As we all know: As the third generation of water reducing agent, water reducing agent has more obvious advantages, such as high water reducing rate, small dosage, strong plasticity retention, good durability and environmental friendliness, etc., and is favored by everyone. However, summer has arrived and the weather is gradually getting hotter. Water-reducing agents without added fungicides are prone to varying degrees of turbidity. Although it has little effect on the loss of water-reducing agents over time and the fluidity of the slurry, it does not affect the setting time of concrete. It will cause a certain impact, and there will be a serious odor, which will affect the construction. This article will simulate four different storage methods to explore the impact on the performance of high-performance water-reducing agents and analyze the reasons for deterioration.
1. Test method
1.1 Storage environment
Put the prepared high-performance water-reducing agent and the water-reducing agent added with 1kg/t fungicide. Transparent PET plastic bottles were stored for a certain period of time under refrigerator low temperature (5°C) sealing, indoor sealing, outdoor sealing exposure, and outdoor open exposure conditions for sampling tests. The performance evolution rules of the water-reducing agent were simulated respectively under indoor storage in winter, indoor storage in summer, sealed outdoor storage in summer, and open outdoor storage in summer.
1.2 Fluidity and setting time of slurry
According to GB/T8077-2012 “Test Method for Homogeneity of Concrete Admixtures”, the same dosage (fold solidification) was tested under different storage conditions. The fluidity and time loss of the water-reducing agent. At the same time, the setting time of the pure slurry was tested with reference to GB/T1346-2011 “Cement standard consistency water consumption, setting time, stability inspection method”.
1.3 Appearance
Take out the water-reducing agent stored in different environments within a certain period of time, and observe the appearance (color, turbidity) of the water-reducing agent in different storage environments through transparent PET plastic bottles evolution.
1.4 Molecular weight and distribution of water-reducing agent
Gel permeation chromatography (GPC), according to the different time of different molecular solutions flowing through the gel chromatography column, the organic matter in the water-reducing agent is obtained molecular weight and distribution.
2. Results and Analysis
2.1 The impact of storage environment on the appearance of water-reducing agents
Under different storage environments, the appearance of water-reducing agents varies. In the case of adding bactericide, the appearance of the water-reducing agent stored in a sealed refrigerator or indoor sealed environment for 90 days is equivalent to that of the newly prepared sample, and has not changed significantly. However, water-reducing agents without added bactericides all appear turbid. Especially under indoor sealing conditions, the water-reducing agents have a serious odor and deteriorate seriously.
Under the condition of outdoor sealing and exposure to the sun, the water-reducing agent without fungicide and fungicide B appears turbid, especially the water-reducing agent with fungicide B is more turbid. Some scholars believe that the fungicide becomes turbid under high temperature and light exposure. , prone to decrease, weakening its bactericidal effect. In the case of outdoor exposure to the sun, fungicides and water-reducing agents will cause bacteria clusters and darker colors, which may be related to the falling of debris. There was precipitate and transparency at the bottom of the water-reducing agent without the addition of fungicides, but no odor occurred during outdoor storage.
In short, the deterioration of water-reducing agent is particularly serious in summer. Fungicide should be added and stored indoors, and must not be exposed to the sun. When there is no fungicide, try to store it outdoors or in the open, and prevent debris from falling in. Do not store it indoors in a sealed manner, which will cause turbidity and aggravated odor.
2.2 The impact of storage environment on the performance of water-reducing agent
Different environments have different effects on the fluidity of water-reducing agent slurry.
Adding fungicides to the water-reducing agent has little effect on the fluidity and time loss of the water-reducing agent, and the water-reducing agent is sealed in the refrigerator, indoors, sealed and exposed 4 After being stored in this environment for 30 days, the fluidity and time loss of the clean slurry are equivalent to those of new water-reducing admixtures. The performance of the water-reducing agent slurry after 90 days of storage in different environments is equivalent to that of the newly prepared sample and the performance of the water-reducing agent stored for 30 days. The fluidity and slump retention of the water-reducing agent over time do not change with changes in storage time, storage environment, and type of fungicide. .
Without the addition of fungicides, the setting time of the water-reducing agent is shortened only in the indoor sealed environment. The initial setting and final setting are shortened by 30% and 20% respectively, while the refrigerator seal, seal exposure, Under open exposure conditions, the retardation time is basically the same. After adding a fungicide, its retarding time is equivalent to that of a water-reducing agent without adding a fungicide, and different storage has little effect on its setting time.
2.3 Analysis of the deterioration mechanism of water-reducing agents under different storage environments
The impact of storage conditions on water-reducing agents and retarders. The amounts of water-reducing agents and retarders without bactericides change with time. .
Only the retardant component of the water-reducing agent stored indoors without adding a bactericide decreased, and it became more obvious as the storage time increased, from 17.5% at the time of sample preparation to 5.7%. And the peak value of the retarder is significantly weakened, and it is decomposed into substances with smaller molecular weights. However, there was no decomposition of the retarder in other environments or when fungicides were added, and there was no change in molecular weight or distribution.
3. Conclusion
3.1 Without the addition of fungicides, only the water-reducing agent stored at room temperature indoors will appear severely turbid and smelly, and the condensation time will be significantly shortened. The water-reducing agent stored under other storage conditions will The water-reducing agent only appears slightly turbid, and the storage environment has little impact on the slurry fluidity and time loss of the water-reducing agent.
3.2 Under different storage times and environments, the water-reducing, slump-preserving, and retarding effects of the clean slurry added with the fungicide and water-reducing agent are equivalent to those of the newly prepared samples, and the two fungicides are anticorrosive under indoor conditions. The effects are all good. However, outdoor exposure will reduce its bactericidal effect, especiallyWhen the mouth is exposed to the sun, debris can easily fall into it and bacteria clusters may appear.
3.3 Through GPC, it was found that the decomposition of the sugar retarder component in the water-reducing agent by microorganisms is the essence of the deterioration phenomena such as turbidity, odor and shortened setting time of the water-reducing agent.
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