Concrete and preparation method thereof

Abstract

The invention relates to concrete and a preparation method thereof. The concrete is prepared from the following components in parts by mass: 450 to 550 parts of ceramsite, 350 to 450 parts of cement and 20 to 150 parts of fly ash, the particle size of the ceramsite is 0-5 mm. The preparation method of the concrete comprises the following steps: S1, mixing a gelling mixture with the ceramsite to obtain a dry powder mixture; the gelling mixture comprises the cement and the fly ash; and S2, mixing the dry powder mixture with the water. The concrete provided by the invention has low dry density and high compressive strength, can be used as a building structure material, and has very low heat conductivity coefficient.

Description

Technical Field

[0001] The invention relates to concrete and a preparation method thereof. Background Art

[0002] Currently, concrete building envelopes primarily utilize structural walls combined with insulation, or self-insulating infill walls (such as aerated concrete blocks). However, both structures present certain drawbacks. 1. In the structural wall combined with insulation structure, reinforced concrete serves as the primary load-bearing component, and strength is paramount. However, the strength of reinforced concrete in existing building structures is generally greater than 30 MPa, with a thermal conductivity of 1, making its insulation performance essentially negligible. This results in a significant waste of space and consumes a significant amount of wall thickness. 2. External insulation offers limited safety performance. Insulation layers are categorized as internal and external insulation. Long-term engineering practice has shown that external insulation, without a curtain wall-like stud structure, can be easily delaminated within a few years by simply attaching the insulation to the concrete structure. Thermal expansion and contraction reduce the adhesion of the adhesive mortar, leading to potential detachment within a few years and significant safety risks. 3. Internal insulation eliminates the risk of detachment from high altitudes, but increases the protected area, reduces the usable area, and is more difficult to control thermal bridges than with external insulation, resulting in increased energy consumption. 4. Generally, the thickness of two enclosure structures is inconsistent under the same wall thermal conductivity. When there are multiple exterior wall enclosure forms in the same building, there will be certain overlap problems. Due to the certain misalignment of the overlap boundary, it is difficult to smooth the boundary and heat treatment. 5. Self-insulating walls, such as common autoclaved aerated concrete blocks, generally have a thermal conductivity of 0.10-0.20 W / (m·K), but are relatively low in strength, generally 2.5 MPa to 10 MPa. They can only be used as non-load-bearing enclosure structures, and their own thermal insulation performance cannot meet the wall thermal conductivity requirements. Generally, they still need to be used in combination with internal and external insulation. However, their own strength is relatively low, which makes it more inconvenient to attach internal and external insulation. For example, when using anchor bolts to fix the insulation material, due to the weak nail holding force of aerated concrete blocks, they generally need to be anchored deeper than concrete.

[0003] Patent CN105330244B proposes a method for preparing a phosphorus-based, highly fluid, lightweight thermal insulation wall material. The method includes pre-wetting shale ceramsite, mixing the raw materials, and slurrying. This method improves the comprehensive utilization rate of phosphorus solid waste and reduces environmental pollution. The dry density is ≤1000 kg / m 3, 28-day compressive strength ≥5 MPa, thermal conductivity ≤0.23 W / (m·K). Patent CN107265964B proposes a super-insulating aerogel foamed concrete and its preparation method, which is mainly composed of aerogel powder and foamed concrete. The aerogel powder is composed of an internal hydrophobic layer and a surface hydrophilic layer. The preparation method includes the steps of aerogel powder modification, mixing and stirring. The thermal conductivity is 0.03-0.09 W / m·K and the compressive strength is 0.5-15.0 MPa. Patent CN103724048B proposes a wall self-insulating porous brick made of raw materials such as expanded clay, ceramic sand, cinder powder, and cementitious materials. No retarder or plasticizer is required. The block density is ≤800 kg / m 3 , equivalent thermal conductivity ≤ 0.18 W / m·K, strength ≥ 5.0 MPa. Patent CN102936936B proposes a decorative thermal insulation integrated lightweight concrete board and its production method. The board is composed of a decorative concrete surface layer and a microporous concrete insulation layer, and has a decorative texture. Dry density 580-790 kg / m 3 , thermal conductivity: 0.1-0.15 W / (m·K), compressive strength 5-9 MPa. Patent CN113563021A proposes a lightweight concrete, which consists of lightweight concrete, including cement, quartz powder, vitrified microspheres, ceramsite, graphite, foaming agent, foam stabilizer, cement enhancer, redispersible latex powder, cellulose ether, water reducer and water. The concrete has the characteristics of light weight, high strength and low thermal conductivity. The above patent has a compressive strength of 2.5-3.5 MPa, a tensile strength of 0.3-0.4 MPa, and a bulk density of 500-550 kg / m 3 , with a thermal conductivity of 0.14-0.16 W / (m·K). The above patents further reduce the thermal conductivity by using different material ratios, but they all have the same characteristics of foaming and adding hollow materials such as aerogel, PE, and glass microspheres. This does not improve the strength, and the process is complex and costly.

