CN112062507A

CN112062507A - Concrete containing recycled waste brick fine aggregate

Info

Publication number: CN112062507A
Application number: CN202010962250.9A
Authority: CN
Inventors: 韩雪松
Original assignee: BEIJING XINAO CONCRETE GROUP CO LTD
Current assignee: BEIJING XINAO CONCRETE GROUP CO LTD
Priority date: 2020-09-14
Filing date: 2020-09-14
Publication date: 2020-12-11

Abstract

The invention provides a concrete containing recycled waste brick fine aggregate, which comprises the following components in percentage by weight: aggregate from raw materials including construction waste bricks, and modified cement. By using such concrete, waste bricks can be fully utilized, and the strength of the concrete can be ensured.

Description

Concrete containing recycled waste brick fine aggregate

Technical Field

The invention belongs to the technical field of building materials, and particularly relates to concrete containing recycled waste brick fine aggregate and a preparation method thereof.

Background

Along with the steady development of national economy and the acceleration of urbanization process in China, the generated construction waste is increased day by day. It is estimated that cities in China generate about 70 million tons of garbage annually, and the amount of garbage is continuously increasing, wherein the amount of construction garbage is about 33 million tons, and the total amount of garbage accounts for about 50 percent of the total amount of the urban garbage. Most of the demolished buildings are brick-concrete structure buildings, and the construction waste bricks account for a considerable proportion of the construction waste generated by demolishing the buildings. How to realize recycling of the construction waste bricks is widely researched.

CN106830792A discloses a concrete doped with waste bricks and recycled coarse aggregate, which is composed of the following raw materials in parts by weight: 1-1.6 parts of cementing material, 1-1.7 parts of fine aggregate and 1.2-2.5 parts of recycled coarse aggregate, thereby greatly reducing resource consumption in the building construction process, realizing the treatment of building garbage and reducing the environmental burden.

CN110240487A discloses a method for preparing an industrial kiln castable by using building waste bricks as raw materials, which comprises the following steps: 1) equipment selection, 2) crushing, 3) screening and 4) stirring: a. quantitative cement, fine powder and water are simultaneously added into a feed inlet of the refractory castable stirrer through a cement tank, a fine powder storage device and a water tank and are uniformly stirred; b. b, simultaneously adding quantitative fine aggregate and additives into the uniformly stirred slurry in the step a through a fine aggregate storage device and an additive storage device, and uniformly stirring again; c. b, adding coarse aggregate into the uniformly stirred slurry in the step b through a coarse aggregate storage device, and finally stirring to form a refractory castable; the casting material has the characteristics of high strength, cement consumption reduction, construction cost reduction and the like.

CN102701647A discloses a preparation method of recycled aggregate ready-mixed mortar, wherein waste concrete, waste bricks and waste sand ash construction wastes smaller than 690mm are used as raw materials, the raw materials are quantified according to the requirement, the raw materials are subjected to grade screening after being crushed, dried and the moisture content of the raw materials is smaller than or equal to 0.5%, metal, wood dust, plastics and sundries are removed in the grade screening, recycled aggregates with the particle size of 0.075-0.15mm, 0.15-0.3mm, 0.3-0.6mm, 0.6-1.18mm, 1.18-2.36mm, 2.36-4.75mm, 4.75-10mm and 10-32mm are prepared, and the total proportion of the recycled aggregates, cement, mineral powder, cellulose, short fibers, yellow glue powder and waterproof powder to water is 1:0.18, and the recycled aggregates, cement, plastering, waterproof and ground mortar are prepared respectively. Can be used as building material.

CN103553689A discloses a high-strength alkali-resistant refractory castable, which comprises aggregate, powder, a bonding agent, an additive and water, wherein the raw materials in parts by weight are as follows: 51-62 parts of aggregate, 25-30 parts of powder, 3-5 parts of binding agent, 5-6 parts of additive and 5-8 parts of water: wherein the aggregate is composed of waste electric porcelain, waste tiles and coal gangue, the powder is composed of coal gangue, waste electric porcelain, waste tiles, flint clay and silica micropowder, the binding agent is aluminate cement, and the additive is alpha-alumina fine powder.

CN102815964A discloses a construction waste recycling process, which comprises the following steps: collecting waste concrete, waste mortar and waste brick slag; crushing and screening: crushing and screening the collected waste concrete, waste mortar and waste brick slag to obtain a regenerated coarse aggregate and a regenerated fine aggregate; preparing foam concrete: preparing cement slurry: uniformly stirring cement, water, the recycled coarse aggregate and the recycled fine aggregate to obtain cement slurry; foam diluent addition: and adding the foam diluent formed by uniformly mixing the foaming agent and water into the cement slurry and uniformly stirring to obtain the foam concrete.

