Abstract
Uncontrolled evaporation of moisture from compressed clay beams can cause surface cracks, resulting in reduction of strength. This paper presents various treatments applied to clay beams during the process of casting, compacting and drying in order to curtail the possibility of cracking and to decrease percentage of drying shrinkage. Following treatments were applied to the beams during casting and drying: (i) a steel plate and double layer of plastic sheet was provided between the beam and the plank, (ii) the beam was enveloped with a propylene fabric sheet during casting and (iii) beams were covered with plastic sheet during drying. Using these treatments, the clay beams were cast and compacted at various intensities of compaction. The results show that the drying shrinkage was reduced to minimum and the cracks were curtailed. The rate of drying shrinkage was decreased depending upon the level of compaction. Thus at the higher degree of compaction, more density of clay beams was achieved, which resulted in higher degree of compressive strength in baked and unbaked state.
Highlights
Shelter is one of the basic requirements of human being besides food
In order to increase the performance of moulded earth blocks in unbaked state, it was tamped and compressed since18th century [4] and is called CEB (Compressed Earth Blocks)
A finished steel plate underneath a double layer of plastic sheet was provided between the beam and the wooden plank on which the beam was cast (Fig. 2).The double layer of plastic sheet was provided between the steel plate and the beam in order to provide a friction free medium
Summary
Shelter is one of the basic requirements of human being besides food. The modern tendency is towards construction of structures with reinforced cement concrete and steel which is not affordable for the poor masses [1]. Low cost and indigenous material of construction is to be sought and used in original or modified state for the construction of affordable houses. In order to use indigenous clay as low cost material of construction, beams were cast and compacted from a mixture of clay and pit sand in a ratio of 70:30, in addition to 22% of potable water. During the process of drying of these clay beams, shrinkage cracks occurred due to evaporation of moisture. Due to this shrinkage, tensile stresses may develop. Associate Professor, Department of Civil Engineering, Mehran University of Engineering & Technology, Jamshoro. The object of this study is to decipher the treatments by application of which the problems of drying shrinkage and cracking in the clay beams could be curtailed
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