bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative Petrographic Technique for Concrete Damage Due to ASR: Experimental and Application
Authors: Rivard P , Fournier B , Ballivy G 
Published: January 2010

Abstract
An automatic petrographic test procedure for quantifying damage in concrete affected by alkali-silica reaction (ASR) is presented in this paper. A computer image analysis program was designed to quantify the degree of microcracking and the amount of silica gel resulting from ASR. The procedure involves the petrographic examination at a magnification of ×20 of polished concrete sections impregnated with fluorescent epoxy resin for cracking and uranyl acetate coated sections for the determination of their silica gel content. Also, the data were compared to the results obtained from a semi-quantitative petrographic method, i.e., the Damage Rating Index commonly used in Canada for evaluating the condition of concrete affected by ASR.
The petrographic examination was first carried out on laboratory sections cut and polished from concrete prisms incorporating two different aggregate types, the Spratt limestone and the Potsdam sandstone. Both methods were also applied to specimens prepared from a core collected from a large dam affected by ASR. Good correlation was obtained between analytical parameters derived from the image analysis method and the expansion levels of the laboratory test prisms; however, no explicit relation was found to date between the amount of gel as measured in this study and the expansion level.
This study shows that the quantitative petrographic method using the image analysis and the Damage Rating Index Method can be used to estimate the condition and current expansion of concrete specimens cored from concrete structures affected by ASR.
Influence of Silica Fume on the Stresses Generated by Alkali-Silica Reaction
Authors: Ferraris C , Garboczi E , Stutzman P , Winpigler J , Clifton J 
Published: January 2010

Abstract
Present test methods for determining the suitability of a given combination of cement and aggregates with respect to the potential for alkali-silica reaction (ASR) are based on the measurement of the expansion of the concrete/mortar under prescribed conditions. The scope of this study was to determine the influence of the addition of silica fume as a cement replacement on the stresses generated by the specimen, a parameter that could be useful for the engineer. Cylindrical specimens were placed in a frame equipped with a load cell that fixed the axial strain at approximately zero and measured the axial stress generated over time. A replacement of cement by silica fume at a dosage of 15% by mass for two different w/c ratios led to a significant decrease of the measured stress. SEM observations helped to provide a tentative explanation for the stress and expansion reduction mechanisms with the addition of silica fume.
Case Study in Performance Testing of Hydraulic Cement
Authors: Struble LJ , Taylor PC , Conway JT 
Published: January 2010

Abstract
A testing program has been initiated to measure and compare the performance in concrete of two hydraulic cements. Both meet the prescriptive specification for portland cement; one cement is a mixture of 98% portland cement and 2% slag, and the other is a similar portland cement with no slag. The program compares their performance in a broad range of standard mortar and concrete tests. Mixes include both chemical admixtures (an air-entraining agent and a water reducer) and mineral admixtures (ground, granulated blast furnace slag, and Class F and Class C fly ashes). The preliminary results show only minor differences in performance between the two cements. An important conclusion of this presentation is that a standard protocol is needed for measuring performance of cement in concrete. The testing program we used is quite broad and includes several tests that are not part of the performance specification for hydraulic cement. Many of the standard tests for hydraulic cement provide quality tests for use in cement production, but do not assure that the cement will perform properly in concrete. A standard protocol would include a range of tests that assure performance of cement in concrete, would include other concrete materials (aggregates, chemical admixtures, and mineral admixtures), and would reduce the number of tests required to assure performance of a new cementitious material.
Analysis of Variables Influencing the Average-Residual Strength of Fiber-Reinforced Concrete
Authors: Hays CD , Mohammed NK , Zollo RF 
Published: January 2010

Abstract
The ASTM C 1399, Test Method for Obtaining Average Residual-Strength of Fiber-Reinforced Concrete, became a standard of ASTM International in December 1999. The test method was developed to provide a practical method, both functionally and economically, for evaluating the performance of fiberreinforced concrete (FRC) of any mixture design. The method is a flexure test and the result, the average residual strength (ARS), is a useful parameter in design and quality control testing. The current standard requires a third-point flexural loading-configuration that complies with ASTM C 78, Standard Test Method for Flexural Strength of Concrete (Using Simple Beam With Third-Point Loading), and net-deflection data analysis. Five factors, consisting of loading configuration, deflection measurement, support apparatus, testing machinery and fiber material type are used as test variables in this research in a testing program suited to the application of a statistical analysis of variance procedure, ANOVA, for their affect on ARS. The results of the test program show that no significant effect is found on the value of ARS computed according to ASTM C 1399 for the modified ASTM C 78, MC78, test apparatus when using either gross or net deflection, or when using third-point or centerpoint loading. There is a significant effect on the value of ARS computed according to ASTM C 1399 for the ASTM C 78 test apparatus when comparing the same test variables.
Evaluation of Precision of a Nuclear Gauge for Measurement of Water and Cement Content of Fresh Concrete
Authors: Nagi M , Whiting D 
Published: January 2010

