Laurent Barcelo - Academia.edu (original) (raw)
Papers by Laurent Barcelo
SP-227: Shrinkage and Creep of Concrete, 2005
This paper presented results that indicated that the stress due to early age restrained autogenou... more This paper presented results that indicated that the stress due to early age restrained autogenous shrinkage varies quite a lot, partly because of the variation in the relaxation capacity of the mixtures. Both the relaxation ratio, defined as the stress generated divided by the theoretical stress, and the relative relaxation, defined as the absolute value of stress relaxation divided by the average applied stress, can be used to illustrate and analyze the variation of the relaxation phenomena as a function of the type of mixture testes.
MIT Concrete Sustainability Hub, Oregon State University, University of New Brunswick, Jan 8, 2021
Although concrete pavements offer many long-term performance benefits, there are still instances ... more Although concrete pavements offer many long-term performance benefits, there are still instances where premature degradation of pavements leads to unexpected and costly repairs. In addition to being a burden to transportation agencies and the driving public, these situations have the potential to unduly tarnish the reputation of concrete pavements. We assembled a multidisciplinary team across multiple universities whose objective was to improve the durability of concrete pavements by improving the scientific understanding of pavement distresses. In particular, we sought to develop a quantitative understanding of the chemical reactions to the physical manifestation of concrete pavement damage from alkali–silica reaction (ASR) and freeze-thaw (FT). This will lay the foundation for connecting pavement material properties and fracture and durability prediction, while also helping to establish the potential for ASR and/or FT damage in a concrete pavement and the rate at which it would happen. In essence, it will identify the conditions that lead to ASR or FT damage. The research approach involved a range of experiments including nano-scale chemomechanical characterization of ASR gels, mechanical and thermal characterization of cement paste after meso-scale FT cycling, and likelihood of ASR damage for concrete mixtures. The modeling approach included analytical and simulation models of ASR, FT, and fracture at the nano-, meso-, and micro scales. The key outcome of this project is a unified theoretical framework for explaining both ASR and FT damage. Detailed explanations for both mechanisms are as follows. FT: by combining mechanical and characterization experiments together with atomistic and mesoscale simulations, we found that there is NO direct impact of an ice phase in damage to the paste and concrete. FT damage in concrete/cement paste appears to result from a disjoining ionic pressure at the C-S-H/ice interface in the capillary pore network which is that fractures the C-S-H matrix. Computer-simulated effects with the type and concentration of ions in the pore solution agree well with experiments. ASR: by combining mechanical and characterization experiments together with atomistic and mesoscale simulations, we found that the swelling of ASR gel is NOT the reason for damage to concrete. ASR damage is likely the consequence of a Na+ Ca2+ exchange mechanism between an initially formed alkali gel that is deficient in Ca (Ca-poor) and C-S-H. Over time this exchange creates a disjoining ionic pressure at the interface between C-S-H and calcified ASR gel (Ca-rich) in the capillary pore network that causes expansion and cracking within the C-S-H matrix.This research was jointly funded by the Portland Cement Association and the Ready Mixed Concrete Research and Education Foundation
Les betons modernes sont beaucoup plus resistants que leurs precurseurs antiques, parce que l'... more Les betons modernes sont beaucoup plus resistants que leurs precurseurs antiques, parce que l'on comprend mieux les reactions chimiques qui regissent leur comportement
Concrete international, 2014
A great deal of laboratory testing and construction trials have gone into determining whether por... more A great deal of laboratory testing and construction trials have gone into determining whether portland limestone cement (PLC) can achieve equivalent performance in the field. Equivalent performance requires the PLC mixture to have the same constructibility, strength, and durability as portland cement (PC). This article describes three pavement trials where PLC concrete mixtures were compared with PC concrete mixtures, focusing on the condition of the pavements after three to four years in aggressive climates. Results found that PLC can be used as a substitute for PC with no significant impact when PLC is manufactured to have the equivalent strength of PC.
La presente invention a pour objet un procede de traitement pour la fabrication d'une composi... more La presente invention a pour objet un procede de traitement pour la fabrication d'une composition hydraulique a air entraine comprenant au moins un adjuvant et un constituant comprenant des materiaux carbones, le procede comprenant : l'obtention d'une valeur representative de l'adsorption de molecules sonde par les des materiaux carbones; et la fabrication de la composition hydraulique ou le traitement dudit constituant avec une quantite d'adjuvant qui depend de ladite valeur.
