| Author | Tanin Osotcharoenphol |
| Call Number | AIT Thesis no. ST-91-20 |
| Subject(s) | Concrete--Chemistry
|
| Note | A thesis submitted in partial fulfillment of the requirements
for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Abstract | This research is aimed to set up a more generalized mathematical model for heat generation
process that is applicable to several types of cement. Cement particle is regarded as multi-component
material composed of four main compounds of cement i.e. ~A, C4AF, ~S and C2S. Each of these
chemical compounds is treated to have the same hydration characteristics as a single compound
when hydrate alone. C3A and C4AF are grouped according to their hydration rate as the most rapid
hydrating compound whereas C3S and C2S are regarded as the intermediate and the slowest hydrating
compounds respectively. Instead of using the conventional procedure, where the heat generation
rate is a function of time only, the coupled analysis of heat generation and heat conduction is
introduced. The heat generation rate is considered to depend upon the temperature and past hydration
process. The rate of heat generation process of cement compounds are calculated based upon the
Arrhenius's equation. The activation energy and maximum heat generation rate are assigned corresponding to the hydration characteristics of each compounds. The heat generation rate of cement
is computed from the summation of weighted heat of hydration generated by individual component
comprising cement.
An experimental program is performed to verify the analytical model. Thermocouples, which
are used as a temperature measuring device throughout the test program, are installed at various
positions of specimen before the placing of concrete. Thereafter, cubical concrete blocks insulated
all sides by foam plates with 2 inches in thickness except the top surface are casted with different
mix proportions and the temperature rise of concrete samples are measured at interval of 1 hour
upto 7 days.
The analytical results exhibit good corresponding with the experimental curves. It is noted
that the peak temperature obtained from the experiment and computational method occurred almost
at the same time, around 11 hours after placing of concrete. In the case of ordinary Portland cement,
the peak temperature is slightly lower than the predicted values. When cement partially replaced
with fly ash is introduced, the peak temperature become more of less the same. However, the
temperature rise predicted by the proposed model increase more slowly than the measured temperature while decreasing rate of temperature after the peak value become higher than the experimental results. The comparison between the temperature rise curve obtained from multi-component
model and temperature predicted by existing model is also carried out and satisfactory correlation
is attained. It can be realized that the multi component model introduces a new approach to deal
with prediction of temperature rise of any type cement possessing different chemical composition. |
| Year | 1991 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Maekawa, Koichi ;
|
| Examination Committee(s) | Karasudhi, Pisidhi ;Pichai Nimityongskul |
| Scholarship Donor(s) | Government of New Zealand |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1991 |