Effect of biochimical environment on fiber concrete containing silica fume

Abstract

The durability of a concrete depends on several factors, one can quote: final mechanical characteristics, operating stresses, environmental stresses… Specific conditions of surrounding environment generate disorders. This is the case of structures and equipment of wastewater treatment which pose some problems not being in the other traditional uses of the concrete, the phenomenon is bacterial in origin. The impact of these degradations is very harmful for our hygiene of life. The present study focuses on the durability of fiber-reinforced concrete kept in two environments: Sewer (aggressive environment) and cyclic wetting / drying (control environment).Three tests were carried out: strength, depth of pH reduction using phenolphthalein, and micro-structural analysis by SEM. The mixes studied had various water cement ratios (0.5; 0.65; 0.8), with a 0.5% steel fibre content and 10% silica fume content. To characterize the durability performance of the mortars studied, samples were exposed to one-year cyclic wetting and drying: control samples under laboratory conditions and exposure samples in a sewage pumping station sump. SEM observations were carried out on samples with 0.8 w/c ratio to study the micro structural changes in the mortar’s matrix. The SEM observation shows that there is a deterioration of the external surface of the samples by biochemical phenomena which are caused by a bacterial attack and sulphate attack.