Study on Frost Damage Degradation in Hydrated Cement Using Hydrophobic Compound

Abstract

The objective of this study is to improve the freezing and thawing resistance of NonAE concrete. It is believed that freezing of macroscopic water in meso capillary pore of hydrated cement causes the frost damage due to freezing and thawing. In this study, it was confirmed that applying a hydrophobic compound into the concrete to block the continuity of meso capillary pore decreases the freezing water by suppressing ice crystal penetration. Further, the effective particle size of the hydrophobic compound was 10-110 μm. Thus, freezing of water in capillary pores in the range of 10 to 110 μm is the main cause for the deterioration due to freezing and thawing. It is anticipated that this technology, without entrained air, can be applied to produce concrete for better performance in freezing and thawing environment.

Visualization of Hydrophobic Compound Distribution in Hardened Cement Paste Using X-Ray Ct

“…The damage occurs when the water pressure P exceeds the tensile strength of the HCP, and this equation also indicates that P is affected by the distance between the freezing location and the air void. Based on this model, Nishi et al [15] reported that hydrophobic compounds are finely dispersed as oil droplets in the HCP and decrease the water pressure by shortening the distance between the freezing location and the air void, thereby suppressing the frost damage. However, they also reported that the penetration space of water reaching the oil droplets is only the volume change with the decreasing temperature, and that alone cannot relieve pressure via the 9% volume expansion due to the water freezing.…”

“…This tendency is easer However, the air void size in the HCP specimen containing AE was smaller than that of specimen containing P and SO. Nishi et al [15] assumed that the hydrophobic compounds existed saturated in the pore as oil droplets. However, from the sectional X- ray CT images of the P and SO specimen, the black area was considered to be air bubbles rather than oil droplets.…”

“…As shown in Fig. 1, the air bubbles were considered to be oil droplets created by the hydrophobic compounds finely dispersed in the hardened cement paste (HCP) [15]. It is explained that the inter-bubble spacing coefficient (including oil droplets) became smaller as the oil droplets behaved as air bubbles in the HCP.…”