RHEOLOGY OF FRESH CEMENT PASTE CONTAINNING CHEMICAL ADMIXTURES MATERIALS

Document Type : Original Article

Authors

1 Prof.Dr., Dean of faculty of engineering.

2 Associ Prof. Dr., Research for Master Degree. Thesis In Civil Engineering.

3 Eng., Research for Master Degree. Thesis In Civil Engineering.

Abstract

Abstract: Understanding the rheology of cement and water is a not a simple task since, the behavior of complicated system various with time and there is still a great deal of work to be done before it is properly understood. Fortunately, fresh cement paste, mortar, at early ages approximate to the Bingham model , and could be tested at two rates of shear, that is ,they require a two point test. All available tests are either empirical or too expensive and could not be used on site, and measure only one parameter . These tests are a single point tests, this means that in each test only one measurement is made, at one rate of shear or under one set of shearing conditions. In this study we used a new simple technique based on dropping a needle from a constant height. The penetration depth is measured at different circumstances different w/c ratios, types of super plasticizer and different percentage of admixture for two types of cement types of cements (OPC type V) (CEMEX ) and OPC type I (HELWAN). Effect of time of testing after mixing and the effect of agitation of the specimens after 30 minutes as well as the effect of the drop height were also investigated in this study. This model although simple and cheap and could be performed on site, also proved to be sensitive in monitoring the effect of different water cement ratio, and various percentages of super plasticizer as well as effect of delay of addition of super plasticizer on the penetration depth of the plastic needle.