Jet repair mortar based on solid waste-based sulphoaluminate cement and preparation method thereof

Abstract

The invention discloses a jet repair mortar based on solid waste-based sulphoaluminate cement and a preparation method thereof, the jet repair mortar comprises the following components in parts by mass: 35 to 50 parts of solid waste-based sulphoaluminate cement, 8 to 16 parts of quartz sand of 20 to 40 meshes, 20 to 35 parts of quartz sand of 40 to 80 meshes, 25 to 35 parts of quartz sand of 80 to 120 meshes, 0.8 to 1.2 parts of redispersible latex powder, 0.008 to 0.025 part of polycarboxylate superplasticizer, 0.05 to 0.12 part of suspending agent and 0.03 to 0.15 part of defoaming agent, 0 to 0.5 part of a retarder; 0.1 to 0.3 part of polypropylene fiber; the mass ratio of the solid waste-based sulphoaluminate cement to the quartz sand aggregate is (0.7-1): 1; the mass ratio of the polycarboxylate superplasticizer to the suspending agent is (0.1-0.5): 1; the ratio of water to material is 0.16 to 0.22. The spraying repair mortar has high thixotropy and high fluidity in the pumping stage and the spraying stage, after the mortar is sprayed to the wall face, shearing force borne by the mortar is reduced, a flocculation structure is rapidly formed in a cement-based material, the fluidity is reduced, and a repair layer is more stable.

Description

Technical Field

[0001] The present invention relates to the technical field of spray repair mortars, and in particular to a spray repair mortar based on solid waste-based sulphoaluminate cement and a preparation method thereof. Background Art

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

[0003] Repair techniques for facade concrete surface defects include plastering and sprayed mortar. Plastering is complex, time-consuming, and labor-intensive. Sprayed mortar typically uses a wet spraying process, using ordinary Portland cement, admixtures, sand and gravel aggregate, fiber, water reducer, and accelerator as raw materials. The cement, admixtures, sand and gravel aggregate fiber, and water reducer are first mixed uniformly and then stirred with water. Sprayed mortar is then piped onto the surface to be repaired. To ensure smooth pipe transportation, the mortar's fluidity needs to be increased. However, to prevent the mortar from dripping along the wall after spraying, the mortar's fluidity needs to be reduced. Consequently, there is a conflicting demand for the fluidity of sprayed mortar.

[0004] To address this conflict, existing technologies use a metering pump to add an accelerator to the nozzle. After spraying, the accelerator takes effect, causing the sprayed mortar to solidify quickly and prevent dripping. However, this approach presents challenges in controlling the amount and uniformity of the accelerator, leading to uneven mortar setting and cracking. Furthermore, the accelerator addition device is complex and expensive.

[0005] Improving thixotropy can enhance the fluidity of sprayed mortar during transportation and spraying, while reducing its fluidity when stationary after spraying. This "shear thinning-standing thickening" property offers a new approach to resolving the conflicting fluidity requirements of sprayed mortar. Currently, thixotropy is primarily achieved by incorporating expensive specialized thixotropic agents such as layered double hydroxides and nanoclays.

[0006] In addition, the existing technology mainly reduces costs and disposes of solid waste by directly adding industrial solid waste to the spray mortar. However, when industrial solid waste is used as an admixture, the amount of solid waste added is small and the activity is low, which is not conducive to the growth of the mechanical properties of the spray mortar. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a spray repair mortar based on solid waste-based sulphoaluminate cement and a preparation method thereof.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] In a first aspect, the present invention provides a spray repair mortar based on solid waste-based sulfoaluminate cement, comprising the following components, calculated by mass: 35 to 50 parts of solid waste-based sulfoaluminate cement, 8 to 16 parts of 20-40 mesh quartz sand, 20 to 35 parts of 40-80 mesh quartz sand, 25 to 35 parts of 80-120 mesh quartz sand, 0.8 to 1.2 parts of redispersible latex powder, 0.008 to 0.025 parts of polycarboxylate water reducer, 0.05 to 0.12 parts of suspending agent, 0.03 to 0.15 parts of defoaming agent, 0 to 0.5 parts of retarder, and 0.1 to 0.3 parts of polypropylene fiber;

[0010] The mass ratio of solid waste-based sulphoaluminate cement to quartz sand aggregate is 0.7 to 1:1;

[0011] The mass ratio of polycarboxylate water reducer to suspending agent is 0.1-0.5:1;

[0012] The water-to-material ratio is 0.16-0.22.

