Thermal-insulation recycled concrete block based on building and agricultural wastes and preparation method of thermal-insulation recycled concrete block

Abstract

The invention belongs to the field of concrete solid waste utilization, and discloses a thermal insulation recycled concrete block based on building and agricultural wastes and a preparation method thereof. The heat-insulating recycled concrete block is mainly prepared from the following raw materials: 100 parts of modified recycled primary coarse aggregate, 70-80 parts of modified recycled secondary coarse aggregate, 20-40 parts of modified recycled fine aggregate, 20-30 parts of modified agricultural straw ash, 10 parts of animal dung ash and 10 parts of cement. The preparation method of the heat-insulating recycled concrete block comprises the following steps: mixing the raw materials in proportion, firstly performing dry mixing, and then adding water for stirring to obtain recycled concrete slurry; the concrete slurry is injected into the forming mold for building blocks; and after the building block is formed, maintenance is performed. The thermal-insulation recycled concrete block prepared by the method is high in mechanical strength, small in heat conductivity coefficient and good in thermal insulation performance, and meanwhile, the utilization of waste resources is realized.

Description

Technical Field

[0001] The invention relates to the field of concrete solid waste utilization, and in particular to a thermal insulation recycled concrete building block based on construction and agricultural wastes and a preparation method thereof. Background Art

[0002] For a long time, with the development of the construction industry, while large-scale construction is being carried out, a large number of old buildings have been demolished and abandoned, resulting in the accumulation of abandoned buildings. The common means of dealing with abandoned buildings is crushing and landfilling, which causes certain pollution to the natural environment such as water bodies, soil and atmosphere. Recycling abandoned buildings into recycled aggregates can not only reduce environmental pollution and protect arable land, but also reduce dependence on natural aggregates, thereby achieving the purpose of protecting the ecological environment. At the same time, farmland straw is mostly used as household fuel, and the ash powder after incineration is also treated as garbage, which also causes waste of resources and environmental pollution.

[0003] Thermal insulation concrete is a special type of concrete with relatively low thermal conductivity that can reduce heat dissipation. Insulation materials such as polystyrene particles and silica aerogel are often added to its composition to improve the thermal insulation performance of concrete. However, this thermal insulation concrete does not conform to my country's transformation direction towards green industrialization. There are few reports in the prior art on combining straw biomass materials with waste concrete to prepare thermal insulation concrete blocks.

[0004] Patent CN 108726956A discloses a modified recycled concrete, which contains 100 parts of cement, 235-260 parts of recycled aggregate, 145-165 parts of sand, 35-45 parts of water, 3-10 parts of silica fume, 0.5-2.5 parts of nano-silicon dioxide, 0.5-2.5 parts of water reducer, and 0.5-1.5 parts of cellulose ether. Among the raw material components in the concrete, the recycled aggregate is not chemically treated and graded, and the strength and durability of the obtained recycled concrete are low.

[0005] For the construction industry, the building materials it needs consume a lot of cement, stone sand and other resources, and these building materials also have a lot of and quite serious pollution links in the production process. Based on this, the development of a thermal insulation recycled concrete block made from construction and agricultural waste and its preparation method has extremely high application value. Summary of the invention

[0006] In view of the problems and shortcomings in the prior art, the present invention aims to provide a thermal insulation recycled concrete block based on construction and agricultural waste and a preparation method thereof.

[0007] In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is as follows:

[0008] A thermal insulation recycled concrete block based on construction and agricultural waste, mainly made of the following raw materials:

[0009] 100 parts of modified recycled primary coarse aggregate, 70-80 parts of modified recycled secondary coarse aggregate, 20-40 parts of modified recycled fine aggregate, 20-30 parts of modified agricultural straw ash, 10 parts of animal dung ash, and 10 parts of cement;

[0010] The modified recycled primary coarse aggregate is made of waste concrete with a particle size of 5 to 10 mm, which is ultrasonically infiltrated with a NaOH solution and a modified water glass solution and then dried;

[0011] The modified recycled secondary coarse aggregate is made of waste concrete with a particle size of 10 to 15 mm, which is ultrasonically infiltrated with a NaOH solution and a modified water glass solution and then dried;

[0012] The modified recycled fine aggregate is made of waste concrete with a particle size of less than 5 mm, which is ultrasonically impregnated with a NaOH solution and a triisopropanolamine solution of chopped jute fibers, and then dried;

[0013] The modified agricultural straw ash is prepared by crushing, calcining and screening agricultural straw, and then soaking in a NaOH solution and then modified with a KH570 solution.

