Effect of hydroxypropyl methylcellulose on cement based materials

Effect of hydroxypropyl methylcellulose on cement based materials

1. Dispersion resistance

Anti dispersion is an important technical index to measure the quality of anti dispersion agent. HPMC is a kind of water-soluble polymer compound, also known as water-soluble resin or water-soluble polymer. It increases the viscosity of mixed water by increasing the consistency of mixture. It is a kind of hydrophilic polymer material, which can be dissolved in water to form a solution or dispersion. With the increase of HPMC content, the dispersion resistance of fresh cement mortar is better and better.

2. Concrete strength characteristics:

In the pilot project based on the application of HPMC underwater non dispersible concrete admixture, the design strength grade is C25. In the basic test, the cement dosage is 400kg and the compound silica fume mixture is 25kg/ The results show that the optimum content of mhpmc is 0.6% of cement, water cement ratio is 0.42, sand ratio is 40%, naphthalene superplasticizer output is 8% of cement, the average strength of concrete specimen is 28 days, the average strength of air is 42.6mpa, the average strength of underwater concrete with drop height of 60mm is 36.4mpa, and the forming strength ratio of formed concrete to air is 84.8%.

The experimental results show that: 1

(1) The addition of HPMC has a significant retardation effect on the mortar mixture. With the increase of HPMC content, the setting time of mortar increases. Under the same amount of HPMC, the molding time is longer. This function is very good for pumping underwater concrete.

(2) The fresh cement mortar mixed with hydroxypropyl methylcellulose has good cohesion and almost no color penetration.

(3) HPMC content and water consumption of mortar decreased first and then increased,

(4) The addition of superplasticizer improves the water demand of mortar, but it must be controlled correctly. Otherwise, the underwater dispersion resistance of fresh cement mortar may be reduced.

(5) The structure of HPMC mixed with HPMC is similar to that of HPMC. There is not much difference in the structure and density of cement paste placed in water and air. The 28d underwater forming specimen is slightly brittle. The main reason is that the addition of HPMC greatly reduces the loss and dispersion of cement during pouring, and reduces the compactness of cement stone. Ensure the underwater non dispersion effect in the project, because the amount of HPMC is minimized.

(6) Mixing HPMC underwater non dispersible concrete admixture and controlling the dosage are beneficial to the strength. The pilot project shows that the strength ratio of cement concrete is 84.8%, and the effect is obvious.