Frequently Asked Questions – Construction Chemicals

FAQ

Will gypsum retarder affect the strength?

Generally speaking, gypsum retarders will affect the strength of gypsum to some extent. For example, organic acid retarders such as tartaric acid have a greater impact on gypsum strength, while modified amino acid retarders have a smaller impact on strength.

What types of gypsum can Sunbo’s retarder be used for?

Sunbo has different types of gypsum retarders that can meet the application requirements of extending the setting time of α-hemihydrate gypsum, β-hemihydrate gypsum, etc., which are calcined from natural gypsum, industrial by-product desulfurization gypsum, industrial by-product phosphogypsum, etc.

What are the differences in the effects of suspension stabilizers and cellulose ethers on gypsum-based self-leveling?

Suspension stabilizers have better solubility and are less affected by pH and temperature changes. Cellulose ethers can easily cause incomplete dissolution in some gypsum-based self-leveling materials, forming wet cracks on the surface of the slurry after pouring. After the surface dries, microcracks or small holes will appear.

In addition, cellulose ether has better water retention performance and the viscosity of gypsum self-leveling slurry increases more significantly.

Gypsum-based self-leveling tends to crack along the walls and corners. How to improve it?

In building construction, protruding corners are called external corners, such as the four protruding corners of a square column, and recessed corners are called internal corners, such as the angles between the walls of a room. Since external corners are stress concentration points, they are prone to stress cracking when floor materials are applied. In structural design, external corners are usually reinforced with additional radial reinforcement to distribute stress and prevent concrete external corner cracking. For gypsum self-leveling, relatively simple methods can be used, for example:

1) Before pouring, use a small piece of elastic material (such as adhesive strips) to stick on the outside corner, preferably in an arc shape;

2) During the pouring process, place a small piece of mesh close to the outside corner (to prevent it from being washed away by the slurry, it is recommended to use a metal mesh);

3) After pouring is completed and the material has hardened, cut a small cross-cut close to the exterior corner. Or cut a cross-cut parallel to the exterior corner line. The depth of the cut must be greater than the thickness of the self-leveling layer.

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