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CN-121974630-A - Expansion agent-fiber synergistic anti-cracking cement stabilized macadam and preparation method thereof

CN121974630ACN 121974630 ACN121974630 ACN 121974630ACN-121974630-A

Abstract

The invention discloses an expanding agent-fiber synergistic anti-cracking cement stabilized macadam and a preparation method thereof, and belongs to the technical field of road engineering materials, wherein the cement stabilized macadam comprises macadam aggregates, cement, a composite expanding agent and modified bamboo fibers; the composite expanding agent is prepared by compounding a calcium oxide-based expanding component and a calcium sulfoaluminate-based expanding component according to the mass ratio of 1 (1.8-2.2), treating modified bamboo fibers by alkali liquor and impregnating by nano silica sol, and adding wet modified fiber suspension into a stirrer under a continuous stirring state.

Inventors

  • DENG CHANGQING
  • ZHANG YU
  • YI YONG
  • ZOU HONG

Assignees

  • 邵阳学院

Dates

Publication Date
20260505
Application Date
20260204

Claims (9)

  1. 1. The expansion agent-fiber synergistic anti-cracking cement stabilized macadam is characterized by comprising the following components of macadam aggregate, cement, a composite expansion agent and modified bamboo fibers, wherein the composite expansion agent is formed by compounding (1.8-2.2) of a calcium oxide-based expansion component and a calcium sulfoaluminate-based expansion component according to the mass ratio of 1, the mixing amount of the composite expansion agent is 8-10% of the mass of the cement, the modified bamboo fibers are bamboo pulp fibers subjected to alkali liquid treatment and nano silica sol impregnation treatment, and the mixing amount of the modified bamboo fibers is 0.15-0.25% of the mass of the cement.
  2. 2. The expander-fiber synergistic crack resistant cement stabilized macadam of claim 1, wherein the calcium oxide based expansion component has a free calcium oxide content of 75% to 85% and a specific surface area of 280 to 350 The anhydrous calcium sulfoaluminate content of the calcium sulfoaluminate-based expansion component is 55-65%, and the specific surface area is 350-420 /kg。
  3. 3. The expander-fiber synergistic crack resistant cement stabilized macadam of claim 1, wherein the modified bamboo fiber has a diameter of 35-45 μm, a length of 10-14 mm, and a tensile strength of 450-550 MPa.
  4. 4. The swelling agent-fiber synergistic crack-resistant cement stabilized macadam according to claim 1, wherein the alkali liquor treatment adopts a sodium hydroxide solution with the mass concentration of 4% -8%, the treatment temperature is 50-70 ℃, the treatment time is 2-4 h, the solid content of the nano silica sol is 25% -35%, the particle size is 15-30 nm, and the dipping time is 1-2 h.
  5. 5. The expander-fiber synergistic crack resistant cement stabilized macadam of any one of claims 1 to 4, having a free expansion ratio of 0.03% to 0.05%, an unconfined compressive strength of 4.5 to 6.0 mpa for 28 days, and a dry shrinkage factor of 35 to 55 x for 28 days /°C。
  6. 6. The method for preparing the expansive agent-fiber synergistic crack-resistant cement stabilized macadam as claimed in any one of claims 1 to 5, comprising the steps of: Step 1, bamboo fiber modification treatment, namely placing bamboo pulp fibers in a sodium hydroxide solution with the mass concentration of 4% -8%, treating 2-4 h at 50-70 ℃, washing to be neutral, and draining; Step 2, premixing a composite expanding agent, namely uniformly mixing a calcium oxide-based expanding component and a calcium sulfoaluminate-based expanding component according to the mass ratio of 1 (1.8-2.2), and then dry-mixing the mixture with cement according to the mass mixing amount of 8-10%, wherein the stirring time is 2-3 min, so as to obtain an expansion type cementing material; step 3, preprocessing aggregate, namely adding water into crushed stone aggregate to wet the crushed stone aggregate to a saturated surface dry state, wherein the water content is controlled to be 95% -105% of the water absorption of the aggregate; step 4, preparing fiber suspension, namely dispersing wet modified bamboo fibers in water to prepare suspension, wherein the mass ratio of the fibers to the water is 1 (80-120), and fully dispersing the fibers by adopting mechanical stirring; Step 5, mixing the mixture, namely firstly mixing the expansion type cementing material obtained in the step 2 with the pre-wet aggregate obtained in the step 3 for 1-2 min, then uniformly adding the fiber suspension obtained in the step4 into a mixer under a continuous stirring state, continuously mixing for 2-3 min, adding the rest of mixing water, and mixing until the mixture is uniform; and 6, molding and curing, namely paving and rolling the mixture, and standard curing or coverage curing for 7-28 days.
  7. 7. The method of claim 6, wherein the fiber suspension in step 4 is maintained under continuous agitation prior to addition to the mixer to prevent fiber segregation.
  8. 8. The method according to claim 6, wherein the compacting in step 6 is vibration compacting, the compactness is not lower than 98%, and the geotextile or plastic film is covered in 2h after compacting for moisture maintenance.
  9. 9. The preparation method according to claim 6, wherein the cement is ordinary portland cement or composite portland cement, the strength grade is 42.5 or 52.5, and the mixing amount of the cement is 4% -6% of the mass of the crushed stone aggregate.