La forme du granulat est consideree comme l'un des parametres cles des melanges de betons. Ma... more La forme du granulat est consideree comme l'un des parametres cles des melanges de betons. Malheureusement, la plupart des methodes permettant de determiner ce parametre sont longues et manquent de precision. Dans le but d'ameliorer la vitesse et la precision de la mesure de la forme des granulats, un modele base sur une approche 2D a ete developpe et applique au videogranulometre VDG 40, afin de calculer le coefficient d'aplatissement des granulats. Les parametres du modele ont ete determines a partir d'une importante base de donnees experimentales, comprenant la caracterisation manuelle de la forme des granulats. Ce modele semi empirique a ete valide par une application sur des echantillons preleves dans d'autres carrieres ; les resultats obtenus sont tres satisfaisants. (A). (Voir fiche generale F100684).
In response to growing pressures to reduce the clinker content in cement, the Canadian Standards ... more In response to growing pressures to reduce the clinker content in cement, the Canadian Standards Association (CSA A3001-08) introduced a new classification of cement in 2008, this being Portland Limestone Cement (PLC) containing up to 15% limestone. This paper presents data from laboratory and field studies on the properties of concrete produced with portland limestone cement (PLC) and moderate to high levels of supplementary cementing materials (SCM). The test data indicate that PLC with up to 15% limestone can be manufactured to produce equivalent performance to a portland cement (PC) in terms of concrete strength and other properties, including durability. The equivalent performance is achieved by optimizing the PLC with regards to composition and particle-size distribution, and requires intergrinding rather than blending of the portland cement and limestone. The performance of concrete produced with PLC in combination with a wide range of SCM is also equivalent to that of concre...
Portland limestone cement (PLC) has become increasingly accepted around the world. PLC is able to... more Portland limestone cement (PLC) has become increasingly accepted around the world. PLC is able to be manufactured to have equivalent performance to portland cement (PC) in terms of strength and durability, and, therefore, it can be used as a replacement for PC. However, there have been a few concerns regarding a total transition from PC to PLC due to areas lacking in research. Blends of PC and supplementary cementitious materials (SCMs) have been used to provide resistance to alkali-silica reaction and sulfate attack, but there is little data yet on the performance of PLC and SCM blends. There has been little research on whether PLC concrete is as resistant to cyclic freezing and thawing as PC in situations that are less than ideal, such as when poorly constructed materials lead to increased water content. Research on carbonation has provided ambiguous results. This article presents recent findings in this area that verify PLC's resistance to alkali-silica reaction, sulfate attack, cyclic freezing and thawing, and carbonation.
Carbon Management Technology Conference, 2012
EPA lists Nitrogen Oxides (NO and NO2, together referred to as “NOx”) as one of the six common ai... more EPA lists Nitrogen Oxides (NO and NO2, together referred to as “NOx”) as one of the six common air pollutants. NOx is present in emissions from transportation (cars, trucks, etc.) and also in power plant and other combustion process emissions. The more toxic form, NO2, is recognized to have extensive direct effects on human health (such as asthma and acute respiratory diseases) and also on many other organisms, especially aquatic life forms (due to eutrophication from atmospheric deposition). NOx additionally affects the environment by promoting acid rain and the formation of ground-level ozone, which causes smogs and is harmful to sensitive plant life and ecosystems. The technology used in “smog-eating” (or “de-polluting”) concrete helps mitigate the effect of atmospheric NO2. Contrary to other solutions, this technology does not rely on photo-catalysis and therefore can function perfectly well in the dark. So it is especially suitable for use in confined areas prone to very high N...
Advances in Civil Engineering Materials, 2012
ABSTRACT Calcium sulfate is typically added to cement clinker to prevent flash set and to improve... more ABSTRACT Calcium sulfate is typically added to cement clinker to prevent flash set and to improve early age strength development without causing additional volume instabilities. Recent changes to ASTM C150, “Standard Specification for Portland Cement,” have enabled greater flexibility in determining optimum sulfate levels in Portland cement by not requiring ASTM C563, “Approximation of Optimum SO3 in Hydraulic Cement Using Compressive Strength,” to set sulfate target levels. ASTM C563 requires strength testing using only hydraulic cement at 23°C, which is not always indicative of the optimum sulfate level for field use, because supplementary materials (e.g., fly ash) might be used and the optimum sulfate level might be sensitive to temperature changes. Adding additional sulfate to account for the sulfate demand of fly ashes can enable an improvement in the early age strength for cement–fly ash systems and decrease the number of problems that may be attributed to cement–admixture–fly ash incompatibility, such as abnormal setting and strength gain. This research provides experimental data on the strength development and heat release during early hydration for cement–fly ash systems with different sulfate levels. It is demonstrated that some fly ashes have their own sulfate demand, and when these ashes are used in cement–fly ash blends there is effectively an increase in the optimal sulfate level that should be used for the Portland cement. It is also shown that the optimum sulfate level determined according to the heat of hydration measured with isothermal calorimetry is similar to the optimum sulfate level determined based on compressive strength at 1 day.
