What is concrete accelerator？
The alkali-free concrete accelerator is a new generation of high-performance, chlorine-free, and alkali-free environmentally friendly products developed by using new materials and new processes. It has good compatibility with various types of cement and can be used with large imported wet spray machines. Reduce dust in construction, high efficiency, and environmental protection, and can significantly improve economic benefits.
Accelerating admixtures Advantages and Features
(1) Good homogeneity: This product is a colorless or light green liquid with good homogeneity and no delamination.
(2) Low dosage: The recommended dosage is 3% to 8% of the cement mass. The cement concrete sets and hardens quickly, and the initial and final setting interval is short.
(3) Good durability of concrete: because alkali-free concrete accelerator admixture does not contain a large number of alkaline substances like alkaline accelerators, it greatly reduces the damage to concrete caused by the introduction of alkaline substances, and reduces the risk of material reaction and improve the durability of concrete.
(4) Health and environmental protection: alkali-free cement accelerator does not contain alkaline cations and is neutral or weakly acidic, which will not cause corrosive damage to the skin and health of construction workers. The alkali-free accelerator reduces the dust concentration and the amount of rebound during the spraying process, which greatly improves the construction environment.
(5) Small rebound rate: Experience shows that the rebound rate of alkali-free accelerating admixtures for spraying is less than 15%. The use of alkali-free accelerating admixtures can reduce the waste of materials and the labor and equipment costs required for cleaning the rebound waste, which is economical. The benefits are obvious.
(6) The difference in strength: the alkali-free accelerator admixtures have high early strength and small late strength loss. The use of alkali-free accelerators to improve the support strength can reduce the amount of cement and reduce the cracking and spalling. The input cost of the secondary repair of slag and roadway deformation reduces the production cost.
(7) Excellent adaptability: suitable for various cement types, within the range of 3%~8%
(8) It has no adverse effect on the durability of concrete. Since the alkali-free liquid accelerator is a non-chloride accelerator, the destructive effect on concrete caused by the introduction of alkaline substances, such as alkali-aggregate reaction, is greatly reduced; The content of chloride is limited, and corrosion of steel bars is avoided.
(9) There is no dust during the spraying process, and the amount of rebound is reduced, thereby protecting the health of the construction workers and reducing the waste of materials.
(10) Hardened concrete has good compactness and impermeability and can be formulated with high-strength shotcrete.
Applications of accelerator in concrete
Alkali-free liquid concrete curing accelerator is suitable for shotcrete construction and leak plugging, ground Cement concrete rapid construction, and concrete emergency rescue, repair, and reinforcement works.
How to use the concrete accelerator and matters needing attention
(1) Dosage: The dosage of an alkali-free liquid concrete accelerator depends on the temperature of the concrete, the environment, and the base, as well as the activity and setting time of the cement used, early strength, etc. Based on the above factors, the recommended dosage of alkali-free liquid accelerator is 3%-8% by weight of cement.
(2) Dry spraying process: The concrete is dry mixed in advance, the alkali-free liquid concrete accelerator is added to the water through the metering pump, and the water is added to the concrete mixture through the nozzle.
(3) Wet spraying process: The concrete is mixed with water in advance, and the alkali-free liquid concrete accelerator enters the compressed air pipeline through the metering pump and is sprayed from the nozzle together with the concrete.
(4) In these cases, full attention should be paid to the accuracy of the admixture dosage. The best water-cement ratio of concrete is ≤0.45. In the case of a lower water-cement ratio, better results can be obtained even if the amount of alkali-free liquid concrete accelerator is small. Water-cement ratio>0.5 will prolong the setting time and reduce the early strength of the concrete.
(5) The alkali-free liquid concrete accelerator has good adaptability to the consistency of concrete and is suitable for shotcrete with large slump (>200mm).
(6) If the dosage used is greater than the recommended dosage, it will cause too slow coagulation and early strength drop, which will seriously affect its structure and adhesion.
(7) Before using the alkali-free liquid concrete accelerator, the metering pump, including the pumping liquid (filter) and the accelerator pipeline, must be rinsed with water. During use, the entire pump system must be cleaned daily to prevent clogging.
