Drying shrinkage of fibre-reinforced lightweight aggregate concrete containing fly ash

Lightweight aggregate concretes containing fly ash with a compressive stren gth between 61 to 67 MPa were produced. The lightweight aggregate; used was sintered fly ash. The concretes were reinforced with tither polypropylene or steel fibres. The fibres did not affect the compressive strength, but di d increase the tensile strength of these concretes. The modulus of elastici ty of all the lightweight concretes tested was about 21 GPa, compared to 35 GPa for the normal-weight concrete. Fibre reinforcement did not affect the value of the elastic modulus. This type of lightweight concrete, containin g fly ash as 23% of the total cementitious content, resulted in long-term s hrinkage that is nearly twice as large as normal-weight concrete of somewha t similar:strength. Polypropylene fibre reinforcement did not reduce drying shrinkage, while steel fibres did. Early shrinkage behaviour of this type of lightweight concrete was similar to normal-weight concrete. However, the rate of shrinkage of the lightweight concrete remained constant until near ly 100 days of drying. This is different from normal-weight concrete that s lowed appreciably after 56 days. Shrinkage :of:normal-weight concrete stabi lised after 400 days, while shrinkage of lightweight concrete did not appea r to stabilise after a similar period of continuous drying. (C) 1999 Elsevi er Science Ltd. All rights reserved.