Abstract
Using recycled aggregate from construction and demolition (C&D) wastes as a construction material is a potential method for solving the disposal of C&D wastes, which can reduce the exploitation of natural aggregate. In this study, extensive laboratory tests were carried out to investigate the reliability of the C&D wastes used as road base material. Meanwhile, the gradation design and the dominant aggregate size range were considered, and a physical disposal method was proposed to enhance the structural performance of the recycled material by replacing the skeleton of the recycled aggregate (RA) with high‐quality limestone. The test results showed that (1) given the high absorbency and fragility of C&D wastes, its RA was not enough to provide the strength and stability required by the base; (2) the compaction characteristics of the RA are quite different from that of the limestone aggregate, but the final compaction effect is basically the same; (3) the replacement treatment proposed in this study is an effective approach to improve the performance of the recycled granular base because the breakage rate decreased by at least 28.2% and the mechanical properties increased by approximately 50% compared with that of the untreated specimen; and (4) when the limestone content reached 75%, the California bearing ratio and the resilient modulus of the graded B specimen exceeded 120% and 200 MPa, respectively, satisfying the pavement requirement in medium traffic.
Highlights
In this study, a series of laboratory experiments were performed to systematically evaluate the performance and applicability of recycled aggregate (RA) for granular base, taking into account enhanced treatments by gradation and composition design
Materials. e natural aggregates and coarse RAs used in the experiment were produced by a renewable technology company in Changsha, China. e process flow of RA production is shown in Figure 1. e coarse RA mainly consists of exposed gravel, brick slag, surface-coated mortar gravel, brick slag, pure cement mortar block, and a small amount of impurities. ree piles of samples were randomly selected from the material site, and the proportion of their components was determined, as shown in Table 1. e RA was mainly composed of 34% natural stone, 36% brick, 23% concrete, and a small amount of impurities
According to the Test Methods of Aggregate for Highway Engineering (JTG E42-2005) in China, aggregates are divided into coarse and fine aggregates according to their particle sizes. e particle sizes between 0.15 and 4.75 mm belong to fine aggregates, and those between 4.75 and 9.0 mm belong to coarse aggregates
Summary
Limestone is widely used in construction and industrial raw materials. It has a compact structure, no micro pores, no. E basic physical properties of the RA and limestone are shown in Tables 2 and 3, respectively:. (a) Coarse aggregate: Table 2 summarizes the physical properties of coarse RA and limestone coarse aggregate. (b) Fine aggregate: Table 3 summarizes the physical properties of fine RA and fine limestone aggregate. E percentage of grains less than 0.075 mm and the plasticity index of fine RA do not meet the specifications, and the water absorption rate is higher than that of limestone. Through the above analysis, most of the physical properties of the coarse and fine aggregate cannot satisfy the requirements. Through the above analysis, most of the physical properties of the coarse and fine aggregate cannot satisfy the requirements. erefore, further attempts were carried out by mix design and component replacement to improve the mechanical properties of the RA base materials
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