Contribution of factors to the development of drying shrinkage in Ghana

Abstract

As part of the recommendations for serviceability, building codes have set limits to the amount of cracks that are permitted in structural members. Hence, in designing of structural members the anticipate d level of cracks should be accurately determine so as to design against them. One of the major factors that contribute to cracks in structural elements is shrinkage, of which drying shrinkage is dominant. Drying shrinkage has been defined as the deformation occurring as a result of moisture loss from the pores of the cement paste. In estimating for the effect of drying shrinkage, mathematical models have been used due to cost and time constraint. The models were arrived at by developing deformation with time equations which allow for variation in the parameters in the form of modification factors. Unfortunately, no single model is globally applicable due to the variations in the ambient conditions and the properties of the materials used for concrete. Hence for a model to be adopted accurately, it has to be calibrated against localized data, otherwise a new model has to be developed for use locally. In order to adopt any of the models in Ghana, it has to be calibrated against local ambient conditions and material properties. This study assessed to extent to which some of the contributing factors to drying shrinkage affect its development in Ghana. It identified the strength class of the cement as the factor that had the greatest influence on the development of the deformation. This was followed by the water-cement ratio, age of concrete at the onset of drying, fine aggregates content and the quantity of cement in the mix respectively.