Type III Portland Cement Auburn NY

Source: MASONRY CONSTRUCTION MAGAZINE
Publication date: July 1, 1996

If you use Type III portland cement, can you repoint brick masonry when the wall temperature is below freezing?

I do not recommend repointing when the surface temperature of the brick masonry is 40 F or less. Although Type III portland cement will perform slightly better than Type I in this situation, the advantage may not be enough to prevent freezing. Type III portland cement performs better because it hydrates faster. All portland cement contains both tricalcium silicate and dicalcium silicate. Tricalcium silicate hydrates faster than dicalcium silicate. Type III portland cement contains a greater concentration of tricalcium silicate; therefore, it generally hydrates faster. Furthermore, Type III cement is finer, and will also hydrate faster for this reason. The faster the portland cement hydrates, the less time the mortar must be kept warm. When mortar hydrates faster, it generates more heat. And the warmer the mortar, the faster it will hydrate. Most Type I portland cement sold today, however, contains fairly high concentrations of tricalcium silicate and is ground more finely than in the past. This brings it close to the requirements of Type III portland cement, so there may be little practical difference between Type III and Type I portland cements.There is a greater risk of mortar freezing when repointing than when installing new masonry during cold weather.

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