CN107200526A - C40 grades are mixed slag regeneration aggregate self-compacting concrete and preparation method thereof - Google Patents

Abstract

The invention discloses a C40 grade self-compacting concrete mixed with steel slag recycled aggregate and a preparation method thereof. The C40 grade steel slag mixed recycled aggregate self-compacting concrete consists of raw materials in parts by mass: 1 part of water and 1 part of natural coarse bone 3.089 parts of raw material, 1.322 parts of recycled coarse aggregate, 3.822 parts of fine aggregate, 1.941-2.183 parts of cement, 0.2426-0.4851 parts of steel slag, 0.609 parts of fly ash, 0.064 parts of additional water, and admixtures of Composed of 0.00495 to 0.0124 parts. The concrete of the present invention has good fluidity, filling property, and segregation resistance, and the time-lapse loss and strength meet the relevant requirements of construction. At the same time, the preparation method is simple, which reduces the production cost of self-compacting concrete with the same strength as compared with the same period last year, and also solves the problem. The problem of steel slag and construction waste disposal can alleviate the pressure of resource depletion. It is green and environmentally friendly and suitable for industrial production.

Description

C40 grade steel slag mixed recycled aggregate self-compacting concrete and its preparation method

technical field

The invention relates to the technical field of building materials, in particular to a C40 grade self-compacting concrete mixed with steel slag recycled aggregate and a preparation method thereof.

Background technique

Self-compacting concrete (Self Compacting Concrete or Self-Consolidating Concrete referred to as SCC) refers to relying on self-gravity without additional mechanical vibration force, it can have sufficient flow and deformation capacity, even if there are dense steel bars, it can fill the formwork space and Form dense and uniform concrete. The preparation of self-compacting concrete generally reduces the yield stress of the concrete enough to be overcome by the shear stress generated by its own weight through the selection and matching of admixtures, cementitious materials, coarse and fine aggregates, and careful mix ratio design, so that the fluidity of the concrete increases. , At the same time, it has enough plastic viscosity to suspend the aggregate in the cement slurry, without segregation and bleeding problems, it can flow freely and fully fill the space in the formwork, forming a dense and uniform gel structure. With the rapid development of my country's construction industry and the shortage of labor force, my country's demand for self-compacting concrete is gradually increasing, so self-compacting concrete has a broad application prospect in my country's construction industry.

As my country's steel output continues to grow rapidly, steel production will produce steel slag that pollutes the environment; the shortening of the service life of the building itself and the construction and demolition cycle have resulted in a large amount of construction waste that cannot be disposed of. The research on steel slag powder mainly focuses on the use of steel slag powder instead of cement to prepare ordinary concrete, while the research on recycled aggregate mainly focuses on the use of waste concrete to process recycled coarse aggregate to replace part of the natural coarse aggregate to prepare recycled concrete. Although the self-compacting concrete prepared at present meets the construction and strength requirements, the cost is relatively high. Therefore, the dual solid waste of steel slag and recycled coarse aggregate is used to replace cement and natural coarse aggregate to prepare self-compacting concrete, which can reduce the production of self-compacting concrete. cost, and self-compacting concrete is a kind of high-performance concrete different from ordinary concrete. It has high fluidity and does not segregate or bleed during the pouring process. It can be filled with formwork and wrapped steel bars without mechanical vibration force. At the same time, the existing technologies for preparing recycled concrete and steel slag concrete cannot solve the current situation of labor shortage.

Contents of the invention

The purpose of the present invention is to address the problems and defects of the prior art, and provide a C40 grade recycled aggregate with steel slag mixed with good fluidity, filling property, segregation resistance, and time-lapse loss and strength meeting the relevant requirements of construction. Dense concrete and method for its preparation.

The unit price of recycled aggregate obtained by the present invention is about 60 yuan/m ³ (including processing fee), and the unit price of natural aggregate is about 90 yuan/m ³ . Calculated with a 30% replacement rate, the self-compacting concrete with recycled aggregates mixed with steel slag saves about 8.2 yuan/m ³ due to recycled aggregates; the unit price of steel slag powder obtained by processing waste steel slag is about 110 yuan/t (including processing fees) , while the unit price of cement is about 330 yuan/t, and the replacement rate of cement replaced by steel slag per cubic meter is calculated as 15%, the self-compacting concrete mixed with steel slag recycled aggregate saves about 16.15 yuan/m ³ due to steel slag. Under the same mix ratio, the self-compacting concrete mixed with steel slag recycled aggregate can directly save the material cost by about 24.35 yuan/m ³ . At the same time, the preparation method of the C40-grade recycled aggregate self-compacting concrete mixed with steel slag is simple, which reduces the production cost of self-compacting concrete with the same strength as compared with the same period last year, and can also solve the problem of steel slag and construction waste disposal, relieve the pressure of resource depletion, and is green and environmentally friendly. The preparation scheme is simple and suitable for industrial production.

