Lightweight high-strength aggregate and lightweight aggregate concrete prepared using the same

Abstract

The application discloses a kind of light high-strength aggregate, each raw material and the weight fraction it occupies include: cement 20~30 parts, mineral admixture 65~75 parts, thickening agent 1~2 parts, fiber 1~2 parts, water 100~120 parts.The application uses cement and mineral admixture and thickening agent as main raw material, and combines thickening agent paste technology and larger forming water solid ratio, can give consideration to good light, high-strength performance, it can guarantee good working performance, mechanical property and stability when being applied to prepare light aggregate concrete;And the preparation method involved is relatively simple, easy to operate, suitable for promotion and application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building materials, and particularly relates to a light-weight high-strength aggregate and light-weight aggregate concrete prepared by using the same. BACKGROUND

[0002] Light-weight aggregate concrete refers to concrete using light-weight aggregate, and the apparent density thereof is not greater than 1950 kg / m 3 It is a light-weight building material widely used at present, and can realize 20% to 40% weight reduction under the same strength grade compared with ordinary concrete, and can be used in load-bearing parts or key parts in buildings. The light-weight aggregate concrete has the characteristics of light weight, high strength, heat preservation and fire resistance, but due to the low elastic modulus of the light-weight aggregate, the shrinkage of the cement paste in the water evaporation process cannot be effectively inhibited, and the shrinkage value is much higher than that of ordinary concrete, and the shrinkage cracking problem is prone to occur.

[0003] The light-weight aggregate concrete has many advantages, but the light-weight aggregate used at present usually has rough and porous surface, and a large amount of cement paste is adsorbed during the mixing process, which significantly reduces the fluidity of the concrete; in addition, the light-weight aggregate and the cement paste are prone to segregation and stratification due to the large density difference during the pouring and vibrating process, and the construction and quality control problems caused by the poor workability of the light-weight aggregate concrete are more prominent. SUMMARY

[0004] The main purpose of the present application is to solve the problems and deficiencies in the prior art, and provide a pouring type light-weight high-strength aggregate, which has simple preparation method, high strength, and can freely adjust the morphology and grading; when the light-weight high-strength aggregate is applied to prepare light-weight aggregate concrete, the obtained concrete has high fluidity and is not prone to segregation and stratification, and has good strength and volume stability, and is suitable for popularization and application.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A light-weight high-strength aggregate, the weight fractions of each raw material and the weight fractions thereof include: cement 20 to 30 parts, mineral admixture 65 to 75 parts, thickening agent 1 to 2 parts, fiber 1 to 2 parts, and water 100 to 120 parts.

[0007] In the above scheme, the cement is ordinary Portland cement with a strength grade of P·O42.5 or above.

[0008] In the above scheme, the mineral admixture can be selected from one or more of fly ash, mineral powder, metakaolin, etc., and the specific surface area is not less than 350 m 2 / kg, and the activity index is not less than 70%.

[0009] In the above scheme, the thickening agent is preferably a polysaccharide thickening agent such as starch or cellulose, and has a thickening capacity of 2-20 Pa·s at 1% solid content (at room temperature) and a thixotropic index of 1.5-4.5.

[0010] In the above scheme, the fiber is preferably glass fiber having a length of 6-12 mm, an aspect ratio of 100-200, and a tensile strength of not less than 200 MPa.

[0011] In the above scheme, the water temperature is 10-40℃.

[0012] In the above scheme, the cast lightweight high-strength aggregate has an angularity coefficient of 0.1-0.2, a water content of 90-100%, a cylinder compressive strength of 5-8 MPa, and an absolute dry bulk density of 300-400 kg / m 3 .

[0013] The above method for preparing a cast lightweight high-strength aggregate includes the following preparation steps:

[0014] (1) mixing and stirring cement, mineral admixture, thickening agent, fiber, and water in a proportioning manner;

[0015] (2) heating and keeping the slurry obtained in step (1) under stirring;

[0016] (3) casting the slurry kept at temperature into a mold, and performing primary curing until hardening, demolding, and obtaining aggregate particles;

[0017] (4) performing secondary curing on the obtained aggregate particles to obtain a lightweight high-strength aggregate product.

[0018] In the above scheme, the stirring rate used in step (1) is 60-90 r / min, and the stirring time is 10-20 min.

[0019] In the above scheme, the stirring rate used in step (2) is 30-60 r / min.

[0020] In the above scheme, in step (2), the heating step is to raise the temperature (the heating method is not limited, and can be high-temperature steam heating or electric heating, etc.) to 90-100℃ at a rate of 5-15℃ / min; and the keeping time is 5-10 min.

