Effect of Cellulose Content on Concrete Mortar

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Anti-dispersion is an important technical index to measure the quality of anti-dispersant. HP cellulose is a water-soluble polymer compound, also known as water-soluble resin or water-soluble polymer. It increases the consistency of the mixture by increasing the viscosity of the mixing water. It is a hydrophilic polymer material and can be dissolved in water to form a solution or dispersion. Liquid.
When the amount of naphthalene superplasticizer increases, the incorporation of water reducer will reduce the anti-dispersion of fresh cement mortar. This is because the naphthalene series superplasticizer is a surfactant, when the water reducing agent is added to the mortar, the water reducing agent in the cement particle surface for directional arrangement to make the cement particle surface with the sameThe electric charge, this electric repulsion force causes the flocculation structure formed by the cement particles to be dismantled, and the water wrapped in the structure is released, which will cause the loss of a part of the cement. At the same time, it is found that with the increase of HP cellulose content, the dispersion resistance of fresh cement mortar is getting better and better.
strength characteristics of concrete:
HP cellulose underwater non-dispersible concrete admixture was applied in a pilot foundation project, and the design strength grade was C25. According to the basic test, the cement dosage is 400kg, the composite silica fume is 25kg/m3, the optimal dosage of HP cellulose is 0.6 of the cement dosage, the water cement ratio is 0.42, the sand ratio is 40%, and the naphthalene system is high.The output of effective water reducing agent is 8% of the cement dosage, the average 28d strength of concrete specimens in air is 42.6MPa, the average 28d strength of underwater pouring concrete with a falling height of 60mm in water is 36.4MPa, and the strength ratio of molded concrete in water to molded in air is 84.8, with remarkable effect.
Experiments show that:
(1) The addition of HP cellulose has obvious retarding effect on the mortar mixture. With the increase of HP cellulose content, the setting time of mortar is prolonged one after another. This feature pairs of underwater concrete pumpsSend favorable.
(2) the new cement mortar mixed with hydroxypropyl methyl cellulose has good cohesive properties, almost no bleeding phenomenon.
(3)HP cellulose content and mortar water demand decreased first and then increased significantly.
(4) The incorporation of water reducing agent improves the problem of increasing water demand of mortar, but the dosage must be reasonably controlled, otherwise the underwater anti-dispersion of fresh cement mortar will be reduced.
(5) There is little difference in the structure between the cement paste specimen mixed with HP cellulose and the blank specimen, and there is little difference in the structure and compactness of the cement paste specimen poured in water and in the air. The specimen formed under water for 28d is slightly loose. The main reason is the addition of HP cellulose, although greatly reducing the water when pouring cementThe degree of loss and dispersion, but also to reduce the density of cement stone. In the project, under the condition of ensuring the non-dispersion effect under water, the dosage of HP cellulose should be reduced as much as possible.
(6) Adding HP cellulose underwater non-dispersible concrete admixture, controlling the dosage is beneficial to the strength, and the pilot project shows that the strength ratio of water forming concrete and air forming is 84.8%, and the effect is more significant.

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