CN101845886A - Phase-change temperature control large-volume concrete formwork and preparation method thereof - Google Patents

Abstract

The invention relates to a temperature-controlled large-volume concrete template prepared by using phase-change materials and a preparation method thereof. Wrap the phase change material in the concrete formwork, and use the phase change energy storage characteristics of the phase change material. When the surface temperature of the concrete is lower than the internal temperature, the phase change material absorbs the heat diffused from the inside of the concrete, and the material wrapped on the surface of the formwork A phase change (solid-liquid phase change) occurs so that the surface temperature of the concrete remains unchanged. At the same time, because the ambient temperature is lower than the concrete surface temperature, the material undergoing phase change will exchange heat with the external environment and wrap the concrete formwork. The material undergoes a phase change (liquid-solid phase change), and the absorbed heat is transferred out, so that the temperature of the concrete surface will not increase due to too much heat accumulation of the phase change material. The internal and external temperature gradient of the concrete can solve the cracking problem of large-volume concrete caused by the profit of the temperature gradient.

Description

A phase-change temperature-controlled mass concrete formwork and its preparation method

technical field

The invention relates to a phase-change temperature-controlled large-volume concrete formwork and a preparation method thereof.

Background technique

With the country's continuous investment in railway construction projects, there are more and more large-scale concrete projects, and the problem of shrinkage and cracking of large-volume concrete is becoming more and more common, which brings structural hidden dangers to the century-old railway construction.

The occurrence of cracks in mass concrete structures is caused by many factors. The most important factor is the temperature gradient stress.

There are two reasons for the temperature gradient stress. On the one hand, the temperature gradient stress generated by the cement hydration heat. Due to the large amount of heat of hydration generated in the process of cement setting and hardening, generally about 500J of heat can be released per gram of cement. If the amount of cement is calculated at 350Kg/m ³ to 550Kg/m ³ , 17500KJ to 27500KJ will be released per cubic meter of concrete. heat. And it is not easy to dissipate when it gathers in the mass concrete, so the temperature rise inside the concrete is much larger than the temperature rise on the surface. In the process of cooling after the concrete heating peak, due to the different heat dissipation conditions, the internal cooling rate is much slower than that of the surface layer. Therefore, the temperature inside the mass concrete is very high, which will form a temperature gradient, and this temperature gradient will produce a temperature gradient stress due to the temperature deformation of the concrete. Once the temperature stress exceeds the tensile limit value that the concrete can bear, cracks will appear in the concrete.

On the other hand, the temperature gradient stress caused by the external air temperature. During the construction of mass concrete structures, the change of outside air temperature has a great influence on the generation of mass concrete cracks. The temperature inside the concrete is composed of the superposition of various temperatures such as the pouring temperature, the adiabatic temperature rise of the cement hydration heat, and the heat dissipation temperature of the structure. The pouring temperature is directly related to the outside air temperature. The higher the outside temperature, the higher the concrete pouring temperature will be; if the outside temperature decreases, the internal and external temperature gradient of mass concrete will increase. If the external temperature drops too fast, it will cause a lot of temperature stress, which will easily lead to concrete cracking.

Contents of the invention

The object of the present invention is to provide a phase-change temperature-controlled mass concrete formwork and a preparation method thereof.

The phase-change temperature-controlled large-volume concrete formwork proposed by the present invention is composed of wrapping materials and phase-change materials. The phase-change temperatures of the phase-change materials from the inside to the outside are 30±2°C, 40±2°C and 50±2°C. ℃ of 3 layers of materials; the wrapping material is coated on the outside of the phase change material; among them: the phase change material of the inner layer is composed of n-decanoic acid and expanded perlite, and the phase change material of the middle layer is composed of lauric acid and expanded perlite The phase change material of the outer layer is composed of stearic acid, palmitic acid, lauric acid and expanded perlite.

In the present invention, the thickness of the phase change material is 1-2mm.

