Saturated hydraulic conductivity of construction wastes for potential replacement of sand blanket

A sand blanket is usually adopted in earthen structures to provide drainage and accelerate soil consolidation. Owing to the over-exploitation of sand, alternative materials such as construction wastes (CWs) are explored for blanket layers. However, the hydrological performance of CW, including crushed rock, broken concrete, and broken asphalt, is rarely investigated. This study examined the saturated hydraulic conductivity of these wastes at three particle size distributions ranging between 5 and 37·5 mm. Particle roundness was determined while various practical models, including Hazen’s equation, were adopted to estimate the hydraulic conductivity. Experimental results showed that the hydraulic conductivity of CW increases with an increasing particle size but at different degrees. The hydraulic conductivity of all conditions was at least ten times greater than that of typical sand (i.e. 10⁻² ms⁻¹). This demonstrates that CW can replace sand for blanket layers with sufficient drainage capacity, thereby facilitating utilisation and recycling of CW for sustainability. Although the estimations made using Hazen’s equation were better than other models, the highest coefficient of determination (R²) was only 0·35. This suggests that modifying common practical models, such as consideration of particle roundness, is necessary to improve their applicability to CW and hence promote the engineering design of CW blankets.