advantage of being a “green” product whose environmental benefits result in a lower carbon footprint and can result in carbon credits for greenhouse gas mitigation which can then be used for expanded growth or sold in the carbon credit market. 
     Inert particulate materials (e.g. sand, rock, and/or crushed concrete) added to cement to influence the physical properties and/or economics of concrete.