MECHANICAL BEHAVIOR OF FLY ASH OR CEMENT STABILIZED SAND-BENTONITE MIXTURES EXPOSED TO FREEZE-THAW ACTION

Abstract

In construction of landfills, embankments and transportation structures, use of clay-sand mixtures are commonly preferred. To provide stability and enhanced engineering properties, stabilization with chemical admixtures is a reasonable approach. Unfortunately, freeze-thaw effect is a significant problem affecting soil behavior in cold regions. Studies on strength behavior of clay-sand mixtures stabilized using fly ash or cement exposed to freezing-thaw action is limited, and need further investigation. For this reason, in this study, using pozzolanic cement or class C fly ash as admixtures for clay-sand mixtures, an experimental framework was used to investigate the effects of clay content, admixture type, number of freeze-thaw cycles on strength of these mixtures. Sand specimens including 4, 8, 12 and 16% bentonite by weight were stabilized wih 3, 6, 9 % pozzolanic cement and 5, 10, 15, and 20 % class C fly ash by weight, specimens were prepared at optimum water content of mixtures. The specimens were then subjected to 1, 3 and 10 freezing / thaw cycles after 28 days of curing period. Freeze-thaw resistance of specimens was determined by application of unconfined compression tests. Experimental results revealed that, under the curing conditions adopted, cement and fly ash stabilization positively affects the strength of sand-bentonite mixtures and dominates the negative effects of freeze-thaw action. Pozzolanic cement stabilized samples provided higher freeze-thaw resistance compared to those amended with fly ash. Besides,  analysis of secant modulus values revealed that, cement stabilized specimens showed a more rigid behavior after freeze-thaw action. 

Keywords

• Sand-bentonite mixtures,freeze-thaw effect,cement,fly ash

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