| dc.description.abstract |
This research aimed to determine the effectiveness of sugarcane bagasse ash (SCBA) in stabilizing three local soils. SCBA is an industrial waste from sugar mills. The studied soils are from (i) Brahmanbaria -(Inorganic Silt,ML), (ii) Dhaka - (Lean Clay,CL), and (iii) Faridpur - (Elastic Silt,MH).
The ML soil (LL=40, PL=30, PI=10), became non-plastic with addition of SCBA (3% to 15%). For the CL (LL=41, PL=22, PI=19) and MH soil (LL=63, PL=33, PI=30), Liquid Limit and Plastic Limits reduced slightly in the range of 3% to 6% SCBA and increased beyond 9% SCBA.Alsowith the addition of SCBA from 0% to 15%, forthe CL and MH soils, shrinkage limits increased by 56% and 83% respectively whereas linear shrinkage decreasedby 25% and 29% respectively.
Standard Proctor Compaction tests were conducted on untreated and SCBA mixed
(3% to 15% by weight) soils to determine the compaction characteristics. For all three soils with addition of SCBA, MDD decreased (ML: 15.98 to 14.59 kN/m³; CL: 16.53 to 14.20 kN/m³; MH: 15.25 to 14.00 kN/m³) while OMC increased (ML: 18.0% to 22.0%; CL: 17.0% to 21.5%; MH: 24.3% to 29.5%).
Stress-strain behavior of untreated and SCBA mixedsoil (3% to 15% by weight) weredetermined by unconfined compression tests on specimens prepared at OMC for different curing periods (1 to 16 weeks). For each soil, with increasing SCBA content the unconfined compressive strength (qu) initially increased up to a peak value and then decreased, indicating an optimum SCBA content in the range of 3% to 5%.
For a given SCBA content, strength increased at a faster rate up to about 2 to 4 weeks, after which the rate of increase diminished and at 16 weeks there was little to no further increase in strength. As for example, with 3% SCBA content and 16 weeks of curing,for ML, CL and MH soils, the unconfined compressive strength increasedby 40%, 21%, and 28%, respectively from the corresponding untreated soils. This indicates that the pozzolanic reaction of SCBA occurs more effectively with silty soils than with clay-type soils.
SCBA mixed soils exhibited more brittleness compared to the untreated soil. It was observed that for most soil samples stabilized with SCBA, failure strain (εf) was maximum for one week curing period. It indicates that, with higher curing age, soil stabilized with SCBA become more brittle.
It was observed that for most specimens of ML and CL soils, the secant modulus of elasticity (E50) values became maximum within 3% to 6% SCBA content. For MH maximum values of E50 occurred within 6% to 12%. For a given SCBA content, the E50 values increased with curing period.
The microfabric arrangements of untreated and 3% SCBA mixed (cured for 16 weeks) specimens were observed by scanning electron microscopy (SEM). It was observed that the microstructure of specimens with 3% SCBA signifies a well-coordinated connection among the soil particles compared to untreated specimens. Also, it was found that SCBA reacted with soil particles, formed SCBA-silicate-hydrate
(SCBA-S-H) and SCBA-aluminate-hydrate (SCBA-A-H) gels resulting in cementation among the soil particles and reduced voids. |
en_US |