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1 preface
Building adhesives are widely used in building engineering, and their application fields are constantly expanding, with great market potential. Building adhesives with polyvinyl alcohol as the main raw material, such as 107 building adhesive and 80 1 building adhesive, occupy a large share in the building adhesive market. The biggest advantage of polyvinyl formal is its low price and wide application. In recent 20 years, its output has been continuously improved and its application scope has been continuously expanded. At present, it is widely used in indoor decoration materials, wall and floor tile pasting materials, external wall plastering materials, etc. Because this binder is made of polyvinyl alcohol and formaldehyde by condensation reaction, formaldehyde is artificially introduced as raw material, and the binder contains a certain amount of free formaldehyde. In the process of production, construction and use, free formaldehyde is continuously released, which affects indoor air quality and harms human health. The voice of gradually restricting or even prohibiting the use is increasing. However, this kind of binder has low price, good performance and wide application range. According to the existing conditions in China, these binders still occupy a certain market. The environment-friendly building adhesive discussed in this paper is a building adhesive with extremely low free formaldehyde content on the basis of maintaining the advantages of polyvinyl formal collagen.
2. The influence of raw materials on environment-friendly building adhesives
Factors The main raw material of environment-friendly building adhesive is still polyvinyl alcohol, but formaldehyde is no longer added for acetalization reaction, but other additives are selected to modify the molecules of polyvinyl alcohol to improve the bonding strength and viscosity of environment-friendly building adhesive.
2. 1 tackifier
Non-acetalized polyvinyl alcohol solution can't directly replace the original building glue, and it can't reach the corresponding performance indexes in viscosity and cohesiveness. It is necessary to introduce tackifier to improve the bonding strength of polyvinyl alcohol and the viscosity of materials. There are many options for tackifiers. Physical methods can be adopted, such as adding other polymer materials as tackifier in polyvinyl alcohol solution to achieve the predetermined effect, and at the same time, considering the compatibility and complementarity between the added materials and polyvinyl alcohol solution, the environmental protection index of the materials, and paying attention to the influence of material price on the final product cost; Chemical reaction can also be used to make the added materials react with polyvinyl alcohol molecules, especially with some groups on the molecular chain, so as to improve the cohesiveness and viscosity of the products, thus achieving the physical and mechanical properties and environmental protection standards of building adhesives. The chemical method is characterized by reasonable selection and design of the variety and dosage of tackifier, direct modification of polyvinyl alcohol, and easy control of product performance and cost.
2.2 catalyst
Another key to the production of building adhesives by modifying polyvinyl alcohol by chemical methods is to select suitable catalysts. The variety and dosage of catalyst affect the process conditions such as temperature control and time control of chemical reaction, and also affect the technical performance index of products. When choosing the catalyst, we should also consider the environmental protection index of the product.
2.3 Other auxiliary equipment
By using some additives, such as changing reaction conditions and adding necessary stabilizers, the chemical reaction can be controlled to stop at an appropriate time and stable products can be obtained. Polyvinyl alcohol solution is prone to mildew (especially in hot and humid areas in the south). After acetalization with formaldehyde, there is a large amount of free formaldehyde in the system, which can play a role in mildew prevention and sterilization. The formaldehyde-free environment-friendly building adhesive does not contain free formaldehyde. In addition to choosing clean water, the choice of mildew inhibitor is also very important. Many industrial fungicides contain harmful compounds, so it is not suitable to choose them here.
3 synthesis process of environmental protection building adhesive
Attention should be paid to the time, speed and temperature control of adding catalyst, tackifier and stabilizer in the production of environmentally friendly building adhesive. Choose the appropriate reaction kettle and other equipment, the stirring form and speed of the reaction kettle can meet certain requirements. The technological process of environment-friendly building adhesive is as follows:
4 technical performance index of environmental protection building adhesive
The technical performance of environment-friendly adhesive should meet the following standards: JC4389 1 Water-soluble polyvinyl formal adhesive GB 18583200 1 Limit of harmful substances in adhesives for interior decoration materials. The test method of each performance shall be carried out in accordance with the methods specified in the above two standards. See table 1 for the main technical properties of environmental-friendly building adhesives.
5 conclusion
(1) According to a certain formula, the building adhesive meeting the relevant standards can be produced in the production equipment that meets the requirements and according to the determined technological process.
