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A reply to a discussion by S. Chandra and P. Flodin of “reactions between methanol and portland cement paste” (vol. 11, pp. 341–349, 1981)
CEMENT and CONCRETE RESEARCH. Vol. 12, p. 263, 1982. Printed in the USA. 0008-8846/82/020263-01503.00/0 Copyright (c) 1982 Pergamon Press, Ltd.
A REPLY TO A DISCUSSION BY S. CHANDRAAND P. FLODIN OF "REACTIONS BETWEEN METHANOLAND PORTLAND CEMENT PASTE" (Vol. I I , pp. 341-349, 1981) R.L. Day Dept. of Civil Engineering The Hatfield Polytechnic Hatfield, Herts, ALIO 9AB, U.K. I thank S. Chandra and P. Flodin for t h e i r discussion. comment on four of the points they raise. I.
I would l i k e to
There were no chlorides in the systems which I examined.
2. I believe that in the absence of water, methoxide formation is a dist i n c t p o s s i b i l i t y . Methanol replaces the water in cement paste; therefore, a f t e r replacement is complete, methoxides may form. There was no free water in the CH-methanol system which was tested. 3. I f the exothermic peak is due to r e c r y s t a l l i z a t i o n , i t is not clear what material is r e c r y s t a l l i z i n g and why this r e c r y s t a l l i z a t i o n does not occur in the untreated samples. 4. The peak shown in Figure 2 (page 345) is not an endothermic peak; i t is a rate of weight loss peak. DTA f a c i l i t i e s were not available to me. I called the exothermic peaks 'exothermic' because there was a sudden and large temperature rise in the TG furnace. The peak at 700°C in the untreated CH is undoubtedly due to carbonation of the CH due to storage before the start of testing. The methanol treated specimens show a much larger peak, yet there was no free carbon dioxide in the TG furnace, or in the methanol. I f the large peak is not methoxide, I can suggest no other p o s s i b i l i t i e s . In response to the f i n a l comment: methanol may be removed during drying, but i t is clear that some type of product is l e f t behind.
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A REPLY TO A DISCUSSION BY S. CHANDRAAND P. FLODIN OF "REACTIONS BETWEEN METHANOLAND PORTLAND CEMENT PASTE" (Vol. I I , pp. 341-349, 1981) R.L. Day Dept. of Civil Engineering The Hatfield Polytechnic Hatfield, Herts, ALIO 9AB, U.K. I thank S. Chandra and P. Flodin for t h e i r discussion. comment on four of the points they raise. I.
I would l i k e to
There were no chlorides in the systems which I examined.
2. I believe that in the absence of water, methoxide formation is a dist i n c t p o s s i b i l i t y . Methanol replaces the water in cement paste; therefore, a f t e r replacement is complete, methoxides may form. There was no free water in the CH-methanol system which was tested. 3. I f the exothermic peak is due to r e c r y s t a l l i z a t i o n , i t is not clear what material is r e c r y s t a l l i z i n g and why this r e c r y s t a l l i z a t i o n does not occur in the untreated samples. 4. The peak shown in Figure 2 (page 345) is not an endothermic peak; i t is a rate of weight loss peak. DTA f a c i l i t i e s were not available to me. I called the exothermic peaks 'exothermic' because there was a sudden and large temperature rise in the TG furnace. The peak at 700°C in the untreated CH is undoubtedly due to carbonation of the CH due to storage before the start of testing. The methanol treated specimens show a much larger peak, yet there was no free carbon dioxide in the TG furnace, or in the methanol. I f the large peak is not methoxide, I can suggest no other p o s s i b i l i t i e s . In response to the f i n a l comment: methanol may be removed during drying, but i t is clear that some type of product is l e f t behind.
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