[0004] Patent CN110056116B proposes an environmentally friendly, energy-saving, and cold-resistant large-scale wall panel and its production method, in which the lightweight concrete uses shale ceramsite concrete, which contains lightweight coarse aggregate, cementitious materials, fine aggregate, auxiliary materials, waterproofing agents, and water reducers. Example 1: compressive strength 27.5 MPa, Example 2: compressive strength 25.45 MPa, Example 3: compressive strength 23.55 MPa, Example 4: compressive strength 20.05 MPa, thermal conductivity 0.1-0.15 W / (m·K). Patent CN102690127B proposes a method for preparing lightweight wall materials, using fly ash, cement, sand, ceramsite and other raw materials, and preparing lightweight wall materials through the steps of stirring, placing in the mold, vibrating, grooving and core extraction, steam curing, etc. Low cost, simple operation, light weight, and good thermal insulation performance. Thermal conductivity 0.18 W / m·K (Example 1), concrete density 1350 Kg / m 3 (Example 1). Patent CN112062597B proposes a lightweight concrete comprising ceramsite, perlite, sulfoaluminate cement, polyvinyl alcohol, polypropylene fiber, and water. By mixing in specific proportions, the synergistic effect of the raw materials is brought into play. Compressive strength: up to 20 MPa, sound insulation: 40 decibels, thermal conductivity coefficient 0.08 W / (m·K). The above patents are based on basic lightweight concrete. Through scientific proportioning, raw material processing, molding and curing, etc., the strength is partially increased to 20-30 MPa and the thermal conductivity is reduced to below 0.10 W / (m·K), but it still does not meet the structural strength requirements.

[0005] Patent CN112250370B proposes a lightweight concrete and its production process, primarily composed of lightweight fine aggregate, lightweight coarse aggregate, cement, water reducer, water, dispersant, viscose fiber, and polyester fiber. This improves the uniformity of lightweight concrete, reduces stratification, and enhances structural strength. The apparent density is 1119-1230 kg / m 3 , compressive strength 41.5-44.6 MPa, but no mention of related thermal conductivity. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a concrete and a preparation method thereof in order to overcome the defects in the prior art. The concrete of the present invention has a low dry density but high compressive strength, can be used as a building structural material, and has a very low thermal conductivity.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a concrete comprising the following parts by mass: 450-550 parts of ceramsite, 350-450 parts of cement and 20-150 parts of fly ash; the particle size of the ceramsite is 0-5 mm.

[0009] In the present invention, the particle size of the ceramsite is equivalent to the diameter of a spherical particle based on the projected area of the particle.

[0010] In the present invention, the mass proportion of the ceramsite may be 500-540 parts, preferably 500-520 parts, such as 500 parts, 510 parts, 520 parts, 530 parts or 540 parts.

[0011] In the present invention, the ceramsite may be shale ceramsite.

[0012] In the present invention, the ceramsite can be crushed ceramsite. Crushed ceramsite is made by directly crushing ceramsite and then roasting it. The crushed ceramsite has a sharp shape.

[0013] In the present invention, the bulk density of the ceramsite can be 300-1000 kg / m 3 , for example 500-625 kg / m 3 .

