Structural, economic and environmental feasibility of plastic load-bearing walling and roofing system for low-income housing

[摘要] ENGLISH ABSTRACT: The lack of adequate housing becomes an increasing concern as the human population increases, which isnot only restricted to Africa, but worldwide. With the world becoming more environmentally aware, the aimtowards more sustainable development has become more essential. This results in alternative buildingtechnologies (ABT's) being investigated to address the backlog in housing.This study investigates plastic materials as structural elements in low-income housing to address the housingbacklog in a structurally stable, cost efficient and environmentally sustainable manner. The viable plasticmaterials that were identified are FFC (foam-fibre composite) and WPC (wood-plastic composite) asstructural elements and EPS (expanded polystyrene) as a core infill panel.Material parameters were obtained experimentally which were used in a numerical analysis to validate thestructural stability of a modular WPC housing unit. The experimental work includes a direct compression,direct tension, compressive creep and a four-point bending test for the WPC. With the sandwich panels apush-though shear and four-point bending test were done. The compressive strength of the EPS as well as arelative bond strength of the selected adhesives was also tested. Furthermore, a comparative study wasconducted on the fire performance (fire rating), cost efficiency as well as the environmental sustainability ofthree housing units constructed of FFC, WPC and block and mortar, respectively. In terms of structuralstability, a modular plastic housing unit was devised and validated by both experimental work and plasticmaterial investigations which showed that WPC can be used for load-bearing walling (with EPS as core infillpanel), roofing and flooring systems.From the comparative study, it was found that the fire rating of the block and mortar housing unit met therequirements of 20 and 30 minutes for the internal and external walls, respectively, prescribed by SANS10400-T (2011). The fire rating of the block and mortar housing unit was met in terms of integrity, insulationand stability. The two modular plastic housing units, however, only met the fire rating in terms of integrityand insulation, but failed to meet the requirements in terms of stability. The approach used to determine thefire behaviour of a housing unit is not as accurate as the physical fire test, since assumptions are made interms of the fire properties. However, the approach gives an indication of the fire performance of a housingunit.FFC and WPC are laminated with PVC (polyvinyl chloride) which emits hydrochloride acid (HCl), whenburning. Hydrochloride acid is a toxic gas. Thus, according to one of the minimum norms, stipulated by theNHBRC Home Building Manual and Agrément, an adequate housing unit should not emit harmful gasses.Although these regulations are not mandatory, in terms of this, WPC and FFC are not viable buildingmaterials for an adequate housing unit, especially when human behaviour and smoke control are considered.However, this aspect can be improved by adding additives to control, and in some cases prevent, smokeproduction.The comparative study also indicated that the cost efficiency of the FFC housing unit is comparable to that ofthe block and mortar design. The modular WPC housing unit has a cost which is substantially greater thanthat of the FFC as well as the block and mortar housing units. The modular plastic housing units, FFC aswell as WPC, typically utilise unskilled labour to construct a housing unit, which can lead to the socioeconomicconditions of a community being improved by means of job creation. Due to the relative ease ofconstruction of a modular plastic housing unit as well as a construction period of approximately three days,the demand for housing can be reached at a more rapid pace than by using conventional methods.In terms of the environmental sustainability, the plastic materials showed less negative environmentalimpacts as well as improved energy efficiency compared to the block and mortar unit.

[发布机构] Stellenbosch University