Abstract
An experimental program was conducted to develop a precision statement for a commercially available nuclear field gauge developed to measure both water and cement contents of fresh concrete. Five gauges were tested at a single site. Three separate batches of concrete having different mixture proportions were tested; each gauge was run by a single operator. Data analysis was carried out following ASTM C 802-94 and the precision statements were developed in accordance with ASTM C 670-91a. Gauge count ratio was used rather than actual cement and water content to avoid the errors associated with gauge calibration. The “one-sigma limit” and the “difference two-sigma limits” were obtained. The precision estimates appear to reflect actual experience with the gauge and can be used to compare results obtained in the field.
Evaluation of Tests for Toughness/Abrasion Resistance and Durability/Soundness of Coarse Aggregates
Authors: Wu Y , Parker F , Kandhal PS 
Published: January 2010

Abstract
Many tests have been developed to empirically characterize aggregate without necessarily strong relationships with the performance of final products incorporating these aggregates. This seems to be particularly true for “toughness and abrasion resistance” and “durability and soundness.” Toughness/abrasion resistance and durability/soundness of aggregate are correlated, but represent resistance to degradation when subject to mechanical forces and weathering, respectively. A literature review identified five toughness/abrasion resistance and four durability/soundness test procedures. Sixteen aggregates with a wide range of properties were tested with eight of the identified test procedures. Results from the tests and test precisions were compared.
Early Shrinkage Development in a High Performance Concrete
Authors: Lepage S , Baalbaki M , Dallaire É , Aïtcin PC 
Published: January 2010

Abstract
As autogenous shrinkage in low water/binder concrete starts to develop almost as soon as portland cement hydrates it is very important to start shrinkage measurement just after the dormant period. One simple way to do it is to insert a gage and a thermocouple at the center of the concrete sample to monitor early shrinkage. Vibrating wire gages having a low rigidity modulus can be used to monitor at the same time length and temperature changes. It is then possible to evaluate separately the actual total deformation while concrete is hydrating at a temperature which is not constant, and autogenous shrinkage in isothermal conditions.
Early shrinkage measurements in a 0.30 water/binder ratio concrete beam (250 by 250 by 900 mm) are presented. It is shown that during the first 50 h due to the temperature increase of concrete the actual total shrinkage is much smaller than the autogenous shrinkage, occurring in isothermal conditions particularly during the first 24 h. Moreover a slight swelling of concrete has even been measured from 4 to 16 h.
Relative humidity inside the concrete sample was measured using a special probe placed close to the vibrating wire gages. This probe was inserted just after initial setting, 6 h after casting. The initial reading indicates a (RH) relative humidity of 97% and after 28-days the measured RH was still 93%.
Possible Mechanisms of Expansion of Concrete Exposed to Elevated Temperatures During Curing (Also Known as DEF) and Implications for Avoidance of Field Problems
Authors: Scrivener KL , Damidot D , Famy C 
Published: January 2010

Abstract
The phenomenon of expansion in concretes which have been exposed to elevated temperatures during curing and subsequently to moisture is discussed; in particular, the relationship of this expansion to the formation of ettringite after initial curing (delayed ettringite formation). Evidence is also presented for the possible implication of the C-S-H gel in the expansion process.
The avoidance of this type of expansion in field concrete is also discussed. The data show that expansion occurs only when the concrete temperature during hydration exceeds 65°C and that the proportion of cements that expand under laboratory testing conditions increases as the temperature of exposure increases. Tests on limited numbers of cements have indicated that some factors in the cement that appear to influence the tendency of the concrete to expand after elevated temperature curing (such as, alkalis content, fineness, SO3), but there is no general relationship between these factors and the degree of expansion valid across the range of commercial cements. This means that the selection of a cement within certain limits will not guarantee the avoidance of expansion if the concrete is exposed to a high enough temperature during curing.
Cementitious Composites Containing Recycled Tire Rubber: An Overview of Engineering Properties and Potential Applications
Authors: Nehdi M , Khan A 
Published: January 2010

