Lightweight mortar and preparation method thereof

Abstract

The invention provides light mortar and a preparation method thereof. The light mortar is prepared from the following raw materials in parts by weight: 360-600 parts of waste autoclaved aerated concrete block recycled aggregate, 75-195 parts of cement, 15-60 parts of fly ash, 85-280 parts of water and 8-13 parts of a water reducing agent. The preparation method comprises the following steps: preparing the waste autoclaved aerated concrete block recycled aggregate; and preparing the mortar mixture. The problem of recycling of the waste autoclaved aerated concrete blocks can be solved, and the application direction of the waste autoclaved aerated concrete blocks is expanded.

Description

Technical Field

[0001] The present application relates to the technical field of construction waste recycling, and in particular to a lightweight mortar using waste autoclaved aerated concrete blocks as recycled aggregate and a preparation method thereof. Background Art

[0002] With the relocation and reconstruction of old urban areas and the implementation of the development and construction plan of new urban areas in my country, the output of construction waste has increased year by year, and the annual demolition waste volume has reached 200 million tons, accounting for 30-40% of the total urban solid waste. However, the current level of construction waste resource utilization technology in my country is backward, and the resource utilization rate is always less than 10%, far lower than 90% in European and American countries and 95% in Japan and South Korea. Therefore, research on the resource utilization of construction waste is urgent.

[0003] Autoclaved aerated concrete blocks have the advantages of low density, good sound insulation and heat preservation, and convenient construction, and are widely used as wall materials. Therefore, demolished construction waste often contains a large proportion of waste autoclaved aerated concrete blocks. Because waste autoclaved aerated concrete blocks have low strength and high water absorption, they are difficult to be used as high-strength grade concrete aggregates. Therefore, there are currently a large number of waste autoclaved aerated concrete blocks in China that are simply backfilled and stacked, causing great harm to the environment. Summary of the invention

[0004] In view of the low resource utilization rate of existing construction waste, the present application provides a lightweight mortar using waste autoclaved aerated concrete blocks as recycled aggregate and a preparation method thereof, so as to improve the resource utilization level of construction waste by reusing waste autoclaved aerated concrete blocks in large amounts.

[0005] In a first aspect of the present application, a lightweight mortar is provided, which is composed of the following raw materials in parts by weight: 360 to 600 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a diameter of 0 to 5 mm (including 5 mm), 75 to 195 parts of cement, 15 to 60 parts of fly ash, 85 to 280 parts of water, and 8 to 13 parts of a water reducing agent.

[0006] Optionally, the particle size of the recycled aggregate of the waste autoclaved aerated concrete block is 0 to 5 mm (including 5 mm), and the apparent density is 2250 to 2350 kg / m 3 .

[0007] Optionally, the cement is 42.5 grade ordinary Portland cement.

[0008] A second aspect of the present application provides a method for preparing a lightweight mortar, comprising the following steps:

[0009] Preparation of recycled aggregate from waste autoclaved aerated concrete blocks: waste autoclaved aerated concrete blocks from the demolition of building structure walls are selected, and the waste autoclaved aerated concrete blocks are crushed and sieved to obtain recycled aggregate particles of waste autoclaved aerated concrete blocks that meet the target particle size;

[0010] Preparation of mixture: the recycled aggregate particles of the waste autoclaved aerated concrete blocks, cement and fly ash are mixed and dispersed, water is added and stirred for 60 seconds, and the sample on the stirring blade and the wall of the stirring container is cleaned for 60 seconds and put into the container, and then the stirring is continued for 60 seconds, and the water reducing agent is added while stirring, and finally the stirring is carried out for 180 seconds to obtain the lightweight mortar.

[0011] Optionally, obtaining recycled aggregate particles for concrete blocks meeting the target particle size includes selecting recycled aggregate particles for concrete blocks having a particle size of 0 to 5 mm (including 5 mm) and performing a pre-wetting treatment.

[0012] Optionally, the water reducing agent is a polycarboxylate water reducing agent with a water reducing rate of 25%.

[0013] Optionally, the lightweight mortar is molded, shaped and cured in sequence.

[0014] Optionally, the curing conditions are: temperature of 18-22° C., humidity ≥90% RH.

[0015] The beneficial effects of the present application are as follows: the present application uses waste autoclaved aerated concrete blocks as fine aggregate to prepare lightweight mortar, which can effectively improve the recycling rate of waste autoclaved aerated concrete blocks and reduce their negative impact on the environment. Reuse as mortar aggregate after recycling reduces the cost of mortar procurement; direct production on the construction site further reduces transportation costs; the mortar can also be further sold, broadening the profit channels. Moreover, the lightweight mortar provided by the present application can be used for structures to effectively reduce the deadweight of the structure, and also has good sound insulation and thermal insulation properties, achieving multiple goals at one stroke.

