Studying the Effect of silicafume and zeolite on durability of self-consolidating concrete exposed to various exposure conditions in a simulated marine environment

The Persian Gulf is well known as one of the most aggressive environments in the world because of its high relative humidity, temperature, and concentration of chloride ions. Concrete structures are increasingly being deteriorated in this region. Therefore, Improving the durability of concrete structures in this environment is an important issue. Supplementary cementitious materials (SCMs) can be useful for concrete durability enhancement in such harsh environments. In this paper, the effect of silica fume on deterioration resistance to sulfate attack in seawater within simulated splash, tidal and submerged conditions have been studied in self-consolidating concretes and mortars containing silica fume (SF) with/without natural zeolite (NZ). To achieve this objective, self-consolidating concrete specimens and concrete equivalent mortars (CEMs) with/without 15% natural zeolite and 8% silica fume with a total binder content of 380 kg/m3 and a constant water to cement ratio of 0.45 were fabricated. limestone powder (LP) is also used as an inert filler in all SCC/CEMs. Additionally, both the conventional and SCC mixes were subjected to these durability tests to compare their performance. After 7 days of curing in a saturated calcium hydroxide solution, all of the specimens were subjected to three exposure conditions (tidal, splash, sub-merged) for 28, 90 and 180 days of testing ages. After taking fresh property testes of mortar/concrete samples by SP demand, slump flow, visual stability index, J-Ring, T50, V-funnel tests, several standard hardened property and durability tests were investigated by mortar/concrete compressive strength, chloride permeability, concrete electrical resistivity, mortar capillary water absorption and porosity tests. Moreover, the degree of sulfate attack was evaluated by measuring the expansion of mortar prisms. Traditionally, the extent of sulfate attack is quantified by the expansion of prismatic bars completely submerged in sulfate solution and this exposure regime used to evaluate sulfate attack is not typically representative of that encountered in the field. Wherefore, in this investigation, prismatic bars were placed in different conditions mentioned and exposed to simulated seawater solution then expansion values evaluated. In addition, a reduction in compressive strength of all specimens was denoted by the strength differential factor (SDF). Results demonstrated that the incorporation of SF with NZ mixes in different exposure conditions led to the lowest absolute value of SDFs in all of the simulated-testing environment. Conversely, the lowest level of compressive strength at all testing ages was obtained for ternary blended cements (PC+LP+SF). Therefore, it can be concluded that SF has a negative effect on the compressive strength of SCC exposed to Persian Gulf seawater solution. This is attributed to the Mg-oriented sulfate attack which was more deleterious in SF ternary blended cements. All in all, the results were obtained from a laboratory set-up and indicated that when the durability properties of the concretes in such environments were taken into account, the quarterly use of zeolite and silica fume (PC+LP+SF+NZ) provided the best performance in all exposures. Furthermore, self-consolidating concretes and mortars performed better than normal types. Besides, it is concluded that splash zones affect concrete specimens more harshly than other conditions.