The Development of a New Chemically Resistant Sprayed Mixture

Abstract

This paper deals with research and development of a new chemically resistant sprayed mixture based on portland cement and special admixtures. The new material will be part of a comprehensive remediation system for the remediation of chemically attacked and stressed sewer structures. The aim of this work is to verify the effect of the amount of crystalline waterproofing admixture on selected physical-mechanical characteristics and chemical resistance, specifically resistance to the attack of sulphate solution and the attack of aggressive biogenic sulfuric acid solution. Furthermore, the resulting characteristics of test specimens manufactured in the laboratory and test specimens made by spraying into boxes and subsequent cutting to the required dimensions were compared. Due to the fact that there is currently no official methodology in the Czech Republic for testing the chemical resistance of cementitious materials intended for sewage environments, the methodology was used in accordance with DIN 19573 "Draft on mortars for construction and rehabilitation sewer systems". The sulphate resistance was determined for test specimens measuring 160×40×10mm, which were exposed to a solution of sulphate salts with a concentration of 29.8g / l (44g/l Na2SO4) for 91days. To determinate the resistance to biogenic sulfuric acid, special tanks were assembled in which the test specimens, measuring 80×40×40mm, were exposed for 14 days to a solution of sulfuric acid (H2SO4) with a molar concentration of 1,0mol/l (pH=0). The results of this work show the optimal amount of crystalline waterproofing admixture. The results of this work will be used in the next phase of research, when cement and some fillers will be substituted by selected secondary raw materials, namely to improve or at least maintain the key characteristics of the final sprayed mixture. Keywords: Sprayed mixture, Sulphates, Biogenic sulfuric acid, Chemical resistance, Crystalline waterproofing admixture