Computerised evaluation of the early age of shrinkage in concrete

• Problem of shrinkage of concrete in literature
• The weakness and advantages of the previous research in measuring concrete shrinkage
• Test stand description and measurement methodology allowing automatic measurement of early shrinkage of concrete
• Tests of the early stages of shrinkage of concrete
• Impact of: cement, aggregates, the concrete care on the early shrinkage of concrete

Shrinkage is a natural phenomenon accompanying drying processes occurring in nature. Particularly acute it is on dirt roads in Africa and Asia, as in the dry season, at high ambient temperatures and low relative humidity, effects of drying are surface irregularities and even landslides. Fresh and hardened concrete mix is subjected to similar phenomena. The mechanism of action of shrinkage in concrete is more complicated than in the environment of cohesive soil, since in the initial phase of hardening chemical processes associated with cement hydration, and after hardening physical processes associated with the adsorption or loss of moisture from the environment during drying, lead to volume reduction. These influences can be precisely separated and indication of their significance for the quality of the concrete structure can be performed only by setting the deformation of concrete in the phase of the laying, caring and operation. The problem of continuous strain measurements in concrete is discussed in this publication, in which a review of existing methods for measuring shrinkage was performed in the period from the start of the modern concrete structures (USA, Europe after 1900 years) to modern times, in which the simple mechanical method of measuring shrinkage was replaced by modern electronic sets of measurement, enabling highly accurate measurements since the moment of production of concrete mix. The exact description of the process of the passing time — the deformation, enables making decisions to rectify or limit unfavourable shrinkage phenomena in the concrete (adding contraction admixtures, water care, covering with foil, use of the sealing and reflecting solar radiation surfaces). Proposed and tested by the authors of the article set-up for automatic control of shrinkage phenomena occurring in the concrete meets the above mentioned functions in both scientific discovery and relevant to practice application research.