| Summary: | 碩士 === 國立臺灣海洋大學 === 河海工程學系 === 107 === This study is based on the feasibility of cement-based crack injection materials blended with different proportions of high-aluminum cement (calcium aluminate cement) and type I cement. The goal is to find out that the injection material that can meet the requirements of the EN1504-5 specification, i.e., the passing time is within 8 minutes, and the 28-day splitting strength exceeds 3MPa. The experimental method includes the passing time test, the splitting strength test, the viscosity test, and the mortar compressive strength test.
The research results show that the injection material with water-to-gel ratio of 0.475, 80% type I cement accounts and 20% high aluminum cement, and 2.0% boric acid, can reach the best splitting tensile strength. The splitting strength obtained by this mix is even higher than that using type I cement alone while the passing time is still within 8 minutes (388 sec). Through the splitting strength values of different passages, it is found that blended cement may have a phenomenon of segregation. From the viscosity test, it was found that when the amount of high alumina cement increased, the viscosity of the slurry decreased, which is consistent with the results of the passability test (passing time).
The reason may be explained as the followings. First, the carboxylates superplasticizer may be not effective to disperse the high- aluminum cement such that when the amount of high-aluminum cement increases, the reaction is faster, and quick-setting, clustering, flocculation, etc. occur, and results in blockages. The mortar compressive strength test showed that when the curing conditions can ensure sufficient water, the mortar with type I cement alone had the best strength. When the amount of type I cement is lower, the compressive strength is lower. However, when the curing condition follows the EN-1774 specification (21oC, R.H.=60%) the splitting strength increased as the amount of high-aluminate cement increased which is contradictory to the results of compressive strength. The reason comes from the different curing condition.
Keywords: passing time test, splitting strength test, viscosity test, mortar compressive strength test
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