Application of Amino Acid Gypsum Retarder in Gypsum Mortar

I. Core Mechanism of Action
Amino acid compounds contain active groups such as amino (-NH₂) groups, which can undergo complexation reactions with Ca²⁺ in the gypsum hydration system to form stable chelates that adsorb onto the surface of dihydrate gypsum crystals. This hinders crystal growth and aggregation, thereby slowing down the hydration process of gypsum, extending the workable time of the mortar, and has no negative impact on the later strength development of the gypsum mortar.
II. Applicable Gypsum Mortar Types and Application Scenarios
1. Green Interior Wall Plastering Gypsum Mortar
This retarder is chlorine-free and formaldehyde-free, meeting green building material standards. It is suitable for interior wall plastering projects in residential buildings, hospitals, schools, and other places with stringent environmental protection requirements. It can extend the initial setting time of morta, solving the problem of rapid setting and inability to smooth the mortar in high-temperature summer environments, ensuring the smoothness of the plaster layer, and reducing the probability of hollow areas and cracking.
2. Gypsum-based Self-leveling Mortar
It precisely controls the setting time and fluidity of the mortar, maintaining high fluidity for 30-60 minutes. This ensures thorough leveling in low-lying areas, preventing segregation and bleeding. Suitable for large-area floor leveling projects in office buildings, shopping malls, etc., resulting in a highly flat surface and meeting compressive strength standards.
3. Mechanized Sprayed Gypsum Mortar
Excellent compatibility with spraying equipment. After addition, the mortar exhibits good thixotropy, preventing premature hardening and blockage in the delivery pipeline. Sufficient time is allowed for finishing and adjustment after spraying. Suitable for mechanized interior wall construction in high-rise buildings, significantly improving construction efficiency and reducing labor costs.
4. Special Gypsum Mortar (Insulation and Repair)
Gypsum-based Insulation Mortar: When combined with lightweight aggregates such as vitrified microspheres and expanded perlite, it slows down the mortar's setting speed, preventing aggregate settling and segregation due to rapid mortar hardening, ensuring uniformity and effective insulation.
Gypsum Repair Mortar: Used for fine repair of wall cracks and holes, extending the workable time, facilitating compaction and filling by construction workers, and ensuring a tight bond with the base gypsum mortar after curing, without shrinkage cracks.
5. Precast Gypsum Component Production: Suitable for the production of precast components such as gypsum panels, gypsum blocks, and decorative gypsum moldings. It can extend the residence time of the mortar in the mold to 1-2 hours, ensuring the mortar fully fills the mold edges and corners, reducing defects such as air bubbles and chipped edges on the component surface, and improving the appearance quality and dimensional accuracy of the precast components.
III. Key Application Points
1. Dosage Control: The dosage needs to be adjusted according to the type of gypsum (building gypsum, high-strength gypsum) and the construction temperature. The specific dosage should be adjusted according to the type of gypsum, gypsum variety, temperature, and construction requirements. Excessive dosage can easily lead to a slight decrease in mortar strength.
2. Compatibility Requirements: It exhibits good compatibility with commonly used water-retaining agents (HPMC), redispersible latex powder, defoamers, and other admixtures in gypsum mortar, showing no flocculation or stratification when used in combination.
3. Construction Precautions: A dry-mixing method followed by wet mixing is required: First, mix the amino acid retarder evenly with the gypsum powder, aggregates, and other dry materials, then add water and stir to ensure even dispersion of the retarder and avoid excessive localized
retarding.