[0014] In the present invention, the thermal insulation coefficient of the ceramsite can be less than or equal to 0.03 W / (m 2 In the construction field, the thermal insulation coefficient usually refers to the heat transfer coefficient of the wall or building materials. That is, under stable heat transfer conditions, when the air temperature difference on both sides of the enclosure is 1°C, the heat transferred through an area of 1 square meter per unit time.

[0015] In the present invention, the weight water absorption rate of the ceramsite may be less than or equal to 9%. The weight water absorption rate refers to the proportion of the weight increase of the material after absorbing water, and is calculated as follows: weight water absorption rate = (wet weight - dry weight) / dry weight × 100%, where the wet weight refers to the weight of the material after saturation with water, and the dry weight refers to the weight of the material in a dry state.

[0016] In the present invention, the particle size of the ceramsite can be 1-5 mm, preferably 2-5 mm.

[0017] In the present invention, the particle size of the ceramsite can be 0-3 mm, preferably 0-1 mm.

[0018] In the present invention, the ceramsite may include large ceramsite with a particle size of 2-5 mm; preferably, the mass fraction of the large ceramsite is less than or equal to 290 parts, for example, 250 parts, 270 parts, 280 parts or 290 parts.

[0019] In the present invention, the ceramsite may include small ceramsite with a particle size of 0-3 mm; preferably, the mass fraction of the small ceramsite is 220-270 parts, for example, 250 parts.

[0020] In the present invention, the mass proportion of the cement may be 380-450 parts, preferably 400-420 parts.

[0021] In the present invention, the cement is conventionally selected in the art, such as Portland cement; preferably, 425 ordinary Portland cement. Portland cement is a hydraulic binder primarily made by grinding Portland cement clinker, an appropriate amount of limestone or granulated blast furnace slag, and gypsum. Its chemical composition primarily includes tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite, with tricalcium silicate comprising the majority.

[0022] In the present invention, the mass fraction of the fly ash can be 50-80 parts. Fly ash is a fine solid particulate matter produced in the coal combustion process, and mainly comes from the coal-fired boilers of thermal power plants. Its formation process is that after the coal powder is burned at high temperature, the incompletely burned mineral residues are carried out by the flue gas and collected by dust removal equipment. It is one of the main solid wastes of coal-fired power plants. From the chemical composition point of view, the main components of fly ash include silicon dioxide, aluminum oxide, iron oxide and calcium oxide. Under normal circumstances, the content of silicon dioxide and aluminum oxide in fly ash is relatively high, accounting for more than 70% of the total components. In terms of physical properties, fly ash particles are small, usually spherical or irregularly porous, with a particle size range from a few microns to hundreds of microns, and a large specific surface area (usually 1000-3650 cm 2 / g), with a density of approximately 1.8-2.4 g / cm 3 .

[0023] In the present invention, the fly ash is conventionally selected in the art, such as Class II fly ash, obtained according to GBT 1596-2017 "Fly ash used in cement and concrete".

[0024] In the present invention, the concrete may also include cellulose or a derivative thereof. The cellulose or derivative thereof may be present in an amount of 0.1-0.5 parts by weight, preferably 0.17-0.19 parts by weight, for example 0.18 parts by weight. Cellulose derivatives are commonly selected in the art, such as cellulose ethers or modified cellulose ethers.

[0025] In the present invention, the concrete may also conventionally include a water reducer. A water reducer is a chemical admixture used to improve the properties of concrete. Water reducers can be classified into various types, including lignin sulfonates, naphthalene-based, aminosulfonates, aliphatic, and water-soluble resins. The weight percentage of the water reducer can be 1-5 parts, preferably 1.8-2.2 parts, for example 2 parts. The water reducer is conventionally selected in the art, such as a polycarboxylate water reducer.

[0026] In the present invention, the concrete may also include a defoamer, which is a conventional option in the art. A defoamer is a chemical additive used to address foaming issues during concrete construction. Its primary function is to eliminate or suppress bubbles generated during concrete mixing. Examples of concrete defoamers include polyether-modified silicone oils, organosilicones, and mineral oils. The defoamer can be present in an amount of 0.5-1.5 parts by weight, more preferably 0.8-1.2 parts, for example, 1 part.

