Improvement of the Behavior of Concrete by Substitution of Sand by Oil Palm Fibers: Effects of Fiber Content and Curing Conditions

Abstract

This work investigates the use of oil palm natural fibers—available as agricultural waste in Cameroon—as reinforcement and partial sand replacement in concrete. The raw materials used include palm fibers collected in the locality of Okola in the central region (Yaoundé - Cameroon), which were treated with soda ash at a temperature of 105°C, gravel from the local quarry in Logbadjeck (near Edéa-Cameroon), sand from the river Dibamba (near Douala-Cameroon) and the cement produced in Cameroon. The chemical and physico-mechanical characteristics of fiber-reinforced concrete were studied. The concrete was formulated according to the method of Dreux Gorisse by substituting sand with oil palm fibers at varying contents, 0% (BT), 0.5% (BF0.5), 0.6% (BF0.6), 1% (BF1) and 1.5% (BF1.5). The hardened concrete obtained was subjected to tests to determine their density, water absorption rate, compressive and tensile strength at 7, 14, and 28 days. It was found that the density decreases with the increase of fibers while the rate of water absorption increases. In addition, the consistency class and slump of fresh concrete vary depending on the percentage of fibers: BF0.5, BF0.6, and BF1 are plastic while BF1.5 is firm. Regarding the compressive strength at 28 days, it goes from 26 MPa for BT to 28.5 MPa for BF0.5 and gradually falls from 23.5 MPa for BF0.6 to 22.5 MPa for BF1.5 passing through the value of 23 MPa for BF1. Concerning tensile strength, this resistance increases according to the fiber content, which normally, was predictable. It goes from 2.06 Mpa for the 28 days BT to 7.5 Mpa for the 28 days BF1.5, which represents an improvement of more than triple the value of the basic resistance. Thus, fibered concrete has better mechanical strength for the dosage at 0.5% of fibers. Beyond this dosage, the resistance gradually decreases with the increase of the rate of the fibers, even if it remains always higher than that of BT: this shows that the addition of treated fibers substantially improves the mechanical properties of the concrete. These fibered concretes can be recommended for works requiring high mechanical strengths and relatively low self-weights, despite a decrease in workability which, for the rest, can be compensated by the use of a plasticizing additive.