Mechanical Behavior of Fly Ash or Cement Amended Sand-Bentonite Mixtures Exposed to Freeze-Thaw Action After Long Curing

Abstract

In construction of landfills, embankments and transportation structures, use of clay-sand mixtures are commonly preferred. To provide stability and enhance engineering properties, stabilization with chemical admixtures is a reasonable approach. Unfortunately, freeze-thaw effect is a significant problem controlling the mechanical behavior of soils in cold regions. Since past studies on strength behavior of clay-sand mixtures stabilized using fly ash or cement exposed to freeze-thaw action is limited, in this study, an experimental framework was used to investigate the effects of clay content, admixture type, number of freeze-thaw cycles on strength of clay-sand mixtures including pozzolanic cement or class C fly ash. Sand specimens including 4, 8, 12 and 16% bentonite by weight were stabilized with 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 freeze-thaw cycles after 28 days of curing period. Freeze-thaw resistance of specimens was determined by carrying out unconfined compression tests. Experimental results revealed that, under certain curing conditions, cement and fly ash stabilization positively affects the strength of sand-bentonite mixtures and dominates the negative effects of freeze-thaw action. As expected, specimens stabilized with pozzolanic cement 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.

Review of the Effects of Freezing/Thawing Cycles on the Engineering Properties of Soilcrete

“…The difference in UCS between specimens with and without F/T cycles has been used as an index to estimate the durability of soilcrete against freezing conditions [34,49,53,58]. Binders added to the natural soil could resist freezing damage to a certain extent due to the bonds generated between soil particles and clusters [49,50,56,57,76]. Generally, the strength of soilcrete decreased with F/T cycles.…”

“…In Ref. [76], the authors used the UCS test to investigate the effects of F/T cycles on the clay-sand mixed with cement and fly ash. It was concluded that cement-treated soil has a higher resistance to F/T cycles than fly ash-treated soil, which was attributed to the difference in the hydration and pore-filling efficiency.…”

“…Figure6. The effect of binders on the performance of soilcrete subjected to F/T cycles: (a) UCS of soilcrete subjected to F/T cycles with varying bassanite content[52], (b) UCS of soilcrete subjected to F/T cycles with varying fly ash content[50], (c) UCS of soilcrete subjected to F/T cycles with varying bentonite and fly ash content[76].…”