International Journal of Sustainable Built Environment (2014) 3, 72–86 HOSTED BY Gulf Organisation for Research and Development International Journal of Sustainable Built Environment ScienceDirect www.sciencedirect.com Original Article/Research Conceptualisation and pilot study of shelled compressed earth block for sustainable housing in Nigeria C. Egenti ⇑, J.M. Khatib 1, D. Oloke 2 Faculty of Science and Engineering, Dept. of Architecture and Built Environment, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY, United Kingdom Received 25 December 2013; accepted 20 May 2014 Abstract Meeting the housing needs in Nigeria is a long-standing task, yet to be realised. The economy of the country, as most developing coun- tries, is ailing with limited resources. Energy and infrastructures are inadequate, yet the use of cement dominated the construction industry. Earth construction is a sustainable option to housing with inherent characteristics that should be desirable in the ailing economy of hot trop- ical environment in Africa. However, most Nigerians are skeptical of taking a low cost option with less modern effects and uncertain dura- bility. This research explores the issues relating to this problem and aims to bridge the gap between Nigerians and earth, which exists in abundance in Africa. The emerging concept from the survey of public reaction to earth construction in Nigeria is of a shelled compressed earth block (SCEB) of an inner core of ‘earth’ with less stabilisation and an outer shell of the same earth composition but with higher ratio of cement stabilisation for adequate durability, compressed into a single piece. A mechanical kit was designed and fabricated for the produc- tion of sample shelled compressed earth block for laboratory tests. Basic preliminary tests were conducted on the model and results revealed that the concept was feasible thus paved the way for further research work in shelled compressed earth block (SCEB). Ó 2014 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V. Open access under CC BY-NC-ND license. Keywords: Sustainability; Social consciousness; Shelled compressed earth block; Durability; Surface texture 1. Introduction In Nigeria, the relics of earth buildings are seen in our tra- ditional city centres as reminiscence of history. These old Buildings of earth date back to 12,000 BC (Pacheco- earth buildings, associated with the Natives, are gradually Torgal and Jalali, 2012). It was a phase in the historic disappearing as illustrious sons and daughters of these fam- development of human shelter. The basic house walls in ilies are replacing them with modern structures. Where most traditional architecture in Nigeria were built of ‘earth’ there were no means of replacing them, Natives have in simple low-cost and self-help construction arrangement. traded them for good fortune to Commercial Banks and Companies who desired their strategic locations. Modern research has established that earth construction ⇑ Corresponding author. Tel.: +44 7405549455, +234 8034655073. E-mail addresses: [email protected] (C. Egenti), [email protected]. is sustainable with less drain on infrastructure (Minke, uk (J.M. Khatib), [email protected] (D. Oloke). 2000; Keefe, 2005; Real, 2010). The earth technology has 1 Tel.: +44 01902518588. advanced with a modern face of stabilised compressed 2 Tel.: +44 7789264899. earth blocks (CEBs) and rammed earth (RE) walls. The Peer review under responsibility of The Gulf Organisation for Research analysis made by Guillaud et al. (1985) revealed that a and Development. compressed earth brick wall cost 32 per cent less than http://dx.doi.org/10.1016/j.ijsbe.2014.05.002 2212-6090/Ó 2014 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V. Open access under CC BY-NC-ND license. C. Egenti et al. / International Journal of Sustainable Built Environment 3 (2014) 72–86 73 sand–cement blocks. The analysis of Taylor and Luther these concerns. Common defects like in Fig. 1 are notice- (2004) showed that the large thermal capacity of earth able in even professionally executed earth walls. walls improves their thermal properties above that The most commonly used protection techniques were expected by consideration of R-values alone. Morton identified by various works in earth construction technol- (2010) revealed a sound reduction index of 46 db to ogy (Rigassi, 1985; Guillaud et al., 1985; Minke, 2000). 57 db; and that a 16 inch compressed earth brick wall has They are roof overhangs, cement, lime or bitumen stabilisa- a coefficient of acoustic attenuation (tested at 500 Hz) of tion, damp proof courses, surface coatings and rendering. 