Abstract
One of the major environmental challenges facing municipalities around the world is the disposal of worn out automobile tires. To address this global problem, several studies have been conducted to examine various applications of recycled tire rubber (fine crumb rubber and coarse tire chips). Examples include the reuse of ground tire rubber in a variety of rubber and plastic products, thermal incineration of waste tires for the production of electricity or as fuel for cement kilns, and use of recycled rubber chips in asphalt concrete. Unfortunately, generation of waste tires far exceeds these uses. This paper emphasizes another technically and economically attractive option, which is the use of recycled tire rubber in portland cement concrete. Preliminary studies show that workable rubberized portland cement concrete (rubcrete) mixtures can be made provided that appropriate percentages of tire rubber are used in such mixtures. Achievements in this area are examined in this paper, with special focus on engineering properties of rubcrete mixtures. These include: workability, compressive strength, split-tensile strength, flexural strength, elastic modulus, Poisson's ratio, toughness, impact resistance, sound and heat insulation, and freezing and thawing resistance. The benefits of using magnesium oxychloride cement as a binder for rubberized concrete mixtures are discussed. Various applications in which rubcrete could be advantageous over conventional concrete are described.
Direct Spectrophotometric Determination of Aluminum Oxide in Portland Cement and Cement Clinker
Authors: Idriss KA , Hashem EY , Abdel-Aziz MS , Ahmed HM 
Published: January 2010

Abstract
A spectrophotometric study of the complexation reaction between Al3+ and Quinizarin (QUIN) is carried out to ascertain the suitability of the complex formed for direct spectrophotometric determination of aluminum. The absorbance at 550 nm, due to the aluminum-QUIN complex, formed at pH 3.8, is recommended for the determination of aluminum content of portland cement and cement clinker. The proposed method is simple and rapid and possesses reasonable selectivity. Interference of iron (III), generally present in portland cement, is eliminated by addition of ascorbic acid. The results obtained for several SRMs, portland cement samples, and a variety of cement materials demonstrate that the proposed method allows precise and accurate determination of Al2O3 content over the concentration range 1.4 to 5.75 μg/mL of aluminum. The determination of Al can be carried out successfully in absence of a masking agent by using first-derivative spectrophotometry. Verification and use of control charts in spectrophotometric determination of Al is achieved. Record of verifier response during routine operation establishes that the method is being maintained in statistical control.
An Investigation of the Minimum Expected Uncertainty in the Linear Traverse Technique
Authors: Snyder K , Hover K , Natesaiver K 
Published: January 2010

Abstract
Analytical solutions to the minimum uncertainty in the linear traverse technique are presented. These solutions are based on the concept of a perfect operator conducting multiple linear traverses using highly accurate instruments on a well-prepared concrete specimen. The air void parameters calculated from each of the traverses will not be the same and will be distributed around an average value. The uncertainty in the knowledge of the true values of the parameters can be characterized by the dispersion of the multiple values of the parameters obtained. The minimum uncertainty is quantified here as twice the standard deviation (95% confidence interval) of the air void parameter values. The analytical solutions were verified by means of computer simulations of a linear traverse being performed on hardened air-entrained cement paste. Results indicate agreement between the analytical solutions and the computer simulations. The minimum uncertainty in measurements of air content, specific surface, and spacing factor are dependent primarily upon the number of chords in a traverse and secondarily upon the coefficient of variation of the chord lengths. The equations derived herein are applied to the results of a linear traverse conducted on an actual specimen of air-entrained concrete.
Influence of Sulfate Ions on Chloride-Induced Reinforcement Corrosion in Portland and Blended Cement Concretes
Authors: Al-Amoudi OSB , Rasheeduzzafar A-A , Maslehuddin M , Abduljauwad SN 
Published: January 2010

AbstractReinforced concrete structures serving in marine environments and in soils contaminated with high concentrations of chloride and sulfate salts are prone to two problems, namely reinforcement corrosion and sulfate attack. While a substantial number of studies have been carried out on reinforcement corrosion in pure chloride environments, practically no data exist on the influence of sulfate ions on chloride-induced reinforcement corrosion in plain and blended cement concretes.In this study, the effect of chloride and sulfate ions, or both on reinforcement corrosion in plain and blended cement concretes was investigated. Reinforcement corrosion was evaluated by measuring corrosion potentials and corrosion current density at periodic intervals. The mechanisms of chloride-induced reinforcement corrosion in the presence of sulfate ions was elucidated by extracting and analyzing the pore solution.The time to initiation of reinforcement corrosion was observed to be strongly related to the mobility and diffusivity of the chloride ions. Once the chloride and sulfate ions reach the steel-concrete interface, the concomitant presence of sulfates and chlorides generally increases the corrosion rate of steel in both plain and blended cements. Despite the very aggressive internal chemical environment in silica fume cement concrete, the corrosion current density was the lowest and generally below the threshold level. The longer time to initiation of corrosion and lower corrosion current density observed in silica fume cement concrete, even in very aggressive environments marked by high chloride and sulfate concentrations, emphasizes its usefulness in aggressive media.
Hexavalent Chromium in Portland Cement
Authors: Klemm WA 
Published: January 2010

