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What are the material requirements for gypsum-based self-leveling mortar

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What are the material requirements for gypsum-based self-leveling mortar

Β-type hemihydrate gypsum prepared by calcining first-grade dihydrate gypsum with a purity of more than 90% or α-type hemihydrate gypsum prepared by autoclave method or hydrothermal synthesis method.
Active admixture: Self-leveling materials can use fly ash, slag powder, etc. as active admixtures. The purpose is to improve the particle gradation of the material and improve the performance of the material hardened body. The slag powder undergoes hydration reaction in an alkaline environment, which can improve the compactness and later strength of the material structure.

Early-strength cementitious materials: In order to ensure the construction time, self-leveling materials have certain requirements for early strength (mainly 24h flexural and compressive strength). Sulphoaluminate cement is used as an early-strength cementing material. Sulphoaluminate cement has fast hydration speed and high early strength, which can meet the requirements of early strength of the material.

Alkaline activator: gypsum composite cementitious material has the highest absolute dry strength under medium to alkaline conditions. Quicklime and 32.5 cement can be used to adjust the pH value to provide an alkaline environment for the hydration of the cementitious material.

Coagulant: Setting time is an important performance index of self-leveling materials. Too short or too long time is not conducive to construction. The coagulant stimulates the activity of gypsum, accelerates the supersaturated crystallization speed of dihydrate gypsum, shortens the setting time, and keeps the setting and hardening time of the self-leveling material in a reasonable range.
Water-reducing agent: In order to improve the compactness and strength of self-leveling materials, it is necessary to reduce the water-binder ratio. It is necessary to add water-reducing agents under the condition of maintaining good fluidity of self-leveling materials.
The naphthalene-based water-reducing agent is used. The water-reducing mechanism is that the sulfonate radicals and water molecules in the naphthalene-based water-reducing agent are associated with hydrogen bonds to form a stable water film on the surface of the gelling material, making the material particles easy to produce Sliding, thereby reducing the amount of mixing water required, and improving the structure of the hardened material.

Water retaining agent: Self-leveling materials are constructed on the ground base, and the construction thickness is relatively thin, and the water is easily absorbed by the ground base, resulting in insufficient hydration of the material, cracks on the surface, and reduced strength. In this experiment, HPMC Celulose Ether is used as a water-retaining agent. HPMC has good wettability, water retention and film-forming properties, so that the self-leveling material does not bleed and fully hydrates.

Redispersible latex powder / polymer powder hereinafter referred to as latex powder): Latex powder can increase the elastic modulus of self-leveling materials, improve crack resistance, bonding strength and water resistance.

Defoamer: Defoamer can improve the apparent performance of self-leveling materials, reduce bubbles during material molding, and have a certain effect on improving the strength of the material.

We PTMA can supply all additives to gysum based mortar, for more information, feel free to contact us.

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