[0014] Preferably: 70 parts of modified recycled secondary coarse aggregate and 30-40 parts of modified recycled fine aggregate.

[0015] The modified water glass solution is a water glass solution to which silicon nitride particles are added, and the silicon nitride particles account for 15% of the mass of the modified water glass solution.

[0016] The concentration of the NaOH solution used in forming the modified recycled primary coarse aggregate, the modified recycled secondary coarse aggregate and the modified recycled fine aggregate is 2% to 5%, and the concentration of the NaOH solution used in forming the modified agricultural straw ash is 4%.

[0017] The content of the chopped jute fibers in the triisopropanolamine solution of chopped jute fibers is 5% to 8% of the mass of the triisopropanolamine solution.

[0018] The concentration of the KH570 solution is 5%.

[0019] The waste concrete is subjected to microwave irradiation treatment before modification, the microwave radiation intensity is 750-1000W, and the irradiation time is 30 minutes.

[0020] The animal dung ash is obtained by drying the animal dung in the sun, calcining at a constant temperature of 600-800° C. for 2 hours, naturally cooling, immersing in an aqueous solution containing bentonite for deodorization treatment for 24 hours, and drying.

[0021] Preferably, the waste concrete is crushed building component materials or waste masonry materials; the agricultural straw is one or more of rice straw, cotton straw, corn straw and wheat straw.

[0022] A method for preparing a thermal insulation recycled concrete block comprises the following steps:

[0023] (1) Mixing: Mix cement, modified recycled primary coarse aggregate, modified recycled secondary coarse aggregate, modified recycled fine aggregate, modified agricultural straw ash and animal dung ash raw materials in sequence, and dry mix at a speed of 100-150 r / min for 8 minutes; then add water and stir at a speed of 200-300 r / min for 30 minutes to obtain recycled concrete slurry;

[0024] (2) Block forming: injecting concrete slurry into the forming mold;

[0025] (3) Curing: After the blocks are formed, they are cured at 25°C for 6 hours, then slowly heated to 90°C and cured for 48 hours, then slowly cooled to 20°C and cured at RH≧95% for 28 days.

[0026] The water-cement ratio in step (1) is 0.42.

[0027] In step (1), 1 to 2 parts of a high-performance water-reducing agent are also added, and the high-performance water-reducing agent is a polycarboxylic acid water-reducing agent.

[0028] Preferably, before the building blocks are formed in step (2), a layer of release agent is applied to the surface of the forming mold.

[0029] Preferably, after the curing process in step (3) is completed, a layer of hydrophobic agent may be applied.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] (1) The present invention adopts the modified recycled coarse aggregate and modified recycled fine aggregate formed after the waste concrete is crushed, screened and modified to replace the existing natural aggregate and fine sand, and is equipped with a very small amount of cementitious material cement, which not only greatly reduces the large-scale use of fine sand, natural coarse aggregate and cement, but also makes full use of waste concrete resources, and maximizes the "waste into treasure" of waste concrete and realizes secondary utilization. The raw material source of the present invention is rich, the cost is low, and the reuse of construction and agricultural waste is realized to the greatest extent. The obtained concrete blocks also have excellent thermal insulation performance and can be used for partition walls of buildings, etc.

[0032] (2) The present invention performs microwave radiation treatment on waste concrete, and microwave radiation is more conducive to the detachment of mortar on the surface of recycled aggregate than conventional heating; recycled fine aggregate and recycled primary coarse aggregate and recycled secondary coarse aggregate are respectively subjected to modification treatments of different processes, wherein the recycled fine aggregate is placed in a triisopropanolamine solution dispersed with chopped jute fibers, and the jute fibers have a large surface roughness, so that the tensile strength and bonding properties of the modified recycled fine aggregate are greatly improved, and the impregnation of the triisopropanolamine solution also improves the volcanic ash reaction and improves the compressive properties; the recycled primary coarse aggregate and the recycled secondary coarse aggregate are immersed in a water glass solution dispersed with silicon nitride particles, which not only greatly improves the bonding properties of the aggregate surface, but also strengthens the wear resistance of the aggregate with silicon nitride, and the mechanical strength of the modified recycled aggregate after treatment is not lower than that of the natural aggregate.

