The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Asad Hanif - One of the best experts on this subject based on the ideXlab platform.
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Steam-cured recycled aggregate concrete incorporating moderately high early strength cement: effect of binder content and Curing conditions
SN Applied Sciences, 2019Co-Authors: Yongjae Kim, Wonjun Park, Asad HanifAbstract:Steam Curing employed for faster strength gain due to higher hydration rate may lead to shrinkage issues, and hence the use of moderately high early strength cement (MESC) is proposed instead of typically used high early strength cement (HESC) which has a high C3S content. This paper evaluates the suitability of MESC for use in precast concrete. The objective was to (i) determine the feasibility of MESC in recycled aggregate concrete (RAC), (ii) determine the optimum Steam Curing conditions (Curing duration, maximum temperature, and duration of holding maximum temperature), and (iii) evaluating the beneficial use of reduced binder content to compensate for Steam Curing. Four series of RAC were developed which were subjected to nine different Steam Curing condition, and the resulting strength properties were determined. Though all the developed concrete specimens achieved the design strength of 30 MPa, those cured at 50 °C with 1 h duration of exposure to maximum temperature exhibited the best performance. Further, it was found that even though reducing the binder content reduces the ultimate strength at 28-day age, Curing at 70 °C with 2 h exposure to maximum temperature duration (for 7% reduction in binder volume) leads to merely 11.8% strength decline. It is concluded that MESC can be effectively used in Steam cured RAC instead of OPC and HESC with meagre strength loss when cured at maximum temperature of 50 °C maintained for 1 h while the total Curing time being 4.5 h. Thus, utilizing MESC in RAC shall not only help combat the persistently declining natural resources but also reduced the associated carbon dioxide emissions, thereby promoting sustainable development.
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optimization of Steam Curing regime for recycled aggregate concrete incorporating high early strength cement a parametric study
Materials, 2018Co-Authors: Asad Hanif, Muhammad Usman, Cheolwoo ParkAbstract:This paper investigates the properties of Steam cured recycled aggregate concrete (RAC), in an attempt to determine the optimum conditions of the Steam-Curing cycle for RAC, and incorporating high early strength cement (HESC). Varying conditions of Steam Curing were employed. The Steam-Curing cycle was set based on the peak temperature, and the duration for which the peak temperature was maintained. Three peak temperatures were used for Steam Curing, 50 °C, 60 °C, and 70 °C, maintained for up to two hours. The compressive strength results indicated that the Steam-Curing cycle employing the peak temperature of 50 °C maintained for one hour with a total duration of four hours was the optimum for strength development, both at the early and late stages of hydration. Determining the optimum Steam-Curing temperature and duration will help reduce the associated Curing cost, thus further economizing the production cost of recycled aggregate concrete.
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early age behavior of recycled aggregate concrete under Steam Curing regime
Journal of Cleaner Production, 2017Co-Authors: Asad Hanif, Zeyu Lu, Cheolwoo ParkAbstract:Abstract This study addresses the effects of accelerated hydration in recycled aggregate concrete (RAC) due to the incorporation of High Early Strength Cement (HESC) and employing the Steam Curing method. The RAC was formulated by the complete replacement of natural aggregates with recycled aggregates. The resulting compressive strength, elastic modulus, and shrinkage strain results at early-ages were assessed and compared with concretes incorporating natural aggregates and ordinary Portland cement (OPC). By employing Steam Curing with HESC as binder, 70% of the design strength could be achieved in one day, however for the contemporary concretes with OPC as binder, the 1-day strength was about 60% of design strength. With HESC as binder, the change in mechanical properties was found to be minimal after 48 h of casting whereas such change was observed at 72 h age for OPC containing concretes. Utilizing recycled aggregates led to a lower net shrinkage strain indicating improvement against early-age cracking. The cost-benefit analysis showed that for accelerated hydration in concrete, utilizing recycled aggregates leads to lower associated CO 2 emissions at reduced cost. Replacing OPC with HESC improves the resulting early – age properties, but the production cost also increases. The study suggests RAC and HESC are beneficial for concrete elements with larger surface area to depth ratio, like road pavements, floorings, reinforced concrete slabs, and precast elements.
