| Author | Pokharel, Achyut Prased |
| Call Number | AIT Thesis no.ST-92-18 |
| Subject(s) | Concrete--Permeability
|
| 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 | Today's interest to engineers toward predicting the durability of concrete is the author's
concern of this study. The process of deterioration of concrete structures are partly and chiefly
mediated by movement of water and the situation is more severe in case of alternate wetting and
drying cycles. The problem is multiphase movement of water in concrete capillaries. In this
study, the water movement in wetting cycle with respect to changing water to cement ratios, viz., 40%, 45%, 50%, 55% and 60%, and with varying sand contents, including cement pastes
are conducted in laboratory test set-up conditions. The sorptivities values of the test specimens
are found rather low, i.e., saturated level rise in the test specimens are very low despite the very
high value of surface tensions in representative capillary. Here, a existence of some initial static
resisting force in microscopic level is recognized as necessary.
The previous work done, by Sharma, A., on this regard is enhanced here in two aspects,
one by introducing a static resisting force 11 Yield Shear 11 in microscopic level and the next is
a direct approach is applied to equiliberate the driving force from surface tension on a
representative capillary to all resisting forces generated from the movement of water. The
dynamic resisting force is associated with friction coefficient and rate of level rise. The yield
shears and friction coefficients are computed by model with experimental results for given water
to cement ratios and mix proportions of sands. These parameters are measure of material
properties of a cement mortar.
After conducting this investigations, the model is visualized as a development of interface
channels system, just like a irrigation canal system and a rice field, with inclusion of sand in
cement paste matrix as boulders. First inclusion of sand in dispersed state imparts high resistance
to water movements as the path length increases than in a paste matrix without sand and as the
absorbant agent to take capillary water from cement paste dispersion. On the other side, densely
spaced sand particles are found to develop a sort of continuous interface channels system in
which a rapid water movement is expected and paste matrix is in turn irrigated through these
channels. |
| Year | 1992 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. ST-92-18 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Maekawa, Koichi |
| Examination Committee(s) | Pichai Nimityongskul;Yamaguchi, Hiroki |
| Scholarship Donor(s) | The Government of Germany (DAAD) |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1992 |