[0033] (3) The modified agricultural straw ash of the present invention is prepared by high-temperature calcination of agricultural straw, treatment with NaOH solution and KH570 solution, and the bonding strength with the cementitious material is also greatly improved, and the mechanical strength of the concrete block is not affected. Animal dung ash has higher volcanic ash properties than conventional dung ash. The present invention combines animal dung ash with modified agricultural straw ash and uses them in the production of recycled concrete to obtain concrete blocks with equivalent performance to that of concrete made of natural aggregates. This is due to the fact that animal dung ash and crop straw contain rich compounds such as SiO2, Al2O3 and CaO, have extremely high volcanic ash effects, can react chemically with cement hydration products to form new gels, and can effectively enhance the strength of cementitious materials, thereby greatly improving the performance of cement-based materials, and preparing cement-based materials with high mechanical strength, low thermal conductivity and good thermal insulation performance. The treated crop straw and dung ash have better bonding with the modified recycled aggregate. Combining crop straw and animal dung ash in concrete mortar can reduce energy loss rate and meet the requirements of energy-saving, low-carbon and environmentally friendly building materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A process flow chart of the method for preparing the thermal insulation recycled concrete building block of the present invention. DETAILED DESCRIPTION

[0035] (I) Effect of different weight proportions of raw materials on the performance of concrete blocks in Examples 1-14

[0036] A thermal insulation recycled concrete block based on construction and agricultural waste is mainly made of the following raw materials: modified recycled primary coarse aggregate, modified recycled secondary coarse aggregate, modified recycled fine aggregate, modified agricultural straw ash, animal dung ash, P.O52.5 ordinary Portland cement. The specific raw material composition is shown in Table 1.

[0037] The preparation method of the modified recycled primary coarse aggregate, the modified recycled secondary coarse aggregate and the modified recycled fine aggregate is as follows:

[0038] (1) Repeatedly crush the waste concrete from broken building components;

[0039] (2) The crushed waste concrete is subjected to microwave radiation treatment with a radiation intensity of 750-1000W and a radiation time of 30 minutes;

[0040] (3) The irradiated waste concrete fragments are repeatedly crushed and sieved using a vibrating screen with mesh sizes of 15 mm, 10 mm, and 5 mm to obtain recycled fine aggregate with a particle size of less than 5 mm, recycled primary coarse aggregate with a particle size of 5-10 mm, and recycled secondary coarse aggregate with a particle size of 10-15 mm;

[0041] (4) The recycled fine aggregate, recycled primary coarse aggregate, and recycled secondary coarse aggregate were immersed in a 5% NaOH solution and ultrasonically immersed for 24 hours;

[0042] (5) The recycled fine aggregate was then placed in a triisopropanolamine solution dispersed with 8% by mass of chopped jute fibers; the recycled primary coarse aggregate and the recycled secondary coarse aggregate were respectively immersed in a modified water glass solution added with 15% by mass of silicon nitride particles, and then ultrasonically infiltrated for 24 hours and dried for later use.

[0043] The preparation method of the modified agricultural straw ash is:

[0044] (1) Crush the rice straw into small pieces of 5-15 mm in a crusher, then calcine in a muffle furnace at a constant temperature of 500-550° C. for 3-5 h, and sieve through a 50-mesh screen;

[0045] (2) Pour the sieved agricultural straw ash into a 4% NaOH solution and soak for 24 hours;

[0046] (3) The agricultural straw ash soaked with NaOH was placed in a 5% KH570 solution, stirred for 30 minutes for modification, and then placed in a forced air drying oven at a constant temperature of 60°C for drying.

[0047] The animal dung ash treatment method comprises: drying the animal dung, calcining it in a muffle furnace at a constant temperature of 600-800° C. for 2 hours, cooling it naturally, immersing it in an aqueous solution containing bentonite for deodorization treatment for 24 hours, and drying it for later use.

[0048] The chemical composition of the animal dung ash is: SiO2 60.8%, Al2O3 8.36%, CaO 12.4%, K2O 4.35%, Fe2O3 4.2%, MgO 3.1%, and the remainder is impurities.

[0049] The preparation method of the above-mentioned thermal insulation recycled concrete blocks, the process of which is shown in Figure 1, including the following steps:

[0050] (1) Mixing: pour cement into a mixer, then pour modified recycled primary coarse aggregate, modified recycled secondary coarse aggregate, modified recycled fine aggregate, modified agricultural straw ash and animal dung ash into the mixer in sequence, and dry mix at a speed of 100-150 r / min for 8 min; then add water and 2 parts of high-performance polycarboxylate water reducer according to a water-cement ratio of 0.42, and mix at 200-300 r / min for 30 min to obtain recycled concrete slurry;

[0051] (2) Block forming: The concrete slurry is injected into a forming mold, which is a cube with a side length of 150 mm;

[0052] (3) Curing: After the blocks are formed, they are cured at 25°C for 6 hours, then slowly heated to 90°C and cured for 48 hours, then slowly cooled to 20°C and cured at RH≧95% for 28 days.

