Dry shake aggregate floor hardeners are commonly applied to the surface of freshly placed concrete to improve wear resistance and occasionally to color a concrete surface. They decrease typical plain concrete negative properties like dusting and liquid absorption by improving the abrasion resistance and reducing surface permeability.
What are Dry Shake Hardeners?
Dry shakes are factory blended materials containing a cementitious binder, aggregates, admixtures and other additives. They may incorporate inorganic pigments or be naturally colored. The ability of a dry shake material to provide a hard, abrasion-resistant wearing surface depends on the presence of enough free water at the fresh concrete surface to enable the finish to be fully wetted and worked monolithically into the base concrete. The hydration process of the cementitious material into dry shake consumes free water from concrete mix and eliminates higher water-to-cement (w/c) ration of the near-surface concrete.
Benefits of Dry Shakes Hardeners
All commercial, manufacturing, and warehouse floors require a high quality work surface providing long-term durability, high abrasion resistance, dustproofing, low permeability and safety. In most industrial applications dry shake floors have the best price/performance ratio when compared with alternative concrete treatments or finishes. The main characteristics and benefits provided by dry shake hardeners include: installation time saving, enhanced durability, improved traction safety, aesthetic options, and overall economy.
While dry shake is applied onto fresh concrete, the surface is finished in one step during the concreting works. The floor surface is finished together with a construction concrete slab within 8 to 12 hours after placement of concrete. The surface is walkable after 24 hours and light operation is possible after three to seven days.
Dry shake floors are economical flooring solutions showing very efficient price/ performance ratio. The initial material cost and reduced labor cost during construction are relatively low. Reduced maintenance cost and the long life cycle minimize plant shutdowns and lost operations costs. In total, dry shake hardeners deliver both short-term and long term cost savings.
The durability of a floor is the primary requirement of a quality industrial floor. In regard of dry shake hardener, the durability is determined by the abrasion resistance of the topping and its adhesion to the base concrete. The dry shake floor surface provides a tough durable cap to the concrete which is not damaged by other construction operations. The application and proper finishing of dry shake reduces the concrete porosity decreasing oil, grease and other chemical substances absorption and potential damage.
High durability concrete floors minimize maintenance and repair, operations shutdown, and overall facility costs. Due to the long life and economy of installation, concrete floors with dry shake topping deliver high performance qualifications in Life Cycle Assessment (LCA) calculations.
The typical color of a dry shake floor is grey. For many years the aesthetics was considered a minority importance in industrial buildings, however aesthetics are gaining more importance due to their contribution to worker morale and corporate image. Dry shake hardeners not only deliver improved performance properties but can also contribute to the facility aesthetic design.
Dry shake hardeners are available with inorganic pigments for a variety of colors, even very light color shades such as yellow and white. Light reflective floors can brighten a workspace, improve work efficiency, and reduce lighting costs. The aesthetic value of dry shake hardeners has increased trends of use in public buildings and private homes.
The floor surface must contribute to a safe working environment in all types of operations, including wet, dry, and contaminant rich conditions. Slips and falls most frequently result from contaminants on the floor. A slip resistant floor depends upon the combination of providing a safe traction surface and an efficient maintenance routine.
Dry shake applications are safe and environment friendly to install. The content of volatile organic substances (VOC) is low contributing to fire and health safety. Additionally, floor maintenance of dry shake surfaces is easy, ordinary cleaning machines can be used. Sealers can also provide additional surface dustproofing protection making the environment hygienic and user friendly.
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Sika aims for success and takes pride in continuously achieving outstanding results and outperforming its markets. The company pursues the vision and targets with persistency and a long-term view. Sika believes in individual responsibilities. Functions and projects will be clearly assigned. The overall profit and loss responsibility lies with the General Manager. Sika has transparent benchmarks for financial performance following a defined strategy. Performance evaluation is based on market share, sales growth, profitability and capital efficiency.
Application Methods and Rates
Dry shake hardeners are applied as a dry compound onto the fresh concrete surface, the application is achieved by hand or mechanical application. Hand application is normally completed after the initial set and floating of the concrete. Mechanical application is commonly performed immediately after concrete placement, before the initial set of the concrete has taken place.
The final thickness of a dry shake finish should be 2 to 3 mm. The necessary application rate to achieve this depends on bulk density of the dry shake. The end use of the floor and the dry shake type define the typical application rate. Variable rates can be specified in a building to suit the different uses in different places.
Mechanical application is ideal for application rates of 5 kg/m2 and are not advisable for lower application rates due to the potential of the aggregate sinking into the plastic concrete slab surface. The typical application rate by hand is 4 to 5 kg/m2. Higher rate is possible (up to 7 kg/m2), but it is highly dependent on the site conditions, concrete formula, and the water content in the concrete. Higher application rates by hand are best performed using two stages.
Typical Application Rates per End Use
| END USE | APPLICATION RATE |
|---|---|
| Foot Traffic | 3 kg/m2 or low water cement ratio concrete |
| Light Forklift Traffic / Abrasion | 3 kg/m2 |
| Medium Forklift Traffic / Abrasion | 5 kg/m2 |
| Heavy Forklift Traffic / Abrasion | 5 – 7 kg/m2 |
NOTES: Pigmented hardeners are recommended to be applied at a minimum rate of 6 kg/m2. Concrete may require water adjustments for higher application rates.
Basic Design Considerations
Some ambient conditions and concrete mixes with low w/c ratio can make medium and high application rates extremely difficult to install and should be carefully considered during planning stages. Concrete mix w/c ratio should be at least 0.50 to secure the adequate amount of water for hydration of the hardener. Concrete mixes for interior floors should not include air entrainment and should have a measured entrapped air content of more than 3%.
Dry shake hardeners are generally not recommended for ultraflat floors. The application method and finishing process makes it difficult to achieve the critical floor tolerances required with ultraflat floors.
Conrad Nabholz
Sika Services AG