阅读说明：本技术 混凝土再生骨料的改性和应用 (Modification and application of concrete recycled aggregate ) 是由 刘小艳 刘力 江波 揭汉铎 赵平忠 余谨瑶 刘彦琦 李田雨 左俊卿 夏苏鲁 于 2020-11-10 设计创作，主要内容包括：本发明公开了一种混凝土再生骨料的改性和应用,所述的改性方法包括将由纳米二氧化硅、纳米氧化石墨烯分散液和再生混凝土微粉配置的改性浆液均匀的喷洒于再生骨料表面。本发明通过对建筑垃圾所制作的再生粗骨料进行改性处理能够有效的降低再生粗骨料的孔隙率,提高再生粗骨料的密实程度,将改性后的再生粗骨料用作制作混凝土的原料,不仅实现了建筑垃圾的回收利用,而且还显著提高了所制作的混凝土的力学强度。(The invention discloses modification and application of concrete recycled aggregate, and the modification method comprises the step of uniformly spraying modified slurry prepared from nano silicon dioxide, nano graphene oxide dispersion liquid and recycled concrete micro powder on the surface of the recycled aggregate. According to the invention, the porosity of the recycled coarse aggregate can be effectively reduced by modifying the recycled coarse aggregate prepared from the construction waste, the compactness of the recycled coarse aggregate is improved, and the modified recycled coarse aggregate is used as a raw material for preparing concrete, so that the recycling of the construction waste is realized, and the mechanical strength of the prepared concrete is also obviously improved.)

1. A method for modifying recycled concrete aggregate is characterized by comprising the following steps: the method comprises the step of uniformly spraying modified slurry prepared from nano silicon dioxide, nano graphene oxide dispersion liquid and recycled concrete micro powder on the surface of the recycled aggregate.

2. The modification method according to claim 1, characterized in that: the modified slurry respectively comprises 1-2% of nano silica sol, 0.04-0.08% of nano graphene oxide dispersion liquid and 8-12% of recycled concrete micro powder slurry according to mass percent.

3. The modification method according to claim 2, characterized in that: the modified slurry comprises 1.5% of nano silica sol, 0.05% of nano graphene oxide dispersion liquid and 10% of recycled concrete micro powder slurry respectively according to mass fraction.

4. The modification method according to any one of claims 1 to 3, characterized in that: the concentration of the nano graphene oxide dispersion liquid is 1-2 mg/ml.

5. The modification method according to claim 1, characterized in that: the particle size range of the selected recycled aggregate is 5-30 mm.

6. The modification method according to any one of claims 1 to 3, characterized in that: the average grain diameter of the recycled concrete micro powder is smallAt 0.16mm, the specific surface area is more than 350m²/k。

7. A modified recycled aggregate obtained by applying the modification method according to any one of claims 1, 2, 3 or 5 to a concrete raw material.

Technical Field

The invention belongs to the field of recycling of construction waste, and particularly relates to modification and application of a concrete recycled aggregate.

Background

Since the 21 st century, the construction industry of China enters a high-speed development stage, a large amount of construction waste is generated, concrete is used as construction waste with the largest proportion, most of the treatment of the concrete is carried out by adopting traditional methods such as open-air stacking, landfill and the like, the method not only occupies a large amount of land resources, but also has great harm to the environment and the personal safety. The negative effects caused by the treatment of construction wastes cause the discussion of sustainable development problems, and the appearance of recycled concrete points out a sustainable development road for the solution of waste concrete.

Waste concrete is processed into recycled coarse aggregate after a series of treatments, and a certain amount of recycled concrete micro powder is generated in the process. The recycled coarse aggregate and the recycled concrete micro powder can be used for respectively replacing natural coarse aggregate and cement to prepare recycled concrete, and the problems of treatment and reutilization of waste concrete can be effectively solved. However, as the surface of the recycled coarse aggregate in the recycled concrete is coated with a considerable amount of cement mortar and a great amount of micro cracks are caused by collision in the crushing process and the like, compared with the natural coarse aggregate, the recycled coarse aggregate has the characteristics of high porosity, high water absorption rate, high crushing index value and the like. This results in that the mechanical properties of recycled concrete are inferior to those of ordinary concrete, so it is necessary to modify recycled aggregate to enhance the strength of recycled concrete.

Disclosure of Invention

The invention provides modification and application of a concrete recycled aggregate, aiming at the problem of recycling of the recycled coarse aggregate made of waste concrete.

