Effect of Silica Fume and Natural Pozzolanas on Sulfuric Acid Resistance of Dense Concretes

Biogenic sulfuric acid corrosion is often a problem in sewer environments. Also in certainindustrial activities sulfuric acid is used during the production process. 􀃸t can lead to a fastdegradation of the concrete structures. Therefore there is a substaintial need for construction of durable concrete structures in such environments. The porosity of concretes plays an important role in harsh environments. For production of low porosity or high density concretes, optimization of aggregate and cement grading and their proporations is necessary. The size distribution of aggregates and cement materials determine the compactibility and highest local density of particles. Dense packing of concrete particles in the mixes lead to low cement content and high-strength of low porosity mortar and concretes. A research program was under taken to improve concrete resistance against sulfuric acid attack. Five concrete mixtures were investigated, first mix contains Type 2 portland cement as a control mix and the second one contains Type 2 portland cement and super fine Quartz powder as a filler with particle size between 0 to 16 micron. Third mix contains Type 2 portland cement with 8% silica fume (SF) replacement and super fine filler. Other mixes contain Type 2 portland cement with 20% natural pozzolanas replacement namely Trass and Pumice and super fine filler. The dense packing of siliceous aggregates and cement materials were used to achieve the highest density of concretes. Fuller ideal grading curve for particle size distribution (PSD) of cement material was used. The PSD of the Quartz powder, silica fume, natural pozzolanas and cement were analayzed to explain the packing effect of super fine Quartz powder. Cementitious material content and water binder ratio were varried in this investigation. 􀃸n the experiment, concrete cubes and mortar plates were immersed insulfuric acid with pH=1.0. They were periodically examined for appearance, measured formass change and tested in compression and flexure up to 180 days. The performance ofmortar and concretes containing Trass and ultra fine filler was better than the other mixes. Also performance of other mixtures was better than the control mixture.