Date of Award
Master of Science (MS)
Civil and Environmental Engineering
Admixtures, Cement, Cracks, Lining, Mortar, Shrinkage
Cement mortar lining plays an essential role in protecting water supply networks. It protects the internal surface of water pipelines from corrosion and prevents the development of red-water problems in water supply networks. While several factors can cause damage to cement mortar lining, shrinkage cracks are considered one of the main sources of lining failure. Shrinkage cracks are hard to control and can significantly shorten the service life of cement mortar lining applications. Thereafter, the service life of steel pipes can be shortened due to corrosion, which in turn affects the quality of the supplied water.
This thesis describes the effects of shrinkage reducing admixtures on the shrinkage and compressive and bending strength properties of cement mortar lining mixes. A methodology that features laboratory experiments was deemed to be the optimum approach to conduct this study. The effects of three shrinkage reducing admixtures on a reference mix were studied. The reference mix in this study is a cement mortar lining mix that is used by a pipeline engineering and construction company. This company, serving in Saudi Arabia, is also sponsoring this research project. Therefore, practices and standards used in Saudi Arabia are frequently cited in this thesis. A total of twelve mixes were designed to test the effects of using different dosages of three shrinkage reducing admixtures on the reference cement mortar lining mix. Each of the designed mixes was tested for:
1- Flow using the Standard Test Method for Flow of Hydraulic Cement Mortar (ASTM C1437).
2- Shrinkage using the Standard Test Method for Drying Shrinkage of Mortar Containing Hydraulic Cement (ASTM C596).
3- Compressive strength using the Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (ASTM C109).
4- Bending strength using the German standard DIN 1164.
The study demonstrated and described the positive effect of shrinkage reducing admixtures on the shrinkage and bending strength of cement mortar lining. In addition, the results demonstrated and described the negative effect of shrinkage reducing admixtures on the compressive strength of cement mortar lining. The tested dosages of the used shrinkage reducing admixtures showed that they can reduce the drying shrinkage of a mix by 7.5 and 29.1%, decrease its compressive strength by 5 to 16%, and increase its bending strength by 4 and 16.6%
While the highest drying shrinkage reduction achieved by this study was 29.1%, the results indicated that a higher shrinkage reduction can be achieved using a higher shrinkage reducing admixture dosage. In addition, the compressive strength results showed that a shrinkage reducing admixture dosage can be used at a dosage higher than the recommended dosage by the manufacturer and the cement mortar lining mix can still meet the minimum compressive strength requirements. Therefore, it is recommended to consider shrinkage reducing admixture dosages higher than the recommended dosage range during the mix design process.
Ashour, Raed, "The Effects of Shrinkage Reducing Admixtures on Shrinkage and Strength Properties of Cement Mortar Lining Mixes" (2020). Theses - ALL. 423.