Effect of Cellulose Content on Concrete Mortar
Release Time:
2021-05-27
Source:
Anti-dispersion performance is a crucial technical indicator for evaluating the effectiveness of anti-dispersants. HP cellulose is a water-soluble polymer, also known as a water-soluble resin or water-soluble polymer, which increases the consistency of the mix by elevating the viscosity of the mixing water. It is a hydrophilic polymeric material that dissolves in water to form a solution or dispersion.
Liquid.
As the dosage of naphthalene-based high-efficiency water-reducing admixture increases, its incorporation reduces the anti-dispersion performance of fresh cement mortar. This is because naphthalene-based high-efficiency water-reducing admixtures are surfactants; when added to the mortar, they orient themselves on the surface of cement particles, imparting a uniform surface charge to these particles. This electrostatic repulsion disrupts the flocculent structure formed by cement particles, releasing the water entrapped within the structure and resulting in some cement loss. Furthermore, it was observed that as the dosage of HP cellulose increases, the resistance to dispersion of fresh cement mortar improves.
Strength characteristics of concrete:
HP cellulose underwater non-dispersible concrete admixture was applied in a pilot foundation project, with a design strength grade of C25. Based on preliminary tests, the cement dosage was 400 kg, with 25 kg/m³ of silica fume added as a composite admixture; the optimal dosage of HP cellulose was 0.6% of the cement content, the water-to-cement ratio was 0.42, and the sand ratio was 40%. Naphthalene-based high When the water-reducing admixture is used at 8% of the cement dosage, the 28-day average compressive strength of concrete specimens cured in air is 42.6 MPa, while that of underwater-cast concrete with a slump of 60 mm is 36.4 MPa. The strength ratio between underwater-cast concrete and air-cured concrete is 84.8%, demonstrating a remarkably significant performance.
The experiment shows:
(1) The addition of HP cellulose exerts a significant retarding effect on the mortar mix; as the dosage of HP cellulose increases, the setting time of the mortar progressively lengthens. Under the same dosage of HP cellulose, mortar molded underwater exhibits a longer setting time than that molded in air. This characteristic is particularly relevant for underwater concrete pumping. Sending is beneficial.
(2) Fresh cement mortar incorporating hydroxypropyl methylcellulose exhibits excellent cohesion and virtually no bleeding.
(3) The water demand of the mortar initially decreases and then increases markedly with increasing HP cellulose content.
(4) The addition of water-reducing admixtures alleviates the issue of increased water demand in mortar; however, the dosage must be carefully controlled, as excessive amounts can sometimes reduce the underwater anti-dispersion performance of fresh cement mortar.
(5) The cement paste specimens incorporating HP cellulose exhibit little structural difference compared with the control specimens, and there is also little difference in structure and compactness between specimens cast in water and those cast in air. However, the specimens cured underwater for 28 days appear slightly crumbly. The primary reason is that the addition of HP cellulose, although it significantly reduces the workability of the cement during casting in water, while also reducing the compactness of the cement paste. In engineering applications, the dosage of HP cellulose should be minimized as much as possible, provided that its anti-dispersion performance under water is maintained.
(6) Incorporating HP cellulose underwater non-dispersible concrete admixture, with proper dosage control, is beneficial to strength. Pilot projects have demonstrated that the strength ratio of concrete cured underwater to that cured in air is 84.8%, indicating a significant effect.
