Agrega hacminin ultra yüksek performansli betonun büzülme, reolojik ve mekanik özelliklerine etkisi

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Rheology and shrinkage are the key features that should be controlled to perform a successful casting process and obtain a durable ultra-high performance concrete (UHPC). It is anticipated that cast-in-situ applications of UHPC will increase in the near future, so the studies on early-age properties of UHPC have come into prominence. However, there is still no standardized method for mix design of UHPC that can ensure the desired performance. High amount of cement and low water/binder ratio increase the shrinkage values, which also increase the crack formation risk especially at early-age. The basic variable of mix proportions that determines the rheological and shrinkage properties is aggregate volume and accordingly paste volume. In the scope of this experimental study, influence of volume fraction of quartz aggregate on rheological, shrinkage, and mechanical properties of UHPC was investigated. The results showed increasing the aggregate volume led to sharpen pseudoplastic behaviour of UHPC. To be able to produce a self-compacting UHPC, upper limit of aggregate volume was found 45%. Both autogenous and drying shrinkage can be limited by increasing the aggregate volume. Early-age autogenous and drying shrinkage are far more than the shrinkage measured after demoulding during 90 days. Necessary precautions, thus, should be taken as of casting stage.