Laboratory study of the effect of adding glass fibers on reactive powdered concrete

Reactive Powder Concrete (RPC) is a type of ultra-high-performance concrete (UHPC). Reactive powder concrete is composed of very fine aggregates (Cement, fine aggregate, quartz powder and Silica sand), strong superplasticizers, and a small amount of water. Improvement of microstructure, elimination of coarse aggregate, particle packing, and toughness enhancement are the main principles of RPC development. Reactive powder concrete has a high modulus of elasticity and low water absorption and also has a high compressive strength. Reactive Powder Concrete contains high amounts of cement. This high ratio increases the production cost of this concrete in addition to causing issues such as high hydration temperature and concrete shrinkage. In this study, due to the difference in material and composition of materials in Iran with other countries, one should use 5 ratios of silica sand to cement including 1, 1.1, 1.2, 1.25, 1.3 and, then, add 4%, 5%, and 6% of the volume of concrete Fiberglass to each ratio. Increasing the sand to cement ratio up to 1.2 can improve the concrete behavior by reducing the amount of cement used. Moreover, According to the SEM images, by increasing the sand-cement ratio to 1.2 with the improvement of concrete microstructure, the compressive strength increased..On the other hand, in this sand-cement ratio, microcracks were reduced compared to the sample with a sand-cement ratio of 1, and water absorption of concrete was reduced.Moreover, the tensile behavior of RPC must be improved using another material due to the limit set on the largest grain size in it. Adding glass fibers at the rate of 4-5% of concrete weight to the mix design and converting reactive powder concrete to composite reduces the number of microcracks, which improves the microstructure of concrete. As a result, the behavior of concrete is enhanced against tension and flexure. Moreover, with the addition of glass fibers, the behavior of concrete against water is strengthened and the water absorption of reactive powder concrete sample armed with glass fibers is appropriate.