High performance low shrinkage concrete containing lightweight aggregate and method of making same

Abstract

The application discloses a kind of high-performance low-shrinkage concrete containing lightweight aggregate and a preparation method thereof, and belongs to the technical field of concrete.The lightweight high-performance concrete, on the one hand, by adding lightweight components such as ceramic granules and ceramic sand, substantially reduces the apparent density of the concrete, achieving the purpose of lightweight high-performance concrete;Meanwhile, using reasonable proportioning, the lightweight aggregate is uniformly distributed in the concrete, so that the stress distribution is uniform, the strength, bending resistance and impact resistance of the concrete are significantly improved.Adding a defoaming agent to the base concrete can effectively inhibit the generation of pores and macroscopic cracks in the concrete, and can improve the crack resistance, tensile resistance, bending resistance and impact resistance of the concrete.A series of lightweight concrete with strength grade LC60-LC80 and density 1700-2150 kg / m3 can be prepared.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of concrete, in particular to high-performance low-shrinkage concrete containing lightweight aggregate and a preparation method and application thereof. BACKGROUND

[0002] With the development and construction of the country, the demand for large-scale buildings and large-span bridges is becoming more and more intense, and the requirements for lightweight, high-strength, green and durable civil engineering materials are also becoming higher and higher. As one of the most common materials in bridge engineering, traditional concrete has a large density, which directly leads to a large structural self-weight, thereby limiting the development of the span of concrete bridges. The lightweight of concrete can effectively reduce the proportion of the self-weight of the bridge and improve the effective load ratio of the bridge. For the external curtain wall structure of a large-scale building, it is an inevitable trend to pursue a concrete structure that is resistant to high temperature and lightweight and high-strength.

[0003] The high-performance low-shrinkage concrete containing lightweight aggregate is a kind of concrete with high performance and a strength of more than 60 MPa, which is designed according to the maximum bulk density theory. The HSLC (high-strength lightweight concrete) has high strength and lightweight performance, and can reduce the structural self-weight in the building field, thereby reducing the material consumption and carbon emission. The HSLC has unique advantages in the fields of bridge engineering, underground structure and high-rise building. It is of great significance to develop a kind of HSLC that can meet the structural performance requirements, reduce the structural self-weight and improve the structural safety, for further development of the application scenarios of the HSLC.

[0004] However, it is found in the use process that the traditional lightweight concrete has a serious floating of the lightweight aggregate while ensuring the fluidity, and the homogeneity of the lightweight concrete itself is difficult to guarantee, which seriously affects the engineering quality. The main reason is that the lightweight aggregate used in the lightweight concrete has a small container weight and is easy to float in the concrete. How to effectively control the floating of the lightweight aggregate in the lightweight concrete is an important prerequisite for guaranteeing the engineering performance of the lightweight concrete. In addition, due to the dense internal structure of the HSLC, defects are few, which leads to the fact that the HSLC is prone to burst under high-temperature conditions, causing great harm to the structure and the surrounding environment and reducing the safety under high-temperature conditions.

[0005] Starting from the use and selection of raw materials, high-quality lightweight aggregate with high strength and composite polycarboxylic admixture for adjusting the working performance are selected; and the mixing proportion of the lightweight high-strength concrete is designed and optimized according to the theoretical "strength matching principle" and "interface enhancement theory"; the prepared lightweight high-strength concrete has good workability, homogeneity, durability and crack resistance, and is applied to the supporting engineering. SUMMARY

[0006] The application provides a lightweight high-temperature-resistant high-performance low-shrinkage concrete, which is prepared by adding lightweight ceramsite, shale ceramic sand and a defoaming agent, and has the advantages of low concrete container weight (which can be reduced to 1700 kg / m3), high strength (which can reach 60 MPa), high temperature resistance (which can reach 800 DEG C), and the like.3 )At the same time, no big change in performance is caused; and the problems of easy floating of ceramsite and ceramic sand and explosion of concrete are solved.

