Lightweight low-carbon concrete and preparation method thereof

Abstract

The invention discloses lightweight low-carbon concrete, which is prepared from the following raw materials in parts by weight: 220 to 280 parts of sulphoaluminate cement, 40 to 90 parts of waste paper pulp ash, 80 to 120 parts of phosphogypsum, 40 to 65 parts of floating beads, 20 to 35 parts of silica fume, 600 to 750 parts of ceramsite, 8 to 12 parts of additives and 190 to 230 parts of water, the waste paper pulp ash is obtained by performing low-temperature anaerobic activation, grinding and gradient screening on original waste paper ash. The phosphogypsum and the sulphoaluminate cement are synergistically complementary in a system, and the waste paper pulp ash and the grading design of various powder are combined, so that the problem of strength reduction and brittleness enhancement of a solid waste admixture in conventional lightweight concrete can be effectively solved, and the lightweight low-carbon concrete with light weight, compactness and high-strength performance is formed while the solid waste is consumed in a limited manner; popularization and application are facilitated.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a lightweight, low-carbon concrete based on the synergistic effect of multiple solid wastes and its preparation method. Background Technology

[0002] In recent years, lightweight concrete has been increasingly used in high-rise buildings and long-span structures due to its light weight and excellent seismic performance. However, traditional lightweight concrete still mainly relies on ordinary Portland cement, which has problems such as low early strength, high brittleness, and high carbon emissions. Therefore, developing a new type of concrete technology that integrates lightweight, high strength, and high value utilization of solid waste has significant economic, environmental, and application value. Summary of the Invention

[0003] The main objective of this invention is to provide a lightweight, low-carbon concrete that, through the synergistic effect of multiple solid wastes, effectively disposes of solid waste while saving resources, reducing carbon emissions, and simultaneously improving the performance (strength, toughness, etc.) of lightweight concrete. It is easy to operate, has low cost, and is suitable for widespread application.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A lightweight, low-carbon concrete comprises the following raw materials and their respective weight proportions: 220-280 parts of sulfoaluminate cement, 40-90 parts of waste paper pulp ash, 80-120 parts of phosphogypsum, 40-65 parts of cenospheres, 20-35 parts of silica fume, 600-750 parts of ceramsite, 8-12 parts of admixtures, and 190-230 parts of water; wherein the waste paper pulp ash is obtained by low-temperature anaerobic activation, grinding, and gradient sieving of waste paper ash.

[0005] In the above scheme, the content of anhydrous calcium sulfoaluminate in the sulfoaluminate cement is greater than 50wt%, the content of anhydrite is greater than 25wt%, and the 3-day compressive strength is ≥25MPa.

[0006] In the above scheme, the specific surface area of ​​the waste paper pulp ash is 300~400m². 2 / kg, density is 1500~2500kg / m³ 3 .

[0007] This invention first involves low-temperature anaerobic activation, grinding, and gradient sieving of waste paper pulp ash to promote its effective application in concrete.

[0008] Furthermore, the low-temperature anaerobic activation temperature is 320~380℃, and the time is 2.5~3h.

[0009] Furthermore, the waste paper pulp ash contains two particle sizes: 0.15~0.3mm and 0.3~0.6mm, with a mass ratio of 3:7~4:6.

[0010] Furthermore, the method for preparing the waste paper pulp ash includes the following steps: (1) The original waste paper pulp ash residue is subjected to low-temperature anaerobic activation treatment, specifically by placing the waste paper pulp ash residue in a protective atmosphere (nitrogen, etc.) at 320~380℃ for 2.5~3h; (2) Grind the activated product at a ball milling rate of 200-300 r / min for 1-1.5 h; (3) Perform gradient screening (through 0.3mm and 0.6mm grading screens) to obtain two grades of particles of 0.15~0.3mm and 0.3~0.6mm, and mix them in proportion to obtain the waste paper pulp ash residue.

[0011] In the above scheme, the phosphogypsum particle size is between 5 and 50 μm, and the specific surface area is between 350 and 500 m². 2 The apparent density is between 2600 and 2800 kg / m³. 3 between.

[0012] Furthermore, the phosphogypsum needs to be pretreated by calcining at 800~900℃ for 1~2 hours before use.

[0013] In the above scheme, the cenospheres are fly ash cenospheres with a density of 600~800 kg / m³. 3 The particle size is between 50 and 150 μm.

