Effects of Using Pozzolan and Portland Cement in the Treatment of Dispersive Clay

A. H. Vakili,M. R. Selamat,H. Moayedi

doi:10.1155/2013/547615

Abstract

Use of dispersive clay as construction material requires treatment such as by chemical addition. Treatments to dispersive clay using pozzolan and Portland cement, singly and simultaneously, were carried out in this study. When used alone, the optimum amount of pozzolan required to treat a fully dispersive clay sample was 5%, but the curing time to reduce dispersion potential, from 100% to 30% or less, was 3 month long. On the other hand, also when used alone, a 3% cement content was capable of reducing dispersion potential to almost zero percent in only 7 days; and a 2% cement content was capable of achieving similar result in 14 days. However, treatment by cement alone is costly and could jeopardize the long term performance. Thus, a combined 5% pozzolan and 1.5% cement content was found capable of reducing dispersion potential from 100% to zero percent in 14 days. The results indicate that although simultaneous treatment with pozzolan and cement would extend the required curing time in comparison to treatment by cement alone of a higher content, the task could still be carried out in a reasonable period of curing time while avoiding the drawbacks of using either pozzolan or cement alone.

Highlights

Dispersive clays have been found in various types of climates and in various locations in Australia, Brazil, Iran, New Zealand, The United States, Thailand, Mexico, Vietnam, South Africa, and many other countries [1,2,3]
Whenever dispersive clay is exposed to water, especially with low salt concentration, the particles separate from each other, become dispersed, and get washed away such as in the progressive erosion phenomenon known as piping [7,8,9,10,11,12]
The origins of piping which could be cracks due to shrinkage, unequal settlement, or structural fractures need to be avoided at an early stage and the construction materials for earth dams, embankments, and foundations need to be erosion resistant [7]

Summary

Introduction

Dispersive clays have been found in various types of climates and in various locations in Australia, Brazil, Iran, New Zealand, The United States, Thailand, Mexico, Vietnam, South Africa, and many other countries [1,2,3]. Dispersion potential, measured in terms of percent dispersion, is a physicochemical phenomenon that is mostly influenced by minerals in the clays and chemical contents of pore water [4,5,6]. Whenever dispersive clay is exposed to water, especially with low salt concentration, the particles separate from each other, become dispersed, and get washed away such as in the progressive erosion phenomenon known as piping [7,8,9,10,11,12]. Changes in soil characteristics during chemical treatment are likely due to the cation exchange Na+ with Ca2+ and Al3+, reduction in the thickness of diffused double layer, and the subsequent reduction in the repulsive forces of the clay particles [3]

Methods

Results

Conclusion