Composite material for solid-waste-based quick-setting anti-cracking truss laminated slab, laminated slab and preparation method of composite material for solid-waste-based quick-setting anti-cracking truss laminated slab

Abstract

The invention belongs to the technical field of truss laminated slabs, and discloses a composite material for a solid-waste-based quick-setting anti-cracking type truss laminated slab, the laminated slab and a preparation method of the composite material, the laminated slab and the preparation method of the solid-waste-based quick-setting anti-cracking type truss laminated slab, and the composite material comprises the following components in parts by mass: 14-30 parts of solid-waste-based sulphoaluminate cement, 10-25 parts of desulfurized building gypsum, 5-15 parts of fly ash, 30-45 parts of medium sand, 15-25 parts of pebbles, 0.08-0.23 part of a polycarboxylate superplasticizer, 0-0.05 part of a suspending agent and 0.03-0.10 part of a defoaming agent. 0.05 to 0.55 part of boric acid and 0.02 to 0.13 part of a gypsum retarder; the mass ratio of the solid waste-based sulphoaluminate cement to the desulfurized building gypsum is 1: (0.7-1). The development speed of the early strength of the bottom plate of the laminated slab is increased, and the production efficiency of the laminated slab is greatly improved; the volume stability of the laminated slab is improved, the cracking risk of the laminated slab is greatly reduced, and the economic loss is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of truss composite slabs, and specifically relates to a composite material for solid waste-based rapid-setting and crack-resistant truss composite slabs, a composite slab and a preparation method thereof. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] The truss composite slab is composed of a precast concrete bottom slab (with steel trusses) and a cast-in-place concrete layer, and the two are connected by steel trusses to form an integral stress-bearing system. Generally, ordinary Portland cement concrete or ultra-high performance concrete is used as the bottom slab material for the composite slab. The thickness of the ordinary Portland cement concrete bottom slab is generally 50 - 80 mm, while the thickness of the UHPC bottom slab can be reduced to about 20 mm. The connection methods between the concrete bottom slab and the steel trusses mainly include two forms: bolt connection and precast embedding.

[0004] The existing truss composite slabs have the following problems in the preparation process: The early strength development of the existing ordinary Portland cement concrete bottom slab is slow, and the demolding time is usually more than 24 hours, which limits the production efficiency and restricts the large-scale production of precast bottom slabs; The drying shrinkage rate of ordinary Portland concrete is relatively large. In the precast embedding connection method, through cracks are likely to occur at the interface between the steel bars and the concrete due to the concentration of shrinkage stress, affecting the structural durability; Although bolt connection can avoid shrinkage cracking, the connectors will increase the structural self-weight, and the reserved holes may weaken the local bearing capacity of the bottom slab; Although ultra-high performance concrete can reduce the thickness of the bottom slab and improve the performance, its high material cost limits its engineering application. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a composite material for solid waste-based rapid-setting and crack-resistant truss composite slabs, a composite slab and a preparation method thereof. It improves the early strength development rate of the bottom slab of the composite slab, greatly improves the production efficiency of the composite slab; It improves the volume stability of the composite slab, greatly reduces the risk of cracking of the composite slab, and reduces economic losses. A large amount of solid waste and solid waste-based cementitious materials are used in the raw materials, greatly reducing the production cost of the composite slab and enhancing the environmental and social benefits.

[0006] In order to achieve the above purpose, the present invention is realized through the following technical solutions: In the first aspect, the present invention provides a composite material for solid waste-based rapid-setting and crack-resistant truss composite slabs, which includes the following components by mass: 14 - 30 parts of solid waste-based sulfoaluminate cement, 10 - 25 parts of desulfurized building gypsum, 5 - 15 parts of fly ash, 30 - 45 parts of medium sand, 15 - 25 parts of gravel, 0.08 - 0.23 parts of polycarboxylate water reducer, 0 - 0.05 parts of suspending agent, 0.03 - 0.10 parts of defoaming agent, 0.05 - 0.55 parts of boric acid, and 0.02 - 0.13 parts of gypsum retarder; The mass ratio of the solid waste-based sulfoaluminate cement to the desulfurized building gypsum is 1:0.7 - 1.

[0007] The gravel serves as coarse aggregate to form a skeleton and bear external loads, while the medium sand serves as fine aggregate to fill between the gravel, improving the material density. The two work together to form a closely packed structure, enhancing the material strength. Moreover, the gravel and medium sand themselves have good volume stability, which can inhibit the deformation and cracking of the composite material after hardening.