[0014] In the above scheme, the average particle size of the silica fume is 100~300nm, and the specific surface area is 22000~26000m². 2 Between / kg, SiO2 content >85%.

[0015] In the above scheme, the ceramsite has a particle size of 5~10mm and an apparent density of 1750~1850kg / m³. 3 The compressive strength of the cylinder is between 10 and 15 MPa.

[0016] In the above scheme, the admixture is a high-performance polycarboxylate superplasticizer with a water reduction rate of ≥25% and a solid content of ≥20%.

[0017] The above-mentioned method for preparing lightweight, low-carbon concrete includes the following steps: 1) Weighing of raw materials: each raw material and its weight percentage include: 220-280 parts of sulfoaluminate cement, 60-90 parts of waste paper pulp ash, 90-120 parts of phosphogypsum, 40-65 parts of cenospheres, 20-35 parts of silica fume, 600-750 parts of ceramsite, 8-12 parts of admixtures, and 190-230 parts of water. 2) Raw material pretreatment: The weighed phosphogypsum was calcined to obtain calcined phosphogypsum. Soak the weighed ceramsite in clean water (20-24 hours), then drain it at room temperature (1-2 hours) to obtain water-absorbing ceramsite. 3) First, add the obtained water-absorbing ceramsite to the mixer and stir (20~30s). Then, add the full amount of sulfoaluminate cement, waste paper pulp ash, phosphogypsum, and silica fume in sequence and dry mix evenly (60~90s). Then, add 40~60% of the amount of water and stir (60~90s). Next, add the remaining water and the mixture of admixtures and stir for 1.5~2 minutes. Finally, add the cenospheres and stir evenly (30~45s) to obtain the lightweight low-carbon concrete.

[0018] The lightweight, low-carbon concrete prepared according to the above scheme has an initial slump of 160-200 mm and a unit weight of 1400-1600 kg / m³. 3 Between these values, the 3d compressive strength is greater than 16 MPa, and the 28d compressive strength is greater than 25 MPa.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Phosphogypsum and sulfoaluminate cement complement each other in the system, which can improve the early strength of the system and improve the phenomenon of strength reduction in the later stage of sulfoaluminate cement stone.

[0020] 2) The lignocellulose in waste paper pulp ash can be evenly dispersed in the matrix. The porous structure on the fiber surface can adsorb cement hydration products, alleviate the volume expansion damage caused by phosphogypsum, and phosphogypsum can also offset the drying shrinkage caused by waste paper pulp ash to a certain extent, thus synergistically improving the flexural strength of concrete, optimizing crack resistance, improving concrete brittleness, and solving the problem of "brittle and weak" traditional lightweight concrete.

[0021] 3) The organic impurities in the waste paper pulp ash after pretreatment can be transformed into nucleation sites for ettringite, promoting uniform growth of ettringite and avoiding cracking caused by local enrichment of ettringite in traditional formulations. At the same time, its gradient particle size forms a four-level dense packing with ceramsite, cenospheres, and phosphogypsum, further promoting the improvement of the problem of 'reduced strength and increased brittleness' of solid waste admixtures in conventional lightweight concrete, forming a concrete matrix with lightweight, dense, and high-strength properties. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the following examples, the sulfoaluminate cement used is grade 42.5 rapid hardening sulfoaluminate cement produced by Xuancheng Anda Special Cement Company, in which anhydrous calcium sulfoaluminate accounts for 57.6%, anhydrite accounts for 30.8%, and the 3-day compressive strength is 31.6 MPa.

[0024] The virgin waste paper pulp ash used came from Hubei Xinhua Printing Co., Ltd., with a moisture content of 31.6%, a total lignocellulose content of 47.2%, a pH value of 5.8, and a loss on ignition of 38.9%.

[0025] The method for preparing waste paper pulp ash includes the following steps: (1) The original waste paper pulp ash residue was subjected to low-temperature anaerobic activation treatment, specifically by placing the waste paper pulp ash residue in nitrogen at 330℃ for 3h. (2) The activated product was ground, with the ball milling rate set to 220 r / min and the time to be 1 h; (3) Gradient screening (through 0.3mm and 0.6mm grading screens) is performed to obtain two grades of particles of 0.15~0.3mm and 0.3~0.6mm, which are then mixed at a mass ratio of 4:6 to obtain the waste paper pulp ash residue.

