Effect of Various Supplementary Cementitious Materials on Early-Age Concrete Cracking

摘要

Abstract: This paper focuses on the effect of supplementary cementitious materials on early-age mechanical and viscoelastic properties of concrete, restrained shrinkage-induced cracking, and time to cracking. Compressive strength, indirect tensile strength, and the elastic modulus were measured with different percentage of ordinary portland cement (OPC) replacement using either fly ash, ground-granulated blastfurnace slag (GGBFS), or ferronickel slag (FNS). Tensile creep and drying shrinkage were measured on dog-bone-shaped specimens. Restrained shrinkage-induced stresses and concrete cracking age were assessed by using the ring test. Results revealed that early-age strength development of fly ash-, GGBFS-, and FNS-blended concrete is lower than that of the corresponding OPC concrete. Similar tensile creep coefficients were observed for fly ash-blended concrete and OPC reference concrete whereas GGBFS- and FNS-blended concretes showed significantly higher tensile creep. Drying shrinkage was not altered to a great extent when OPC was replaced by fly ash. However, concrete containing GGBFS and FNS showed more shrinkage than OPC concrete. Partial replacement of OPC by supplementary cementitious materials resulted in a shorter time to cracking. 30% OPC replacement by FNS had the lowest influence on time to cracking with only 20% reduction compared to the reference OPC concrete. 20% replacement by fly ash and 30% replacement by GGBFS led to a reduction in time to cracking of about 33% and 40%, respectively, compared to the reference OPC concrete.