Use of additives to enhance the performance of fly ash in ground improvement works | |
| Author | Shahid, Muhammad Ejaz |
| Call Number | AIT Thesis no.GE-98-30 |
| Subject(s) | Soil stabilization Fly ash |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Mae - Moh fly ash, Thailand has a very low amount ofreactive silica, which plays an important role in pozzolanic reactivity. Rice husk ash (RHA) duly burnt in ferrocement incinerator at approximately 400°C was ground in a ball mill and sieved through a US sieve # 60 containing approximately 90% reactive silica. This was used in conjunction with Mae - Moh fly ash (FA) produced by Mae - Moh power plant and cement (C). To determine the optimum contents of RHA and FA at constant amount of cement, Bangkok soft clay (depth 3.5-4m) was mixed with varied ratios of 4-20%RHA, 20-4% FA and 6% cement while maintaining a pozzolan quantity of 24% for the total. Unconfined compression tests were performed to determine the strength gain behavior with time and optimum content ofRHA required to enhance the performance of FA with 6%C. Bangkok soft clay with 18%RHA+6%FA+6%C with a curing period of 28 days exhibited maximum unconfined compressive strength (52 t/m2 ). This compressive strength is higher than that of 5% lime (20.5 t/m2 ) and 5-10% cement (7.5- 31 t/m2 ) for the same curing period due to unique gradation of mix and complete pulverization of Ca(OH)2 with silica and alumina of additives. The RHA- FA-C ratio has been standardized as 3: 1: 1 (% of dry wt. of base clay) for Bangkok soft clay. Oedometer test results showed considerable improvement in consolidation characteristics of base clay treated with 4-20%RHA+20-4%FA+6%C as compared to lime and cement treated clays. It was also observed that a mix ratio of 18%RHA+6%FA+6%C (3:1:1) shows the maximum increase in pre-consolidation pressure (969kpa) among all RHA treated samples, that is higher than 5-10% cement (115-320 kpa) and 5% lime (220kpa) at a 28 day curing period. RHA-FA-C treated samples show stable consolidation behavior as compared to lime and cement treated samples. A general increase of the coefficient of consolidation and a decrease of the compression and swelling indices due to an increase ofRHA content in conjunction with FA and cement was noticed. Mix of 100% RHA shows a lower void ratio and preconsolidation pressure than 100% FA and untreated clay. CIU test results indicated the mix of 12-18%RHA+12-6%FA+6%C showed a lightly over-consolidated behavior even at higher pre-shear consolidation pressures. A higher pore pressure response was observed in RHA-FA-C treated samples than those treated with lime and cement. However, 18%RHA+6%FA+6%C treated samples at a curing period of 14 days provided effective shear strength parameters (c'= 1.27ksc and f = 30°), an improvement over 5% lime (c'=0.23ksc, f =33.2°) and 5% cement ( c'=0.17ksc, $ = 29.4°) which had been cured for 28 days. |
| Year | 1999 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Balasubramaniam, A. S.; |
| Examination Committee(s) | Bergado, D. T.;Der Guey, Lin; |
| Scholarship Donor(s) | Ministry of Defence, Government of Islamic Republic of Pakistan; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1999 |