[0026] The phosphogypsum used was obtained from Yuan'an County, Yichang City, with an average particle size of approximately 24.7 μm and a specific surface area of ​​368 m². 2 / kg, apparent density is 2729kg / m³ 3 The water of crystallization content is 22.6%.

[0027] The silica fume used is from Xuzhou Mingrui Materials Technology Co., Ltd., with an average particle size of 145nm and a specific surface area of ​​24800m². 2 The SiO2 content is between 91.2% and 91.2% per kilogram.

[0028] The cenospheres used were purchased from Shandong Longteng New Materials Co., Ltd., and their density is approximately 720 kg / m³. 3 Between these values, the average particle size is 80.6 μm.

[0029] The ceramsite used is coal gangue ceramsite from Anhui Dongchen New Materials Co., Ltd., with a particle size of 5~10mm and an apparent density of 1770kg / m³. 3 Between these values, the cylinder compressive strength is 12.2 MPa.

[0030] The water-reducing agent used is from China Construction Western Construction New Materials Technology Co., Ltd., with a water reduction rate of 26.4% and a solid content of 33.8%.

[0031] Example 1 A lightweight, low-carbon concrete is prepared by the following steps: (1) Weigh the raw materials. The raw materials and their weight percentages include: 240 parts of sulfoaluminate cement, 40 parts of waste paper pulp ash, 80 parts of phosphogypsum, 50 parts of cenospheres, 28 parts of silica fume, 680 parts of ceramsite, 8 parts of admixtures, and 205 parts of water. (2) Raw material pretreatment; 2-1) The weighed phosphogypsum was calcined in a muffle furnace at 800℃ for 2 hours to obtain calcined phosphogypsum; 2-2) Soak the weighed ceramsite in water for 24 hours, then drain it at room temperature for 1 hour to obtain water-absorbing ceramsite; (3) First, add the pre-wetted and drained ceramsite into the mixer and mix for 30 seconds. Then, add the full amount of sulfoaluminate cement, waste paper pulp ash, phosphogypsum and silica fume in sequence and dry mix for 60 seconds. Then, add 50% of the amount of water and mix for 90 seconds. Then, add the remaining amount of water and the mixture of admixtures and mix for 2 minutes. Finally, add the cenospheres and mix for 30 seconds to obtain lightweight low-carbon concrete.

[0032] Example 2 A lightweight, low-carbon concrete is prepared in a manner similar to that of Example 1, except that the raw materials and their weight percentages are as follows: 220 parts of sulfoaluminate cement, 80 parts of waste paper pulp ash, 110 parts of phosphogypsum, 60 parts of cenospheres, 25 parts of silica fume, 700 parts of ceramsite, 9 parts of admixtures, and 210 parts of water.

[0033] Example 3 A lightweight, low-carbon concrete is prepared in a manner similar to that of Example 1, except that the raw materials and their weight percentages are as follows: 280 parts of sulfoaluminate cement, 60 parts of waste paper pulp ash, 120 parts of phosphogypsum, 40 parts of cenospheres, 30 parts of silica fume, 660 parts of ceramsite, 12 parts of admixtures, and 220 parts of water.

[0034] Comparative Example 1 A lightweight, low-carbon concrete is prepared in a manner similar to that of Example 1, except that phosphogypsum is not added (resulting in a later-stage strength reduction and lower flexural strength compared to the example). Comparative Example 2 A lightweight, low-carbon concrete is prepared in a manner similar to that of Example 1, except that silica fume is not added (due to its low compressive and flexural strength). Comparative Example 3 A lightweight, low-carbon concrete is prepared in a manner similar to that of Example 1, except that no cenospheres (which have high density, slightly higher compressive strength, and lower flexural strength) are added. Comparative Example 4 A lightweight, low-carbon concrete is prepared in a manner similar to that of Example 1, except that: undisturbed waste paper pulp ash is directly added (without anaerobic activation, grinding, or screening).

[0035] Comparative Example 5 A lightweight, low-carbon concrete is prepared in a manner largely similar to that of Example 1, except that waste paper pulp ash is replaced by secondary fly ash and chopped polypropylene fibers, wherein the amount of chopped polypropylene fibers is 0.5 parts; the fly ash is sourced from a thermal power plant, with a moisture content of 12.3%, a loss on ignition of 8.7%, and a SiO2 content of 54.2%; the chopped polypropylene fibers have an average length of 6 mm, a diameter of approximately 20 μm, and a tensile strength ≥300 MPa, and are purchased from a building materials company.

