The mechanical properties of high and normal-strength of fly ash concrete strengthened by polypropylene and steel fiber

Abstract

Concrete technology has developed rapidly due to the high demand for advanced infrastructure facilities in which concrete has become the most frequently used material. Due to high CO2 emission caused by cement utilization in concrete production, partial cement substitution by pozzolanic material such as fly ash will be beneficial for the environment. Despite the concrete high demand for infrastructure facilities, the concrete needs attention on its lower tensile strength, especially in high-strength concrete. Therefore, this paper presents a study on the effect of different types of fiber on the strength properties of fly ash concrete. The method applied in this study is an experimental program by manufacturing specimens with compression strength design variations of 25 MPa for normal-strength concrete and 45 MPa for high-strength concrete. In addition, 0.66% steel fibre BWG21 (SWF) by weight of concrete and 600 g/m3 polypropylene fibre Sika Fibre-12 (PPF) were used. Moreover, 20% fly ash as a partial substitution for cement was used to address the green concrete issue. The testing programs include the workability test for fresh concrete, compression strength test and splitting tensile strength test for cylinder concrete, and flexural strength test for the concrete beam. Besides the workability test of fresh concrete, the other testing programs were conducted after the concrete curing stage at 28 days. The test result shows that cement substitution of 20% by weight of fly ash and the addition of fibre can meet the design strength of concrete both for 25 MPa and 45 MPa. Even though this research confirms that steel fibre gives higher strength properties than polypropylene fibre, polypropylene fibre is easier to work with in the manufacturing stage. Moreover, this finding support reducing greenhouse gas release into the atmosphere coming from the construction industry through cement replacement up to 20%.