Hydroxypropyl methylcellulose (HPMC for short) has excellent thickening properties and can be used as an excellent concrete anti-dispersion agent. In recent years, with the continuous development of external wall insulation technology and the continuous progress of cellulose production technology . As well as the excellent characteristics of HPMC itself, HPMC has been widely used in the construction industry.
1: Anti-dispersion test
Anti-dispersion is an important technical index to measure the quality of anti-dispersion agent. HPMC is a water-soluble polymer compound, also known as water-soluble resin or water-soluble polymer. HPMC increases the consistency of the mixture by increasing the viscosity of the mixing water. It is a hydrophilic polymer material. It can be dissolved in water to form a solution or dispersion.
Experiments show that when the amount of naphthalene-based high-efficiency superplasticizer increases, the addition of superplasticizer will reduce the dispersion resistance of freshly mixed cement mortar. This is because naphthalene-based superplasticizers are surfactants.
When the water-reducing agent is added to the mortar, the water-reducing agent is oriented on the surface of the cement particles so that the surface of the cement particles has the same charge. This electric repulsion breaks up the flocculation structure formed by cement particles. Release the water trapped in the structure. Part of the cement will be lost. At the same time, it is found that with the increase of HPMC content, the dispersion resistance of fresh cement mortar is getting better and better.
2: The strength characteristics of concrete
(1) The addition of hydroxypropyl methylcellulose has an obvious retarding effect on the mortar mixture. With the increase of HPMC content. The setting time of mortar is extended successively. In the case of the same HPMC dosage. Mortars formed underwater will take longer to set than those formed in air. This feature is beneficial for underwater concrete pumping.
(2) The freshly mixed cement mortar mixed with hydroxypropyl methylcellulose has good cohesive properties and almost no bleeding.
(3) The content of hydroxypropyl methylcellulose and the water demand of mortar decreased first and then increased obviously.
(4) The addition of water reducing agent improves the problem of increased water demand for mortar. But its dosage must be controlled reasonably. Otherwise, the underwater dispersion resistance of the freshly mixed cement mortar will sometimes be reduced.
(5) There is little difference in the structure between the cement paste specimen mixed with HPMC and the blank specimen. There is little difference in the structure and compactness of the cement paste specimens cast in water and in air. The specimen formed under water is slightly crisp.
The main reason is the addition of HPMC. Although it greatly reduces the loss and dispersion of cement when pouring in water. But at the same time, it also reduces the compactness of cement stone. In the project, under the condition of ensuring the effect of non-dispersion under water, the dosage of HPMC should be reduced as much as possible.
(6) Add hydroxypropyl methylcellulose underwater non-dispersible concrete admixture. Controlling the dosage is good for strength. The pilot project shows. The strength ratio of concrete formed in water to that formed in air is 84.8%. The effect is more significant.
Landcel manufactures HPMC for concrete addition. It can effectively improve the commonality of ease. Concrete sagging, water retention, etc.