Performance of Fly Ash-Blended Cementitious Systems Incorporating CaCl2 and TEA: Effects on Mechanical and Hydration Properties

This study experimentally investigates the effects of CaCl2 and TEA, used individually and in combination, on the fresh and hardened properties of fly ash-blended cementitious systems. The primary objective was to evaluate the potential of chemical admixtures to mitigate the setting retardation and insufficient early-age strength development associated with fly ash incorporation while examining the effects of different admixture dosages. Cementitious mixtures containing 20% fly ash, CaCl2 at 1%, 3%, and 5%, and TEA at 0.1%, 0.2%, and 0.3% were prepared. Setting time, flow spread, compressive strength, and water absorption were determined, and the experimental data were evaluated using ANOVA. The results showed that fly ash incorporation prolonged setting time and limited early-age strength development. CaCl2 significantly reduced the setting time with increasing dosage, mitigating the retarding effect of fly ash; however, higher dosages markedly reduced fresh-state flowability. TEA used alone prolonged setting time, particularly at higher dosages, whereas its retarding effect was substantially moderated when combined with CaCl2. Nevertheless, the combined use of CaCl2 and TEA did not provide the expected improvement in mechanical performance, and particularly at higher dosages, resulted in significant reductions in compressive strength.