Anti-crack fiber is a new concrete and mortar type compounded with polypropylene and polyester as the primary raw materials. It is called the “secondary reinforcement” of concrete. With the development of composite materials, anti-crack fibers have been widely used in civil engineering.
Studies have shown that adding crack-resistant fibers with a volume ratio of 0.05% to 0.2% to cement mortar and concrete can produce noticeable effects of crack resistance, toughening, shock resistance, impermeability, freeze-thaw resistance, and fatigue resistance. These excellent properties are essential in the crack resistance, toughening, and impermeability of dry-mixed plastering mortar, interior and exterior wall putty, and caulking agent. Crack-resistant fibers are widely used in road and bridge engineering, concrete expressway, and tunnel engineering.
Properties of crack-resistant fibers
(1) High tensile strength;
(2) Good aging resistance;
(3) Strong acid and alkali resistance;
(4) Crack resistance, toughening, shock resistance, impermeability, freeze-thaw resistance;
(5) Light specific gravity, less dosage, good dispersion;
(6) Low cost.
2.Range of application
There are many types of anti-crack fiber suitable for dry-mixed mortar, mainly including thermal insulation mortar, anti-crack plaster mortar, interior and exterior wall putty, waterproof mortar, caulking putty for gypsum board and lightweight concrete board, and cement-gypsum-based plaster mortar, suitable for the application of cement mortar or concrete, and the application fields include road bridges, dams, expressways, culverts, and subway projects.
3. Technical description
(1) Reduce and eliminate cracks
(2) Improve the impermeability of cement mortar and concrete
(3) Improve the shock resistance of cement mortar and concrete
(4) Improve the freeze-thaw resistance of cement mortar and concrete
Natural lignin fiber
Natural lignin fiber is one of the essential additives in dry-mixed mortar products. Natural lignin fiber and methyl cellulose ether are two completely different products in practical application. Lignin fiber is a natural fiber that is insoluble in water and obtained from beech and fir wood through pickling and neutralization, and then crushed, bleached, rolled, and sieved to get products of different lengths and finenesses. It is fundamentally different from dissolved methyl cellulose ether. Although some functions of lignin fiber, such as thickening and water retention, are similar to methyl cellulose ether, its thickening and water retention effects are far lower, and it cannot be used alone as a thickener and water retaining agent. The most prominent feature of lignin fiber is its flexibility and unique three-dimensional network structure. These characteristics determine that lignin fiber plays a role in reinforcement, crack resistance, and sag resistance in the dry-mixed mortar system rather than increasing thickening and water retention. The raw material for producing methyl cellulose ether is also wood fiber or short cotton fiber, but its production process differs significantly from lignin fiber. Therefore, the prices are also different. In practical applications, the main functions of methyl cellulose ether are water retention and thickening, so users should pay attention to distinguish the purposes of the two when using them.
2. Basic properties of lignin fiber
Lignin fiber is widely used in dry-mixed mortar, such as the production of tile adhesives, pointing agents, dry powder coatings, interior and exterior wall putty, interface agents, thermal insulation mortars, anti-crack plastering mortars, waterproof mortars, and plastering gypsum. Since lignin fiber is naturally insoluble in water and organic solvents, it has excellent flexibility and dispersibility. Adding an appropriate amount of lignin fibers of different lengths to the dry-mixed mortar product can enhance the shrinkage and crack resistance, improve the thixotropy and sag resistance of the product, prolong the available time, and play a specific thickening effect.
Lignin fibers with different lengths ranging from 10 to 2 000 μm tend to have a “carpet-like” effect after curing. With various lengths, they are used in other dry-mixed mortar products. Since the lignin fiber product is nontoxic and harmless, it is also used as a substitute for asbestos products, and the addition is only 30% to 50% of the standard complement of asbestos. In addition, lignin fiber also has specific high-temperature resistance, acid and alkali resistance, and frost resistance, so it is widely used.
