A discussion of the paper “Ice in cement paste as analysed in the low-temperature scanning electron microscope,” by P.J.M. Monteiro, A.I. Rashed, J. Bastacky, and T.L. Hayes

✍ Scribed by Xu Amin; S. Chandra

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 64 KB
• Volume: 20
• Category: Article
• ISSN: 0008-8846
• DOI: 10.1016/0008-8846(90)90043-w

✦ Synopsis

We congratulate the authors for nice work. They have shown a very interesting phenomenon in this paper, e.g. that deterioration (cracks) occurs during warming (thawing) and not during freezing.

This work has shown the morphologies of ice formation in large pores of cement paste at low temperatures from -150"C to -44"C. The micrographs depicting cracks are worth noting. It is, however, questionable that the morphology of ice formed at the rapid freezing to -180"C is similar to that which occurs in nature. It is known that the filling of large pores is different with different rates of freezing, namely when the temperature is suddenly dropped to -18012, the water in the gel phase freezes; subsequently the large pores become less filled. Whereas in the case of slow rate of freezing, the ice formation starts in the large pores. The water from smaller pores and even from gel pores migrates to the large pores due to the osmotic pressure. This may also influence the crack development in the cement paste. Besides, the heat liberated during freezing may also develop cracks. The heat liberated depends upon the rate of freezing.