Lightweight aggregate alkali-activated concrete and preparation method thereof

Abstract

The invention belongs to the technical field of constructional engineering, and particularly relates to lightweight aggregate alkali-activated concrete and a preparation method thereof. The concrete is prepared from a retarder and the following raw materials in parts by weight: 500 to 550 parts of mineral powder, 100 to 150 parts of fly ash, 150 to 200 parts of water, 100 to 150 parts of water glass, 20 to 30 parts of NaOH, 300 to 350 parts of lightweight aggregate with the particle size of less than 2.5 mm, 350 to 400 parts of lightweight aggregate with the particle size of 2.5 to 5.0 mm, 350 to 400 parts of lightweight aggregate with the particle size of 5 to 10 mm, 150 to 200 parts of lightweight aggregate with the particle size of 10 to 16 mm and 90 to 110 parts of lightweight aggregate with the particle size of 16 to 20 mm. The preparation method relates to the steps of pot moistening, blanking and stirring. The preparation method can be used for preparing the lightweight aggregate alkali-activated concrete with light weight, high strength and good fluidity, and is especially suitable for the field of PPVC modular buildings.

Description

Technical Field

[0001] The invention belongs to the technical field of construction engineering, and particularly relates to a lightweight aggregate alkali-activated concrete and a preparation method thereof. Background Art

[0002] Lightweight aggregate alkali-activated concrete is a material that adds lightweight aggregate and alkaline substances (such as nano sodium silicate, nano sodium hydroxide, etc.) to concrete to improve the performance of concrete. Lightweight aggregate alkali-activated concrete has the following characteristics:

[0003] (1) Lightweight and high strength: The use of lightweight aggregate makes the apparent density of concrete no more than 1950 kg / m 3 , while maintaining high strength.

[0004] (2) Thermal insulation and fire resistance: Lightweight aggregate concrete has good thermal insulation and fire resistance properties and is suitable for building structures that require thermal insulation and fire resistance.

[0005] (3) Good deformation performance: Lightweight aggregate concrete has good deformation performance, low elastic modulus, large shrinkage and creep, and is suitable for projects that require good deformation performance.

[0006] The principle of lightweight aggregate alkali-activated concrete is to promote the reaction of cement by adding alkaline substances (such as nano sodium silicate, nano sodium hydroxide, etc.) to generate more hydration products. These hydration products fill the pores in the concrete, increase the density of the concrete, and thus improve the crack resistance and durability of the concrete. It is suitable for building structures that require thermal insulation, fire resistance, lightness and high strength, such as factory floors, exhibition centers, etc. Its good deformation performance also makes it suitable for projects that require good deformation performance.

[0007] The PPVC space module is a cubic box structure, including four walls, a top plate, and a bottom plate. Several PPVC space modules can be built into a multi-story building or a high-rise building or a building complex. At present, PPVC space modules are mainly cast using ordinary concrete, and there is still a lack of lightweight aggregate alkali-activated concrete specifically for PPVC buildings. Summary of the invention

[0008] The invention discloses a lightweight aggregate alkali-activated concrete and a preparation method thereof. The concrete optimizes the aggregate grading method so that the aggregates can be more densely packed, thereby improving the concrete strength and reducing the concrete density. The concrete is particularly suitable for use in the construction of PPVC space modules.

[0009] To achieve the above purpose, the technical solution of the present invention is:

[0010] A light aggregate alkali-activated concrete, which is composed of a retarder and the following raw materials in parts by weight: 500-550 parts of mineral powder, 100-150 parts of fly ash, graded aggregate components, 150-200 parts of water, 100-150 parts of water glass, and 20-30 parts of NaOH. The graded aggregate components are composed of the following aggregate parts: 300-350 parts of light aggregate with a particle size of less than 2.5 mm, 350-400 parts of light aggregate with a particle size of 2.5-5.0 mm, 350-400 parts of light aggregate with a particle size of 5-10 mm, 150-200 parts of light aggregate with a particle size of 10-16 mm, and 90-110 parts of light aggregate with a particle size of 16-20 mm. The retarder accounts for 4%-6% of the total weight of the fly ash and the mineral powder.

