Abstract
In this thesis the effect of moisture in the surface layers of concrete on the permeation properties measured using the 'Autoclam' is investigated. A literature survey indicated two main ways of removing the influence of moisture on these tests - to assess the moisture condition of the concrete and allow for it, or physically to alter the moisture state of the concrete prior to permeation testing.A series of laboratory tests was undertaken to investigate the influence of different moisture conditions in the concrete on 'Autoclam' air permeability and sorptivity measurements. An analysis of the results indicated a unique relationship between the air permeability and the relative humidity recorded in a 10 mm deep drilled hole. A linear relationship was found between the sorptivity and the relative humidity.
A theoretical study of the effect of temperature on air permeability and sorptivity was undertaken and was confirmed by laboratory tests. In addition, an 18 month investigation was carried out on exposed samples of concrete to study the influence of changes in moisture conditions on permeation properties. Significant differences were found between the permeation results obtained for the laboratory and in in-situ concrete. Permeation. Permeation measurements in exposed concrete with a relative humidity greater than 80% were shown to be ineffective in determining the quality of the concrete. On the basis of the in-situ results a procedure has been developed which renders Autoclam permeation test results largely unaffected by the influence of environmental factors in concrete with a relative humidity less than 80%. Thus, Autoclam permeation results obtained from in-situ tests, which were previously considered to be unreliable, can be corrected.
A parallel investigation into the feasibility of preconditioning in-situ concrete prior to permeation tests was also carried out. The application of hot air was found to be more efficient than other methods as a means of removing moisture from concrete. Overall, the use of preconditioning concrete prior to insitu permeation tests was found to be impracticable.
| Date of Award | Jul 1997 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | P.A.M. Basheer (Supervisor) |