What effect does retarder have on the initial setting time of concrete?

As we all know: Coagulant is a new type of coagulation material. It has a saturation point. It will increase beyond that saturation point but not too obviously. You can make a sample to find the optimal dosage. It is a way to reduce the cement or cement content. Additives that increase the hydration speed and heat of gypsum and extend the setting time of gypsum. Refer to the regulations in the national standard “Classification, Naming and Definition of Concrete Admixtures” (GB8075-2005). The purpose of adding retarder to commercial concrete is to prolong the hydration and hardening time of cement, so that fresh concrete can maintain its plasticity for a longer period of time, thereby adjusting the setting time of fresh concrete.

Retarder is suitable for continuous pouring of concrete, large volume concrete, ready-mixed concrete and pumped concrete under high temperature conditions.

When the gelling material hydrates, it will release a lot of heat. When the temperature is high in summer, the temperature of some products can reach 80 degrees. When the temperature of the product is too high, the product will no longer be 5.1.8 phase, but the very unstable 9.1.5 phase, and the strength is not high. When the temperature is too high, magnesite products produced will have problems such as halogenation, deformation, and low strength. The current solution is to add a retarder to disperse the heat of hydration and control the setting time.

For concrete pouring construction, the initial setting time generally needs to be longer to ensure that the concrete has sufficient transportation, pouring and vibration time, because these tasks must be completed before the initial setting. After the initial setting of concrete, the faster the final setting, that is, the shorter the time interval between initial setting and final setting, the more beneficial it is to increase the construction speed, because the faster the final setting, the faster the strength increases, and the faster follow-up work can be carried out.

Function

The purpose of adding concrete retarder to commercial concrete is to extend the hydration and hardening time of cement so that fresh concrete can maintain plasticity for a longer period of time. Thereby adjusting the setting time of fresh concrete.

Testing indicators

Flow rate increase: 8 Initial setting time difference: +60~+120 Compressive strength ratio at 7 days: 120 Compressive strength ratio at 28 days: 120 Softening coefficient: 0.55

The most technically challenging thing is to retard the concrete (2 to 3 hours), and at the same time final set immediately after the initial set, the strength increases rapidly, it can be quickly demoulded, speed up the turnover of formwork, and improve construction or production. efficiency. This is suitable for some thin-walled structures or products. Some companies claim that with the help of nanotechnology additives, Portland cement can do this, but at least it has not been applied in China. China uses sulphoaluminate cement and can achieve this effect by using only a retardant, but it actually relies on the rapid strength development of sulphoaluminate cement.

Retarder

The retarder series products are a new type of concrete admixture independently developed and produced by our company. There are a large number of hydroxyl and carboxyl groups in the molecular structure of this product, which can form a stable complex with free Ca 2+ in the alkaline medium of cement hydration products, delaying the crystallization of CH, and can also be adsorbed on cement particles. surface, delaying the hydration reaction. This product has no rusting effect on steel bars and can be widely used in concrete pumping construction of buildings, roads, bridges, hydraulic engineering and underground projects. If this product becomes slightly hardened during transportation and storage, it is normal and will not affect product performance.

Product performance

1. This product is used to adjust the setting time of concrete. The dosage and usage method are the same as those of conventional retardant materials. It can be adjusted according to the floor material and temperature in each region. , adjust the dosage reasonably.

2. This product can reduce the slump loss of concrete over time and adjust the workability of concrete.

3. This product can adjust the adaptability of cement and water-reducing agent.

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