[0007] The application provides a kind of high-performance low-shrinkage concrete of lightweight aggregate, the concrete is mixed by the following raw materials with weight percentage:

[0008] Cement 19%-21%, first-class fly ash 4%-6%, silica fume 12%-15%, water 5%-8%, gravel 28%-32%, ceramsite 5%-10%, river sand 15%-20%, 900-grade shale ceramsite 5%-10%, water reducing agent 5%, defoaming agent 0.01%.

[0009] Preferably, the cement is ordinary portland cement of 42.5.

[0010] Preferably, the fly ash is first-class fly ash.

[0011] Preferably, the specific surface area of the silica fume is greater than or equal to 19000 m 2 / kg, and the SiO2 content is greater than or equal to 90%.

[0012] Preferably, the gravel is basalt gravel with a particle size of 5-10 mm and a continuous gradation.

[0013] Preferably, the ceramsite is fly ash ceramsite with a bulk density of 1600 kg / m 3 -1800 kg / m 3 , composed of 5-12 mm size, with a cylinder compressive strength of 13.1 MPa, a 1h water absorption of 4.8%, a softening coefficient of 0.9, and a sum of breakage rate and abrasion rate of 3.1%.

[0014] Preferably, the river sand is medium sand with a fineness modulus of 2.3-2.6.

[0015] Preferably, the shale ceramsite is 900-grade, with a bulk density of 900 kg / m 3 -1400 kg / m 3 , composed of 0.5-0.35 mm, 0.35-0.25 mm, and 0.160-0.25 mm large, medium, and small sizes, with a weight ratio of 60-65:20-25:10-20, a cylinder compressive strength greater than 5 MPa, and chemical components mainly including silicon dioxide, aluminum oxide, iron oxide, and calcium oxide.

[0016] Preferably, the water reducing agent is a polycarboxylic acid water reducing agent.

[0017] Preferably, the defoaming agent mainly contains modified organosilicon.

[0018] The application further provides a preparation method of the high-performance low-shrinkage concrete of the light-weight aggregate, which comprises the following steps:

[0019] S1, pre-wetting treatment is performed on the ceramsite to obtain pre-wetted ceramsite;

[0020] S2, water and an additive are uniformly stirred to obtain a first mixture;

[0021] S3, the cement, the first-class fly ash, the silica fume and the fine aggregate are added into a forced stirrer for internal dry mixing for 1-2 minutes, so that the cementitious material and the fine aggregate are uniformly mixed to obtain a second mixture;

[0022] S4, the first mixture and the second mixture are uniformly mixed, the coarse aggregate is added into the interior of the stirring equipment for stirring for 1-2 minutes, so that the coarse aggregate can be better wrapped by the mortar, and the concrete can be formed;

[0023] S5, the concrete is formed in a mold, and moisture conservation is performed.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] The light-weight high-performance concrete disclosed by the application, on one hand, by adding light-weight components such as ceramsite and ceramic sand, the apparent density of the concrete is greatly reduced, and the purpose of light-weight high-performance concrete is achieved; and on the other hand, by using reasonable proportioning, the light-weight aggregate is uniformly distributed in the concrete, so that the stress distribution is uniform, and the strength, the bending resistance and the impact resistance of the concrete are obviously improved; by adding the defoaming agent into the matrix concrete, the generation of pores and macroscopic cracks of the concrete can be effectively inhibited, and the crack resistance, the tensile resistance, the bending resistance and the impact resistance of the concrete can be improved; a series of light-weight concrete with the strength grade LC60-LC80 and the density 1700-2150 kg / m3 can be prepared.

[0026] The light-weight high-performance concrete provided by the application is based on the closest packing density theory in the HSLC preparation technology, and the ceramic sand is used to replace the river sand in the traditional concrete, so that the problem of large apparent density of the traditional concrete is solved. The ceramic sand is in a honeycomb shape and has low thermal conductivity. The apparent density of the concrete with the river sand as the aggregate is 2400 kg / m-2600 kg / m, and the apparent density of the UHPC with the ceramic sand as the aggregate can be reduced to 1600 kg / m-2000 kg / m, so that the apparent density of the concrete is greatly reduced.