[0016] The present application provides an optimal mortar component ratio, which can provide lightweight mortar with higher compressive strength and meet the requirements for structure use. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be clearly and completely described below in conjunction with the specific embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0018] Autoclaved aerated concrete blocks are porous silicate blocks made by adding aluminum powder as an air-entraining agent to the ingredients of calcium materials (such as cement, lime) and silicon materials (such as sand, fly ash, slag), adding water and stirring, pouring and molding, gas expansion, pre-curing and cutting, and then curing with high-pressure steam. The unit volume weight of autoclaved aerated concrete blocks is one-third of that of clay bricks, the thermal insulation performance is 3-4 times that of clay bricks, the sound insulation performance is 2 times that of clay bricks, the impermeability is more than double that of clay bricks, and the fire resistance is 6-8 times that of reinforced concrete. Autoclaved aerated concrete blocks are suitable for internal and external filling walls above the ground and internal filling walls below the ground in various types of buildings (except for walls with special requirements). The current main recycling method is to backfill after crushing or transport it as garbage.

[0019] The present invention provides a lightweight mortar using waste autoclaved aerated concrete blocks as recycled aggregate and a preparation method thereof, comprising the following steps: selecting cement and fly ash, selecting waste autoclaved aerated concrete blocks as recycled fine aggregate, completely replacing natural sand, and mixing and forming. The preparation method comprises the following steps: preparing recycled aggregate from waste autoclaved aerated concrete blocks; preparing mortar mixture. The present invention can solve the problem of recycling waste autoclaved aerated concrete blocks and expand the application direction of waste autoclaved aerated concrete blocks.

[0020] The embodiment of the present application provides a lightweight mortar, which is composed of the following raw materials in parts by weight: 360 to 600 parts of recycled aggregate from waste autoclaved aerated concrete blocks, 75 to 195 parts of cement, 15 to 60 parts of fly ash, 85 to 280 parts of water, and 8 to 13 parts of a water reducing agent.

[0021] In one embodiment of the present application, the particle size distribution and apparent density of the recycled aggregate of the waste autoclaved aerated concrete block are measured. The particle size of the recycled aggregate of the waste autoclaved aerated concrete block is 0 to 5 mm (including 5 mm), and the apparent density is 2250 to 2350 kg / m 3 .

[0022] In one embodiment of the present application, the total mass fraction of the cement and fly ash added is 25% to 45% of the recycled aggregate of the waste autoclaved aerated concrete blocks. Further, the mass fraction of the fly ash added is 15% to 25% of the total mass fraction of the cement and fly ash added. Specifically, the lightweight mortar is composed of the following raw materials in parts by weight: 360 to 600 parts of recycled aggregate of 0 to 5 mm (including 5 mm) of waste autoclaved aerated concrete blocks, 75 to 195 parts of cement, 15 to 60 parts of fly ash, 85 to 280 parts of water, and 8 to 13 parts of water reducer.

[0023] In one embodiment of the present application, the added water is in an amount of 80% to 120% by mass of the total mass of cement and fly ash.

[0024] The present application also provides a method for preparing a lightweight mortar, comprising the following steps:

[0025] Preparation of recycled aggregate from waste autoclaved aerated concrete blocks: waste autoclaved aerated concrete blocks from the demolition of building structure walls are selected, and the waste autoclaved aerated concrete blocks are directly crushed and screened at the construction site to obtain recycled aggregate particles of waste autoclaved aerated concrete blocks that meet the target particle size;

[0026] Preparation of mixture: the recycled aggregate particles of the waste autoclaved aerated concrete blocks, cement and fly ash are mixed and dispersed, water is added and stirred for 60 seconds, and the stirring blades and the sample on the wall of the stirring container are cleaned for 60 seconds and the sample is put into the container, and then stirring is continued for 60 seconds. During the 60-second stirring process, the water reducing agent is added while stirring, and the state of the mortar mixture is observed to prevent uneven stirring. Finally, stirring is carried out for 180 seconds to obtain lightweight mortar.

[0027] In one embodiment of the present application, the obtaining of recycled aggregate particles of waste autoclaved aerated concrete blocks meeting the target particle size includes selecting recycled aggregate particles of concrete blocks having a particle size of 0 to 5 mm (including 5 mm) and performing a pre-wetting treatment.

[0028] In one embodiment of the present application, the lightweight mortar is molded, shaped, and cured in sequence.

[0029] In one embodiment of the present application, the curing conditions are: temperature of 18-22° C., humidity ≥90% RH.

[0030] It can be understood that age refers to the time it takes for the mortar to harden from the start of water addition and mixing. 3d refers to 3 days from the start of water addition and mixing. Under normal curing conditions, the strength of the mortar will continue to develop with the increase of age. The strength development is relatively fast in the first 7 to 14 days, and then gradually slows down. The design strength is reached in 28 days, and its strength grade is determined based on the 28d compressive strength. The strength is still developing after 28d, and its growth process can continue for decades. Under standard curing conditions, the development of the mortar strength is roughly proportional to the common logarithm of its age (the age is not less than 3d).

