Effect of interfacial transition zone on properties and microstructure of concrete

Articles in Press

Document Type : Research Article

Authors

1 Professor, Department of Civil Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran

2 PhD candidate, Department of Civil Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran

Abstract

Natural aggregates with high silica and w/c of 0.45 were used. To investigate the effect of the interfacial transition zone (ITZ) on the properties of concrete, 30 samples were examined in the form of 10 mixtures in the age range of 7 to 180 days; the selected mixtures was determined by the Taguchi method. Experiments were conducted to determine the properties concrete and finally its microstructure. The results showed that with the increase in the age, the mechanical properties improved; there was a decrease in volumetric water absorption, pressure water penetration and accelerated chloride ion penetration (RCPT), and a significant increase in the electrical resistance of the samples. Also, the amount of crystalline phase of calcium oxide and the number of large pores decreased and the hydrated calcium silicate phase of the transition region increased, which led to the improvement of the quality of the microstructure. With increasing age, hydrated calcium silicate and calcium carbonate increased by 24% and 21.5%, respectively; the compressive strength and electrical resistances also increased by 10.3% and 48.6%, and the accelerated penetration of chloride ions increased by 5.2%. Upto 30 micrometers, due to the disturbance in the boundary area, no acceptable correlation between the ratio of constituent elements and concrete properties was obtained. from 30 to 50 micrometers, linear relationships with R2 as 0.85 were established between the weight ratio of Ca/Si with compressive strength and the RCPT; so by reducing Ca/Si by 82%, the compressive strength increased by 10.3% and penetration by 5.2% decreased.

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Amirkabir Journal of Civil Engineering

Articles in Press, Accepted Manuscript
Available Online from 14 January 2025

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