About antifreeze
Enlightenment: How much antifreeze is ethically required? In fact, it is so much, so be there early. If the solubility is exceeded, the most suitable antifreeze is an air-entraining agent.
Meet on Saturday: Your point of view is incorrect. Air bleed alone cannot lower the freezing point. It must be a combination of antifreeze component + air bleed to be practical.
Qidi: I have been selling antifreeze for more than ten years. Other ingredients are just a big deal. The real antifreeze is the air-entraining component. Antifreeze must have four major components: high water reduction, early strength, freezing point lowering, and ice crystal destruction. To lower the freezing point, salt is the best, but chloride ions will exceed the standard. Salt is the best way to prevent freezing of plain concrete.
Meet on Saturday: But the experiments done in each place are different. We specialize in experiments on different types of antifreeze components. After the trial assembly, the molds are directly installed and placed. When frozen in the freezer, the freezing time varies.
Regina Yim: I think antifreeze means lowering the freezing point. The small holes introduced by the air-entraining agent can buffer frost heave stress. There are two testing methods for frost resistance in durability testing, one is to measure strength and mass loss, and the other is to measure vibration.
jz: The air bleed is to block the capillary tubes, so that the moisture in the capillary tubes will not introduce new moisture and freeze and expand repeatedly.
Ren Nianqi: Add 6 kilograms of sodium nitrite to a square of concrete. You can’t add sodium nitrite to the admixture.
Meet on Saturday: @jz? is right, this is also the reason why it is impermeable.
Tusday: In the north, there is no insulation measures for the construction site, and the temperature is more than ten degrees below zero. How can we lower the freezing point to more than ten degrees below zero? It will freeze even if it drops to minus five degrees. It’s very difficult, and the real reduction is only two or three degrees. The main ingredients of my antifreeze are high-water-reducing and air-entraining, and I also mix in some other ingredients to make it look cool. For example, the solubility of the Naixin system is 36% (no matter how high it is, it is difficult to pump it up). The water reduction alone accounts for about 24 to 26%, leaving 12% of the antifreeze component. When the antifreeze minus 10 is added, 4% is added, and the antifreeze component is added. How much does it take to get up and will it work?
Meet on Saturday: One side of concrete admixture is 8-10 kilograms. You add 6 kilograms of sodium oxide to 8-10 kilograms. It definitely won’t dissolve. Besides, you added too much, right?
Time: In winter, we use hot water, so how can it freeze?
Qidi: There are very few stations with hot water, and there are also very few stations with temperatures exceeding five degrees Celsius.
Regina Yim: Use hot water and Portland cement, which has high heat of hydration and good frost resistance.
Time: hot water + good antifreeze, no matter how you use it in winter, it will be fine.
Enlightenment: Cold water and insulation are fine.
Meet on Saturday: No matter how good the antifreeze is, the insulation measures on the construction site are just antifreeze without insulation, and the construction of heating measures is a scam. Antifreeze is defined as an admixture that can harden concrete at negative temperatures and achieve expected performance and sufficient antifreeze strength under specified curing conditions. It is a substance that can prevent moisture in materials from freezing at low temperatures. Antifreeze also has specified maintenance conditions. Maintenance in winter is generally heat storage and insulation. Second, heating maintenance.
Many workers don’t understand why it’s still freezing even after adding antifreeze. There’s something wrong with the antifreeze. I said this is concrete antifreeze (it is used within specified limits), not car antifreeze. Every winter, I clear my line of responsibility with the construction site.
Qidi: I have done a lot of experiments and found that as long as the concrete is not frozen before final setting, the strength can be restored. I am afraid that it will be frozen before final setting. Generally speaking, you don’t have to worry about laying the foundation, etc. What you worry about is building a thin-walled structure. C15 and C20 add nothing to resist frost (less cement). The condensation time in winter must be controlled. The earlier the condensation is achieved, the better.
Fengjing: There is a problem in Dongshi that has never been clear. The critical strength of freezing. The old standard has a clear definition but it is incorrect. The new standard definition is definitely not wrong. , but ambiguous. The key to winter application is to take effective measures to reduce the critical freezing strength of concrete and reach the critical freezing strength as early as possible. Key antifreeze does not achieve antifreeze in the common sense sense. This is the root of all misunderstandings. Concrete antifreeze, this name may be appropriately changed.