[0008] As a mineral admixture, the fly ash can effectively reduce the porosity through its micro-aggregate filling effect, enhancing the material strength. Additionally, its particles are small and spherical, which can reduce the friction between particles and improve the material fluidity.

[0009] The inventors found through experiments that the solid waste-based materials such as solid waste-based sulfoaluminate cement and desulfurized building gypsum have the characteristics of early strength and slight expansion. When the mass ratio of the solid waste-based sulfoaluminate cement to the desulfurized building gypsum is 1:0.7 - 1, it can not only effectively improve the early strength performance of the composite material, significantly reduce the demolding time, and thus effectively improve the preparation efficiency; it can also significantly improve the mechanical properties of the prepared composite slabs, such as compressive and flexural strengths. In addition, it can significantly reduce the dry shrinkage rate of the composite slab material, ensure the connection quality at the joint with the steel bar truss, and effectively extend the service life of the truss composite slab.

[0010] Boric acid and gypsum retarder work together to adjust the setting time of the composite material, coordinating the time required for production and the rapid growth of early mechanical properties. In addition, the addition of boric acid can improve the dry shrinkage phenomenon of the composite material to a certain extent.

[0011] In some embodiments, the particle size of the medium sand is 0.3 - 4 mm.

[0012] In some embodiments, the particle size of the gravel is 5 - 10 mm.

[0013] In some embodiments, the specific surface area of the solid waste-based sulfoaluminate cement is not less than 400 m 2 / kg; the flexural and compressive strengths at 1 day are not less than 6.0 MPa and 35.0 MPa respectively, and the flexural and compressive strengths at 28 days are not less than 7.5 MPa and 50 MPa respectively.

[0014] In some embodiments, the content of hemihydrate gypsum in the desulfurized building gypsum is not less than 55%.

[0015] In some embodiments, the suspending agent is selected from at least one of hydroxypropyl methylcellulose, methylcellulose or ethylcellulose. The suspending agent is used to improve the water retention of the composite material and adjust the fluidity of the material.

[0016] In some embodiments, the defoaming agent is an inorganic silicon defoaming agent. The defoaming agent is used to promote the discharge of air bubbles in the composite material and improve the density and mechanical strength of the material.

[0017] In some embodiments, the gypsum retarder is a bone collagen-based retarder or / and a plant protein-based retarder.

[0018] In a second aspect, the present invention provides a method for preparing a solid waste-based quick-setting and crack-resistant truss composite slab, comprising the following steps: Mix the composite material for the solid waste-based quick-setting and crack-resistant truss composite slab evenly in proportion to obtain a mixed powder; Mix the mixed powder and water in a water-to-material ratio of 0.13 - 0.18:1 evenly to obtain a composite material slurry; Pour the composite material slurry into a mold, eliminate air bubbles, and scrape it flat to remove excess slurry; Embed the steel bar truss in the slurry in the mold, let it stand for a set time, then demold and cure, and that's it.

[0019] In some embodiments, the standing time is 3 - 5 h, preferably 4 h.

[0020] In some embodiments, the curing time is not less than 7 days, and the relative humidity in the room during curing is not less than 60%RH.

[0021] In a third aspect, the present invention provides a solid waste-based quick-setting and crack-resistant truss composite slab prepared by the preparation method.

[0022] The beneficial effects obtained by one or more of the above embodiments of the present invention are as follows: The solid waste-based sulfoaluminate cement and the desulfurized building gypsum hydrate rapidly in the early stage, generating a large number of ettringite crystals and gypsum dihydrate crystals respectively, enabling the composite material to obtain high mechanical strength in the early stage, shortening the demolding time, and improving the production efficiency. In addition, the formation reactions of ettringite and gypsum dihydrate crystals are both expansion reactions. The two are generated simultaneously and closely combined. By strictly controlling the ratio of the solid waste-based sulfoaluminate cement and the desulfurized building gypsum, the composite material can exhibit a micro-expansion characteristic, producing a compensating shrinkage effect, effectively improving the volume stability, and reducing the risks of expansion cracking and shrinkage cracking.

[0023] The present invention makes full use of the characteristics of solid waste-based materials such as solid waste-based sulphoaluminate cement and desulphurized building gypsum, which have early strength and slight expansion. By controlling the material ratio and combining additives such as polycarboxylate water reducer, defoamer, and retarder, the solid waste-based composite cementitious system materials have the performance characteristics of high early strength and volume stability.