[0036] The concrete obtained in Examples 1-3 and Comparative Examples 1-5 were subjected to workability, mechanical properties, and unit weight tests, specifically including: initial slump, 3-day and 28-day flexural and compressive strength, unit weight, and 28-day shrinkage performance of the fresh concrete. The performance test results are shown in Table 1 below.

[0037] Table 1. Performance test results of concrete obtained in the examples and comparative examples.

[0038] The above comparative examples and embodiment data illustrate the synergistic effect of the raw materials in the innovation of this invention, which effectively solves the problems of low early strength and high brittleness of lightweight concrete, and also achieves innovative breakthroughs in solid waste application.

[0039] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A lightweight, low-carbon concrete, characterized in that, The raw materials and their respective weight proportions include: 220-280 parts of sulfoaluminate cement, 40-90 parts of waste paper pulp ash, 80-120 parts of phosphogypsum, 40-65 parts of cenospheres, 20-35 parts of silica fume, 600-750 parts of ceramsite, 8-12 parts of admixtures, and 190-230 parts of water; the waste paper pulp ash is obtained by low-temperature anaerobic activation, grinding, and gradient sieving of undisturbed waste paper ash.

2. The lightweight, low-carbon concrete according to claim 1, characterized in that, The low-temperature anaerobic activation temperature is 320~380℃, and the time is 2.5~3h.

3. The lightweight, low-carbon concrete according to claim 1, characterized in that, The sulfoaluminate cement contains more than 50 wt% anhydrous calcium sulfoaluminate, more than 25 wt% anhydrite, and has a 3-day compressive strength ≥ 25 MPa.

4. The lightweight, low-carbon concrete according to claim 1, characterized in that, The waste paper pulp ash contains two particle sizes: 0.15~0.3mm and 0.3~0.6mm, with a mass ratio of 3:7~4:

6.

5. The lightweight, low-carbon concrete according to claim 1, characterized in that, The phosphogypsum has a particle size of 5-50 μm and a specific surface area of ​​350-500 m². 2 / kg, apparent density is 2600~2800kg / m³ 3 .

6. The lightweight, low-carbon concrete according to claim 1, characterized in that, The phosphogypsum needs to be pretreated by calcining at 800-900℃ for 1-2 hours before use.

7. The lightweight, low-carbon concrete according to claim 1, characterized in that, The cenospheres are fly ash cenospheres with a density of 600~800 kg / m³. 3 The particle size is 50~150um; the average particle size of silica fume is 100~300nm, and the specific surface area is 22000~26000m². 2 / kg, SiO2 content > 85%.

8. The lightweight, low-carbon concrete according to claim 1, characterized in that, The ceramsite has a particle size of 5-10 mm and an apparent density of 1750-1850 kg / m³. 3 The cylinder compressive strength is 10~15MPa.

9. The lightweight, low-carbon concrete according to claim 1, characterized in that, The admixture is a high-performance polycarboxylate superplasticizer with a water reduction rate of ≥25%.

10. The method for preparing lightweight low-carbon concrete according to any one of claims 1 to 9, characterized in that, Includes the following steps: 1) Weighing of raw materials: each raw material and its weight percentage include: 220-280 parts of sulfoaluminate cement, 60-90 parts of waste paper pulp ash, 90-120 parts of phosphogypsum, 40-65 parts of cenospheres, 20-35 parts of silica fume, 600-750 parts of ceramsite, 8-12 parts of admixtures, and 190-230 parts of water. 2) Raw material pretreatment: The weighed phosphogypsum was calcined to obtain calcined phosphogypsum. Soak the weighed ceramsite in clean water, then drain it at room temperature to obtain water-absorbing ceramsite. 3) First, add the obtained water-absorbing ceramsite to the mixer and stir. Then, add the full amount of sulfoaluminate cement, waste paper pulp ash, phosphogypsum, and silica fume in sequence and dry mix evenly. Then, add a portion of the water and stir. Next, add the remaining water and the mixture of admixtures and stir for 1.5 to 2 minutes. Finally, add the cenospheres and stir evenly to obtain the lightweight low-carbon concrete.

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