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

Le Roux, Franel (2014-12)

Thesis (MEng) -- Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: The lack of adequate housing becomes an increasing concern as the human population increases, which is not only restricted to Africa, but worldwide. With the world becoming more environmentally aware, the aim towards more sustainable development has become more essential. This results in alternative building technologies (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 housing backlog in a structurally stable, cost efficient and environmentally sustainable manner. The viable plastic materials that were identified are FFC (foam-fibre composite) and WPC (wood-plastic composite) as structural elements and EPS (expanded polystyrene) as a core infill panel. Material parameters were obtained experimentally which were used in a numerical analysis to validate the structural 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 a push-though shear and four-point bending test were done. The compressive strength of the EPS as well as a relative bond strength of the selected adhesives was also tested. Furthermore, a comparative study was conducted on the fire performance (fire rating), cost efficiency as well as the environmental sustainability of three housing units constructed of FFC, WPC and block and mortar, respectively. In terms of structural stability, a modular plastic housing unit was devised and validated by both experimental work and plastic material investigations which showed that WPC can be used for load-bearing walling (with EPS as core infill panel), roofing and flooring systems. From the comparative study, it was found that the fire rating of the block and mortar housing unit met the requirements of 20 and 30 minutes for the internal and external walls, respectively, prescribed by SANS 10400-T (2011). The fire rating of the block and mortar housing unit was met in terms of integrity, insulation and stability. The two modular plastic housing units, however, only met the fire rating in terms of integrity and insulation, but failed to meet the requirements in terms of stability. The approach used to determine the fire behaviour of a housing unit is not as accurate as the physical fire test, since assumptions are made in terms of the fire properties. However, the approach gives an indication of the fire performance of a housing unit. FFC and WPC are laminated with PVC (polyvinyl chloride) which emits hydrochloride acid (HCl), when burning. Hydrochloride acid is a toxic gas. Thus, according to one of the minimum norms, stipulated by the NHBRC 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 building materials 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, smoke production. The comparative study also indicated that the cost efficiency of the FFC housing unit is comparable to that of the block and mortar design. The modular WPC housing unit has a cost which is substantially greater than that of the FFC as well as the block and mortar housing units. The modular plastic housing units, FFC as well as WPC, typically utilise unskilled labour to construct a housing unit, which can lead to the socioeconomic conditions of a community being improved by means of job creation. Due to the relative ease of construction 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 environmental impacts as well as improved energy efficiency compared to the block and mortar unit.

AFRIKKANSE OPSOMMING: Die tekort aan voldoende behuising raak ʼn kommerwekkende probleem in die huidige samelewing soos die wêreld populasie aan hou toeneem, waar hierdie probleem nie net tot Afrika beperk is nie. Soos die wêreld meer omgewingsbewus raak, word daar gestrewe na meer volhoubare ontwikkeling in die boubedryf wat aanleiding gee tot die ontwikkeling van alternatiewe bou tegnologieë (ABT’e) om die behuisingsagterstand op te los. Plastiese materiale word ondersoek vir hul gebruik as strukturele elemente in lae-inkomste behuising om die behuisingsagterstand in ʼn struktureel stabiele-, koste effektiewe- en omgewingsvolhoubare manier op te los. Geskikte plastiese materiale is geïdentifiseer as SVS (skuim-vesel samestelling) en HPS (hout-plastiek samestelling) vir gebruik as strukturele elemente en uitgesette polistireen is gebruik as ʼn invul paneel. Materiële eienskappe was eksperimenteel bepaal, wat in ʼn numeriese analise gebruik was om die strukturele stabiliteit van ʼn modulêre HPS behuisingseenheid te verifieer. Die eksperimentele werk sluit ʼn direkte druk, direkte trek, druk kruip en ʼn vier-punt buig toets in, wat uitgevoer is met HPS. Vir die saamgestelde paneel was daar ʼn druk-deur skuif en ʼn vier-punt buig toets gedoen. ʼn Druk toets met die uitgesette polistireen en ʼn relatiewe verband sterkte vir die geselekteerde gomme was ook getoets. Verder, is ʼn vergelykende studie gedoen op die vuur uitvoering (vuurbestand waardering), koste effektiwiteit en die omgewingsvolhoubaarheid van ʼn SVS-, HPS- en blok-en-mortel behuisingseenheid. ’n Ontwerp is bepaal en geverifieer deur beide eksperimentele werk en analitiese ondersoeke, wat gewys het dat HPS gebruik kan word as ʼn lasdraende muurpaneel (met uitgesette polistireen invul), so wel as ʼn dak- en vloer sisteem. Daar is gevind, vanaf die vergelykende studie, dat die vuur uitvoering van die blok-en-mortel behuisingseenheid voldoen aan die vereiste van 20 en 30 minute onderskeidelik vir die interne en eksterne mure, soos voorgeskryf deur die SANS 10400-T (2011). Die vuur waardering van die blok-en-mortel behuisingseenheid het in terme van integriteit, insolasie en stabiliteit voldoen. Die twee modulêre plastiek behuisingseenhede het erger aan die vuur waardering slegs in trems van integriteit en insolasie voldoen. Hul het misluk in die voldoening in terme van stabiliteit. Die benadering wat gebruik was om die vuur gedrag van ʼn behuisingseenheid te bepaal, is nie so akkuraat soos ʼn fisiese vuur toets nie. Dit is omdat vir die benadering aannames in terme van die vuur eienskappe gemaak is. Die benadering gee egter ʼn indikasie van die vuur uitvoering van ʼn behuisingseenheid. SVS en HPS is gelamineer met PVC (poliviniel chloried) wat hidrochloried suur (HCl) afgee wanneer dit brand. Hidrochloried suur is ʼn giftige gas. Volgens een van die minimum norms, gestipuleer deur die NHBRC Home Building Manual en Agrément, moet ʼn voldoende behuisingseenheid nie giftige gasse afgee nie. Al is die regulasies nie verpligtend nie, in terme hiervan, is SVS en HPS nie ʼn uitvoerbare boumateriaal vir ʼn voldoende behuisingseenheid nie, veral wanneer menslike gedrag en rook beheer aangespreek word nie. Nietemin, die aspek kan verbeter word deur die byvoeging van bymiddels om die rook produsering te verminder en in sommige omstandighede te voorkom. Die vergelykende studie het ook gewys, dat die koste effektiwiteit van die SVS-behuisingseenheid vergelykbaar is met die van ʼn blok-en-mortel behuisingseenheid. Die HPS-behuisingseenheid se koste is aansienlik hoër as die van SVS-en die blok-en-mortel behuisingseenheid. Die modulêre plastiese, SVS en HPS, behuisingseenheid maak tipies gebruik van ongeskoolde werkers om die behuisingseenhuid op te rug, wat tot ʼn verbetering in die sosio-ekonomiese toestande in ʼn gemeenskap kan lei, deur dat dit werk skep. Aangesien die modulêre plastiese behuisingseenheid met relatiewe gemak en in ongeveer drie dae opgerig kan word, kan die aanvraag tot behuising vinniger bereik word, as wanner die konvensionele boumetodes gebruik word. In terme van omgewingsvolhoubaarheid, het die plastiese materiale minder negatiewe omgewingsimpakte en is meer energie-doeltreffend in vergelyking met die blok-en-mortel onwerp.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/95939
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