Search

CN-122010480-A - Solid waste base low-carbon concrete and preparation method thereof

CN122010480ACN 122010480 ACN122010480 ACN 122010480ACN-122010480-A

Abstract

The invention discloses solid waste base low-carbon concrete and a preparation method thereof, and belongs to the field of environment-friendly concrete. The problems of low mixing amount, poor performance, poor process suitability and the like of the traditional solid waste concrete are solved by a compound excitant preactivation technology, a solid waste multistage grinding process and a gradient stirring process. The slag powder, the fly ash, the waste limestone powder and the superfine tunnel slag powder are taken as the admixture (the total admixture is more than or equal to 40 percent), and the compound excitant with adjustable modulus is combined, so that the reactivity of solid waste and the interface bonding strength are obviously improved. The strength of the concrete is more than or equal to 55MPa after pretreatment and staged stirring, the impermeability level reaches P12, the carbon emission is reduced by 38%, and the concrete is suitable for high-durability engineering such as tunnel lining, prefabricated parts and the like, and realizes the recycling and high-value utilization of solid wastes.

Inventors

  • MA CHAO
  • ZHANG LEI
  • LI FUJUN
  • PANG YU
  • Ba Yacui
  • ZHANG CHUNLEI
  • MING YANG
  • TAN BO
  • LI LING

Assignees

  • 中交路桥建设有限公司
  • 中交路桥南方工程有限公司
  • 桂林理工大学

Dates

Publication Date
20260512
Application Date
20251231

Claims (10)

  1. 1. The solid waste base low-carbon concrete is characterized by comprising the following raw materials in parts by weight: 200-240 parts of cement and the following components, 160-200 Parts of solid waste admixture, 600-750 Parts of fine aggregate, 900-1100 Parts of coarse aggregate, 8-15 Parts of a compound excitant, 2-4 Parts of water reducer, 140-160 Parts of water; The solid waste admixture is formed by compounding slag powder, fly ash, waste limestone powder and tunnel slag powder according to the mass ratio of (30-45): (25-35): (15-25): (10-20); Wherein, the slag powder contains more than or equal to 35 weight percent of CaO, more than or equal to 30 weight percent of SiO 2 and more than or equal to 85 percent of vitreous body; The coal ash has the ignition loss less than or equal to 5 percent, the SiO 2 +Al 2 O 3 is more than or equal to 70 percent, and the fineness (45 mu m screen residue) is less than or equal to 12 percent; Waste limestone powder, caCO 3 is more than or equal to 90%, D50=5-15 μm; The tunnel slag powder contains more than or equal to 15% of SiO 2 ≥40％、Al2O 3 and more than or equal to 75% of activity index.
  2. 2. The solid waste-based low-carbon concrete according to claim 1, wherein the tunnel slag powder is prepared by adopting a three-stage grinding process, wherein the primary grinding process comprises the steps of crushing to a particle size of <5mm, the secondary ball milling process comprises the steps of grinding to a specific surface area of 300-400m 2 /kg, and the three-stage superfine grinding process comprises the step of grinding to a specific surface area of 500-600m 2 /kg.
  3. 3. The solid waste-based low-carbon concrete according to claim 1, wherein the composite activator consists of sodium water glass with a water glass modulus of 1.2-1.8, sodium hydroxide, sodium sulfate and nano silica fume according to a mass ratio of 5:2:2:1.
  4. 4. The solid waste-based low-carbon concrete according to claim 3, wherein the nano silica fume is hydrophobic nano silica fume subjected to surface modification, the specific surface area is more than or equal to 20000m 2 /kg, and the surface contact angle is more than or equal to 120 °.
  5. 5. The method for preparing the solid waste-based low-carbon concrete according to any one of claims 1 to 4, comprising: (1) The solid waste pretreatment, namely grinding tunnel slag to a specific surface area of 500-600m 2 /kg through three stages, grinding slag to a specific surface area of 450-550m 2 /kg, and mixing the ground slag with fly ash and waste limestone powder to obtain a solid waste admixture; (2) Pre-activating the exciting agent, namely mixing 30-40% of the total amount of the composite exciting agent with the solid waste admixture in a high-speed mixer for 5-8min to obtain a pre-treated solid waste admixture; (3) Mixing the concrete, namely dry-mixing the cement, the pretreated solid waste admixture, the coarse aggregate and the fine aggregate for 30-60s according to the proportion, and adding the rest excitant, the water reducer and the water to wet-mix for 90-120s to obtain the solid waste-based low-carbon concrete.
  6. 6. The preparation method of claim 5, wherein 0.5-1.5% of grinding aid is added during grinding tunnel slag in the step (1), and the grinding aid is prepared by compounding triethanolamine with a polycarboxylic acid dispersant according to the proportion of 1 (2-3).
  7. 7. The method according to claim 5, wherein the temperature of the materials is controlled to be less than or equal to 45 ℃ in the mixing process in the step (2), and nitrogen protection is adopted.
  8. 8. The method according to claim 5, wherein the wet mixing in the step (3) is performed in three stages, low-speed stirring (30-50 rpm) for 30s, medium-speed stirring (80-100 rpm) for 45s, and high-speed stirring (120-150 rpm) for 15s.
  9. 9. The use of the solid waste-based low carbon concrete according to any one of claims 1 to 4 in tunnel lining engineering.
  10. 10. Use of the solid waste-based low carbon concrete according to any one of claims 1 to 4 in prefabricated parts.

