The Effect of Fibres on the Compressive Ductility of Lightweight Aggregate Concrete

Abstract

The purpose of this thesis was testing the effect of different type of fibre reinforcements to the compressive ductility of lightweight aggregate concrete (LWAC). Concrete with density of about 1800 kg/m3 and compressive strength of about 40 MPa was used. The fibres used were two types of steel fibres with lengths of 35 and 60 mm and then basalt fibres with length of 45 mm.Eight full scale over-reinforced LWAC beams with length of 4,2m and cross-section of 0,2x0,3m were constructed with identical structural steel reinforcement but with different type of fibres added. The beams were then tested in a four point bending until failure. The deflection and top and bottom concrete strains were measured with inductive sensors and recorded in a test-log.Test results of these beams were compared to calculations with input values from testing of the compressive strength and oven-dry density from testing of concrete cylinders. Comparison of test results and calculations showed a generally good compliance.The fibres had positive effect on the ductility in compression. Even though they didn?t increase the load bearing capacity post-failure, they decreased the deflection rate considerably. This test indicated clear difference in effect of the steel fibres versus the basalt fibres to the compressive ductility.