Cheolwoo Park - One of the best experts on this subject based on the ideXlab platform.
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optimization of Steam Curing regime for recycled aggregate concrete incorporating high early strength cement a parametric study
Materials, 2018Co-Authors: Asad Hanif, Muhammad Usman, Cheolwoo ParkAbstract:This paper investigates the properties of Steam cured recycled aggregate concrete (RAC), in an attempt to determine the optimum conditions of the Steam-Curing cycle for RAC, and incorporating high early strength cement (HESC). Varying conditions of Steam Curing were employed. The Steam-Curing cycle was set based on the peak temperature, and the duration for which the peak temperature was maintained. Three peak temperatures were used for Steam Curing, 50 °C, 60 °C, and 70 °C, maintained for up to two hours. The compressive strength results indicated that the Steam-Curing cycle employing the peak temperature of 50 °C maintained for one hour with a total duration of four hours was the optimum for strength development, both at the early and late stages of hydration. Determining the optimum Steam-Curing temperature and duration will help reduce the associated Curing cost, thus further economizing the production cost of recycled aggregate concrete.
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early age behavior of recycled aggregate concrete under Steam Curing regime
Journal of Cleaner Production, 2017Co-Authors: Asad Hanif, Zeyu Lu, Cheolwoo ParkAbstract:Abstract This study addresses the effects of accelerated hydration in recycled aggregate concrete (RAC) due to the incorporation of High Early Strength Cement (HESC) and employing the Steam Curing method. The RAC was formulated by the complete replacement of natural aggregates with recycled aggregates. The resulting compressive strength, elastic modulus, and shrinkage strain results at early-ages were assessed and compared with concretes incorporating natural aggregates and ordinary Portland cement (OPC). By employing Steam Curing with HESC as binder, 70% of the design strength could be achieved in one day, however for the contemporary concretes with OPC as binder, the 1-day strength was about 60% of design strength. With HESC as binder, the change in mechanical properties was found to be minimal after 48 h of casting whereas such change was observed at 72 h age for OPC containing concretes. Utilizing recycled aggregates led to a lower net shrinkage strain indicating improvement against early-age cracking. The cost-benefit analysis showed that for accelerated hydration in concrete, utilizing recycled aggregates leads to lower associated CO 2 emissions at reduced cost. Replacing OPC with HESC improves the resulting early – age properties, but the production cost also increases. The study suggests RAC and HESC are beneficial for concrete elements with larger surface area to depth ratio, like road pavements, floorings, reinforced concrete slabs, and precast elements.
Payam Vosoughi - One of the best experts on this subject based on the ideXlab platform.
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effect of Steam Curing cycles on strength and durability of scc a case study in precast concrete
Construction and Building Materials, 2013Co-Authors: A A Ramezanianpour, M H Khazali, Payam VosoughiAbstract:Abstract Use of Self-Compacting Concrete (SCC) in pre-cast concrete plants is growing rapidly due to its benefits such as reduction in labor and equipment costs, increasing productivity, providing flexibility in filling highly reinforced sections and complex formworks, lowering the noise on job site and having superior surface quality. Also, considering the critical importance of “production time” in precast plants, accelerated Curing is considered as an inevitable part of precast concrete elements production. In this study the effects of thirty-six different Steam-Curing regimes on the compressive strength and permeability of a self-compacting concrete mixture, used in precast concrete elements of Sadr elevated highway was investigated. Compressive strength measurements indicated that in a constant total time, increase in preCuring period leads to lower immediate compressive strength. On the other hand, increase in treatment temperature and total cycle time (which means higher energy and time consumption) led to higher immediate compressive strength. Furthermore, durability tests results demonstrated that application of cycles with maximum temperature of 70 °C imposes negative effect on durability properties of reference SCC, such as surface resistivity and capillary absorption. Finally, on the basis of three criteria (compressive strength, permeability and energy consumption by Steam Curing cycle), an optimum Steam Curing cycle was introduced and utilized in the precast concrete plant.