(2) Environmental-friendly building adhesive has the characteristics of high bonding strength and good environmental protection performance. It has a wide application range and moderate price, and is a new generation of building adhesive that meets the requirements of environmental protection.
References:/cailiao/081027/16202856.html.
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Respondents:1519761952-Qian Zongwu11-3 23:11.
Quality control of one-step forming of large area concrete emery ground.
In order to avoid cracks in concrete and control ground smoothness, effective technical measures have been taken in optimizing mix design, improving construction technology, improving construction quality and strengthening maintenance.
Keywords: quality control of crack formation
Guangzhou Siwei Heavy Industry Co., Ltd. is located at No.5 Dongjiang Avenue, West Zone of Guangzhou Economic and Technological Development Zone. This project consists of production workshop, power workshop and storage yard. The production workshop adopts bent structure and the power workshop adopts reinforced concrete frame structure. The upper part of the workshop is a steel roof truss, with a single floor and four floors, with a building area of about 10 125m2 and a building height of16.72m.: : The power workshop has a building area of 200.5 m2 and a building height of 6m. The building area of the communication room is 5 1.27 m2, and the building height is 3.5m There is also a pile of fields. The ground of production workshop and storage yard is formed by grinding emery ground once. The thickness of foundation concrete is 300mm, and the design strength is C30. The whole foundation consists of 732 caps with different specifications and bottom plates between the caps, with an area of 12845 m2, which is relatively large. Because the construction site is located at the intersection of the Pearl River and Dongjiang River, the water level of the river is high at high tide, so the production layer has anti-seepage requirements. Therefore, it is necessary to formulate an effective scheme to control the quality during construction and after foundation formation.
First, crack control.
The main reasons why cracks may occur when pouring compacted foundation concrete are: high strength grade of foundation concrete and high hydration heat; In winter construction, the ambient temperature is low (about 12 ~ 10℃ in Guangzhou), and the temperature difference between concrete and ambient temperature is large; Improper curing, sudden cold water curing when the concrete temperature is high, will also produce many irregular micro-cracks, which can lead to floor leakage. In order to prevent cracks, it is necessary to set expansion and post-pouring zones in the design, cut cracks on the emery ground after completion, improve the construction technology during construction, reduce the temperature stress of concrete and improve the resistance of concrete.
1, mix design and trial match
In order to reduce the temperature stress of concrete, the best way is to reduce the hydration heat of concrete. Therefore, we must do a good job in concrete mix design and trial mixing.
1. 1, raw material selection
1. 1. 1. Cement: Fly ash silicate cement with low hydration heat shall be selected to minimize the cement consumption. 425 # fly ash cement is selected for this project.
1. 1.2. Fine aggregate: medium sand in Zone II is suitable, because the use of medium sand can reduce the amount of water and cement compared with fine sand.
1. 1.3. Coarse aggregate: under the pumping condition, continuous graded stone with particle size of 5~20 is selected to reduce the shrinkage and deformation of concrete.
1. 1.4. Mud content: Too much mud content in aggregate will not only increase the shrinkage deformation of concrete, but also seriously reduce the tensile strength of concrete, which is very unfavorable for crack resistance. Therefore, the aggregate must be sampled and determined on site, and the silt content of stones should be controlled within 65438 0%, and the silt content of sand should be controlled within 2%.
1. 1.5. admixture: fly ash mixing technology is adopted. Adding fly ash into concrete can not only reduce the cement consumption, reduce the hydration heat and increase the workability of concrete, but also greatly improve the later strength of concrete, and the 28-day strength of concrete can be close to the standard strength value of concrete.
1. 1.6, admixture: UEA micro-expansive agent technology is adopted. About 10% UEA is added to concrete. The test shows that after UEA is added to concrete, the expansion stress generated in concrete can compensate the shrinkage stress of concrete, thus improving the crack resistance of concrete accordingly.
1. 1.7, trial mixing and determination of construction mix proportion: according to the laboratory mix proportion design, the mix proportion of concrete per cubic meter is 275kg of No.525 cement, continuously graded macadam (particle size 5-20 mm)1031kg, 73kg of admixture, 5.28kg of admixture, and 5.28 kg of aggregate.
