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Dry shake hardener is a mixture of cement, aggregate, and admixture which is applied as a dry compound onto the fresh concrete surface to protect floor surface from abrasion and impact effects, provide slip resistance; color; and surface texture, and improve durability.
It is applied on fresh concrete surface by hand or machinery and then power floated and troweled. Dry shake hardener reduces dusting and liquid penetration of concrete surface by declining its permeability.
Based on the type of aggregates used in the dry mixture, the dry-shake hardener is classified into three major groups namely: natural quartz aggregate, synthetic mineral aggregates, and metallic and metallic alloy aggregates. Single type of aggregate or combination of different types can be used to achieve certain concrete surface strength and color.
Types of Dry Shakes
Dry shakes are divided into three basic groups based on the type of aggregate used:
- Natural quartz aggregate
- Synthetic (non-metallic) mineral aggregates
- Metallic and metallic alloy aggregates
Dry shakes can be produced from one type or combination of these aggregates to achieve certain color and performance properties. Several factors such as service condition, durability, aesthetic and cost dictate the decision to choose a type of combination of aggregates for dry shake mixture.
Dry Shake Application Methods
Dry shake is applied onto fresh concrete by hand or machinery. Commonly, hand application is finalized after the initial set and floating of the concrete whereas machine application is conducted immediately after concrete placement, before the concrete sets.
Dry Shake Application Rates
The rate of application of dry shake onto the fresh concrete is based on bulk density of the dry shake and the end use of the floor. Variable rates can be specified in a building to suit the different uses in different places.
The method of application of dry shake also influences its rate of application. For example, minimum application rate of 5 kg/m2 is suitable for machine application in order to prevent the sinking of aggregate into the plastic concrete.
However, application rates of 4 to 5 kg/m2 is suitable for hand application. It is possible to increase the rate of application for hand application based on the site conditions, concrete formula, and the water content in the concrete. It is recommended to apply dry shake in two stages when higher application rates by hand is considered.
Dry Shake Thickness
The thickness of dry shake is at least 19mm.
Design and Construction Considerations
- Concrete mix w/c ratio should be at least 0.50 to secure the adequate amount of water for hydration of the hardener.
- It should be applied on well-designed and non-air entrained concrete mixes.
- If unusual conditions exist such as direct hot sun, high winds, low humidity or cold weather, care should be taken to protect the slab during dry shake placement
- Dry shake is not suitable for ultra-flat surfaces because it is impossible to achieve critical floor tolerances of ultra-flat floors. The unsuitability of dry shake this application is due to its application method and finishing process.
- Airplane hangars
- Electronic assembly plants
- Manufacturing plants
- Warehouses and distribution centers
- Shipping and receiving areas
- Maintenance facilities
- Commercial and industrial floors subject to deicing salts
- Where light-reflective flooring is desired
- Floors subject to heavy or frequent traffic
- Salt-storage facilities
- Multi-purpose sporting facilities
- Recreational facilities
- Prevents concrete damage due to abrasion, impact, punching, and scraping.
- Decline cost of maintenance during the life span of the floor.
- Enhances the appearance of floor surface.
- It adds texture and slip resistance
- It is able to increase the value of an industrial building and improve building sale-ability.
- Dry shake is an economical way to add color which is not fade with time.
- It can help the floor to reflect more light, reducing lighting and energy requirements. Extended floor life