Mechanical Behaviour of Soil Improved by Alkali Activated Binders

Enza Vitale,Chiara Bartolomeo,Claudio Ferone,Giacomo Russo,Gianfranco Dell’Agli

doi:10.3390/environments4040080

Abstract

The use of alkali activated binders to improve engineering properties of clayey soils is a novel solution, and an alternative to the widely diffused improvement based on the use of traditional binders such as lime and cement. In the paper the alkaline activation of two fly ashes, by-products of coal combustion thermoelectric power plants, has been presented. These alkali activated binders have been mixed with a clayey soil for evaluating the improvement of its mechanical behaviour. One-dimensional compression tests on raw and treated samples have been performed with reference to the effects induced by type of binder, binder contents and curing time. The experimental evidences at volume scale of the treated samples have been directly linked to the chemo-physical evolution of the binders, investigated over curing time by means of X Ray Diffraction. Test results showed a high reactivity of the alkali activated binders promoting the formation of new mineralogical phases responsible for the mechanical improvement of treated soil. The efficiency of alkali activated binders soil treatment has been highlighted by comparison with mechanical performance induced by Portland cement.

Highlights

Soil treatment is a widely used technique to improve the engineering properties of natural soils not suitable for construction purposes by means of the addition of chemical agents, which react with soil particles
The reactions kinetic controlling the chemo-physical evolution of alkali activated binders and the macroscopic evolution of soil properties depends on fly ashes mineralogy, as evidenced by the mechanical test results
An insight into the mechanical improvement induced by alkali-activated binders based on the activation of two different type of fly ashes on a clayey soil has been presented

Summary

Introduction

Soil treatment is a widely used technique to improve the engineering properties of natural soils not suitable for construction purposes by means of the addition of chemical agents, which react with soil particles. With reference to traditional binders, the mechanical improvement of soil is mainly due to pozzolanic activity developed after the addition of binder. The use of novel and efficient binders for geotechnical applications is a promising issue in terms of sustainability since it reduces the carbon footprint and allows reusing secondary by-products such as artificial pozzolans. These by-products can be involved in soil improvement as cementing agents if properly activated, inducing a mechanical improvement which allows the reuse of soils not suitable in their natural state as construction materials for earthworks. The recycling of waste materials such as Environments 2017, 4, 80; doi:10.3390/environments4040080 www.mdpi.com/journal/environments

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