Types of Portland Cement – Concrete Moisture & Cracking

Types of Portland Cement – Concrete Moisture & Cracking

Different types of Portland cement can be used to regulate the amount of hydration heat released when concrete sets. Type 10 Normal Portland cement releases half of its heat in three days. Type 20 Moderate Portland cement takes more than three days to release half of its heat. Type 30 High Early Strength Portland cement releases half of its heat in less than three days. Type 40 Low Heat of Hydration Portland cement releases very little heat of hydration. Type 50 Sulphate Resistant Portland cement is used to protect concrete from degradation when it is placed in soils with high sulphate content. Concrete must remain moist when it is curing. Hydration continues only as long as there is moisture in the cement paste. Concrete that has dried out before it is completely cured shrinks and cracks, and can disintegrate into dust, especially at the surface. Control joints and reinforcing steel can be used to control cracking. If concrete loses it’s moisture or the relative humidity goes below 80 percent, or if it freezes, concrete stops curing and gaining strength.