Lightweight aggregate alkali-activated concrete and preparation method thereof

Abstract

The application belongs to the technical field of building engineering, and particularly relates to a light aggregate alkali-activated concrete and a preparation method. The concrete is composed of retarder and the following raw materials in parts by weight: 500-550 parts of mineral powder, 100-150 parts of fly ash, 150-200 parts of water, 100-150 parts of water glass, 20-30 parts of NaOH, 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 preparation method involves the steps of lubricating, discharging and stirring. The light aggregate alkali-activated concrete prepared by the application is light in weight, high in strength and good in flowability, and is particularly suitable for the field of PPVC modularized building.

Description

Technical Field

[0001] This invention belongs to the field of building engineering technology, specifically relating to a lightweight aggregate alkali-activated concrete and its preparation method. Background Technology

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

[0003] (1) Lightweight and high strength: The use of lightweight aggregates ensures that the apparent density of the concrete is no more than 1950 kg / m³. 3 At the same time, it maintains 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 add alkaline substances (such as nano-sodium silicate, nano-sodium hydroxide, etc.) to promote the reaction of cement and generate more hydration products. These hydration products fill the pores in the concrete, increasing its density and thus improving its crack resistance and durability. It is suitable for building structures requiring thermal insulation, fire resistance, lightweight, and high strength, such as factory floors and exhibition centers. Its good deformation performance also makes it suitable for projects requiring good deformation properties.

[0007] PPVC space modules are cubic box structures, including four walls, a top slab, and a bottom slab. Several PPVC space modules can be assembled into multi-story buildings, high-rise buildings, or building complexes. Currently, PPVC space modules are mainly constructed using ordinary concrete, and there is a lack of lightweight aggregate alkali-activated concrete specifically designed for PPVC buildings. Summary of the Invention

[0008] This invention discloses a lightweight aggregate alkali-activated concrete and its preparation method. This concrete improves concrete strength and reduces concrete density by optimizing the aggregate gradation, enabling the aggregate to be packed more densely. It is particularly suitable for the construction of PPVC space modules.

[0009] To achieve the above objectives, the technical solution of this invention is as follows:

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

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

[0014] Step 1, Pre-wetting the concrete mixing pot: To avoid the mixing pot becoming too dry and absorbing water during the mixing process, which would affect the water-cement 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 any visible water on the surface.

[0015] Step 2, Feeding and Mixing: Add lightweight aggregate to the pot and mix for 3 minutes. Add retarder, mineral powder and fly ash to the pot and mix for 4 minutes. Finally, add alkali activator prepared by water, water glass and NaOH to the pot and mix for 5-6 minutes to obtain concrete mixture.

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

[0017] 1. This invention designs the aggregate gradation in concrete. Based on several field experiments, it has been verified that by optimizing the aggregate gradation, the aggregate can be packed more tightly, thereby improving the concrete strength and reducing the concrete density. It is especially suitable for the construction of PPVC space modules.

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

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

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

[0021] The following description is merely 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 within the scope of protection of the present invention.

[0022] The following embodiments can be understood as illustrating a part of the structure or method of the present invention individually, or as combining the embodiments to explain the broader structure or method of the present invention.

[0023] Example 1

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

[0025] Example 2

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

[0027] Example 3

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

[0029] The retarder mentioned is borax.

[0030] This embodiment provides the optimal mix proportion, which can be used to prepare lightweight aggregate alkali-activated concrete with a strength of C30.

[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 the concrete mixing pot: To avoid the mixing pot becoming too dry and absorbing water during the mixing process, which would affect the water-cement 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 any visible water on the surface.

[0034] Step 2, Feeding and Mixing: Add lightweight aggregate to the pot and mix for 3 minutes. Add retarder, mineral powder and fly ash to the pot and mix for 4 minutes. Finally, add alkali activator prepared by water, water glass and NaOH to the pot and mix for 5-6 minutes to obtain concrete mixture.

[0035] In this embodiment, the lightweight aggregate is added first to absorb excess water during the rinsing process, preventing the subsequently added fly ash and mineral powder from sticking to the pot. When pouring the alkali activator, care should be taken to avoid contact with the impeller, mixing shaft, and inner wall of the mixing pot; it should be poured directly onto the mixture of expanded clay and powder to avoid loss. When using the lightweight aggregate concrete of this invention, the concrete mixture is poured into the shear wall steel mold. No vibration is required; simply tapping the steel mold template will release air bubbles and achieve a compacted effect.

