Cement hydration product - calcium silicate hydrate brief introduction
Key words
Calcium silicate hydrate, C-S-H gel, amorphous calcium aluminate
Calcium silicate hydrate is formed by the hydration of tricalcium silicate and dicalcium silicate, or a water-containing compound synthesized from silicon-containing materials and calcium oxide-containing materials. It is in a gel state at room temperature and is a microcrystal with short-range order and long-range disorder. It has fibrous, reticulated, granular and other morphology, about 1 um in length and 0.2 um in width. It is the main compound of Portland cement.
Calcium silicate hydrate accounts for about 60% to 70% of the hydration products of Portland cement. In the process of cement hydration, the calcium silicate hydrate generated by hydration fills the voids, increases the density, and cross-links the hydration products of cement. , to form a network structure and promote the development of cement strength. Synthetic calcium silicate hydrate is added to cement concrete, and its nucleation and adsorption accelerate the cement hydration process, so it plays an important role in the field of cement reinforcement.
During the hydration process of Portland cement, hydration products such as C-S-H, Ca(OH)2 and ettringite are also formed in the cement hydration reaction. Calcium silicate hydrate is an important substance that plays the main strength in concrete. After the silica fume contacts the mixing water, it first forms a silicon-rich gel and absorbs water; the gel aggregates between the unhydrated cement particles and gradually wraps the cement particles; Ca(OH)2 and the surface of the silica-rich gel The reaction produces C-S-H gels, and these C-S-H gels derived from silica fume and Ca(OH)2 are mostly formed in the pores of C-S-H gels of cement hydration, which greatly improves the structural density.
In addition to the production of calcium silicate hydrate in the process of cement hydration; calcium silicate hydrate is prepared and produced through a series of chemical processes as an admixture for cement and concrete. It can effectively promote the hydration of cement, shorten the setting time of cement, and improve the early strength of cement.
Amorphous calcium aluminate has extremely strong hydration activity. Adding amorphous calcium aluminate into Portland cement can significantly promote the cement hydration reaction and promote the production of hydrated calcium silicate C-S-H gel, thereby improving the Early strength of cement and concrete structures, shortening of setting time and a series of improved cement and concrete properties.