Cement and Concrete Research, 2014
ABSTRACT Blended Portland cements containing up to 15% limestone have recently been introduced in... more ABSTRACT Blended Portland cements containing up to 15% limestone have recently been introduced into Canada and the USA. These cements were initially not allowed for use in sulfate environments but this restriction has been lifted in the Canadian cement specification, provided that the “limestone cement” includes sufficient SCM and that it passes a modified version of the CSA A3004-C8 (equivalent to ASTM C1012) test procedure run at a low temperature (5 °C). This new procedure is proposed as a means of predicting the risk of the thaumasite form of sulfate attack in concretes containing limestone cements. The goal of the present study was to better understand how this approach works both in practice and in theory. Results from three different laboratories utilizing the CSA A3004-C8 test procedure are compared and analyzed, while also taking into account the results of thermodynamic modeling and of thaumasite formation experiments conducted in dilute suspensions.
ABSTRACT This article summarizes the results of a study on the shrinkage behavior of an ordinary ... more ABSTRACT This article summarizes the results of a study on the shrinkage behavior of an ordinary portland cement (OPC), a portland-limestone cement (PLC), and a PLC-Slag cement. The results show that the OPC, PLC, and PLC-Slag systems have similar early-age shrinkage, stress development, and cracking behavior, despite the higher fineness of the PLC. Eliminating the largest cement particles during the grinding/separation process used in the production of the PLC allows PLC mixtures to have pore size distributions that are similar to those for OPC mixtures.
Transportation Research Record: Journal of the Transportation Research Board, 2012
Significant efforts have been made to reduce carbon dioxide (CO2) emissions associated with the m... more Significant efforts have been made to reduce carbon dioxide (CO2) emissions associated with the manufacture of portland cement, primarily by making the process more energy efficient and increasing the use of alternative fuels. Further reductions in CO2 can be achieved by lowering the clinker component of the cement because the pyroprocessing used to manufacture clinker produces approximately 1 tonne of CO2 for every tonne of clinker. Traditionally reductions in the clinker content of cement have been achieved by producing blended cement consisting of portland cement combined with a supplementary cementing material (SCM). In Canada, it is now permitted to intergrind up to 15% limestone with cement clinker to produce portland limestone cement or blended portland limestone cement. Recent trials were conducted at the Brookfield cement plant in Nova Scotia to evaluate the performance of a blended cement containing 15% ground, granulated blast furnace slag (an SCM) with that of a blended ...
Construction and Building Materials, 2007
ABSTRACT Aggregate shape is a key parameter that influences mixtures properties. This paper accou... more ABSTRACT Aggregate shape is a key parameter that influences mixtures properties. This paper accounts for a closely controlled experimental program aimed at clarifying the variation of aggregate shape with two parameters, gyratory crusher setting and feed grading. The results show that crusher setting has a significant influence on the flakiness index of produced elementary size fractions, which is not the case for spread size fractions. Moreover, a variation of the proportions of feed fraction constituents has no significant influence on the flakiness index of produced aggregates, whereas a variation of the spreading or size of the feed fraction has. Regarding the shape characteristics of particles, it has been observed that the dimensions of a particle were not related, but flat particles are elongated, and vice versa. Finally, it has been observed that flakiness index varies conversely with the size of produced aggregate.
