Effect of organic matter on swell and undrained shear strength of treated soils

Abbey, Samuel Jonah; Omotayo Olubanwo, Adegoke; Ngambi, Samson; Umo Eyo, Eyo; Adeleke, Blessing Oluwaseun

Abstract

This paper presents a laboratory and statistical study on swell and undrained shear strength of cemented organic clays blended with eco-friendly (by-product) cementitious materials such as ground granulated blast slag (GGBS) and cement kiln dust (CKD). The presence of organic matter in soils can be very problematic especially during construction of infrastructures such as roads and foundations. Therefore, experimental and statistical investigations are crucial to further understand the effect of organic matter on swell and strength performance of soils treated with by-product materials (GGBS and CKD). Five artificially synthesised organic clays with 0%, 5%, 10%, 15% and 20% organic matters were mixed with 20% cement during the first phase of mixing. In the second phase, cement content was reduced to 4% and blended with 12% GGBS and 4% CKD respectively. All mixed samples were cured up to 56days and subjected to undrained triaxial test and one-dimensional oedometer swell test. The undrained shear strength of the untreated soils decreases from 22.47kPa to 15.6kPa upon increase in organic matter from 0-20%. While the swell increases from 1.17% to 3.83% for the same range of 0-20% organic matter. The results also show improvement on strength and swell upon addition of 20% cement for all investigated samples. For samples treated with 4% cement and inclusion of 12% GGBS and 4% CKD, the treated soils showed better performance in terms of swell potential due to reduction in plasticity compared to the plasticity of soils treated with 20% cement. Undrained shear strength increases from 632kPa to 804.9kPa and from 549.8kPa to 724.4kPa with reduction in organic matter upon addition of 20% CEM and 4% CEM: 12% GGBS: 4% CKD after 56days. The results obtained show that the inclusion of GGBS and CKD reduced swell and increases undrained shear strength irrespective of the percentage of organic materials due to cementation effect. However, results of the statistical studies show that the presence of organic matter influences the extent of performance of the cement, GGBS and CKD treated soils.

• Journal Article Type: Article
• Acceptance Date: Jul 1, 2019
• Online Publication Date: Jul 12, 2019
• Publication Date: Jul 12, 2019
• Deposit Date: Sep 26, 2019
• Publicly Available Date: Sep 27, 2019
• Journal: Journal of Civil, Construction and Environmental Engineering
• Print ISSN: 2637-3882
• Electronic ISSN: 2637-3890
• Publisher: Science Publishing Group
• Peer Reviewed: Peer Reviewed
• Volume: 4
• Issue: 2
• Pages: 48-58
• DOI: https://doi.org/10.11648/j.jccee.20190402.12
• Keywords: Stabilised Soils; Expansive Soils; Organic Matter; Undrained Strength; Swell Capacity; GGBS; Cement; CKD
• Public URL: https://uwe-repository.worktribe.com/output/3284144