Effect of accelerated curing conditions on strength development of high strength mortars containing rice husk ash and pulverized fly ash | |
| Author | Surachai Leelaleartlaew |
| Call Number | AIT Thesis no.ST-00-6 |
| Subject(s) | Fly ash Rice hull ash Mortar--Additives Concrete--Testing |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | This study is aimed at investigating the effect of accelerated curing conditions on the strength development of high strength mortars containing different types of pozzolana. The high strength mortars possess the compressive strengths in the range of 90-100 MPa. Main parameters are types and percentage replacements of pozzolana, and curing conditions. The accelerated curing condition adopted in this experiment involves the immersion of mortar specimens in 60°C and 90°C hot water for early duration of 3 days. Two types of pozzolana are investigated namely rice husk ash (RHA) and pulverized fly ash (Pfa) obtained from Mae-Moh lignite power plant. The percentage replacements of both pozzolanas are 0%, 10%, 20% and 30% by weight of cement. Ordinary Portland cement (OPC) Type I is used throughout this experiment. The water-cementitious ratio is kept constant to eliminate the effect of water on the strength of mortars. The dosage of superplasticizer is varied for maintaining the same flowability in fresh state. The compressive strengths of mortar specimens are tested at the ages of 3, 7, 28 and 56 days. For comparison, tests on mortar samples cured under conventional condition are also performed. Test results indicated that curing temperatures during the early ages of mortars played an inportant role in the strength development of high strength mortars. Like ordinary Portland cement mortar, mortars containing rice husk ash and pulverized fly ash had a potential of achieving high early strengths at early ages when the curing temperature was raised. Hot water curing resulted in an extraordinary high early strength and an irrecoverably lower long-term strength compared to the conventional curing condition in normal water. Preliminary tests in this study revealed that using a hot water technique, a compressive strength of control mortar as high as 72% of the 28-days strength obtained under normal condition can be conducted with only 3 days cured in 90 °C hot water, but the 28-days compressive strength of the mortar was only about 73% of the control strength. Furthermore, the compressive strength at the age of 56 days was slightly decreased to be only about 71 % of the control strength. This might be explained by the adverse effect of the high early curing temperature on the long-term strength development. In addition, the 56-days compressive strength of fly ash mortar was significantly higher than the other mortars and the differences became higher the higher curing temperature. In other words, the adverse effect of high temperature curing on long-term strength of high strength mortars could be compensated by the replacement of cement by fly ash. Finally, based on the experimental results, predicting equations for the compressive strength at a required maturity of high strength mortars containing rice husk ash and pulverized fly ash cured under different temperatures were proposed. |
| Year | 2000 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pichai Nimityongskul; |
| Examination Committee(s) | Nii, Kazuyoshi ;Takewaka, Koji; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2000 |