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EFFECT OF SOME FINELY DIVIDED MINERAL ADMIXTURES ON DRYING SHRINKAGE OF END RESTRAINED CONCRETE BEAMS
Basim Thabit Al-Khafaji Dr.Mahdi Saleh Essa
University of Babylon University of Babylon
College of Engineering College of Engineering
Department of Civil Engineering Department of Civil Engineering
Abstract
End restrained steel moulds having a channel section were used to study restrained shrinkage cracking. In these moulds concrete specimens from different mixes were cast to measure the free and restrained shrinkage strain. Three local admixtures of (FDMA) were used which are lime stone dust (LSD), Silica flour (SF) and bentonite (Bt). Three levels of addition were used for each type, (1.5%, 3% and 4% by weight of cement) for (LSD), (2.5%, 5% and 8% by weight of cement) for (SF) admixture and (2.5%, 4.5% and 6% by weight of cement) for bentonite admixture. The experimental results illustrate that For concrete specimens with different levels of (LSD), the free shrinkage strain decreased at early and later ages, while no noticeable effect was observed in free shrinkage strain with (SF) at all ages but it increased significantly with (Bt) addition .The increase of content of any admixture used leads to a decrease in cracking time, crack width and creep strain at (cracking time). Mathematical models were developed in this study. Non-linear regression estimation is used to evaluate good coefficient correlation with less difference between the observed value and predicted value (df) and with fewer variables introduced in them
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- DRYING SHRINKAGE OF END RESTRAINED CONCRETE BEAMS
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