Investigation the effect of steel fibers and coarse aggregate ratio on self-compacting concrete properties

The ultimate goal of concrete as the most important and most used building material is the durable resistance properties. Self-compacting Concrete, as an option to solve the major problems of conventional concretes, has a higher cost due to the use of special additives and aggregates size. Also, the presence of fine grains increases the cracking potential of the concrete. The aim of this paper is to assess the effect of coarse aggregate ratio and steel fibers on the properties of self-compacting concrete (SCC). For this purpose, 27 SCC mixtures with C/T(coarse aggregates as a fraction of the total combined aggregate mass) for 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35% and 30% and 12 SCC mixtures containing hook end steel fibers with volume fractions of 0%, 0.5%, 1.0%, 1.5%, 2.0% and 2.5% were prepared. The effect of C/T ratio on the fresh properties and mechanical properties of SCC was studied. The test results indicated that aggregate with C/T ratio for 50% has the best fresh and hardened properties. With the change in fiber ratio from 0% to 2.5%, the slump flow, blocking and segregation ratio are increasing, while in the fiber ratio above 2%, the self-consolidation property is lost. Fibers increase the tensile strength above than 40 % and decrease shrinkage cracking more than 50%. Fiber has no positive effects on compressive strength. According to the results, the best percentage of hook end steel fibers which can be recommended for self-compacting concrete is 1.5%.