[0053] The performance of the thermal insulation recycled concrete blocks prepared in Examples 1-14 was tested, and the results are shown in Table 1.

[0054] Table 1 Raw material composition and performance test table of thermal insulation recycled concrete blocks of Examples 1 to 14

[0055]

[0056] The thermal insulation recycled concrete blocks prepared in Examples 1 to 3 have 20, 30 and 40 parts by weight of modified recycled fine aggregate respectively, and the weight of other raw materials are the same. From the data in Table 1, it can be seen that the thermal insulation recycled concrete blocks with 30 and 40 parts by weight of modified recycled fine aggregate have better overall mechanical properties of compressive strength and splitting strength, smaller thermal conductivity, and better thermal insulation performance, which are better than the thermal insulation recycled concrete blocks with 20 parts by weight of modified recycled fine aggregate.

[0057] By comparing the data of Examples 1 and 4, 2 and 5, and 3 and 6, it can be seen that the compressive strength, splitting strength and thermal insulation performance of the thermal insulation recycled concrete block when the weight portion of the modified recycled secondary coarse aggregate is 70 parts are better than those of the thermal insulation recycled concrete block when the weight portion of the modified recycled secondary coarse aggregate is 80 parts, indicating that reducing the content of modified recycled secondary coarse aggregate can improve the compressive strength, splitting strength and thermal insulation performance of the block.

[0058] By comparing the data of Examples 1 and 7, 2 and 8, 3 and 9, 4 and 10, 5 and 11, and 6 and 12, it can be seen that when the weight portion of modified agricultural straw ash is 20 parts, the overall mechanical properties of the concrete block are better, but when the weight portion of agricultural straw ash is 30 parts, the thermal conductivity is lower and the thermal insulation performance of the concrete block is better.

[0059] In Table 1, Example 13-14 is a control group without adding animal dung ash. Example 13-14 is compared with Example 8-9 with the same weight of other raw materials. The mechanical strength and thermal insulation effect of the concrete blocks without adding animal dung ash are worse than those with adding animal dung ash. The introduction of animal dung ash greatly improves the mechanical strength and thermal insulation performance of concrete blocks. This is because animal dung ash contains rich compounds such as SiO2, Al2O3 and CaO, has a very high volcanic ash effect, can react chemically with cement hydration products to form new gel, and can effectively enhance the strength of cementitious materials, thereby greatly improving the performance of cement-based materials. The thermal conductivity of Example 8-9 is 0.040-0.041 (W / mk), which is comparable to the thermal conductivity of existing polystyrene / polyurethane insulation materials. Compared with polystyrene / polyurethane insulation materials, the concrete blocks of the present invention are more environmentally friendly and realize the reuse of construction and agricultural waste to the greatest extent.

[0060] (II) Effects of different recycled aggregate modification methods on concrete blocks

[0061] The recycled aggregate was subjected to three different modification treatments, which were respectively recorded as treatment method A, treatment method B, and treatment method C.

[0062] Treatment method A: The recycled fine aggregate, recycled primary coarse aggregate and recycled secondary coarse aggregate are all immersed in a triisopropanolamine solution containing 8% by mass of chopped jute fiber.

[0063] Treatment method B: The recycled fine aggregate, recycled primary coarse aggregate and recycled secondary coarse aggregate are all immersed in a modified water glass solution in which silicon nitride particles are dispersed at a mass fraction of 15%.

[0064] Treatment method C: The recycled fine aggregate is placed in a triisopropanolamine solution dispersed with chopped jute fibers, while the recycled primary coarse aggregate and the recycled secondary coarse aggregate are immersed in a modified water glass solution dispersed with 15% by mass silicon nitride particles.

[0065] In Example 9, treatment method C is adopted.

[0066] Embodiment 15

[0067] The composition and dosage of raw materials are basically the same as those in Example 9, except that the recycled fine aggregate, recycled primary coarse aggregate, and recycled secondary coarse aggregate are processed using treatment method A.

[0068] Example 16

[0069] The composition and dosage of raw materials are basically the same as those in Example 9, except that the recycled fine aggregate, recycled primary coarse aggregate, and recycled secondary coarse aggregate are processed using treatment method B.