Qiang Wang - One of the best experts on this subject based on the ideXlab platform.
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influence of alkali activators on the early hydration of cement based binders under Steam Curing condition
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Dengquan Wang, Qiang Wang, Zhenggang FangAbstract:The effects of water glass, NaOH, Na2SO4, and Na2CO3 on the early hydration of plain cement and two composite binders incorporating 40 mass% ground granulated blast furnace slag (GGBS) and 40 mass% fly ash under the Steam Curing temperature of 60 °C were investigated. Meanwhile, a 20 °C Curing condition was set as a reference. The results showed that water glass, NaOH, and Na2CO3 can improve the exothermic rates of the binders at the acceleration period and promote the reaction of GGBS and fly ash. However, the alkali activators inhibited the hydration of Portland cement at the deceleration period, which was more significant at 60 °C. Thus, the alkali activators cannot efficiently increase the cumulative hydration heat within 16 h under Steam Curing or even appear to decrease. Na2SO4 shows a better performance than the other three alkalis in the early hydration of the composite binders due to its promotion on the formation of AFt, but it cannot efficiently increase the cumulative hydration heat too. The results also showed that all of the alkali activators significantly decreased the form-removal strength of cement–GGBS composite binder. For cement–fly ash composite binder, the form-removal strengths of the samples activated by a low concentration of water glass and high concentration of Na2SO4 were close to that reacted with water, while the form-removal strengths of the samples activated by other alkaline solutions were lower. Overall, the four alkali activators cannot improve the form-removal strength of Steam-cured mortar containing a large volume of mineral admixtures.
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influence of Steam Curing method on the performance of concrete containing a large portion of mineral admixtures
Advances in Materials Science and Engineering, 2017Co-Authors: Mengyuan Li, Qiang Wang, Jun YangAbstract:A comparison was made between the impact of raising the thermostatic temperature and the impact of prolonging the thermostatic time on the performance of Steam-cured concrete containing a large portion of fly ash (FA) or ground granulated blast furnace slag (GGBS) by analysing the form removal strength, chemically combined water content, reaction degree, strength development, chloride permeability, and volume stability. For the materials and test conditions reported in this study, raising the thermostatic temperature is more favourable for concrete containing FA, as indicated by the significantly higher form removal strength and the higher growth of reaction degree of FA compared with prolonging the thermostatic time. With an increase in the thermostatic temperature, the hydration degree of a binder containing FA or GGBS initially increases and subsequently decreases. Although concrete containing FA can obtain satisfactory form removal strength with Steam Curing at 80°C, the late strength development of concrete containing FA is slow for the same Curing conditions. The effect of the late performance of resistance to chloride ion permeability improved by FA is better than the effect improved by GGBS. The risk of destroying the structure of concrete containing a large portion of FA or GGBS due to delayed ettringite formation (DEF) is minimal when specimens were Steam-cured at 80°C.
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properties of high volume limestone powder concrete under standard Curing and Steam Curing conditions
Powder Technology, 2016Co-Authors: Zengqi Zhang, Qiang Wang, Honghui ChenAbstract:Abstract A comparative study of the mechanical properties, volume stability and durability of high-volume limestone powder concrete (HVLPC) and high-volume fly ash concrete (HVFAC) was conducted by testing pore structures of the paste and determining the adiabatic temperature rise, porosity, compressive strength, chloride ion permeability, 1 year's natural carbonation depth and dry shrinkage strains of the concrete. The test results illustrate that the reductive influence of high-volume limestone powder on the temperature rise of the massive concrete is identical to that of the high-volume fly ash. Compared with high-volume fly ash concrete, high-volume limestone powder concrete with the same water/binder ratio has relatively high interconnected porosity, low compressive strength, and low resistance to carbonation and chloride ion penetration, especially at the Steam-Curing conditions. The volume stability of concrete containing a high volume of limestone powder is almost identical to that of concrete containing fly ash with the same water/binder ratio. Reducing the water/binder ratio and replacing part of the limestone powder by ground granulated blast furnace slag can reduce the negative effects of limestone powder on the macro-properties of concrete.
