Technical support: polypropylene fiber application in dry mortar
Mortar is the main construction materials. With economic growth, population growth, improve people's environmental protection requirements and achieve commercialization mortar construction developed to a certain level is an important symbol. Mortar commercialization mainly focused on targeted supply of ready-mixed mortar and stir bagged dry mortar mixing mortar that two forms. Use dry mortar has many advantages, but there are some performance deficiencies. Products such as mortar cracks easily make natural water infiltration reduces durability of buildings, low temperature flexibility mortar products, tensile strength, impact resistance and poor. To solve these problems, the incorporation of polypropylene fibers in the dry mortar can effectively prevent cracks dry mortar products, dry products to improve the toughness and impact resistance. The authors studied the polypropylene fiber dispersion in dry mortar, impact the addition of fiber products for dry mortar crack resistance, impact resistance and other properties.
First, the use of the advantages of dry mortar
Dry mortar is a composition by a variety of raw materials, according to a certain formula in the factory mixed with dry, add water at the site is just a mixture of mixing can be used. Dry mortar has been widely used in foreign countries, with the improvement in the domestic quality requirements of the building, to develop new building materials, green building materials have been incorporated into our development plans. Shanghai, Beijing and other cities, government departments have explicitly require the development and promotion of the use of mortar, dry mortar and therefore bound to be rapid development in China. Use dry mortar has many advantages: high 1) product quality. Depending on the application, such as mortar for masonry, plastering and floor, etc., on the product's resistance to shrinkage, the different requirements of the anti-crack, waterproof, thermal insulation properties, mortar need to follow a different recipe can be achieved through a rigorous preparation. In the actual construction, because of the quality of all raw materials, the right mix, mixing uniformity can not guarantee the quality of the mortar often cause instability. Specializing in the use of large-scale automated production line of dry mortar, reliable, stable, and can produce a variety of applications to meet the special needs of special dry mortar. 2) high production efficiency. Dry mortar production plant scale, annual output is usually around tens of tons, can have a variety of dry mortar products to meet market demand. Dry mortar but also conducive to the use of modern construction equipment application, reducing the duration of construction. 3) environmental pollution. Large-scale centralized production and use of premixed bag, ease of construction, transport and storage, large construction site to avoid the accumulation of raw materials and on-site mixed impact on the surrounding environment.
Second, the role of the mechanism of polypropylene fiber
However, there are some properties of dry mortar products defects, such as cracks in the mortar to make products easy to produce natural water infiltration reduces the durability of buildings, low temperature flexibility mortar products, tensile strength, impact resistance and poor. Use polypropylene fibers can well improve these properties, the mechanism of the fiber is: its good uniformity in the mortar to the three-dimensional chaotic step using polypropylene fiber good ductility, adhesion, stress transfer, absorption Because cement mortar to suppress energy syneresis (Shrinkage), cement hydration cause temperature difference (temperature shrinkage), micro-crack in the cement hydration process volume deformation (chemical shrinkage) and other factors, thereby enhancing the integrity of the mortar , flexibility, continuity, and crack resistance, impermeability, and tensile strength.
After the addition of fiber in the project, can significantly improve the performance of mortar cracking and wall insulation board wall insulation to improve the integrity of the system, can work together to ensure the insulation and the wall and effectively block thermal bridge, significantly improved mortar insulation board workability; especially for the outer insulation board mortar, adding fiber can improve the mortar surface resistant to temperature and humidity changes, the ability to wind and rain impact, increasing the overall stability of the external thermal insulation layer to overcome the external wall insulation Durability appears good, easy to produce shrinkage cracks, construction techniques and complex defects.
Polypropylene fiber properties
Fiber Type: bundle monofilament
Density: 0.91g / cm3
Melting point: 160 ~ 170 ℃
Acid alkaline: high
Specific surface area: 237m2 / kg
Flash point: 580 ℃
Surface mortar dedicated fiber "length of 3mm, 6mm, 12mm, typically mixing amount of 0.9kg / m3. The main application of external wall insulation board insulation system in the outer surface mortar.
Third, the experimental study of polypropylene fiber in dry mortar
3.1 Test
3.1.1 raw materials
The main dry plaster wall insulation materials include: P.032.5 cement, specific surface area: 4000cm2 / g; after washed river sand, the particle size of 60 mesh; polymer additives and fine powder filler polypropylene fibers.