[0031] In the present application, the standard compressive strength and flexural strength of the mortar at 3 days of age are 27.4 MPa and 5.5 MPa, respectively, and the standard compressive strength and flexural strength at 28 days of age are 53.6 MPa and 8.7 MPa, respectively.

[0032] The present application also provides a method for preparing a lightweight mortar specimen, which is implemented by the following steps:

[0033] 1) Use waste autoclaved aerated concrete blocks from the demolition of building structure walls;

[0034] 2) The waste autoclaved aerated concrete blocks are crushed and sieved to obtain recycled fine aggregate with a diameter of 0 to 5 mm;

[0035] 3) Pre-wetting the recycled aggregate of waste autoclaved aerated concrete blocks;

[0036] 4) Mix and disperse the recycled aggregate particles of the waste autoclaved aerated concrete blocks, cement and fly ash, add water and stir for 60 seconds, stop for 60 seconds to clean the stirring blades and the sample on the wall of the stirring container into the container, and then continue to stir for 60 seconds. During the 60-second stirring process, add a water reducer while stirring, and pay attention to observe the state of the mortar mixture to prevent uneven stirring. Finally, stir for 180 seconds to obtain a lightweight mortar;

[0037] 5) Load the lightweight mortar into the mold, compact it using a vibrating table or a manual vibrator, and demold and maintain after forming.

[0038] It should be noted that the raw material component contents in this application include endpoint values, such as 75 to 195 parts of cement, which means: 75 parts ≤ parts by weight of fly ash ≤ 195 parts. Similarly, percentage contents also include endpoint values.

[0039] Example

[0040] In this embodiment, waste autoclaved aerated concrete blocks from the demolition of a building structure wall are selected, and the recycled aggregates of the waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm) are screened after crushing. The apparent density is 2287 kg / m 3 .

[0041] Example 1

[0042] The lightweight mortar in this embodiment is composed of the following ingredients in parts by weight: 360 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm), 114 parts of cement, 30 parts of fly ash, 130 parts of water, and 9 parts of water reducing agent.

[0043] Example 2

[0044] The lightweight mortar in this embodiment is composed of the following ingredients in parts by weight: 360 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm), 96 parts of cement, 24 parts of fly ash, 120 parts of water, and 9 parts of water reducing agent.

[0045] Example 3

[0046] The lightweight mortar in this embodiment is composed of the following ingredients in parts by weight: 360 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm), 80 parts of cement, 20 parts of fly ash, 120 parts of water, and 9 parts of water reducing agent.

[0047] Example 4

[0048] The lightweight mortar in this embodiment is composed of the following ingredients in parts by weight: 360 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm), 75 parts of cement, 20 parts of fly ash, 115 parts of water, and 9 parts of water reducing agent.

[0049] Weigh the raw materials according to the above proportions, mix and disperse the recycled aggregate particles of the waste autoclaved aerated concrete blocks, cement and fly ash, add water and stir for 60 seconds, stop for 60 seconds to clean the stirring blades and the sample on the wall of the stirring container, and then continue to stir for 60 seconds. During this 60-second stirring time, add water reducer while stirring, and pay attention to observe the state of the mortar mixture to prevent uneven stirring. Finally, stir for 180 seconds to obtain lightweight mortar. Put it into the mold and vibrate it on a vibrating table. After forming, demould and maintain for 28 days.

[0050] The lightweight mortar specimens of 28 days old prepared in Examples 1 to 4 were tested for dry density and compressive strength one by one. The test results are shown in Table 1.

[0051] Table 1 Dry density and compressive strength test results

[0052] Serial number Specimen size Sand-to-binder ratio Water-cement ratio <![CDATA[Dry density (Kg / m 3 )]]> Compressive strength(MPa) Example 1 Ф70.7mm*70.7mm 2.5 0.9 891 6.4 Example 2 Ф70.7mm*70.7mm 3 1 757 5.9 Example 3 Ф70.7mm*70.7mm 3.5 1.2 564 3.8 Example 4 Ф70.7mm*70.7mm 3.8 1.2 523 3.5

[0053] It can be seen from Table 1 that the dry density of the lightweight mortar specimens prepared in Examples 1 to 4 is 900 Kg / m 3 Below, the 28-day compressive strength can reach more than 2.5MPa, which can meet the requirements of lightweight dry-mix mortar for construction projects.