[0027] The main components of the defoaming agent in the application include polyether and modified organic silicon, can destroy the foam film, make the foam disappear rapidly, so that the surface of the concrete is more compact, the bubbles generated in the concrete can be effectively inhibited, the micro-cracks caused by factors such as plastic shrinkage, dry shrinkage and temperature change can be inhibited, and the crack resistance and the impact resistance of the concrete are greatly improved.

[0028] The lightweight high-performance concrete provided by the application is beneficial to be applied to prefabricated structure transportation and hoisting and splicing, and is beneficial to promote the development of prefabricated high-performance concrete and accelerate engineering progress. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated herein by reference. The illustrations are shown schematically and are not intended to limit the application unless otherwise defined in the patent claims.

[0030] Figure 1 It is a cross-sectional view of the high-performance low-shrinkage concrete after forming. DETAILED DESCRIPTION

[0031] The technical solutions of the patent will be further described in detail below in combination with specific embodiments.

[0032] In the description of the application, it should be noted that the terms "inner", "outer", "upper", "lower", "horizontal", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0033] In Example 1, the high-performance low-shrinkage concrete of lightweight aggregate is mixed from the following raw materials in parts by weight: cement 41 parts, first-grade fly ash 11 parts, silica fume 2.75 parts, water 14.3 parts, gravel 60 parts, ceramsite 17.5 parts, river sand 36.2 parts, 900-grade shale ceramic sand 14 parts, water reducing agent 2.75 parts, and defoaming agent 0.5 parts.

[0034] In this embodiment, the shale ceramic sand is 900-grade, with a bulk density of 1230 kg / m 3 , and is composed of large, medium and small sizes of 0.5-0.35 mm, 0.35-0.25 mm and 0.160-0.25 mm, and the weight ratio of the large, medium and small sizes of the ceramic sand is 60:25:20.

[0035] In this embodiment, the fly ash is first-grade fly ash.

[0036] In this embodiment, the specific surface area of the silica fume is ≥19000 m 2 / kg, and the SiO2 content is ≥90%.

[0037] In this embodiment, the gravel is basalt gravel, with a particle size of 5-10 mm and a continuous gradation.

[0038] In the embodiment, the ceramsite is fly ash ceramsite, and the bulk density is 1600kg / m 3 ~1800kg / m 3 The size is 5-12mm, the cylinder compressive strength is 13.1MPA, the 1h water absorption is 4.8%, the softening coefficient is 0.9, and the sum of the crushing rate and the abrasion rate is 3.1%.

[0039] In the embodiment, the river sand is medium sand with fineness modulus of 2.3-2.6.

[0040] In the embodiment, the water reducing agent is specifically polycarboxylic acid high-performance water reducing agent.

[0041] In the embodiment, the defoaming agent is organic silicon liquid defoaming agent.

[0042] The preparation method of the high-performance low-shrinkage concrete of the lightweight aggregate in the embodiment is as follows:

[0043] Firstly, the ceramsite is pre-wetted in water for 72h to obtain pre-wetted ceramsite.

[0044] Then, the water and the additive are stirred uniformly to obtain a first mixture;

[0045] Subsequently, the Portland cement, the first fly ash, the silica fume and the fine aggregate are added into a forced stirrer for internal dry mixing for 1-2min, so that the cementitious material and the fine aggregate are uniformly mixed to obtain a second mixture;

[0046] Finally, the first mixture and the second mixture are uniformly mixed, the speed of the stirrer is adjusted to 200r / min, and the uniform low-speed stirring is continued for 1-2min, so that the concrete is formed;

[0047] In the embodiment 2, the difference from the above embodiment 1 is that:

[0048] The high-performance low-shrinkage concrete of the lightweight aggregate in the embodiment is mixed by the following raw materials in parts by weight: cement 41 parts, first fly ash 11 parts, silica fume 2.75 parts, water 14.3 parts, gravel 50 parts, ceramsite 32.5 parts, river sand 36.2 parts, 900-grade shale ceramsite 14 parts, water reducing agent 2.75 parts, and defoaming agent 0.5 parts.

