Post Date:20,Oct,2025
What are the material requirements for gypsum self-leveling mortar?
1. Active admixtures: Self-leveling materials can use fly ash, slag powder, and other active admixtures to improve the particle size distribution and enhance the properties of the hardened material. Slag powder undergoes hydration in an alkaline environment, increasing the material's structural density and later strength.
2. Early-strength cementitious material: To ensure construction time, self-leveling materials have certain requirements for early strength (primarily 24-hour flexural and compressive strength). Sulphoaluminate cement is used as an early-strength cementitious material. Sulphoaluminate cement hydrates rapidly and offers high early strength, meeting these requirements.
3. Alkaline activator: Gypsum composite cementitious materials achieve their highest absolute dry strength under moderately alkaline conditions. Quicklime and 32.5 cement can be used to adjust the pH to create an alkaline environment for hydration.
4. Setting accelerator: Setting time is a key performance indicator of self-leveling materials. Setting time that is too short or too long is detrimental to construction. The coagulant stimulates the activity of gypsum, speeding up the supersaturated crystallization of dihydrate gypsum, shortening the setting time, and keeping the setting and hardening time of the self-leveling material within a reasonable range.
5. Water Reducer: To improve the density and strength of the self-leveling material, the water-to-cement ratio must be reduced. While maintaining good fluidity, the addition of a water reducer is necessary. The water-reducing mechanism of a naphthalene-based water reducer is that the sulfonic acid groups in the naphthalene-based water reducer molecules hydrogen-bond with water molecules, forming a stable water film on the surface of the cementitious material. This facilitates the sliding of the material particles, reducing the amount of mixing water required and improving the structure of the hardened material.
6. Water Retention Agent: Self-leveling materials are applied on a relatively thin base layer, making them easily absorbed by the base layer. This can lead to inadequate hydration, surface cracks, and reduced strength. In this test, methylcellulose (MC) was selected as a water-retaining agent. MC exhibits excellent wettability, water retention, and film-forming properties, preventing water exudation and ensuring full hydration of the self-leveling material.
7. Redispersible polymer powder (hereinafter referred to as polymer powder): Polymer powder can increase the elastic modulus of the self-leveling material, improving its crack resistance, bond strength, and water resistance.
8. Defoaming agent: Defoaming agents can improve the surface properties of the self-leveling material, reduce bubbles during molding, and contribute to the strength of the material.
Post time: Oct-20-2025