Study of the Deterioration of Concrete Influenced by Biogenic Sulphate Attack

Prediction of remaining life of RCC sewer manhole using smart material-based EMI technique for sustainable environment

Manholes are vital component of the sewerage system; they are often damaged due to concrete corrosion, hydrogen sulphide (H₂S) gas released by sewage effluent and vehicular loading. Due to large number of accidents occurred on the road, there is need for supervision of manholes so that it can be replaced when it is about to damage. In this paper, three different manholes were tested according to Indian standard code IS 12592 (2002). At the same time, using electro mechanical impedance (EMI) technique, the damage quantification was done using root mean square deviation (RMSD) for the obtained signature of the manholes with different damage stages. Three PZT sensors were bonded using epoxy, one each on top and bottom of manhole cover and third at the frame of the manhole. It was found that the PZT bonded at bottom captures the damages well than the PZT bonded on the top of cover, but it shows large variation when the crack line passes through the PZT bonded place, the PZT bonded on the frame shows abrupt variations with the damage. Hence, PZT sensor pasted on top of manhole cover was found to be well correlated to the damage stages. The effective structural parameters were extracted using PZT sensor; moreover, for all the three manhole structures, the structural damping was identified for different damage states. A model was developed including all three manholes with more than 95% confidence level for estimating the remaining life of manhole.

Enhancing the Biological Oxidation of H2S in a Sewer Pipe with Highly Conductive Concrete and Electricity-Producing Bacteria

Hydrogen sulfide (H2S) generated in sewer systems is problematic to public health and the environment, owing to its corrosive consequences, odor concerns, and poison control issues. In a previous work, conductive concrete, based on amorphous carbon with a mechanism that operates as a microbial fuel cell was investigated. The objective of the present study is to develop additional materials for highly conductive concrete, to mitigate the concentration of H2S in sewer pipes. Adsorption experiments were conducted to elucidate the role of the H2S reduction. Additionally, electricity-producing bacteria (EPB), isolated from a municipal wastewater treatment plant, were inoculated to improve the H2S reduction. The experimental results showed that inoculation with EPB could decrease the concentration of H2S, indicating that H2S was biologically oxidized by EPB. Several types of new materials containing acetylene black, or magnetite were discovered for use as conductive concrete, and their abilities to enhance the biological oxidation of H2S were evaluated. These conductive concretes were more effective than the commercial conductive concrete, based on amorphous carbon, in decreasing the H2S concentration in sewer pipes.