Cement and Concrete Research, 2002
The influence of temperature on the autogenous shrinkage of cement paste has been studied using t... more The influence of temperature on the autogenous shrinkage of cement paste has been studied using the maturity approach based on Arrhenius' law. Application of this law requires knowledge of the apparent activation energy, E a , of cement. In this work, E a has been determined by the ''setting time method.'' The external volume change of cement paste was measured by hydrostatic weighing. In order to separate the thermal and autogenous deformations, the thermal dilation coefficient (TDC) was determined at both 20 and 30 °C. Investigations have shown that maturity can be used to predict autogenous shrinkage under isothermal and realistic conditions as long as temperatures remain between 10 and 40 °C. Outside of this temperature range, the calculated autogenous deformation and measured isothermal shrinkage are quite different and, as a result, autogenous shrinkage appears to be dependent on more than hydration advancement alone.
Materials and Structures, 2013
Because of its low cost, its ease of use and relative robustness to misuse, its versatility, and ... more Because of its low cost, its ease of use and relative robustness to misuse, its versatility, and its local availability, concrete is by far the most widely used building material in the world today. Intrinsically, concrete has a very low energy and carbon footprint compared to most other materials. However, the volume of Portland cement required for concrete construction makes the cement industry a large emitter of CO 2. The International Energy Agency recently proposed a global CO 2 reduction plan. This plan has three main elements: long term CO 2 targets, a sectorial approach based on the lowest cost to society, and technology roadmaps that demonstrate the means to achieve the CO 2 reductions. For the cement industry, this plan calls for a reduction in CO 2 emissions from 2 Gt in 2007 to 1.55 Gt in 2050, while over the same period cement production is projected to increase by about 50 %. The authors of the cement industry roadmap point out that the extrapolation of existing technologies (fuel efficiency, alternative fuels and biomass, and clinker substitution) will only take us half the way towards these goals. According to the roadmap, the industry will have to rely on costly and unproven carbon capture and storage technologies for the other half of the required reduction. This will result in significant additional costs for society. Most of the CO 2 footprint of cement is due to the decarbonation of limestone during the clinkering process. Designing new clinkers that require less limestone is one means to significantly reduce the CO 2 footprint of cement and concrete. A new class of clinkers described in this paper can reduce CO 2 emissions by 20 to 30 % when compared to the manufacture of traditional PC Clinker. Keywords Cement Á Carbon emissions Á Clinker chemistry 1 Introduction The link between climate change and human activity is no longer in question. As stated by the U.S. Global Change Research Program in its review 1 of the impacts of climate change in the United States [21]: ''Observations show that warming of the climate is unequivocal. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil,
SP-227: Shrinkage and Creep of Concrete, 2005
This paper presented results that indicated that the stress due to early age restrained autogenou... more This paper presented results that indicated that the stress due to early age restrained autogenous shrinkage varies quite a lot, partly because of the variation in the relaxation capacity of the mixtures. Both the relaxation ratio, defined as the stress generated divided by the theoretical stress, and the relative relaxation, defined as the absolute value of stress relaxation divided by the average applied stress, can be used to illustrate and analyze the variation of the relaxation phenomena as a function of the type of mixture testes.
MIT Concrete Sustainability Hub, Oregon State University, University of New Brunswick, Jan 8, 2021
Although concrete pavements offer many long-term performance benefits, there are still instances ... more Although concrete pavements offer many long-term performance benefits, there are still instances where premature degradation of pavements leads to unexpected and costly repairs. In addition to being a burden to transportation agencies and the driving public, these situations have the potential to unduly tarnish the reputation of concrete pavements. We assembled a multidisciplinary team across multiple universities whose objective was to improve the durability of concrete pavements by improving the scientific understanding of pavement distresses. In particular, we sought to develop a quantitative understanding of the chemical reactions to the physical manifestation of concrete pavement damage from alkali–silica reaction (ASR) and freeze-thaw (FT). This will lay the foundation for connecting pavement material properties and fracture and durability prediction, while also helping to establish the potential for ASR and/or FT damage in a concrete pavement and the rate at which it would happen. In essence, it will identify the conditions that lead to ASR or FT damage. The research approach involved a range of experiments including nano-scale chemomechanical characterization of ASR gels, mechanical and thermal characterization of cement paste after meso-scale FT cycling, and likelihood of ASR damage for concrete mixtures. The modeling approach included analytical and simulation models of ASR, FT, and fracture at the nano-, meso-, and micro scales. The key outcome of this project is a unified theoretical framework for explaining both ASR and FT damage. Detailed explanations for both mechanisms are as follows. FT: by combining mechanical and characterization experiments together