Influence Of Sulfate Environment Effect On The Tensile Strength Of Reactive Powder Concrete

Reinforced concrete structure in sulfate environment of northern region suffers the coupling effect of dry-wet cycle, freezing-thaw cycle and sulfate attack, which causes the weakening of the durability of concrete exacerbated and shortens the life of the structure seriously. Reactive powder concrete has remarkable durability, ultra-high compressive strength and tensile strength, especially suits for the design and protection of structure in sulfate environment. Therefore, tensile strength should be used to resist the tensile stress of component in the design of reactive powder concrete structure. So tensile strength has also become an important evaluation index of durability.In this paper, the durability of pre-loaded reactive power concrete under the coupling effect of freeze-thaw and dry-wet cycle was studied based on three concentrations of Na2SO4solution which were selected in advance. The splitting tensile strength is selected as the evaluation index of durability. The microscopic structural change and erosion product are also analyzed through SEM, EDS, XRD microscopic methods. Meanwhile, C60high performance concrete is selected for comparison. In addition, the research of reactive power concrete after the coupling effects of sulfate freeze-thaw cycle was carried out, in order to compare the damage degree of dry-wet cycle and freeze-thaw cycle. The main conclusions are as follows:1. Under the coupling effect of sulfate freezing-thaw and dry-wet cycles, the durability of reactive power concrete are far superior to the durability of high performance concrete. The splitting tensile strength of high performance concrete after6times coupling is2.3MPa, which decreases48.89%compared with the original. However, the splitting tensile strength of reactive powder concrete after8times coupling is13.5MPa, which decreases by31.47%. In addition, the variation of splitting tensile strength of them is different. The variation of HPC’s splitting tensile strength can be divided into two stages, namely, initial deterioration stage and strengthening stage.However, as for reactive powder concrete, it can be divided into three stages, which includes the initial deterioration stage, strengthening stage and s deterioration stage.2. According to the coupling effect of sulfate freezing-thaw and dry-wet cycles results, it can be concluded that the influence of Na2SO4concentration on the durability damage degree is5%>10%>0%. The reason is that the sulfate solution with high concentration is easier to form salt crystals, and it forms a blockage effect in the pore. So it is more difficult to permeate into the pore for the high concentration of sulfate solution. It can be seen from the microscopic test results that the sulfate erosion chemical reaction of5%Na2SO4solution is more complete. And the crystal has larger size and higher XRD diffraction peak intensity.3. Compared with the freeze-thaw and dry-wet coupling cycle, the durability of reactive powder concrete under the freezing-thaw cycle is more remarkable. And the strength loss under the freeze-thaw cycle is less. The strength loss of dry-wet cycle is calculated based on the strength loss of freezing-thaw cycle and coupling cycle, what’s more, the curve of calculated strength loss is given. After analyzing and comparing their strength loss, it can be concluded that the damage of dry-wet cycle is more serious than the freezing-thaw cycles.