Study on Mix Proportion Design Based on Strength and Sulfate Resistance of 100% Recycled Aggregate Concrete

Abstract

This paper presents the mechanical properties of 100% recycled aggregate concrete (RAC), and the results and analysis of the dry–wet cycle accelerated sulfate attack test. The results show that recycled concrete aggregate (RCA) can replace the coarse and fine aggregate. The recycled clay brick aggregate (RCBA) is not suitable for use as a coarse aggregate because the water absorption exceeds the standard. RCA replaces the coarse aggregate; and RCBA returns the fine aggregate to prepare 100% recycled concrete aggregate (RAC). The water–cement ratio is the most significant factor affecting the compressive strength of 100% RAC. The results of the mechanical properties analysis show that the compressive strength of RAC is less than that of NAC, and the difference in compressive strength between 100% RAC and NAC decreases with age. The splitting tensile strength of 100% RAC was slightly higher than that of NAC except for 7 d. The results of the dry–wet cycle accelerated sulfate attack test showed that the performance of 100% RAC was lower than that of NAC under the dry–wet process and sulfate attack coupling. Still, the loss rate was less than 5%, which met the standard resistance to the dry–wet cycle accelerating the sulfate attack.

Current Knowledge and Pending Research on Sulfate Resistance of Recycled Aggregate Concrete

“…In the case of wetting-drying cycle tests, some works in the literature evaluate protocols and concentrations that provide better test times and have some correlation with long-term tests [117,158]. For partial saturation tests, there is no single criterion, but in general, these tests use semi-buried or semi-submerged specimens in soils or sulfate solutions, with concentrations that are also very aggressive [57,88,159]. Regardless of the method applied, the most relevant aspect to delve into is finding information that includes the results of accelerated tests and field exposures.…”

“…Figure 3.Degradation ratios of concretes with different % CRA exposed to ESA + PSA[63,65,77,83,84,88,89,91].…”