For achieving the above object, technical scheme of the present invention is:

A kind of C40 grade steel slag mixed recycled aggregate self-compacting concrete, by mass parts: water is 1 part, natural coarse aggregate is 3.089 parts, recycled coarse aggregate is 1.322 parts, fine aggregate is 3.822 parts, cement is 1.941 parts ~ 2.183 parts, steel slag 0.2426 ~ 0.4851 parts, fly ash 0.609 parts, additional water 0.064 parts, admixture 0.00495 ~ 0.0124 parts.

Further, the above-mentioned steel slag contains 15.9% MgO by mass percentage, and the steelmaking waste slag stored for more than 6 months is subjected to iron removal, ball milling, and screening to obtain steel slag powder with a particle size of less than 0.08 mm. The steel slag has an apparent density of 2.36g/cm ³ and an alkalinity coefficient of 1.99. Other detection indicators of steel slag are in line with the GB/T 20491-2006 standard "Steel slag powder used in cement and concrete".

Described steel slag main chemical composition (%) is as shown in table 1 below:

Furthermore, the above-mentioned regenerated coarse aggregate is waste concrete containing broken bricks and mortar blocks, and after sorting, crushing and screening, the regenerated coarse aggregate with a particle size of 5-20mm is obtained. The apparent density of the recycled coarse aggregate is 2.60g/cm ³ , the bulk density is 1.20g/cm ³ , and the water absorption rate is 4.75%.

Further, the natural coarse aggregate mentioned above is crushed stone with a particle size of 5-20 mm. The natural coarse aggregate has an apparent density of 2.87g/cm ³ , a bulk density of 1.53g/cm ³ and a water absorption rate of 0.54%.

Furthermore, the fine aggregate mentioned above is any one of river sand and medium sand graded in zone II.

Further, the above-mentioned admixture is a high-efficiency polycarboxylate water reducer with a water reducing rate of 25%.

Further, the above-mentioned cement is any one of P.O42.5 ordinary Portland cement and Portland cement.

Furthermore, the above-mentioned fly ash is Class I fly ash.

To achieve the above object, another technical solution of the present invention is:

A preparation method of C40 grade steel slag mixed recycled aggregate self-compacting concrete, comprising the following steps:

Step 1. Weigh the cement, natural coarse aggregate, recycled coarse aggregate, fine aggregate, steel slag, fly ash, water, additional water and high-efficiency polycarboxylate water reducer according to the parts by weight of each raw material component ;

Step 2. Put the weighed natural coarse aggregate, regenerated coarse aggregate, fine aggregate, cement, fly ash and steel slag into the mixer whose inner wall is evenly coated with a thin layer of concrete, at 45 rpm Start the mixer and stir for 2 to 3 minutes;

Step 3. Add the weighed water and additional water, and continue to stir at 45 rpm for 2-3 minutes;

Step 4. Add the weighed high-efficiency polycarboxylate superplasticizer into the mixer at least five times. After each addition, start the mixer and stir for 1 minute, and continue stirring for 3 minutes after the last addition, that is, C40 grade steel slag regeneration is obtained. aggregate self compacting concrete

The present invention uses steel slag and recycled coarse aggregate to replace part of cement and natural coarse aggregate to prepare high-performance recycled aggregate self-compacting concrete for three purposes:

First, large-scale iron and steel production accompanied by the production of steel slag has already caused environmental impacts, and solving the problems caused by steel slag is already a subject of sustainable economic development of a country;

The second is to reduce the production of cement, thereby reducing the emission of carbon dioxide, which is conducive to the protection of the atmospheric environment;

The third is to recycle the construction waste of waste concrete with broken bricks and mortar blocks, which meets the requirements of green building materials. At present, there are few studies on dual solid waste materials using steel slag and recycled coarse aggregate. Therefore, the preparation of self-compacting concrete mixed with steel slag recycled aggregate can not only solve the environmental and social problems caused by waste steel slag and construction waste, but also have certain economic benefits. Benefits, and implement the national technical and economic policy of resource conservation and green production.