[0036] It should be noted that:

[0037] 1. The lightweight aggregate alkali-activated concrete of the present invention requires the addition of borax as a retarder. 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 20 min to 40 to 60 min. For other temperatures, appropriate adjustments are required. However, the dosage of borax should not be too high, otherwise, severe strength loss will occur.

[0038] 2. The lightweight aggregates selected in this invention mainly include: (1) artificial lightweight aggregates: such as shale ceramsite, clay ceramsite, expanded perlite and its lightweight sand, etc. These materials are made by high-temperature sintering or expansion processes and have high strength and good thermal insulation properties. (2) industrial waste lightweight aggregates: including fly ash ceramsite, self-igniting coal gangue, expanded slag beads, coal slag and its lightweight sand, etc. These materials are made from industrial waste, which is both environmentally friendly and economical. The lightweight aggregates of this invention preferably use ceramsite with different particle sizes.

[0039] 3. Under standard curing conditions, the concrete prepared by this invention has an average strength of more than 25 MPa at 7 days and an average strength of 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 / m³.

[0040] 4. Since alkali-activated concrete has the characteristic of early strength, its curing conditions after pouring are crucial, and maintaining humidity and temperature in the early stage is essential. It is not recommended to prepare the concrete of this invention when the temperature is below 15℃ (the curing temperature is too low and the alkali solution is very likely to solidify).

[0041] 5. The principle of setting graded aggregate components in this invention is as follows: When a large piece of aggregate is crushed, it will form fine aggregate with a gradient in particle size. Through reverse reduction, aggregates of different particle sizes should be set as gradation to ensure strength while achieving a denser packing effect. Based on this, this invention selects the following scheme: 330 parts of lightweight aggregate with a particle size of less than 2.5 mm, 370 parts of lightweight aggregate with a particle size of 2.5-5.0 mm, 385 parts of lightweight aggregate with a particle size of 5-10 mm, 190 parts of lightweight aggregate with a particle size of 10-16 mm, and 100 parts of lightweight aggregate with a particle size of 16-20 mm. Among them, the large-particle-size lightweight aggregate plays the role of ensuring strength, while the small-particle-size lightweight aggregate, while ensuring strength, can be combined with the large-particle-size lightweight aggregate to achieve a denser packing effect. Experiments have verified that this gradient aggregate configuration and proportion can effectively reduce the density of concrete while achieving the set strength, thus 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 suitable for use in the construction of PPVC space modules, and is composed of a retarder and the following raw materials in parts by weight: 500-550 parts mineral powder, 100-150 parts fly ash, graded aggregate components, 150-200 parts water, 100-150 parts water glass, and 20-30 parts NaOH, wherein the graded aggregate components are composed of the following aggregate parts: The aggregate comprises 300-350 parts of lightweight aggregate with a particle size of less than 2.5 mm, 350-400 parts of lightweight aggregate with a particle size of 2.5-5.0 mm, 350-400 parts of lightweight aggregate with a particle size of 5-10 mm, 150-200 parts of lightweight aggregate with a particle size of 10-16 mm, and 90-110 parts of lightweight aggregate with a particle size of 16-20 mm. The retarder accounts for 4%-6% of the total weight of fly ash and mineral powder. The graded aggregate component is composed of lightweight aggregate, which is ceramsite.

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

3. The lightweight aggregate alkali-activated concrete as described in claim 1, characterized in that: The retarder mentioned is borax.

4. A method for preparing lightweight aggregate alkali-activated concrete as described in claim 1, 2, or 3, characterized in that, Includes the following steps: Step 1, Pre-wetting the concrete mixing pot: To avoid the mixing pot becoming too dry and absorbing water during the mixing process, which would affect the water-cement 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 any visible water on the surface. Step 2, Feeding and Mixing: Add lightweight aggregate to the pot and mix for 3 minutes. Add retarder, mineral powder and fly ash to the pot and mix for 4 minutes. Finally, add alkali activator prepared by water, water glass and NaOH to the pot and mix for 5-6 minutes to obtain concrete mixture.