[0021] In the above scheme, the water-to-solid ratio of the slurry kept at temperature in step (2) is 1.1-1.4.

[0022] In the above scheme, the temperature used in the primary curing is 80-100℃, the relative humidity is 90-100%, and the curing time is 1-2 h.

[0023] In the scheme, the secondary curing is performed at a temperature of 25-100 DEG C, a relative humidity of 90-100%, and a time of 1-28 days.

[0024] Preferably, the secondary curing is performed at a temperature of 90-100 DEG C, a relative humidity of 95-100%, and a time of 1-2 days.

[0025] The application further provides a light aggregate concrete prepared by using the cast light high-strength aggregate, wherein the raw materials and the weight percentage of each raw material are as follows: cement 16-20 parts, light high-strength aggregate 30-35 parts, sand 40-45 parts, water 6-10 parts, and high-efficiency water reducing agent 0.1-0.2 parts; and the preparation method comprises the following steps: uniformly stirring (5-10 min) the weighed raw materials and then pouring and forming, and naturally curing for 14-28 days to obtain the light aggregate concrete product.

[0026] In the scheme, the cement is preferably P·O42.5 and above grade ordinary portland cement.

[0027] In the scheme, the cast light high-strength aggregate adopts a continuous grading of 5-15 mm.

[0028] In the scheme, the sand adopts river sand or machine-made sand, the fineness modulus is 2.4-2.8, the crushing value is lower than 30%, and the apparent density is 2500-2800 kg / m 3 .

[0029] In the scheme, the water reducing rate of the high-efficiency water reducing agent is 30-40%, and the high-efficiency water reducing agent is preferably a polycarboxylic acid water reducing agent.

[0030] In the scheme, the stirring rate is 90-120 r / min.

[0031] In the scheme, the natural curing temperature is 20-35 DEG C, and the relative humidity is 80-100%.

[0032] The performance optimization mechanism of the light high-strength aggregate and the light aggregate concrete prepared by using the light high-strength aggregate comprises:

[0033] 1) The light high-strength aggregate is formed by using a larger water-solid ratio, and contains a large number of capillary pores in a water-retaining state, thereby reducing the density difference between the aggregate and the cement mortar, and effectively solving the stratification problem caused by the floating of the light aggregate in the stirring and pouring process.

[0034] 2) In the process of high-temperature gelatinization under heating and heat preservation, the polysaccharide thickening agent can connect and intertwine with each other to form a network containing water colloid, which can fill the capillary pores in the obtained lightweight high-strength aggregate, effectively improve the problem that the traditional aggregate absorbs water in the concrete and reduces the fluidity, and slowly release water to the surrounding to ensure that the cement hydration reaction is fully carried out. In addition, it can promote the realization of the smooth surface of the lightweight high-strength aggregate, no cracks and the like, effectively improve the problem that the traditional lightweight aggregate easily adsorbs the cement slurry in the concrete, effectively ensure the high fluidity of the obtained concrete, and reduce the forming defects caused by insufficient fluidity.

[0035] 3) During the hardening process of the concrete, part of the water will undergo hydration reaction or evaporate to the environment, causing significant volume shrinkage. The water in the capillary pores of the obtained lightweight high-strength aggregate can slowly diffuse outward and continuously supplement the water in the hardened cement slurry, which can effectively reduce the shrinkage value of the concrete.

[0036] 4) The surface of the traditional coarse aggregate usually has a large amount of calcium hydroxide, which is the hydration product of cement, forming a relatively weak interfacial transition zone. The obtained lightweight high-strength aggregate contains unreacted mineral admixtures, which can react with calcium hydroxide to generate C-S-H gel and ettringite, effectively improving the interfacial transition zone and thus improving the strength.

[0037] 5) The further introduction of fibers in the application can effectively improve the brittleness of the lightweight high-strength aggregate, reduce stress concentration at the pores of the lightweight aggregate, delay crack propagation, and thus improve the strength of the lightweight aggregate concrete.

[0038] Compared with the prior art, the application has the following beneficial effects:

[0039] 1) Under the adjustment of the thickening agent, effective forming under the condition of super-high water-solid ratio is promoted, and the phenomenon of bleeding and layering does not occur. A large number of capillary pores formed by water adjust the bulk density of the aggregate. The capillary pores formed are uniformly distributed in the aggregate, and the pore size is small, which can effectively reduce the stress concentration phenomenon under the action of load, and obtain lightweight high-strength aggregate. In addition, the particle type and particle size distribution can be controlled by the mold during pouring and forming, which helps to improve the workability and strength of the concrete.