[0070] The concrete blocks prepared in Example 9 and Examples 15 to 16 were tested for performance, and the results are shown in Table 2:

[0071] Table 2 Performance parameters of recycled aggregates under different modification processes

[0072]

[0073] By comparison, it was found that the recycled fine aggregate and recycled primary coarse aggregate and recycled secondary coarse aggregate were treated with different processes respectively. Compared with a single treatment, the compressive strength and splitting strength were very different, and the thermal conductivity was basically unaffected. This is because the performance of aggregates of different gradations is different. The recycled fine aggregate is placed in a triisopropanolamine solution dispersed with chopped jute fibers. The jute fibers use their own surface roughness and toughness to greatly improve the tensile strength and bonding properties of the aggregate; the impregnation of triisopropanolamine solution improves the volcanic ash reaction and improves the compressive performance; the recycled primary coarse aggregate and recycled secondary coarse aggregate are immersed in a modified water glass solution dispersed with 15% by mass silicon nitride particles. The water glass solution not only greatly improves the bonding properties of the aggregate surface, but the silicon nitride particles also adhere to the aggregate surface to strengthen the wear resistance of the aggregate. The recycled aggregate after this special treatment is not lower than the natural aggregate in mechanical strength, can completely replace natural aggregate, and greatly reduce the use of fine sand and natural coarse aggregate.

[0074] Existing partition wall blocks are mostly made of ordinary concrete and do not have thermal insulation properties. The concrete of the present invention not only effectively combines and utilizes construction and agricultural wastes, but also has low cost and excellent thermal insulation properties. It is very suitable for partition wall blocks of northern residences and is worthy of promotion.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A thermal insulation recycled concrete block based on construction and agricultural waste, characterized in that: It is mainly made of the following raw materials: 100 parts of modified recycled primary coarse aggregate, 70-80 parts of modified recycled secondary coarse aggregate, 20-40 parts of modified recycled fine aggregate, 20-30 parts of modified agricultural straw ash, 10 parts of animal dung ash, and 10 parts of cement; The modified recycled primary coarse aggregate is made of waste concrete with a particle size of 5 to 10 mm, which is ultrasonically infiltrated with a NaOH solution and a modified water glass solution and then dried; The modified recycled secondary coarse aggregate is made of waste concrete with a particle size of 10 to 15 mm, which is ultrasonically infiltrated with a NaOH solution and a modified water glass solution and then dried; The modified recycled fine aggregate is made of waste concrete with a particle size of less than 5 mm, which is ultrasonically impregnated with a NaOH solution and a triisopropanolamine solution of chopped jute fibers, and then dried; The modified agricultural straw ash is prepared by crushing, calcining and screening agricultural straw, and then soaking in a NaOH solution and then modified with a KH570 solution.

2. The thermal insulation recycled concrete block according to claim 1, characterized in that: The modified water glass solution is a water glass solution to which silicon nitride particles are added, and the silicon nitride particles account for 15% of the mass of the modified water glass solution.

3. The thermal insulation recycled concrete block according to claim 1, characterized in that: The concentration of the NaOH solution used in forming the modified recycled primary coarse aggregate, the modified recycled secondary coarse aggregate and the modified recycled fine aggregate is 2% to 5%, and the concentration of the NaOH solution used in forming the modified agricultural straw ash is 4%.

4. The thermal insulation recycled concrete block according to claim 3, characterized in that: The content of the chopped jute fibers in the triisopropanolamine solution of chopped jute fibers is 5% to 8% of the mass of the triisopropanolamine solution.

5. The thermal insulation recycled concrete block according to claim 3, characterized in that: The concentration of the KH570 solution is 5%.

6. The thermal insulation recycled concrete block according to claim 1 or 5, characterized in that: The waste concrete is first subjected to microwave irradiation treatment before modification.

7. The thermal insulation recycled concrete block according to claim 1, characterized in that: The animal dung ash is obtained by drying the animal dung in the sun, calcining at a constant temperature of 600-800° C. for 2 hours, naturally cooling, immersing in an aqueous solution containing bentonite for deodorization treatment for 24 hours, and drying.

8. A method for preparing the thermal insulation recycled concrete block according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Mixing: Mix cement, modified recycled primary coarse aggregate, modified recycled secondary coarse aggregate, modified recycled fine aggregate, modified agricultural straw ash and animal dung ash raw materials in sequence, and dry mix at a speed of 100-150 r / min for 8 minutes; then add water and stir at a speed of 200-300 r / min for 30 minutes to obtain recycled concrete slurry; (2) Block forming: injecting concrete slurry into the forming mold; (3) Curing: After the blocks are formed, they are cured at 25°C for 6 hours, then slowly heated to 90°C and cured for 48 hours, then slowly cooled to 20°C and cured at RH≧95% for 28 days.

9. The method for preparing the thermal insulation recycled concrete block according to claim 8, characterized in that: In step (1), the water-cement ratio is 0.42.

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