[0013] The water-to-material ratio is the ratio of the total water consumption to the dry weight of the mixed materials.

[0014] Quartz sand grading can form a dense stacking structure in the mortar, which increases the friction between particles when stationary and improves thixotropy.

[0015] The mass ratio of solid waste-based sulfoaluminate cement to quartz sand aggregate is 0.7 to 1:1. When the ratio is too large, the fluidity of the mortar decreases slowly when it is stationary. When the ratio is too small, the mortar requires greater shear force to increase its fluidity.

[0016] The mass ratio of polycarboxylate water-reducing agent to suspending agent is 0.1-0.5:1. When the ratio is too high, the fluidity of the sprayed mortar is difficult to reduce when it is stationary, which may cause the mortar to flow along the wall. When the ratio is too low, the fluidity of the sprayed mortar cannot be improved, which may cause difficulty in mortar transportation and blockage of the pipeline.

[0017] The water-to-material ratio is 0.16-0.22. The water-to-material ratio should be adapted to the mass ratio of polycarboxylic acid water-reducing agent and suspending agent. A suitable water-to-material ratio can enable the sprayed mortar to obtain a suitable fluidity variation range and avoid water seepage.

[0018] In the present invention, by regulating the fineness of solid waste-based sulfoaluminate cement and the grading of quartz sand aggregate, and coordinating the specific ratio of polycarboxylate water-reducing agent and suspending agent, the repair mortar has a higher thixotropy. The polycarboxylate water-reducing agent is mainly adsorbed on the surface of cement particles, and improves the fluidity of the mortar through steric hindrance and electrostatic repulsion, while the suspending agent is mainly distributed in the liquid phase, and forms a flocculation network through hydrogen bonds and van der Waals forces, thereby reducing the fluidity of the mortar. During the pumping and ejection stages, the sprayed mortar is subjected to a large shear force, and the flocculation effect of the suspending agent is weakened. The water-reducing agent plays a leading role, improving the fluidity of the mortar and making it have good transportability. After the mortar is sprayed onto the wall, the mortar is almost not subject to shear force. At this time, the suspending agent plays a leading role, quickly forming a flocculation network, locking free water, reducing fluidity, and allowing the mortar to obtain good wall-hanging stability.

[0019] The main mineral phases of solid waste-based sulphoaluminate cement include calcium sulphoaluminate, calcium sulfoferroaluminate, dicalcium silicate and iron phase. A large amount of ettringite is generated in the early stage of hydration, and the early strength develops rapidly. In the later stage of hydration, colloids such as iron glue, aluminum glue, and CSH gel are generated, which promotes the continuous growth of the later strength of the mortar. The cement is combined with admixtures to regulate the cement hydration rate, so that after the construction of the spray repair mortar, the strength of the repaired structure is rapidly improved, the later strength is high, the volume is stable, and it is not easy to crack.

[0020] In some embodiments, the composition of the solid waste-based sulphoaluminate cement includes: CaO 45-55%, SiO2 3-10%, Al2O3 10-20%, Fe2O3 6-15%, SO3 15-22%, where % is mass percentage.

[0021] Preferably, the specific surface area of the solid waste-based sulphoaluminate cement is not less than 400 m 2 / kg; the 1-day flexural and compressive strengths shall not be less than 6.0MPa and 35.0MPa respectively, and the 28-day flexural and compressive strengths shall not be less than 7.5MPa and 50MPa respectively.

[0022] In some embodiments, the mud content of the quartz sand is no more than 5%.

[0023] In some embodiments, the suspending agent is selected from at least one of hydroxypropyl methylcellulose, methylcellulose, or ethylcellulose.

[0024] Preferably, the viscosity of the suspending agent is 100,000 to 200,000.

[0025] In some embodiments, the defoaming agent is an inorganic silicone defoaming agent.

[0026] In some embodiments, the retarder is boric acid or citric acid.

[0027] In some embodiments, the length of the polypropylene fiber is 3 to 8 mm.

[0028] In some embodiments, the mass fraction of the retarder is 0.1 to 0.5 parts.

