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CN-121990797-A - High crack resistant concrete

CN121990797ACN 121990797 ACN121990797 ACN 121990797ACN-121990797-A

Abstract

The invention discloses high-crack-resistance concrete, which relates to the technical field of building materials and comprises the following raw materials in parts by mass: portland cement: 350-450 parts of fly ash: 80-120 parts of granulated blast furnace slag powder: 60-100 parts of fine aggregate: 650-750 parts of coarse aggregate: 950-1100 parts of mixing water: 140-165 parts of high-performance polycarboxylate water reducer: 4.5 to 8.0 portions of anti-cracking synergistic toughening modifier: 15-35 parts of anti-cracking synergistic toughening modifier is formed by mixing a first component, a second component and a third component, and the anti-cracking synergistic toughening modifier endows basalt fiber with extremely strong surface chemical reactivity through double bionic-chemical co-modification of dopamine and a silane coupling agent, so that the basalt fiber is firmly riveted in a concrete gel network directly through a chemical covalent bond in the cement strong alkaline hydration process, and has more excellent and durable pull-out resistance and tensile strain bearing capacity than conventional carbon fiber.

Inventors

  • ZHU SHULE

Assignees

  • 滁州市中凯新型建材有限公司

Dates

Publication Date
20260508
Application Date
20260311

Claims (9)

