Engineering properties of rubberised concrete incorporating palm oil fuel ash

Abstract

The utilisation of waste materials and by-products is a partial solution to environmental and ecological problems. One important recent development, in the field of concrete technology, is the utilisation of waste materials and by-products in the construction industry, as aggregates in the production of various types of concrete. Agro-waste materials, such as palm oil fuel ash (POFA), show a great potential ability to be utilised as a pozzolanic material in concrete. The problem of the rising costs of construction materials, coupled with evident environmental degradation, and the need to improve concrete properties; especially in terms of acoustic properties, has stimulated the necessity to incorporate tyre-rubber aggregates (TRA) and POFA in concrete. Rubberised Concrete (RC) is produced by replacing a volume percentage of the traditional coarse and/or fine aggregate with tyre-rubber particles. TRA has been utilized in various gradations from used vehicle tyres and POFA has been replaced partially as cementitious material. This research investigates the wide range of physical, mechanical and acoustic properties of concrete containing recycled TRA and POFA to assess its suitability as a construction material. The influence of factors, such as rubber aggregate content, size, shape and type of rubber particle, was also considered. TRA is classified into three groups, namely fine fibre (R1), fine granular (R2) and coarse granular (R3). The concrete mixture is designed based on ACI 211-91. The TRA component of the mixture is replaced in 5% to 30% by volume. The results of this study show that the best proportion of POFA is 20% with a water-binder ratio of 0.38; which improves the 28-day concrete strength. The results show that despite a great loss in strength with increasing TRA replacement, this type of concrete is acceptable for various structural applications requiring medium to low compressive strengths. It is found that for the same volume of rubber (coarse and fine TRA), coarse rubber particles increase air content, decrease compressive, indirect tensile, and flexural strengths, and improve the deformability of concrete, compared to concrete containing fine TRA. Furthermore, the modified rubberised concrete exhibits superior acoustic properties. The results of sound absorption coefficient and sound transmission loss show that the coarse aggregates have more influence on improving the soundproofing properties by up to 42.5% with 30% TRA incorporation. These attributes make rubberised POFA concrete a potential candidate for application in a promising flooring system that is cost-effective and has increased sound-proof properties. The possible quantities of concrete produced worldwide for such applications would ensure the viability of this product. Therefore, this type of concrete shows promise in becoming an additional sustainable solution for tyre-rubber waste management.