Slag Cement Facts What is Slag Cement?

 
How Does Slag Cement Improve Concrete?
Slag cement is a hydraulic binder that, like portland cement, reacts with water to form 
cementitious material (calcium-silicate hydrate or CSH). Like pozzolans, slag cement 
consumes by-product calcium hydroxide from the hydration of portland cement to form 
additional CSH. The resulting cement paste is stronger and denser, thus improving the 
concrete. 

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Slag Cement Association: Slag Cement Facts 
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How Does Slag Cement Affect Concrete Strength and Elastic Modulus?
 
Slag cement provides higher levels of compressive strength in concrete when compared 
with ordinary portland cement (OPC) concrete of equal cementitious materials content.
Slag cement proportions of 40 to 50 percent normally optimize strength. Concretes made 
with slag cement will generally exhibit higher flexural strength for a given level of 
compressive strength. Modulus of elasticity follows the same relationship as OPC 
concrete, when based on compressive strength. Thus, with the higher compressive 
strengths achievable with slag cement, structural stiffness can be enhanced, and load 
deflections minimized. 
How Does Slag Cement Affect Permeability and Corrosion Resistance? 
Low concrete permeability is essential for long-term durability, especially with regard to 
corrosion resistance of reinforcing steel. The additional CSH formed and denser cement 
paste in slag cement concrete reduce pore size and lower concrete permeability, often by 
several orders of magnitude. Low permeability reduces the ingress of harmful substances 
(such as chlorides and sulfates) and the availability of water to catalyze harmful chemical 
reactions within concrete. It also dramatically lowers the rate of chloride ion diffusion 
and carbonation, thus significantly enhancing the corrosion protection offered by the 
concrete to the reinforcing steel.