DETERIORATION OF ORDINARY PORTLAND CEMENT AND FLY-ASH BASED GEO-POLYMER CONCRETES DUE TO SULFATE ATTACK UNDER THE ACTION OF SULFURIC ACID AND WASTEWATER

Corrosion in concrete sewers and wastewater treatment plants has been a major problem but this issue has not been resolved satisfactorily yet. Generally, deterioration happens due to sulfuric acid reaction with treatment units and sewer materials. Geo-polymer binders especially fly ash (FA) is an acid resistant and can be used as a substitute binder for sewer construction. This research work highlights the laboratory results of fly ash based geo-polymer concrete and effects on its durability under sulfuric acid exposure. Class ‘F’ fly ash was used in the preparation of samples that were properly cured for 28 days at room temperature. After curing, specimens were immersed in three types of sulfate containing solutions to check corrosion.. These sulfate containing solutions include static sulfuric acid, dynamic wastewater and static wastewater. Samples were tested at 28, 45 and 60 days after immersing in different type of solutions to find the corrosion depth. By visual inspection the corrosion depth and residual compressive strength were observed according to the modified ASTM C267& C39 respectively. Reaction products of gypsum remained on the surface of concrete samples absorbed in diluted sulfuric acid, while reaction products of gypsum were not seen on the surfaces of concrete samples absorbed in static as well as dynamic wastewater. Static wastewater also produced corrosion but in a limited fashion, it causes only surface weathering. The obtained results are strongly confirming that geopolymer concrete samples are showing great resistant to sulfuric acid solution. Moreover, geo-polymer samples were also showing reasonable load carrying capacity after entire section had been neutralized by sulfuric acid