  1. 1. The high-crack-resistance concrete is characterized by comprising the following raw materials in parts by mass: 350-450 parts of silicate cement; 80-120 parts of fly ash; 60-100 parts of granulated blast furnace slag powder; 650-750 parts of fine aggregate; 950-1100 parts of coarse aggregate; 140-165 parts of mixing water; 4.5-8.0 parts of high-performance polycarboxylate water reducer; 15-35 parts of anti-cracking synergistic toughening modifier; The anti-cracking synergistic toughening modifier is formed by mixing a first component, a second component and a third component; The first component is dopamine/silane co-grafted modified basalt fiber, the second component is a core-shell structure phase-change microcapsule taking n-octadecane as a core and silicon dioxide as a shell, and the third component is a salt-resistant internal maintenance water-absorbing microsphere prepared by ternary polymerization of acrylic acid, acrylamide and hydroxyethyl methacrylate; The mass ratio of the first component, the second component and the third component in the anti-cracking synergistic toughening modifier is (2-5)/(8-15)/(5-15).
  2. 2. The high crack resistant concrete according to claim 1, wherein the method of preparing the first component comprises the steps of: Cutting and ultrasonic cleaning are carried out on the basalt coarse fiber to remove the surface sizing agent, and the pretreated basalt fiber is obtained after drying; Soaking the pretreated basalt fiber in hydrochloric acid solution for water bath reflux etching treatment, and washing and drying to obtain basalt fiber with activated surface hydroxyl; adding the basalt fiber with the activated surface hydroxyl into Tris buffer solution containing dopamine hydrochloride, stirring for reaction under the conditions of light shielding and constant temperature, and performing self-oxidative polymerization on the dopamine to form a polydopamine coating which is coated on the surface of the fiber, and washing and drying to obtain polydopamine-coated basalt fiber; Dispersing the polydopamine coated basalt fiber into absolute ethyl alcohol containing 3-aminopropyl triethoxysilane hydrolysate, stirring at constant temperature for reflux reaction, carrying out Michael addition reaction and Schiff base reaction on phenolic hydroxyl and quinolyl structures on the surface of the polydopamine coating and 3-aminopropyl triethoxysilane, grafting silanol groups on the polydopamine modified layer, and washing and drying to obtain the first component.
  3. 3. The high crack resistant concrete according to claim 2, wherein the cut length of the basalt coarse fiber is 12-18 mm; The ultrasonic cleaning is carried out by adopting an ethanol water solution with the volume concentration of 70% -80%, the ultrasonic frequency is 40-50 kHz, and the cleaning time is 30-45 minutes; the concentration of the hydrochloric acid solution is 2-3 mol/L, the etching temperature is 60-70 ℃, and the etching time is 2-3 hours; The concentration of the Tris buffer solution is 10-20 mmol/L, the pH value is 8.4-8.6, the concentration of dopamine hydrochloride in the Tris buffer solution is 2-4 g/L, the reaction temperature is 25 ℃, and the reaction time is 18-24 hours; The volume concentration of the 3-aminopropyl triethoxy silane in the 3-aminopropyl triethoxy silane hydrolysate is 5% -10%, the reflux reaction temperature is 50% -60 ℃, and the reaction time is 6-8 hours.
  4. 4. The high crack resistant concrete of claim 1, wherein the second component is prepared by a sol-gel in situ coating method comprising the steps of: Mixing cetyl trimethyl ammonium bromide and octyl phenyl polyoxyethylene ether according to a molar ratio of 1:1, and dissolving the mixture in deionized water to prepare a compound surfactant aqueous solution with a mass concentration of 1.5% -2.5%; heating the composite surfactant aqueous solution to 45-50 ℃, adding n-octadecane in a molten state, and performing high-shear homogenizing emulsification for 20-30 minutes at a rotating speed of 10000-15000 r/min to form oil-in-water type phase-change core material microemulsion, wherein the particle size of n-octadecane liquid drops is controlled to be 1-3 microns; Reducing the stirring rotation speed to 400-600 r/min, regulating the temperature of a reaction system to 35-40 ℃, adding ammonia water solution with mass fraction of 5% to regulate the pH value of the system to 9.5-10.5, dropwise adding a mixed solution of ethyl orthosilicate and absolute ethyl alcohol into the system at the speed of 0.5-1.0 mL/min, wherein the volume ratio of the ethyl orthosilicate to the absolute ethyl alcohol is 1:1, continuing to stir at constant temperature for reaction for 12-16 hours after the dropwise addition, and hydrolyzing and polycondensing the ethyl orthosilicate at the interface of n-octadecane micro-oil drops and water to form a silicon dioxide shell; And (3) centrifugally separating, washing, vacuum freeze-drying the product, grinding and sieving the product with a 200-mesh sieve to obtain the second component.
  5. 5. The high crack resistant concrete according to claim 1, wherein the third component is prepared by an inverse suspension polymerization method comprising the steps of: The preparation of a water phase, namely placing acrylic acid into an ice water bath, dropwise adding a sodium hydroxide aqueous solution with the mass concentration of 30% for partial neutralization, controlling the neutralization degree to be 65% -75%, adding acrylamide accounting for 20% -30% of the mass of the acrylic acid and hydroxyethyl methacrylate accounting for 10% -15% of the mass of the acrylic acid, adding N, N' -methylene bisacrylamide accounting for 0.2% -0.4% of the total mass of the monomers as a cross-linking agent and potassium persulfate accounting for 0.5% -1.0% of the total mass of the monomers as an initiator after dissolving, and carrying out ultrasonic exhaust to obtain the water phase solution; preparing an oil phase, namely taking cyclohexane as a continuous phase solvent, adding sorbitan monostearate accounting for 2-4% of the mass of the cyclohexane as a dispersion protective agent, heating and dissolving, and then introducing nitrogen to remove dissolved oxygen to obtain an oil phase solution; Dropwise adding the aqueous phase solution into the oil phase solution under the conditions of continuous nitrogen protection and 300-400 revolutions per minute mechanical stirring, heating to 65-70 ℃ at the heating rate of 2 ℃ per minute, and reacting for 4-6 hours at constant temperature; and after the reaction is finished, heating to 75-85 ℃ to carry out azeotropic dehydration and solvent removal, collecting polymer microspheres, extracting and washing with acetone, drying to constant weight under the vacuum condition of 60 ℃, and screening out powder with the particle size of 100-200 microns to obtain the third component.
  6. 6. The high crack resistant concrete of claim 1, wherein the core-shell phase change microcapsules have a peak phase change temperature of 27.5-28.5 ℃ and a latent heat of phase change of 120-140 j/g.
  7. 7. The high-crack-resistance concrete according to claim 1, wherein the absorption rate of the salt-resistant internal curing water-absorbing microspheres in the cement simulated pore solution is 35-50 times.
  8. 8. The high crack resistant concrete according to claim 1, wherein the portland cement is a portland cement of grade p.o42.5 and above; The fly ash is I-grade fly ash conforming to GB/T1596-2017; the granulated blast furnace slag powder is S95 grade slag powder and above grade slag powder; the fineness modulus of the fine aggregate is 2.6-3.0, and the mud content is controlled within 1.0%; The coarse aggregate is continuous graded broken stone with the particle size of 5-20 mm, and the crushing index value is not more than 8%; the solid content of the high-performance polycarboxylate water reducer is not less than 40%, and the water reducing rate is more than 25%.
  9. 9. The high crack resistant concrete according to any one of claims 1 to 8, wherein the method of preparing the high crack resistant concrete comprises the steps of: Adding the fine aggregate, the coarse aggregate and the anti-cracking synergistic toughening modifier into a stirrer for dry mixing; Adding silicate cement, fly ash and granulated blast furnace slag powder into a stirrer, and continuously dry-mixing; and dissolving the high-performance polycarboxylate water reducer into mixing water, and adding the mixing water into a stirrer to perform wet forced stirring to obtain the high-crack-resistance concrete mixture.

