CEMENT COMPOSITES WITH WASTE INCORPORATION UNDER ACID RAIN ATTACK

Abstract

The paper is aimed at the study of the resistance of cement pastes containing various secondary materials (fly ash, zeolite, zeoslag, slag and microsilica) in the model environment of acid rain. Changes in characteristics of the studied materials due to acid rain, such as compressive strength of cement composites, water absorption, penetration of aggressive ions, pH of material and its chemical composition were analysed. Model acidic environments represented solutions simulating acid rain with different pH values (2, 4 and 6). Natural acid rain, deionized water and saturated solution of Ca(OH)2 were used as reference media. Based on the experimental findings, it can be stated that a positive effect of the secondary materials on increasing the resistance of cement pastes has been proven. The cement pastes with added additives resulted in a significant reduction in permeability in each model environment. This fact has an impact on the overall durability due to the fact that the amount of aggressive ions in the internal structure is reduced, causing corrosion and subsequent deterioration of cement composites. Based on the innovative methodology for the ion-penetraton test of cement pastes, a coefficient was designed, which characterizes the effect of the used admixture in terms of pozzolanic resp. latent hydraulic activities. Based on this coefficient, the most significant positive effect was manifested by the use of an admixture of ash and zeolite. The rapid chloride penetration (RCP) test method has thus proved to be much more relevant in comparison with, for example, water absorption.