[0049] The shale ceramsite is 900-grade, and the bulk density is 1230kg / m 3 The large, medium and small size shale ceramsite is composed of 0.5-0.35mm, 0.35-0.25mm and 0.160-0.25mm, and the weight ratio of the large, medium and small size shale ceramsite is 60:25:20.

[0050] The preparation method of the high-performance low-shrinkage concrete of the lightweight aggregate in the embodiment is as follows:

[0051] Put the ceramic sand into water and pre-wet for 72h.

[0052] Then, stir the water and the admixture to obtain a first mixture;

[0053] Put the ceramic sand into water and pre-wet for 72h.

[0054] Then, stir the water and the admixture to obtain a first mixture;

[0055] Put the ceramic sand into water and pre-wet for 72h.

[0056] Then, stir the water and the admixture to obtain a first mixture;

[0057] Example 3 is different from the above-mentioned example 1 in that:

[0058] The high-performance low-shrinkage concrete of the light aggregate in this example is prepared by mixing the following raw materials in the weight ratio: cement 41 parts, first-grade fly ash 11 parts, silica fume 2.75 parts, water 14.3 parts, gravel 40 parts, ceramic sand 39.1 parts, river sand 36.2 parts, 900-grade shale ceramic sand 14 parts, water reducing agent 2.75 parts, and defoaming agent 0.5 parts.

[0059] The shale ceramic sand is of 900 grade and has a bulk density of 1230 kg / m 3 It is composed of large, medium and small sizes of 0.5-0.35 mm, 0.35-0.25 mm and 0.160-0.25 mm, and the weight ratio of the large, medium and small sizes of the ceramic sand is 60:25:20.

[0060] The preparation method of the high-performance low-shrinkage concrete of the light aggregate in this example is as follows:

[0061] Put the ceramic sand into water and pre-wet for 72h.

[0062] Then, stir the water and the admixture to obtain a first mixture;

[0063] Put the ceramic sand into water and pre-wet for 72h.

[0064] Then, stir the water and the admixture to obtain a first mixture;

[0065] Example 4 is different from the above-mentioned example 1 in that:

[0066] The high-performance low-shrinkage concrete of the lightweight aggregate in the embodiment is prepared by mixing the following raw materials in parts by weight: cement 41 parts, first-class fly ash 11 parts, silica fume 2.75 parts, water 14.3 parts, gravel 60 parts, ceramsite 17.5 parts, 900-grade shale ceramic sand 28 parts, water reducing agent 2.75 parts, and defoaming agent 0.5 parts.

[0067] The shale ceramic sand is of 900 grade, and has a bulk density of 1230 kg / m 3 The large, medium and small size ceramic sand is composed of 0.5-0.35 mm, 0.35-0.25 mm and 0.160-0.25 mm, and the weight ratio of the large, medium and small size ceramic sand is 60:25:20.

[0068] The preparation method of the high-performance low-shrinkage concrete of the lightweight aggregate in the embodiment is as follows:

[0069] The ceramsite is pre-wetted in water for 72 hours.

[0070] Then, the water and the additive are stirred uniformly to obtain a first mixture;

[0071] The Portland cement, the first-class fly ash, the silica fume and the fine aggregate are added into a forced stirrer for internal dry mixing for 1-2 minutes, so that the cementing material and the fine aggregate are uniformly mixed to obtain a second mixture;

[0072] The first mixture and the second mixture are uniformly mixed, the stirring speed of the stirrer is adjusted to 200 r / min, and the uniform low-speed stirring is continuously performed for 1-2 minutes, so that the concrete is formed;

[0073] Example 5 is different from the above-described example 1 in that:

[0074] The high-performance low-shrinkage concrete of the lightweight aggregate in the embodiment is prepared by mixing the following raw materials in parts by weight: cement 41 parts, first-class fly ash 11 parts, silica fume 2.75 parts, water 14.3 parts, gravel 60 parts, ceramsite 17.5 parts, 900-grade shale ceramic sand 28 parts, water reducing agent 2.75 parts, and defoaming agent 0.5 parts.

