Transportation Research Record: Journal of the Transportation Research Board
With the increased use of recycled materials and various additives, the performance of asphalt mi... more With the increased use of recycled materials and various additives, the performance of asphalt mixes, especially their cracking resistance, has become a primary concern. Researchers have developed performance test methods and parameters to simulate field performance in the laboratory. When these performance tests are included in specifications, contractors must adjust their mix design parameters accordingly. To aid contractors, this study evaluated rut depths obtained from Hamburg wheel-tracking tests of 261 asphalt mixes and cracking test (CT) index values from IDEAL-CT tests of 69 mixes designed by contractors and verified by the Washington State Department of Transportation. These mixes had different gradations; binder contents; air void contents; recycled asphalt pavement (RAP); recycled asphalt shingles (RAS); recycling agents; binder performance grades; and other volumetric properties. The results show that (1) rut depth is highly sensitive to binder content, performance grade...
Abstract Rock asphalt which is a natural asphalt, along with other modifiers, can be used to impr... more Abstract Rock asphalt which is a natural asphalt, along with other modifiers, can be used to improve the performance of asphalt binder from crude oil. In this research, a systematic study was conducted to investigate the fatigue failure evolution behaviors of rock asphalt composite modified asphalt (RACMA). The fatigue performance of the modified asphalt subjected to rolling thin film oven (RTFO) and pressurized aging vessel (PAV) was explored to determine and assess various fatigue life indices. The applicability of various fatigue life indexes (Nf50, Nfm, Nδ, NR, and Np20) which are determined according to five different fatigue failure criteria were evaluated through statistical analysis and geometric position method. The results indicated that the Nf50 and Nfm in the stress-controlled mode and the Nf50 and NR in the strain-controlled mode of time sweep test exhibited comparable fatigue lives, respectively. The index Nf50 was recommended to estimate the fatigue performance in both stress and strain-controlled modes of time sweep test. Further, it was found that the optimal dosage of rock asphalt (RA) and styrene-butadiene-styrene (SBS) was 5% and 2% respectively in the composite modified asphalt (RA/SBS) in stress-controlled mode, while the content of RA and crumb rubber (CR) in the composite modified asphalt (RA/CR) was 5% and 18% respectively in strain-controlled mode to achieve maximum fatigue lives. The reduction of RA content and the increment of CR content can significantly improve the fatigue resistance of the RA/CR and extend its fatigue life by >5 times. The RACMA generally exhibits good fatigue resistance after RTFO aging.
Studded tire wear leads to severe deterioration of pavement. Therefore, the reduction of studded ... more Studded tire wear leads to severe deterioration of pavement. Therefore, the reduction of studded tire wear is urgently needed to improve asphalt pavement conditions and save repair costs. Steel slag is a co-product of the steel industry and features high hardness, when compared to conventional crushed aggregate, such as granite and limestone. This study evaluates the performance of hot mix asphalt (HMA) that contains steel slag aggregate (SSA) as a surface material to mitigate the studded tire wear. The physical properties of SSA were assessed to determine its suitability in HMA. Four percentages (0%, 20%, 40% and 60%) of SSA were used in asphalt mix, and the mix designs for HMA are conducted in accordance with Superpave mix design. The performance of the mixes was evaluated comprehensively in terms of studded tire wear, dynamic modulus, flow number, fracture properties at intermediate and low temperatures, and Hamburg wheel-tracking device testing. The results indicate that the add...
Oxidative aging can lead to the susceptibility of asphalt pavement to cracking. Most studies on o... more Oxidative aging can lead to the susceptibility of asphalt pavement to cracking. Most studies on oxidative aging of asphalt binders are related to the prediction of the aging properties of asphalt binders based on oxidation kinetics. Development of kinetics models often involves short-term and long-term aging in the laboratory of original binder at different temperatures and for different times, and experiments of original and aged binder. However, for many rehabilitation projects or forensic studies, the original materials of pavements that were constructed years ago are not readily available to develop kinetic models. The development of a kinetic model based on asphalt binder in an in-service pavement is greatly needed to predict the properties of asphalt binder subjected to further aging for the purpose of overlay design, or to backcalculate the original properties of binder before aging for the purpose of forensic studies. This study develops a methodology to develop Arrhenius ki...
AbstractDue to budget constraints, highway agencies tend to use thin lifts as a primary rehabilit... more AbstractDue to budget constraints, highway agencies tend to use thin lifts as a primary rehabilitation strategy. The construction of a thin lift requires a small nominal maximum aggregate size (NMA...
Transportation Research Record: Journal of the Transportation Research Board, 2019
The use of cementitiously stabilized materials (CSM), such as lean concrete, cement-stabilized ag... more The use of cementitiously stabilized materials (CSM), such as lean concrete, cement-stabilized aggregate, and soil stabilized with cement, lime, fly ash, or combinations thereof in the subgrade, sub-base, and base layers of flexible and rigid pavement structures, is a widely accepted practice by many state highway agencies. However, the bottom-up fatigue cracking models of cementitiously stabilized layers (CSL) described in the AASHTO Interim Mechanistic-Empirical Pavement Design Guide Manual of Practice (referred to as the MEPDG) have not been calibrated for CSM based on their field performance. In addition, top-compression fatigue as well as the effects of increases in the modulus and strength values of CSM over time, erosion, and freeze–thaw and wet–dry cycles on the fatigue properties of CSM are not considered in the MPEDG. To address these deficiencies, this research calibrated the bottom-up fatigue model, and developed and calibrated the top-compression fatigue model, with con...
Transportation Research Record: Journal of the Transportation Research Board, 2015
Because the aging of asphalt binders affects nearly all critical aspects of asphalt mixtures, agi... more Because the aging of asphalt binders affects nearly all critical aspects of asphalt mixtures, aging is a fundamentally important factor that affects pavement performance. This study developed a methodology to predict the rheological and damage properties of asphalt binders after they were subjected to aging. Three asphalt binders (one neat and two modified) were aged at four temperatures in a standard atmosphere for different periods. An approximately linear relationship between the carbonyl area and the log of the crossover modulus was found, but the relationship was asphalt specific. It was also found that the inverse of the log crossover modulus could be characterized with the Arrhenius kinetics model. The relationship between the log crossover frequency and log crossover modulus was linear at each aging temperature. The crossover modulus and crossover frequency were used in the Christensen–Anderson model to predict the complex modulus and phase angle master curves of the binders...
AbstractBituminous surface treatments (BSTs), or chip seals, can be placed soon after (e.g., with... more AbstractBituminous surface treatments (BSTs), or chip seals, can be placed soon after (e.g., within 1 year) the underlying asphalt layer is paved, toward the end of the life of the existing asphalt...
Transportation Research Record: Journal of the Transportation Research Board, 2016
Although warm-mix asphalt (WMA) has been used in pavement construction in recent years, the long-... more Although warm-mix asphalt (WMA) has been used in pavement construction in recent years, the long-term field performance of WMA pavements has not been studied extensively. In response, this study investigated 28 pavement projects in the United States, covering different climate zones, WMA technologies, service years, pavement structures, and traffic volume levels. The long-term field rutting performance between WMA pavements and hot-mix asphalt (HMA) pavements was compared. Field samples were extracted for laboratory experiments. Significant determinants (engineering or material properties) that correlate with rutting performance also were investigated. A simple rutting resistance index obtained from the Hamburg wheel-tracking test was found to be the significant determinant (material property) that correlates best with field rutting performance. The significant mix design parameters that affect the rutting resistance index were analyzed to suggest a better rutting-resistant mix desi...
Journal of Performance of Constructed Facilities, 2017
AbstractStone mastic asphalt (SMA) has been used for decades to extend the life of asphalt paveme... more AbstractStone mastic asphalt (SMA) has been used for decades to extend the life of asphalt pavements, especially in terms of rutting resistance. However, its performance and cost-effectiveness have been debated. This study evaluates the long-term performance of an SMA pavement and its control hot-mix asphalt (HMA) pavement in eastern Washington State. The field performance of the SMA pavement and HMA control pavement was evaluated based on the data in a pavement management system and site visits. Field cores were extracted from both the SMA and HMA pavements and subjected to indirect tension (IDT) dynamic modulus tests, creep compliance tests, studded tire wear resistance tests, and intermediate and low temperature IDT fracture tests in the laboratory. SMA and HMA asphalt binders also were extracted, recovered, and subjected to performance grading, multiple stress and creep recovery tests, and monotonic tests. This study found that in the field, the SMA pavement outperformed the HMA pavement in terms of r...
Transportation Research Record: Journal of the Transportation Research Board, 2015
The development of field transverse cracking prediction models is highly complicated because of s... more The development of field transverse cracking prediction models is highly complicated because of several factors, including the difficulty in differentiating thermal cracking from reflective cracking in the field, the high variability of field conditions, and the potential variability in crack initiation and crack propagation mechanisms. As a result, a statistical-based approach is preferred to a mechanical-based prediction model. In this study, statistical methods, partial least squares regression, and binary logistic regression were used to establish prediction models for field transverse cracking. Results indicated that crack initiation and crack propagation were controlled by predictor variables. Material properties (mixture creep compliance, work density, and percentage passing the No. 200 sieve), pavement structure (overlay thickness), climate (low temperature hour), and traffic (average annual daily truck traffic) were found to be key indicators for transverse crack propagatio...
AbstractStudded tire wear can lead to the severe deterioration of asphalt pavement; therefore, th... more AbstractStudded tire wear can lead to the severe deterioration of asphalt pavement; therefore, the reduction of studded tire wear is urgently needed to improve asphalt pavement conditions and save repair costs. Steel slag is a coproduct of the steel industry and features high hardness compared to conventional crushed aggregate, such as granite and limestone. This study evaluated the performance of hot-mix asphalt (HMA) that contains steel slag aggregate (SSA) as a surface material to mitigate studded tire wear. The physical properties of the SSA were assessed to determine its suitability in HMA. Four percentages (0, 20, 40, and 60%) of SSA were used in asphalt mixes, and the mix designs for the HMA were conducted in accordance with Superpave mix design. The performance of the mixes was evaluated comprehensively in terms of studded tire wear resistance, thermal cracking resistance, moisture susceptibility, and rutting. The results indicate that the addition of steel slag increased the mixtures’ studded tir...
Soil water characteristic curve (SWCC) which characterizes the relationship between the degree of... more Soil water characteristic curve (SWCC) which characterizes the relationship between the degree of saturation and suction is an important tool to quantify the mechanical properties of unsaturated soils. The increased use of additives to improve the engineering properties of marginal soils in pavement design has necessitated the need for rapid methods to quantify SWCC. This study used the dewpoint method (WP4) to measure the suction values at various water contents for Class C fly ash stabilized silt and clay soils quickly. The results indicate that significant suction could exist in fly ash stabilized soils and that the suction values are greatly affected by the degree of saturation. The suction and the degree of saturation in stabilized soils will play a significant role in the strength of the stabilized material. The fly ash stabilized material exhibited the hysteretic property on the SWCC. In addition, the data was used to compare the suitability and efficiency of five predictive ...
Transportation Research Record: Journal of the Transportation Research Board, 2015
The phenomenon of top-down cracking in asphalt pavements has drawn increased attention in recent ... more The phenomenon of top-down cracking in asphalt pavements has drawn increased attention in recent years, yet the asphalt pavement field still lacks an effective top-down crack initiation model. Many factors contribute to the initiation and propagation of top-down cracking. This study developed a phenomenological top-down crack initiation model for mechanistic–empirical pavement design. Pavements at FHWA's accelerated loading facility were used to develop a top-down crack initiation model based on the failure strain of asphalt mixtures, as obtained from indirect tensile testing. It was found that the current Mechanistic– Empirical Pavement Design Guide top-down cracking model failed to predict top-down cracking in the wheelpath in the field accurately, whereas the proposed failure strain–based top-down cracking model was effective in predicting top-down cracking in the field. In addition, the Level 2 prediction of failure strain is developed here; it is based on binder failure she...
The large porosity, high water absorption and many inherent micro-cracks in recycled aggregates a... more The large porosity, high water absorption and many inherent micro-cracks in recycled aggregates are the key causes of the weaker mechanical properties, higher drying shrinkage and even vulnerability to early-age cracking in recycled aggregate concrete (RAC). A method of using the polymer aluminium sulfate (PAS) to enhance the mechanical properties and volume stability of RAC is presented. Three basic mechanical properties (compressive strength, flexural strength and elastic modulus) and two volume stability parameters (free drying shrinkage and restrained shrinkage cracking) were evaluated along with a few parallel tests of PAS at the microstructural level. The microstructure of the interfacial transition zone (ITZ) in RAC was characterised by micro-hardness tests and scanning electron microscopy. The test results show that the PAS, due to its chemical function, is capable of effectively increasing the micro-hardness and reducing the inhomogeneity of the ITZ in RAC. These improvemen...
Transportation Research Record: Journal of the Transportation Research Board
With the increased use of recycled materials and various additives, the performance of asphalt mi... more With the increased use of recycled materials and various additives, the performance of asphalt mixes, especially their cracking resistance, has become a primary concern. Researchers have developed performance test methods and parameters to simulate field performance in the laboratory. When these performance tests are included in specifications, contractors must adjust their mix design parameters accordingly. To aid contractors, this study evaluated rut depths obtained from Hamburg wheel-tracking tests of 261 asphalt mixes and cracking test (CT) index values from IDEAL-CT tests of 69 mixes designed by contractors and verified by the Washington State Department of Transportation. These mixes had different gradations; binder contents; air void contents; recycled asphalt pavement (RAP); recycled asphalt shingles (RAS); recycling agents; binder performance grades; and other volumetric properties. The results show that (1) rut depth is highly sensitive to binder content, performance grade...
Abstract Rock asphalt which is a natural asphalt, along with other modifiers, can be used to impr... more Abstract Rock asphalt which is a natural asphalt, along with other modifiers, can be used to improve the performance of asphalt binder from crude oil. In this research, a systematic study was conducted to investigate the fatigue failure evolution behaviors of rock asphalt composite modified asphalt (RACMA). The fatigue performance of the modified asphalt subjected to rolling thin film oven (RTFO) and pressurized aging vessel (PAV) was explored to determine and assess various fatigue life indices. The applicability of various fatigue life indexes (Nf50, Nfm, Nδ, NR, and Np20) which are determined according to five different fatigue failure criteria were evaluated through statistical analysis and geometric position method. The results indicated that the Nf50 and Nfm in the stress-controlled mode and the Nf50 and NR in the strain-controlled mode of time sweep test exhibited comparable fatigue lives, respectively. The index Nf50 was recommended to estimate the fatigue performance in both stress and strain-controlled modes of time sweep test. Further, it was found that the optimal dosage of rock asphalt (RA) and styrene-butadiene-styrene (SBS) was 5% and 2% respectively in the composite modified asphalt (RA/SBS) in stress-controlled mode, while the content of RA and crumb rubber (CR) in the composite modified asphalt (RA/CR) was 5% and 18% respectively in strain-controlled mode to achieve maximum fatigue lives. The reduction of RA content and the increment of CR content can significantly improve the fatigue resistance of the RA/CR and extend its fatigue life by >5 times. The RACMA generally exhibits good fatigue resistance after RTFO aging.
Studded tire wear leads to severe deterioration of pavement. Therefore, the reduction of studded ... more Studded tire wear leads to severe deterioration of pavement. Therefore, the reduction of studded tire wear is urgently needed to improve asphalt pavement conditions and save repair costs. Steel slag is a co-product of the steel industry and features high hardness, when compared to conventional crushed aggregate, such as granite and limestone. This study evaluates the performance of hot mix asphalt (HMA) that contains steel slag aggregate (SSA) as a surface material to mitigate the studded tire wear. The physical properties of SSA were assessed to determine its suitability in HMA. Four percentages (0%, 20%, 40% and 60%) of SSA were used in asphalt mix, and the mix designs for HMA are conducted in accordance with Superpave mix design. The performance of the mixes was evaluated comprehensively in terms of studded tire wear, dynamic modulus, flow number, fracture properties at intermediate and low temperatures, and Hamburg wheel-tracking device testing. The results indicate that the add...
Oxidative aging can lead to the susceptibility of asphalt pavement to cracking. Most studies on o... more Oxidative aging can lead to the susceptibility of asphalt pavement to cracking. Most studies on oxidative aging of asphalt binders are related to the prediction of the aging properties of asphalt binders based on oxidation kinetics. Development of kinetics models often involves short-term and long-term aging in the laboratory of original binder at different temperatures and for different times, and experiments of original and aged binder. However, for many rehabilitation projects or forensic studies, the original materials of pavements that were constructed years ago are not readily available to develop kinetic models. The development of a kinetic model based on asphalt binder in an in-service pavement is greatly needed to predict the properties of asphalt binder subjected to further aging for the purpose of overlay design, or to backcalculate the original properties of binder before aging for the purpose of forensic studies. This study develops a methodology to develop Arrhenius ki...
AbstractDue to budget constraints, highway agencies tend to use thin lifts as a primary rehabilit... more AbstractDue to budget constraints, highway agencies tend to use thin lifts as a primary rehabilitation strategy. The construction of a thin lift requires a small nominal maximum aggregate size (NMA...
Transportation Research Record: Journal of the Transportation Research Board, 2019
The use of cementitiously stabilized materials (CSM), such as lean concrete, cement-stabilized ag... more The use of cementitiously stabilized materials (CSM), such as lean concrete, cement-stabilized aggregate, and soil stabilized with cement, lime, fly ash, or combinations thereof in the subgrade, sub-base, and base layers of flexible and rigid pavement structures, is a widely accepted practice by many state highway agencies. However, the bottom-up fatigue cracking models of cementitiously stabilized layers (CSL) described in the AASHTO Interim Mechanistic-Empirical Pavement Design Guide Manual of Practice (referred to as the MEPDG) have not been calibrated for CSM based on their field performance. In addition, top-compression fatigue as well as the effects of increases in the modulus and strength values of CSM over time, erosion, and freeze–thaw and wet–dry cycles on the fatigue properties of CSM are not considered in the MPEDG. To address these deficiencies, this research calibrated the bottom-up fatigue model, and developed and calibrated the top-compression fatigue model, with con...
Transportation Research Record: Journal of the Transportation Research Board, 2015
Because the aging of asphalt binders affects nearly all critical aspects of asphalt mixtures, agi... more Because the aging of asphalt binders affects nearly all critical aspects of asphalt mixtures, aging is a fundamentally important factor that affects pavement performance. This study developed a methodology to predict the rheological and damage properties of asphalt binders after they were subjected to aging. Three asphalt binders (one neat and two modified) were aged at four temperatures in a standard atmosphere for different periods. An approximately linear relationship between the carbonyl area and the log of the crossover modulus was found, but the relationship was asphalt specific. It was also found that the inverse of the log crossover modulus could be characterized with the Arrhenius kinetics model. The relationship between the log crossover frequency and log crossover modulus was linear at each aging temperature. The crossover modulus and crossover frequency were used in the Christensen–Anderson model to predict the complex modulus and phase angle master curves of the binders...
AbstractBituminous surface treatments (BSTs), or chip seals, can be placed soon after (e.g., with... more AbstractBituminous surface treatments (BSTs), or chip seals, can be placed soon after (e.g., within 1 year) the underlying asphalt layer is paved, toward the end of the life of the existing asphalt...
Transportation Research Record: Journal of the Transportation Research Board, 2016
Although warm-mix asphalt (WMA) has been used in pavement construction in recent years, the long-... more Although warm-mix asphalt (WMA) has been used in pavement construction in recent years, the long-term field performance of WMA pavements has not been studied extensively. In response, this study investigated 28 pavement projects in the United States, covering different climate zones, WMA technologies, service years, pavement structures, and traffic volume levels. The long-term field rutting performance between WMA pavements and hot-mix asphalt (HMA) pavements was compared. Field samples were extracted for laboratory experiments. Significant determinants (engineering or material properties) that correlate with rutting performance also were investigated. A simple rutting resistance index obtained from the Hamburg wheel-tracking test was found to be the significant determinant (material property) that correlates best with field rutting performance. The significant mix design parameters that affect the rutting resistance index were analyzed to suggest a better rutting-resistant mix desi...
Journal of Performance of Constructed Facilities, 2017
AbstractStone mastic asphalt (SMA) has been used for decades to extend the life of asphalt paveme... more AbstractStone mastic asphalt (SMA) has been used for decades to extend the life of asphalt pavements, especially in terms of rutting resistance. However, its performance and cost-effectiveness have been debated. This study evaluates the long-term performance of an SMA pavement and its control hot-mix asphalt (HMA) pavement in eastern Washington State. The field performance of the SMA pavement and HMA control pavement was evaluated based on the data in a pavement management system and site visits. Field cores were extracted from both the SMA and HMA pavements and subjected to indirect tension (IDT) dynamic modulus tests, creep compliance tests, studded tire wear resistance tests, and intermediate and low temperature IDT fracture tests in the laboratory. SMA and HMA asphalt binders also were extracted, recovered, and subjected to performance grading, multiple stress and creep recovery tests, and monotonic tests. This study found that in the field, the SMA pavement outperformed the HMA pavement in terms of r...
