Utilization of excavated soil in coal ash-based controlled low strength material (CLSM)

• Coal ash and excavated soil can be used in CLSM production.
• The engineering properties of CLSM using excavated soil, possibly up to 30%, satisfy the specifications of ACI 229R.
• An increase in excavated soil content can lead to improvement in CLSM stability.
• It is feasible to completely replace Portland cement with cementless binder in CLSM production.

Coal ash generated from the combustion process of thermal power plants and excavated soil from construction sites in Jeolla Province (South Korea) have significant environmental and economic impacts. The aim of this study is to evaluate the feasibility of controlled low strength material (CLSM) production using wastes (e.g., ponded ash, fly ash, and excavated soil) and cementless binder as full replacement of Portland cement in CLSM mixtures by assessing its engineering properties. First, control mixtures were produced with Portland cement or cementless binder, Class F fly ash, ponded ash, and water. Then, for other mixtures, excavated soil substituted for ponded ash in amounts of 10, 20, 30, and 40% by weight. The bleeding, flowability, and initial setting time of fresh CLSM mixtures were measured; afterward, they were hardened and tested for compressive strength, water absorption, and corrosivity. It was found that the engineering properties of CLSM with excavated soil, possibly up to 30%, satisfied the specifications of ACI 229R. In particular, it was found that an increase in excavated soil content as replacement could lead to an improvement in the stability (bleeding rate) of the proposed CLSM mixtures. Finally, it is worth noting that cementless binder could be feasibly used to completely replace Portland cement in CLSM production.