Studying the Effect of Adding Carbon Fibers on Mechanical Properties of Normal and Self Compacting Concrete

Abstract

Concrete is a brittle material with low tensile strength and low strain capacity that lead to low resistance to cracking. The aim of this work is studying the effect of adding carbon fibers on mechanical properties of two types of concrete, normal and SCC. This study included (8 mixtures) and it is divided into two parts, the first part represents the normal concrete mixture containing reference mix with proportions (1:1.55:1.74) and (3 mixtures) containing different ratios of chopped carbon fiber which (0.5%, 1%, 1.5%). The second part is to produce a mix of SCC after several trial mixes, the properties that satisfied the SCC requirements in terms of filling ability, passing ability and segregation resistance, have been reached with proportions of (1:1.8:1.5), and choose the mix of reference after a number of tests such (Slump Flow), (T500 slump flow), (V-funnel), (V-funnel after 5minute) and (J-ring). As well as the production of (3 mixtures) containing different volumetric ratios of chopped carbon fiber which (0.3%, 0.4%, 0.5%) has been studying the effect of adding carbon fiber for the fresh properties as well as some of mechanical properties in the hardened state. Specimens that have been found are 288 specimens includes 72 cubic with dimensions (100) mm for compressive strength test, 72 cylinder with dimensions (100*200) mm to test the splitting tensile strength, 72 prism with dimensions (100*100*500) mm to test the flexural strength and 72 cylinder with dimensions (150*300) mm to static modulus of elasticity test. All mixtures were tested in ages of (7, 28 and 56) days. The results showed that the addition of carbon fibers leads to a remarkable decrease in workability of concrete and increases with increasing carbon fiber content. The results indicate that the addition of carbon fiber improve mechanical properties of normal concrete for the mixture containing fibers (1%), which is the better ratio where increased the splitting tensile strength , flexural strength and static modulus of elasticity about (50%, 38%, 4%) respectively. As for the compressive strength was there a slight decrease about (1.5%). As well as the results showed the possibility of producing SCC reinforced carbon fibers with proportions (0.5%), where increased the compressive strength, splitting tensile strength, flexural strength and static modulus of elasticity by about (6%, 16%, 18% , 8%) respectively.