Development of sustainable masonry units from flood mud soil: Strength and morphology investigations

Abstract

In the aftermath of the mega flood 2014–2015 event on the East Coast of the Peninsular Malaysia high piles of debris and mud were found deposited on the affected area. The cost of cleaning and removal of the debris and mud was extremely high. Utilisation of the flood mud soil as an aggregate to develop sustainable masonry units could be possible through chemical stabilisation to increase the strength of the soil. Biomass silica (BS) stabiliser was used to enhance the engineering properties of the flood mud. The flood mud soil sample was taken from Kuala Krai, Kelantan, after the flood event, which occurred during December 2014 and January 2015. The Unconfined Compressive Strength (UCS) of unstabilised samples and samples stabilised using 3%, 5% and 10% stabiliser, was measured after three and seven days of curing. The stabiliser could increase the soil strength up to 10-fold (1330 kPa) of the unstabilised strength but was still lower than the strength requirement specified by British Standard Institute. An addition of 2% of cooking salt at 105 °C curing could significantly improve the UCS. Microstructural analyses via Energy-Dispersive X-ray spectrometry (EDX) and Field-Emission Scanning Electron Microscopy (FESEM) tests were undertaken to examine the influence of BS stabiliser, cooking salt and heat curing on UCS development. The additional cooking salt with heat curing caused the aggregation and enhanced the chemical reaction of the BS stabilised soil. The formation of Calcium Silicate Hydrate (CSH) and Calcium Aluminate Hydrate (CAH), as shown by white-coloured lumps, filled the pore spaces of the biomass silica stabilised soils. The aggregation and CSH and CAH products resulted in a dense and strong soil structure and subsequent strength development. This research indicates that the mixture of BS stabiliser and cooking salt can be used to manufacture mud-based masonry units as a sustainable construction and building material.