40 to 50 db. Earth improves indoor air quality and lowers Heath et al. (2012) suggested ‘appropriate detailing’ as a embodied energy (Minke, 2000). These characteristics of requirement for Modern Earth Construction. earth are highly desirable in the ailing economy of hot trop- ical environment. However, new houses built of earth are 2.1.1. Durability rare in urban environment in Nigeria, compared to the Durability in modern context should not be assessed by baked bricks in the United Kingdom and France. how long an earth wall stands without falling but also Sandcrete block-walls presently dominate the building con- how well the integrity of the original texture of exposed sur- struction industry in Nigeria with the attendant demerits of faces lasts with no deterioration. This probably explains the high cement utilisation, poor thermal performance and reason for a cold shoulder from Nigerians who under high cost. unpleasant financial strains strived to build with, the This research aims to enhance the compressed earth expensive, sand–cement blocks, which are widely known block by evolving a model that gives extra consideration for durability, reliability and pleasant aesthetic effect. to durability and surface texture within the framework of affordable housing and social consciousness of average 2.1.2. Planning Nigerians. A review and survey of housing in Nigeria were The planning of an adequate roof overhang to protect carried out. These were intended to practically identify rea- earth wall in Africa is very challenging. The cost of roof sons for non-acceptability and evolve possible solutions overhang in the contest of modernity can be enormous that may reverse the present trend of non-utilisation of (Egenti et al., 2013b). The microclimate of heavy driving earth. The contesting issue of durability against cost was rainfall in most parts of the continent and the low level analysed in a comparative assessment of cement content of infrastructural development like irregular supply of elec- needed for stabilisation. The emerging model is Shelled tricity make such planning difficult. The Architect goes compressed earth block (SCEB) for which a mechanical through the arduous task of balancing between creating kit was designed and fabricated to produce samples for lab- internal spaces of adequate natural lighting and ventilation oratory tests. Preliminary laboratory tests were conducted while avoiding an exposure of the external walls. The plan- on samples of SCEB specimens with feasible results. ning becomes almost impossible with storey buildings, which are most desirable in Africa for the factor of secu- rity, increased ventilation and social class factor. 2. Background/context for the study 2.1.3. Quality control Earth is an unstandardised building material with limi- This is applicable to material, methods and earth block tations which Minke (2000) identified as surface erosion presses. It is apparent that the state of quality control, for when exposed to weather and a need for frequent mainte- earth construction, hangs in critical balance with very lim- nance. Attempts have been made at solution to the limita- ited tolerance for satisfactory performance. It is worthy of tions of earth (Ngowi, 1997; Ikejiofor, 1998; Wekesa et al., note that the sand–cement wall system also has the quality 2010; Galan-Marin et al., 2010) with improved results. control element, but has been very successful in terms of However, overcoming the limitations of earth remained a durability in tropical environment because of a wider toler- subject of interest in modern research. ance for satisfactory performance. In other words, a small compromise in material and method may not result in very 2.1. Challenges of earth construction significant defect. This explains the reason why sand– cement wall has been very successful in the hands of all UNCHS Habitat (1986) observed from field experiences manners of artisans and funding statues of developers. It that majority of world’s earth houses in rural areas, all suf- is therefore important to advance earth construction fer from common defects identified as: Surface erosion, technology to a state of increased tolerance for satisfactory partial crumbling, unhealthy conditions due to constant performance where an architectural design with some humidity, and hallowed bases. Heathcote (1995) identified exposed walls or a small reduction in the effectiveness of durability of earth wall as one area that attracts the most a press may not result in very significant defects. Quality concern from the public and emphasised the importance control factor has been identified by field reports as reason of addressing this problem for earth to gain acceptance for defects in earth buildings (UN-HABITAT, 2012). as a modern building material. He concluded that there is These are probably the challenges militating against a no conclusive evidence based on field performance to alley wide acceptability of earth construction in urban environ- 74 C. Egenti et al. / International Journal of Sustainable Built Environment 3 (2014) 72–86 Figure 1. Common defects or imperfections in earth walls (Source: Walker et al., 2005). ment in Nigeria. This research aims to evolve a model that proof/washable surfaces for floors and walls. This was may increase the tolerance for satisfactory performance of apparently a progressive and positive development in compressed earth block. human shelter and living conditions – product of science and technological development.