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Monitoring the development of properties in fresh cement paste and mortar by ultrasonic waves

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2009
Kasap Keskin, Özlem
The determination and following up the development of properties during the fresh state and early ages of concrete are important in order to schedule the work and to obtain the desired properties in the hardened concrete. As the traditional methods such as Vicat and Penetrometer mostly depend on the experience of the operator and do not provide a continuous picture of the development of properties, reliable and objective non-destructive test methods are needed for the quality control of fresh concrete. The purpose of this thesis is to observe the development of properties of fresh pastes and mortars continuously by longitudinal ultrasonic waves. For this purpose, cement pastes and mortars with three different w/c ratios were prepared with ordinary portland cement. The ultrasonic pulse velocities were determined continuously during hydration. The setting times were also determined by standard test methods. The flexural and compressive strength were determined at 1, 2, 3, 7 and 28 days by standard test method and the volume of permeable pores were also obtained at the same ages. Lastly, the heat of hydration of cement pastes of similar w/c ratios were determined by isothermal calorimetry. UPV (Ultrasonic Pulse Velocity) development was compared with the results of standard tests applied on the samples. The results revealed that the UPV is a useful method in monitoring the hydration process of cementitious materials.