Experimental Evaluation of Rubber-Plastic Solid Sandcrete Blocks under Marine Water Exposure

Abstract

This study experimentally evaluates the performance of solid sandcrete blocks incorporating recycled polyethylene terephthalate (PET) plastic and crumb rubber as partial replacements for fine aggregate under marine water exposure. A Taguchi L9 orthogonal array was employed to design nine mixes, with replacement levels ranging from 0% to 15% for each waste material. The blocks were tested for water absorption and compressive strength after 14 days of curing.

Results indicate that the inclusion of these hydrophobic waste materials significantly enhances water resistance; a mix with 20% plastic and 20% rubber reduced water absorption by 32% compared to the conventional control block. However, a substantial trade-off was observed in compressive strength, which decreased significantly with increasing waste content. All modified mixes failed to meet the Nigerian Industrial Standard (NIS 87:2004) for load-bearing blocks (3.45 MPa), with strengths falling as low as 0.94 MPa.

Statistical analysis identified an optimal mix with 7.5% plastic and 7.5% rubber, offering a balance of improved durability (9.12% absorption) and a compressive strength of 1.85 MPa. The study concludes that while these rubber-plastic sandcrete blocks are unsuitable for structural applications, their superior resistance to water ingress makes them a viable, sustainable material for non-structural applications in marine environments.