Abstract
A method for estimation of the thickness of transition zone is proposed by calculating the coarse pore volume in transition zone from discrepancy between pore size distribution of hardened mortar and concrete and hardened cement paste using specific surface area of aggregate. Thickness of layer of coarse pore in transition zone of mortar and concrete at the age of 28 days is calculated at 14.6μm and 12.3μm, respectively, and average thickness of transition zone in mortar and concrete is estimated at 30μm and 25μm, respectively by the method proposed. These values coincide well with those determined by SEM observation. Transition zone in mortar and concrete is generally formed at 3 days after placing mortar and concrete and increases in its thickness reaching the maximum value at 7 days and gradually decreases in its thickness with age although the change is not remarkable especially in concrete. Estimation of development strength and explanation of the difference of strength development between cement paste, mortar and concrete can be obtained from the time dependency of thickness and pore structure of transition zone.
