Stabilization of Recycled Demolition Aggregates by Geopolymers comprising Calcium Carbide Residue, Fly Ash and Slag precursors

• Calcium Carbide Residue, Fly Ash and Slag precursors in geopolymers.
• Strength tests on geopolymer stabilized RCA and CB.
• Resilient modulus (MR) tests on geopolymer stabilized RCA and CB.
• Three-parameter model capturing effect of confinement and deviator stresses on MR.

Calcium Carbide Residue (CCR) is the by-product of acetylene gas production. In this research, the alkali activation of Calcium Carbide Residue (CCR) was studied as an economical and low-carbon precursor for development of geopolymer binder. Recycled Concrete aggregates (RCA) and Crushed Brick (CB) are the two major demolition material sources for the Construction and Demolition (C&D) industry. The cement stabilization of C&D materials has been evaluated in recent years, however due to the large carbon footprint associated with Portland cement, geopolymers which utilize the alkali activation of industrial waste by-products have garnered increasing interest from industry. Evaluation of the geopolymer stabilization of C&D materials with CCR precursor were also compared with traditional Fly Ash (FA) and Slag (S) precursors. In addition, the performance of CCR based geopolymers with supplementary FA and S precursors were also evaluated. The three precursors (CCR, FA, S) were combined with contents of up to 10% for the geopolymer stabilization of the C&D materials. A liquid alkaline activator comprising sodium silicate solution (Na2SiO3) and sodium hydroxide (NaOH) was used for the alkali activation of the CCR based geopolymers. The strength and durability of the geopolymer stabilized C&D materials were evaluated to ascertain their application in pavement bases/subbases. The results of Unconfined Compressive Strength (UCS) and Resilient Modulus (MR) testing of these geopolymer stabilized CB and RCA aggregates indicate that different mixtures of CCR based geopolymers can be used to improve the strength properties of the C&D aggregates for pavement base/subbase applications. CCR + 5% S with the C&D materials resulted in the optimum combination for CCR based geopolymer stabilization of C&D aggregates.