"influence of typical construction solid waste recycled aggregate on the performance of the environment-friendly brick", Cheng Guo Ming & lt environmental engineering academy, in 2013, regional characteristic aggregates such as construction waste recycled aggregate, bottom slag and stone powder are used for preparing the environment-friendly brick, and the influence of the aggregate on the mechanical property of the environment-friendly brick is systematically investigated. Experimental results show that the influence of the type of the recycled aggregate on the compressive strength of the environment-friendly brick is remarkable, the compressive strength of the environment-friendly brick is gradually increased due to the increase of concrete in the recycled aggregate, and the compressive strength of the environment-friendly brick is obviously reduced due to the increase of the content of clay bricks in the recycled aggregate.

However, in the prior art, when the aggregate is made of the building waste bricks, the strength of the prepared concrete is often not high enough to meet the requirements of some specific applications. Therefore, there is a need for a concrete having high compressive strength using aggregate made of construction waste bricks and a method for preparing the same.

Disclosure of Invention

In order to solve the above problems, the present inventors have conducted extensive studies and extensive experiments to provide a concrete comprising recycled waste brick fine aggregate and a method for preparing the same. The concrete has or even exceeds the compressive strength of concrete made from conventional sand aggregate.

In one aspect of the present invention, there is provided a concrete comprising recycled waste brick fine aggregate, the concrete comprising: aggregate from raw materials including construction waste bricks, and modified cement.

Preferably, the modified cement comprises fly ash.

More preferably, the fly ash is added in an amount of 10-30 wt%, preferably 10-20 wt% of the cement.

Preferably, the modified cement comprises an activator. More preferably, the amount of the activator is 0.5 wt% to 5.0 wt% based on the weight of the modified cement.

Preferably, the activator comprises at least one of calcium hydroxide and calcium chloride.

Preferably, the concrete further comprises sand aggregate.

Preferably, the concrete further comprises a water reducing agent.

The inventor researches and discovers that the crystal of the waste brick fine aggregate is in an amorphous state, has an active base and is used as a mixtureWhen the concrete aggregate is solidified, the pores can be reduced, pore water can be reduced, the capillary action force can be reduced, the microcracks of the concrete can be effectively reduced, and the early drying shrinkage of the test block can be slowed down. Al in fine aggregate of waste brick₂O₃And SiO₂The component is mixed with lime or cement and mixed with water, and then can be chemically reacted with calcium hydroxide to produce a series of hydration products of hydrated calcium silicate, hydrated calcium aluminate and the like, and these products can be hardened in air or water and can produce strength, so that the Ca (OH) content in the hydration system can be reduced₂Content, and quickens the hydration process.

The fly ash particles are mostly glass beads, play a role in lubricating in concrete mixtures, can reduce the internal friction, enable the concrete mixtures doped with fly ash to have better fluidity than standard concrete, are convenient for construction, and have the function of water reduction, and the fine particles in the fly ash can be uniformly distributed in cement paste to fill pores and capillary holes, thereby improving the pore structure of the concrete and increasing the compactness of the concrete.

Therefore, the inventor effectively combines the concrete aggregate containing the waste brick aggregate and the fly ash to play the synergistic promotion effect of the concrete aggregate and the fly ash, thereby realizing the advantage complementation.

In another aspect, there is also provided a method of preparing the aforementioned concrete, the method comprising the steps of: aggregate from raw materials including construction waste bricks is mixed with concrete and water.

Preferably, the method further comprises curing after mixing.

Preferably, the aggregate from the waste brick raw material has a particle size of 6mm or more in average.

Preferably, the curing includes 7 days, 14 days and 28 days of curing.

Preferably, the SiO of the building waste brick₂The content is more than 63.6 wt%.

Preferably, Al of the construction waste brick₂O₃The content is more than 21.5 wt%.

Preferably, the SiO of the building waste brick₂And Al₂O₃The sum of the amounts is greater than 89.5 wt.%, preferably greater than 90.0 wt.%. Research shows that when the SiO of the building waste brick is used₂And Al₂O₃When the content satisfies the above requirements, a good hydration effect can be achieved.

The concrete may be for construction of buildings, roads, sport areas, etc.

Preferably, the aggregate from the construction waste bricks is mixed with 10 to 50mm of sand or coarse crushed stone (preferably graded crushed stone) in a weight ratio of 1:1 to 1:5, and used as an aggregate, for example, an aggregate for road concrete. After the two materials are mixed, a framework can be formed in concrete paving, mechanical paving is facilitated, and the embedded lock is more facilitated due to larger particle edges and corners. The large-particle waste bricks can also play a role of a gap filler of graded broken stones, and are favorable for filling and compacting. The proportioning ratio can ensure that the filler can be well compacted in the gaps of the aggregate.