with atomistic and mesoscale simulations, we found that there is NO direct impact of an ice phase in damage to the paste and concrete. FT damage in concrete/cement paste appears to result from a disjoining ionic pressure at the C-S-H/ice interface in the capillary pore network which is that fractures the C-S-H matrix. Computer-simulated effects with the type and concentration of ions in the pore solution agree well with experiments. ASR: by combining mechanical and characterization experiments together with atomistic and mesoscale simulations, we found that the swelling of ASR gel is NOT the reason for damage to concrete. ASR damage is likely the consequence of a Na+ Ca2+ exchange mechanism between an initially formed alkali gel that is deficient in Ca (Ca-poor) and C-S-H. Over time this exchange creates a disjoining ionic pressure at the interface between C-S-H and calcified ASR gel (Ca-rich) in the capillary pore network that causes expansion and cracking within the C-S-H matrix.This research was jointly funded by the Portland Cement Association and the Ready Mixed Concrete Research and Education Foundation
Les betons modernes sont beaucoup plus resistants que leurs precurseurs antiques, parce que l'... more Les betons modernes sont beaucoup plus resistants que leurs precurseurs antiques, parce que l'on comprend mieux les reactions chimiques qui regissent leur comportement
Concrete international, 2014
A great deal of laboratory testing and construction trials have gone into determining whether por... more A great deal of laboratory testing and construction trials have gone into determining whether portland limestone cement (PLC) can achieve equivalent performance in the field. Equivalent performance requires the PLC mixture to have the same constructibility, strength, and durability as portland cement (PC). This article describes three pavement trials where PLC concrete mixtures were compared with PC concrete mixtures, focusing on the condition of the pavements after three to four years in aggressive climates. Results found that PLC can be used as a substitute for PC with no significant impact when PLC is manufactured to have the equivalent strength of PC.
La presente invention a pour objet un procede de traitement pour la fabrication d'une composi... more La presente invention a pour objet un procede de traitement pour la fabrication d'une composition hydraulique a air entraine comprenant au moins un adjuvant et un constituant comprenant des materiaux carbones, le procede comprenant : l'obtention d'une valeur representative de l'adsorption de molecules sonde par les des materiaux carbones; et la fabrication de la composition hydraulique ou le traitement dudit constituant avec une quantite d'adjuvant qui depend de ladite valeur.
La forme du granulat est consideree comme l'un des parametres cles des melanges de betons. Ma... more La forme du granulat est consideree comme l'un des parametres cles des melanges de betons. Malheureusement, la plupart des methodes permettant de determiner ce parametre sont longues et manquent de precision. Dans le but d'ameliorer la vitesse et la precision de la mesure de la forme des granulats, un modele base sur une approche 2D a ete developpe et applique au videogranulometre VDG 40, afin de calculer le coefficient d'aplatissement des granulats. Les parametres du modele ont ete determines a partir d'une importante base de donnees experimentales, comprenant la caracterisation manuelle de la forme des granulats. Ce modele semi empirique a ete valide par une application sur des echantillons preleves dans d'autres carrieres ; les resultats obtenus sont tres satisfaisants. (A). (Voir fiche generale F100684).
In response to growing pressures to reduce the clinker content in cement, the Canadian Standards ... more In response to growing pressures to reduce the clinker content in cement, the Canadian Standards Association (CSA A3001-08) introduced a new classification of cement in 2008, this being Portland Limestone Cement (PLC) containing up to 15% limestone. This paper presents data from laboratory and field studies on the properties of concrete produced with portland limestone cement (PLC) and moderate to high levels of supplementary cementing materials (SCM). The test data indicate that PLC with up to 15% limestone can be manufactured to produce equivalent performance to a portland cement (PC) in terms of concrete strength and other properties, including durability. The equivalent performance is achieved by optimizing the PLC with regards to composition and particle-size distribution, and requires intergrinding rather than blending of the portland cement and limestone. The performance of concrete produced with PLC in combination with a wide range of SCM is also equivalent to that of concre...
Portland limestone cement (PLC) has become increasingly accepted around the world. PLC is able to... more Portland limestone cement (PLC) has become increasingly accepted around the world. PLC is able to be manufactured to have equivalent performance to portland cement (PC) in terms of strength and durability, and, therefore, it can be used as a replacement for PC. However, there have been a few concerns regarding a total transition from PC to PLC due to areas lacking in research. Blends of PC and supplementary cementitious materials (SCMs) have been used to provide resistance to alkali-silica reaction and sulfate attack, but there is little data yet on the performance of PLC and SCM blends. There has been little research on whether PLC concrete is as resistant to cyclic freezing and thawing as PC in situations that are less than ideal, such as when poorly constructed materials lead to increased water content. Research on carbonation has provided ambiguous results. This article presents recent findings in this area that verify PLC's resistance to alkali-silica reaction, sulfate attack, cyclic freezing and thawing, and carbonation.
