Effect of sewage on compressive strength and geometric texture of the surface of concrete elements

Joanna Witkowska‐Dobrev, Olga Szlachetka, Maciej Malarski, Justyna Czajkowska, Maciej Miturski, Piotr Nowak, Marek Dohojda

This paper presents the results of a study on the compressive strength, weight loss, surface roughness, elemental analysis and ultrasonic pulse velocity (UPV) measurement after 270 days of seasoning concrete cubes measuring 100 × 100 × 100 mm in solutions of sewage from the post-grit chamber as well as sewage from the activated sludge chamber in three different environments, that is, acidic, neutral, and alkaline. The value of the compressive strength of the samples stored in the tested environments varied depending on the type of the tested wastewater and its pH in relation to the control sample. The most influence on compressive strength was acidic environment—the decrease was approximately 12.7% in the post-grit chamber and 9.5% in the activated sludge chamber. Samples which had been seasoned in the post-grid chamber were characterized by UPVs ranging from 4805.3 to 4864.6 m/s. Samples seasoned in an activated sludge chamber achieved UPVs ranging from 4689.7 to 4778.9 m/s. The average relative error between the compressive strength values calculated from the ultrasonic method according formula (3) and the measured values does not exceed 4%. The conclusions from the 3D measurements of roughnesses show that parameters Ra, Rz, Sa, and Sq are the most reliable in assessing the roughness intensity of corrosion damage of concrete caused by sewage. Elemental analysis proved that in the acidic pH solution of sewage from the post-grit chamber, the presence of calcium was not identified at any of the points tested.

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