EXPERIMENTAL INVESTIGATION ON THE COMBINED EFFECT OF BAMBOO FIBER AND PARTIAL REPLACEMENT OF CEMENT BY KAOLIN ON CONCRETE PROPERTIES

Abstract

Concrete suffers from several drawbacks due to the pollution associated with steel production, high cost, low tensile strength, and low strain capacity that result in low resistance to cracks. In addition, the production of cement results in the depletion of natural resources and the consumption of huge energy and CO2 emissions into the environment that cause global warming and climate change. Researchers are becoming more interested in developing an alternate substance to partial cement created from industrial and agricultural wastes in order to solve the issue. Moreover, to balance the drawbacks of concrete like low tensile strength and low resistance capacity to cracks, the researchers found an alternative material to steel by using natural reinforcing material. This paper aims to investigate the effect of calcined kaolin (CK) particles as a partial replacement for cement (OPC) and a 37.5mm length of bamboo fiber (BF) as fiber reinforcement in C-25 concrete production. ACI 211.1 was used to design a grade of 25MPa. The concrete mixture was prepared by the combination of partially substituted cement with CK in different proportions (4%, 8%, and 12%) and BF as a reinforcement addition in different ratios (0.5%, 1%, and 1.5%) by total weight in C-25 grade concrete. The strength of modified and conventional concrete after 7, 14, and 28 days of curing has been tested. The complete silicate analysis by using AAS and morphological analysis by using SEM, XRD, and FTIR were investigated. The mechanical tests such as compressive, splitting tensile, and flexural strengths at 7, 14, and 28 days were investigated. In addition, durability tests like carbonation, water absorption, and sulfate attack tests were conducted every 28 days. Slump flow was also investigated. The test results revealed that the workability of mixtures showed a decreasing trend with an increase in the share of the CK and BF content in which the measured slump flow values ranged between 75 and 100 mm. Compared with the nominal concrete mix, the compressive strength of concrete increased with an increase in the share of the CK and BF combination from 4–8%CK and 0.5–1%BF, and decreased after 12%CK and 1.5%BF for the 7th, 14th, and 28th days, respectively. The reason for the increment should be that it was discovered that the CK is a suitable material for use as a pozzolana as it satisfied the minimum requirement given in ASTM C618 and bamboo reduces crack propagation in concrete. This gives the concrete a more dense and well-compacted microstructure than the control concrete. The reason for decreasing after the combination of 8%CK and 1%BF should be the high surface area and absorption of calcined kaolin and the balling effect of bamboo fiber, XVII respectively. The splitting tensile strength and flexural strength were increased at a mixture of 4% and 8% CK replacement and 0.5% BF addition, respectively. Overall, an optimal modified CK8BF1 mix with 8% OPC replacement by CK and a 1 % BF addition outperforms all other mixes. The results also showed that the maximum strength and durability were achieved by combined effects in comparison to all other concretes for all the curing days. The SEM analysis of concrete modified with the optimum concrete (CK8BF1) revealed a more densified and well-compacted microstructure than control concrete. An X-ray diffraction test was conducted on calcined kaolin pozzolanic material used to analyze its content ingredients. The XRD analysis of concrete modified with both CK and BF showed the existence of more phases, which are responsible for strength modification than the original concrete. In general, it was also observed that, from the compressive strength, the concrete satisfies its design strength up to 8% replacement level and 1% bamboo as an addition without compromising the performance of the concrete