Carbon Management Technology Conference, 2012
EPA lists Nitrogen Oxides (NO and NO2, together referred to as “NOx”) as one of the six common ai... more EPA lists Nitrogen Oxides (NO and NO2, together referred to as “NOx”) as one of the six common air pollutants. NOx is present in emissions from transportation (cars, trucks, etc.) and also in power plant and other combustion process emissions. The more toxic form, NO2, is recognized to have extensive direct effects on human health (such as asthma and acute respiratory diseases) and also on many other organisms, especially aquatic life forms (due to eutrophication from atmospheric deposition). NOx additionally affects the environment by promoting acid rain and the formation of ground-level ozone, which causes smogs and is harmful to sensitive plant life and ecosystems. The technology used in “smog-eating” (or “de-polluting”) concrete helps mitigate the effect of atmospheric NO2. Contrary to other solutions, this technology does not rely on photo-catalysis and therefore can function perfectly well in the dark. So it is especially suitable for use in confined areas prone to very high N...
Advances in Civil Engineering Materials, 2012
ABSTRACT Calcium sulfate is typically added to cement clinker to prevent flash set and to improve... more ABSTRACT Calcium sulfate is typically added to cement clinker to prevent flash set and to improve early age strength development without causing additional volume instabilities. Recent changes to ASTM C150, “Standard Specification for Portland Cement,” have enabled greater flexibility in determining optimum sulfate levels in Portland cement by not requiring ASTM C563, “Approximation of Optimum SO3 in Hydraulic Cement Using Compressive Strength,” to set sulfate target levels. ASTM C563 requires strength testing using only hydraulic cement at 23°C, which is not always indicative of the optimum sulfate level for field use, because supplementary materials (e.g., fly ash) might be used and the optimum sulfate level might be sensitive to temperature changes. Adding additional sulfate to account for the sulfate demand of fly ashes can enable an improvement in the early age strength for cement–fly ash systems and decrease the number of problems that may be attributed to cement–admixture–fly ash incompatibility, such as abnormal setting and strength gain. This research provides experimental data on the strength development and heat release during early hydration for cement–fly ash systems with different sulfate levels. It is demonstrated that some fly ashes have their own sulfate demand, and when these ashes are used in cement–fly ash blends there is effectively an increase in the optimal sulfate level that should be used for the Portland cement. It is also shown that the optimum sulfate level determined according to the heat of hydration measured with isothermal calorimetry is similar to the optimum sulfate level determined based on compressive strength at 1 day.
Cement and Concrete Research, 2014
ABSTRACT Blended Portland cements containing up to 15% limestone have recently been introduced in... more ABSTRACT Blended Portland cements containing up to 15% limestone have recently been introduced into Canada and the USA. These cements were initially not allowed for use in sulfate environments but this restriction has been lifted in the Canadian cement specification, provided that the “limestone cement” includes sufficient SCM and that it passes a modified version of the CSA A3004-C8 (equivalent to ASTM C1012) test procedure run at a low temperature (5 °C). This new procedure is proposed as a means of predicting the risk of the thaumasite form of sulfate attack in concretes containing limestone cements. The goal of the present study was to better understand how this approach works both in practice and in theory. Results from three different laboratories utilizing the CSA A3004-C8 test procedure are compared and analyzed, while also taking into account the results of thermodynamic modeling and of thaumasite formation experiments conducted in dilute suspensions.
ABSTRACT This article summarizes the results of a study on the shrinkage behavior of an ordinary ... more ABSTRACT This article summarizes the results of a study on the shrinkage behavior of an ordinary portland cement (OPC), a portland-limestone cement (PLC), and a PLC-Slag cement. The results show that the OPC, PLC, and PLC-Slag systems have similar early-age shrinkage, stress development, and cracking behavior, despite the higher fineness of the PLC. Eliminating the largest cement particles during the grinding/separation process used in the production of the PLC allows PLC mixtures to have pore size distributions that are similar to those for OPC mixtures.
