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Gypsum is used to prevent immediate stiffen and reduce heat loss of cement. If gypsum has already been added into cement,do we still need to undergo curing process after that?

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When gypsum is added to the concrete mix it changes some of its characteristics.Curing is the process in which the concrete is protected from loss of moisture and kept within a reasonable temperature range.

Even if you were using gypsum alone, you would still need to add water: much less than concrete, but still...

for the curing process, it depends on several factors(temperature, humidity, materials)

But to answer your question, yes you should still carry out curing process. This is something that you just can't escape.

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This a bit late but I will add to the answers already given, with some additional technical and historical perspective.

Portland cement contains four Bogues compounds - C3A, C2S, C3S and C4AF. Of these, one is not hydraulic - C3A. C3A (tricalcium aluminate) was introduced to Portland cement during the 1920's as it was found to reduce the heat required for production, thereby reducing the cost of manufacture. It was not introduced for engineering purposes, as some may suggest. Unfortunately, as it is not hydraulic, C3A will dissolve with time if immersed in water, and it is susceptible to sulphate attack.

During hydration, however, C3A produces about 3 or 4 times more heat than other Bogues compounds - leading potentially to flash setting and cracking problems in the hardened concrete. Accordingly, gypsum, or CaSO4 (calcium sulphate), is inter-ground with the clinker to control this flash setting.

The addition of CaSO4 (particularly the sulphate portion), however, is again detrimental. Accordingly, Portland cement standards limit the maximum SO4 content. Thus we see that the addition of C3A necessitates the addition of gypsum and both are detrimental to long term performance, in my view.

Some will argue that the addition of C3A will have benefit with respect to binding chlorides and resisting steel corrosion. I have not found this to be the case in my projects and research. But this view is subject to some controversy. I prefer to eliminate C3A and gypsum when possible but this will increase the cost of Portland cement.

Now we return to your core question: adding C3A, which will also require the addition of gypsum, will make the concrete more sensitive during construction and will require greater attention to curing, not less.

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