KH Series Retarder for Precast Concrete Components / Aggregate Exposure Agent / Stone Exposure Agent

Applying the aggregate-exposed coating to the formwork surface creates a uniform film. The -OH and -COOH organic compounds in the aggregate-exposed coating possess strong adsorption properties. When the poured concrete comes into contact with it, the film rapidly absorbs water, dissolves, and penetrates the concrete to a certain depth, quickly bonding with the cement particles. This causes a temporary delay in the setting of the concrete surface for a certain period of time. If the formwork is not removed and moisture is not allowed to evaporate, this “delayed setting” effect can be significantly prolonged; After the concrete member has reached sufficient strength for form removal, rinsing the surface with a high-pressure water jet exposes the aggregate, creating a rough surface that effectively enhances the tensile and shear strength of the concrete joint. This product does not affect the overall setting or performance of the concrete; however, the depth of the retarding effect depends on various factors, including the thickness of the coating, the time of form removal, ambient temperature, cement properties, and the concrete mix design. This product is water-soluble but must not be diluted with water to avoid compromising the exposed aggregate effect. It does not stain concrete products and can be thoroughly rinsed off with water.

Product Characteristics

Appearance: Colorless, viscous liquid

Uses: Used for exposed aggregate treatment on concrete; suitable for building structures, joints and ends of concrete components, or continuous construction applications. It creates a rough, exposed aggregate concrete surface without the need for chiseling or scraping.

Composition: Organic compounds containing -OH and -COOH groups

pH: 7–10

Coverage: 6–8 square meters/kg; Retardation depth: 3–6 mm

Storage: Must be stored in a cool place; avoid exposure to direct sunlight or rain

Application Method

1. There is no need to clean concrete residue or dirt from the formwork surface;

2. After thoroughly mixing the product, apply it directly to the formwork surface;

3. Pour concrete once the film has air-dried; remove the formwork after the concrete member has reached the required strength—generally no later than 1 day at temperatures between 20–30°C, and no later than 2 days at temperatures around 10°C. Rinse the exposed aggregate surface with a high-pressure water jet; If the exposed aggregate surface needs to be left for an extended period before rinsing, do not remove the formwork prematurely; remove it only when rinsing is required. Alternatively, apply an additional 1–2 coats of the exposed aggregate product to ensure sufficient penetration depth. It is recommended to conduct a preliminary test based on on-site materials and environmental conditions to observe its retarding effect.

4. When creating an exposed aggregate effect on a flat concrete surface, dilute the product with 0.2–0.5 times its volume of water to increase its flowability. Apply the diluted emulsion evenly over the concrete surface where the exposed aggregate effect is desired, and rinse with a high-pressure water jet within 2 hours after the concrete has reached its required strength.