Hydraulic conductivity and undrained shear strength of clay-construction and demolition solid waste materials mixtures

Abstract

The study aims to investigate the effects of three different construction and demolition materials (CDMs), including crushed waste asphalt (CWA), crushed waste bricks (CWB), and crushed waste concrete (CWC), on some geotechnical properties of low plastic clayey soil, particularly, the undrained shear strength (Su) and the hydraulic conductivity (k). A set of experimental tests were performed on clayey soil and on clayey soil-CDM mixtures at mixing ratios of 5%, 10%, 15%, and 20% by dry weight. The results show that the soil plasticity decreases as the CDMs increase. Quantitatively, it is found a maximum of 12%, 6%, and 6% decrease in the liquid limits (LL) and a maximum of 9%, 4%, and 6% decrease in the plasticity limit (PI) of the mixtures with 20% of CWA, CWB, and CWC, respectively. The results of the Su estimated empirically from the fall cone tests show that the Su decreases as the CDMs increase. The Su reduces by approximately 10% and 2% of the mixtures with 20% CWA and CWB, respectively. But the Su is not affected by the CWC additive for water content lower than approximately 35%. The k value increases as the CDMs increase. The results show that the reported k value increases by 75%, 79%, and 247% of the mixtures with 20% of CWA, CWB, and CWC, respectively. Additionally, the k values obtained from the consolidation test confirm the findings of the effect of the CDMs on the coefficient of hydraulic conductivity.

Improvement of consolidation properties of clay soil using fine-grained construction and demolition waste

“…The samples of original soil and soil-CDW mixture fall in the same zone of low plasticity clay soil but show lower values of LL and PI. In comparison, Abdulnafaa et al. (2021) experienced changes in soil classification of low plasticity clay soil to low plasticity silty soil after adding construction and demolition materials in the soil as the additive materials contained of stone, brick chips and others construction materials.…”

“…As seen in Figure 5 , the compaction curve changes their peak with the addition of CDW in soil. As the CDW content increased in the soil sample, the optimum moisture content decreased because the non-cohesive CDW powder absorbed less water than natural soil particles and maximum dry density increased because CDW powder has more sands and greater specific gravity than clayey soil ( Abdulnafaa et al., 2021 ). The changes in optimum moisture content and maximum dry density of soil sample due to CDW percentages are shown in Figure 6 .…”

“…(2021) . Abdulnafaa et al. (2021) explained that k -value changes because increasing granular and non-cohesive materials in the soil accelerates the passing of water through it.…”