[0027] In the present invention, the concrete may not include sand. The apparent density of the sand may be ≥2500 kg / m 3 Apparent density refers to the mass per unit volume of a material in its natural state. It is usually used to describe the physical properties of porous or granular materials, reflecting the density of the material and the influence of internal pores. Its calculation formula is: ρ0=m / V0, ρ0 represents the apparent density, m represents the mass of the material, and V0 represents the volume of the material in its natural state, including the solid volume and the volume of open and closed pores. The bulk density of the sand can be ≥1400 kg / m 3 Bulk density refers to the mass per unit volume of a granular or powdered material in its natural state of accumulation. It typically includes the pores within the particles and the voids between them. It is calculated using the formula: ρ0' = m / V0', where ρ0' is the bulk density, m is the mass of the material, and V0' is the bulk volume of the material, which includes the volume of the particles, the volume of the pores within the particles, and the volume of the voids between the particles. The sand has a particle size of 30-50 mesh. The sand can be natural sand or manufactured sand. Natural sand is rock particles formed by natural conditions (such as weathering, water transport, and sedimentation) with a particle size of less than 5 mm. Natural sand can be divided into river sand, lake sand, sea sand, and mountain sand. Its particles are regular in shape and smooth in surface, but its gradation is usually discontinuous and may contain impurities such as silt and shells. Manufactured sand is rock particles produced through mechanical crushing and screening processes with a particle size of less than 4.75 mm. Manufactured sand includes granite, limestone, and construction waste. Manufactured sand has a more regular particle shape, a rough surface, distinct edges, and a stable particle size distribution. The color and composition of manufactured sand are different from those of natural sand.

[0028] In certain specific embodiments of the present invention, the concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 290 parts of large ceramsite with a particle size of 2-5 mm, 450 parts of cement and 50 parts of fly ash, excluding sand.

[0029] In certain specific embodiments of the present invention, the concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 270 parts of large ceramsite with a particle size of 2-5 mm, 450 parts of cement and 50 parts of fly ash, excluding sand.

[0030] In certain specific embodiments of the present invention, the concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 270 parts of large ceramsite with a particle size of 2-5 mm, 420 parts of cement and 80 parts of fly ash, excluding sand.

[0031] In certain specific embodiments of the present invention, the concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 270 parts of large ceramsite with a particle size of 2-5 mm, 400 parts of cement and 80 parts of fly ash, excluding sand.

[0032] In certain specific embodiments of the present invention, the concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 280 parts of large ceramsite with a particle size of 2-5 mm, 400 parts of cement and 80 parts of fly ash, excluding sand.

[0033] In certain specific embodiments of the present invention, the concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 250 parts of large ceramsite with a particle size of 2-5 mm, 420 parts of cement and 80 parts of fly ash, excluding sand.

[0034] In certain specific embodiments of the present invention, the concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 270 parts of large ceramsite with a particle size of 2-5 mm, 380 parts of cement and 80 parts of fly ash, excluding sand.

[0035] In a second aspect, the present invention provides a method for preparing concrete, comprising the following steps: drying a mixture; the mixture comprises the following parts by mass: 450-550 parts of ceramsite, 350-450 parts of cement, 20-150 parts of fly ash and 150-200 parts of water; the particle size of the ceramsite is 0-5 mm.

[0036] In the present invention, the ceramsite can be as described above.

[0037] In the present invention, the cement may be as described above.

[0038] In the present invention, the fly ash may be as described above.

[0039] In the present invention, the concrete may further include cellulose or its derivatives;

[0040] In the present invention, the concrete may further include a water reducing agent;

[0041] In the present invention, the concrete may further include a defoaming agent;

[0042] In the present invention, the concrete may not include sand;

[0043] In the present invention, the mass fraction of the water may be 165-180 parts.

[0044] In the present invention, conventionally, the method for preparing the concrete comprises the following steps:

[0045] S1. Mixing a cementitious mixture with the ceramsite to obtain a dry powder mixture; the cementitious mixture includes the cement and the fly ash;

[0046] S2. Mixing the dry powder mixture with the water and drying.

