(1. Harbin University of Civil Engineering, Harbin 1500062, China) Harbin Dacheng Mountain Concrete Manufacturing Co., Ltd., Harbin 150001, Heilongjiang, China; 3 Shenzhen Yantian District Quality Inspection Station, Shenzhen, Guangdong, China 5 Thermal Insulation Performance, Developed with Class 500 and 700 Aerated Concrete Block-matching insulation mortar with a compressive strength of more than 25 MPa is used for the masonry of aerated concrete blocks with good technical performance.
1 The conventional masonry mortar is generally a cement mortar or a mixed mortar. The bulk density of such mortar is 1600 (m°K). The bulk density of aerated concrete blocks is generally 450 to 750 kg/m3, and the thermal conductivity is 0.12. ~0.32WV (m°K) Using traditional mortar to build aerated concrete wall will make the masonry produce cold bridge, and the additional heat loss caused by the mortar joint is up to 15%~25% of the total heat loss. This study mainly adopts Expanded perlite, cement, calcium-enriched slag, and admixtures are used as raw materials to develop insulation mortar that matches the density grade 500 and 700 aerated concrete blocks. The use of the thermal insulation mortar can reduce the additional heat loss caused by the mortar joint and has good technical performance.
2 Test raw materials The test raw materials include ordinary portland cement, expanded perlite, calcium-added slag, and admixtures that can improve the ease of mortar.
2. The physical properties and chemical composition of cement, expanded perlite and calcium-enriched slag cement, expanded perlite, and calcium-enhancing slag are shown in Table 1 to Table 4, respectively. Table 1 Basic properties of cement Fineness Specific surface area Setting time (min) Resistance Compressive strength (MPa) Flexural strength (MPa) Initial setting of final coagulation 2 Basic properties of expanded perlite Density Particle size (dimensions at room temperature Thermal conductivity Moisture content Table 3 Chemical composition of calcined slag % Loss on ignition Table 4 Ca-retaining slag Basic properties Appearance Moisture content Bulk density Porosity Maximum particle size Water absorption Color Dark gray 2. Additives Due to the large difference in raw material densities of lightweight mortars, it is prone to delamination segregation during mixing and transportation and seriously affects the mixture. And its properties after hardening.Ordinary mortar generally use lime paste, mortar lime crystal or micro foam agent to improve the workability.For light insulation mortar, using lime paste or lime crystal will increase the density of mortar, use micro Foams are difficult to meet the requirements for lightweight mortars, and for this reason, we have formulated an admixture that can effectively ensure the workability of lightweight mortars and evenly distribute the components in lightweight mortars. Stop segregation, bleeding phenomenon.
3 Test results and analysis 3. Development of bulk density insulation mortar 500600 In order to determine the best mix ratio of insulation mortar, we conducted the following tests. First, we determined the optimum mix ratio of cement and expanded perlite. They were 15.0.1:5.5.1:6.0, respectively, and the admixture amount was 9.9% of cement quality. The test results are shown in Table 5. Table 5 Effect of different binder content on mortar performance No. Cement: perlite (volume) Quantity of each material (kg/m3) Consistency Stratification Dry density Cement perlite Admixture water See Table 5: With the increase of the amount of cement, the dry density of the mortar gradually increases, and the strength of the mortar after hardening also gradually increases.
Taking into account the requirements of production cost and heat preservation, the blending ratio of A2 was selected for the admixture volume test. The admixture volume was 1%, 3%, 6%, 9% and 12% of the cement quality, respectively. The consistency of the mortar mix is ​​basically unchanged. The experimental results are shown in Table 6. Table 6 Effect of Admixture Addition on Mortar Properties No. Admixture Addition Amount of Each Material (kg/m3) Consistency Lamination Degree Dry Density Cement Perlite Admixture Water It can be seen from the test results in Table 6 that: With the increase in the amount of admixtures, the water consumption and dry density per unit volume of insulation mortar are gradually reduced. When the admixture content is 1%, the compressive strength of the mortar is abnormal. This is because there are fewer mortars and additives, the gas content of the mortar is less, and the material components of different densities are mixed unevenly, resulting in delamination and segregation of the mortar. , Bleeding, the volume decreases after hardening, the dry density increases, and the strength increases. When the admixture content is 3%, the number of bubbles in the mortar increases, the gas content increases, the workability of the mortar mixture becomes better, the dry density decreases, and the strength decreases. With the increase in the admixture dosage, the water consumption is reduced, the workability of the mortar mixture becomes better, the gas content increases, the distribution of the components tends to be uniform, and the interface structure between the expanded perlite and the cement stone is improved. The degree of excess water accumulation in the aggregate around the aggregate decreases, the bond strength between the cement paste and the expanded perlite increases, and the increase is greater than the magnitude of the loss of strength due to the decrease in the amount of cement, so the macroscopic performance is the dry density reduction. Small, increased strength. When the admixture content exceeds 9% of the cement content, both the water consumption and the dry density tend to be stable, and the variation is small. Therefore, the best admixture amount is 9%. Comprehensive strength, delamination, and dry density Factors, select the mix ratio B4 as the best mix ratio of the bulk density 500-600 insulation mortar.
3.2 Development of bulk density 650750 thermal insulation mortar 1 New type of built-in solid material like 3 In the case where the strength remains unchanged, adding some active mineral admixture to replace part of the cement can reduce the cost. For this purpose, we added active calcium-enriched slag to replace part of the cement in the heat-insulating mortar mix ratio (excessive substitution method). The results are shown in Table 7. Table 7 Effect of Calcium-added Slag Content on the Performance of Thermal Insulating Mortar Cement No.: Perlite (Volume ) The amount of each material (kg/m3) Consistency Stratification Dry Density Cement Perlite Calcium Slag Admixture Water As can be seen from the test results, the dry density of mortar gradually increases as the amount of binder increases, compressive strength Gradually increase, select the mix ratio C2 = 650 ~ 700 grade mortar mix ratio 3. Thermal insulation mortar technical performance on the basis of the above test results, select the ratio B4 and C2 as the best mix ratio, its performance was tested The test results shown in Table 8 can satisfy the use of aerated concrete masonry.
Table 8 Basic Properties of Thermal Insulation Mortar Dry Density Compression Adhesion Strong Softening 90d Shrinkage Thermal Conductivity Frost Resistance Coefficient Notes: (1) Bond strength refers to the bond strength between thermal insulation mortar and aerated concrete block. 2) Frost resistance refers to the percent loss of strength after 15 freeze-thaw cycles.
3. Performance comparison with other thermal insulation mortars (see Table 9) Table 9 Performance comparison of several kinds of thermal insulation mortars. This product is a product of a research institute in Zhejiang. Products of a certain factory in Shanghai. Products of the former Soviet Union French products Cement: Perlite (volume) Dry density ( Kg/m3) Compressive strength (MPa) Thermal conductivity [WV(m°K)] 4 Conclusion The thermal insulation mortar has good technical performance.
For aerated concrete blocks of different density levels, heat insulation mortars with a dry density of 566 kg/m3 and 706 kg/m3 are used respectively, which can basically eliminate the heat loss caused by the cold joints caused by the mortar joints and achieve better insulation effect. .
In the case where the strength of the mortar is basically constant, the addition of active calcium-enriched slag can increase the dry density of the mortar and reduce the cost.
Contact address: Department of Materials Science and Engineering, Harbin Jianzhu University 491
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