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The Characterisation of the Strength Development of A Cement-Stabilised Soft Soil Treated with Two Different Types of Fly Ashes

Jafer, HM and Atherton, W and Al-Dulaimi, A (2017) The Characterisation of the Strength Development of A Cement-Stabilised Soft Soil Treated with Two Different Types of Fly Ashes. In: Proceedings 16th Annual International Conference on Asphalt, Pavement Engineering and Infrastructure , 16 (22-23). (16th Annual International Conference on Asphalt, Pavement Engineering and Infrastructure, 22 February 2017 - 23 February 2017, Britannia Adelphi Hotel, Liverpool, UK).

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Abstract

There are several problems associated with soft soils such as the low strength, high compressibility and the sensitivity with the changes in the water content. In order to mitigate such undesirable properties, soft soils are often improved and stabilised either mechanically chemically. However, chemical stabilisation is the most effective technique to improve the geotechnical properties of the soft soil. This study aims to improve the properties of a soft soil regarding the consistency and compressive strength by using a small amount of cement (5% OPC by the dry weight of the treated soil). Then two different types of fly ash were examined for pozzolanic activation of the cement treated soil. These fly ashes were pulverised fuel ash (PFA) and palm oil fuel ash (POFA). Initially, trial specimens containing 5% OPC with 5% of PFA or POFA were prepared for unconfined compressive strength testing (UCS) conducted at 7 days of curing. These trial specimens were manufactured to indicate with which type of fly ash the future research should be based on. The results of UCS test revealed that PFA indicated higher strength than that for POFA after 7 days of curing. Thus PFA was considered in this study as a pozzolanic activator for further experimental works. Additionally, the cement-stabilised soil (CSS) mixture was mixed with PFA with different proportions where OPC was kept as 5% and PFA was varied from 5–15% by the dry weight of the stabilised soil. The improvement levels in the stabilised soil were evaluated dependent on the results of UCS test conducted on specimens of CSS treated with different percentages of PFA and subjected to two different periods of curing (7 and 28 days). The effect of PFA on the compaction parameters (maximum dry density (MDD), optimum moisture content (OMC)) and Atterberg limits (liquid limit (LL), plastic limit (PL), along with the plasticity index (PI)) of the CSS soil was also explored in this study. The plasticity characteristic of the treated soil was found to decrease with continuous increments of PFA. The PI decreased from 20.3 for the untreated soil to 13.75 for the cement stabilised soil treated with 10% PFA. The optimised mixture in this research was found to be (soil + 5% OPC + 10% PFA) which increased the UCS of the soil from 134kPa for the virgin soil (VS) and 732kPa for the soil treated with only 5% OPC cured for 28 days to 946kPa at an equivalent 28 days of curing.

Item Type: Conference or Workshop Item (Paper)
Uncontrolled Keywords: Soil stabilisation; OPC; Fly ashes; Pozzolanic activation; unconfined compressive strength
Subjects: T Technology > TE Highway engineering. Roads and pavements
T Technology > TP Chemical technology
Divisions: Civil Engineering
Publisher: Liverpool Center for Materials Technology
Date Deposited: 19 May 2017 10:44
Last Modified: 19 May 2017 10:44
URI: http://researchonline.ljmu.ac.uk/id/eprint/6529

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