Authored by BR Phanikumar*
Abstract
Expansive soils have a tendency to undergo volumetric changes corresponding to changes in water content. As a result, civil engineering structures founded in these soils are severely distressed. This has caused a huge financial loss, it is, therefore, necessary to reduce volumetric changes of these soils by physical and chemical alteration. This paper presents experimental results on a remolded expansive clay blended with varied amounts of quarry dust and lime. Compaction characteristics, stress-strain characteristics, unconfined compressive strength (UCS) were studied.
Keywords: Expansive soils; Physical alteration; Chemical alteration; Quarry dust and lime
Introduction
Introduction
Expansive soils are highly problematic because of their tendency to undergo risky volumetric changes consequent upon changes in water content [1]. These volumetric changes happen in alternate seasons of winters and summers. These alternate swelling or volume increase and shrinkage or volume reduction cause damage to lightly loaded structures founded in them such as foundations, retaining walls, pavements, airports, sidewalks, canal beds and linings [1,2]. To address the problems posed by expansive soils, various innovative foundation practices have been devised which can be broadly classified as (i) avoiding expansive material, (ii) mechanical, physical or chemical alteration and (iii) adopting special foundation techniques. In physical alteration technique, granular material is mixed with expansive clay to minimize heave [3-5]. In chemical alteration, addition of chemicals to expansive clay alters the nature of clay minerals thereby reducing heave. Of all chemicals tried, lime has been found to be most effective and economical additive. This paper presents an experimental work on a remolded expansive clay blended with quarry dust (QD) and lime in varied amounts. The effect of quarry dust and lime on the compaction characteristics and stress-strain behavior was studied. The values of unconfined compressive strength (UCS) were reported.
Experimental Investigation
A remoulded expansive clay of free swell index (FSI) 120% was used in testing. Table 1 shows the index properties of the clay. Further, quarry dust and lime were also used as blend materials. Quarry dust was varied as 0%, 5%, 10%, 15%, 20%, 25% and 30% by dry weight of the soil; and lime was varied as 0%, 1%, 2%, 4% and 6%, it may be mentioned here that lime was added in different quantities to the blend of expansive soil and 30% quarry dust gave the highest MDD. The tests conducted were standard Proctor compaction tests and the unconfined compression tests. The standard proctor compaction tests on the unblended expansive clay and the clay blended with quarry dust and lime were performed accordingly to ASTM 2000 D698 a. The unconfined compressive strength tests were performed on the unblended clay and the clay blended with quarry dust and lime were performed accordingly to ASTM 2000, D2166 on cylindrical samples of length 76mm and Diameter 38mm. The effect of curing period on UCS were also studied (Table 1).
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