Modelling early age drying in fibre-reinforced concretes

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Title: Modelling early age drying in fibre-reinforced concretes

Author(s): Tara Rahmani; Mehdi Bakhshi; Barzin Mobasher; Mohammad Shekarchi

Publication: Special Publication

Volume: 310

Issue:

Appears on pages(s): 141-150

Keywords: Fibre-reinforced concrete, drying, plastic shrinkage, cracking, diffusivity.

Date: 3/17/2017

Abstract:
Plastic shrinkage cracking due to a high rate of evaporation detrimentally affects durability and serviceability of concrete structures. The effect of different types of fibres to control these cracks, including steel, glass, polypropylene, and polyolefin fibres on the moisture loss and evaporation rates is investigated by performing ASTM C1579 tests. Using a dual stage methodology of constant drying rate period (stage I) and falling drying rate period (stage II), results are analysed. Moisture diffusivities are computed which in turn can be used for modelling the drying shrinkage and cracking under different environmental conditions. The formation of microcracks is documented using digital photography and processed by image analysis. The results show that moisture diffusivities at stage I drying are similar to each other between FRC and control samples. These magnitudes are approximately 50 times higher than diffusivities at stage II drying. The main difference is observed in stage II drying where the diffusivities in FRC are lower compared to plain concrete. Image analysis results indicate significant effects of fibres on controlling plastic shrinkage cracks.