Why Portland cement is not suitable for mass engineering?

Because of the quick hydration reaction of portland cement, the content of tricalcium silicate and dicalcium silicate is high, and the hydration heat is large, which is beneficial to winter construction. However, due to the large hydration heat, when building mass concrete projects (generally, the length, width and height are all above 1m), it is easy to accumulate large heat in concrete members, resulting in the stress difference between internal and external temperature differences, thus causing the destruction of concrete. Therefore, it is not suitable for mass concrete engineering.

Portland cement has compact structure and good frost resistance. It is suitable for repeated freezing and thawing projects in cold areas and projects with high freezing requirements, such as dam overflow surface and concrete pavement projects.

Extended data

The main mineral components of portland cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium ferric aluminate. Tricalcium silicate determines the strength of Portland cement around; It takes four weeks for dicalcium silicate to exert its strength, and it takes about one year for tricalcium silicate to reach its strength around.

The strength of tricalcium aluminate is fast, but low, which plays a certain role in the strength of portland cement in 1 ~ 3 days or a little longer; The strength of tetracalcium ferrite also develops rapidly, but the strength is low, which makes little contribution to the strength of portland cement.

The national standard stipulates that the initial setting time of portland cement should not be earlier than 45min minutes, otherwise it is unqualified; The final setting time is not later than 390min, otherwise it is unqualified. The volume stability of portland cement must pass the inspection, otherwise it is unqualified. Portland cement is divided into three strength grades according to the compressive strength of 3d and 28d, namely 42.5, 52.5 and 62.5, and each grade has two types (denoted by R): ordinary type and early strength type.

Baidu encyclopedia-Portland cement

Baidu Encyclopedia-Ordinary Portland Cement