WHAT ARE THE ADVANTAGES OF PPC (PORTLAND POZZOLANA CEMENT)

PPC在新混凝土中的优点

Portland pozzolana cement (PPC) has following advantages when concrete is in its fresh state.

1. Workability

波特兰Pozzolana水泥具有球形水泥颗粒，它们具有更高的细度值。由于球形形状混凝土移动更自由，颗粒的细度允许更好地填充孔隙。这种类型的水泥还可以为混凝土提供更好的粘结性。与用普通水泥制成的混凝土相比，PPC水泥也降低了混凝土的坍落度损失率，特别是在炎热的天气条件下。

2. Bleeding

Bleeding is a type of segregation in which some of the water in the concrete mix tens to rise to the surface of fresh concrete. As a result of bleeding, the top surface becomes too wet and concrete will become porous, weak and non durable. PPC cement reduces bleeding by providing greater fines volume and lower water content for a given workability. This also helps to block bleed water channels.

3. Pumpability

PPC水泥有助于生产更多的粘性混凝土，不太容易发生偏析和出血。颗粒的球形形状用于通过降低骨料颗粒与混凝土和泵线之间的摩擦来提高可加工性和泵送性。

4.设置时间和可完成性

PPC cement slightly prolongs the setting time of concrete which helps the mason for good finishing of concrete or cement mortar. The cohesiveness of concrete mix helps for better finishing of concrete.

PPC在硬化混凝土中的优点

Portland pozzolana cement (PPC) has following advantages when concrete is in its hardened state.

1. Compressive Strength & Rate of Strength Gain

用PPC制造的混凝土强度增益的强度和速率将在28天时相当于普通混凝土。即使在普通水泥的水合速率下降后，PPC的硅酸盐形成也仍在速度下降。这导致后期的强度增益增加。这种更高的强度增益率将随着时间的推移继续，并导致更高的年龄强度。

2. Modulus of Elasticity

The modulus of elasticity of PPC concrete is somewhat lower at early ages and little higher at later ages than ordinary concrete.

3. Bond of Concrete to Steel

The bond or adhesion of concrete to steel is dependent on the contact area of steel with concrete, the depth of reinforcement & density of concrete. PPC being finer in nature usually increases paste volume & reduce bleeding thus the contact will be increased, resulting into improved bond with steel.

4. Heat of Hydration

The hydration of PPC is a slower process than hydration of ordinary cement, resulting into slower heat generation and lower internal stresses in concrete. Thus PPC becomes ideal cement for mass concreting like dams, retaining walls, large foundation etc.

5. Reduced Shrinkage

PPC in concrete helps to reduce drying shrinkage & plastic shrinkage. Drying shrinkage is reduced because of lower internal concrete stresses & slower heat generation. Plastic shrinkage is also reduced considerably because concrete bleeds less at a given slump or workability by using PPC.

6.渗透率

If concrete has interconnecting void spaces, then the concrete becomes permeable. In PPC concrete, the lime [Ca (OH)2] liberated during initial hydration is consumed by reactive silica & forms an insoluble cementitious compound instead of leaching on the concrete surface. This helps in reducing void spaces & also blocks capillary channels & subsequently reduces permeability of concrete.