2. Because the thickness of concrete base is only 300mm, it can be cured by common covering, water spraying or spraying, which can ensure that the internal and external temperatures of concrete (center and surface, surface and nickname) are less than 25℃.
3. Problems needing attention in construction: Within 7~ 10 days after the formation of emery ground, cracks in internal corners usually appear at the junction of ground and column, which is mainly due to the change of stiffness. There are structural vertical cracks at the internal corner of the turning point of the plane shape of foundation concrete, which are open from top to bottom, wide at the top and narrow at the bottom. This is due to the combined action of shrinkage stress, settlement and temperature stress, and the concentrated stress formed at the corner exceeds the tensile strength of concrete. In order to prevent cracks in concrete at internal corners, in addition to using concave-convex surfaces as little as possible in design and adopting structural measures such as additional reinforcement at internal corners, the construction quality of concrete at internal corners should also be ensured during construction, and curing should be carried out by covering, sprinkling water or spraying curing agent in time to control the premature formwork removal.
4. Surface treatment
4. 1, Introduction of emery:
There are two kinds of ground hardeners, one is nonmetal ground hardener, the other is metal ground hardener, and the two kinds of hardeners are composed of nonmetal or metal aggregate, standard portland cement and other wetting materials, which can be used after opening the bag. High strength, wear resistance and dust prevention, effectively increase the oil resistance of the ground and shorten the construction period. Generally used in industrial floors that must be wear-resistant and dust-proof. Its 28-day strength; Non-metallic ground hardener 80mpa；; Metal floor hardener floor 9 1mpa. It may be open for driving after 48~72 hours of construction: light trucks can drive after 7~ 10 days; It can be used normally after 28 days.
4.2, emery ground construction method:
Concrete at the grass-roots level shall be vibrated in time. First of all, the concrete in the middle of the material should be vibrated to form a natural flowing slope, and then fully vibrated. In order to improve the ultimate tensile strength of concrete, prevent cracks due to the settlement of concrete, reduce internal micro-cracks and improve the compactness of concrete, the method of secondary vibration is also adopted. When the vibrator is pulled, the concrete can still close itself without leaving holes in the concrete. This is the right time to apply secondary vibration, but the vibration should not be too large to prevent segregation. Due to the thick cement on the surface of the pumped concrete, a long trowel shall be used for initial leveling within 3 ~ 4 hours after pouring the foundation concrete, and it shall be rolled twice with an iron roller before initial setting, and then leveled and compacted with a wooden trowel to control the surface cracking and reduce the water emission on the concrete surface. Then, use a special trowel and disc to further level the concrete to ensure that the concrete surface is smooth and dense. After the initial setting of concrete, the hardener shall be sprinkled before the final setting, and the trowel and disc shall be used for compaction and leveling. After 24 hours, slit the finished surface to prevent cold cracks.
After about 1~2 hours, the operations of sowing and compaction are repeated again; Finally, polish the seal with a trowel and a blade, and repair the corners manually at the same time; Finally, spray curing agent or covering film to prevent cracking caused by rapid evaporation of water. From concrete leveling to covering curing, all operation processes should be completed within 24 hours. 2~3 days after the construction is completed, you can walk in public, and cut seams on the finished surface to prevent cold cracking.
5. Maintenance measures: adopt common water spraying for maintenance.
6. Improve the construction organization and management: while formulating technical measures and quality control measures, implement the organization and command system and make technical disclosure step by step to ensure smooth implementation.
7, problems that should be paid attention to in the construction.
7. 1, try to shorten the concrete transportation time, arrange the pouring sequence reasonably, and discharge in time; Before pouring, rinse the formwork with water to cool it; The pump pipe is wrapped in linen to prevent the sun from getting hot;
7.2, ensure the vibrating compaction, strictly control the vibrating time, moving distance and insertion depth, to prevent vibration leakage and excessive vibration;
7.3, ensure the supply of concrete, not arbitrarily lien construction joints;
7.4, do a good job of site coordination, organization and management, should have enough manpower and material resources, to ensure the smooth progress of the construction as planned.
Second, flatness and flatness control
The surface of factory floor is made of undisturbed concrete mixed with hardener to increase its surface hardness. In the construction process, after simple treatment (leveling with a long scraper and rolling with a roller), the concrete surface is polished with a special mechanical trowel before initial setting, and the surface hardness after maintenance can meet the requirements of heavy load without damage.
