Concrete and Gypsum Matrices

Portland cement, which is not a trade name, is available in several grades, to meet various physical and chemical requirements (see ASTM C-150, which covers eight types of Portland cement and Cement Standards of the World [7]). 

As the reaction proceeds, cement and water are gradually used up to produce an amorphous gel. To achieve good strength, it is necessary to cure the mass for several days by keeping the surface moist at 10 25°C. 

Concrete is extremely stiff and good in compression, but quite poor in tension. Steel rebar reinforcement is normally used to make a stronger structure, but because steel is subject to atmospheric corrosion, it has to be shielded with a relatively thick protective layer of concrete, which with time, is removed by weathering and erosion, eventually exposing the steel to attack. Carbon fiber has very good corrosion resistance and would not be affected by any alkalis in the cement. Hence it should be possible to utilize a carbon fiber composite such as carbon fiber/epoxy pultruded rods that would only require a relatively thin coating of concrete. Alternatively, carbon fiber can be incorporated directly into the concrete mix [9]. 

---