The advantages of the present invention are:

1. The C40 grade steel slag recycled aggregate self-compacting concrete produced by the present invention uses materials except cement, stone, sand and water four kinds of raw materials used in ordinary concrete, and also includes fly ash and 6 iron-removed materials. The waste steel slag that is more than one month old has been ball-milled to reach the cement-grade steel slag powder, and the waste concrete containing broken bricks and mortar blocks has been crushed and screened to continuously grade recycled coarse aggregate and high-efficiency polycarboxylate superplasticizer. The fluidity, filling, segregation resistance, time loss and strength of the self-compacting concrete mixed with steel slag recycled aggregates all meet the relevant requirements;

2. The present invention adopts steelmaking waste slag ball milling to achieve cement grade to replace part of cement (10% to 20%), and adopts waste concrete containing broken bricks and mortar blocks as continuous gradation regenerated coarse aggregate to replace part of natural coarse aggregate ( 30%) to prepare the method of self-compacting concrete mixed with steel slag recycled aggregate, which can effectively solve the waste steel slag produced by steel mills, reduce construction waste, relieve the pressure of resource depletion, be green and environmentally friendly, save resources, and reduce the cost of self-compacting concrete with the same strength as compared with the same period of last year. The production cost is in line with the concept of national sustainable development and suitable for industrialized production.

3. The present invention has a lower loss rate over time, the average value of the initial slump expansion degree is 700mm, the J ring expansion degree is 677.5, the average value of the slump expansion degree after 90mins is 552.5mm, and the J ring expansion degree is 517.5mm , that is, the self-compacting concrete mixed with steel slag recycled aggregate still has certain fluidity after 90 minutes. At this time, 0.15% high-efficiency polycarboxylate superplasticizer can be added, and the slump expansion can be restored to 695mm, and the J-ring expansion can be 670mm.

4. The compressive strength test of the cube of the present invention is above 45MPa, which has a high strength guarantee rate. At present, my country's waste steel slag is about 150 million tons, and waste concrete is at least 250 million tons, and this data is still rising. These solid wastes have created severe environmental pressures. The invention realizes recycling of double solid waste materials, improves the greenness of concrete, and can directly contribute to energy saving and emission reduction.

detailed description

The above solution will be further described below in conjunction with specific embodiments. It should be understood that these examples are used to illustrate the present invention and not to limit the scope of the present invention. The implementation conditions adopted in the examples can be further adjusted according to the conditions of specific manufacturers, and the implementation conditions not indicated are usually the conditions in routine tests.

Example

(1) Prepare raw materials

Cement: P·O4 2.5 ordinary Portland cement with an apparent density of 3.20g/cm ³ .

Fly ash: Class I fly ash with an apparent density of 2.42g/cm ³ .

Fine aggregate: river sand with a fineness modulus of 2.4, a bulk density of 1.54g/cm ³ , an apparent density of 2.64g/cm ³ , and a moisture content of 0.35%.

Steel slag: the steelmaking waste slag that has been placed in the steel plant for more than 6 months has been iron-removed, ball milled and screened, and the steel slag powder with a particle size of less than 0.08mm is selected, the apparent density is 2.36g/cm ³ , and the alkalinity coefficient of the steel slag is 1.99 , the mass percentage of MgO is 15.9%, and other detection indicators of steel slag are in line with the GB/T 20491-2006 standard of "Steel Slag Powder Used in Cement and Concrete".

Natural coarse aggregate: 5-20mm crushed stone, with an apparent density of 2.87g/cm ³ , a bulk density of 1.53g/cm ³ , and a water absorption rate of 0.54%.

Recycled coarse aggregate: After sorting, crushing and screening waste concrete containing broken bricks and mortar blocks in construction waste, and screening out particles smaller than 4.75mm and larger than 20mm, the aggregate particle size is 5-20mm Recycled coarse aggregate is processed in sections, with an apparent density of 2.60g/cm ³ , a bulk density of 1.20g/cm ³ and a water absorption rate of 4.75%.

Admixture: high-efficiency polycarboxylate superplasticizer.

Water and additional water: tap water.

