Abstract
When proximate and locally available materials to be used for road pavement construction are deficient to meet the nominal requirements of the intended flexible pavement layer; then stabilization becomes necessary. Therefore, this paper presents the results of laboratory experiments undertaken to assess the effect of sugarcane Bagasse Ash (BA) as an admixture to cement stabilized Black Cotton Soil (BCS). The Bagasse was obtained from a dump-site at Kasuwan Shanu market Bauchi and was incinerated at a controlled temperature range between 600°C and 700°C to get the BA, while the BCS was obtained along Kanawa-Jauro-Gotel road, in Yemaltu-Deba, Gombe, Nigeria. The specimens were prepared by admixing the four blends of cement stabilized BCS (using 0, 4, 6, and 8% cement) with stepped percentage of BA (0, 1, 2, 3 4, 5, and 6%) by dry weight of the BCS. The experiments carried out on both the natural and treated BCS include; Atterberg’s limits, Sieve/hydrometer analysis, Free swell, Compaction, soaked California Bearing Ratio (CBR), and Unconfined Compressive Strength (UCS) at 7, 14, and 28 days curing periods. The BCS was classified as A – 7 – 6 (68), and CH (high plasticity clay) using the American Association of State Highway and Transportation Officials (AASHTO) and Unified Soil Classification System (USCS) respectively. In addition, the soil was also categorized as High swell potential BCS under Nigerian Building and Road Research Institute (NBRRI) classification. It was found that; addition of BA to cement stabilized BCS affected their compaction characteristics, and improved both the soaked CBR, and the UCS. On the other hand, the addition of BA alone does not improve the strength properties of the natural BCS. The optimum blend was achieved with 5% BA as admixture to BCS stabilized with 8% cement, this blend gave a 7-days soaked CBR of 73% and a UCS value of 851 kN/m2 after curing for 7 days therefore, satisfied the sub-base requirements of the Nigerian Federal Ministry of Works. This study finally recommends the use of 5% BA with 8% cement for BCS stabilization for use as sub-base in flexible pavement construction.
Highlights
Expansive soils are soils that are highly sensitive to moisture variation; they show large volume change when exposed to moisture content fluctuations [1] [2] Because the cotton plant grows well on this soil type it is often referred to as Black Cotton Soils (BCS), they have colours ranging from light-grey to dark-grey and black [1] [3].In Nigeria BCS are often found in North Eastern part of the country, and it is believed that these soils derived their origin in Nigeria [4]
The natural BCS is very poor for pavement engineering applications
73% Soaked (7-days) California Bearing Ratio (CBR) value was achieved with 8% Cement-5% Bagasse Ash (BA) stabilization of the BCS
Summary
Expansive soils are soils that are highly sensitive to moisture variation; they show large volume change when exposed to moisture content fluctuations [1] [2] Because the cotton plant grows well on this soil type it is often referred to as Black Cotton Soils (BCS), they have colours ranging from light-grey to dark-grey and black [1] [3].In Nigeria BCS are often found in North Eastern part of the country, and it is believed that these soils derived their origin in Nigeria [4]. Expansive soils are soils that are highly sensitive to moisture variation; they show large volume change when exposed to moisture content fluctuations [1] [2] Because the cotton plant grows well on this soil type it is often referred to as Black Cotton Soils (BCS), they have colours ranging from light-grey to dark-grey and black [1] [3]. Deposits of BCS show a general pattern of cracks during the dry season [3]. BCS are not the same in their properties and behaviors. The Nigerian Building and Road Research Institute (NBRRI) have classified BCS into three categories (Table 1) based on two determinable parameters due to their
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