[0029] In a second aspect, the present invention provides a method for preparing the spray repair mortar based on solid waste-based sulphoaluminate cement, comprising the following steps:

[0030] Solid waste-based sulphoaluminate cement, quartz sand, redispersible latex powder, polycarboxylic acid water reducer, suspending agent, defoaming agent, retarder and polypropylene fiber are mixed in proportion, and then mixed with water in proportion; first, the mixture is stirred at a low speed of 300-600 rpm for 0.3-1 min, and then stirred at a high speed of 1000-1500 rpm for 2-3 min to obtain a spray repair mortar.

[0031] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0032] In the present invention, the performance characteristics of solid waste-based sulphoaluminate cement, such as early strength, rapid hardening and slight expansion, are fully utilized. By compounding the cement fineness, aggregate gradation, water reducer and suspending agent, the mortar is made highly thixotropic, without the need for a special thixotropic agent, which can effectively save costs.

[0033] The main cementitious material of the spray repair mortar prepared by the present invention is solid waste-based sulfoaluminate cement, which reduces production costs and effectively solves the problem of high-value utilization of solid waste. In addition, the calcination temperature for producing solid waste-based sulfoaluminate cement is 150 to 250°C lower than that of traditional silicate cement, and the carbon emissions are lower.

[0034] The sprayed repair mortar prepared by the present invention is easy to pump and spray, does not require an external accelerator during construction, and maintains a stable shape after spraying, does not sag, and facilitates construction. The sprayed mortar has advantages such as rapid early strength development, high thixotropy, and excellent crack resistance.

[0035] The spray repair mortar prepared by the present invention has very high flexural and compressive strengths: the flexural strengths after 1 day, 3 days and 28 days are respectively greater than 5MPa, 9MPa and 12MPa; the compressive strengths after 1 day, 3 days and 28 days are respectively greater than 35MPa, 40MPa and 60MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0037] Figure 1 This is a flow chart of the preparation and construction of the jet repair mortar of the present invention;

[0038] Figure 2This is a diagram showing the spraying effect of the repair mortar on a vertical concrete wall in Example 1 of the present invention;

[0039] Figure 3 This is a diagram showing the spraying effect of the repair mortar on the vertical concrete wall in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0040] 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 skilled in the art to which the present invention belongs.

[0041] The present invention will be further described below with reference to the embodiments.

[0042] Example 1

[0043] In this embodiment, the components of the spray repair mortar are placed in a mixer in the following proportions and stirred evenly to obtain mortar powder: 1000 g of solid waste-based sulphoaluminate cement, 1350 g of quartz sand (including 200 g of 20-40 mesh quartz sand, 500 g of 40-80 mesh quartz sand, and 650 g of 80-120 mesh quartz sand), 22 g of redispersible latex powder, 0.3 g of polycarboxylic acid high-efficiency water reducer, 1.6 g of inorganic silicone defoaming agent, 1.8 g of suspending agent hydroxypropyl methylcellulose, 6.3 g of retarder boric acid, and 5 g of 3-8 mm polypropylene staple fibers.

[0044] Pour 430g of water into the mixer, add the mixed spray repair mortar powder, stir at a low speed of 600rpm for 30s, then adjust the speed to 1000rpm and stir for 2 minutes and 30s.

[0045] The rebound rate test method is as follows: a rebound material collection device is laid under the spraying area. After the spraying is completed, the total amount of sprayed material used is recorded, and all rebound materials are collected and weighed. The rebound rate is the ratio of the mass of the rebound material to the total mass of the sprayed material.

[0046] The obtained repair mortar was pumped and sprayed on the vertical concrete wall. The spraying effect was good, the rebound rate was measured to be 5.3%, and no dripping occurred. The spraying effect was as follows: Figure 1 shown.

[0047] The repair mortar was poured into a 40×40×160mm rectangular test mold and demolded after 4 hours. The compressive and flexural strengths were measured at 36.0 MPa and 6.1 MPa, respectively, on day 1. At day 3, the compressive and flexural strengths were 55.7 MPa and 9.3 MPa, respectively. At day 28, the compressive and flexural strengths were 62.9 MPa and 12.8 MPa, respectively.