[0011] Preferably, the concrete is composed of a retarder and the following raw materials in parts by weight: 520 parts of mineral powder, 130 parts of fly ash, graded aggregate components, 185 parts of water, 125 parts of water glass, and 27 parts of NaOH. The graded aggregate components are composed of the following aggregate parts: 330 parts of light aggregate with a particle size of less than 2.5 mm, 370 parts of light aggregate with a particle size of 2.5-5.0 mm, 385 parts of light aggregate with a particle size of 5-10 mm, 190 parts of light aggregate with a particle size of 10-16 mm, and 100 parts of light aggregate with a particle size of 16-20 mm. The retarder accounts for 5% of the total weight of fly ash and mineral powder.

[0012] Preferably, the retarder is borax.

[0013] A method for preparing lightweight aggregate alkali-activated concrete comprises the following steps:

[0014] Step 1: Pre-wetting of concrete mixing pot: To prevent the mixing pot from being too dry and absorbing water during mixing, affecting the water-binder ratio, the mixing pot needs to be pre-wetted before mixing concrete; rinse the mixing pot with water and drain it until it is moist but without visible water on the surface;

[0015] Step 2: Adding materials and stirring: Add lightweight aggregate into the pot and stir for 3 minutes. Add retarder, mineral powder and fly ash into the pot and stir for 4 minutes. Finally, add alkali activator composed of water, water glass and NaOH into the pot and stir for 5-6 minutes to obtain a concrete mixture.

[0016] The beneficial effects of the lightweight aggregate alkali-activated concrete and the preparation method of the present invention are:

[0017] 1. The present invention performs a graded design on the aggregate in the concrete. According to several field experiments, it is verified that by optimizing the aggregate gradation, the aggregate can be more densely packed, thereby improving the strength of the concrete and reducing the density of the concrete, which is particularly suitable for the construction of PPVC space modules.

[0018] 2. When the lightweight aggregate alkali-activated concrete of the present invention is applied to the PPVC space module, it can effectively reduce the weight of the space module and ensure the strength of the space module, thereby facilitating the hoisting of the space module and reducing the difficulty of construction.

[0019] 3. The lightweight aggregate alkali-activated concrete of the present invention has good fluidity, a slump of 240 mm, and an expansion of about 500 mm.

[0020] It should be noted that the lightweight aggregate alkali-activated concrete prepared by the present invention can also be applied to other construction fields besides the PPVC construction field. DETAILED DESCRIPTION

[0021] The following description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0022] The following embodiments may be understood as individually expressing a part of a local structure or method of the present invention, or may be understood as a combination of the embodiments to explain the connotation of a larger structure or method of the present invention.

[0023] Example 1

[0024] A light aggregate alkali-activated concrete, which is composed of a retarder and the following raw materials in parts by weight: 500 parts of mineral powder, 100 parts of fly ash, graded aggregate components, 150 parts of water, 100 parts of water glass, and 20 parts of NaOH. The graded aggregate components are composed of the following aggregate parts: 300 parts of light aggregate with a particle size of less than 2.5 mm, 350 parts of light aggregate with a particle size of 2.5-5.0 mm, 350 parts of light aggregate with a particle size of 5-10 mm, 150 parts of light aggregate with a particle size of 10-16 mm, and 90 parts of light aggregate with a particle size of 16-20 mm. The retarder accounts for 4% of the total weight of the fly ash and the mineral powder.