[0047] In certain specific embodiments of the present invention, the method for preparing concrete comprises the following steps:

[0048] Step 1: uniformly mix cellulose, water reducing agent, defoaming agent, cement, and fly ash to prepare a cementitious mixture;

[0049] Step 2: After washing and drying, the ceramsite is placed in a horizontal forced mixer, and 50% of the gelling mixture is added while stirring for about 1 minute, and then another 50% of the gelling mixture is added and stirred for 1 minute to obtain a dry powder mixture;

[0050] Step 3: In a horizontal forced mixer, add 100% water first, then add all the dry powder mixture, stir for 2 minutes, let it stand for 2 minutes, stir for another minute, and dry.

[0051] In a third aspect, the present invention provides concrete produced by the above-mentioned method for producing concrete.

[0052] In the present invention, the concrete is the concrete as described in the first aspect.

[0053] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

[0054] The reagents and raw materials used in the present invention are commercially available.

[0055] The positive progress effect of the present invention is:

[0056] (1) The concrete of the present invention uses ceramsite as the main lightweight aggregate, and the dry density is less than 1610 kg / m 3 , even less than 1550 kg / m 3 , but the compressive strength also meets the requirements of more than 39.5 MPa, and even more than 45 MPa, which can be used as a building structure material; the thermal conductivity coefficient does not exceed 0.35 W / (m·K), or even lower than 0.35 W / (m·K);

[0057] (2) The concrete of the present invention does not contain sand, which can avoid the high cost of transporting river sand and use ceramsite that is easy to transport instead. At the same time, the shape and particle size of the ceramsite are matched to meet the requirements of better performance of the concrete.

[0058] (3) The concrete of the present invention can meet the requirements of building structural strength through the scientific proportion of each component, and has obvious energy-saving improvements compared with existing structural materials. It is simple to produce, convenient to construct, and low in cost. DETAILED DESCRIPTION

[0059] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0060] In the following examples and comparative examples, the raw materials used are as follows:

[0061] Ceramic aggregate (particle size 0-3 mm), made of crushed shale ceramsite, with a bulk density of 625 kg / m 3 , cylinder pressure strength is above 1.3MPa, thermal insulation coefficient is 0.030 W / (m 2 ·K) or less, and the weight water absorption rate is less than 9%.

[0062] Ceramic aggregate (particle size 2-5 mm), made of crushed shale ceramsite, with a bulk density of 500 kg / m 3 , cylinder pressure strength is above 1.3MPa, thermal insulation coefficient is 0.030 W / (m 2 ·K) or less, and the weight water absorption rate is less than 9%.

[0063] Cement, 425 ordinary Portland cement.

[0064] Fly ash, Class II fly ash in GBT 1596-2017 "Fly ash for cement and concrete".

[0065] Yellow sand, 30-50 mesh, according to the classification of GBT 14684-2022 "Construction Sand", with a 0.30-0.60 mm square sieve size, natural sand, machine-made sand or mixed sand in Zone 1.

[0066] Modified cellulose ether was purchased from Hercules Temple, model 30011C.

[0067] Polycarboxylate water reducer, model R1020, was purchased from Shanghai Runpeng Trading Co., Ltd.

[0068] Defoaming agent, purchased from Shanghai Runpeng Trading Co., Ltd., model DF-3018.

[0069] Example 1

[0070] In this embodiment, the formula is: 520 parts of ceramsite (including 250 parts of small ceramsite with a particle size of 0-3 mm and 270 parts of large ceramsite with a particle size of 2-5 mm), 400 parts of cement, 80 parts of fly ash, 0.18 parts of modified cellulose ether, 2 parts of polycarboxylate water reducer, 1 part of defoamer, and 180 parts of water. The specific preparation steps include:

[0071] Step 1: uniformly mix modified cellulose ether, polycarboxylate water reducer, defoamer, cement and fly ash to prepare a cementitious mixture.

[0072] Step 2: Wash and dry the ceramsite, then put it into a horizontal forced mixer, add 50% of the gelling mixture while stirring, stir for about 1 minute, then add another 50% of the gelling mixture, stir evenly for 1 minute to obtain a dry powder mixture.

[0073] Step 3: In a horizontal forced mixer, first add all the water, then add all the dry powder mixture, stir for 2 minutes, let it stand for 2 minutes, and then stir for 1 minute to obtain the concrete mixture, which can be directly used in construction. The concrete obtained after drying has the characteristics of lightness and high strength.

