CHEMICAL EVALUATION OF CRACK DEVELOPMENT IN CEMENT-BASED SANDCRETE STRUCTURE

摘要

Cement-based structure stability could be characterized not only by their mechanical strength, soil geophysics and loading condition, but also the resistance to various physical and chemical factors that could initiate its corrosion. The contribution of water and various water-based solutions in the environment, to cement based structure durability could be either physical as in seasonal flooding of the structure or chemical often initiated by the presence in the solution of organic or inorganic compounds or gases. Irrespective of the corrosion type, its destructive effect could be attributed to the build up of internal stress and weakening of the structure matrix. This work is aimed at investigating the role of chemical changes in the sandcrete matrix in the formation and development of macrocracks in cement-based sandcrete walls. Collected sandcrete samples were analyzed using titrimetric and granulometeric methods. Results showed that the percentage composition differential between the top and bottom of SiO_2 was high in all the sandcrete blocks samples analyzed ranging from 0.4-3.2%. This indicates high permeability of ground level structure. The acidic nature of the soil varying from pH = 5.89 - 6.11 could seriously undermine the structures strength. The CaO contents were generally very low ranging from 3.83 at the ground to 4.44% at the top levels. For most points there were compositional differential across cracked points horizontally and vertically. There is the need to encourage compositional differentiation to allow for leaching process and perhaps retard top down migration of dissolved hydrates/ions. This will minimize cracking process.