Optimization of the compressive strength of hair fiber reinforced concrete using central composite design

Abstract

Abstract In society today, improper waste disposal brings about numerous problems. One of the most common residual wastes found in the municipal solid waste is human hair. This waste, which is evidently continuing to accumulate in disposal streams poses a threat if not disposed properly. Several studies have been done in the search for possibilities of incorporating hair to construction materials. In this study, the compressive strength of Hair Fiber Reinforced Concrete (HFRC) was studied aiming to find the combination that would yield the optimum compressive strength. A parametric study on the effect of amount of hair (1%, 2% and 3%) as well as length of hair strand (0.5-inch, 1 inch and 1.5 inch) on the compressive strength of HFRC was done. The results of the parametric study were used to find the optimum compressive strength. Utilizing the Central Composite Design (CCD) of Response Surface Methodology (RSM), a mathematical model was produced relating the parameters and the combination of parameters that would yield the maximum compressive strength. Based on the results, the mathematical model obtained a Coefficient of Regression of 0.9807 showing that the probability plot of the residuals fits the regression line. As generated by the mathematical model, a combination of 3.2% amount of hair by volume of concrete and a hair strand length of 0.752 inch will yield an optimum compressive strength of 38.15 MPa.