[0075] The shale ceramic sand is of 900 grade, and has a bulk density of 1230 kg / m 3 The large, medium and small size ceramic sand is composed of 0.5-0.35 mm, 0.35-0.25 mm and 0.160-0.25 mm, and the weight ratio of the large, medium and small size ceramic sand is 60:25:20.

[0076] The preparation method of the high-performance low-shrinkage concrete of the lightweight aggregate in the embodiment is as follows:

[0077] The ceramsite is pre-wetted in water for 72 hours.

[0078] Then, the water and the admixture are stirred to obtain a first mixture;

[0079] The silicate cement, the first fly ash, the silica fume and the fine aggregate are added into a forced stirrer and internally stirred for 1-2 min to mix the cementitious material and the fine aggregate to obtain a second mixture;

[0080] The first mixture and the second mixture are uniformly mixed, the speed of the stirrer is adjusted to 200 r / min, and the uniform low-speed stirring is continued for 1-2 min, so that the concrete is formed.

[0081] I. Performance effect

[0082] The super high performance concrete prepared in the above examples 1-5 is tested for slump, spread, mechanical properties and dry shrinkage value, and the test standards and methods are as follows:

[0083] (1) Test standard of slump: GB / T50080-2016;

[0084] (2) Test standard of compressive strength and flexural strength: refer to GB / T50081-2019 "Standard for test methods of physical and mechanical properties of concrete" to make standard test blocks of 10 cm×10 cm×10 cm, and detect the flexural strength and compressive strength of the test blocks after curing for 7 d and 28 d.

[0085] (3) Anti-cracking performance test: refer to GB / T50081-2019 "Standard for test methods of physical and mechanical properties of concrete" to make standard test blocks, and record the number of surface cracks of the concrete after curing for 28 d under the condition of an environment of 42±2℃ to obtain the number of cracks per unit area.

[0086] (4) Shrinkage performance test: refer to GB / T50081-2019 "Standard for test methods of physical and mechanical properties of concrete" to make standard test blocks, and then refer to GB / T50082-2009 "Standard for test methods of long-term performance and durability of ordinary concrete" to record the shrinkage data of the test blocks after curing for 28 d under the condition of an environment of 42±2℃.

[0087] The results are as follows:

[0088]

[0089] From the above results, the ultra-high performance concrete prepared according to the application has high mechanical properties, 7d flexural strength of 5-7 MPa, 28d flexural strength of 7-9 MPa, 7d compressive strength of 44-55 MPa, 28d compressive strength of 64-71 MPa, no crack number, and shrinkage of 0.10-0.25‰; it can be seen that the concrete of the application has low shrinkage effect and high strength, good durability and bearing capacity, and the effect of Example 3 is the best.

[0090] The comparative example is set up for the best strength Example 5 for comparison, as follows:

[0091] Comparative Example 1, the difference between this comparative example and Example 5 is that the lightweight aggregate high-performance low-shrinkage concrete includes the following raw materials by weight: cement 44 parts, first-grade fly ash 11 parts, silica fume 0 parts, water 14.3 parts, gravel 50 parts, ceramsite 32.5 parts, 900-grade shale ceramic sand 28 parts, water reducing agent 2.75 parts, and defoaming agent 0.5 parts.

[0092] Comparative Example 2, the difference between this comparative example and Example 3 is that the ceramic sand is not pre-wetted.

[0093] Comparative Example 3, the difference between this comparative example and Example 3 is that the low-shrinkage and anti-cracking ultra-performance concrete does not add a defoaming agent to the raw materials.

[0094] Specifically, it includes the following raw materials by weight: cement 41 parts, first-grade fly ash 11 parts, silica fume 2.75 parts, water 14.3 parts, gravel 50 parts, ceramsite 32.5 parts, 900-grade shale ceramic sand 28 parts, and water reducing agent 2.75 parts.