[0074] Example 2

[0075] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 500 parts of ceramsite (including 250 parts of small ceramsite with a particle size of 0-3 mm and 250 parts of large ceramsite with a particle size of 2-5 mm), 420 parts of cement, and 80 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0076] Example 3

[0077] The only difference from Example 1 is that the mass parts of ceramsite, cement, fly ash and water in the formula are changed to: 540 parts of ceramsite (including 250 parts of small ceramsite with a particle size of 0-3 mm and 290 parts of large ceramsite with a particle size of 2-5 mm), 450 parts of cement, 30 parts of fly ash, and 165 parts of water, and the mass parts of the remaining components remain unchanged.

[0078] Example 4

[0079] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 520 parts of ceramsite (including 250 parts of small ceramsite with a particle size of 0-3 mm and 270 parts of large ceramsite with a particle size of 2-5 mm), 450 parts of cement, and 50 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0080] Example 5

[0081] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 520 parts of ceramsite (including 250 parts of small ceramsite with a particle size of 0-3 mm and 270 parts of large ceramsite with a particle size of 2-5 mm), 420 parts of cement, and 80 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0082] Example 6

[0083] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 530 parts of ceramsite (including 250 parts of small ceramsite with a particle size of 0-3 mm and 280 parts of large ceramsite with a particle size of 2-5 mm), 420 parts of cement, and 80 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0084] Example 7

[0085] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 520 parts of ceramsite (including 250 parts of small ceramsite with a particle size of 0-3 mm and 270 parts of large ceramsite with a particle size of 2-5 mm), 380 parts of cement, and 80 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0086] Comparative Example 1

[0087] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 500 parts of ceramsite (including 270 parts of small ceramsite with a particle size of 0-3 mm and 230 parts of large ceramsite with a particle size of 2-5 mm), 480 parts of cement, and 30 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0088] Comparative Example 2

[0089] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 500 parts of ceramsite (including 270 parts of small ceramsite with a particle size of 0-3 mm and 230 parts of large ceramsite with a particle size of 2-5 mm), 470 parts of cement, and 30 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0090] Comparative Example 3

[0091] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 500 parts of ceramsite (including 250 parts of small ceramsite with a particle size of 0-3 mm and 250 parts of large ceramsite with a particle size of 2-5 mm), 480 parts of cement, and 30 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0092] Comparative Example 4

[0093] The only difference from Example 1 is that the mass parts of ceramsite, cement and fly ash in the formula are changed to: 500 parts of ceramsite (including 230 parts of small ceramsite with a particle size of 0-3 mm and 270 parts of large ceramsite with a particle size of 2-5 mm), 480 parts of cement, and 30 parts of fly ash, and the mass parts of the remaining components remain unchanged.

[0094] Comparative Example 5

[0095] The only difference from Example 1 is that the mass parts of ceramsite, cement, fly ash and water in the formula are changed to: 500 parts of ceramsite (including 210 parts of small ceramsite with a particle size of 0-3 mm and 290 parts of large ceramsite with a particle size of 2-5 mm), 480 parts of cement, 30 parts of fly ash, and 165 parts of water, and the mass parts of the remaining components remain unchanged.

[0096] Comparative Example 6

[0097] The only difference from Example 1 is that 40 parts of yellow sand is added to the formula, and the mass parts of ceramsite, cement and fly ash are changed to: 490 parts of ceramsite (including 220 parts of small ceramsite with a particle size of 0-3 mm and 270 parts of large ceramsite with a particle size of 2-5 mm), 380 parts of cement, and 80 parts of fly ash. The mass parts of the other components remain unchanged. The specific preparation steps include:

[0098] Step 1: uniformly mix modified cellulose ether, polycarboxylate water reducer, defoamer, cement and fly ash to prepare a cementitious mixture.

[0099] Step 2: Wash the yellow sand and ceramsite with water, dry them, and put them into a horizontal forced mixer. Add 50% of the gelling mixture while stirring, stir for about 1 minute, then add another 50% of the gelling mixture, stir evenly for 1 minute to obtain a dry powder mixture.