Description

High crack resistant concrete Technical Field The invention relates to the technical field of building materials, in particular to high-crack-resistance concrete. Background As modern construction engineering develops towards ultra-high-rise, large-span, ultra-deep underground space, large-volume structure, severe marine environment and other complex structures, increasingly stringent requirements are put forward on the mechanical properties, volume stability and long-term durability of concrete materials, in practical engineering application, high-performance concrete or ultra-high-performance concrete generally needs to use extremely low water-gel ratio (usually lower than 0.30) and extremely high gel material dosage, however, the design of the mix ratio necessarily results in remarkable self-shrinkage, chemical shrinkage and severe hydration heat rise of the concrete in the hydration hardening process, the self-shrinkage and the temperature shrinkage generate huge tensile stress in the concrete when being constrained by steel bars, templates or existing structures and the like, once the tensile stress exceeds the early tensile strength of the concrete, microscopic microcracks are generated in the concrete, and the concrete is rapidly expanded into macroscopic penetrability or non-penetrability cracks, the existence of the microcracks seriously weakens the whole mechanical bearing capacity and the integrity of the building structures, and rapidly invaded corrosive media such as moisture, chloride ions, sulfate ions and carbon dioxide are provided, the rapid invasion of corrosive media is rapidly provided, and the corrosion media such as the concrete has extremely accelerated, the cost and the chemical corrosion of the concrete is greatly invaded in the service life is greatly reduced, and the hidden danger of the steel bar structures is greatly reduced, and the service cost is greatly shortened, and the service cost is greatly prolonged. Aiming at the serious cracking problem of concrete under a high cementing material system, the prior art usually adopts a single-dimensional control method of adding physical cracking resistant fibers (such as steel fibers, polypropylene fibers, common carbon fibers and the like) or adding chemical expansion agents (such as calcium oxide expansion agents, calcium sulfoaluminate expansion agents), shrinkage reducing agents and the like to relieve. For example, a Chinese invention patent document CN115959870A discloses an anti-cracking low-carbon high-performance concrete and a preparation method thereof, and the comparative document discloses that each raw material and the dosage thereof comprise 390-410 kg/m3 of LC3 cementing material, 640-660 kg/m3 of sand, 1000-1100 kg/m3 of stone, 150-170 kg/m3 of water, 8.0-8.5 kg/m3 of water reducer, 0.1-0.3 kg/m3 of activated carbon fiber and 0.1-0.3 kg/m3 of graphene oxide; Wherein the LC3 cementing material mainly comprises cement, calcined clay, limestone powder and gypsum; The water is formed by mixing waste water and clear water of a mixing station, and the prior art is expected to exert the bridging crack resistance effect of the carbon fiber and the micro-filling and hydration promotion effect of the graphene oxide to improve the crack resistance of the cement-based material by introducing activated carbon fiber and the graphene oxide. However, as can be seen from the deep analysis, the above-mentioned prior art documents still have the following technical drawbacks, which are not neglected: firstly, the carbon fiber has extremely high axial tensile strength and elastic modulus, but the surface is typical chemical inert, even though the conventional acid liquid electric activation treatment is carried out in the comparative literature, in the high alkaline cement hydration liquid environment, the interfacial chemical bonding force between the carbon fiber and cement hydration products (such as hydrated calcium silicate gel and C-S-H) is still extremely limited, under the dry-wet alternate action of complex temperature alternation and environmental humidity fluctuation along with the growth of age, the interface between the carbon fiber and a matrix is extremely easy to generate microscopic slip and debonding, so that the long-term bridging crack resistance effect is greatly attenuated, secondly, the graphene oxide has extremely high specific surface area, but in the actual mixing process of the large-volume ready mixed concrete, the graphene oxide is extremely easy to generate irreversible severe agglomeration in a strong alkaline pore solution due to the strong van der waals attraction, pi stacking action and double-layer compression caused by high calcium ion concentration, the agglomeration is not only unable to effectively fill the effect of pores, but also can not generate natural shrinkage stress formed in the concrete matrix under the dry-wet alternate action, the crack resistance effect is extremely low, the problem o