Influence on Hemp Fiber Treatment of Natural Fiber Reinforced Concrete Properties

Abstract

This research aims to use hemp fibers, a natural reinforcing material, as an admixture in concrete. The comparison of the treatment of natural hemp fibers with alkaline chemicals such as calcium hydroxide (Ca(OH)2) and sodium hydroxide (NaOH) at a concentration of 2 M with untreated fibers (natural fiber) was studied hemp fibers were added at 1, 2 and 3 percent by weight of the binder. The concrete ratio was 1:2:4 (cement: sand: coarse aggregate) of all 3 parts and the w/c ratio was 0.67 (compressive strength 180 kg/cm2). The mechanical and physical properties such as fresh concrete slump, compressive strength, flexural strength, density, and water absorption were tested at 7, 14 and 28 days to determine the properties of natural fiber-reinforced concrete that are suitable for use.

The test results of all 3 parts of mix ratios showed that the average slump of fresh concrete was 9.5 cm, the difference from the allowable slump was -3.5 %, the compressive strength was between 105.3 and 226.0 kg/cm2, the flexural strength was between 137.2 and 150.9 kg/cm2, the density was between 2,399.3 and 2,459.0 kg/m3, and the water absorption was between 1.6 and 4.2 % at 28 days. when compared to the control mixture that did not contain hemp fibers. The most suitable ratio is one in which 3 % of the fiber content of all 3 parts is mixed. It was also found that the use of alkaline chemicals helped to roughen the fiber surface, increase adhesion and increase the adhesion between the cement paste and the fiber surface, which had better properties than hemp fibers that were not treated with chemicals.