THE EFFECT OF COCONUT FIBER ASH WASTE AS A PARTIAL CEMENT SUBSTITUTE IN FLOW CONCRETE

Abstract

Indonesia is a major producer of important food raw materials, such as sugar cane and coconut. Currently, Indonesia is the world's largest producer of coconut fiber, with approximately 3.27 million hectares of coconut plantations and a production of approximately 2.85 million tons. The coconut fiber is typically used for consumption, while the remaining fiber has the potential to become waste. The natural degradation process of this waste is relatively slow, leading to accumulation if not managed properly. Several previous studies have shown that coconut fiber ash contains oxide compounds, such as silica, alumina, and calcium, which can act as additives in concrete construction. The pozzolanic content of coconut fiber ash allows it to react with calcium hydroxide to produce calcium silicate hydrate (C-S-H), a compound that functions as a binder and contributes to improving concrete quality. In this study, coconut fiber ash was used as a cement substitute to evaluate its effect on the mechanical properties of flowable concrete, particularly unit weight and compressive strength, when used as a partial cement substitute. The test specimen used was flowable concrete with the addition of Sika-Viscocrete superplasticizer. The percentage of coconut fiber ash variations applied were 0%, 0.5%, 1.5%, 2.5%, and 4% of the cement weight. The test results showed that the highest unit weight was obtained at 2366.29 kg/m3 at 1.5% coconut fiber ash substitution, and the highest compressive strength value was obtained at 2.5% coconut fiber ash substitution, which reached 31.99 MPa.