Page "Cement" Paragraph 13

Setting time and " early strength " are important characteristics of cements.

Hydraulic limes, " natural " cements, and " artificial " cements all rely upon their belite content for strength development.

Belite develops strength slowly.

Because they were burned at temperatures below 1250 ° C, they contained no alite, which is responsible for early strength in modern cements.

The first cement to consistently contain alite was made by Joseph Aspdin's son William in the early 1840s.

This was what we call today " modern " Portland cement.

Because of the air of mystery with which William Aspdin surrounded his product, others ( e. g., Vicat and I. C.

Johnson ) have claimed precedence in this invention, but recent analysis of both his concrete and raw cement have shown that William Aspdin's product made at Northfleet, Kent was a true alite-based cement.

However, Aspdin's methods were " rule-of-thumb ": Vicat is responsible for establishing the chemical basis of these cements, and Johnson established the importance of sintering the mix in the kiln.