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.
Highlights
Peat is an organic material and soils rich in organic matter constitute serious challenge to vital geotechnical and geological land development undertakings especially in areas where their deposits are abundant and unavoidable
This study has investigated the strength and swelling capacity of cemented medium swelling clay blended with ground granulated blast slag (GGBS) and cement kiln dust (CKD)
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
Summary
Peat is an organic material and soils rich in organic matter constitute serious challenge to vital geotechnical and geological land development undertakings especially in areas where their deposits are abundant and unavoidable. Soil mechanics practitioners and researchers have considered the study of the influence of the. Abbey Samuel Jonah et al.: Effect of Organic Matter on Swell and Undrained Shear Strength of Treated Soils organic matter content in clays as very pertinent because of their undesirable mechanical and geotechnical properties and because the amount and composition of organic matter does vary greatly in natural deposits [2, 3]. The behaviour of the clay has been reasoned to be dependent on the nature of the organic matter [4]. Organic matter found in soils could loosely be divided into three groups: non-humic (vegetal, animal, or micro-organism remains), humic (alkanes, fatty acids, humic acids, fulvic acids, and humins) and anthropogenic contaminants (oils and a variety of compounds) [4, 5]
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