Mechanism of delayed hydration of cement analyzed by HPMC manufacturer

Shandong chuangyao Biotechnology Co., Ltd., a manufacturer of hydroxypropyl methylcellulose, has tested that the effect of different hydroxypropyl methylcellulose on the hydration delay of Portland cement is not the same, and the delay effect of the same hydroxypropyl methyl cellulose on different hydration products is also different, which shows that the hydration products of Portland cement have selectivity for cellulose ether adsorption, and hydroxypropyl methyl cellulose has the selectivity The adsorption of cement hydration products is also selective. Hydroxypropyl methyl cellulose HPMC has stronger retardation than MC, and hydroxypropyl methyl cellulose has the ability to delay the formation of calcium hydroxide than C.S.H gel and Ettringite. This has a corresponding relationship with the adsorption capacity of hydroxypropyl methyl cellulose and hydration products of cement. It is further confirmed that adsorption is probably the real cause of delayed hydration of hydroxypropyl methyl cellulose and fiber. The stronger the adsorption capacity of vitamin ether and cement hydration products is, the more obvious the formation of delayed hydration products is.

1. The hypothesis that ion motion is hindered

HPMC manufacturers assume that HPMC increases the viscosity of pore solution, hinders the rate of ion movement, thus delaying cement hydration. However, in this experiment, HPMC with lower viscosity has stronger ability to delay cement hydration. Therefore, this hypothesis is not true. In fact, the time of ion movement or migration is very short, which is obviously incomparable with the delay time of cement hydration.

2. Adsorption

Adsorption may be the real reason for the delay of cement hydration by HPMC. Many organic additives will be adsorbed on cement particles and hydration products to prevent the dissolution of cement particles and the crystallization of hydration products, thus delaying the hydration and setting of cement. Hydroxypropyl methylcellulose manufacturers found that hydroxypropyl methyl cellulose readily adsorbed on the surface of hydrated products such as calcium hydroxide, C.S.H gel and calcium aluminate hydrate, but it was not easily adsorbed by ettringite and unhydrated phase. The lower the content of hydroxyethyl in HEC or hydroxypropyl in HPMC, the stronger the adsorption capacity. For the hydration products, the adsorption capacity of calcium hydroxide is stronger than that of c.s.h. Further analysis also shows that the adsorption capacity of hydration products and cellulose ether is corresponding to the delay of cement hydration: the stronger the adsorption, the more obvious the delay. However, ettringite has weak adsorption on HPMC, but its formation is obviously delayed. The study of hydroxypropyl methylcellulose also shows that HPMC has strong adsorption on tricalcium silicate and its hydration products, thus obviously delaying the hydration of silicate phase and low adsorption of ettringite, but the formation of ettringite is obviously delayed, because the delay of ettringite formation is affected by the balance of Ca2 + in solution, which is cellulose ether delayed silicate water The continuation of transformation.

3. Alkali degradation

In alkaline conditions, polysaccharides are easy to degrade to form hydroxycarboxylic acids which will delay cement hydration. Therefore, the reason why HPMC delays cement hydration may be that it forms hydroxycarboxylic acids in alkaline cement slurry. However, studies by hydroxypropylmethylcellulose manufacturers have found that HPMC is very stable under alkaline conditions, with only a small amount of degradation The delay of cement hydration has little effect.

Hydroxypropyl methylcellulose (HPMC) is the best water retaining agent and thickener for mortar, and it is an indispensable additive. The quality of HPMC and the amount of HPMC will directly affect the quality of mortar. And hydroxypropyl methyl cellulose is a renewable resource, and belongs to green environmental protection additives. Hydroxypropyl methyl cellulose is widely used in many fields. For more information about HPMC, please pay close attention to HPMC manufacturer, Shandong chuangyao Biotechnology Co., Ltd www.cyhuagong.com 。