Nowadays, with the commercialization of concrete and the dispersion and wetting effect of water agents, it is difficult to meet the market requirements for early hydration speed and high performance of cement. According to the survey, the accelerated degree of high strengthening, the increase in hydration products, and the rapid increase in solid content have become important directions for the development of today's concrete technology. In order to overcome this problem, the plastic retaining agent was born to solve the workability and other problems in its production process. If the concrete plastic retaining agent is used properly, it can reduce the water slump value, and at the same time it has high strength and rapid hardening. , high density and durability, etc.
Causes and solutions to the problems of slump loss and slump instability
1. Causes
(1) Adaptability of admixtures and cement It will cause rapid loss of concrete slump.
(2) The amount of small ingredients is not enough, and the retardation and plastic retention effects are not ideal.
(3) The weather is hot, and some admixtures fail at high temperatures; water evaporates quickly; bubbles overflow causing a rapid loss of fresh mix slump.
(4) The initial slump is too small and the unit water consumption is too little.
(5) Poor coordination between the construction site and the mixing station caused the tanker to be pressed and jammed for too long, resulting in excessive slump loss.
(6) The concrete mixing and weighing system has large measurement errors and is unstable.
(7) Changes in moisture content of coarse and fine aggregates.
(8) Cement is stored in a mixed warehouse and used for mixing.
2. Solutions
(1) Adjust the admixture formula to make it compatible with cement. Before construction, be sure to conduct admixture and cement adaptability tests.
(2) Adjust the concrete mix ratio, increase or decrease the sand rate and water consumption, and adjust the initial slump of concrete to more than 200mm.
(3) Add an appropriate amount of fly ash to replace part of the cement.
(4) Increase the amount of admixture appropriately and adjust the retarding component of the admixture (especially when the temperature is much higher than normal).
(5) Prevent water from evaporating too quickly and bubbles from overflowing too quickly.
(6) Choose slag cement or pozzolanic cement.
(7) Improve the water retention and cooling devices of transport vehicles.
(8) The accuracy of measuring equipment should meet relevant regulations and have a valid certificate issued by the legal metrology department. Self-inspection should be strengthened to ensure accurate measurement.
(9) Strengthen the detection of aggregate moisture content, and adjust the mix ratio in time when it changes.
(10) Incoming cement should be stored and used separately according to manufacturer, variety and label.
How to use concrete plastic retaining agent
When the dosage of pumping agent is 1.5-3.0%, 5-10 kg of plastic retaining agent can be added directly to the original formula; to meet the requirements Under experimental requirements, part of the water-reducing agent mother liquor can be appropriately replaced to achieve better cost performance.
The mechanism of action of high-efficiency plastic retainers. As for the reason for slump loss, it can be summarized that when cement meets water, it begins to dissolve and hydrate to produce gel, and form a network-like agglomeration structure, and the wrapped part Moisture. As time goes by, the gel continues to increase, which significantly improves the cohesion of the mixture and gradually decreases the slump, that is, slump loss occurs. High-strength, fluid-type concrete generally uses high-efficiency water-reducing agents. After the water-reducing agent is added to the concrete, a large amount of anionic water-reducing agent is adsorbed on the surface of the cement, which increases the surface charge.
Plastic retainers should be used in the project By reducing the dosage to a certain extent, increasing the use and compounding with an appropriate amount of highly efficient water-reducing, plastic-preserving and other components, the area is reduced, and the cost is reduced. Therefore, significant technical mixing, granulation and other processes can be achieved. </p
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