Development of a new cementless binder for controlled low strength material (CLSM) using entirely by-products.

Highlights • A new cementless binder is developed from fly ash, red mud, lime, and gypsum. • Engineering properties of CLSM using the developed binder satisfy the specifications of ACI 229R. • CLSMs made with the newly developed binder are classified as non-hazardous materials, conforming to the EPA guidelines. • An increase in red mud content can lead to an improvement in early strengths of CLSM. • It is feasible to completely replace Portland cement with the proposed cementless binder in CLSM production. Abstract The aim of this study is to develop of a new binder using entirely by-products for a production of CLSM. The new cementless binder, tentatively named Fa-RmLG, was made from fly ash (Fa), lime (L), gypsum (G) and red mud (Rm). Various CSLM mixtures were produced with pond ash and different proportions of the new cementless binder Fa-RmLG. To assess the technical feasibility of this cementless binder in CLSM, three phases corresponding with three mix proportions were performed in this study. A preliminary proportion (phase I) was conducted to evaluate the engineering properties of five proposed CLSM mixtures in which the ratio of gypsum to red mud (G/Rm) varied in the range of 0.4–6.0. Subsequently, the best CLSM mixture was selected to be the control mix for a further study, which investigated the effect of fly ash content (phase II) and lime content (phase III) on the engineering properties of all CLSM mixtures in these phases. The obtained results showed that the engineering properties (flowability, bleeding, setting time, unconfined compressive strength, and microstructural analysis) and environmental impacts (corrosivity, heavy metals) of CLSM made with the proposed cementless binder met the ACI 229R requirements through a control of the cementless binder proportions. In conclusion, it was found a feasibility of using the developed Fa-RmLG binder for the production of CLSM. [ABSTRACT FROM AUTHOR]