Zhong Lei: What is the antifreeze principle of antifreeze? Any antifreeze product that meets standards has a clear “use temperature”. Everyone should know this, right?
Fengjing: Early understanding is to lower the freezing point. Antifreeze must have four major components: high water reduction, early strength, freezing point lowering, and ice crystal destruction. This is the currently recognized basis for antifreeze formulation. Its main purpose is to reduce the critical freezing strength of concrete and promote the concrete to reach the critical freezing strength as soon as possible.
Zhong Lei: To put it bluntly, antifreeze means that before the ambient temperature drops to the use temperature of the admixture, the concrete must reach the critical anti-freeze strength, so that the concrete is safe.
Fengjing: Theoretical research on antifreeze has been stagnant for a long time. Antifreeze and even winter construction are no longer a matter of concern to domestic front-line experts.. There is room for consideration regarding antifreeze, critical strength due to freezing, and even the acceptance methods and assessment basis for the strength of concrete applied in winter.
Zhong Lei: I participated in and compiled our local standards and specifications. Regarding the understanding of antifreeze and early strength agents, it is true that the winter temperature differences in various regions are large. Currently, domestically produced The use temperature of concrete antifreeze is mostly between -10 and -15. Be sure to pay attention to the usage temperature. In many cases, don’t deliberately make a fuss. It is normal not to add antifreeze during winter application. Cover it in time, keep it warm, extend the positive temperature maintenance time, etc. These can solve the anti-freeze problem very well.
Enlightenment: The embarrassment of compound antifreeze is that the first is that the selling price determines the quality of the materials used, and the second is that the dosage determines the adequacy of the antifreeze components. Thirdly, the inherent compounding is very contradictory. It strengthens early and collapses quickly. In order to solve this problem, it has to be compounded with a retarding component. When the pharmaceutical factory saw that there were 10 kilograms of sodium fluoride per ton in the formula of Nylon antifreeze, they asked the technician out of curiosity. The technician smiled and said, “It’s too far away to prevent collapse.” 10kg sodium gluconate.
Adjustment of the formula of admixture
How to use this 3.0 sand? What should we pay attention to when using admixtures?
Discussion
Shang Concrete Station: Qiu Jining: Pay attention to admixtures, one is water reduction The rationality of the rate is also due to the thickening component in the admixture. The ratio should be paid more attention to, because part of the sand is weathered, and the amount of glue should also be considered. If there are other sands that can be matched, that’s a different matter.
There is basically no sand below 0.63, which means it is broken-graded sand. If you have fine sand, then this problem is not a problem. , if not, one is to increase the sand rate, the other is to adjust the gradation of coarse aggregate, the last one is to adjust the total amount of cementitious materials, and finally focus on adjusting the formula of the admixture.
When adjusting the formula of admixtures, you should pay attention to the following factors: One is that the water reduction rate must adapt to the cement you use, and your sand must also be fully considered. The problem is that it cannot be too big or too small; the other is the consideration of air-entraining agents. I also know that air-entraining is not considered in Guangdong, but for this kind of sand, it is impossible not to consider air-entraining. Finally, you can consider it. Dextrin, because it has a certain thickening effect, but the dosage should not be large. If it is used in large quantities, it will easily cause problems. Before using it in large-scale production, it is best to do a trial mix to get a good idea.
Li Hongjun: Let’s slow down the setting, too much. The setting time will be too long. For every 1-2 hours of extension in the laboratory, large-scale production will be extended by 4-5 hours. Is the idea of doubling correct?
Shang Concrete Station: Qiu Jining: Yes, because its excess will seriously inhibit the hydration rate of cement, and will seriously affect other admixtures in concrete. These are the things to pay attention to when using dextrin. Generally, it is not added and only considered when there is no other way.
Li Hongjun: Are there any conflicts between these two points when the concrete wants to preserve the collapse time for a long time and at the same time wants to control the setting time? Can we have both?
Business Concrete Station: Qiu Jining: Yes, but you have to choose the right product and fully understand the characteristics of your material and the ambient temperature where you are.
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