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CN-121990794-A - Anti-cracking concrete and preparation method thereof

CN121990794ACN 121990794 ACN121990794 ACN 121990794ACN-121990794-A

Abstract

The invention discloses anti-cracking concrete and a preparation method thereof, and belongs to the technical field of concrete materials. The anti-cracking concrete is prepared from the following raw materials, by weight, 300-500 parts of cement, 900-1200 parts of coarse aggregate, 600-800 parts of fine aggregate, 15-40 parts of admixture, 3-10 parts of water reducer, 20-50 parts of composite fiber reinforcing agent, 10-20 parts of filler, 1-3 parts of internal curing agent and 140-180 parts of water. The composite fiber reinforcing agent is formed by compounding basalt fibers and modified cotton stalk fibers according to the mass ratio of 1 (4-6). The invention ensures that the obtained concrete has excellent cracking resistance and excellent durability while maintaining good construction workability through the triple effects of synergistic toughening of the composite fibers, microstructure compaction of the functional filler and continuous moisture retention of the internal curing agent, and realizes comprehensive improvement of the cracking resistance.

Inventors

  • WANG XINGWU
  • LI HOUYU
  • Ye longxiang
  • FAN ZHIRUI
  • WANG LILI
  • WEN MINDE

Assignees

  • 天元建设集团有限公司
  • 临沂天方建设研究试验有限公司

Dates

Publication Date
20260508
Application Date
20260130

Claims (10)

  1. 1. The anti-cracking concrete is characterized by being prepared from the following raw materials, by weight, 300-500 parts of cement, 900-1200 parts of coarse aggregate, 600-800 parts of fine aggregate, 15-40 parts of admixture, 3-10 parts of water reducer, 20-50 parts of composite fiber reinforcing agent, 10-20 parts of filler, 1-3 parts of internal curing agent and 140-180 parts of water, wherein the composite fiber reinforcing agent comprises basalt fiber and modified cotton stalk fiber according to a mass ratio of 1 (4-6).
  2. 2. The anti-crack concrete according to claim 1, wherein the modified cotton stalk fiber is prepared by the following method: (1) Cleaning the cleaned cotton stalks, drying and crushing the cotton stalks into small sections of 1-3cm, then placing the small sections into a high-speed crusher for crushing, sieving, and collecting fibers passing through a 20-mesh screen but trapped in a 60-mesh screen for later use; (2) Dissolving Ca (OH) 2 in deionized water, stirring uniformly to prepare Ca (OH) 2 solution with constant concentration, adding the cotton stalk fiber obtained in the step (1) into the solution according to the solid-to-liquid ratio, and stirring at the rotating speed of 500-600 r/min for reaction for 1-2h; (3) Transferring the cotton stalk fiber mixed system after alkali treatment into a high-pressure reaction kettle, sealing the reaction kettle, introducing carbon dioxide gas to reach a fixed pressure, regulating stirring speed, maintaining the pressure at normal temperature for reaction for 4-5 hours until the pH value of the reaction system reaches 6.5-7.0, taking out slurry after the reaction is finished, centrifugally washing the slurry for multiple times by deionized water until the supernatant is clear, and vacuum drying the cleaned solid product to obtain the modified cotton stalk fiber.
  3. 3. The anti-crack concrete according to claim 2, wherein the concentration of the Ca (OH) 2 solution in the step (2) is 0.8. 0.8 wt%.
  4. 4. The anti-crack concrete according to claim 2, wherein the solid-to-liquid ratio of the cotton stalk fiber to the Ca (OH) 2 solution in step (2) is 1 g:20 mL.
  5. 5. The anti-crack concrete according to claim 2, wherein the fixing pressure in the step (3) is 1.2MPa and the stirring speed is 400-500 r/min.
  6. 6. The anti-crack concrete according to claim 1, wherein the admixture is at least one of fly ash, slag powder and silica fume.
  7. 7. The anti-crack concrete according to claim 1, wherein the filler is composed of nano silicon dioxide and mica powder according to a mass ratio of 2:1.
  8. 8. The anti-crack concrete of claim 1, wherein the water reducer is a high efficiency polycarboxylate water reducer.
  9. 9. The anti-cracking concrete according to claim 1, wherein the internal curing agent is composed of sodium polyacrylate and vermiculite according to a mass ratio of 2:1.
  10. 10. A method for preparing the anti-crack concrete according to any one of claims 1 to 9, comprising the steps of: Step 1, preparing modified cotton stalk fiber by adopting the method of claims 2-4, and uniformly mixing the modified cotton stalk fiber and basalt fiber in a dry state according to a proportion to prepare a composite fiber reinforcing agent for later use; step 2, mixing sodium polyacrylate and vermiculite according to a mass ratio of 2:1 to form an internal curing agent, adding the internal curing agent into mixing water with the total mass being 40-60 times of that of the internal curing agent, standing for 20-40 minutes to fully absorb water and presaturate the internal curing agent to form a gel-like mixture; Step 3, putting cement, admixture, fine aggregate, coarse aggregate, filler and the composite fiber reinforcement agent prepared in the step 1 into a stirrer together, and dry-stirring at a rotating speed of 30-50 r/min for 60-120 seconds until the materials are uniformly mixed and the fibers are dispersed and free from agglomerations; Step 4, adding the pre-saturated gel-like internal curing agent prepared in the step 2 into a stirrer, and stirring at a rotating speed of 40-60 r/min for 60-90 seconds to uniformly disperse the pre-saturated gel-like internal curing agent in a concrete mixture; and 5, discharging the final mixture, pouring, mechanically vibrating and compacting, and curing to obtain the modified asphalt.

