The Durability Of Alkali Activated Slag Concrete Reinforced By Polypropylene Fiber

As an environmentally friendly building materials, alkali activated slag concrete could improve the utilization of industrial waste. Compared with the Ordinary Portland cement concrete, it contain the characteristics of high early strength, excellent corrosion resistance and durability. However, alkali activated slag concrete had poor carbonation and shrinkage resistance, which restricted its application and promotion. As a new type of organic fiber material, Polypropylene fiber had high elastic modulus, ultimate tensile and strength, which was helpful for improving the shrinkage cracking of alkali-activated slag concrete.According to the test methods of durability of concrete, the effects of polypropylene fibers on the durability of alkali slag concrete had been investigated and analyzed. The types and numbers of hydration products and microscopic pore structure had been meansured by XRD, DSC-TG, SEM-EDS and MIP. At the same time,the relationship between slag concrete durability and the type, quantity, microscopic pore structure correlation of hydration products was studied. Results indicated that: 1) Alkali activated slag concrete showed excellent performance of chloride penetration1) Alkali activated slag concrete showed excellent performance of chloride penetration resistance and chemical attack, but weak shrink properties and anti-carbonation, which seriously affected the safety and performance of concrete structures. With the addition of polypropylene fiber, the durability of alkali-activated slag concrete became more balanced. When incorporated into polypropylene fibers, it improved the abilities of concrete anti hydrochloric acid and magnesium sulfate erosion, but it reduced the ability of resistance chloride ion penetration, sodium hydroxide and water erosion resistance. When the fiber replacement was 0.9 kg / m3, the shrinkage and carbonation depth of alkali-activated slag concrete decreased. when the rate of fiber increased to 1.8 kg / m3, the performance of concrete constantly optimize.2) Polypropylene fibers had stable chemical property which did not affect the types of hydration products. And its hydration products were still mainly CSH gel and un-hydrated slag. Meanwhile, polypropylene fiber could significantly improve the 270 d ages hardening paste porosity, median pore diameter and pore distribution.The results of micro-porous structure test demonstrated that the porosity of the paste mixed with 0.9 kg/m3 fiber was reduced by 7% compared with the blank.