Study on cement and lime stabilization on soils of selected reclaimed sites of Dhaka city

Abstract

In the present study cement stabilization of reclaimed soils of two selected sites (Aminbazar and Bashillldhara) and lime stabilization of one site (Bashlllldhara) in Dhaka City were carried out in order to assess their suitability for use in road construction. The soils from Aminbazar and Bashundhara were respectively a clayey silt oflow plasticity (LL=4l, Pl=12) and a silty clay of high plasticity (LL=52, PI=29). As additives, ordinary Portland cement was used in percentage of 1,3 and 5 for Aminbazar soil and 1, 3, 5 and 7 for Bashundhara soil while slacked lime was used in percentages of 1, 3, 5 and 7 for Bashillldhara soil. Comparisons of different soil stabilization of regional soils of Bangladesh were also lllldertaken. Index tests indicate that compared with the untreated samples, plasticity index and linear shrinkage of the cement and lime stabilized samples of the soils reduced. Shrinkage limit, however, reduced for cement-treated samples while it increased for lime-treated samples. For the cement and lime stabilized samples, maximrun dry density increased and reduced respectively, while optimum moisture content reduced and increased for cement and lime stabilized samples respectively with the increase in additive content. For samples of both the sites, unconfined compressive strength of cement and lime treated samples increased significantly than the untreated samples, depending on the additive content and curing age. It was found that compressive strength of samples treated with 3% cement and cured for 14 and 28 days satisfied the PCA (1956) for the compressive strength of soilcement mix and that for all cement contents and all curing ages. Compressive strength of the stabilized samples fulfilled the requirements of soil-eement mix for use in road sub-base and base subject to light traffic, as proposed by Ingles and Metcalf (1972). It was also fOillld that the compressive strength of samples treated with 5% and 7% lime met the requirements of upgrading heavy clays to sub-base materials quality type, proposed by Ingles and Metcalf (1972). In attempt to investigate the effect of molding water content on qu,it appeared that in order to achieve maximum compressive strength, the cement and lime stabilized samples should be compacted at their optimum and wet side of optimum moisture content respectively. Compared with untreated samples, CBR of the cement and lime stabilized samples increased up to about 5.8 times and 4.1 times respectively. CBR values of samples of both the soils, treated with 3% and 5% cement, fulfilled the requirements of soil-eement road sub-base and base for light traffic while CBR values of samples stabilized with 7% lime did not satisi)' the criteria of the minimum CBR for soil-lime mix for improvement of base material in road construction, as proposed. by Ingles and Metcalf (1972). The flexural stress versus deflection curves has been found to be approximately linear for both cement and lime stabilized samples. Compared with the illltreated samples, flexural strength and modulus of the cement and lime stabilized samples increased considerably, depending on the additive content, compared with the untreated sample, the flexural strength and modulus of cement -treated samples increased up to 5.5 times and 5.3 times respectively, while for lime treated samples the respective increases were about 2.4 times and 2.6 times respectively. The loss in soil-cement of cement treated samples reduced with the increase in cement content. Although, the cement-treated samples did not meet the PCA (1956) durability requirements, the samples treated with 3% and 5% cement however, fulfilled the requirements as suggested by Compendiwn 8 (1979). It was found from comparison that the values of qu, CBR, flexural strength and flexural modulus of the cement-treated samples of Bashundhara were significantly higher than those of the lime-treated samples. Moreover, it is executed that compared with soil-lime mix, soilcement mix would be much more durable in the weather conditions of tropical regions. It could be concluded that the cement stabilization of the reclaimed soils studied would be more suitable than lime stabilization for their use in various pmposes. From previous researchers' findings (between 1984-2001) it has been found that eighteen regional soils of Bangladesh has so far been stabilized with different percent of cement and lime. Among them eleven soils were stabilized with. cement and twelve soils were stabilized with lime. In general Unconfined Compressive Strength and CBR value increase with increase of cement (%). The range of Unconfined Compressive Strength is between 51.8 kN/m2 to 4304 kN/m2. Also flexural strength and modulus increase with increase of cement (%). The range of flexural strength is between 26.9 kN/m2 to 286 kPa and flexural modulus varies between 17.3 MPa and 136 MPa. Durability of cement stabilization has been calculated by measuring soil-cement loss, which ranges from 10.6% to 42.7%. Soil-eement loss decreases with the increase of cement (%). In general Unconfined Compressive Strength and CBR values increases with the increases in lime content (%). The range of Unconfined Compressive Strength is between 39.3 kPa to 3452 kPa and CBR between 4 to 70. Three regional soils were investigated to find the flexural strength and modulus. For all the cases flexural strength and modulus increases with increase in lime content (%). The ranges of flexural strength are between 47.3 kPa to 243 kPa and flexural modulus varies from 23.3 MPa to 71.2 MPa