The preparation method of the phase change temperature-controlled mass concrete formwork proposed by the present invention, the specific steps are as follows:

(1) Put the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and vacuum the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve, slowly add the fully dissolved n-decanoic acid, after the addition of n-decanoic acid is completed, open the vacuum pumping valve to a negative pressure of 0.8-1.48MPa, accelerate stirring for 30-60 minutes; close the pumping valve, discharge Material, cooling; To obtain the phase change material whose phase change temperature is 30±2°C; wherein: the weight ratio of n-decanoic acid and expanded perlite is 1:0.9-0.9:1;

(2) Place the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and evacuate the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve, slowly add the fully dissolved lauric acid, after the lauric acid is added, open the vacuum pumping valve to a negative pressure of 0.8-1.48MPa, accelerate stirring for 30-60 minutes; close the pumping valve, discharge, Cooling; to obtain a phase change material with a phase change temperature of 40 ± 2°C; wherein: the weight ratio of lauric acid to expanded perlite is 1: 0.9-0.9: 1;

(3) Place the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and evacuate the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve and slowly add the completely dissolved stearic acid, palmitic acid and lauric acid. After the stearic acid, palmitic acid and lauric acid are added, open the vacuum valve to a negative pressure of 0.8-1.48MPa , accelerate stirring for 30 to 60 minutes; close the exhaust valve, unload, and cool; that is, a phase change material with a phase change temperature of 50±2°C; wherein: stearic acid, palmitic acid and lauric acid and expanded perlite The weight ratio is 1:-0.8-1:0.8-1:0.8-1;

(4) Three layers of phase change materials with phase transition temperatures of 30±2°C, 40±2°C and 50±2°C were divided into inner layer, middle layer, and outer layer and wrapped in the mass concrete formwork wrapping material, each layer The thickness of the phase change material is 1-2 mm.

In the present invention, the expanded perlite is used to adsorb the phase change temperature control material, so the expanded perlite should be untreated and have adsorption properties.

The present invention utilizes hard acid with a melting point of 69.6±2°C, palmitic acid with a melting point of 63°C, lauric acid with a melting point of 41±2°C, and n-decanoic acid with a melting point of 31±2°C. After compounding two or any three kinds, and then compounding with expanded perlite, the obtained phase change materials have phase change temperatures of 30±2°C, 40±2°C and 50±2°C respectively, which are suitable for reducing Temperature gradient stress of mass concrete, phase change energy storage material for formwork to solve the cracking of mass concrete due to temperature gradient stress. The phase-change material produced by the invention is applied to a large-volume concrete formwork, significantly reduces the temperature gradient inside and outside the large-volume concrete, and solves the problem of cracking of the large-volume concrete due to temperature gradient stress.

The way to control the temperature of the product prepared by the present invention is: the heat diffused from the inside of the mass concrete absorbs heat through the phase change material, undergoes a phase change, and saves the heat, so that the mass concrete formwork maintains a certain temperature. The environmental temperature is lowered, so as to solve the problem of stress cracking caused by the excessive temperature gradient inside and outside the mass concrete.

The beneficial effects of the present invention are:

The present invention adopts 4 kinds of materials that undergo phase change at different temperatures, and composites them into a phase change material at a certain temperature, which is used to make a formwork for large-volume concrete. According to the characteristics of the phase change material, it changes shape with the change of temperature and can provide latent heat , to reduce the internal and external temperature gradient of mass concrete, thereby solving the cracking problem of mass concrete due to temperature gradient stress.

Detailed ways

The present invention is further illustrated below by way of examples.

Example 1:

(1) Put the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and vacuum the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve, slowly add the fully dissolved n-decanoic acid, after the addition of n-decanoic acid is completed, open the vacuum pumping valve to a negative pressure of 0.8-1.48MPa, accelerate stirring for 30-60 minutes; close the pumping valve, discharge Material, cooling; To obtain the phase change material whose phase change temperature is 30±2°C; wherein: the weight ratio of n-decanoic acid and expanded perlite is 1:1;

(2) Place the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and evacuate the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve, slowly add the fully dissolved lauric acid, after the lauric acid is added, open the vacuum pumping valve to a negative pressure of 0.8-1.48MPa, accelerate stirring for 30-60 minutes; close the pumping valve, discharge, Cooling; to obtain a phase change material with a phase change temperature of 40±2°C; wherein: the weight ratio of lauric acid to expanded perlite is 1:1;

