Question

1. Answer the following questions related to “Type HE” cement
   • What property of this cement sets it apart from type GU?
   • What are the benefits of using this type of cement?
   • How does this type of cement differ from Type GU cement with respect to the relative amounts of C2S, C3S and C3A?

Answer 1

Type GU or Type I Portland Cement : A general-purpose cement suitable for all uses for which the special properties of other types of portland cements are not required. It is generally assumed unless another type is specified. It is commonly used for general construction, especially when making precast, and precast-prestressed concrete that is not to be in contact with soils or ground water. The typical compound compositions of this type are: 55% (C₃S), 19% (C₂S), 10% (C₃A), 7% (C₄AF), 2.8% MgO, 2.9% (SO₃), 1.0% ignition loss, and 1.0% free CaO.
A limitation on the composition is that the (C₃A) shall not exceed 15%.

Type HE or Type III Portland Cement : High-early-strength cement for use where high early strengths are required. Its typical compound composition is: 57% (C₃S), 19% (C₂S), 10% (C₃A), 7% (C₄AF), 3.0% MgO, 3.1% (SO₃), 0.9% ignition loss, and 1.3% free CaO. This cement is similar to type I, but ground finer. Some manufacturers make a separate clinker with higher C₃S and/or C₃A content, but this is increasingly rare, and the general purpose clinker is usually used, ground to a specific surface area typically 50–80% higher. The gypsum level may also be increased a small amount. This gives the concrete using this type of cement a three-day compressive strength equal to the seven-day compressive strength of types I and II. Its seven-day compressive strength is almost equal to 28-day compressive strengths of types I and II.