Ultra-lightweight Concrete Containing Expanded Poly-lactic Acid as Lightweight Aggregate

The environmental impact of using petroleum products has become a serious issue nowadays. This paper is about the possibility of producing ultra-lightweight concrete by using bio-polymer aggregate as a replacement for petroleum polymer. Expanded poly-lactic acid (EPLA) and Expanded Vermiculite (EV) are used as aggregate in producing biopolymer concrete. In total, five concrete mixtures are designed with varying EPLA and EV contents. The cement content and effective water-cement ratio are kept constant. The EV aggregate was replaced with EPLA aggregate in the ratio of 20%, 40%, 60% and 80%. Three types of curing conditions were used. The mechanical properties, thermal properties, electrical properties of biopolymer concrete were assessed and analysed. The microstructure of concrete was assessed after 28-days and one year. It was found that the properties of EPLA concrete are mainly influenced by the volume of EPLA and curing conditions. The chemical reactivity of EPLA significantly changes the hydration products of concrete and causes concrete carbonation as well as the conversion of hydration products to more calcium carbonate. However, at the long-term investigation (after a year) the more C-S-H gel was found. Furthermore, EPLA aggregates shrunk and lost their strength in the alkaline environment of cement.