A model for simulating concrete shrinkage taking into account the effect of aggregate restraint | |
| Author | Thanin Deesawangnade |
| Call Number | AIT Thesis no.ST-94-29 |
| Subject(s) | Concrete--Expansion and contraction Aggregates (Building materials) |
| Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Durability design has the merit of relating everything in the construction and maintenance to the design. Shrinkage is one of the subjects concerned not only with the durability but also with the mechanical properties. Va1ious models had been proposed to simulate the effect of aggregate restraint on shrinkage of concrete, However, there had been no model proved to be effective for the whole range of aggregate content, especially at the range which is closed to densely packed aggregate. From the study of Tinapat, et al [2], concrete was considered as a two-phase material consisting of paste and aggregate phases. The reason was that shrinkage was regarded to occur only in the paste phase whereas the aggregate phase was considered to restrain the s1ninkage by their pa1ticle interaction. However the stiffness of paste and aggregate phases which is necessary for the derivation of the concrete shrinkage model has not been separately proposed. In order to improve the model for simulating concrete shrinkage, the stiffness of paste and aggregate phases has to be proposed separately. In this study, the stiffness of paste phase was adopted from the study of Kouiti, Y. et al [13] and the stiffness of aggregate phase was proposed by introducing micro model for solid phase which was modified from the contact density model for deriving stiffness of aggregate in high stress condition proposed by Tangtennsirikul, S., Maekawa, K [7]. The stiffness of aggregate restraint was found to be related to the volume concentration and the strain of aggregate phase. The stiffness of aggregate phase is proposed by introducing the micro model of solid phase in which the initial contact areas of fine and coarse aggregates play an important role and is taken into account. Initial contact areas which are obtained from linear combination of the initial contact areas of fine and coarse aggregates are proposed to find the initial contact area for bina1y mixture. However the effect of water-cement ratio, one of the properties of paste phase, was also investigated. The results show that the stiffness of aggregate phase was not much dependent on water-cement ratio of paste phase. -iii- The concrete shrinkage model was then verified by compa1ing the analytical results with the test results of autogeneous shrinkage obtained :from m01tars, no-fine concrete and concrete. The concrete shrinkage model was also verified on d1ying shrinkage of mortar. It was found from the comparison that the model is effective for simulating the effect of aggregate restraint against concrete shrinkage. This research was also investigate the effect of chemical expansion, which is caused by class C fly ash, on drying shrinkage of paste. The chemical expansion was expected to be efficient for reducing drying shrinkage of cement paste. Finally the effect of submerged curing period on both cement paste with and without fly ash was examined. From the results, it can be concluded that class C fly ash :from Mae-Moh can be used as a pozzolonic material to reduce drying shrinkage. It can be pointed out that longer submerged curing period gives rise to smaller drying shrinkage for both pastes with and without class C fly ash, however the effect does not improve when curing period is longer than 6 days for both pastes with and without class C fly ash. |
| Year | 1994 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Aoyagi, Yukio ;Somnuk Tangte1msirikul |
| Examination Committee(s) | Worsak Kanok-Nukulchai ;Pennung Warnitchai |
| Scholarship Donor(s) | The Government of Germany (DAAD) |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1994 |