Cement production is responsible for consuming 13% of energy along with producing 7% of CO2 worldwide. Using supplementary cementitious materials (SCMs) such as pozzolans could be helpful in this regards, while it could potentially improve the properties of concrete. The results of previous investigations have illustrated the fact that pozzolans partially replacing cement as binaries (one pozzolan along with cement), resulted in the improvement of concrete's durability parameters in many cases. On the other hand, one of the main uses of pozzolans is in self-consolidating concrete (SCC), a special concrete that has gain attention and popularity in recent years due to its specific properties. Recent studies on SCC containing ternary (two pozzolans along with cement) blends revealed impressive improvements in the mechanical and specially durability properties, outperforming both binaries and non-pozzolanic mixes. This was attributed to the fact that using pozzolans resulted in great decrease in permeability caused by their filler effect along with transformation of CH to CSH or CASH. Also their high blain causes significant improvement in the pore structure of concrete. In this context, capillary pores increase in number, each with much lower volume and diameter compared to non-pozzolanic samples. Another consequence of using these materials is less porosity of the interfacial transition zone (ITZ). Overall, the numerous beneficial effects of using pozzolans in concrete is well-established, and this could promote the use of more pozzolans in concrete.
Nevertheless, there has few investigations concerning the effects of ternary mixes on the durability of SCC, and studying the properties of quadratics mixes (three pozzolans along with cement) has been rarely done. On this basis, the purpose of this research was to study the effects of using binary, ternary and quadratic blends on durability characteristics of SCC. In this regards, two natural pozzolan, namely trass and pumice, were used as cement replacements at 0, 10 and 20% levels in mixes containing 10% silica fume. Various tests on the fresh properties of SCC including slump flow as flow ability and J ring as filling ability test were performed. As for hardened concrete, the 28 day compressive strength, velocity of ultrasonic pulses in concrete, water absorption, depth of penetration of water under pressure, Surface Resistivity toward Chloride Ion Penetration and rapid chloride penetration (RCPT) tests were considered.
The results showed that binaries, only in compressive strength and to some extent in pulse velocity performed better compared to ternaries and quadratics. Also, it was concluded that ternaries slightly outperformed quadratics in terms of compressive strength, pulse velocity, and water penetration tests, whereas quadratics generally had slight superiority over ternaries in terms of electrical resistivity and rapid chloride penetration. Overall, choosing the best performance for each test result, using ternaries and quadratics decreased compressive strength, pulse velocity, water absorption, water penetration and rapid chloride penetration by 5%, 3%, 15%, 61%, 71% respectively, while increased electrical resistivity by 55% compared to binary mixture. In addition, all mixtures had desirable, water absorption below 2% and binaries, ternaries and quadratics had similar results with no significant differences.
