Wastewater structures, such as treatment plants or sewers can be easily affected by bio-corrosion influenced by microorganisms living in waste water. The activity of these microbes results in deterioration and can cause the reduction in structural performance of such structures. In order to improve the durability of mortar and concrete, different admixtures are being used and the best impact is observed in cement based materials combined with blast furnace slag. In this study, mortar samples with blast furnace slag were exposed to bacterial sulphate attack for 90 and 180 days. The leaching of calcium ions from the cement matrix and equivalent damaged depths of studied mortar samples were evaluated. The results showed more significant leaching of samples placed in bacterial environment, compared to the samples placed in non-bacterial environment. Similarly, the equivalent damaged depths of mortars were much higher for the bacteria-influenced samples. The slag-based cement mortars did not clearly show improved resistance in bacterial medium in terms of calcium leaching.

Water absorptivity is heavily influenced by the volume and connectivity of pores in the pore network of cement composites and has been used as an important parameter for quantifying their durability. To improve the durability and permeability of mortars, various mineral admixtures such as furnace slag, silica fume or fly ash are added into the mortar and concrete mixtures. These admixtures provide numerous important advantages such as corrosion control, improvement of mechanical and physical properties and better workability. This study investigated the changes in absorptivity of cement mortars with different amounts of mineral admixture, represented by granulated blast furnace slag, under aggressive bacterial influence. The water absorptivity of mortars specimens exposed to sulphur-oxidising bacteria A. thiooxidans for the period of 3 and 6 months has changed due to bio-corrosion-based degradation process. The differences in water absorptivity in dependence on the mortars composition have been observed.

The durability of cement-based materials is an increasingly important characteristic for civil engineering structures due to the growing demand for their long service life and minimal maintenance. Mortars and concrete with high acid resistance are required for the construction and the repair of sewer structures, in which biogenic sulphuric acid attack is the major degradation mechanism. Important progress has been achieved in this regard with hybrid binders and materials known as supplementary cementitious materials (blast furnace slag, silica fume, fly ash etc.). These mainly industrial wastes and by-products increase many important properties of concrete structures such as acid resistance, permeability, strength and many more. This study investigates the effect of industrial by-products such as blast furnace slag and fly ash on strength and leaching parameters of composites exposed to bacterial influence. The medium with bacteria A. thiooxidans was used for microbiologically induced corrosion and the experiments were conducted during the period of 9 months. The sample with 95 wt. % of slag was found more resistible in bacterial environment compared to the sample with hybrid binder.

Resistance of cement composites against various chemical processes such as sulphate attack and corrosion is nowadays one of the most desired property. Mechanism largely involved in sulphate corrosion is the ingress of aggressive ions through diffusion. The result of the ingress of aggressive ions is leaching of the elements from the mortar matrix and the deterioration of the composite. In the experiment, the slag-based cement mortars samples were exposed to an aggressive microbiological sulphate environment, represented by the bacteria A. thiooxidans, for the period of 6 months. The paper presents the investigation of damaged depths of cement mortars based on the leaching characteristics of the Ca ions. The damage depths (EDD) of cement composites were much higher (up to 0.2 mm) for samples placed in the biotic environment, which confirms the aggressive action of A. thiooxidans.

Acid rain is identified as one of the most serious environmental problems nowadays and it is mainly a mixture of sulfuric and nitric acids. Deterioration of concrete structures exposed to aggressive acid rain attack is a key durability issue that affects the performance and maintenance costs of vital civil infrastructures. The motivation for understanding the acid rain corrosion process is high because of the early age deterioration of many concrete structures exposed to acid rain. The main objective of this study was to investigate the durability of concrete specimens with different supplementary cementitious materials, such as fly ash, zeolite and blast furnace slag against acid rain attack. Experiments of acid rain simulation influence on the composites were carried out for 7 weeks and parameters like visual changes, absorbability and leachability of calcium and silicon ions were evaluated. The increase in absorbability was detected for all samples while the sample with blast furnace slag was identified to be the most durable in this point of view. The most durable sample considering leached-out calcium and silicon ions was found to be sample with fly ash.