Packaging and storage of concrete accelerator
The alkali-free cement accelerator is packed in plastic barrels in tons and can also be packaged according to user needs.
Plastic buckets should be handled with care so as not to break.
It must be stored in the original airtight container, in a cool, dry, and ventilated place, avoid moisture, and the temperature is five ℃ to 35 ℃.
Concrete accelerators cannot be stored in metal containers. Stir the product well before use to avoid precipitation.
Shelf life of concrete accelerator
The storage period of the alkali-free liquid accelerator is six months if stored in the recommended original airtight container.
FAQs of concrete accelerator
Q: What are the main ingredients of alkali-free concrete accelerators? How do they work?
A: Alkali-free concrete accelerators usually contain the following main ingredients: Aluminate compounds: such as aluminum chloride and aluminum sulfate, these ingredients accelerate early strength development by promoting rapid hydration of the C₃A (tri-calcium aluminate) and C₄AF (tetra-calcium aluminoferrate) mineral phases in the cement. Nitrites or nitrates: as freeze-thaw resistant components, they not only help to accelerate the hardening process but also provide some protection against corrosion. Organic compounds: such as certain sugar derivatives or other surfactants, can improve the workability of fresh concrete and enhance early strength growth. These ingredients work synergistically to greatly reduce the initial and final setting time of concrete without affecting later strength development, thereby accelerating construction progress and permitting efficient concrete placement operations at lower temperatures.
Q: What are the advantages of using Alkali-Free Concrete Accelerator?
A: There are several significant advantages of using NACs: Enhanced durability: Concrete structures are more stable and have a longer service life as the risk of alkali - aggregate reactions is avoided. Adaptation to low temperatures: Especially suitable for cold regions or winter construction projects, it can effectively accelerate concrete hardening at lower temperatures without compromising quality. Improved early strength: the ability to reach the required strength level in a short period of time allows for faster formwork removal and reduced waiting times. Optimized construction scheduling: By shortening the curing cycle, it improves the efficiency of the construction site and reduces overhead costs. Environmentally friendly: compared with traditional alkali containing accelerators, alkali-free products have less impact on the surrounding environment, which is in line with the concept of modern green construction.
Q: Under what circumstances should I choose to use alkali-free concrete accelerator?
A: Alkali-free concrete accelerator is especially suitable for the following situations: Projects with stringent requirements for durability: e.g. infrastructure construction such as bridges, tunnels, dams, etc., where there is a need to ensure that the concrete structure will remain in good condition for decades to come. Areas with a potential risk of alkali-aggregate reactions: If the aggregates used contain components that are prone to triggering alkali-aggregate reactions, alkali-free accelerators should be prioritized to avoid long-term damage. Construction in low temperatures: Especially during winter in cold northern regions, where conventional concrete may struggle to harden properly when temperatures fall below 5°C, non-alkali accelerators can help overcome this challenge. Rapid turnaround needs: For situations where a specific strength needs to be reached quickly in order to continue with subsequent processes, such as in precast plants, NACs can significantly improve productivity. Additionally, any project looking to adopt more environmentally friendly construction methods may also want to consider the use of NACs.
Q: What should I be aware of when using NACs?
A: The following points should be kept in mind when using NACs: Follow the manufacturer's guidelines: Strictly follow the recommended mixing amounts on the product specification. Overuse may cause negative effects such as excessively rapid setting or compromised final strength. Control temperature conditions: Although alkali-free accelerators perform well at low temperatures, extreme cold weather may still affect their effectiveness; use insulation where necessary to ensure optimum results. Test for compatibility: Prior to large-scale application, it is recommended that small-scale tests be conducted to confirm that the accelerator does not react adversely with the cement and other admixtures used. Focus on workability: Observe changes in the workability of fresh concrete to ensure that the mixture remains easy to pump, pave and vibrate. Maintain Safe Handling: Always wear appropriate personal protective equipment (PPE), including gloves, goggles, etc., when handling chemicals to prevent skin contact or inhalation of dust. Comply with environmental regulations: Ensure that surplus materials and packaging materials are disposed of in a manner that complies with local environmental protection regulations and avoids polluting the environment. Proper selection and use of alkali-free concrete accelerators will not only improve construction efficiency, but also provide better protection and support for the building.