The technical purpose is achieved, the technical effect is achieved, and the invention is realized through the following technical scheme:

a method for modifying concrete recycled aggregate comprises the step of uniformly spraying modified slurry prepared from nano silicon dioxide, nano graphene oxide dispersion liquid and recycled concrete micro powder on the surface of the recycled aggregate.

As a further improvement of the invention, the modified slurry comprises 1-2% of nano silica sol, 0.04-0.08% of nano graphene oxide dispersion liquid and 8-12% of recycled concrete micropowder slurry by mass percent respectively.

As a further improvement of the invention, the modified slurry comprises 1.5% of nano silica sol, 0.05% of nano graphene oxide dispersion liquid and 10% of recycled concrete micropowder slurry by mass fraction.

As a further improvement of the invention, the concentration of the nano graphene oxide dispersion liquid is 1-2 mg/ml.

As a further improvement of the invention, the particle size range of the selected recycled aggregate is 5-30 mm.

As a further improvement of the invention, the average particle size of the recycled concrete micro powder is less than 0.16mm, and the specific surface area is more than 350m²/k。

The modified recycled aggregate obtained by applying the modification method is used as a concrete raw material.

The invention has the beneficial effects that: according to the invention, the porosity of the recycled coarse aggregate can be effectively reduced by modifying the recycled coarse aggregate prepared from the construction waste, the compactness of the recycled coarse aggregate is improved, and the modified recycled coarse aggregate is used as a raw material for preparing concrete, so that the recycling of the construction waste is realized, and the mechanical strength of the prepared concrete is also obviously improved.

Drawings

FIG. 1 shows the results of the tests of the compressive strength of recycled concrete produced by the method of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

According to the invention, the recycled aggregate with the particle size range of 5-30 mm is selected for modification, the modified slurry prepared from nano silicon dioxide, nano graphene oxide dispersion liquid and recycled concrete micro powder is uniformly sprayed on the surface of the recycled aggregate under the stirring condition, so that the surface of the recycled aggregate is completely soaked by the modified slurry, and then the recycled aggregate is ventilated and dried.

In one embodiment of the present invention, a mixed liquid obtained by mixing nano silica, nano graphene oxide dispersion liquid, and recycled concrete micropowder in clear water is modified slurry. The prepared modified slurry respectively comprises 1.5% of nano silica sol, 0.05% of nano graphene oxide dispersion liquid and 10% of recycled concrete micro powder slurry according to mass fraction. Wherein the concentration of the nano graphene oxide dispersion liquid is 1-2 mg/ml.

The nano silicon dioxide particles in the modified slurry have the advantages of superfine property, high specific surface area and high activity, form nano silicon dioxide sol in the slurry, have a filling effect, can fill micro cracks in the recycled coarse aggregate, reduce the number of internal pores and improve the compactness of the recycled coarse aggregate. In addition, a certain amount of mortar is contained on the surface of the recycled coarse aggregate, and the nano-silica has a volcanic ash effect, so that the hydration of cement is accelerated, the generation of C-S-H gel is promoted, and the nano-silica can be filled in gaps of the recycled coarse aggregate, so that the recycled coarse aggregate is more compact. The nano graphene oxide particles in the modified slurry can be connected through a chemical reaction between surface carboxyl groups of the nano graphene oxide particles and cement hydration products Ca (OH)2, so that a 3D network structure is formed in a cement matrix, and the cement hydration products are inserted into the 3D network structure, so that the reinforcement and toughening of the cement-based material are realized. The average grain diameter of the selected recycled concrete micro powder is less than 0.16mm, and the specific surface area is more than 350m²The cement particles in the recycled concrete micropowder slurry also have filling effect, and the hydration products of the cement can be continuously filled in the recycled concrete micropowder slurryThe gap of the raw coarse aggregate improves the compactness of the regenerated coarse aggregate. Therefore, the modified slurry can effectively improve the performance of the recycled coarse aggregate by the synergistic use of the nano-silica sol, the nano-graphene oxide dispersion liquid and the recycled concrete micro-powder slurry.

The modified recycled aggregate obtained by applying the above modification method was used as a raw material for concrete, and concrete was obtained in the following formulation in examples and tested.

Comparative example 1

The raw materials for preparing the recycled concrete comprise, by weight, 40 parts of cement, 20 parts of recycled concrete micropowder, 20 parts of glass powder, 20 parts of fly ash, 200 parts of natural coarse aggregate, 200 parts of fine aggregate, 1 part of water reducing agent, 40 parts of water and stainless steel fiber with the volume mixing amount of 1.5%.