[0025] Example 2

[0026] A light aggregate alkali-activated concrete, which is composed of a retarder and the following raw materials in parts by weight: 550 parts of mineral powder, 150 parts of fly ash, graded aggregate components, 200 parts of water, 150 parts of water glass, and 30 parts of NaOH. The graded aggregate components are composed of the following aggregate parts: 350 parts of light aggregate with a particle size of less than 2.5 mm, 400 parts of light aggregate with a particle size of 2.5-5.0 mm, 400 parts of light aggregate with a particle size of 5-10 mm, 200 parts of light aggregate with a particle size of 10-16 mm, and 110 parts of light aggregate with a particle size of 16-20 mm. The retarder accounts for 6% of the total weight of the fly ash and the mineral powder.

[0027] Example 3

[0028] The concrete is composed of a retarder and the following raw materials in parts by weight: 520 parts of mineral powder, 130 parts of fly ash, graded aggregate components, 185 parts of water, 125 parts of water glass, and 27 parts of NaOH. The graded aggregate components are composed of the following aggregate parts: 330 parts of light aggregate with a particle size of less than 2.5 mm, 370 parts of light aggregate with a particle size of 2.5-5.0 mm, 385 parts of light aggregate with a particle size of 5-10 mm, 190 parts of light aggregate with a particle size of 10-16 mm, and 100 parts of light aggregate with a particle size of 16-20 mm. The retarder accounts for 5% of the total weight of the fly ash and the mineral powder.

[0029] The retarder is borax.

[0030] This embodiment provides an optimal mix ratio, through which lightweight aggregate alkali-activated concrete with a strength of C30 can be prepared.

[0031] Example 4

[0032] Based on the above embodiments, this embodiment discloses a method for preparing lightweight aggregate alkali-activated concrete, comprising the following steps:

[0033] Step 1: Pre-wetting of concrete mixing pot: To prevent the mixing pot from being too dry and absorbing water during mixing, affecting the water-binder ratio, the mixing pot needs to be pre-wetted before mixing concrete; rinse the mixing pot with water and drain it until it is moist but without visible water on the surface;

[0034] Step 2: Adding materials and stirring: Add lightweight aggregate into the pot and stir for 3 minutes. Add retarder, mineral powder and fly ash into the pot and stir for 4 minutes. Finally, add alkali activator composed of water, water glass and NaOH into the pot and stir for 5-6 minutes to obtain a concrete mixture.

[0035] In this embodiment, the light aggregate is first added to absorb the excess water when the pot is moistened to prevent the fly ash and mineral powder added later from sticking to the pot: when pouring the alkali activator, care should be taken to avoid contact with the impeller, stirring shaft and inner wall of the stirring pot as much as possible, and pour it directly on the mixture of ceramsite and powder to avoid loss. When the light aggregate concrete of the present invention is used, the concrete mixture is poured into the shear wall steel mold, and no vibration is required. The bubbles can be discharged by tapping the steel mold template to achieve a compacting effect.

[0036] It should be noted that:

[0037] 1. The lightweight aggregate alkali-activated concrete of the present invention needs to add borax as a retarder, and the optimal dosage range is 4% to 6% of the total weight of mineral powder and fly ash. At around 20°C, the initial setting time can be extended from 20min to 40 to 60min. Other temperature conditions need to be appropriately adjusted, but the borax dosage should not be too much, otherwise there will be a serious loss of strength.

[0038] 2. The light aggregate used in the present invention mainly includes: (1) artificial light aggregate: such as shale ceramsite, clay ceramsite, expanded perlite and light sand. These materials are made by high-temperature sintering or expansion process, and have high strength and good thermal insulation performance. (2) industrial waste light aggregate: including fly ash ceramsite, self-igniting coal gangue, expanded slag beads, coal slag and light sand. These materials are made from industrial waste, which is both environmentally friendly and economical. The light aggregate of the present invention preferably uses ceramsite of different particle sizes.

[0039] 3. Under standard curing conditions, the concrete prepared by the present invention has an average strength of more than 25 MPa at 7 days and more than 37 MPa at 28 days, with a variance of 3 to 4 MPa. The strength will be further improved under high heat and high humidity conditions, and the specific strength value depends on the curing conditions. The density is in the range of 1750 to 1850 kg / m'.

