SÜLFAT ETKİSİNE MARUZ ÇİMENTO İLE STABİLİZE EDİLMİŞ ZEMİNLERİN MİKROYAPISININ İNCELENMESİ
Project no. 755 · Status: Kapanmış · 2016
Summary
Widely used in the last century, stabilisation of soils with cement is known to provide benefits in promoting the engineering properties of soils. In addition to its positive effects on strength, additional advantages of this stabilisation method can be counted as the reduction in permeability as well as the increase in volumetric stability. On the other hand, chemical reactions occurring in cement stabilised soils either including sulfate salt or under sulfate attack cause reduction in strength and loss in volumetric stability. In this scope, a systematic approach was carried out to evaluate the improvement of the engineering properties of clays exposed to sulfate attack. Effects of cement type, cement content, sodium/magnesium sulfate salts, salt concentration, and curing period as well were individually investigated. Clay was stabilised using two types of cements, namely, normal portland cement and sulphate resistant cement. The cement contents were considered to be 0, 5, 10 and 15%, by weight. The mixtures were compacted using Standard Proctor effort. Two sulphate solutions were used: sodium sulphate and magnesium sulphate solutions. The concentration of the salts in mixture water were designated as 0.3, 0.5 and 1%. Specimens listed above were exposed to magnesium and sodium sulphate attack during 1, 7, 28 and 90 days curing. Experimental results were comparatively discussed. Moreover, the effect of sulfate attack on microstructure of cement stabilized clay was investigated by carrying out SEM and EDS analyses on selected specimens. The results obtained from experimental this experimental study revealed that, increase in cement content and curing period caused increase in strength. Micro cracks caused by ettringite formation induced strength loss. A cement stabilized clay resisting sulfate attack should include 10% of cement, by weight. As previously observed in concrete, microstructural investigations and results of strength tests revealed that use of sulfate resistant cement provide resistance against sulfate attack in cement stabilized soils.