[0024] The present invention has a fast hydration rate and a short setting time, and can be demoulded after 4 hours. The bottom plate and the steel bar truss are connected by an embedded method, which is simple to operate and saves the complex process of bolt connection.

[0025] In the main materials of the bottom plate of the composite slab of the present invention, the proportion of solid waste-based materials such as solid waste-based sulphoaluminate cement, desulphurized building gypsum, and fly ash is greater than 30%, which greatly reduces the production cost and provides a high-value utilization way for industrial solid waste. In addition, the calcination temperature of producing solid waste-based sulphoaluminate cement is 150-250°C lower than that of traditional Portland cement, and the carbon emission is lower, with significant environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0027] Figure 1 is the preparation flow chart of the steel bar truss composite slab of the present invention; Figure 2 is the construction effect drawing of Example 1 of the present invention; Figure 3 is the construction effect drawing of Comparative Example 2 of the present invention; Figure 4 is the construction effect drawing of Comparative Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0029] The present invention will be further described below in conjunction with embodiments.

[0030] Example 1 In this embodiment, the components of the composite material for the bottom plate of the laminated slab are put into a mixer and stirred evenly according to the following proportions to obtain a powder material: 105 kg of solid waste-based sulfoaluminate cement, 85 kg of desulfurized building gypsum, 45 kg of fly ash, 210 kg of medium sand, 110 kg of gravel, 1.1 kg of polycarboxylate water reducer, 0.1 kg of hydroxypropyl methylcellulose-based suspending agent, 0.4 kg of defoaming agent, 0.5 kg of boric acid, and 0.21 kg of plant protein-based gypsum retarder.

[0031] 80 kg of water is added to the mixer and stirred at a speed of 60 revolutions per minute for 3 minutes to obtain a composite material slurry. It is poured into a bottom plate mold of 3000×1200×25 mm, vibrated and leveled at a frequency of 2000 Hz, and then the steel bar truss is embedded in the composite material.

[0032] Take a part of the slurry from the mixer and pour it into a mold of 40×40×160 mm for testing the compressive and flexural strengths and dimensional change rate of the composite material. Demold after 4 hours of pouring.

[0033] The compressive and flexural strengths measured at 4h are 23.3 MPa and 4.9 MPa respectively.

[0034] The compressive and flexural strengths measured at 3d are 51.9 MPa and 11.4 MPa respectively.

[0035] The compressive and flexural strengths measured at 28d are 72.3 MPa and 12.8 MPa respectively.

[0036] The shrinkage rate measured at 28d is 0.03%.

[0037] The prepared steel bar truss laminated slab has a dense and complete appearance, without defects such as cracks, holes, and honeycombs, as Figure 2 shown.

[0038] Example 2 In this embodiment, the components of the composite material for the bottom plate of the laminated slab are put into a mixer and stirred evenly according to the following proportions to obtain a powder material: 90 kg of solid waste-based sulfoaluminate cement, 85 kg of desulfurized building gypsum, 55 kg of fly ash, 195 kg of medium sand, 123 kg of gravel, 0.8 kg of polycarboxylate water reducer, 0.1 kg of ethyl cellulose-based suspending agent, 0.3 kg of defoaming agent, 1.4 kg of boric acid, and 0.3 kg of bone glue protein-based gypsum retarder.

[0039] 75 kg of water is added to the mixer and stirred at a speed of 60 revolutions per minute for 3 minutes to obtain a composite material slurry. It is poured into a bottom plate mold of 3000×1200×25 mm, vibrated and leveled at a frequency of 2000 Hz, and then the steel bar truss is embedded in the composite material.

[0040] Take part of the slurry from the mixer and pour it into a mold of 40×40×160 mm to test the compressive and flexural strengths and the dimensional change rate of the composite material.

[0041] Demold after 4 hours of pouring.

[0042] The compressive and flexural strengths measured at 4h are 19.3 MPa and 4.4 MPa respectively.

[0043] The compressive and flexural strengths measured at 3d are 52.3 MPa and 10.1 MPa respectively.

[0044] The compressive and flexural strengths measured at 28d are 74.5 MPa and 11.7 MPa respectively.

[0045] The shrinkage rate measured at 28d is 0.01%.

[0046] The manufactured reinforced truss composite slab has a dense and complete appearance, without defects such as cracks, holes, and honeycombs.