(3) Place the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and evacuate the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve and slowly add the completely dissolved stearic acid, palmitic acid and lauric acid. After the stearic acid, palmitic acid and lauric acid are added, open the vacuum valve to a negative pressure of 0.8-1.48MPa , accelerate stirring for 30 to 60 minutes; close the exhaust valve, unload, and cool; that is, a phase change material with a phase change temperature of 50±2°C; wherein: stearic acid, palmitic acid and lauric acid and expanded perlite The weight ratio is 1:1:1:1;

(4) Three layers of phase change materials with phase transition temperatures of 30±2°C, 40±2°C and 50±2°C were divided into inner layer, middle layer and outer layer and wrapped in the mass concrete formwork wrapping material resin, each The thickness of the layer phase change material is 1.5 mm.

The phase-change temperature-controlled mass concrete formwork prepared by the present invention is applied to Project A, and the mass concrete poured by using the phase-change temperature-control mass concrete formwork has different hydration ages, the central temperature of the mass concrete and the surface temperature The temperature difference between temperatures is shown in Table 1. For mass concrete poured with ordinary concrete pouring formwork, at different hydration ages, the temperature difference between the center temperature and surface temperature of mass concrete is shown in Table 2.

Table 1 The internal and external temperature of project A after adopting mass concrete phase change temperature control formwork

temperature point 1 2 3 4 5 6 7 8 9 10 Internal temperature (℃) 71 72 73 72 74 71 69 71 72 72 External temperature (℃) 52 50 51 52 51 50 50 52 51 50

Table 2 Internal and external temperature after using ordinary concrete formwork in Project A

temperature point 1 2 3 4 5 6 7 8 9 10 Internal temperature (℃) 75 69 70 72 73 75 72 70 68 75 External temperature (℃) 30 29 33 27 30 33 30 31 29 28

Example 2:

(1) Put the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and vacuum the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve, slowly add the fully dissolved n-decanoic acid, after the addition of n-decanoic acid is completed, open the vacuum pumping valve to a negative pressure of 0.8-1.48MPa, accelerate stirring for 30-60 minutes; close the pumping valve, discharge Material, cooling; To obtain the phase change material whose phase change temperature is 30±2°C; wherein: the weight ratio of n-decanoic acid and expanded perlite is 1:1;

(2) Place the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and evacuate the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve, slowly add the fully dissolved lauric acid, after the lauric acid is added, open the vacuum pumping valve to a negative pressure of 0.8-1.48MPa, accelerate stirring for 30-60 minutes; close the pumping valve, discharge, Cooling; to obtain a phase change material with a phase change temperature of 40±2°C; wherein: the weight ratio of lauric acid to expanded perlite is 1:1;

(3) Place the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and evacuate the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve and slowly add the completely dissolved stearic acid, palmitic acid and lauric acid. After the stearic acid, palmitic acid and lauric acid are added, open the vacuum valve to a negative pressure of 0.8-1.48MPa , accelerate stirring for 30 to 60 minutes; close the exhaust valve, unload, and cool; that is, a phase change material with a phase change temperature of 50±2°C; wherein: stearic acid, palmitic acid and lauric acid and expanded perlite The weight ratio is 1:1:1:1;

(4) Three layers of phase change materials with phase transition temperatures of 30±2°C, 40±2°C and 50±2°C were divided into inner layer, middle layer and outer layer and wrapped in the mass concrete formwork wrapping material resin, each The thickness of the layer phase change material is 1.5mm.

Apply the phase-change temperature-controlled mass concrete formwork prepared by the present invention to Project B. The mass concrete poured by using the phase-change temperature-control mass concrete formwork has different hydration ages, the central temperature of the mass concrete and the surface temperature. The temperature difference between the temperatures is shown in Table 3. For the mass concrete poured with ordinary concrete pouring formwork, the temperature difference between the center temperature and the surface temperature of the mass concrete is shown in Table 4 at different hydration ages.