Transportation Research Record: Journal of the Transportation Research Board, 2012
Significant efforts have been made to reduce carbon dioxide (CO2) emissions associated with the m... more Significant efforts have been made to reduce carbon dioxide (CO2) emissions associated with the manufacture of portland cement, primarily by making the process more energy efficient and increasing the use of alternative fuels. Further reductions in CO2 can be achieved by lowering the clinker component of the cement because the pyroprocessing used to manufacture clinker produces approximately 1 tonne of CO2 for every tonne of clinker. Traditionally reductions in the clinker content of cement have been achieved by producing blended cement consisting of portland cement combined with a supplementary cementing material (SCM). In Canada, it is now permitted to intergrind up to 15% limestone with cement clinker to produce portland limestone cement or blended portland limestone cement. Recent trials were conducted at the Brookfield cement plant in Nova Scotia to evaluate the performance of a blended cement containing 15% ground, granulated blast furnace slag (an SCM) with that of a blended ...
Construction and Building Materials, 2007
ABSTRACT Aggregate shape is a key parameter that influences mixtures properties. This paper accou... more ABSTRACT Aggregate shape is a key parameter that influences mixtures properties. This paper accounts for a closely controlled experimental program aimed at clarifying the variation of aggregate shape with two parameters, gyratory crusher setting and feed grading. The results show that crusher setting has a significant influence on the flakiness index of produced elementary size fractions, which is not the case for spread size fractions. Moreover, a variation of the proportions of feed fraction constituents has no significant influence on the flakiness index of produced aggregates, whereas a variation of the spreading or size of the feed fraction has. Regarding the shape characteristics of particles, it has been observed that the dimensions of a particle were not related, but flat particles are elongated, and vice versa. Finally, it has been observed that flakiness index varies conversely with the size of produced aggregate.
Cement and Concrete Research, 2002
The influence of temperature on the autogenous shrinkage of cement paste has been studied using t... more The influence of temperature on the autogenous shrinkage of cement paste has been studied using the maturity approach based on Arrhenius' law. Application of this law requires knowledge of the apparent activation energy, E a , of cement. In this work, E a has been determined by the ''setting time method.'' The external volume change of cement paste was measured by hydrostatic weighing. In order to separate the thermal and autogenous deformations, the thermal dilation coefficient (TDC) was determined at both 20 and 30 °C. Investigations have shown that maturity can be used to predict autogenous shrinkage under isothermal and realistic conditions as long as temperatures remain between 10 and 40 °C. Outside of this temperature range, the calculated autogenous deformation and measured isothermal shrinkage are quite different and, as a result, autogenous shrinkage appears to be dependent on more than hydration advancement alone.
Materials and Structures, 2013
Because of its low cost, its ease of use and relative robustness to misuse, its versatility, and ... more Because of its low cost, its ease of use and relative robustness to misuse, its versatility, and its local availability, concrete is by far the most widely used building material in the world today. Intrinsically, concrete has a very low energy and carbon footprint compared to most other materials. However, the volume of Portland cement required for concrete construction makes the cement industry a large emitter of CO 2. The International Energy Agency recently proposed a global CO 2 reduction plan. This plan has three main elements: long term CO 2 targets, a sectorial approach based on the lowest cost to society, and technology roadmaps that demonstrate the means to achieve the CO 2 reductions. For the cement industry, this plan calls for a reduction in CO 2 emissions from 2 Gt in 2007 to 1.55 Gt in 2050, while over the same period cement production is projected to increase by about 50 %. The authors of the cement industry roadmap point out that the extrapolation of existing technologies (fuel efficiency, alternative fuels and biomass, and clinker substitution) will only take us half the way towards these goals. According to the roadmap, the industry will have to rely on costly and unproven carbon capture and storage technologies for the other half of the required reduction. This will result in significant additional costs for society. Most of the CO 2 footprint of cement is due to the decarbonation of limestone during the clinkering process. Designing new clinkers that require less limestone is one means to significantly reduce the CO 2 footprint of cement and concrete. A new class of clinkers described in this paper can reduce CO 2 emissions by 20 to 30 % when compared to the manufacture of traditional PC Clinker. Keywords Cement Á Carbon emissions Á Clinker chemistry 1 Introduction The link between climate change and human activity is no longer in question. As stated by the U.S. Global Change Research Program in its review 1 of the impacts of climate change in the United States [21]: ''Observations show that warming of the climate is unequivocal. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil,