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Sulapha Peethamparan - One of the best experts on this subject based on the ideXlab platform.
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On drying shrinkage in alkali-activated Concrete: Improving dimensional stability by aging or heat-curing
Cement and Concrete Research, 2017Co-Authors: Robert J. Thomas, Diego Lezama, Sulapha PeethamparanAbstract:Abstract The problem of excessive drying shrinkage in alkali-activated Concrete (AAC) is well-documented in the literature. The magnitude of drying shrinkage is often three or more times that in Portland Cement Concrete. This study investigates the effects of binder type, activator concentration, strength, age, and curing method on the manifestation of drying shrinkage in alkali-activated fly ash and slag Cement Concrete. Early-age shrinkage strains in excess of 1200 μe (0.12 percent strain) are observed in AAC. This is attributed to delayed hydration, microstructure refinement, and strength development. The resulting damage is far more significant than in Portland Cement Concrete. Shrinkage and resulting damage are greatly reduced when specimens are dried at later age and after heat-curing. Alkali-activated slag Cement Concrete is more sensitive to water loss than Portland Cement or alkali-activated fly ash Concrete. This results from a finer pore structure in alkali-activated slag binders.
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alkali activated Concrete engineering properties and stress strain behavior
Construction and Building Materials, 2015Co-Authors: Robert J. Thomas, Sulapha PeethamparanAbstract:Abstract This paper presents an investigation into the tensile strength, modulus of elasticity, Poisson’s ratio, and stress–strain relationships of alkali-activated Portland-Cement-free Concrete made with fly ash or ground granulated blast furnace slag (GGBFS) as the sole binder. Alkali-activated Concrete is shown to be stronger in tension and have lower Poisson’s ratio than Portland Cement Concrete. Relationships are proposed to estimate the tensile strength and modulus of elasticity based on the compressive strength of alkali-activated Concrete, which are of the same form as those currently employed for Portland Cement Concrete.
Baoshan Huang - One of the best experts on this subject based on the ideXlab platform.
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recycling of waste tire rubber in asphalt and Portland Cement Concrete an overview
Construction and Building Materials, 2014Co-Authors: Xiang Shu, Baoshan HuangAbstract:Abstract Waste tires pose significant health and environmental concerns if not recycled and/or discarded properly. Over the years, recycling waste tires into civil engineering applications, especially into asphalt paving mixtures and Portland Cement Concrete, has been gaining more and more interests. This review summarizes the recent advances in the use of waste tire rubber in asphalt and Portland Cement Concrete. The use of crumb rubber in asphalt paving mixture has long been proven successful due to good compatibility and interaction between rubber particles and asphalt binder, leading to various improved properties and performance of asphalt mixtures. The rubberized asphalt mixtures also have shown good compatibility with two widely used sustainability technologies in asphalt paving industry – reclaimed asphalt pavement (RAP) and warm-mix asphalt (WMA). In comparison with its use in asphalt paving mixtures, recycling of waste rubber in Portland Cement Concrete has not been so successful due to two factors: (1) incompatibility in chemical property between rubber and Cement paste and (2) the significant difference in stiffness resulting in stress concentrations. Various methods have been proposed to overcome the barriers to improve the performance of rubberized Portland Cement Concrete, some of which have shown to be promising.
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chemical mechanical and durability properties of Concrete with local mineral admixtures under sulfate environment in northwest china
Materials, 2014Co-Authors: Changjun Zhou, Qiang He, Baoshan HuangAbstract:Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes Portland Cement Concrete. Rapid industrialization in the region has been generating huge amounts of mineral admixtures, such as fly ash and slags from energy and metallurgical industries. These industrial by-products would turn into waste materials if not utilized in time. The present study evaluated the suitability of utilizing local mineral admixtures in significant quantities for producing quality Concrete mixtures that can withstand the harsh chemical environment without compromising the essential mechanical properties. Comprehensive chemical, mechanical, and durability tests were conducted in the laboratory to characterize the properties of the local Cementitious mineral admixtures, Cement mortar and Portland Cement Concrete mixtures containing these admixtures. The results from this study indicated that the sulfate resistance of Concrete was effectively improved by adding local class F fly ash and slag, or by applying sulfate resistance Cement to the mixtures. It is noteworthy that Concrete containing local mineral admixtures exhibited much lower permeability (in terms of chloride ion penetration) than ordinary Portland Cement Concrete while retaining the same mechanical properties; whereas Concrete mixtures made with sulfate resistance Cement had significantly reduced strength and much increased chloride penetration comparing to the other mixtures. Hence, the use of local mineral admixtures in Northwest China in Concrete mixtures would be beneficial to the performance of Concrete, as well as to the protection of environment.
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laboratory investigation of Portland Cement Concrete containing recycled asphalt pavements
Cement and Concrete Research, 2005Co-Authors: Baoshan Huang, Xiang Shu, Guoqiang LiAbstract:Recycled asphalt pavement (RAP) is the removed and/or reprocessed pavement material containing asphalt and aggregate. The use of RAP in asphalt pavement has become a common practice in the construction of new, and reconstruction of old, hot mix asphalt (HMA) pavements. But little research has been done to examine the potential of incorporating RAP into Concrete. Since RAP contains asphalt, it is very likely that the toughness of Concrete made with RAP could be improved. In the present study, the mechanical properties of RAP-incorporated Portland Cement Concrete were investigated through laboratory experiments. Two types of RAP (coarse and fine RAP) materials were considered. The results from this study indicated that RAP could be incorporated into Portland Cement Concrete without any modification to the conventional equipment or procedures. Without any treatment, there was a systematic reduction in the compressive and split tensile strengths with the incorporation RAP in Concrete. Notably, the energy absorbing toughness for the RAP incorporated Concrete has been significantly improved.
Robert J. Thomas - One of the best experts on this subject based on the ideXlab platform.
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On drying shrinkage in alkali-activated Concrete: Improving dimensional stability by aging or heat-curing
Cement and Concrete Research, 2017Co-Authors: Robert J. Thomas, Diego Lezama, Sulapha PeethamparanAbstract:Abstract The problem of excessive drying shrinkage in alkali-activated Concrete (AAC) is well-documented in the literature. The magnitude of drying shrinkage is often three or more times that in Portland Cement Concrete. This study investigates the effects of binder type, activator concentration, strength, age, and curing method on the manifestation of drying shrinkage in alkali-activated fly ash and slag Cement Concrete. Early-age shrinkage strains in excess of 1200 μe (0.12 percent strain) are observed in AAC. This is attributed to delayed hydration, microstructure refinement, and strength development. The resulting damage is far more significant than in Portland Cement Concrete. Shrinkage and resulting damage are greatly reduced when specimens are dried at later age and after heat-curing. Alkali-activated slag Cement Concrete is more sensitive to water loss than Portland Cement or alkali-activated fly ash Concrete. This results from a finer pore structure in alkali-activated slag binders.
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alkali activated Concrete engineering properties and stress strain behavior
Construction and Building Materials, 2015Co-Authors: Robert J. Thomas, Sulapha PeethamparanAbstract:Abstract This paper presents an investigation into the tensile strength, modulus of elasticity, Poisson’s ratio, and stress–strain relationships of alkali-activated Portland-Cement-free Concrete made with fly ash or ground granulated blast furnace slag (GGBFS) as the sole binder. Alkali-activated Concrete is shown to be stronger in tension and have lower Poisson’s ratio than Portland Cement Concrete. Relationships are proposed to estimate the tensile strength and modulus of elasticity based on the compressive strength of alkali-activated Concrete, which are of the same form as those currently employed for Portland Cement Concrete.
Shima Pilehvar - One of the best experts on this subject based on the ideXlab platform.
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effect of freeze thaw cycles on the mechanical behavior of geopolymer Concrete and Portland Cement Concrete containing micro encapsulated phase change materials
Construction and Building Materials, 2019Co-Authors: Shima Pilehvar, Anna M Szczotok, Luca Valentini, Ramon Pamies, Juan F Rodriguez, Marcos Lanzon, Annalena KjoniksenAbstract:Abstract The effect of frost conditions on the physical and mechanical properties of geopolymer Concrete (GPC) and Portland Cement Concrete (PCC) containing two different micro-encapsulated phase change materials (MPCM) was examined. Microstructural studies revealed that the freeze-thaw induced Concrete deterioration can be contributed to microcracks appearing at the weak interfacial transition zones between paste/aggregate and paste/MPCM. The addition of MPCM provided an excellent resistance against freeze-thaw cycles with minor reduction of the compressive strength, unlike the samples without MPCM where a stronger reduction was observed. When the temperature was reduced to 0 °C, the initial setting time of Portland Cement pastes became longer due to the low temperature and the high viscosity. For geopolymer pastes, the initial setting time became shorter due to phase separation of the alkaline solution at low temperatures. Increasing the MPCM concentration reduced the final setting time for both Portland Cement and geopolymer pastes.
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mechanical properties and microscale changes of geopolymer Concrete and Portland Cement Concrete containing micro encapsulated phase change materials
Cement and Concrete Research, 2017Co-Authors: Shima Pilehvar, Vinh Duy Cao, Anna M Szczotok, Luca Valentini, Davide Salvioni, Matteo Magistri, Ramon Pamies, Annalena KjoniksenAbstract:Abstract The effect of micro-encapsulated phase change materials (MPCM) in solid and liquid states on the mechanical properties and microstructure of geopolymer and Portland Cement Concretes is investigated. Geopolymer Concrete (GPC) and Portland Cement Concrete (PCC) containing different amounts of MPCM were prepared and cured at both 20 °C and 40 °C. The results revealed that the compressive strength of both GPC and PCC decreases with the addition of MPCM. Whether the PCM is in solid (20 °C) or liquid (40 °C) state did not significantly affect the mechanical properties of GPC, while melting the PCM was found to reduce the strength of PCC. X-ray tomography imaging was utilized to examine the effect of MPCM on the porosity of the samples. SEM imaging reveals that air gaps are formed between the microcapsules and the surrounding Concrete matrix.
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microencapsulated phase change materials for enhancing the thermal performance of Portland Cement Concrete and geopolymer Concrete for passive building applications
Energy Conversion and Management, 2017Co-Authors: Shima Pilehvar, Vinh Duy Cao, Anna M Szczotok, Juan F Rodriguez, Carlos Salasbringas, Manuel Carmona, Nodar AlmanasirAbstract:Abstract Concretes with a high thermal energy storage capacity were fabricated by mixing microencapsulated phase change materials (MPCM) into Portland Cement Concrete (PCC) and geopolymer Concrete (GPC). The effect of MPCM on thermal performance and compressive strength of PCC and GPC were investigated. It was found that the replaCement of sand by MPCM resulted in lower thermal conductivity and higher thermal energy storage, while the specific heat capacity of Concrete remained practically stable when the phase change material (PCM) was in the liquid or solid phase. Furthermore, the thermal conductivity of GPC as function of MPCM concentration was reduced at a higher rate than that of PCC. The power consumption needed to stabilize a simulated indoor temperature of 23 °C was reduced after the addition of MPCM. GPC exhibited better energy saving properties than PCC at the same conditions. A significant loss in compressive strength was observed due to the addition of MPCM to Concrete. However, the compressive strength still satisfies the mechanical European regulation (EN 206-1, compressive strength class C20/25) for Concrete applications. Finally, MPCM-Concrete provided a good thermal stability after subjecting the samples to 100 thermal cycles at high heating/cooling rates.
Xiju Shi - One of the best experts on this subject based on the ideXlab platform.
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punchout study for continuously reinforced Concrete pavement containing reclaimed asphalt pavement using pavement me models
International Journal of Pavement Engineering, 2020Co-Authors: Xiju Shi, Da G Zollinge, Anol MukhopadhyayAbstract:The restricted use of reclaimed asphalt pavement (RAP) in hot mix asphalt (HMA) motivates the use of RAP in Portland Cement Concrete (PCC) as an aggregate replaCement. The addition of RAP causes si...
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characterization of two parameter fracture properties of Portland Cement Concrete containing reclaimed asphalt pavement aggregates by semicircular bending specimens
Cement & Concrete Composites, 2019Co-Authors: Xiju Shi, Anol Mukhopadhyay, M M Mirsaya, Da G ZollingeAbstract:Abstract Although few available test results showed that Portland Cement Concrete containing reclaimed asphalt pavement (RAP-PCC) can have equivalent (or even improved) fracture properties and ductility compared to plain PCC, the limitations of the existing experimental methods to test the two-parameter fracture properties (TPFP) of Concrete (critical stress intensity factor, K Ic s , and critical crack tip opening displaCement, CTOD c ) have hindered an effective characterization of RAP-PCC's fracture properties and ductility. To provide an easy but effective approach, this paper developed an innovative fracture test using the semicircular bending (SCB) geometry to characterize the TPFP of the studied RAP-PCC mixtures. Based on the results, it is confirmed that addition of RAP improves PCC's CTOD c and G f , despite of a reduction in mechanical strengths. The material length, Q , of the RAP-PCC mixture is statistically higher than that of the plain PCC, suggesting that RAP-PCC is a more ductile material. Besides, the theoretical tensile strength, tensile MOE, and bilinear softening curve of the RAP-PCC can be easily obtained using the developed SCB fracture test.
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sustainability assessment for Portland Cement Concrete pavement containing reclaimed asphalt pavement aggregates
Journal of Cleaner Production, 2018Co-Authors: Xiju Shi, Anol Mukhopadhyay, Da G ZollingeAbstract:Abstract The lack of quantitative sustainability assessments of use of reclaimed asphalt pavement (RAP) in Portland Cement Concrete (PCC) as an aggregate replaCement for pavement applications has impeded the field application of pavements built with PCC containing RAP (RAP-PCC). This paper presents a life cycle inventory analysis in order to fill the gap of research and encourage a wider use of PCC made with RAP aggregates as paving materials. Three different types of pavements, namely a single-lift pavement made of plain PCC slab, a single-lift pavement made of RAP-PCC slab, and a two-lift Concrete pavement using RAP-PCC as the bottom lift material, were designed, followed by an extensive sustainability assessment via the economic input-out life cycle assessment (EIO-LCA) approach. Based on the EIO-LCA results, the economic, social, and environmental benefits of utilization of RAP-PCC for pavement applications were clearly demonstrated. Among all three studied pavements in this case study, the single-lift RAP-PCC pavement could yield the highest economic benefits, while the two-lift construction using RAP-PCC in the bottom lift could have the highest positive impacts from social and environmental perspective.
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mix design formulation and evaluation of Portland Cement Concrete paving mixtures containing reclaimed asphalt pavement
Construction and Building Materials, 2017Co-Authors: Xiju Shi, Anol Mukhopadhyay, Kaiwei LiuAbstract:Abstract One potential solution to reduce the amounts of extra reclaimed asphalt pavement (RAP) stockpiles is to use RAP as an aggregate replaCement in Portland Cement Concrete (PCC). This study investigated whether partial replaCement of virgin coarse aggregate by coarse RAP is a practically viable option to formulate PCC paving mixtures. The results showed that replacing virgin coarse aggregate by coarse RAP with sufficient intermediate size particles offers the benefits of achieving dense combined aggregate gradation. Measuring relevant mechanical properties followed by developing a procedure to determine optimum RAP replaCement levels and guidelines and recommendations for designing PCC containing RAP were conducted and presented in this paper.