A semi-quantitative investigation of the free expansion stage of steel corrosion in fly ash concrete

Abstract

In order to boost the use of fly ash concrete, and improve the accuracy of predicting the durability deterioration degree of reinforced concrete structures due to steel corrosion in concrete, free expansion stage of steel bar corrosion in fly ash concrete was investigated in this paper. Mercury intrusion porosimetry (MIP) was utilized to investigate the porosity and mean pore size at the steel/concrete interface of ordinary concrete and three types of fly ash concrete specimens cast with different amount of fly ash (15%, 30%, and 45%). Based on the proposed prediction model and MIP test results, steel corrosion amount in free expansion stage was investigated quantitatively. The results showed that the content of fly ash had great influence on pore size distribution in concrete. Compared to the ordinary concrete, the maximum corrosion depth of steel bar, the corrosion amount of per unit length steel bar and the corrosion ratio in free expansion stage were decreased slightly (about 1.6%) after adding 15% fly ash replacement. When the replacement increased to 30% and 45%, the maximum corrosion depth of steel bar, the corrosion amount of per unit length steel bar and the corrosion ratio increased about 12.7% and 60.5%, respectively.