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The construction industry is one of the key industries with high potential for the circular economy; the promotion of reuse and recycling of construction and demolition waste (CDW) is essential for sustainable urban development. In this study, a series of compaction, California bearing ratio, saturated hydraulic conductivity, and particle breakage tests of well– and poor–graded mixtures of recycled clay brick aggregates (RCBs) and recycled concrete aggregates (RCAs) with maximum aggregate diameters of 19, 25, and 37.5 mm were carried out to examine the practical application of those mixtures to unbound roadbed materials in Vietnam. The experimental results suggest that the maximum amount of RCBs added to RCAs should be less than 30% when applied to unbound roadbed materials. In addition, it was found that the mixing proportions of RCBs and RCAs and the maximum aggregate diameter, gradation of aggregates, and initial moisture condition control the saturated hydraulic conductivity. Further, the particle breakage characteristics under compaction were carefully examined, and it was found that the percentage increment/decrement, as well as a newly introduced method of estimating the mixing proportions of RCAs and RCBs in the fine fraction (<2.36 mm), is effective in understanding the mechanism of particle breakage of RCA and RCB mixtures. [ABSTRACT FROM AUTHOR]

Due to the rapid increase in population and urbanization, municipal solid waste (MSW) generation is increasing. Sri Lanka, in particular, faces serious difficulties in finding new sites for MSW disposal, due to the lack of available space; therefore, the rehabilitation of existing MSW dumping sites and the extension of their services are required to achieve sustainable urban development. To examine suitable rehabilitation techniques, it is essential to identify the physicochemical and mechanical properties of dumped MSW, fully considering climatic conditions, waste composition, and the time since the waste was dumped. In this study, therefore, the physicochemical and mechanical properties of dumped MSW were investigated; the dumped MSW was taken from existing MSW dumping sites in three climate zones in Sri Lanka, namely the Karadiyana site in the wet zone, Udapalatha in the intermediate zone, and Hambantota in the dry zone, and it was taken at different times after being dumped. The results showed that the waste composition and biodegradation of organic materials affected the physicochemical and mechanical properties of the dumped waste. The measured compaction parameters of the "old" sites at Udapalatha and Hambantota were higher compared to the "new" sites. Compaction parameters at the Karadiyana site, on the other hand, were low, at even >20 years since being dumped, probably due to the high amount of scarcely compacted materials. In direct shear tests, both strain hardening and softening of the waste samples were observed, depending on the difference in vertical stress. Based on the Pearson correlations among measured physicochemical and mechanical parameters, it was found that the loss on ignition (LOI) would be a good indicator to quickly assess the mechanical parameters of "new" and "old" waste materials, due to the small sensitivities to waste age and climate conditions in Sri Lanka. In particular, LOI correlated well to measured specific gravity and compaction properties, and the r2 values of correlations exceeded |0.80|. [ABSTRACT FROM AUTHOR]

Reuse and recycling of non-hazardous construction and demolition waste and industrial byproducts in the construction industry is vital to promote environmentally sound waste management. In particular, the effective utilization of sludge and waste clay bricks is greatly required in developing countries. This paper studied compaction characteristics and the California bearing ratio (CBR) of water treatment sludge (WTS) blended with clay brick aggregates for the road subgrade application. Raw and waste clay bricks from Vietnam were used for preparing clay brick (CB) and recycled clay brick (RCB) aggregates of three different particle sizes, Coarse 10- 30 mm, Graded 2-30 mm, and Fine 2-10 mm. In addition, fine residues of clay bricks with a size of < 2 mm were tested. WTS sieved under 2.0 mm blended with CB/RCB aggregates with different mixing proportions (f) were used for compaction and CBR tests in the laboratory. Results showed that the measured maximum dry densities (MDD) were dependent solely on mixing proportion f and increased linearly with f irrespective of blended fractions of CB/RCB aggregates. Unlike MDD, the measured CBR was dependent on both f and blended fractions. Especially, the WTS blended with coarse and graded fractions with a range of 60 ≤ f ≤ 80% showed a significant improvement in CBR (>100%). Due to its limited particle breakage and high CBR, the WTS blended with graded CB/RCB aggregates was preferable for the road subgrade application. [ABSTRACT FROM AUTHOR]