[0048] Example 2

[0049] In this embodiment, the components of the spray repair mortar are placed in a mixer in the following proportions and stirred evenly to obtain mortar powder: 950 g of solid waste-based sulphoaluminate cement, 1150 g of quartz sand (including 180 g of 20-40 mesh quartz sand, 430 g of 40-80 mesh quartz sand, and 540 g of 80-120 mesh quartz sand), 18 g of redispersible latex powder, 0.2 g of polycarboxylic acid high-efficiency water reducer, 1.8 g of inorganic silicone defoaming agent, 5.3 g of citric acid as a retarder, 4 g of polypropylene staple fiber, and 1.9 g of suspending agent hydroxypropyl methylcellulose.

[0050] Pour 400g of water into the mixer, add the mixed spray repair mortar powder, stir at a low speed of 400rpm for 30s, then adjust the speed to 1200rpm and stir for 2 minutes and 30s.

[0051] The obtained repair mortar was pumped and sprayed on a vertical concrete wall. The spraying effect was good, the rebound rate was measured to be 6.1%, and no dripping occurred.

[0052] The repair mortar was poured into a 40×40×160mm rectangular test mold and demolded after 4 hours. The compressive and flexural strengths were measured at 38.4MPa and 5.5MPa on day 1, 42.7MPa and 10.3MPa on day 3, and 65.7MPa and 12.2MPa on day 28.

[0053] Example 3

[0054] In this embodiment, the components of the spray repair mortar are placed in a mixer in the following proportions and stirred evenly to obtain mortar powder: 1200 g of solid waste-based sulphoaluminate cement, 1420 g of quartz sand (including 215 g of 20-40 mesh quartz sand, 540 g of 40-80 mesh quartz sand, and 665 g of 80-120 mesh quartz sand), 22 g of redispersible latex powder, 0.6 g of polycarboxylic acid high-efficiency water reducer, 1.5 g of inorganic silicone defoaming agent, 4.3 g of retarder boric acid, 5 g of polypropylene staple fiber, and 2.6 g of suspending agent methyl cellulose.

[0055] Pour 440g of water into the mixer, add the mixed spray repair mortar powder, stir at a low speed of 600rpm for 30s, then adjust the speed to 1500rpm and stir for 2 minutes and 30s.

[0056] The obtained repair mortar was pumped and sprayed on a vertical concrete wall. The spraying effect was good, the rebound rate was measured to be 5.7%, and no dripping occurred.

[0057] The repair mortar was poured into a 40×40×160mm rectangular test mold and demolded after 4 hours. The compressive and flexural strengths were measured at 36.8MPa and 7.6MPa, respectively, on day 1. At day 3, the compressive and flexural strengths were measured at 49.1MPa and 11.1MPa, respectively. At day 28, the compressive and flexural strengths were measured at 63.2MPa and 14.7MPa, respectively.

[0058] Comparative Example 1

[0059] The difference from Example 1 is that the quartz sand is replaced with 1350 g of 40-80 mesh quartz sand, and the rest is the same as Example 1.

[0060] The obtained repair mortar was pumped and sprayed on a vertical concrete wall. The rebound rate was measured to be high, 12.1%, and no dripping occurred.

[0061] The repair mortar was poured into a 40×40×160mm rectangular test mold and demolded after 4 hours. The compressive and flexural strengths were measured at 31.1 MPa and 3.5 MPa, respectively, on day 1. At day 3, the compressive and flexural strengths were measured at 45.6 MPa and 5.8 MPa, respectively. At day 28, the compressive and flexural strengths were measured at 51.9 MPa and 7.2 MPa, respectively.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that the solid waste-based sulphoaluminate cement is replaced by commercially available sulphoaluminate cement (brand: Jiuqi Building Materials, model: R.SAC42.5), and the rest is the same as Example 1.

[0064] The obtained repair mortar was pumped and sprayed on a vertical concrete wall. The measured rebound rate was slightly higher, 7.7%, and no dripping occurred.

[0065] The repair mortar was poured into a 40×40×160mm rectangular test mold and demolded after 4 hours. The compressive and flexural strengths were measured at 30.2MPa and 4.7MPa, respectively, on day 1. At day 3, the compressive and flexural strengths were measured at 47.5MPa and 6.6MPa, respectively. At day 28, the compressive and flexural strengths were measured at 51.3MPa and 10.1MPa, respectively.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that the solid waste-based sulfoaluminate cement is replaced with 1475 g of solid waste-based sulfoaluminate cement (the mass ratio of solid waste-based sulfoaluminate cement to quartz sand is greater than 1), and the rest is the same as Example 1.

