After adding the cover clothes, the next step is to wet the cover clothes.
Similarly, the tank car transporting concrete also involves the problem of color, and do not use dark colors.
When the liquid evaporates or boils, keeping the temperature unchanged, energy must be input from the outside, so that the heat in the tank and the heat of solar radiation can be taken away by absorbing latent heat to cool down.
Therefore, the measures to reduce the concrete temperature are also measures to ensure the concrete quality.
Specifically, pay attention to the sunscreen of aggregates, add ice chips or ice water to mix the concrete, and reduce the cement dosage by selecting reasonable raw materials and adopting good mix proportion.
Fixing Socket Cross Hole Nail Plate
From the choice of construction period, try to avoid high temperature period.
Red, blue and green objects have different reflective and endothermic ratios due to the difference in material and color brightness, but generally speaking, they are relatively close.
In the total radiant energy, the wavelength is 0.15 ~ 4 μ M accounts for more than 99%, and is mainly distributed in the visible light region and the red and ultraviolet regions.
When the pouring temperature is lower than 16 ℃ ~ 18 ℃, the actual temperature rise per 100kg of cement is 12 ℃.
These colors not only make people feel cool psychologically, but also can actually keep objects at a relatively low temperature.
The color of powder storage tank will directly affect the temperature of cementitious materials, which is often ignored because different colors have different degrees of heat absorption.
Of course, the light color of the cover is better.
Figure 2 tank cars with different colors.
The band range of solar radiation observed on the ground is about 0.295 ~ 2.5 μ m。 Less than 0.295 μ M and greater than 2.5 μ M-wavelength solar radiation cannot reach the ground due to the strong absorption of ozone, water vapor and other atmospheric molecules in the earth’s atmosphere.
According to the theory of molecular motion of matter, the average distance of molecules in gas is much larger than that in liquid.
The main feature of summer is high temperature and rainy.
This kind of work is called internal skill.
The faster the hydration reaction, the greater and faster the slump loss of concrete, and the more difficult it is to control the construction quality.
The heat of vaporization of water is 40.8 kJ / mol, equivalent to 2260 kJ / kg.
Therefore, painting the storage tank white is the best choice.
Solar radiation is mainly concentrated in the visible part (0.4 ~ 0.76 μ m) , infrared with wavelength greater than visible light (>0.76 μ m) And ultraviolet light less than visible light (<0.4 μ m) Less.
Obviously, dark color will absorb more visible light.
The lowest heat absorption rate is white.
For dark tank cars, it is a better method to add a cover.
Figure 1 white tank and dark tank.
Some colors can reflect light without absorbing heat, so that the actual temperature of the object is relatively low, while some colors can absorb light and heat at the same time, so that the actual temperature of the object is relatively high.
The empirical formula of the relationship between the rate constant of chemical reaction and temperature shows that the higher the temperature is, the faster the reaction speed is.
The heat of vaporization is a physical property of a substance.
In winter, in order to prevent the heat in the tank from dispersing, and in summer, in order to prevent the external heat from guiding in, it plays a role of isolation from the environment.
The mixer truck itself also carries water with it.
Because the heat of vaporization only changes the phase of the substance without changing the temperature of the substance, it is also called latent heat of vaporization.
In order to reduce the cement temperature, it is best to add several powder tanks, which can be used interchangeably, so as not to cause the cement temperature to be too high.
The result of the increase of pouring temperature is that the whole temperature of newly poured concrete increases..
Doing work requires a certain amount of energy.
It is defined as the heat required to evaporate a mole of substance at a certain temperature at standard atmospheric pressure (101.325kpa), which is a function of temperature for a substance.
In addition, when a substance changes from liquid phase to gas phase, its volume will increase many times, so it must also resist atmospheric pressure and do work, which is called external work.
What is the impact of temperature on concrete? First, let’s look at Arrhenius’ formula: K is the rate constant, R is the molar gas constant, t is the thermodynamic temperature, EA is the apparent activation energy, and a is the pre exponential factor (also known as the frequency factor).
When the pouring temperature is 21 ℃, the actual temperature rise per 100kg of cement increases to 16 ℃.
First, reduce the concrete outlet temperature.
When matter changes from liquid phase to gas phase, it must overcome the attraction between molecules and do work.
So light absorption and heat absorption are not exactly the same thing.
It is worth mentioning that Navy Blue has a relatively low lightness and a relatively thick color, but its heat absorption rate is relatively low.
The visible light region accounts for about 50% of the total solar radiation energy, the infrared region accounts for about 43%, and the solar radiation energy in the ultraviolet region is very small, accounting for only about 7% of the total.
The evaporation of water can take away radiant heat and tank heat.
It’s summer construction and high incidence of quality problems.
In liquid state, there is a strong attraction between the molecules of matter.
It is very helpful to keep the cover clothes moist.
It is also an effective measure to cool the aggregate by watering the ground water.
During this period, I visited some enterprises and sites and found that some problems still need to be paid attention to.
Figure 3 concrete tank cars with coverings for concrete tank cars, in fact, coverings should be added in winter and summer.
Bright colors such as white, yellow and light blue can reflect light, but they are not easy to absorb heat, while colors such as black and fuchsia are easy to absorb light and heat.
The research shows that the higher the outside temperature is, the higher the pouring temperature of concrete is.
The most endothermic color is black, followed by dense colors such as Tan, followed by red, yellow and white.