[0054] In the above embodiments, the compressive strength of embodiment 1 is the highest and it is a preferred embodiment. Therefore, on the basis of specific embodiment 1, the amount of recycled aggregate is adjusted by the control variable method, and other amounts remain unchanged. The specific proportion is as follows:

[0055] Example 5

[0056] The lightweight mortar in this embodiment is composed of the following components by weight: 432 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm), 114 parts of cement, 30 parts of fly ash, 130 parts of water, and 9 parts of water reducing agent;

[0057] Example 6

[0058] The lightweight mortar in this embodiment is composed of the following components in parts by weight: 504 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm), 114 parts of cement, 30 parts of fly ash, 130 parts of water, and 9 parts of water reducing agent;

[0059] Example 7

[0060] The lightweight mortar in this embodiment is composed of the following ingredients in parts by weight: 547 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm), 114 parts of cement, 30 parts of fly ash, 130 parts of water, and 9 parts of water reducing agent.

[0061] Example 8

[0062] The lightweight mortar in this embodiment is composed of the following ingredients in parts by weight: 600 parts of recycled aggregate of waste autoclaved aerated concrete blocks with a particle size of 0 to 5 mm (including 5 mm), 114 parts of cement, 30 parts of fly ash, 130 parts of water, and 9 parts of water reducing agent.

[0063] The following test results are obtained:

[0064] Table 2 Dry density and compressive strength test results

[0065] Serial number Specimen size Sand-to-binder ratio Water-cement ratio <![CDATA[Dry density (Kg / m 3 )]]> Compressive strength(MPa) Example 5 Ф70.7mm*70.7mm 3 0.9 717 5.7 Example 6 Ф70.7mm*70.7mm 3.5 0.9 521 5.3 Example 7 Ф70.7mm*70.7mm 3.8 0.9 474 4.2 Example 8 Ф70.7mm*70.7mm 3.9 0.9 421 4.0

[0066] It can be seen from the component proportions and test results of Examples 5 to 8 that Example 5 is a preferred example. It can be seen that on the basis of the proportion of Example 1, when the content of recycled aggregate of waste autoclaved aerated concrete blocks is reduced, better compressive strength can be obtained. Further, Example 5 is compared with Basic Example 1, and Example 1 is upgraded to the optimal example of this application, and the obtained test piece can obtain the best compressive strength in this application.

[0067] Since the autoclaved aerated concrete blocks themselves are porous, have good thermal insulation properties and are light in weight, this application recycles them and re-prepares them into mortar for use in plastering and other occasions. This can increase the sound insulation and thermal insulation of the wall. At the same time, the wall hanging is light in weight and not easy to fall off, which also has significant advantages over traditional mortar.

[0068] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A lightweight mortar, characterized in that: The invention is composed of the following raw materials in parts by weight: 360-600 parts of recycled aggregate of waste autoclaved aerated concrete blocks, 75-195 parts of cement, 15-60 parts of fly ash, 85-280 parts of water and 8-13 parts of water reducing agent.

2. A lightweight mortar as claimed in claim 1, characterized in that: The particle size of the recycled aggregate of the waste autoclaved aerated concrete blocks is 0 to 5 mm (including 5 mm), and the apparent density is 2250 to 2350 kg / m 3 .

3. A lightweight mortar as claimed in claim 1, characterized in that: The cement is 42.5 grade ordinary Portland cement.

4. A lightweight mortar according to claim 1, characterized in that: The particle size of the fly ash is 0.1-100 μm.

5. A method for preparing lightweight mortar, characterized in that: The following steps are involved: Preparation of recycled aggregate from waste autoclaved aerated concrete blocks: waste autoclaved aerated concrete blocks from the demolition of building structure walls are selected, and the waste autoclaved aerated concrete blocks are crushed and sieved to obtain recycled aggregate particles of waste autoclaved aerated concrete blocks that meet the target particle size; Preparation of mixture: the recycled aggregate particles of the waste autoclaved aerated concrete blocks, cement and fly ash are mixed and dispersed, water is added and stirred for 60 seconds, and the sample on the stirring blade and the wall of the stirring container is cleaned for 60 seconds and put into the container, and then the stirring is continued for 60 seconds, and the water reducing agent is added while stirring, and finally the stirring is carried out for 180 seconds to obtain the lightweight mortar.

6. A method for preparing a lightweight mortar according to claim 5, characterized in that: Obtaining recycled aggregate particles of waste autoclaved aerated concrete blocks that meet target particle sizes includes selecting recycled aggregate particles of concrete blocks with a particle size of 0 to 5 mm (including 5 mm) and performing pre-wetting treatment.

7. A method for preparing a lightweight mortar according to claim 5, characterized in that: The water reducing agent is a polycarboxylate water reducing agent with a water reducing rate of 25%.

8. A method for preparing a lightweight mortar according to claim 5, characterized in that: The lightweight mortar is molded, shaped and cured in sequence.

9. A method for preparing a lightweight mortar according to claim 8, characterized in that: The curing conditions are as follows: temperature of 18-22° C. and humidity ≥90% RH.