In-service deterioration of compressed earth blocks

摘要

With the increasing backlog of shelter in most of the third world, attempts are being made to evolve low-cost but durable walling units. The introduction of compressed earth blocks (CEBs) some 50 years ago was seen as a major milestone. These blocks are made by compressing a damp mix of soil (90-95 percent), and cement (5-10 percent) to form strong and dense blocks used for walling. While considerable knowledge is available regarding their initial performance characteristics, little research has so far been conducted on their long-term durability and deterioration due to prolonged exposure to environmental factors. It is now widely recognised that rapid and premature deterioration does take place when the material is used in unrendered walling in most humid tropical environments. Premature defects such as roughening, pitting, erosion, volume reduction, cracking as well as crazing, etc., have all been witnessed within periods ranging from 1 month to 5 years after completion of construction. This paper reports on recent research conducted in Uganda where in-service defects such as pitting and cracking where measured directly from existing exposed walling to quantify their nature and extent. It can be concluded that the greatest deterioration was found to occur on east-west facing facades, and on the lower wall sections. The deterioration was also found to correspond to the age of the structure.