Investigation of Causes and Possible Preventive Measures to Cracks in Stabilized Rammed Earth Walls
Katuramu, Usaamah, Bagonza
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Stabilized rammed earth walls are a construction method that involves the use of a homogeneous soil, fine aggregates, binder, coarse aggregates and water to construct walls of low rise buildings. It is an ancient building technique that has recently been rediscovered due to its sustainability, low cost and superior aesthetic properties. Understanding its properties could provide an affordable alternative to housing for developing countries especially in Africa. This project sought to identify the causes of cracking in rammed earth construction by using a case study of Entebbe Emergency Paediatric Hospital where cracking had occurred. Preventive measures would then be proposed to avoid cracking in the walls for the benefit of future similar projects. The cracks observed and measured in the field were found to be up to 10 mm wide and up to 3m in length and therefore were of significance to the structural integrity of the walls. The results showed that the soils used at the site contained over 63% fines which was way above the recommended range of 15% to 25%. The results from Atterberg limits tests showed that the soil obtained from the site was predominantly clay. This implied that the soil would experience large volumetric changes and hence be prone to cracking. The compressive strength of the control mix, as used at the site, was found to be adequate. Furthermore, an increase in binder content led to an increase in compressive strength. A reduction of the fines content also showed an increase in compressive strength compared to that of the control mix. The results from the wet and dry appraisal test showed that reduction of fines content to recommended percentages led to better resistance to cracking when exposed to cyclic wetting and drying. Therefore, reduction of fines in predominantly clay soils was observed to be a suitable preventive measure to cracking in rammed earth walls. Further research was recommended in order to achieve a deeper understanding of properties stabilized rammed earth walls and enhance their suitability in Uganda and Africa at large.