Hydroxypropyl Methyl Cellulose Function to Construction Admixture
Anti-dispersibility is an important measure of the quality of anti-dispersant. HPMC is a water-soluble polymer compound, also known as water-soluble resin or water-soluble polymer, by increasing the viscosity of the mixed water to increase the consistency of the mixture, is a hydrophilic polymer material, dissolved in water to form a solution Or dispersion. It can be seen that when the dosage of naphthalene superplasticizer is increased, the incorporation of water reducing agent will reduce the anti-dispersibility of fresh cement mortar. This is because the naphthalene superplasticizer is a surfactant. When the water reducing agent is added to the mortar, the water reducing agent is arranged on the surface of the cement particles so that the surface of the cement particles has the same charge. The electric repulsion causes the cement particles to form Of the flocculation structure is broken up, the structure of the water wrapped in the release, will cause a part of the loss of cement. At the same time, it was found that the anti-dispersibility of fresh cement mortar was getting better with the increase of HPMC content.
Strength characteristics of concrete
The HPMC underwater non-dispersible concrete admixture is used in the bridge foundation engineering of the Dandu-line (Dandong-Tonghua) expressway. The design strength grade is C25. The optimum dosage of HPMC is 0.6% of cement, 0.4% of water and cement is 40%, the rate of water is 40%, and the amount of naphthalene superplasticizer is 40% The average strength of the concrete in the air was 42.6 MPa, and the average strength of the underwater pouring concrete was 36.4 MPa underwater drop height of 60 mm. The concrete in the water was molded in the air and the air was molded The intensity ratio of 84.8%, the effect is significant.
(1) The addition of HPMC has obvious retardation effect on the mortar mixture. With the increase of the amount of HPMC, the setting time of mortar is prolonged, and the same amount of HPMC is more The molding time in air is longer. This feature is advantageous for pumping underwater concrete.
(2) mixed with hydroxypropyl methyl cellulose new cement mortar has a good adhesion performance, almost no bleeding phenomenon.
(3) HPMC content and mortar water demand showed a significant increase after the first increase.
(4) the incorporation of water reducing agent to improve the mortar water demand increases, but must be reasonable control of its content, or sometimes the new cement mortar underwater anti-dispersion is reduced.
(5) The cement cement paste injected with HPMC had little difference from the structure of the blank specimen, and the structure and density of the cement paste in the water pouring and the air were not big. Underwater molding 28 d of the specimen slightly crisp. The main reason is that the addition of HPMC, although greatly reduced when the water pouring cement loss and dispersion, but also make the cement stone to reduce the degree of density. In the project to ensure that the water does not disperse the effect of the case, due to minimize the amount of HPMC.
(6) The incorporation of HPMC underwater non-dispersible concrete admixture to control the good content of the strength of the benefit of the pilot project shows that the water forming concrete and air molding strength ratio of 84.8%, the effect is significant.