[0040] 4. Since alkali-activated concrete has the characteristic of early strength, the curing conditions after its pouring are crucial, and the maintenance of its initial humidity and temperature is essential; when the temperature is lower than 15°C, it is not recommended to prepare the concrete of the present invention (the curing temperature is too low and the alkali solution is very likely to solidify).

[0041] 5. The principle of setting the graded aggregate components in the present invention is that when a large piece of aggregate is broken, fine aggregate with a gradient particle size will be formed. Through the reverse reduction method, aggregates of different particle sizes should be set as grading to ensure strength while achieving a denser stacking effect. Based on this, the present invention selects the following schemes: 330 parts of light aggregate with a particle size of less than 2.5 mm, 370 parts of light aggregate with a particle size of 2.5-5.0 mm, 385 parts of light aggregate with a particle size of 5-10 mm, 190 parts of light aggregate with a particle size of 10-16 mm, and 100 parts of light aggregate with a particle size of 16-20 mm. The light aggregate with a large particle size plays a role in ensuring strength, while the light aggregate with a small particle size can cooperate with the light aggregate with a large particle size to achieve a denser stacking effect while ensuring strength. Experimental verification shows that this gradient configuration of aggregates and the proportion relationship can effectively reduce the density of concrete while achieving the set strength of concrete, thereby providing high-strength and lightweight concrete materials for PPVC modular buildings.

Claims

1. A lightweight aggregate alkali-activated concrete, characterized in that the concrete is composed of a retarder and the following raw materials in parts by weight: 500-550 parts of mineral powder, 100-150 parts of fly ash, graded aggregate components, 150-200 parts of water, 100-150 parts of water glass, and 20-30 parts of NaOH, wherein the graded aggregate components are composed of the following aggregate parts: 300-350 parts of lightweight aggregate with a particle size of less than 2.5mm, 350-400 parts of lightweight aggregate with a particle size of 2.5-5.0mm, 350-400 parts of lightweight aggregate with a particle size of 5-10mm, 150-200 parts of lightweight aggregate with a particle size of 10-16mm, and 90-110 parts of lightweight aggregate with a particle size of 16-20mm. The retarder accounts for 4%-6% of the total weight of fly ash and mineral powder.

2. A lightweight aggregate alkali-activated concrete as claimed in claim 1, characterized in that: The concrete is composed of a retarder and the following raw materials in parts by weight: 520 parts of mineral powder, 130 parts of fly ash, graded aggregate components, 185 parts of water, 125 parts of water glass, and 27 parts of NaOH. The graded aggregate components are composed of the following aggregate parts: 330 parts of light aggregate with a particle size of less than 2.5 mm, 370 parts of light aggregate with a particle size of 2.5-5.0 mm, 385 parts of light aggregate with a particle size of 5-10 mm, 190 parts of light aggregate with a particle size of 10-16 mm, and 100 parts of light aggregate with a particle size of 16-20 mm. The retarder accounts for 5% of the total weight of the fly ash and the mineral powder.

3. The lightweight aggregate alkali-activated concrete according to claim 1, characterized in that: The retarder is borax.

4. A method for preparing a lightweight aggregate alkali-activated concrete as claimed in claim 1, 2 or 3, characterized in that: The steps include: Step 1: Pre-wetting of concrete mixing pot: To prevent the mixing pot from being too dry and absorbing water during mixing, affecting the water-binder ratio, the mixing pot needs to be pre-wetted before mixing concrete; rinse the mixing pot with water and drain it until it is moist but without visible water on the surface; Step 2: Adding materials and stirring: Add lightweight aggregate into the pot and stir for 3 minutes. Add retarder, mineral powder and fly ash into the pot and stir for 4 minutes. Finally, add alkali activator composed of water, water glass and NaOH into the pot and stir for 5-6 minutes to obtain a concrete mixture.