EFFECT OF INDUSTRIAL WASTE WATER ON STRENGTH AND DURABILITY OF CONSTRUCTION MATERIALS

Abstract

Stone masonry and brick masonry with cement mortar as binding material has been used since long times. However, with developments now a days, concrete is widely used and is a durable construction material for large and heavy structures. The structures using concrete as construction material and cement mortar as binding material have shown significant signs of deterioration due to the sharp rise in the environmental pollution in the recent past. Deterioration of construction materials is the result of number of physical, chemical and biological factors in addition to the environmental conditions. Industrial waste water contains various pollutants viz. salts, ammonia, acids, alkali, nitrates, sulphates etc. which cause chemical deterioration of construction materials. Irrigation structures, bridge structures i.e. piers, abutments and substructures such as foundations etc. are always exposed to water for a long time pdauted by different industrial wastes discharging into the streams and other water bodies. The present study embodies a few of the chemicals NH3' acids & alkali, responsible for decay of cement sand mortar and cement concrete, the materials most extensively used in construction. The most common pollutants encountered in water (iv) bodies are solids, nitrogen in all forms, acids, alkali and sulphates from the industries such as sugar, pulp and paper, distillery, fertilizer 4nd steel industries. °Usually the pH of the waste from these industries vary between 2 to 12 and ammonia constitutes the important pollutant of fertilizer industry waste, so the physico chemical studies have been carried out to determine the effect of pH and ammonia for a maximum immersion period of 90 days. The weight loss, water absorption and compressive strength/ flexural strength have been determined at different immersion periods to study the effect on strength & durability of the materials. The general trend in all the cases is the progressive increase in weight loss, water absorption and reduction in compressive strength/flexural strength with the decay of respective material. There is an exception in case of low ammonia concentration solution, thAit- is weight gain, though not much significant and also there is increase in compressive strength/flexural strength of the construction materials while in case of higher concentration the results are adversely effected. In cement mortar and concrete disintegration starts with surface roughness due to surface erosion of material and this behaviour was dominant in case when cement mortar or concrete cubes were immersed in pH solutions lying in acidic range. It is found that weight loss, increase in water absorption and decrease in compressive strength/ flexural strength were significant in pH solutions of 2,4 & 6, (v) while in other pH solutions the effect was not significant. The compressive strength of cement mortar and concrete was found to reduce by about 45 percent for pH less than 7 at 90 days immersion period. The redUction was only 15 percent for pH greater than 7 at 90 days immersion period. The flexural strength of concrete was found to reduce by 25 percent for pH less than 7 while decrease is insignificant for pH greater than 7. The maximum weight loss recorded was about 5 percent and increase in water absorption was 130 percent. The extent of water absorption can easily be correlated with the significant reduction in strength. Cement mortar and concrete are safe in 0.1 and 0.5 percent ammonia solution, where there is weight gain and increase in compressive strength/flexural strength with variation of immeresion period. For 1 percent ammonia solution there is decrease in Weight, increase in water absorption and decrease in compressive strength/flexural strength with immersion period variation due to surface erosion of material at higher concentration of ammonia.