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The paper deals with the experimental investigation aimed at the continual monitoring of the process of setting and early hardening in cement pastes and mortars using the measurement equipment Vikasonic. The measurement principle consists in measuring the time of ultrasonic pulses transit through a test specimen placed between two ultrasonic transducers. This innovative method of measurement could in the future suitably complement or, in some cases, completely substitute the measurement of setting in cement composites using the Vicat apparatus. The pilot measurement results performed on the cement pastes and mortars are presented in the paper.

This paper describes an experiment focused on monitoring the development of the modulus of elasticity and the compressive strength of composites that are based on alkali‑activated slag (AAS) during the first 28 days of ageing. The test specimens were tested at the age of 3 and 28 days using two non-destructive methods (ultrasonic pulse and resonance methods) to determine the value of the dynamic modulus of elasticity. Subsequently, the same specimens were used to determine the static modulus of elasticity using compressive stress test, during which the behaviour of the composite was monitored by equipment for recording the acoustic emission in the material. The result of the experiment is the evaluation of the behaviour of the AAS composite in regard to the development of its modulus of elasticity and compressive strength, as well as in regard to the acoustic emission method during loading.

This paper deals with the influence of the coarse aggregate grain size on the frost resistance of concrete. For the purpose of the experiment, three types of concrete were produced, varying only in the maximum grain size of the used natural aggregate. The evaluation of the frost resistance of concrete is based on non-destructive (NDT) dynamic and static testing methods. The results of the experiment indicate influences of the aggregate used in the production of the concrete on the results of its frost resistance.