[0040] 2) A large amount of water colloid exists in the capillary pores of the lightweight high-strength aggregate, which can be directly used to produce lightweight aggregate concrete without the traditional aggregate pre-wetting process, and can ensure good working performance.

[0041] 3) The obtained pouring type lightweight high-strength aggregate is cured at room temperature or by steam, without the need for high-temperature sintering process. The carbon emission and energy consumption involved in the preparation process are much lower than those of traditional sintered lightweight aggregate such as ceramsite. The production process is simple, and the performance of the obtained lightweight high-strength aggregate can be effectively ensured. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0043] In the following examples and comparative examples, the cement is P·O42.5 Portland cement. The mineral admixture is selected from fly ash or metakaolin, and the specific surface area is 430 m 2 / kg and 485 m 2 / kg, respectively, and the activity index is 98% and 112%, respectively. The thickening agent is hydroxypropyl starch produced by Jinan Yuncheng Biological Technology Co., Ltd., and the thickening capacity at 1% solid content and normal temperature is 16 Pa·s, and the thixotropic index is 2.1. The fiber is glass fiber, and the length is 6-7 mm, the aspect ratio is 120-140, and the tensile strength is 550-600 MPa. The river sand has a fineness modulus of 2.6, a crushing value of 12%, and an apparent density of 2670 kg / m 3 . The water reducing agent is polycarboxylic acid superplasticizer, and the water reducing rate is 35%. The ceramsite has a continuous gradation of 5-15 mm, an apparent density of 1510 kg / m 3 , a bulk density of 790 kg / m 3 , a 1h water absorption rate of 7%, and a cylinder compressive strength of 5.1 MPa.

[0044] Example 1

[0045] A pouring type light-weight high-strength aggregate and a light aggregate concrete prepared therefrom, and a preparation method thereof, the preparation method comprising the following steps:

[0046] light-weight high-strength aggregate;

[0047] 1) taking cement 25 parts, fly ash 72 parts, hydroxypropyl starch thickening agent 2 parts, fiber 1 part, and water 110 parts, stirring uniformly to obtain a slurry, the stirring time being 15 min and the stirring rate being 60 r / min;

[0048] 2) heating the slurry by high-temperature steam, the heating rate being 10℃ / min, and keeping the temperature at 95℃ for 10 min; the stirring rate is controlled at 45 r / min during the heating process of the slurry; and the water-solid ratio of the obtained slurry after keeping the temperature is 1.2;

[0049] 3) pouring the heated slurry into a mold, and entering a curing chamber for curing for 2 h to harden and demold to obtain aggregate particles, the temperature in the curing chamber being 90℃ and the relative humidity being 95%;

[0050] 4) obtaining the finished light-weight high-strength aggregate after the post-curing of the aggregate particles, the curing temperature being 90℃, the relative humidity being 90%, and the time being 1d, to obtain the pouring type light-weight high-strength aggregate, and the corner coefficient thereof being 0.16.

[0051] Lightweight aggregate concrete

[0052] Take cement 18 parts, lightweight high-strength aggregate (using 5-15 mm continuous gradation) 32 parts, sand 42 parts, water 8 parts, high efficiency water reducing agent 0.15 parts, the weighed raw materials are stirred at a speed of 90-120 r / min for 5 min, then poured into a mold, and naturally cured (temperature 30℃, relative humidity 85%) for 28 days to obtain lightweight aggregate concrete products.

[0053] Example 2

[0054] A kind of lightweight high-strength aggregate and the lightweight aggregate concrete prepared by using it, its preparation method is substantially same with example 1, the difference is that, in the preparation step of lightweight high-strength aggregate, the weight fraction of each raw material is as follows: cement 25 parts, metakaolin 72 parts, hydroxypropyl starch thickening agent 2 parts, fiber 1 part, water 110 parts.

[0055] Example 3

[0056] A kind of lightweight high-strength aggregate and the lightweight aggregate concrete prepared by using it, its preparation method is substantially same with example 1, the difference is that: in the preparation step of lightweight high-strength aggregate, the aggregate particles are cured twice to obtain finished lightweight high-strength aggregate, wherein the curing temperature is 35℃, the relative humidity is 95%, and the time is 28d.

[0057] Comparative example 1

[0058] A kind of lightweight high-strength aggregate and the lightweight aggregate concrete prepared by using it, its preparation method is substantially same with example 1, the difference is that: no thickening agent is used.

[0059] Comparative example 2

[0060] A kind of lightweight high-strength aggregate and the lightweight aggregate concrete prepared by using it, its preparation method is substantially same with example 1, the difference is that: the slurry is heated by electric heating, the heating rate is 10℃ / min, and the temperature is kept at 95℃ for 10 min during heating, and the stirring rate is controlled at 45 r / min during heating; the water-solid ratio of the slurry obtained after keeping warm is 0.9.

