Author(s): M. Kadonzvo, M Mohammed
Keywords: Cement blocks, Polyethylene Tetraphthalate (PET), Composite, Green construction
There is an increasing demand for housing in Ghana due to the increase in population growth . Consequently, millions of tons of materials go into the construction process. With the current population growth rate of Ghana and a population of 29.7M in 2018, one can predict the efforts required by the civil engineering and construction industry to meet infrastructural demand. The high population growth rate means that more land space and building materials needs to be churned into this ever-growing industry. This idea raises concerns over the need for efficient use of land and construction methods that point towards environmentally sustainable practices in construction. Research is ongoing in the field to look for better ways of building with the least possible negative impact on the environment. These better methods will define a new form of construction - green construction – which will be more environmentally friendly. On the same note of being ecologically conscious, several researchers have been raising awareness on the adverse impact of poor plastic waste management. Plastics are synthetic organic hetero-atomic polymers that are often synthesized in large quantities from oil, coal, and natural gas . They are generally non-biodegradable in the presence of enzymes or microbes . This raises environmental issues, since approximately 30% of worldwide production of plastics goes into food packaging and the making of detergents and chemicals, with the annual global economic growth of this industry being around 12% . One of the most commonly used forms of plastics is polyethylene tetraphthalate (PET). According to Albertson, approximately 140 million tons of human-made polymers, including PET, are manufactured around the world annually, with a utility rate of around 12% . Ghana Times argues that 250 tons of plastic packaging waste are produced daily in Ghana alone . Although PET can be degraded by chemical, photodegradation, thermal, and some sophisticated biodegradation techniques , there is a need to recycle it into other functional materials . To harmonize the ideas of green construction and sustainable waste management this study seeks to create a new breed of blocks that contains PET granules as part of the reinforcement. These new blocks would replace the traditional cement blocks, which are composites with cement as the matrix and sand as the reinforcement, and clay-based bricks. The conventional blocks and bricks are used for their aesthetic nature, high flexural strength, high compressive strength, fire protection, good porosity, sound attenuation, insulation, wear-resistance, and durability. The incorporation of PET into the blocks would go a long way to improve plastic waste management as plastic waste will be recycled into something useful. Moreover, the new breed of blocks will replace vitrified clay bricks thereby reducing carbon dioxide emissions that are associated with the vitrification of clay bricks. On the construction side, the question is; will the addition of PET significantly alter the mechanical and thermal properties of the blocks. This is a crucial question as any small change in these properties will affect the applicability of the blocks in construction. Therefore, this study will investigate whether the changes in the properties of plastic-cement brick will be better than those of the standard cement brick.
Civil engineering is one of the oldest fields of engineering that recently has begun to investigate the sustainable management of the environment. Research in this field is focusing on moving away from old methods of construction to new approaches that are environmentally friendly. Construction that has minimum negative impact on the environment is termed green construction. On the other hand, poor management of plastic waste poses a threat to the environment. Plastics like polyethylene tetraphthalate are non-biodegradable and very hard to handle as waste in the world and especially in Ghana. This paper describes how the need for better plastic waste management can be harmonized with the quest to find greener methods of construction. Traditional cement blocks are compared to a new breed of cement blocks that contain waste plastic as part of reinforcement. The mechanical and thermal properties of conventional blocks and those of the new blocks with different plastic compositions are compared using statistical methods and tools. There were statistically significant differences in the compressive strength, flexural strength, hardness and thermal conductivity of the newly engineered blocks.
From the statistical analysis and tests carried out, it can be concluded that there are statistically significant differences in the compressive strength, flexural strength, hardness, and thermal conductivity of the blocks. From the Kruskal Wallis test, both compressive and flexural strength for all the block types were similar. From the Tukey tests, there are statistically significant differences in the Hardness and Thermal conductivity of the blocks. For the hardness test, all except 2.25% of PET and 0.75% of PET, and 3.00% of PET and 1.50% of PET were different from the Tukey’s test. For the thermal conductivity, all except 0.00% of PET and 3.00% of PET were similar from the Tukey’s test. This shows that the mechanical properties are changed by the introduction of PET. The differences in mechanical properties of the blocks of different PET contents show that the amount of PET granules does change the structure of the material significantly. Scientifically, PET reinforced blocks could be used in low-stress bearing applications where aesthetics, durability and low thermal conductivity are of paramount importance.