Abstract
Improvement of soft soil using cementitious additives is a widely practiced technique in the construction industry. However, cement mixing is considered to be an expensive technique and this research has attempted to study the use of an industrial waste; flyash to improve a drinking water treatment sludge. Flyash is a fine, glass powder recovered from the gases of burning coal during the production of electricity at Norochchole, thermal power plant in Sri Lanka. The larger amount of drinking water treatment sludge which is a very soft clayey soil, is disposed into the environment without acquiring any benefit. Use of flyash in improving soft soils such as sludge with a low maximum dry density and low CBR will solve few burning issues such as dumping of flyash and sludge, health issues due to disposal of flyash and sludge, difficulties to find soils with better properties for road constructions and other construction related applications. Identifying the characteristics of the sludge, studying the variation of maximum dry density and optimum moisture content with flyash content, strength gain with time, and the applicability of the improved soil in the industry are the key findings and observations of this study. It was observed that the optimum proportion of the flyash to be added to the sludge to achieve a remarkable gain in its properties is around 30% of its dry weight. Acceptable CBR value was achieved after 7 days curing followed by standard 4 days soaking period.
Highlights
One of the most demanding issues in civil engineering constructions is unavailability of suitable soils for applications such as highway, and railway construction and land filling
Properties of sludge The sludge used in this study was collected from a water treatment plant located in Horana, Kalutara district, Sri Lanka
It was observed that liquid limit, plastic limit and plasticity index of sludge Were, 59.44, 51.75 and 7.69% respectively
Summary
One of the most demanding issues in civil engineering constructions is unavailability of suitable soils for applications such as highway, and railway construction and land filling. Low shear strength, and high compressibility are some of the key issues that generally arise in road and other construction sectors with a poor soil. The most common solution for these issues is removing the weak soil and refill it with a good soil. This will be time consuming and costly and very importantly dumping of poor soil is not environmental friendly. A reasonable option to overcome this issue is to improve the existing soil using appropriate additive materials
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