[0061] Comparative example 3

[0062] A kind of lightweight high-strength aggregate and the lightweight aggregate concrete prepared by using it, its preparation method is substantially same with example 1, the difference is that: take cement 25 parts, fly ash 72 parts, hydroxypropyl starch thickening agent 2 parts, fiber 1 part, and water 80 parts, and stir uniformly to obtain a slurry.

[0063] Comparative example 4

[0064] A kind of pouring type light high-strength aggregate and the light aggregate concrete prepared by it, the specific preparation steps are as follows:

[0065] 1) the aggregate described in comparative example 1 is used;

[0066] 2) light aggregate concrete;Its preparation method is basically same with example 1, the difference is that taking cement 18 parts, aggregate (using 5-15 mm continuous gradation) 32 parts, sand 42 parts, water 8 parts, hydroxypropyl starch thickening agent 0.05 parts, high efficiency water reducing agent 0.15 parts.

[0067] Comparative example 5

[0068] A kind of pouring type light high-strength aggregate and the light aggregate concrete prepared by it, its preparation method is basically same with example 1, the difference is that using ceramsite to replace finished light high-strength aggregate.

[0069] The light aggregate and light aggregate concrete obtained from example 1-3 and comparative example 1-5 are respectively tested for performance, and the results are shown in Table 1.

[0070] Table 1: Performance test results of light aggregate and light aggregate concrete

[0071]

[0072] The above examples are only for clearly illustrating the examples made, and are not limited to the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description, which need not and cannot be exhausted all the embodiments, therefore the obvious changes or variations still within the scope of the present application.

Claims

1. A lightweight high strength aggregate, characterized by, The raw materials and the weight percentage of each raw material include: cement 20-30 parts, mineral admixture 65-75 parts, thickening agent 1-2 parts, fiber 1-2 parts, and water 100-120 parts; The thickening agent is a polysaccharide thickening agent, and the thickening capacity of 1% solid content is 2-20 Pa·s, and the thixotropic index is 1.5-4.

5. The preparation method of the light-weight high-strength aggregate comprises the following steps: (1) uniformly mixing cement, mineral admixture, thickening agent, fiber and water according to the proportion, and stirring; (2) heating and keeping the slurry obtained in step (1) under stirring; (3) pouring the slurry after keeping warm into a mold, and curing once to harden, demolding, and obtaining aggregate particles; (4) curing the obtained aggregate particles again to obtain light-weight high-strength aggregate products.

2. The lightweight high-strength aggregate according to claim 1, characterized in that, The cement is ordinary Portland cement with a strength grade of P·O42.5 or above.

3. The lightweight high-strength aggregate according to claim 1, wherein The mineral admixture is one or more of fly ash, slag, metakaolin; the specific surface area is not less than 350 m 2 / kg, and the activity index is not less than 70%.

4. The lightweight high-strength aggregate according to claim 1, wherein The length of the fiber is 6-12 mm, the aspect ratio is 100-200, and the tensile strength is not less than 200 MPa.

5. The method of producing a lightweight high-strength aggregate according to any one of claims 1 to 4, characterized by, The preparation method comprises the following steps: (1) uniformly mixing cement, mineral admixture, thickening agent, fiber and water according to the proportion, and stirring; (2) heating and keeping the slurry obtained in step (1) under stirring; (3) pouring the slurry after keeping warm into a mold, and curing once to harden, demolding, and obtaining aggregate particles; (4) curing the obtained aggregate particles again to obtain light-weight high-strength aggregate products.

6. The preparation method according to claim 5, characterized in that, In step (2), the heating step is: heating at a rate of 5-15 ℃ / min to 90-100 ℃; and the keeping warm time is 5-10 min.

7. The production method according to claim 5, characterized by, The curing temperature is 80-100 ℃, the relative humidity is 90-100%, the curing time is 1-2 h, the curing temperature is 25-100 ℃, the relative humidity is 90-100%, and the curing time is 1-28 d.

8. A lightweight aggregate concrete prepared using the lightweight high strength aggregate of claim 1, characterized by, The raw materials and the weight percentage of each raw material include: cement 16-20 parts, light-weight high-strength aggregate 30-35 parts, sand 40-45 parts, water 6-10 parts, and high-efficiency water reducing agent 0.1-0.2 parts.

9. Lightweight concrete according to claim 8, characterized in that The light-weight high-strength aggregate adopts a continuous gradation of 5-15 mm.

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