Description

Expansion agent-fiber synergistic anti-cracking cement stabilized macadam and preparation method thereof Technical Field The invention belongs to the technical field of road engineering materials, and particularly relates to an expanding agent-fiber synergistic anti-cracking cement stabilized macadam and a preparation method thereof. Background The cement stabilized macadam is widely applied to highway construction in China as a semi-rigid base material, and has the advantages of high strength, good integrity, strong anti-scouring capability, relatively low manufacturing cost and the like. However, cement stabilized macadam base has common shrinkage cracking problems, mainly manifested by dry shrinkage cracks and temperature shrinkage cracks. These cracks gradually reflect upward and extend to the surface layer, forming reflective cracks, severely affecting the service performance and service life of the pavement. Aiming at the shrinkage cracking problem of cement stabilized macadam, researchers at home and abroad develop a great deal of research work. In the aspect of fiber reinforcement technology, polyvinyl alcohol fibers, polypropylene fibers, basalt fibers and the like are introduced into cement stabilized macadam, and crack propagation is inhibited through bridging action of the fibers. The research shows that the optimal doping amount of the polyvinyl alcohol fiber is 0.6-1.2 kg-When the optimal length is 12-30 mm, the cracking resistance index of the cement stabilized macadam can be improved by 44.4 percent. Basalt fiber mixing amount exceeds 6 kg +.In this case, the anti-shrinkage performance and the crack resistance under temperature cycle can be effectively improved. However, the single fiber reinforcement has limited effect of inhibiting shrinkage deformation, and the problem of shrinkage stress accumulation cannot be fundamentally solved. In the expansion agent shrinkage compensation technology, calcium sulfoaluminate expansion agents are receiving attention due to their expansion characteristics and lower carbon emission characteristics. Main mineral phase of calcium sulfoaluminate expanding agent is anhydrous calcium sulfoaluminate) Rapid hydration in the presence of gypsum to form ettringite) Expansion-compensated contraction is generated. The research shows that when calcium sulfoaluminate and magnesium oxide expanding agent are compounded according to the mass ratio of 2:1, the cracking resistance of the concrete can be improved by 97-127%. However, the expansion time course of the conventional composite expansion agent is difficult to be precisely matched with the shrinkage development process, and the problems of over-expansion in the early stage or under-expansion in the later stage exist. Natural plant fibers have received attention in recent years as an environmentally friendly reinforcing material. The bamboo fiber has the advantages of wide sources, reproducibility, low carbon footprint and the like, and the tensile strength of the bamboo fiber can reach 400-600 MPa, which is equivalent to that of certain synthetic fibers. However, the application of the bamboo fiber in the cement-based material faces two major challenges, namely that the surface of the natural fiber is provided with substances such as wax, pectin and the like, so that the interface bonding strength of the fiber and a cement matrix is low, and the natural fiber is easy to degrade in an alkaline environment and has insufficient durability. The prior researches mainly adopt alkali treatment or silane coupling agent treatment to improve the interface combination of the fiber and the matrix, but have limited alkali resistance improvement effect on the fiber. In summary, in the prior art, the effect of single fiber reinforcement on inhibiting shrinkage deformation is limited, the expansion time course of the traditional expanding agent is not matched with shrinkage development, the problems of insufficient alkali resistance and interface bonding strength of natural fibers and the like are solved, and the further improvement of the cracking resistance of the cement stabilized macadam foundation is restricted. Therefore, the development of the crack-resistant cement stabilized macadam with the synergistic effect of the expanding agent and the modified natural fiber has important engineering application value. Disclosure of Invention Aiming at the problems that the temperature shrinkage and dry shrinkage cracks of a cement stabilized macadam base layer are generally developed, the shrinkage deformation inhibition effect of single fiber reinforcement is limited, the durability of natural fibers in an alkaline environment is insufficient and the like in the prior art, the invention provides the expansion agent-fiber synergistic anti-cracking cement stabilized macadam and a preparation method thereof. The invention realizes the effective inhibition of the shrinkage deformation of the cement stabilized macadam and the remarkabl