Year

1992

Degree Name

Doctor of Philosophy

Department

Department of Civil and Mining Engineering

Abstract

Rice husk ash (RHA) and granulated blast furnace slag (GBFS) have been investigated as pozzolanic materials for soil stabilisation. They contain siliceous and aluminous materials, and react with lime or cement, having the economic potential to replace some of the lime or cement presently used as an additive in the stabilisation of soil.

Four (4) types of soils were treated with varying quantities of lime, cement, rice husk ash, granulated blast furnace slag, combinations of rice husk ash with lime or cement and combinations of granulated blast furnace slag with lime or cement under laboratory conditions.

To determine the effectiveness of RHA and GBFS as stabilisers, general geotechnical soil properties, including unconfined compressive strength, undrained shear strength, CBR, plasticity index and linear shrinkage, were measured. X-ray diffraction analysis, scanning electron microscopy and a repeated dynamic load test were also carried out in this investigation.

It is revealed that rice husk ash alone is not suitable for modifying soil properties, however, beneficial results are obtained when it is used in combinations with lime or cement. It is shown that lime-rice husk ash and cement rice-husk ash additives increase the unconfined compressive strength, the CBR and the undrained shear strength of soils. They also improve the behaviour of soils under the action of repeated dynamic loads and improve the workability and volume stability of soils.

It is revealed that granulated blast furnace slag alone is suitable for modifying the volume stability of heavy clays and the workability of gravel-sand soils. It increases the unconfined compressive strength and the CBR of soils and improves their behaviour under the action of repeated dynamic loads.

The effects of lime-granulated blast furnace slag and cement-granulated blast furnace slag additives on soils are shown to be similar to those of lime-rice husk ash and cement-rice husk ash additives.

The effectiveness of rice husk ash and granulated blast furnace slag can be expressed in terms of ratios of rice husk ash and granulated blast furnace slag required to lime or cement saved. Information relevant to these ratios and the current and projected future availability of granulated blast furnace slag and rice husk ash in Australia is presented.

A suggested mix design procedures for lime-rice husk ash, cement-rice husk ash, lime-granulated blast furnace slag and cement-granulated blast furnace slag soil stabilisation is also presented.

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