Experimental study on shrinkage behaviour of earth walling materials with fibers and stabilizer for cob building

Abstract

In this paper, a series of laboratory tests on shrinkage of walling materials are presented. The walling materials consist of sandy soil, stabilizer and natural fibers. Two types of fiber, coconut coir and paddy straw were used as reinforcement and cement as stabilizer at varying percentages. Each type of sample (unreinforced, reinforced and stabilized) prepared by adding 31.7%, 33.7%, 35.7% and 40% moulding moisture content (MMC) were dried under three different temperatures of 30 °C, 50 °C and 70 °C respectively in the laboratory. The effect of the following factors on shrinkage was investigated: temperature, MMC, fiber types, fiber content and stabilizer. The result shows that addition of fibers to the soil contributed to a reduction in linear shrinkage and density of the sample, thereby reducing the weight of structures and cracking. The linear shrinkage is influenced by MMC, fiber content, and cement content, temperature and fiber types. That is at higher MMC and temperature the shrinkage value of sample increases. In general, preference are to be given to lower MMC and temperature and higher fiber content to achieve better performance of earth walling materials, i.e. reduction of shrinkage and crack formation.