The present invention is directed to a cement composition admixture capable of reducing drying shrinkage and cracking resulting therefrom.
One of the major disadvantages of conventional cement compositions is that they tend to shrink during curing of the composition. This shrinkage results in cracks, and other defects in the resultant structure. Such cracks have both appearance and physical defects to the structure. For example, water can enter in the cracks and further deteriorate the structure through freeze-thaw pressures exerted by the water on the cement composition.
Various admixtures have been suggested as useful in reducing drying shrinkage and the resultant cracking. Japanese Patent Laid-Open Application 81/37259 and Japanese 87/10947 disclose the use of alcohol-alkylene oxide and alkylphenol-alkylene oxide adducts as useful for this purpose. However, these materials must be used in large dosages which causes their usage to be too expensive for practical use. C.sub.4 -C.sub.6 alkyl alcohols, as disclosed in U.S. Pat. No. 5,181,961, have been suggested for use in inhibiting drying shrinkage. However, the alcohols are not highly effective under dry conditions and they tend to leach out under any wet condition encountered. In addition the lower alcohols have high vapor pressure at ambient conditions and are, therefore, difficult to handle.
Amino alcohols have been previously used in the cement industry. For example, lower alkanolamines, such as triethanolamine, diethanolamine and the like have been used, in small quantities, as a grinding aid to form cement powder from clinker nodule materials. Higher (C.sub.4 - C.sub.8) trialkanolamines, such as triisopropanolamines, when added in very small amounts, provide enhanced strength to the resultant cement composition. Amino alcohols have been described in U.S. Pat. No. 5,176,152 to be a stabilizing agent for microsilica slurries to prevent the slurry from gelation and settlement of solids. Mortars can be formed from cement and the silica slurry composition. Finally, U.S. Pat. No. 3,583,880 teaches that shrinkage of porous organic products can be reduced by applying an alcohol, a monoalkyl ether or an amino alcohol to the surface of an already formed inorganic product.
A need continues to exist for a cement composition admixture and a resultant cement composition capable of inhibiting drying shrinkage. The admixture must be inexpensive, readily handleable at the job site and provide the desired inhibiting effect at low dosage levels.