[0047] Example 3 In this example, put each component of the composite material for the bottom slab of the composite slab into the mixer and stir evenly to obtain the powder material: 120 kg of solid waste-based sulphoaluminate cement, 87 kg of desulfurized building gypsum, 32 kg of fly ash, 180 kg of medium sand, 105 kg of stones, 1.0 kg of polycarboxylate water reducer, 0.02 kg of methyl cellulose-based suspending agent, 0.5 kg of defoaming agent, 0.1 kg of boric acid, and 0.15 kg of plant protein-based gypsum retarder.

[0048] Add 90 kg of water to the mixer, stir at a speed of 60 revolutions per minute for 3 minutes to obtain the composite material slurry, pour it into a bottom slab mold of 3000×1200×25 mm, vibrate and level it at a frequency of 2000 Hz, and then bury the steel truss in the composite material.

[0049] Take part of the slurry from the mixer and pour it into a mold of 40×40×160 mm to test the compressive and flexural strengths and the dimensional change rate of the composite material.

[0050] Demold after 4 hours of pouring. The compressive and flexural strengths measured at 4h are 20.9 MPa and 5.3 MPa respectively.

[0051] The compressive and flexural strengths measured at 3d are 55.3 MPa and 11.7 MPa respectively.

[0052] The compressive and flexural strengths measured at 28d are 77.5 MPa and 13.1 MPa respectively.

[0053] The shrinkage rate measured at 28d is 0.06%.

[0054] The prepared reinforced truss composite slab has a dense and complete appearance, without defects such as cracks, holes, and honeycombs, as Figure 1 shown.

[0055] Comparative Example 1 The difference from Example 1 is that 105 kg of solid waste-based sulphoaluminate cement is replaced with 90 kg of solid waste-based sulphoaluminate cement, and 85 kg of desulphurized building gypsum is replaced with 100 kg of desulphurized building gypsum (the mass ratio of solid waste-based sulphoaluminate cement to desulphurized building gypsum is less than 1:1). The rest are the same as in Example 1.

[0056] The compressive and flexural strengths measured at 4 h are 25.6 MPa and 5.5 MPa respectively.

[0057] The compressive and flexural strengths measured at 3 d are 50.9 MPa and 9.7 MPa respectively.

[0058] The compressive and flexural strengths measured at 28 d are 53.5 MPa and 7.5 MPa respectively.

[0059] The shrinkage rate measured at 28 d is -0.05%.

[0060] The prepared reinforced truss composite slab has no holes and honeycombs, but a large number of irregular cracks appear at 28 d.

[0061] Comparative Example 2 The difference from Example 1 is that the solid waste-based sulphoaluminate cement is replaced with commercially available sulphoaluminate cement (brand: Jiuqi Building Materials, model: R.SAC42.5). The rest are the same as in Example 1.

[0062] The compressive and flexural strengths measured at 4 h are 17.7 MPa and 4.3 MPa respectively.

[0063] The compressive and flexural strengths measured at 3 d are 45.3 MPa and 9.3 MPa respectively.

[0064] The compressive and flexural strengths measured at 28 d are 61.3 MPa and 11.6 MPa respectively.

[0065] The shrinkage rate measured at 28 d is 0.07%.

[0066] The prepared reinforced truss composite slab has no holes and honeycombs, but a small number of cracks appear along the distribution of the steel bars, as Figure 3 shown.

[0067] Comparative Example 3 The difference from Example 1 is that the solid waste-based sulphoaluminate cement is replaced with commercially available ordinary Portland cement (brand: Jiuqi Building Materials, model: P.O 42.5). The rest are the same as in Example 1.

[0068] The 4h sample has solidified but has not gained strength.

[0069] The compressive and flexural strengths measured at 3d are 28.8 MPa and 4.5 MPa respectively.

[0070] The compressive and flexural strengths measured at 28d are 73.7 MPa and 12.5 MPa respectively.

[0071] The shrinkage rate measured at 28d is 0.11%.

[0072] The fabricated reinforced truss composite slab has no holes or honeycombs, but there are a large number of through cracks along the direction of the steel bars. The effect is as Figure 4 shown.

[0073] Comparative Example 4 Compared with Example 1, the difference is that only boric acid is replaced with a plant protein-based gypsum retarder, and the others are the same as in Example 1.

[0074] The compressive and flexural strengths measured at 4h are 16.2 MPa and 3.8 MPa respectively.

[0075] The compressive and flexural strengths measured at 3d are 52.5 MPa and 10.3 MPa respectively.

[0076] The compressive and flexural strengths measured at 28d are 69.2 MPa and 11.8 MPa respectively.

