The Durability of Concretes Made with Blends of High-Alumina Cement and Ground Granulated Blast Furnace Slag


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Title: The Durability of Concretes Made with Blends of High-Alumina Cement and Ground Granulated Blast Furnace Slag

Author(s): G. J. Osborne and B. Singh

Publication: Special Publication

Volume: 153


Appears on pages(s): 885-910

Keywords: acid resistance; adiabatic conditions; blast furnace slag; blended cements; concretes; durability; high-alumina cements; seawater; sulfates; Materials Research

Date: 6/1/1995

A rapid-hardening cement was made by blending mixtures of high- alumina cement (HAC) and ground granulated blast furnace slag (GGBS). The addition of slag alters the course of hydration reactions in HAC. A chemical compound 2CaO.Al 2O 3.SiO 2.8H 2O (gehlenite hydrate or stratlingite), only seen in plain HAC in small amounts, readily forms and becomes the main stable hydrate in the blended cement concretes in the temperature range of 5 to 38 C, replacing the metastable hydrates which lead to loss of strength in HAC through the conversion reaction. The properties of mortars and concretes made with this cement were assessed in a series of durability studies carried out by the Building Research Establishment. Mortars made with the blend have shown excellent sulfate resistance. Concrete specimens were compared with those from HAC concretes of similar proportions, following exposure for two years in aggressive sulfate, marine, and soft acid water environments. The findings, at this relatively early stage, are very encouraging. Longer term tests will be carried out at five and 10 years. Concretes made with the blend have shown a greater tolerance of high water-cement ratio mixtures in forming stable products with reduced temperature rises and enhanced durability in terms of their excellent sulfate, seawater, and soft acid water resistance.