Development of Waterproofing Agent for Cement Soil Blocks from Low Density Polyethylene Wastes

Abstract

Low density polyethylene (LDP) is an essential element of industrialization and socio-economic development of a country. This is due to the universal use of low density polyethylene in other sectors of the economy. However, the problem arises from the management of LDP waste. If burned, LDP infuse the air with toxic fumes which have been linked with cases of cancer. When animals, fish or birds ingest LDP, they eventually die due to its indigestibility. When LDP is littered, it is carried by wind and rain storms and it clogs drainage and sewer lines. The current methods for managing LDP waste materials which include injection moulding, blow moulding and film moulding are inadequate. About 2,000 tons of LDP end up into the waste stream every month in Kenya. This study sought to develop a method for converting LDP into waterproofing agent for cement soil blocks (CSB‟s). Red soil was stabilized with cement and then compressed to make CSB‟s. Through heating, LDP was liquefied and the melt applied on CSB‟s through immersion. The LDP melt formed a uniform coat on CSB‟s after cooling. When the melt was put in an air tight container and allowed to cool at room temperature for 24 hrs, it solidified. Kerosene was added in to the LDP melt to stop solidification after cooling to room temperature at the ratio of LDP : Kerosene; 1 : 2 v/v. Since the improved melt dry film easily peeled off, long drying oil alkyd resin was added at the xxiii ratio of LDP : Kerosene : resin; 1: 2 : 3 v/v. The resulting dry film was transparent. To increase its hiding power, red iron oxide was added to the improved melt until the optimum pigment volume concentration (PVC) was achieved. This was achieved by establishing the scattering coefficient of the dry films of the improved melts. The improved melt with the highest hiding power was given by LDP : Kerosene : Resin : Red iron Oxide; (1 : 2 : 3) : 0.2 m/m. This formulation had 23.1 % pigment volume concentration, 86.7 μm scattering coefficient, 34.7 m2/l spreading rate, 0.0288 l/m2 usage rate, 9.66 Ksh/m2 per hiding power, 335 Ksh/l and 40 μm opacity. It was free of gel, coarse particles and skin. It produced a homogenous product of uniform consistency after stirring manually, was easy to brush, had satisfactory flowing, spreading and leveling properties, its dry film had no signs of sagging, running and had no brush marks. It did not exhibit any cracking or colour fading when tested for resistance to accelerated weathering. CSB‟s coated with this formulation did not absorb water after immersing them in water for 30 days. The improved melt (LDP : Kerosene : Resin : Red iron Oxide; (1 : 2 : 3) : 0.2 m/m) was reformulated to investigate the compromise between improving opacity and increasing formulation costs. This was done by using constant amount of red iron oxide while varying LDP, kerosene and resin. The best formulation was given by LDP : Kerosene : Resin : Red iron Oxide; (1 : 2 : 57) : 0.2 m/m. This formulation had 17.1 % PVC, 116.7 xxiv % volume solids, 46.7 m2/l spreading rate, 21.4 l/m2 usage rate, 5.9 μm scattering coefficient, 528.5 Ksh per liter and cost per hiding power of 11.3 Ksh/ m2. The formulations developed had a mean of 10.6, standard deviation of 0.5 and coefficient of variation of 0.05. Since their coefficient of variation was less than 1, the cost of covering a given area did not change significantly. However, the cost will change if price of any of the raw materials changes. LDP : Kerosene : Resin : Red iron Oxide; (1 : 2 : 57) : 0.2 m/m formulation gave the desired waterproofing agent for protecting CSB‟s.