In the present invention, it is particularly preferable that the water reducing agent is a water reducing agent represented by the following formula (I):

wherein, preferably, τ is 0.2 to 0.6, more preferably 0.2 to 0.4; n is preferably an integer from 2 to 4, more preferably from 3 to 4, most preferably 4. When τ is within the range, the optimum coordination of the two polymer blocks can be achieved. The value of n allows to obtain an optimal hydrophobicity and thus an optimal water reducing effect.

The weight average molecular weight of the water-reducing agent of the formula (I) is preferably 7,000-70,000, more preferably 10,000-50,000.

The water reducing agent can be prepared by polymerizing a carboxylate monomer and a polycarboxylate monomer by a simple polymerization method. The polymerization can be carried out by bulk or suspension processes.

Preferably, the water reducing agent is used in an amount of 0.2 to 5.0 wt%, preferably 0.5 to 2.0 wt%, based on the weight of the cement.

The present inventors have found that when aggregate made from raw materials of construction waste bricks and modified cement made from raw materials of construction waste bricks are used together, the strength of concrete is sometimes difficult to meet the requirements for high-standard road concrete applications, and for this reason, the present invention provides the above-mentioned targeted water reducing agent.

It was found that the polymer behaviour of cement at the cement-aggregate particle interface is significantly improved when using this water-reducing agent, and that this water-reducing agent has a positive effect on the surface potential and the rheological properties. When the concrete is used at the same amount, the compressive strength of the concrete can be improved by 18-38% compared with the common commercial polycarboxylate water reducing agent (such as sodium polycarboxylate DY-YL-330 of Nantongdaiyi chemical company).

Detailed description of the preferred embodiments

In order that the invention may be more clearly understood, reference will now be made in detail to the following examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

Taking the waste bricks of the building produced by dismantling, wherein the waste bricks are waste red bricks and SiO of the waste red bricks₂64.1 wt% of Al₂O₃The content of 22.3 wt%, the construction waste bricks were crushed with a jaw crusher and then sieved, particles having an average particle diameter of more than 6mm were collected, and the particles were mixed with sand in a weight ratio of 10 to 50mm in the range of 1:4 to be used as aggregate, which was then mixed with modified cement comprising preferably 15.2 wt% fly ash, 0.56 wt% excitant (1: 1 weight mixture of calcium hydroxide and calcium chloride), and 0.51% water reducing agent represented by formula (I) and water. After the cement (content: 7.4 wt%) was mixed with aggregate and water, the compressive strength after curing for 28 days was measured. The determination of the compressive strength is carried out by using a MATEST compressive and flexural testing machine and preparing a test piece according to the test method GB/T2542-2012. The detection proves that the compressive strength is 52.29 MPa.

Comparative example 1

Example 1 was repeated except that the water-reducing agent used was a commercial water-reducing agent (model DY-YL-330 sodium polycarboxylate from Nantongdaiyi chemical company) and the aggregate was sand alone. The compressive strength was measured to be 47.71 MPa.

As can be seen from the above examples and comparative examples, the method of the present application makes full use of the construction waste bricks. And due to the use of the water reducing agent, compared with concrete prepared from pure sandstone aggregate, the compressive strength is not reduced, but is improved.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. All citations referred to herein are incorporated herein by reference to the extent that no inconsistency is made.

Claims

1. A concrete comprising recycled waste brick fine aggregate, the concrete comprising: aggregate from raw materials including construction waste bricks, and modified cement.

2. The concrete of claim 1, wherein the modified cement comprises fly ash.

3. The concrete according to claim 1 or 2, wherein the modified cement comprises an activator.

4. The concrete of any one of claims 1-3, wherein the activator comprises at least one of calcium hydroxide and calcium chloride.

5. The concrete according to any one of the preceding claims, further comprising sand aggregate.

6. The concrete according to claim 5, further comprising a water reducing agent.

7. A method of producing concrete according to any one of the preceding claims, characterized in that it comprises the following steps: aggregate from raw materials including construction waste bricks is mixed with concrete and water.

8. The method of claim 7, further comprising curing after mixing.

9. A method according to claim 7 or 8, characterized in that the aggregates from the waste brick raw material are particles having an average particle size of 6mm or more.

10. The method of any one of claims 7-9, wherein the curing comprises 7 days, 14 days, and 28 days of curing.