STUDY OF MECHANICALLY PRESSED COMPOSITE EARTH BLOCKS

Abstract

This paper presents the use of mechanically pressed composite earth blocks for low cost housing. In developing countries there is a considerable need to develop materials, which may replace or minimize the use of costlyconstruction materials. The soil when combined with a small percentage of fly ash, rice husk, surkhi, volcanic ash,lime, sand or cement, in the presence of moisture, and then mechanically pressed, gives more strength and satisfactory moisture resistance as compared to the ordinary burnt bricks. For this purpose, the research work was carried out to improve the engineering properties of soil for more strength and better moisture resistance. The paper outlines the research being carried out by the authors (for M.Sc structural engineering at N.W.F.P, U.E.T, Peshawar, Pakistan) on the compressive strength and erosion of mechanically pressed earth blocks. Pressed earth blocks were made of earth/clay with around 5-10% pozzolanic materials like fly ash, rice husk, volcanic ash, surkhi, and bentonite etc in a special steel mould. The soil was brought from different quarries, and about 200 pressed earth blockswere prepared from thirteen combinations of composite earth blocks. The composite pressed earth blocks were kept for 5 days natural drying before they were subjected to compression test. All the thirteen combinations were thensubjected to abrasion test, both with & without surface treatment. The performance of pressed soil blocks was not satisfactory without surface treatment against water. In order to improve their abrasion strength against water, ten surface treatment materials were prepared; three bricks from each combination were subjected to surface treatment for each material and the bricks were cured for 5 days. The bricks were subjected to 20 minutes heavy spray of water and the materials giving satisfactory surface treatment were lime + surkhi (1:4) and cement + sand (1:6) by weight. The masonry strength of the mechanically pressed earth blocks was then determined by preparing twoprisms of 9 x 9 x 24 inch, using mortars as binding materials, one with lime:surkhi (1:4) and other with cement:sand (1:6) by weight. The seven days compressive strengths of these prisms were 375 psi and 337 psi forcement: sand and lime: surkhi mortars respectively, which were quite satisfactory