Influence of crack geometry and crack width on carbonation of High-Volume Fly Ash (HVFA) mortar

Carbonation of concrete results in a drop of the pH which can induce steel corrosion. This is costly to repair and therefore an accurate assessment of the carbonation resistance is required. Carbonation of uncracked concrete has been well-studied. However, in reality many of the concrete stmctures exhibit cracks, but only limited data is available on the influence of cracks on the carbonation process. Two types of cracks in cylindrical High-Volume Fly Ash mortar specimens were investigated: (1) an artificial crack created by pulling out a cast-in metal plate with a thickness of 100, 200 or 300 pm, and (2) a realistic crack created by splitting cylinders and reattaching them with Silicon spacers (with a thickness of 100, 200 or 300 pm). After crack creation the specimens were stored in a carbonation chamber for different durations and the carbonation front was visualised using phenolphthalein. This paper reports on the influence of the crack width and the crack geometry on the C02 ingress. Artificial cracks with different crack widths did not show a difference in carbonation front. On the other hand, a significant difference could be observed for realistic cracks with different crack widths; realistic cracks with a nominal crack width of 100 pm induced a substantially lower carbonation depth. This demonstrates the influence of crack tortuosity on carbonation; the smaller the crack width, the larger the influence of the tortuosity. Comparing artificial cracks to realistic cracks, it could be concluded that the carbonation depth is lower for realistic cracks. Due to the wall effect near artificial cracks, more pores can be found in the crack area which makes them more susceptible to C02 ingress.

ISBN:9783030765514

Publication year:2021

Accessibility:Closed