[0100] Step 3: In a horizontal forced mixer, first add all the water, then add all the dry powder mixture, stir for 2 minutes, let it stand for 2 minutes, and then stir for 1 minute to obtain the concrete mixture, and then dry the concrete.

[0101] The formulas of various embodiments and comparative examples are listed in the following table.

[0102]

[0103]

[0104] Effect embodiment

[0105] 1. Test object: Concrete obtained in Examples 1-7 and Comparative Examples 1-6.

[0106] 2. Test method:

[0107] (1) Thermal conductivity: The experimental method of GBT5486-2008 "Test methods for inorganic rigid thermal insulation products" was adopted. Two thermal conductive samples (300 mm × 300 mm) were used in each experiment. The thermal conductivity coefficient was measured by the heat flow meter method and the average value was taken.

[0108] (2) Dry density: Measured according to the appendix of GB / T 20473 "Building Thermal Insulation Mortar". Dry at 105℃ to constant weight and then measure.

[0109] (3) Compressive strength: According to GB50107-2010 “Standard for Test and Assessment of Concrete Strength”, three 100 mm × 100 mm × 100 mm cubic specimens were made after mixing. After curing for 28 days, the compressive strength test was carried out and the average value was taken.

[0110] 3. Test results: See the table below.

[0111]

[0112] First, from the comparison between Comparative Example 1 and Comparative Example 2, it can be seen that only reducing the amount of cement will significantly reduce the compressive strength of the concrete, but the thermal conductivity will not change much.

[0113] Similarly, a comparison between Examples 5, 1, and 7 shows that simply reducing the cement content significantly reduces the compressive strength of the concrete and decreases the density somewhat, but the thermal conductivity fluctuates slightly and meets the requirements. Furthermore, a comparison between Examples 4, 5, and 1 shows that reducing the cement content while simultaneously increasing the fly ash content slightly reduces the compressive strength of the concrete, but significantly reduces the thermal conductivity.

[0114] Secondly, from the comparison between Example 1 and Example 6, it can be seen that by only increasing the amount of large ceramsite, the compressive strength of the concrete is reduced, and although the thermal conductivity is increased, it still meets the requirements.

[0115] Furthermore, from the comparison between Example 2 and Examples 1 and 6, it can be seen that reducing the amount of cement and simultaneously increasing the amount of large ceramsite significantly reduces the compressive strength of the concrete and also reduces the thermal conductivity. However, from the comparison between Example 6 and Example 7, it can be seen that reducing the amount of cement and simultaneously reducing the amount of large ceramsite results in almost no change in the compressive strength and thermal conductivity of the concrete.

[0116] Thirdly, from the comparison between Example 7 and Comparative Example 6, it can be seen that the addition of yellow sand and the simultaneous reduction of the amount of small ceramsite can lead to an increase in the compressive strength of the concrete, but the thermal conductivity is increased too much.

[0117] Fourthly, from the comparison between comparative examples 4, 3 and 1, it can be seen that when the total amount of ceramsite remains unchanged, the compressive strength and thermal conductivity of the concrete are increased by increasing the proportion of small ceramsite in the ceramsite.

Claims

1. A concrete, characterized in that: The invention comprises the following parts by mass: 450-550 parts of ceramsite, 350-450 parts of cement and 20-150 parts of fly ash; and the particle size of the ceramsite is 0-5 mm.

2. The concrete according to claim 1, characterized in that It meets one or more of the following conditions: (1) The mass proportion of the ceramsite is 500-540 parts, preferably 500-520 parts, such as 500 parts, 510 parts, 520 parts, 530 parts or 540 parts; (2) The ceramsite is shale ceramsite; (3) The ceramsite is crushed ceramsite; (4) The bulk density of the ceramsite is 300-1000 kg / m 3 , for example 500-625 kg / m 3 ; (5) The thermal insulation coefficient of the ceramsite is less than or equal to 0.03 W / (m 2 K); (6) The weight water absorption rate of the ceramsite is less than or equal to 9%; (7) The particle size of the ceramsite is 1-5 mm, preferably 2-5 mm; (8) The particle size of the ceramsite is 0-3 mm, preferably 0-1 mm.