Transportation Research Record: Journal of the Transportation Research Board, 2015
The development of field transverse cracking prediction models is highly complicated because of s... more The development of field transverse cracking prediction models is highly complicated because of several factors, including the difficulty in differentiating thermal cracking from reflective cracking in the field, the high variability of field conditions, and the potential variability in crack initiation and crack propagation mechanisms. As a result, a statistical-based approach is preferred to a mechanical-based prediction model. In this study, statistical methods, partial least squares regression, and binary logistic regression were used to establish prediction models for field transverse cracking. Results indicated that crack initiation and crack propagation were controlled by predictor variables. Material properties (mixture creep compliance, work density, and percentage passing the No. 200 sieve), pavement structure (overlay thickness), climate (low temperature hour), and traffic (average annual daily truck traffic) were found to be key indicators for transverse crack propagatio...
AbstractStudded tire wear can lead to the severe deterioration of asphalt pavement; therefore, th... more AbstractStudded tire wear can lead to the severe deterioration of asphalt pavement; therefore, the reduction of studded tire wear is urgently needed to improve asphalt pavement conditions and save repair costs. Steel slag is a coproduct of the steel industry and features high hardness compared to conventional crushed aggregate, such as granite and limestone. This study evaluated the performance of hot-mix asphalt (HMA) that contains steel slag aggregate (SSA) as a surface material to mitigate studded tire wear. The physical properties of the SSA were assessed to determine its suitability in HMA. Four percentages (0, 20, 40, and 60%) of SSA were used in asphalt mixes, and the mix designs for the HMA were conducted in accordance with Superpave mix design. The performance of the mixes was evaluated comprehensively in terms of studded tire wear resistance, thermal cracking resistance, moisture susceptibility, and rutting. The results indicate that the addition of steel slag increased the mixtures’ studded tir...
Soil water characteristic curve (SWCC) which characterizes the relationship between the degree of... more Soil water characteristic curve (SWCC) which characterizes the relationship between the degree of saturation and suction is an important tool to quantify the mechanical properties of unsaturated soils. The increased use of additives to improve the engineering properties of marginal soils in pavement design has necessitated the need for rapid methods to quantify SWCC. This study used the dewpoint method (WP4) to measure the suction values at various water contents for Class C fly ash stabilized silt and clay soils quickly. The results indicate that significant suction could exist in fly ash stabilized soils and that the suction values are greatly affected by the degree of saturation. The suction and the degree of saturation in stabilized soils will play a significant role in the strength of the stabilized material. The fly ash stabilized material exhibited the hysteretic property on the SWCC. In addition, the data was used to compare the suitability and efficiency of five predictive ...
Transportation Research Record: Journal of the Transportation Research Board, 2015
The phenomenon of top-down cracking in asphalt pavements has drawn increased attention in recent ... more The phenomenon of top-down cracking in asphalt pavements has drawn increased attention in recent years, yet the asphalt pavement field still lacks an effective top-down crack initiation model. Many factors contribute to the initiation and propagation of top-down cracking. This study developed a phenomenological top-down crack initiation model for mechanistic–empirical pavement design. Pavements at FHWA's accelerated loading facility were used to develop a top-down crack initiation model based on the failure strain of asphalt mixtures, as obtained from indirect tensile testing. It was found that the current Mechanistic– Empirical Pavement Design Guide top-down cracking model failed to predict top-down cracking in the wheelpath in the field accurately, whereas the proposed failure strain–based top-down cracking model was effective in predicting top-down cracking in the field. In addition, the Level 2 prediction of failure strain is developed here; it is based on binder failure she...
The large porosity, high water absorption and many inherent micro-cracks in recycled aggregates a... more The large porosity, high water absorption and many inherent micro-cracks in recycled aggregates are the key causes of the weaker mechanical properties, higher drying shrinkage and even vulnerability to early-age cracking in recycled aggregate concrete (RAC). A method of using the polymer aluminium sulfate (PAS) to enhance the mechanical properties and volume stability of RAC is presented. Three basic mechanical properties (compressive strength, flexural strength and elastic modulus) and two volume stability parameters (free drying shrinkage and restrained shrinkage cracking) were evaluated along with a few parallel tests of PAS at the microstructural level. The microstructure of the interfacial transition zone (ITZ) in RAC was characterised by micro-hardness tests and scanning electron microscopy. The test results show that the PAS, due to its chemical function, is capable of effectively increasing the micro-hardness and reducing the inhomogeneity of the ITZ in RAC. These improvemen...
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