The Effect of Polyvinyl Alcohol (PVA) on the Mix Proportion of Oil Palm Shell (OPS) Concrete C.C.Thong 1,a , D.C.L. Teo 2,b and C.K. Ng 3,c 1, 2, 3 Universiti Malaysia Sarawak, 94300, Kota Samarahan, Sarawak, Malaysia a thong_cc38@hotmail.com, b tdelsye@feng.unimas.my, c ckng@feng.unimas.my Keywords: Agricultural waste, Polyvinyl alcohol, Mix proportion, Slump value, Compressive strength. Abstract. Oil palm shell (OPS) is a renewable resource obtained from agricultural solid waste after the extraction of palm oil. It has been previously reported that OPS can be used as a coarse aggregate substitute in the manufacture of structural lightweight concrete. Since OPS is an organic material, its properties may degrade after a certain period of time unless pre-treatment is applied on the aggregates. Polyvinyl alcohol (PVA) can be used to treat the OPS before being incorporated as coarse aggregates in concrete. It has been determined that the use of PVA as pre-treatment enables an improvement to the properties of raw OPS aggregates and consequently the resulting concrete. In this research work, the effect of PVA as pre-treatment on OPS aggregates on the mix proportion of OPS concrete was investigated. The results show that there was an increase in the slump values of the OPS concrete made with PVA treated OPS aggregates. The 28-day air-dry density and compressive strength of PVA treated OPS concrete slightly increased as compared to raw OPS concrete. Introduction In building construction, the self weight of the concrete element represents a substantial amount of the total dead load to be carried on the structure. By reducing the dead weight of a concrete structure, it can lower the load bearing capacity and consequently, a reduction in the size of the foundation. This also enables a reduction to the manpower required and increases productivity [1]. The reduction of concrete weight can be achieved through different methods, such as the use of smaller sections, hollow core concrete and by incorporating lightweight concrete. In the past few decades, extensive research have been conducted to investigate the use of oil palm shell (OPS) which is a by-product from the agricultural industry as lightweight coarse aggregate in making structural lightweight concrete [2-5]. Results have shown that concrete produced from OPS aggregates enables a reduction of approximately 17% to 19% of the self weight as compared to normal concrete [3,5] and it also achieves the minimum compressive strength requirement of 17 MPa for structural lightweight concrete as stipulated in ACI 213R-87 [6]. Mannan et al. [7] reported that polyvinlyl alcohol (PVA) can be used to improve the OPS aggregate properties and the engineering properties of OPS concrete. PVA can also be used in wood preservatives to improve the resistance against fungal decay and termite attack [8]. OPS, which is organic in nature may decompose and its properties may degrade after a certain period of time. Therefore, it is believed that the use of PVA as pre-treatment can be used as a means to increase the resistance against fungal decay and termite attack and subsequently improve the properties of raw OPS aggregates and the resulting concrete properties. This research aims to investigate the effect of the PVA pre-treatment on OPS on the properties of concrete (slump, 28-day air-dry density and compressive strength), by comparing the test results of the raw OPS concrete with the test results of an identical mix proportion but with full substitution of the raw OPS aggregates with the PVA treated OPS aggregates.