[0068] The obtained repair mortar was pumped and sprayed on the vertical concrete wall. The rebound rate was measured to be 5.5%, and severe dripping occurred. Figure 3 shown.

[0069] The repair mortar was poured into a 40×40×160mm rectangular test mold and demolded after 4 hours. The compressive and flexural strengths were measured at 37.4MPa and 6.5MPa on day 1, 57.2MPa and 9.7MPa on day 3, and 59.8MPa and 12.3MPa on day 28.

[0070] Comparative Example 4

[0071] The difference from Example 1 is that 0.3g of polycarboxylate water reducer is replaced with 0.1g of polycarboxylate water reducer (the mass ratio of polycarboxylate water reducer to suspending agent is less than 0.1:1).

[0072] The resulting repair mortar is difficult to pump and difficult to spray.

[0073] The repair mortar was poured into a 40×40×160mm rectangular test mold and demolded after 4 hours. The compressive and flexural strengths were measured at 1 day, 28.9 MPa, and 4.6 MPa, respectively. At 3 days, the compressive and flexural strengths were measured at 43.2 MPa and 7.1 MPa, respectively. At 28 days, the compressive and flexural strengths were measured at 48.2 MPa and 9.8 MPa, respectively.

[0074] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A spray repair mortar based on solid waste-based sulphoaluminate cement, characterized by: The composition comprises the following components in parts by mass: 35-50 parts of solid waste-based sulphoaluminate cement, 8-16 parts of 20-40 mesh quartz sand, 20-35 parts of 40-80 mesh quartz sand, 25-35 parts of 80-120 mesh quartz sand, 0.8-1.2 parts of redispersible latex powder, 0.008-0.025 parts of polycarboxylate water reducer, 0.05-0.12 parts of suspending agent, 0.03-0.15 parts of defoaming agent, 0-0.5 parts of retarder, and 0.1-0.3 parts of polypropylene fiber. The mass ratio of solid waste-based sulphoaluminate cement to quartz sand aggregate is 0.7 to 1:1; The mass ratio of polycarboxylate water reducer to suspending agent is 0.1-0.5:1; The water-to-material ratio is 0.16-0.

22.

2. The spray repair mortar based on solid waste-based sulphoaluminate cement according to claim 1, characterized in that: The solid waste-based sulphoaluminate cement comprises: CaO 45-55%, SiO2 3-10%, Al2O3 10-20%, Fe2O3 6-15%, SO3 15-22%, where % is mass percentage.

3. The spray repair mortar based on solid waste-based sulphoaluminate cement according to claim 1, characterized in that: The mud content of the quartz sand is not more than 5%.

4. The spray repair mortar based on solid waste-based sulphoaluminate cement according to claim 1, characterized in that: The suspending agent is selected from at least one of hydroxypropyl methylcellulose, methylcellulose or ethylcellulose.

5. The spray repair mortar based on solid waste-based sulphoaluminate cement according to claim 4, characterized in that: The viscosity of the suspending agent is 100,000 to 200,000.

6. The spray repair mortar based on solid waste-based sulphoaluminate cement according to claim 1, characterized in that: The defoaming agent is an inorganic silicon defoaming agent.

7. The spray repair mortar based on solid waste-based sulphoaluminate cement according to claim 1, characterized in that: The retarder is boric acid or citric acid.

8. The spray repair mortar based on solid waste-based sulphoaluminate cement according to claim 1, characterized in that: The length of the polypropylene fiber is 3 to 8 mm.

9. The spray repair mortar based on solid waste-based sulphoaluminate cement according to claim 1, characterized in that: The mass fraction of the retarder is 0.1 to 0.5 parts.

10. The method for preparing the spray repair mortar based on solid waste-based sulphoaluminate cement according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: mixing solid waste-based sulphoaluminate cement, quartz sand, redispersible latex powder, polycarboxylate water reducer, suspending agent, defoaming agent, retarder and polypropylene fiber in proportion, and then mixing with water in proportion; first stirring at a low speed of 300-600 rpm for 0.3-1 min, and then stirring at a high speed of 1000-1500 rpm for 2-3 min to obtain spray repair mortar.

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