Relationship between Defects of Recycled Aggregate and Mechanical Properties of Recycled Aggregate Concrete

Abstract

This paper presents an experimental research on the influence of defects of recycled coarse aggregate on mechanical properties of recycled aggregate concrete (RAC). Concretes at two water/binder ratios (0.255 and 0.586) were broken into recycled aggregate (RA). A type of thermal treatment, i.e. heating to target temperature 620 °C, which was maintained for 3 hr, was employed to remove mortar from gravel in RA. Tests were conducted on RA and natural aggregate to measure their water absorption and crushing values, and on RAC and natural aggregate concrete (NAC) to measure compressive strength, tensile splitting strength, and fracture energy. The experimental results revealed that both gravel damage and mortar attached can significantly influence the water absorption and crushing value of RA, as well as strength and fracture energy of RAC. The mechanical properties RAC were obviously lower than those of NAC at an identical mix proportion. Moreover the removal of mortar caused additional change in mechanical properties of RA, which might be a decrease in mechanical properties in the case of low water/binder ratio, but might be an increase in mechanical properties in the case of high water/binder ratio. As to RAC at a low water/binder ratio, gravel damage was a main factor governing the decrease in fracture energy, which means a decrease in cracking resistance of hardened RAC, whereas the mortar attached had only a slight influence on fracture energy. However, as to RAC at a high water/binder ratio, mortar attached could significantly cause a greater decrease in cracking resistance of RAC than that caused by gravel damage.

Effect of Construction Wastes as Coarse Aggregates in Cement Concrete: A Review

“…Waste management in the building and demolition industry relies heavily on the 3R (reduce, reuse, and recycle) concepts. In recycling, waste items are transformed into fresh raw materials [41][21] reported that recycling also promotes environmental sustainability by getting rid of the need for raw materials and turning waste into eight useful processes. Although recycling is widely accepted as the most effective strategy for achieving long-term sustainability, real-world implementation has proven to be challenging [21].…”

Experimental Study on Preparation and Characteristics of Concrete Modified by Construction Waste

“…Ahmad S I [32] also indicates that the strength of recycled aggregate concrete is directly proportional to the improvement in the quality of recycled aggregate. Peng Gaifei et al [33] pointed out that compared to using recycled aggregates to prepare cement-based recycled materials, the mechanical properties of concrete prepared with natural aggregates are significantly lower in the latter. And it is believed that the main reason for this phenomenon is the stone damage caused by the preparation process of recycled aggregates and the hardened mortar attached to the surface.…”

“…And it is believed that the main reason for this phenomenon is the stone damage caused by the preparation process of recycled aggregates and the hardened mortar attached to the surface. Purushothaman R et al [33][34][35][36] found that there is a significant difference in the water absorption and strength properties of recycled aggregates compared to natural aggregates, mainly manifested in the high water absorption rate, high crushing value, and low apparent density of recycled aggregates. The water absorption rate of recycled aggregate is about four times higher than that of natural coarse aggregate, and the crushing index is also 23.85% higher than that of natural coarse aggregate.…”

Size effect on dynamic compressive failure mode and mechanical properties of recycled concrete

“…1,2 The research shows that the compressive strength of recycled concrete is about 80% of that of ordinary concrete. [3][4][5][6] The recycled concrete made of recycled coarse aggregate and natural fine sand has been tested, and the results show that the compressive and tensile strength of recycled concrete decreases by about 5% compared with ordinary coagulation. 7 The uniaxial compressive tests of standard columns were carried out with a Discussion on this paper must be submitted within two months of the print publication.…”