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influence of pre Curing time on the hydration of binder and the properties of concrete under Steam Curing condition
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Qiang Wang, Mengyuan Li, Bo ZhangAbstract:There is a pre-Curing period before the freshly made concrete elements were exposed to Steam Curing in the Steam Curing process. In this paper, the influence of pre-Curing time on the hydration of binder and the properties of concrete under Steam Curing condition was investigated. Three binders were used: the pure cement, the binder containing high content of GGBS, and the binder containing high content of fly ash. Three pre-Curing times (1, 3, and 6 h) and one Steam Curing period at 60 °C (over 8 h) were adopted. Results show that pre-Curing time has limited influence on the hydration degree of binder, and compressive strength and pore structure of paste. The influence of pre-Curing time has limited influence on the compressive strength and chloride permeability of the pure cement concrete and the concrete containing high content of GGBS at whether early or late ages, indicating that the proper pre-Curing time can be as short as 1 h for these two concretes. Increasing pre-Curing time enhances the late-age compressive strength of the concrete containing high content of fly ash significantly, but it has limited influence on the late-age permeability.
Chunxiang Qian - One of the best experts on this subject based on the ideXlab platform.
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effects of Steam Curing on strength and porous structure of concrete with low water binder ratio
Construction and Building Materials, 2011Co-Authors: Mingfang Ba, Chunxiang QianAbstract:Abstract A research program was carried out to investigate the effects of duration of initial Steam Curing at atmosphere pressure on compressive strength of concrete with low water/binder ratio. The results showed that the compressive strength of samples Steam cured for 5, 10, 14 h increased, while it decreased distinctively for sample Steam cured for 24 h. Mercury intrusion porosimetry (MIP) method and scanning electron microscope-backscattered electron (SEM-BSE) image analysis technique were adopted to measure the corresponding variation of porous characteristics caused by the increasing duration of Steam Curing. The changes in coarse porosity and total porosity calculated by SEM-BSE image analysis and MIP method respectively could indicate the relationship between porosity and mechanical properties of the concrete subjected to different duration of Steam Curing. Compared with total porosity obtained by MIP method, the coarse porosity by SEM-BSE image analysis was in better accord with the compressive strength because the coarse pores measured by SEM-BSE image analysis were larger than 0.5 μm and included not only the interconnected pores but also the closed ones. An empirical model was developed to evaluate the influence of duration of initial Steam Curing on the compressive strength of concrete. By comparison, the measured compressive strength was in great accordance with the compressive strength calculated by the proposed model.
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Effects of Steam Curing on strength and porous structure of concrete with low water/binder ratio
Construction and Building Materials, 2010Co-Authors: Mingfang Ba, Chunxiang QianAbstract:Abstract A research program was carried out to investigate the effects of duration of initial Steam Curing at atmosphere pressure on compressive strength of concrete with low water/binder ratio. The results showed that the compressive strength of samples Steam cured for 5, 10, 14 h increased, while it decreased distinctively for sample Steam cured for 24 h. Mercury intrusion porosimetry (MIP) method and scanning electron microscope-backscattered electron (SEM-BSE) image analysis technique were adopted to measure the corresponding variation of porous characteristics caused by the increasing duration of Steam Curing. The changes in coarse porosity and total porosity calculated by SEM-BSE image analysis and MIP method respectively could indicate the relationship between porosity and mechanical properties of the concrete subjected to different duration of Steam Curing. Compared with total porosity obtained by MIP method, the coarse porosity by SEM-BSE image analysis was in better accord with the compressive strength because the coarse pores measured by SEM-BSE image analysis were larger than 0.5 μm and included not only the interconnected pores but also the closed ones. An empirical model was developed to evaluate the influence of duration of initial Steam Curing on the compressive strength of concrete. By comparison, the measured compressive strength was in great accordance with the compressive strength calculated by the proposed model.