(2) In order to prevent sticking to the pot, prepare ready-mixed concrete according to the parts by weight of each raw material component, and the dosage is determined according to the volume of the mixer. After the inner wall is coated with a thin layer of cement mortar, remove the remaining concrete;

(3) Weigh cement, natural coarse aggregate, recycled coarse aggregate, fine aggregate, steel slag, fly ash, water, additional water and admixture according to the parts by weight of each raw material component; Add the weighed natural coarse aggregate, recycled coarse aggregate, fine aggregate, cement, fly ash and steel slag in order to the mixer with a thin layer of concrete, and then start the mixer to dry mix for 2mins to ensure that each material group If the volume of the mixer is large, the dry mixing time can be extended appropriately;

(4) Add the weighed water and additional water, and continue stirring for 2-3mins;

(5) Finally, add the weighed polycarboxylate high-efficiency water reducer to the mixer at least five times. After each addition, start the mixer and stir for 1 minute, and observe the fluidity of the mixture until the last addition Continue stirring for 3 minutes to obtain C40 grade self-compacting concrete mixed with steel slag recycled aggregate.

The mixing ratio of C40 grade self-compacting concrete with recycled aggregates mixed with steel slag is shown in Table 2 below:

The effect test data of the C40 grade steel slag-mixed recycled aggregate self-compacting concrete example is shown in Table 3 below:

The above examples are only to illustrate the technical conception and characteristics of the present invention, and its purpose is to allow people familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (9)

1. A kind of self-compacting concrete of C40 grade mixed with steel slag recycled aggregate, by mass parts: water is 1 part, natural coarse aggregate is 3.089 parts, recycled coarse aggregate is 1.322 parts, fine aggregate is 3.822 parts, cement 1.941-2.183 parts, steel slag 0.2426-0.4851 parts, fly ash 0.609 parts, additional water 0.064 parts, admixture 0.00495-0.0124 parts. 2. The self-compacting concrete of C40 grade mixed steel slag regenerated aggregate according to claim 1 is characterized in that, the steel slag contains 15.9% MgO by mass percentage, the steelmaking waste slag stored for more than 6 months, after iron removal , ball milling, and sieving to obtain steel slag powder with a particle size of less than 0.08mm. 3. according to the described C40 class steel slag regenerated aggregate self-compacting concrete of right 1, it is characterized in that, described regenerated coarse aggregate is the discarded concrete that contains broken brick, mortar block, through sorting, crushing, screening, obtains Recycled coarse aggregate with a particle size of 5-20mm. 4. The self-compacting concrete of grade C40 mixed with steel slag recycled aggregate according to claim 1, characterized in that the natural coarse aggregate is crushed stone with a particle size of 5-20 mm. 5. The C40 grade self-compacting concrete with steel slag mixed with recycled aggregate according to claim 1, characterized in that the fine aggregate is river sand or medium sand graded in Zone II. 6. The self-compacting concrete of grade C40 mixed with steel slag recycled aggregate according to claim 1, characterized in that the admixture is a high-efficiency polycarboxylate water reducer with a water reducing rate of 25%. 7. The self-compacting concrete of grade C40 mixed with steel slag recycled aggregate according to claim 1, characterized in that the cement is P.O42.5 ordinary Portland cement or Portland cement. 8. The self-compacting concrete of grade C40 mixed with steel slag recycled aggregate according to claim 1, characterized in that the fly ash is grade I fly ash. 9. A preparation method of C40 grade steel slag mixed recycled aggregate self-compacting concrete as described in any one of claims 1 to 9, characterized in that, comprising the following steps: Step 1. Weigh the cement, natural coarse aggregate, recycled coarse aggregate, fine aggregate, steel slag, fly ash, water, additional water and high-efficiency polycarboxylate water reducer according to the parts by weight of each raw material component ; Step 2. Put the weighed natural coarse aggregate, regenerated coarse aggregate, fine aggregate, cement, fly ash and steel slag into the mixer whose inner wall is evenly coated with a thin layer of concrete, at 45 rpm Start the mixer and stir for 2 to 3 minutes; Step 3. Add the weighed water and additional water, and continue to stir at 45 rpm for 2-3 minutes; Step 4. Add the weighed high-efficiency polycarboxylate superplasticizer into the mixer at least five times. After each addition, start the mixer and stir for 1 minute, and continue stirring for 3 minutes after the last addition, that is, C40 grade steel slag regeneration is obtained. Aggregate self-compacting concrete.