[0095]

[0096] From the above results, it can be seen that, compared with Comparative Example 1, the concrete raw materials of the application are reasonably selected and scientifically proportioned, and the performance is synergistically exerted, with low shrinkage, high mechanical properties, and not easy to break; compared with Comparative Example 1, the addition of an appropriate amount of silica fume in the concrete can fill the small pores and fine cracks inside the concrete, improve the compactness and durability of the concrete. In addition, the active silicon dioxide in the silica fume reacts with water to form calcium silicate cementitious material, which can enhance the strength and hardness of the concrete; compared with Comparative Example 2, the ceramsite is pre-wetted, and the wet ceramsite can supplement the water for cement hydration, making the cement slurry hydration more complete and the self-shrinkage reduced.

[0097] Example 5 compared with Comparative Example 3, adding defoaming agent, wet ceramsite will be the hydration of cement to supplement water, make the hydration of cement paste more thoroughly, self-shrinkage reduction concrete defoaming agent can destroy the surface tension of concrete, prevent the bubble in the concrete; Defoaming agent in the surfactant can form a lubricating film in the concrete, so that the concrete particles between each other sliding, thereby improving the compactness of concrete.

[0098] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high-performance, low-shrinkage concrete using lightweight aggregate, characterized in that, The concrete is made from the following raw materials by weight percentage: The composition of the raw materials is as follows: cement 19%-21%, fly ash 4%-6%, silica fume 12%-15%, water 5%-8%, crushed stone 28%-32%, ceramsite 5%-10%, river sand 15%-20%, 900-grade shale ceramsite sand 5%-10%, water-reducing agent 5%, and defoamer 0.01%, with the sum of all percentages being 100%. The ceramsite is fly ash ceramsite with a bulk density of 1600 kg / m³. 3 ~1800kg / m 3 It is composed of materials with dimensions of 5-12mm, a compressive strength of 13.1MPa, a water absorption rate of 4.8% in 1 hour, a softening coefficient of 0.9, and a combined breakage and wear rate of 3.1%. The shale ceramsite sand is grade 900, with a bulk density of 900 kg / m³. 3 ~1400kg / m 3 It consists of large, medium and small sizes of shale clay sand with diameters of 0.5-0.35mm, 0.35-0.25mm and 0.16-0.25mm, and the weight ratio of large, medium and small shale clay sand is 60-65:20-25:10-20. The cylinder compressive strength is greater than 5MPa, and the main chemical components are silicon dioxide, aluminum oxide, iron oxide and calcium oxide.

2. The high-performance, low-shrinkage concrete with lightweight aggregate according to claim 1, characterized in that, The cement is grade 42.5 ordinary Portland cement.

3. The high-performance, low-shrinkage concrete with lightweight aggregate according to claim 1, characterized in that, The fly ash is grade I fly ash.

4. The high-performance, low-shrinkage concrete with lightweight aggregate according to claim 1, characterized in that, The specific surface area of ​​the silica fume is ≥19000 m². 2 / kg, of which SiO2 content ≥90%.

5. The high-performance, low-shrinkage concrete with lightweight aggregate according to claim 1, characterized in that, The crushed stone is basalt crushed stone with a particle size of 5-10 mm and a continuous gradation.

6. The high-performance, low-shrinkage concrete with lightweight aggregate according to claim 1, characterized in that, The river sand is medium sand with a fineness modulus of 2.3-2.

6.

7. The high-performance, low-shrinkage concrete with lightweight aggregate according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

8. The high-performance, low-shrinkage concrete with lightweight aggregate according to claim 1, characterized in that, The main component of the defoamer is modified organosilicon.

9. The method for preparing high-performance, low-shrinkage concrete using lightweight aggregates according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Pre-wet the ceramsite to obtain pre-wetted ceramsite; S2. Mix water and additives evenly to obtain the first mixture; S3. Add the cement, grade I fly ash, silica fume, and fine aggregate into a forced mixer and dry mix for 1-2 minutes to ensure that the cementitious materials and fine aggregate are evenly mixed to obtain a second mixture. S4. Mix the first mixture and the second mixture evenly, add coarse aggregate into the mixing equipment and mix for 1-2 minutes so that the coarse aggregate can be well coated by the mortar, and the concrete can be formed. S5. The concrete is formed in a mold and then moisturized and cured.

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