recycled coarse aggregate
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Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 257
Author(s):  
Guoying Liu ◽  
Qiuyi Li ◽  
Jialin Song ◽  
Liang Wang ◽  
Haibao Liu ◽  
...  

Due to the large amount of old hardened cement mortar attached to the surface of aggregate and the internal micro-cracks formed by the crushing process, the water absorption, apparent density, and crushing index of recycled coarse aggregate are still far behind those of natural coarse aggregate. Based on the performance requirements of different qualities of recycled coarse aggregate, the performance differences of recycled coarse aggregate before and after physical strengthening were observed. The results showed that the physical strengthening technique can remove old hardened mortar and micro powder attached to the surface of recycled coarse aggregate by mechanical action, which can effectively improve the quality of recycled coarse aggregate. The optimum calcination temperature of the recycled coarse aggregate was 400 °C and the grinding time was 20 min. The contents of the attached mortar in recycled coarse aggregates of Class I, II, and III were 7.9%, 22.8%, and 39.7%, respectively. The quality of recycled coarse aggregate was closely related to the amount of mortar attached to the surface. The higher the mortar content, the higher the water absorption, lower apparent density, and higher crushing index of the recycled coarse aggregate.


Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1512
Author(s):  
Zexin Yu ◽  
Yuanxin Guo ◽  
Gongbing Yue ◽  
Zhenwen Hu ◽  
Chao Liu ◽  
...  

Green recycled aggregate concrete (RAC) with high strength and low shrinkage is prepared based on recycled coarse aggregate produced by the particle-shaping and aggregate-strengthening method and green low-carbon new cement. This not only effectively alleviates the shortage of natural resources, but also improves the performance of recycled aggregate concrete, which is of great significance for multi-channel resource utilization of construction waste. In this study, three kinds of recycled coarse aggregates (RCA), including simple crushing recycled coarse aggregate (JD-RCA), one-time particle-shaping recycled coarse aggregate (KL-RCA) and two-time particle-shaping recycled coarse aggregate (EKL-RCA), were prepared from the preparation technology of recycled aggregate, and high belite sulphoaluminate cement with excellent performance was used. The effects of aggregate quality, aggregate replacement ratio, and cementitious material content on mechanical properties and shrinkage properties of green recycled aggregate concrete were studied in comparison with ordinary Portland cement-based recycled aggregate concrete. The testing results show that the particle-shaping method can effectively improve the aggregate quality. The compressive strength and dry shrinkage performance of recycled aggregate concrete made of particle-shaped aggregate are only a little different from those of natural aggregate concrete, and even the performance of recycled aggregate is better than that of natural aggregate concrete under the condition of a low replacement ratio of recycled aggregate. In addition, high belite sulphoaluminate cement-based recycled aggregate concrete (HBRAC) not only has early strength and rapid hardening, but also has excellent drying shrinkage resistance, and its shrinkage rate can be reduced to more than 75% compared with ordinary Portland cement-based recycled aggregate concrete (OPRAC).


Structures ◽  
2021 ◽  
Vol 34 ◽  
pp. 2996-3012
Author(s):  
Hongyuan Zhou ◽  
Houzhan Zhou ◽  
Xiaojuan Wang ◽  
Wanlin Cao ◽  
Tianyi Song ◽  
...  

2021 ◽  
Vol 930 (1) ◽  
pp. 012100
Author(s):  
E N Cahya ◽  
R Haribowo ◽  
E Arifi

Abstract Predicting the infiltration rate on inclined surfaces is a pending case, especially when compared to rain intensity. The inclined surface has less ability to generate ponding, leading to higher runoff and higher erosion rates. In the rainy season, on the highway with a very steep slope, erosion usually occurs and becomes very dangerous. By using porous concrete, it is expected to receive higher infiltration and less runoff. This study aimed to determine the impact of the inclined surface of porous concrete on infiltration capacity. The research was conducted using both natural coarse aggregate and recycled coarse aggregate made from concrete waste. The infiltration and permeability test were conducted using porous concrete slabs under 0 to 30% inclined surface. It was shown that the infiltration rate is getting lower as the surface is being steeper. It was also shown that porous concrete made from recycled coarse aggregate has higher performance on permeability and infiltration rate compared to porous concrete made from the natural one.


2021 ◽  
Vol 13 (23) ◽  
pp. 13200
Author(s):  
Yang Yu ◽  
Peihan Wang ◽  
Zexin Yu ◽  
Gongbing Yue ◽  
Liang Wang ◽  
...  

Shrinkage property is a significant indicator of the durability of concrete, and the shrinkage of green recycled concrete is particularly problematic. In this paper, construction waste was crushed and screened to generate simple-crushed recycled coarse aggregate (SCRCA). The SCRCA was then subjected to particle shaping to create primary particle-shaped recycled coarse aggregate (PPRCA). On this basis, the PPRCA was particle-shaped again to obtain the secondary particle-shaped recycled coarse aggregate (SPRCA). Under conditions where the dosage of cementitious material is 300 kg/m3 and the sand rate is 38%, a new high-belite sulphoaluminate cement (HBSAC) with low carbon emission and superior efficiency was used as the basic cementitious material. Taking the quality of recycled coarse aggregate (SCRCA, PPRCA, and SPRCA) and the replacement ratio (25%, 50%, 75%, and 100%) as the influencing factors to prepare the green recycled concrete, the workability and shrinkage property of the prepared concrete were analyzed. The results show that the water consumption of green recycled concrete decreases as the quality of the recycled coarse aggregate (RCA) increases and the replacement ratio decreases, provided that the green recycled concrete achieves the same workability. With the improvement of RCA quality and the decrease of replacement ratio, the shrinkage of recycled concrete decreases. The shrinkage performance of green recycled concrete configured with the SPRCA completely replacing the natural coarse aggregate (NCA) is basically the same as that of the natural aggregate concrete (NAC).


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