Cement based materials such as concrete and mortar are the most widely used man-made materials in the world and have a significant impact on the world economy and environment. Although, Portland Cement (PC) is the most preferred cement type, other cement types are also widely used in different applications. Calcium alumina cement (CAC) is a special cement type, made of different raw materials from those used to manufacture PC and have many superior properties according to PC such as high sulfate resistance and abrasion resistance, high early strength, and resistance to high temperatures. Usage of CAC was very common in some countries especially in the manufacture of precast concrete units up to about 40 years ago. However, some hydration products of CAC are chemically unstable and show a change known as conversion with time and temperature. Increasing the temperature accelerates the conversion of metastable hydrates (CAH10, C2AH8) to stable hydrate (C3AH6). Conversion causes an increase in porosity and a reduction in strength. Therefore, the usage of CAC in structural applications is limited, however, it is highly used in refractory applications and in the production of repair materials. In addition, there has been some efforts by the manufacturers of CAC to re-introduce the structural use of this cement in last 10-15 years and a new CAC standard published and started to be used in Europe at 2006.
The addition of SCMs in the production of CAC containing products may change the hydration mechanism of a CAC-SCM system. Especially, some SCMs such as ground granulated blast furnace slags (GGBFS) may cause the formation of stratlingite (C2ASH8) and due to the high stability of this compound, CAC–SCMs blends, do not exhibit strength loss that would reported for pure CAC systems. In addition, using SCMs in the production of cement based materials are also beneficial for both economically and ecologically. Because, most of the used SCMs are industrial wastes and by-products. Thus, it is possible to reduce CO2 emissions in the production of cement or cement based materials.
In spite of its superior properties, usage of CAC is controversial especially in structural applications and need to be studied more in order to understand the conversion mechanism and the strength loss in order to use it safely. In the frame of this proposed cooperation we intend to search the effect of supplementary cementious materials such as fly ash, blast furnace slag and silica fume on the hydration mechanism of CAC mortars at different curing temperatures. For this purpose, CAC mortar specimens are going to be prepared using different SCMs and the effect of these SCMs to the strength and heat development of mortars will be investigated.