Method for preparing low-carbon porous lightweight aggregate by using construction recycled sand powder

Abstract

The present application belongs to the technical field of building waste resource utilization, and discloses a method for preparing low-carbon porous lightweight aggregate by using building recycled sand powder, which comprises the following steps: firstly, drying and primary screening the building sand powder, and then separating the raw material into recycled fine sand and recycled micro powder through multi-stage screening; mixing the recycled fine sand and recycled micro powder according to a proportion to form building recycled sand powder; then, adding geopolymer cementitious precursor into the building recycled sand powder to form a composite cementitious precursor; then, preparing an alkali activator; then, placing the composite cementitious precursor into a disc granulator for granulation treatment; spraying the plant protein foaming agent solution and the alkali activator simultaneously or alternately during the granulation rolling process, introducing air by mechanical shearing force, and preparing aggregate green body; and finally, curing the obtained aggregate green body at low temperature to obtain low-carbon porous lightweight aggregate. The present application is energy-saving and environment-friendly, realizes low-carbon production, has controllable performance, stable pore structure and excellent performance.

Claims

1. A method for preparing low-carbon porous lightweight aggregate using recycled construction sand powder, characterized in that: It includes the following steps: S1. Raw material pretreatment: First, the building sand powder is dried and initially screened; then, the raw material is separated into recycled fine sand and recycled micro powder through multi-stage screening; next, the recycled fine sand and recycled micro powder are remixed at a mass ratio of 0.2 to 1.5:1 to form recycled building sand powder. S2. Construction of composite cementitious precursor: Geopolymer cementitious precursor is added to the recycled building sand powder obtained in step S1 to form composite cementitious precursor. S3. Preparation of alkaline activator: The alkaline activator includes one or more of alkali metal silicates, alkali metal hydroxides, carbonates, sulfates, and aluminates; S4. Bio-based interface modification and granulation foaming: The composite gel precursor obtained in step S2 is placed in a disc granulator for granulation; during the granulation rolling process, a plant protein foaming agent solution and the alkali activator obtained in step S3 are sprayed simultaneously or alternately, and air is introduced by mechanical shearing force to prepare aggregate raw materials; the plant protein foaming agent is one or more of natural plant protein, modified plant protein, and plant-derived surfactants. S5. Curing: The raw aggregate obtained in step S4 is cured at low temperature to obtain low-carbon porous lightweight aggregate.

2. The method for preparing low-carbon porous lightweight aggregate using recycled building sand powder according to claim 1, characterized in that: It also includes one or more of the following features: (1) In step S2, the mass fraction of recycled building sand powder in the composite cementitious precursor is 70% to 95%; (2) In step S2, the geopolymer gelation precursor is one or more of the following: high-calcium system, low-calcium silica-alumina system, and industrial solid waste co-processing system.

3. The method for preparing low-carbon porous lightweight aggregate using recycled building sand powder according to claim 1, characterized in that: In step S4, the total mass ratio of the plant protein foaming agent solution and the alkali activator to the composite gelling precursor is controlled at 1:2.5 to 4.

5.

4. The method for preparing low-carbon porous lightweight aggregate using recycled building sand powder according to claim 1 or 3, characterized in that: In step S4, the amount of plant protein foaming agent solution added accounts for 0.5% to 5.0% of the mass of the composite gel precursor.

5. The method for preparing low-carbon porous lightweight aggregate using recycled building sand powder according to claim 1, characterized in that: In the plant protein foaming agent, the natural plant protein is one or more of the following: soybean protein, pea protein, wheat protein, corn protein, peanut protein, rice protein, and cottonseed protein; and / or the plant-derived surfactant is one or more of the following: tea saponin, saponins, sulfonated soybean protein, carboxymethylated pea protein, alkyl glycosides, and sodium lauryl sulfate.

6. The method for preparing low-carbon porous lightweight aggregate using recycled building sand powder according to claim 1, characterized in that: In step S4, the rotation speed of the disc granulator is adjusted to 15-25 rpm, the disc tilt angle is adjusted to 40-50°, and the granulation time is 10-20 min.

7. The method for preparing low-carbon porous lightweight aggregate using recycled building sand powder according to claim 1, characterized in that: In step S5, the low-temperature curing method is oven curing, steam curing, or microwave curing.

8. The method for preparing low-carbon porous lightweight aggregate using recycled building sand powder according to claim 1 or 7, characterized in that: In step S5, the low-temperature curing temperature is 60-80℃, and the curing time is 24-72h.

9. A low-carbon porous lightweight aggregate prepared by the method for preparing low-carbon porous lightweight aggregate using recycled building sand powder as described in any one of claims 1 to 8.

10. The low-carbon porous lightweight aggregate according to claim 9, characterized in that: its bulk density... The carbon emission is not higher than 900 kg / m³, the cylinder compressive strength is 4.0 to 10.0 MPa, and the estimated carbon emission is not higher than 50 kg CO2 / t.