For this practice, on the one hand, it saves the cost of adding 20mm thick cement mortar integral surface layer on the floor, thus saving investment; On the other hand, under the condition of the same structural height, the thickness of 20 mm cement mortar integral surface layer is reduced, thus increasing the room clearance of 20 mm.
On the other hand, this method reduces the design difficulty. Because the delta area is mostly soft soil foundation, the bearing capacity of the foundation is relatively weak, and the cost of dealing with the bearing capacity of the foundation is higher than that of the whole project. The density of cement mortar is calculated as 2000kg/m3. At this time, if the weight of 20mm thick integral mortar pavement is reduced, the structural weight per square meter of construction area will be reduced by1×1× 0.002× 2000 = 40 (kg). The design standard value of the uniformly distributed load on the ground of this workshop is 3000kg/m2, which is equivalent to reducing the load by 40/3000= 1.33%, and correspondingly reducing the foundation treatment cost, thus reducing the investment of the construction unit and the design difficulty of the design unit.
And the construction is convenient. Compared with the shear wall structure of residential buildings, when the disc grinder with the diameter of 1m is used for emery ground treatment, the workshop with large bay has enough operation surface, and it can be mechanized except for the ground and the post-grafting of the workshop, thus reducing the precision reduction caused by the unqualified technical quality of workers.
Analysis on construction difficulties of one-step forming concrete floor slab
1. 1. There is no quality acceptance standard for once-molded concrete floor in the current specification. According to the Code for Acceptance of Construction Quality of Concrete Engineering, the flatness requirement of concrete ground (rough ground) is 8mm, which can generally be met. However, the only acceptance standard that can be referenced in the construction process can only be the flatness (4mm) of the mortar surface in the Code for Acceptance of Construction Quality of Building Ground Engineering. In this way, it is much more difficult for the construction unit to form the concrete floor at one time than the mortar surface floor.
1.2. As the design requires the ground to be formed once before the superstructure can be constructed, it is very likely that the formed ground will be damaged during the construction. During the installation and removal of columns, ring beams and steel roof trusses, the formed ground may be destroyed, which will greatly increase the cost of technical measures and management difficulty of product protection.
Control measure
After the steel bar binding, level shall be placed around the site, elevation shall be introduced by control points, a steel bar perpendicular to the ground shall be welded on the floor steel bar every 4m×4m, and the steel bar shall be cut off at the ground molding elevation position. When pouring concrete, the exposed steel bar head controls the ground forming elevation. When pouring concrete, the thickness is slightly higher than the steel bar head, and then it is vibrated and compacted. Then check the flatness with the steel bar head as a symbol, and then recheck the elevation with a second long ruler to ensure that the elevation error is controlled within 4 mm After the initial setting of concrete, make emery ground, rub the position where the vertical steel bar is placed flat with a wooden trowel, and mix emery with concrete slurry to make the surface layer closely integrated.
After the emery ground is formed, it is necessary to implement the technical measures to protect the finished product, and water conservation is required within 2~3 days after the ground strength is reached, and 2~3 layers of film are covered to prevent the rapid evaporation of water and protect the ground. In the follow-up construction of the main structure, materials shall be lifted manually, and it is forbidden to leave them behind. When hoisting the steel roof truss, the truck crane must be driven into the factory building, so it is required to lay 20mm thick sand on the ground and cross-pad two layers of 10× 10 wooden fang under the truck crane support frame to prevent the concentrated load from damaging the ground.
Conclusion: Through field test, no temperature deformation cracks are found in the foundation, and the ground flatness and smoothness can meet the requirements on the whole. Practice has proved that taking effective technical measures in optimizing mix design, improving construction technology, improving construction quality and strengthening maintenance, and adhering to strict construction organization and management can completely control the occurrence of concrete temperature cracks and construction cracks, and achieve good self-waterproofing and impermeability effects; Strengthening management and seriously implementing technical measures can effectively control the surface smoothness and flatness of the once-molded emery floor and meet the use requirements of the factory building. There were many doctoral and master's theses in previous years, so it is not convenient for me to publish privacy issues. ) I gave britney spears more. . . . . . . . . . . . . . . . . . . Thank you. Remember to give more.