Description

Anti-cracking concrete and preparation method thereof Technical Field The invention relates to the technical field of concrete, in particular to anti-cracking concrete and a preparation method thereof. Background The concrete is used as an artificial building material with the largest dosage and the widest application in the current world, and is an indispensable structure and function carrier for various building engineering. However, since its birth, the problem of cracks is a serious problem that afflicts the engineering community. The cracks not only destroy the integrity and the aesthetic property of the structure, but also provide convenient channels for moisture, aggressive ions (such as chloride ions and sulfate ions) and oxygen, obviously accelerate corrosion of internal steel bars, carbonization and freeze thawing destruction of concrete, seriously weaken the bearing capacity, durability and service life of the structure, and even possibly cause catastrophic safety accidents, thereby causing huge economic loss and resource waste. Cracking of concrete is a complex physicochemical process, and the root of the cracking is attributable to the inherent brittleness of the material and the combined action of the external environment and load. From the inside of the material, the tensile stress is generated in the concrete by chemical shrinkage generated in the cement hydration process, thermal expansion and contraction caused by temperature change, drying shrinkage caused by water evaporation and sedimentation shrinkage in the plastic stage. When these tensile stresses exceed the tensile strength of the concrete at the time, cracks inevitably occur. From external factors, design loads, secondary stresses (such as uneven settlement, constraint deformation generation), early disturbances during construction (such as form deformation, improper maintenance), and long-term environmental effects (such as dry-wet cycles, freeze-thaw cycles) are all key external forces for inducing and expanding cracks. In order to inhibit and control concrete cracks, long-term and intensive researches are carried out in the fields of engineering technology and material science, and various traditional technical routes are developed, but certain limitations exist in 1) optimizing the mixing ratio and material selection, namely, shrinkage can be reduced to a certain extent, hydration heat can be reduced, and compactness and tensile strength can be improved by reducing the water-cement ratio, selecting low-heat or micro-expansion cement, adding high-quality mineral admixture (such as fly ash and slag powder) and optimizing aggregate grading. However, this method has limited improvement effect on cracks, particularly cracks caused by strong external restraint or severe temperature and humidity changes, often is difficult to completely avoid, and may adversely affect workability or early strength. 2) Fiber reinforcement technology, which is to blend chopped fibers (such as steel fibers, synthetic fibers, glass fibers, natural fibers) into concrete, is a widely used anti-cracking means. The fiber can bridge microcracks and prevent the microcracks from expanding, so that the toughness, the cracking resistance and the impact resistance of the concrete are improved. However, the technology has obvious short plates, the effect is not obvious when the blending amount of the fiber is too low, and the blending amount is too high, so that the fluidity of the mixture is easy to be rapidly reduced, the fiber is agglomerated, and the construction performance and the uniformity of the material are seriously affected. Some fibers (e.g., steel fibers) also present a risk of tarnishing, are costly, and can affect the surface treatment. In addition, fibers primarily control microscopic and microscopic cracks, with limited ability to inhibit macrostructural cracking. 3) The chemical additive mainly comprises an expanding agent and a shrinking agent. The expansion agent compensates for the partial shrinkage by generating a moderate volume expansion at the early stage of hardening of the concrete, but its expansion efficiency is greatly affected by curing conditions (particularly, moisture supply), and improper curing may cause insufficient expansion or an adverse delayed expansion at the later stage. The shrinkage reducing agent reduces the capillary stress by reducing the surface tension of the pore solution, thereby reducing the drying shrinkage, but its long term effectiveness, adaptability to different cement systems, and possibly the subtle effects on strength development remain of concern. The single use of chemical additives tends to be difficult to cope with complex, multifactorial coupled shrinkage stresses. 4) The design and construction measures comprise reasonable arrangement of expansion joints and post-pouring belts, reinforcement of reinforcing structures (such as a small-diameter closely-spaced reinforcing mesh), strict moisture and he