High Performance Concrete Resistance To Sulfate Attack Pilot Study

Durability is one of the most important properties to evaluate the quality of concrete. Lots of original achievements and experiences in this field have been reported. A great deal of sound suggestions to improve the durability of concrete has been proposed. Although materials science and technology have being highly developed, there are still many problems remained unresolved by now when concrete structures are exposed in severe environment, for example, the guideline selection and durability evaluation of concrete.In this paper, high performance concrete (HPC), which are specially suitable for being used in salted region, are compounded with the differ proportion and kinds of mixing superplasticizer and high-quality mineral admixtures. In view of the environmental features of salted region, several different test methods of durability of concrete are designed.The paper studied sulphate resistance of concrete by drying-wetting in differ PH indicator salt solution and in water. Concrete durability deteriorates more rapidly under drying-wetting in salt solution than in water. And it is stricter to evaluate the frost resistance of concrete with the method of drying-wetting in salt solution than in water, and the evaluating results are more reliable.In the test of concrete, fly ash, mineral admixtures, silica fume and composite fly ash are for cement replacement materials (CRM). The results show that the high sulphate resistance of concrete has been completed in condition of general intension grade. The results show that fly ash, mineral admixtures and composite fly ash as CRM can increase concrete durability highly.After comparing the durability guideline, it is sure that dynamic elastic modulus is the most reliable to concrete durability; the method without dilapidation is feasible to evaluate concrete durability. It is sure that concrete lose durability when dynamic elastic modulus loss rate reached 40%.Through studying SEM microstructure of concrete, it is put forward that HPC used in salted region should form more perfect microstructures as the follows than the ordinary HPC:(1) Matrix of hardened cement paste: gel C-S-H forms dense net structure which is filled by secondary hydrate, so the matrix of hardened cement paste is very uniform and dense.(2) Interface zone: not only the thickness of interface zone is reduced and the orientation of hydrate in it decreases, but also its pore structure becomes better and hydrate in it forms net structure.It is the above microstructures that give the excellent durability to HPC used in salted region.