Deterioration of long-serving cement-based sandcrete structures in Nigeria

Abstract The fall in living standard of the Nigerian citizenry, starting from the mid-1980s, has encouraged massive importation of secondhand goods, most especially industrial machines, cars, motorcycles, etc. It is a well-known fact that the majority of these equipment are very inefficient and produce a lot of pollutants (Cl − , SO 2 , CO 2 , CO, N x O y , etc), particularly as a result of incomplete fuel combustion. The presence of these pollutants has contributed not only to the depreciation of the people's quality of life, but also to the degradation of cement-based structures' physicochemical, mechanical and aesthetic qualities. This paper is aimed at developing a deterministic model, based on a mechanism of cement corrosion, to predict the deterioration of cement-based structures in Nigeria. The developed model equation showed that intensive diffusion of pollutants takes place within 0- to 10-mm-depth of the sandcrete block. It represents the relationship between concentration of pollutant and depth of their penetration and gives a comparative measure of the ease of diffusion of the latter into the structure at various depths. Variation in the type of pollutant and possible reaction, including leaching need to be considered in order to develop an acceptable model.