Abstract
Due to increasing environmental and health-related concerns, the amount of hexavalent chromium found in portland cement is coming under increasing scrutiny. Hexavalent chromium has been classified as a carcinogen, and its release into the air or groundwater is regulated and controlled under many Federal and State regulations.
In addition to carcinogenic risks, soluble chromium has long been linked to chromate-sensitive contact dermatitis of workers exposed to wet cement or concrete. As a consequence, Scandinavian countries have limited the amount of hexavalent chromium allowed in portland cement. This is generally accomplished by intergrinding clinker and gypsum with the chemical reducing agent, ferrous sulfate, which maintains hexavalent chromium below 2 ppm. Developments in this area are reviewed.
Studies at a California cement plant showed that more than half of the hexavalent chromium in the cement was contributed by the grinding media in the finish mill. Attempts to reduce the chromium to its benign trivalent form with ferrous sulfate failed in full-scale trial grinds, due to oxidation of the ferrous iron. This indicates that further research is needed to find better methods for introducing ferrous sulfate into the cement or to develop more stable reducing agents.
Lipase-Catalyzed Production of Biodiesel from Tallow
Authors: Han Jingtian , Silcock Patrick , Bell Martin , Birch John 
Published: January 2010

Abstract
The use of enzymes (lipases) to convert triglycerides to acylesters (biodiesel) holds potential as an alternative to the conventional base catalyzed processes. Advantages include the ability to utilize impure feedstocks, less downstream processing, and potentially overcoming the requirement to dedicate expensive agricultural land for raw oil production. Lipid sources such as oleaginous microorganisms along with processing wastes may provide renewable substrates requiring minimal pre-processing. Transesterification of vegetable oils and restaurant grease has been studied using immobilized enzymes as catalysts with an optimal temperature of around 35°C. This study investigates ester formation from unrefined tallow at 50°C employing similar enzymes used for vegetable oils. Novozyme 435 (a commercially available immobilized enzyme) proved best at a loading of 2 % w/w based on tallow reaching 98 % conversion after 96 h using methanol as the chosen alcohol, with immobilized lipase from Pseudomonas cepacia (PS-30) (69 % conversion) proving superior to free PS-30 (11 % conversion), and the other lipases barely registering any activity. Immobilized PS-30 was chosen to investigate the effect of lipase level, alcohol reactant, water content of the tallow, grade of tallow, and influence of solvent or a solvent-free system. Results showed that water content of up to 0.6 % and the tallow grade had no effect on ester formation, while enzyme loadings of at least 4 % were needed to achieve a good conversion that plateaued at around 6–8 % water content. The primary alcohols ethanol, propanol, and butanol reacted equally efficiently with immobilized PS-30, reaching 96–99 % conversion, while methanol performed less well along with 2-propanol and 2-butanol where conversion was only in the range of 10–40 %. Transesterification reactions worked best in a non-polar environment with hexane as solvent (95 % conversion), with a higher polarity solvent, acetonitrile, also proving an efficient medium (80 % conversion), while solvents intermediate to these had little comparative activity, suggesting that solubility of reactants and products is a key driver in the conversion. Interestingly, petro-diesel proved to be a better solvent than using either a solvent-free system or a diethylether environment.
Long-term morphological, hormonal, and clinical follow-up in a single unit on 118 patients with adrenal incidentalomas
Authors: Giordano R , Marinazzo E , Berardelli R , Picu A , Maccario M , Ghigo E , Arvat E 
Published: January 2010

ObjectiveTo evaluate long-term morphological, functional, and clinical outcome in adrenal incidentalomas.Design and methodsA total of 118 patients (77 F and 47 M; age 62.3±1.0 years) with adrenal incidentalomas were evaluated at baseline and followed-up for median 3 years (range 1–10 years) by clinical, biochemical, hormonal, and morphological evaluation. Among them, six patients with diagnosis of subclinical Cushing's syndrome (SCS) underwent surgery.ResultsAt entry, 86% (n=102) of tumors were nonfunctioning (NF) and 14% (n=16) showed SCS. Comparing NF with SCS patients, a significantly higher percentage of dyslipidemia was found in the group of SCS patients (50 vs 23%,P=0.033). During follow-up, adrenal function remained normal in all NF patients, none of them developed subclinical or overt endocrine disease. The cumulative risk of mass enlargement was globally low (25%), but progressive up to 8 years. SCS was confirmed in all patients, and none of them shifted to overt Cushing's syndrome. The cumulative risk of developing metabolic–cardiovascular abnormalities was globally low (22%), but progressive up to 8 years and new diseases were recorded in the group of NF patients only (three patients with dyslipidemia, four with impaired fasting glucose/impaired glucose tolerance, and three with diabetes mellitus). SCS patients who underwent surgery did not show any significant clinical improvement.ConclusionsThe risk of mass enlargement, hormonal, and metabolic impairment over time is globally low. Conservative management seems to be appropriate, but further prospective studies are needed to establish the long-term outcome of such patients, especially for metabolic status, cardiovascular risk profile and their relationship with endocrine function.