Stabilisation of peat soil using unique additives with sand and incinerated bottom ash

Peatlands are areas where peat has accumulated over hundreds or thousands of years with depths of at least 450mm. The Republic of Ireland has 17.2% of its land mass classed as Peatlands and this is only higher in Finland,... [ view full abstract ]

Peatlands are areas where peat has accumulated over hundreds or thousands of years with depths of at least 450mm. The Republic of Ireland has 17.2% of its land mass classed as Peatlands and this is only higher in Finland, Canada and Indonesia. Due to these high levels of peat present in Irish soil, difficulties have arisen when undertaking construction projects in areas with this type of land due to peat’s poor geotechnical properties such as high water content, low shear strength, high organic matter and low bearing capacity.

This project involved investigating techniques for soil stabilisation through the use of novel additives as well as the replacement of sand with municipal waste incinerator bottom ash. The soil being tested was a peaty top layer of soil taken from a depth of between 100mm and 400mm of land between Navan and Athboy, Co. Meath in eastern Ireland. Seven different mixes were prepared with three mixes using unique additives Market Leading Additive 1 (MLA-1), Intelligent Soil Additive 1 (ISA-1) and Intelligent Soil Additive (ISA-2) mixed with sand and cement and the next three using the unique additives mixed with municipal waste incinerator bottom ash (MWIBA) and cement. The final mix was a control mix only using cement and sand with no additive. Compression and flexural tests were carried out to determine initial mechanical characteristics of the mixes. The results of this project will be used to identify the best additive/sand and best additive/ incinerated bottom ash mixes to be used in further study.

The results from this study show that the mixes containing the unique additives performed better than the control mix that only used cement. Specifically, ISA-2/sand and ISA-1/incinerated bottom ash mixes gave the highest average compression strengths while the MLA-1/sand and MLA-1/incinerated bottom ash mixes gave the highest average flexural strengths. These results show that the use of the unique additives can improve the mechanical characteristics and that municipal waste incinerated bottom ashley can be used as an alternative to sand in soil stabilisation.