3. The concrete according to claim 1, characterized in that It meets one or both of the following conditions: (1) The ceramsite includes large ceramsite with a particle size of 2-5 mm; preferably, the mass fraction of the large ceramsite is less than or equal to 290 parts, for example, 250 parts, 270 parts, 280 parts or 290 parts; (2) The ceramsite includes small ceramsite with a particle size of 0-3 mm; preferably, the mass fraction of the small ceramsite is 220-270 parts, for example, 250 parts.

4. The concrete according to claim 1, characterized in that It meets one or more of the following conditions: (1) The mass fraction of the cement is 380-450 parts, preferably 400-420 parts; (2) The cement is Portland cement; preferably 425 ordinary Portland cement; (3) The mass fraction of the fly ash is 50-80 parts; (4) The fly ash is Class II fly ash; (5) The concrete further comprises cellulose or its derivatives; (6) The concrete also includes a water reducing agent; (7) The concrete also includes a defoaming agent; (8) The concrete does not include sand.

5. The concrete according to claim 4, characterized in that It meets one or more of the following conditions: (1) The weight percentage of the cellulose or its derivative is 0.1-0.5 parts, preferably 0.17-0.19 parts, for example 0.18 parts; (2) The cellulose derivative is cellulose ether or modified cellulose ether; (3) The mass fraction of the water reducer is 1-5 parts, preferably 1.8-2.2 parts, for example 2 parts; (4) The water reducer is a polycarboxylate water reducer; (5) The mass fraction of the defoaming agent is 0.5-1.5 parts, more preferably 0.8-1.2 parts, for example 1 part; (6) The apparent density of the sand is ≥2500 kg / m 3 ; (7) The bulk density of the sand is ≥1400 kg / m 3 ; (8) The particle size of the sand is 30-50 mesh; (9) The sand is natural sand and / or machine-made sand.

6. The concrete according to claim 1, characterized in that It meets one of the following conditions: (1) The concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 290 parts of large ceramsite with a particle size of 2-5 mm, 450 parts of cement and 50 parts of fly ash, excluding sand; (2) The concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 270 parts of large ceramsite with a particle size of 2-5 mm, 450 parts of cement and 50 parts of fly ash, excluding sand; (3) The concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 270 parts of large ceramsite with a particle size of 2-5 mm, 420 parts of cement and 80 parts of fly ash, excluding sand; (4) The concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 270 parts of large ceramsite with a particle size of 2-5 mm, 400 parts of cement and 80 parts of fly ash, excluding sand; (5) The concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 280 parts of large ceramsite with a particle size of 2-5 mm, 400 parts of cement and 80 parts of fly ash, excluding sand; (6) The concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 250 parts of large ceramsite with a particle size of 2-5 mm, 420 parts of cement and 80 parts of fly ash, excluding sand; (7) The concrete comprises the following parts by mass: 250 parts of small ceramsite with a particle size of 0-3 mm, 270 parts of large ceramsite with a particle size of 2-5 mm, 380 parts of cement and 80 parts of fly ash, excluding sand.

7. A method for preparing concrete, characterized in that: It includes the following steps: The mixture is dried; the mixture comprises the following parts by mass: 450-550 parts of ceramsite, 350-450 parts of cement, 20-150 parts of fly ash and 150-200 parts of water; the particle size of the ceramsite is 0-5 mm.

8. The method for preparing concrete according to claim 7, characterized in that: It meets at least one of the following conditions: (1) The ceramsite is as defined in claim 2 or 3; (2) The cement is as defined in claim 4; (3) The fly ash is as defined in claim 4; (4) The concrete further comprises cellulose or its derivatives; (5) The concrete also includes a water reducing agent; (6) The concrete also includes a defoaming agent; (7) The concrete does not include sand; (8) The mass fraction of the water is 165-180 parts.

9. The method for preparing concrete according to claim 7, wherein: It includes the following steps: S1. Mixing a cementitious mixture with the ceramsite to obtain a dry powder mixture; the cementitious mixture includes the cement and the fly ash; S2. Mixing the dry powder mixture with the water and drying.

10. Concrete prepared by the method for preparing concrete according to any one of claims 7 to 9; preferably, the concrete is the concrete according to any one of claims 1 to 6.

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