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    Comprehensive Testing Techniques for the Measurement of Shrinkage and Structural Changes of Fine-Grained Cement-Based Composites during Ageing
    (Hindawi Publishing Corporation, 2017-01-15) Kucharczyková, Barbara; Topolář, Libor; Daněk, Petr; Kocáb, Dalibor; Misák, Petr
    The paper deals with an experimental analysis focusing on the utilization of a specific measurement technique for determining the development of shrinkage and for monitoring structural changes in fine-grained cement-based composites during their ageing. Advanced measurement equipment and procedure allowing simultaneous measurement of length changes, mass losses, acoustic responses, and temperature development were designed and verified by the experimental investigation. The main scope of the experiments performed was focused on finding the relationships between the characteristics being investigated while maintaining a uniform test setup. For the purpose of the experimental measurement, three fine-grained cement composite mixtures were designed and manufactured. The mixtures differed in the water-to-cement ratio (w/c) and in the amount of plasticizer. The measurement outputs are presented in the form of diagrams showing the relations between the studied parameters, such as relative length changes, mass losses, temperature progress, and acoustic emission (AE) activity during solidification of the composites. The measurement results showed close relations between the examined characteristics. The progress of relative length changes together with the progress of mass losses and temperature development is reflected in the AE activity. The advanced measurement procedure and technique provided valuable information about the behaviour of cement-based composites during early setting and long-term hardening.
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    Experimental Analysis of the Development of Elastic Properties and Strength under Different Ambient Temperature During the Hardening of Concrete
    (Elsevier, 2017-07-20) Kocáb, Dalibor; Daněk, Petr; Misák, Petr; Topolář, Libor; Pössl, Petr
    This paper focuses on the experimental assessment of the degree to which continued exposure to low ambient temperatures influences the concrete modulus of elasticity and compressive strength. The elastic modulus is not a constant; in fact, it can reach very different values in concrete of the same strength class. It is thus important to have knowledge of aspects which have the greatest influence on it. One of the most important factors influencing the modulus of elasticity is the ambient temperature during concrete setting and hardening. The experiment tested the C 35/45 concrete, which was aged at temperatures of +20 °C, +10 °C and +5 °C. The result of the experiment is the determination of the modulus of elasticity and compressive strength in dependence on ambient temperature while comparing the obtained results with previously published findings.