[0077] The shrinkage rate measured at 28d is 0.09%.

[0078] Comparative Example 5 Compared with Example 1, the difference is that only the plant protein-based gypsum retarder is replaced with boric acid, and the others are the same as in Example 1.

[0079] The compressive and flexural strengths measured at 4h are 25.2 MPa and 4.8 MPa respectively.

[0080] The compressive and flexural strengths measured at 3d are 45.1 MPa and 9.2 MPa respectively.

[0081] The compressive and flexural strengths measured at 28d are 71.2 MPa and 12.3 MPa respectively.

[0082] The shrinkage rate measured at 28d is 0.04%.

[0083] Comparative Example 6 Compared with Example 1, the difference is that only fly ash is omitted, and the others are the same as in Example 1.

[0084] The compressive and flexural strengths measured at 4h are 20.1 MPa and 4.7 MPa respectively.

[0085] The compressive and flexural strengths measured by 3D are 47.6 MPa and 9.5 MPa respectively.

[0086] The compressive and flexural strengths measured by 28D are 63.9 MPa and 11.2 MPa respectively.

[0087] The shrinkage rate measured by 28D is 0.06%.

[0088] Table 1

[0089] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite material for a solid waste-based rapid-setting and crack-resistant truss composite slab, characterized in that: By mass fraction, it comprises the following components: 14 - 30 parts of solid waste-based sulphoaluminate cement, 10 - 25 parts of desulphurized building gypsum, 5 - 15 parts of fly ash, 30 - 45 parts of medium sand, 15 - 25 parts of gravel, 0.08 - 0.23 parts of polycarboxylate water reducer, 0 - 0.05 parts of suspending agent, 0.03 - 0.10 parts of defoaming agent, 0.05 - 0.55 parts of boric acid, 0.02 - 0.13 parts of gypsum retarder; The mass ratio of the solid waste-based sulphoaluminate cement to the desulphurized building gypsum is 1:0.7 - 1.

2. The composite material for the solid waste-based rapid-setting and crack-resistant truss composite slab according to claim 1, wherein: The particle size of the medium sand is 0.3 - 4 mm.

3. The composite material for solid waste-based rapid-setting crack-resistant truss composite slabs according to claim 1, wherein: The particle size of the gravel is 5 - 10 mm.

4. The composite material for the solid waste-based quick-setting and crack-resistant truss composite slab according to claim 1, wherein: The specific surface area of the solid waste-based sulphoaluminate cement is not less than 400 m 2 / kg; the flexural strength and compressive strength at 1 day are not less than 6.0 MPa and 35.0 MPa respectively, and the flexural strength and compressive strength at 28 days are not less than 7.5 MPa and 50 MPa respectively.

5. The composite material for the solid waste-based quick-setting and crack-resistant truss composite slab according to claim 1, wherein: The content of hemihydrate gypsum in the desulphurized building gypsum is not less than 55%.

6. The composite material for the solid waste-based rapid-setting and crack-resistant truss composite slab according to claim 1, wherein: The suspending agent is selected from at least one of hydroxypropyl methylcellulose, methylcellulose or ethylcellulose; Or, the defoaming agent is an inorganic silicon-based defoaming agent.

7. The composite material for solid waste-based fast-setting and crack-resistant truss composite slabs according to claim 1, wherein: The gypsum retarder is a bone glue protein-based retarder or / and a plant protein-based retarder.

8. A preparation method of a solid waste-based rapid-setting and crack-resistant truss composite slab, characterized in that: It comprises the following steps: Mix the composite material for solid waste-based quick-setting and crack-resistant truss composite slabs according to any one of claims 1 - 7 in proportion and uniformly to obtain a mixed powder; Mix the mixed powder with water at a water-to-material ratio of 0.13 - 0.18:1 and uniformly to obtain a composite material slurry; Pour the composite material slurry into a mold, remove air bubbles, and scrape to remove excess slurry; Embed a steel bar truss in the slurry in the mold, leave it to stand for a set time, then demold and cure, and that's it.

9. The preparation method of the solid waste-based rapid-setting crack-resistant truss composite slab according to claim 8, characterized in that: The standing time is 3 - 5 h; Or, the curing time is not less than 7 days, and the indoor relative humidity during curing is not less than 60%RH.

10. A solid waste-based quick-setting and crack-resistant truss composite slab, characterized in that: It is prepared by the preparation method according to claim 8 or 9.

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