Some experiences on the construction and application of external thermal insulation mortar under low temperature conditions

1. Introduction

In some northern areas, when the temperature drops below 0℃ in winter, some exterior walls need to be insulated. Projects require winter construction in order to rush the construction period or finish the project. However, the relevant national technical regulations and product standards do not make corresponding provisions for anti-freeze products and construction. As an insulation mortar manufacturer, it must not only meet construction needs but also ensure Product quality, thus placing new requirements on the performance of thermal insulation mortar during negative temperature construction.

2. Technical route

At present, some mortar companies usually use the following methods during low-temperature construction To solve:

2.1 Choose redispersible latex powder with a relatively low film-forming temperature as the binding material.

Select several redispersible latex powders with different film-forming temperatures. The dosage of rubber powder is 3%, and different temperatures of 0℃, -5℃, – For performance testing at 10°C, the test method is that after molding, the specimens are placed in a low temperature box for 7 days, and then taken out and placed at room temperature for 2 days. The inspection method shall refer to JG 149-2003 and shall be bonded with cement mortar.

Except for 1# rubber powder, the strength of the rest of the rubber powder basically decreases with the decrease of temperature. Since it is made of copolymerized monomers that can disperse the rubber powder, the ingredients Different ratios, protective colloids, etc. make each rubber powder may have different minimum molding temperatures. It is also one of the characteristics of the polymer. It is the lowest temperature at which the polymer forms a continuous film, so it has a negative impact on the practical application of redispersible rubber powder. Engineering applications play an important guiding role. Theoretically, in order for the redispersible rubber powder to form a film in the hardened mortar and form an interpenetrating network structure intertwined with the cement slurry, it must be ensured that the ambient temperature is higher than the minimum film-forming temperature of the redispersible rubber powder. . If the curing temperature is lower than this value, the polymer will exist in the form of discontinuous particles in the cement mortar. Only when the curing temperature is higher than the minimum film-forming temperature of the polymer, will the polymer form a continuous film evenly distributed between the cement hydration products, which can play a bridging role when there is stress and effectively absorb and transmit energy. Thereby inhibiting the formation and expansion of cracks and improving bond strength.

In the test, we found that although the strength of the mortar of different rubber powders will slowly recover after the negative temperature is converted to positive temperature, the adhesive strength after curing under the conversion to positive temperature conditions All can meet the standards, but they are not ideal in actual product applications. The main reason is that after bonding, the bonding mortar freezes at low temperatures and cannot be hydrated. Therefore, the initial bonding strength of the bonding mortar is very low. It will cause trouble for the next step of construction.

2.2 Choose early-strength antifreeze to improve the low-temperature performance of thermal insulation mortar

2.2.1 Antifreeze Selection

In the selection of antifreeze, some companies currently mainly choose antifreeze applied in concrete soil. After many tests, we believe that if the antifreeze of concrete is directly used, agent is inappropriate, because the antifreeze agent in concrete mainly improves the compressive strength of concrete at negative temperatures, and as the compressive strength of external thermal insulation mortar is not the most important technical indicator, thermal insulation mortar requires good bonding strength. That is to say, the antifreeze in the thermal insulation mortar requires the mortar to have good workability without reducing the bonding strength of the mortar. Through the standards of some special mortars such as: tile adhesive, exterior wall putty, tile caulking agent, concrete interface treatment agent, etc., it can be seen that product quality is judged more by testing bond strength, while compressive strength indicators are involved. There are relatively few. During the test, we selected many types of concrete antifreeze for testing and found that the bond strength will be reduced to varying degrees. Finally, the modified TB207 antifreeze was chosen.

2.2.1 The test formula is shown in Table 1

Table 1

2.2.1 Test methods and results

The test method is to quickly place the specimen into a -10°C low-temperature box after being formed. After placing it for 7 days, a cycle of -10°C low-temperature box for 16 hours and room temperature for 8 hours is made (similar to the actual construction conditions). After 7 cycles, it is placed at room temperature for 24 hours. test. The inspection method refers to JG 149-2003 bonding with cement mortar and bonding strength with EPS board.

After using TB207 antifreeze in thermal insulation mortar, the bonding strength is not reduced but can also be improved. In addition, by observing the bonding in the cryogenic chamber every day The test specimens found that the cement solidification speed of the specimens mixed with TB207 antifreeze was relatively fast. It was completely solidified and had a certain bonding strength in 2-3 days. This is very important and critical, because during the actual construction process, if within 3 days Carrying out the next step of construction before the thermal insulation mortar has a certain bonding strength will not only fail to gain the approval of the constructor and supervisor, but also pose a huge quality hazard. If the mortar is constructed after it has a certain bonding strength, the construction period will be increased. Of course, since there are currently no relevant technical standards for negative temperature construction, it is best not to construct in winter.

2

2

Heavy calcium

50

50

—

—

—

—

Antifreeze TB-207

—

5

—

8

—

8

2.2.1 Test methods and results

The test method is to quickly place the specimen into a -10°C low temperature chamber after molding After being placed for 7 days, a cycle of -10°C low temperature chamber for 16 hours and room temperature for 8 hours is made (similar to the actual construction conditions). After 7 cycles, it is placed at room temperature for 24 hours for testing. The inspection method refers to JG 149-2003 bonding with cement mortar and bonding strength with EPS board.

After using TB207 antifreeze in thermal insulation mortar, the bonding strength is not reduced but can also be improved. In addition, by observing the bonding in the cryogenic chamber every day The test specimens found that the cement solidification speed of the specimens mixed with TB207 antifreeze was relatively fast. It was completely solidified and had a certain bonding strength in 2-3 days. This is very important and critical, because during the actual construction process, if within 3 days Carrying out the next step of construction before the thermal insulation mortar has a certain bonding strength will not only fail to gain the approval of the constructor and supervisor, but also pose a huge quality hazard. If the mortar is constructed after it has a certain bonding strength, the construction period will be increased. Of course, since there are currently no relevant technical standards for negative temperature construction, it is best not to construct in winter.

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8

2.2.1 Test methods and results

The test method is to quickly place the specimen into a -10°C low temperature box after being formed, and after placing it for 7 days, – A cycle of 16 hours in a 10°C low temperature chamber and 8 hours at room temperature (similar to actual construction conditions), and after 7 cycles, placed at room temperature for 24 hours for testing. The inspection method refers to JG 149-2003 bonding with cement mortar and bonding strength with EPS board.

After using TB207 antifreeze in thermal insulation mortar, the bonding strength is not reduced but can also be improved. In addition, by observing the bonding in the cryogenic chamber every day The test specimens found that the cement solidification speed of the specimens mixed with TB207 antifreeze was relatively fast. It was completely solidified and had a certain bonding strength in 2-3 days. This is very important and critical, because during the actual construction process, if within 3 days Carrying out the next step of construction before the thermal insulation mortar has a certain bonding strength will not only fail to gain the approval of the constructor and supervisor, but also pose a huge quality hazard. If the mortar is constructed after it has a certain bonding strength, the construction period will be increased. Of course, since there are currently no relevant technical standards for negative temperature construction, it is best not to construct in winter. </p