Study on the effects of highly active pozzolanic admixtures and mixed fibers on the properties of high-performance concrete using southern raw materials

Abstract

This paper presents the results of research on the use of highly activity puzzolanic admixtures Silicafume and fly ash (FA) of Phu My thermal power plant with large concentrations of southern raw materials, steel fiber (SF) and Polypropylene fiber(PP) to produce high performance concrete (HPC). This type of concrete can achieve a 28-day design compressive strength of more than 80 MPa, however, there are actual samples that reach over 100 MPa. Research on concrete mixes at mixing ratios of Silicafume Additive 10%, 7%; Fly ash 40%, 50%; Steel fiber volume is 0,4%; 0,8%, 1,2%; The PP fiber mixing ratio is 1,2%, and the mixed gradation is 0,6% SF and 0,6% PP. It was found that when adding 7% Silicafume and 50% fly ash, the concrete mixture had quite good flexibility reaching 18cm and high compressive strength (102,8MPa). When adding steel fibers and PP fibers to the concrete mixture, the slump decreases, especially PP fibers decrease sharply from 18cm to 5cm; Compressive strength and tensile strength when pressed and split at 28 days also increased by 9% to 14% compared to samples without fibers; Water absorption also decreases sharply. The study suggests that the appropriate mixing ratio of HPC concrete is Silicafume 7%; fly ash 50%; 0,6% SF and 0,6% PP to simultaneously meet the criteria of workability, strength, water absorption and cost.