Description

Solid waste base low-carbon concrete and preparation method thereof Technical Field The invention belongs to the field of environment-friendly concrete, and particularly discloses solid waste base low-carbon concrete and a preparation method thereof. Background In recent years, the concrete industry is faced with double pressure of reducing carbon emission and improving the recycling utilization of solid waste, and the preparation of low-carbon concrete by replacing cement with industrial solid waste represented by slag and fly ash has become an important research direction. However, the prior art system still has significant technical bottlenecks in material design, process adaptation and engineering application, and is mainly represented by the following core problems: 1. inversion contradiction of solid waste mixing amount and performance Traditional solid waste concrete is limited by low reactivity of solid waste materials, and the mixing amount is usually controlled below 30% to ensure strength development. For example, when slag powder is directly mixed, the glass body is difficult to depolymerize, the activity utilization rate is less than 50% in 28 days, and the early hydration inertia of the fly ash leads to the prolonging of the concrete form removing time by more than 40%. The prior art relies on the cement consumption to compensate the strength loss, so that the actual solid waste substitution rate is difficult to break through, and the real low-carbon target cannot be realized. Experimental research shows that when the solid waste mixing amount exceeds 35%, the dissolution efficiency of the traditional alkaline excitant (such as sodium hydroxide) on the silicon-aluminum phase is drastically reduced, unreacted solid waste particles in a gelling system form a weak interface area, and the impermeability and durability of the concrete are remarkably reduced. 2. Novel solid waste utilization technology blank The waste rock and soil of tunnel slag and other engineering is complex in mineral composition (quartz phase accounts for 40% -60%) and deficient in active components, and the waste rock and soil is used as low-added-value aggregate (the mixing amount is less than 10%) in the prior art, so that high-value micropowder utilization cannot be realized. The hole slag powder (specific surface area is less than 400m 2/kg) prepared by the conventional mechanical grinding process mainly plays a role in filling micro aggregates in concrete, and the volcanic ash activity index is less than 60%, so that the workability loss and the looseness of an interface transition zone are easy to occur after the hole slag powder is mixed. In addition, clay minerals (such as montmorillonite) remained in the hole slag powder can adsorb water reducer molecules, so that the slump loss is increased by 30% -50% with time. 3. Out of control of performance caused by material fluctuation The chemical components of industrial solid wastes are affected by sources and obviously fluctuate, for example, the CaO content in slag can differ by 15% -20%, and the fluctuation of the loss on ignition of the fly ash reaches 3% -8%. The prior art lacks a limiting and compensating mechanism for key indexes of raw materials, so that the discrete coefficient of the concrete strength is as high as 12% -18% under the same proportion. Typical problems include low calcium slag (CaO < 30%) forming non-gelling products due to insufficient alkaline excitation, and high loss on ignition fly ash (> 5%) with unburned carbon adsorbing air entraining agent, causing abnormal fluctuation of air content (. + -. 2%), severely affecting freeze resistance. 4. Defect of suitability of process system The characteristics of slow hydration heat release, high viscosity and the like of the large-mixing amount solid waste concrete have fundamental conflicts with the traditional construction process. For example: The conventional vibrating frequency (5000-6000 times/min) can not effectively discharge bubbles formed by aggregation of micro powder, so that the porosity of a pouring body is increased by 1.5-2 times; Curing system, namely constant temperature steam curing (such as 80 ℃ C. And 8 h) to intensify the difference of solid waste and cement hydration rate, and to cause shrinkage stress concentration, and increase the density of surface microcracks by 300-400 strips/m 2; the stirring process is that the traditional one-time feeding mode causes uneven distribution of the exciting agent, the exciting blind area appears locally, and the difference of the solid waste particle reaction rate reaches 20% -30%. The defects cause that the existing solid waste concrete is difficult to meet the requirements of high-durability engineering (such as prefabricated members and underground structures), and the large-scale application of the existing solid waste concrete is severely restricted. Disclosure of Invention In order to solve the problems in the prior art, the invention di