Table 3 The internal and external temperature of B project after adopting mass concrete phase change temperature control formwork

temperature point 1 2 3 4 5 6 7 8 9 10 Internal temperature (℃) 120 125 118 112 121 115 119 127 109 118 External temperature (℃) 90 88 95 87 86 90 80 99 114 89

Table 4 Internal and external temperature after ordinary concrete formwork is adopted in Project B

temperature point 1 2 3 4 5 6 7 8 9 10 Internal temperature (℃) 119 127 120 122 109 115 114 115 115 127 External temperature (℃) 34 32 25 28 38 35 29 32 27 37

It can be seen from Tables 1 and 2 that there is a large difference in the internal and external surface temperatures of the large-volume concrete poured using the two formworks, and the temperature difference between the internal and external surfaces of the large-volume concrete poured using the phase-change temperature-controlled formwork is about 20 °C , while the large-volume concrete poured with ordinary concrete pouring formwork has a temperature difference of about 40°C between the inside and outside.

It can be seen from Tables 3 and 4 that the temperature difference between the inner and outer surfaces of the large-volume concrete poured with the mass-concrete phase-change temperature-controlled formwork has a more significant effect of reducing the temperature difference between the inner and outer surfaces of the concrete when the internal temperature reaches above 100 °C. The ordinary concrete formwork basically does not play a role in controlling the temperature difference between the inside and outside of the mass concrete.

Obviously, the use of mass concrete phase change temperature control formwork is beneficial for controlling the external temperature of mass concrete and reducing the internal and external temperature gradient of mass concrete.

Claims (3)

1. A phase-change temperature-controlled large-volume concrete formwork, characterized in that it is composed of a wrapping material and a phase-change material, and the phase-change temperature of the phase-change material from the inside to the outside is 30±2°C, 40±2°C and Composed of 3 layers of materials at 50±2°C; the wrapping material is coated on the outside of the phase change material; among them: the phase change material of the inner layer is composed of n-decanoic acid and expanded perlite, and the phase change material of the middle layer is composed of lauric acid and expanded perlite. It is made of perlite, and the phase change material of the outer layer is made of stearic acid, palmitic acid, lauric acid and expanded perlite. 2. The phase-change temperature-controlled mass concrete formwork according to claim 1, characterized in that the thickness of the phase-change material is 1-2 mm. 3. a preparation method of phase change temperature control mass concrete formwork as claimed in claim 1, is characterized in that concrete steps are as follows: (1) Put the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and vacuum the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve, slowly add the fully dissolved n-decanoic acid, after the addition of n-decanoic acid is completed, open the vacuum pumping valve to a negative pressure of 0.8-1.48MPa, and accelerate stirring for 30-60 minutes; close the pumping valve, discharge Material, cooling; To obtain the phase change material whose phase change temperature is 30±2°C; wherein: the weight ratio of n-decanoic acid and expanded perlite is 1:0.9-0.9:1; (2) Place the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and evacuate the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve, slowly add the fully dissolved lauric acid, after the lauric acid is added, open the vacuum pumping valve to a negative pressure of 0.8-1.48MPa, accelerate stirring for 30-60 minutes; close the pumping valve, discharge, Cooling; to obtain a phase change material with a phase change temperature of 40 ± 2°C; wherein: the weight ratio of lauric acid to expanded perlite is 1: 0.9-0.9: 1; (3) Place the expanded perlite in a vacuum kettle for heating and stirring, keep the temperature of the water bath at 50-70°C, heat for 10-40 minutes, and evacuate the vacuum kettle to a negative pressure of 0.5-0.8MPa; close the exhaust valve, Open the liquid inlet valve and slowly add the completely dissolved stearic acid, palmitic acid and lauric acid. After the stearic acid, palmitic acid and lauric acid are added, open the vacuum valve to a negative pressure of 0.8-1.48MPa , accelerate stirring for 30 to 60 minutes; close the exhaust valve, unload, and cool; that is, a phase change material with a phase change temperature of 50±2°C; wherein: stearic acid, palmitic acid and lauric acid and expanded perlite The weight ratio is 1:-0.8-1:0.8-1:0.8-1; (4) Three layers of phase change materials with phase transition temperatures of 30±2°C, 40±2°C and 50±2°C were divided into inner layer, middle layer, and outer layer and wrapped in the mass concrete formwork wrapping material, each layer The thickness of the phase change material is 1-2 mm.