3.1.2 Test
3.1.2.1 fiber dispersion
Test will be added to the polymer polypropylene fiber dry mortar, by actual production test equipment, testing its dispersion in dry mortar. A continuous rotary mixer, stirring speed 100 ~ 200r / min, the effective volume of 1600L, the real effective filling rate of 70%, plus additional stirring.
1) Experimental Design
① The polypropylene fibers are added Tangshan DUNSHI powder produced by artificial feeding mixing equipment, the use of its high-speed stirring dispersing performance fibers, the stirrer is stopped after the doors open with a stirrer, a stirrer in the interior of different heights, different locations total Take 10 samples.
② in production equipment at the bottom of the packaging machine to take a mixed sample.
③ on the samples were taken above the dispersibility test.
2) test ideas
Polypropylene fiber is a small diameter, but the length of the longer true linear material, due to its own structural features, in the course of screening with fine powder does not fall into the lower sieve, and the portion of the crude Under the conditions of the presence of particles in constant shaking, put the process will reunite with each other to form a relatively complete aggregates. We decided to take advantage of this feature by two graded mesh sieve to obtain again after dispersion fiber aggregates.
3.1.2.2 Performance dry mortar products
Crack resistance
DBJ 01-63-2002 experimental basis in crack detection "exterior insulation quality inspection standard for polymer mortar" approach. Taking into account the actual environmental factors, we took four options:
① under normal laboratory conditions (temperature of 22 ℃, relative humidity 50%)
② high-speed wind conditions (temperature of 22 ℃, 50% relative humidity, wind speed at 5m / s)
③ wind speed + light shine (temperature of 22 ℃, 50% relative humidity, wind speed at 5m / s, according to 500W light bulb)
④ In the actual natural environment (temperature of 35 ℃, relative humidity 40%, wind 2)
Impact resistance and other properties
Test based on detection methods JG149-2003 "expanded polystyrene board thin plaster exterior insulation system" in the relevant properties.
Fourth, the results of the discussions
4.1 polypropylene fiber in the dispersion of dry mortar
Stirrer 10 testing data samples (see below)
The number of test samples weighed sample amount (g) contains the amount of fiber (g)
1200 0.11
2200 0.10
3200 0.09
4200 0.09
5200 0.08
6200 0.10
7200 0.10
8200 0.10
9200 0.09
10200 0.11
It seems from the experimental data, reflects the higher polypropylene fiber dispersion, though the data fluctuate, which may be due to the screening process when the fibers reagglomeration wrapped part of the polymer additives, resulting in an unstable data . But the discovery by screening the fiber content ratio given us the added amount of the basic agreement. Description while stirring the fibers have good dispersibility.
Bags of dry mortar mix sample data
After packing machine for mixing samples that have been packed in bags of dry mortar sampling, screening, testing test result: dry mortar fiber content of 0.01g, the test results and the test results are consistent with a stirrer. This fully shows that the fiber through stirrer and packaged into a bag fibers and mortar after no separation phenomenon, its dispersion, good uniformity.
By assay above two parts, we can determine the polypropylene fibers have good dispersion in dry mortar.
4.2 crack resistance of polypropylene fibers mixed with dry mortar products
After more than four in the designed test conditions after the test to get under the conditions tested, adding polypropylene fiber exterior insulation surface mortar almost no cracks, without adding external insulation polypropylene fiber surface mortar, in addition to an external test conditions, In the other three conditions, the external insulation surface mortar are significant cracks and cracks up to in the natural environment (Condition 4) appears. The test results indicated adequate insulation hand dry mortar mixed with polypropylene fibers have significantly improved the performance of its products crack.
4.3 adding impact resistance of polypropylene fibers dry mortar products and other properties
Surface mortar test data (see table)
Pilot project test results
Contain no fiber fiber
Original strength 0.20 0.20
Water 0.15 0.16
Freeze-thaw resistance 0.21 0.22
Flexibility compressive / flexural strength wait 2.2
Operating time, h 3 3
V. Conclusion
Through experiments can be drawn polypropylene fibers have good dispersion in dry mortar. The addition of fiber, greatly improving the resistance to cracking, impact properties of materials, and no negative impact other properties of dry mortar products. By actual production equipment and engineering applications, adding polypropylene fiber has the ability to produce large-scale industrialization in the dry mortar. Polypropylene fibers can be significantly improved performance engineering cracking mortar and wall insulation panels, reducing brittleness and increase the toughness and improve the integrity of the external wall insulation system, can be expected in the dry mortar mixed with polypropylene will be in my foreign Wall insulation works play a great role.