Investigation of the quality of plastic-sand composite bricks.

Abstract

Plastic pollution has become a global menace, with various initiatives inventing ways of repurposing plastic waste, one of which includes the use of plastic as a constituent of building materials. However entrepreneurial this idea seems to be, there is need to ascertain the quality of these materials that are being gradually introduced to the Uganda market. This research aims at investigating the quality of plastic-sand composite bricks. Plastic-sand composite bricks are made of molten plastic with sand as a filler material. Recycled Polyethylene terephthalate (PET) plastic was used since it comprises most of the plastic waste in Uganda hence it is readily available. The bricks were manufactured locally, using firewood as a source of fuel for melting the plastic. Different plastic to sand mix ratios of 1:1, 1:2, 1:3 and 1:4, were used. Representative samples were then obtained and laboratory tests carried out to ascertain the properties of the bricks. The average compressive strength of the bricks ranged from 5.39 MPa to 5.93 MPa for the different mix ratios, which satisfied the minimum requirement for both loadbearing internal walls and non-load bearing walls as per the Uganda Standard for burnt clay building blocks, US EAS 94. All the brick samples depicted water absorption values that were way lower than the recommended maximum of 10% by weight; with the experimental average values ranging from 0.65% to 1.71% for the different mix ratios. The optimum mix ratio chosen was 1:3 since the bricks made with this mix ratio had the highest average compressive strength of 5.93 MPa, with an acceptable average water absorption capacity of 1.64% by weight. A compressive strength test was also carried out on masonry wallettes constructed using these bricks, to model the performance of axially loaded masonry walls. The failure of the masonry wallettes was characterized by vertical cracks through the masonry units, with no defined cracks along the brickmortar interface, indicating an adequate bond and adhesion between the bricks and the mortar.