Sustainable production of eco-friendly roofing tile using methyl ester residue as the alternative binder – A preliminary study

Making full use of industrial by-products is an effort to achieve ‘zero waste’ and promote greener development. Methyl ester residue (MER) is a waste commonly found in oleochemical manufacturers, such as palm oil mills. Contrary to conventional cement and clay, MER was employed as an alternative binder to fabricate a novel eco-friendly roofing tile, henceforth referred to as MER-RT. Parameters tested were transverse strength, water absorption, sulfate resistance, and fire resistance. During the optimization phase, a range of 6–11% of MER was mixed with a fixed composition of fly ash and fine sand, compacted and cured at 190° C for 12–48 hours. Considering the electrical energy consumption, the optimal curing duration chosen was 24 hours as this MER-RT achieved a dry transverse strength of 4112 N whereas curing for an additional 18 hours further contributed to only 16% strength gain. The optimal MER-RT was found to contain 10% MER as it showed the highest dry transverse strength (6410 N), the highest wet transverse strength (3681 N) and the lowest water absorption percentage (2.67%), meeting the American Society for Testing and Materials (ASTM) standards. Besides exhibiting minimal corrosion under the sodium sulfate test, the optimal MER-RT was non-flammable and did not undergo structural changes when exposed to fire. The study reveals the potential of both MER and fly ash as green binders and fillers for roof tiles, despite their origins as industrial waste.