Short- and long-term effects of sodium chloride on strength and durability of coal fly ash stabilized with carbide lime

Abstract

The research presented aims to quantify the influence of the curing period (t), dry unit weight (γd), lime amount (L), and the addition of sodium chloride (NaCl) on the short- and long-term behaviors of coal fly ash – carbide lime blends. Strength and wet–dry durability tests were carried out for differing values of porosity (η), L, and curing time (t) on mixtures that either contained small amounts of NaCl or contained none. Addition of NaCl to the mixtures resulted in significant increase in early strength gain when compared to specimens without NaCl, which demand longer curing periods to reach similar strength values. The addition of NaCl to coal fly ash – carbide lime blends reduced the accumulated loss of mass (ALM) after 12 wet–dry brushing cycles for specimens at early stages of curing (about 50% for 7 days). Equivalence in the unconfined compressive strength (qu) and ALM(after 12 wet–dry cycles) between the specimens with and without NaCl is achieved in the long term. Finally, a variance analysis performed regarding qu and ALM results yielded that the order of importance of the controllable factors changed from t, NaCl addition, γd, and L for strength to γd, t, NaCl addition, and L for ALM(after 12 wet–dry cycles).