Use of Natural Zeolite to Produce Self-Consolidating Concrete with Low Portland Cement Content and High Durability

AbstractSelf-consolidating concrete (SCC) is one of the innovative products in concrete technology that has been developed in recent years. However, many researchers are still trying to optimize the mixture proportions and investigate the incorporation of new materials in SCC. The typical high content of portland cement in SCC is one of the main challenges in optimization of its mixture proportions. This high cement consumption increases the production cost of SCC and, considering the large amount of CO2 emitted during portland cement production, is also undesirable from an environmental point of view. In this study, two approaches were employed to lower the portland cement content in SCC mixtures, namely, adopting a dense aggregate grading and partially replacing portland cement with natural zeolite. Portland cement was replaced by natural zeolite at different percentages to investigate the effect of this natural pozzolan on the fresh and hardened properties of the SCC mixtures. Fresh properties of the SCC mixtures were assessed by slump flow, T50 time, J-ring, and GTM screen stability tests. Compressive strength, electrical resistivity, and rapid chloride penetration tests (RCPTs) were carried out to evaluate the hardened properties of the SCC mixtures. It was concluded that producing a durable SCC mixture containing a low portland cement content of 262.5 kg/m3 is possible while keeping the total cementitious materials content at a constant 350 kg/m3. On the basis of the fresh-SCC test results, using higher replacement levels of natural zeolite (up to 30%) led to improved segregation resistance but increased the required dosage of high-range water-reducer agent. At hardened state, using higher replacement levels of natural zeolite resulted in lower RCPT values and higher surface resistivity.