Preparing cement, recycled concrete micro powder, glass powder, fly ash, natural coarse aggregate, fine aggregate, polycarboxylic acid water reducing agent, water and stainless steel fiber according to the proportion. And pouring the natural coarse aggregate, the fine aggregate and the stainless steel fiber into a stirrer, and stirring for 100 s. And pouring the cement, the recycled concrete micro powder, the glass powder and the fly ash into a stirrer, stirring for 70s, then uniformly mixing the polycarboxylic acid water reducing agent and 70% of water, pouring into the stirrer, stirring for 60s, finally pouring the rest 30% of water, continuously stirring until the mixture is uniform, and pouring out and forming to obtain the recycled concrete.

Comparative example 2

The raw material mixture ratio of the prepared recycled concrete is as follows, and the raw material mixture ratio comprises 40 parts of cement, 20 parts of recycled concrete micro powder, 20 parts of glass powder, 20 parts of fly ash, 20 parts of unmodified recycled coarse aggregate, 180 parts of natural coarse aggregate, 200 parts of fine aggregate, 1 part of water reducing agent, 40 parts of water and stainless steel fiber with the volume mixing amount of 1.5 percent.

Preparing cement, recycled concrete micro powder, glass powder, fly ash, natural coarse aggregate, fine aggregate, polycarboxylic acid water reducing agent, water and stainless steel fiber according to the proportion. And pouring the natural coarse aggregate, the fine aggregate and the stainless steel fiber into a stirrer, and stirring for 100 s. And pouring the cement, the recycled concrete micro powder, the glass powder and the fly ash into a stirrer, stirring for 70s, then uniformly mixing the polycarboxylic acid water reducing agent and 70% of water, pouring into the stirrer, stirring for 60s, finally pouring the rest 30% of water, continuously stirring until the mixture is uniform, and pouring out and forming to obtain the recycled concrete.

Example 1

The raw materials for preparing the recycled concrete are as follows, and the recycled concrete comprises, by weight, 40 parts of cement, 20 parts of recycled concrete micropowder, 20 parts of glass powder, 20 parts of fly ash, 20 parts of modified recycled coarse aggregate, 180 parts of natural coarse aggregate, 200 parts of fine aggregate, 1 part of water reducing agent, 40 parts of water and stainless steel fiber with the volume mixing amount of 1.5%.

Preparing cement, recycled concrete micro powder, glass powder, fly ash, modified recycled coarse aggregate, natural coarse aggregate, fine aggregate, polycarboxylic acid water reducing agent, water and stainless steel fiber according to the proportion. And pouring the natural coarse aggregate, the fine aggregate and the stainless steel fiber into a stirrer, and stirring for 110 s. And pouring the cement, the recycled concrete micro powder, the glass powder and the fly ash into a stirrer, stirring for 50s, then uniformly mixing the polycarboxylic acid water reducing agent and 70% of water, pouring into the stirrer, stirring for 60s, finally pouring the rest 30% of water, continuously stirring until the mixture is uniform, and pouring out and forming to obtain the recycled concrete.

Example 2

The raw materials for preparing the recycled concrete are as follows, and the recycled concrete comprises, by weight, 40 parts of cement, 20 parts of recycled concrete micropowder, 20 parts of glass powder, 20 parts of fly ash, 40 parts of modified recycled coarse aggregate, 160 parts of natural coarse aggregate, 200 parts of fine aggregate, 1 part of water reducing agent, 40 parts of water and stainless steel fiber with the volume mixing amount of 1.5%.

Preparing cement, recycled concrete micro powder, glass powder, fly ash, modified recycled coarse aggregate, natural coarse aggregate, fine aggregate, polycarboxylic acid water reducing agent, water and stainless steel fiber according to the proportion. And (3) pouring the natural coarse aggregate, the fine aggregate and the stainless steel fiber into a stirrer, and stirring for 120 s. And pouring the cement, the recycled concrete micro powder, the glass powder and the fly ash into a stirrer, stirring for 70s, then uniformly mixing the polycarboxylic acid water reducing agent and 70% of water, pouring into the stirrer, stirring for 60s, finally pouring the rest 30% of water, continuously stirring until the mixture is uniform, and pouring out and forming to obtain the recycled concrete.

