Beneficial Reuse of Construction Surplus Clay in CLSM

The disposal of on-site construction imperfect earth materials and the production of standard engineering aggregates for backfill have been facing increasingly environmental and ecological challenges in many densely populated metropolitan areas. This paper presents an experimental study using soft excavated surplus clay to produce a clay-based controlled low strength material (CLSM) as subgrade material for a pedestrian plaza. Observations have been made for physical and engineering properties based on the fresh and harden-state of the samples. The presented test results include physical and engineering properties for flowable and hardened samples. Two control parameters, the weight ratios of cement-to-water (C/W) and water-to-solid (W/S) were defined to correlate each investigated property with the variations of mixture proportions. Experimental findings indicate that a clay-based CLSM can be developed as an alternative structural backfill material. The recommended C/W and W/S design ratios for the proposed material should be 0.5-0.7 and 0.7, respectively. The fresh state of such mixture presents acceptable flowability and bleeding for easy construction. Its hardened state also behaves as stiff clay with lowest compressibility and stronger bearing capacity, and therefore qualifies for the proposed structural support. The results explore an innovative scheme for the reduction and reuse of construction surplus clay, and suggest a beneficial paradigm for the sustainable development of built environments. However, the findings presented herein can only ensure the validity of the mixtures with the materials in this study. It is highly recommended that those interested in clay-based CLSM perform site-specific experimental studies using local materials to evaluate the particular mix designs.