Example 3

The raw materials for preparing the recycled concrete comprise, by weight, 40 parts of cement, 20 parts of recycled concrete micropowder, 20 parts of glass powder, 20 parts of fly ash, 60 parts of modified recycled coarse aggregate, 140 parts of natural coarse aggregate, 200 parts of fine aggregate, 1 part of water reducing agent, 40 parts of water and stainless steel fiber with the volume mixing amount of 1.5%.

Preparing cement, recycled concrete micro powder, glass powder, fly ash, modified recycled coarse aggregate, natural coarse aggregate, fine aggregate, polycarboxylic acid water reducing agent, water and stainless steel fiber according to the proportion. And pouring the natural coarse aggregate, the fine aggregate and the stainless steel fiber into a stirrer, and stirring for 110 s. And pouring the cement, the recycled concrete micro powder, the glass powder and the fly ash into a stirrer, stirring for 60s, then uniformly mixing the polycarboxylic acid water reducing agent and 70% of water, pouring into the stirrer, stirring for 80s, finally pouring the rest 30% of water, continuously stirring until the mixture is uniform, and pouring out and forming to obtain the recycled concrete.

Example 4

The raw materials for preparing the recycled concrete are as follows, and the recycled concrete comprises, by weight, 40 parts of cement, 20 parts of recycled concrete micropowder, 20 parts of glass powder, 20 parts of fly ash, 80 parts of modified recycled coarse aggregate, 120 parts of natural coarse aggregate, 200 parts of fine aggregate, 1 part of water reducing agent, 40 parts of water and stainless steel fiber with the volume mixing amount of 1.5%.

Preparing cement, recycled concrete micro powder, glass powder, fly ash, modified recycled coarse aggregate, natural coarse aggregate, fine aggregate, polycarboxylic acid water reducing agent, water and stainless steel fiber according to the proportion. And (3) pouring the natural coarse aggregate, the fine aggregate and the stainless steel fiber into a stirrer, and stirring for 120 s. And pouring the cement, the recycled concrete micro powder, the glass powder and the fly ash into a stirrer, stirring for 50s, then uniformly mixing the polycarboxylic acid water reducing agent and 70% of water, pouring into the stirrer, stirring for 70s, finally pouring the rest 30% of water, continuously stirring until the mixture is uniform, and pouring out and forming to obtain the recycled concrete.

Example 5

The raw materials for preparing the recycled concrete are as follows, and the recycled concrete comprises, by weight, 40 parts of cement, 20 parts of recycled concrete micropowder, 20 parts of glass powder, 20 parts of fly ash, 100 parts of modified recycled coarse aggregate, 100 parts of natural coarse aggregate, 200 parts of fine aggregate, 1 part of water reducing agent, 40 parts of water and stainless steel fiber with the volume mixing amount of 1.5%.

Preparing cement, recycled concrete micro powder, glass powder, fly ash, modified recycled coarse aggregate, natural coarse aggregate, fine aggregate, polycarboxylic acid water reducing agent, water and stainless steel fiber according to the proportion. And pouring the natural coarse aggregate, the fine aggregate and the stainless steel fiber into a stirrer, and stirring for 100 s. And pouring the cement, the recycled concrete micro powder, the glass powder and the fly ash into a stirrer, stirring for 60s, then uniformly mixing the polycarboxylic acid water reducing agent and 70% of water, pouring into the stirrer, stirring for 60s, finally pouring the rest 30% of water, continuously stirring until the mixture is uniform, and pouring out and forming to obtain the recycled concrete.

Performance testing

The concrete test blocks prepared in the above examples and comparative examples were subjected to a compressive strength test in accordance with GB/T50081-2002 Standard for testing mechanical Properties of general concrete, and the results are shown in the following table and FIG. 1.

As can be seen from the data of table 1 and fig. 1, compared to comparative example 1, the mechanical properties of the recycled concrete obtained by replacing a part of the natural coarse aggregate in each example with the modified recycled coarse aggregate prepared by the method of the present invention are significantly better than those of comparative example 1, while the mechanical properties are rather significantly reduced when the unmodified recycled coarse aggregate is used as a concrete raw material; and the data of each embodiment show that the mechanical property of the recycled concrete is improved along with the improvement of the proportion of the regenerative coarse aggregate, so that the adoption of the modified regenerative coarse aggregate not only eliminates the structural defect of the regenerative coarse aggregate, but also can improve the mechanical property of the regenerative concrete.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.