Alkali-free powdery quick-setting material

Abstract

The invention provides an early-strength quick-hardening alkali-free powdery quick-setting material and a preparation method thereof. The raw materials specifically comprise a flash coagulation component, a coagulation adjusting component, a drying and stabilizing component, a reinforcing component, a grinding aiding component and a thickening component. The percentage of each component is as follows: 45wt%-55wt% of the flash setting component, 3wt%-10wt% of the setting adjusting component, 5wt%-15wt% of the drying stabilizing component, 25wt%-35wt% of the reinforcing component, 1wt%-5wt% of the grinding aid component and 2wt%-8wt% of the thickening component. The early-strength quick-hardening alkali-free powdery quick-setting material disclosed by the invention can simultaneously meet the following requirements: (1) the initial setting time of neat paste is less than 2min, and the final setting time is less than 3min; (2) the 1d strength of the mortar is greater than 13MPa, the 28d compressive strength ratio is greater than 105%, and the 90d strength retention rate is greater than 110%; (3) the alkali content (in terms of Na2O equivalent) is lower than 0.5%; (4) the compatibility with cement of different manufacturers is good, the use dosage is low, and good popularization and application values are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of new materials for shotcrete in traffic engineering, and particularly relates to an alkali-free powdered quick-setting material. Background Art

[0002] As an important component of the composite lining structure of the tunnel, shotcrete not only needs to bear all the loads in the construction stage, but also needs to bear the main loads in the operation stage. At present, traffic engineering is gradually eliminating alkali-containing accelerators, and liquid accelerators are gradually developing towards alkali-free. Compared with liquid alkali-containing accelerators, the cost of liquid alkali-free accelerators has increased significantly. The reason is that liquid alkali-free accelerators must add stabilizing components (accounting for about 30% of the production cost) to ensure that their stability meets the requirements. At the same time, in order to reduce the viscosity of the accelerator and ensure the extraction effect of the peristaltic pump, the solid content of the liquid accelerator is generally 35%~45%, and the recommended dosage is 7%~9%. This means that in addition to the effective quick-setting components, the amount of water introduced into the liquid accelerator accounts for about 3.85%~5.85% of the total amount of concrete cementitious materials, which is equivalent to increasing the water-cement ratio of shotcrete by 0.04~0.06, which will seriously affect the setting time, strength development and durability of shotcrete. Under high-cold and low-temperature conditions, most liquid quick-setting agents will also have problems such as segregation, stratification and crystallization, which will seriously affect their use effect; in water-rich areas of broken surrounding rock tunnels, the setting time of liquid alkali-free quick-setting agents cannot meet on-site needs at all.

[0003] In the prior art, Chinese patent CN 110204238B discloses a water-soluble powdered alkali-free quick-setting agent and a preparation method thereof, wherein the powdered alkali-free quick-setting agent and water are mixed in a mass ratio of 1:0.8 to 1:1.5 to prepare an alkali-free liquid quick-setting agent for use, but the adverse effects of the additional amount of water introduced into the liquid quick-setting agent on the setting time, strength development and durability of the shotcrete are not overcome. Chinese patent CN102964076B discloses an alkali-free and chlorine-free enhanced powdered quick-setting agent, the raw materials of which include gypsum, powdered aluminum sulfate and sulphoaluminate cement, and the dosage of the quick-setting agent must account for more than 10% of the cement mass, and the technical and economic performance is poor. Only the performance test results of the quick-setting agent such as the setting time of the pure slurry and the mortar strength are introduced, and the actual application effect of the quick-setting agent in shotcrete, such as the spraying rebound rate and the 28d electrical flux, are not explained. Chinese patent CN112142359B discloses a powdered alkali-free accelerator for both dry and wet concrete spraying. The raw materials include aluminum sulfate, fluorosilicate, by-product silicon dioxide and solid alcohol amine. The problem that the setting time of such accelerator is greatly affected by the external temperature and moisture is not solved. The powdered aluminum sulfate in the raw material is easy to absorb moisture in the air. The final setting time of the accelerator under low dosage conditions is generally 5min~8min, which is difficult to meet the construction needs of shotcrete in low temperature, large deformation and water-rich areas. Chinese patent CN113024147B provides an alkali-free powdered accelerating setting agent for shotcrete and a preparation method thereof, wherein the main active components are inorganic compounds such as aluminum hydroxide, aluminum sulfate, and soda ash. The problem that the setting time of such accelerating setting agent is greatly affected by the external temperature and moisture is also not solved. Powdered aluminum sulfate easily absorbs moisture in the air. The initial setting time of the accelerating setting agent at a dosage of 4% is generally 2min~4min, and the final setting time is generally 5min~8min. Moreover, the spraying rebound rate is still at a level of about 10%, which is difficult to meet the construction needs of shotcrete in low temperature, large deformation, and water-rich areas. Summary of the invention

[0004] The invention aims to provide an alkali-free powdered quick-setting material to solve the problems of slow setting speed, slow early strength development, difficult operation with water, and high construction rebound rate of shotcrete in tunnels with low temperature, large deformation, and water-rich areas.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: By improving the setting and hardening mechanism of the quick-setting material and changing the main active component type in the quick-setting material, the problem that the setting effect of the traditional powdered quick-setting material is greatly affected by the external environment temperature and moisture is overcome. That is, the alkali-free powdered quick-setting material described in the present invention includes a flash setting component, a setting adjustment component, a drying component, a reinforcing component, a grinding aid component and a thickening component. The flash setting component is mainly amorphous 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3, CaO·2Al2O3, CaO·6Al2O3 and α-Al2O3 with a certain fineness. It has self-hydration and is less affected by the external temperature and moisture. It can undergo hydration reaction after contacting with water in concrete, thereby driving the hydration reaction process of silicate cement, thereby achieving the technical effect of flash setting. The main function of the regulating component is to make the setting speed of the alkali-free powdered quick-setting material controllable. The main function of the drying component is to ensure that the flash-setting component will not be affected by the moisture in the environment during storage and will not absorb moisture and agglomerate. The main function of the reinforcing component is to ensure that the alkali-free quick-setting material can provide sufficient aluminum phase material to promote the hydration of silicate cement after the self-hydration reaction. The main function of the grinding-aiding component is to reduce the energy consumption and time of grinding the alkali-free powdered quick-setting material to a specified fineness. The main function of the thickening component is to increase the overall cohesion of the sprayed material after the alkali-free powdered quick-setting material contacts the concrete, thereby reducing the rebound rate.

[0006] Specifically, an alkali-free powdered quick-setting material includes the following components: 45-55 flash setting components: 3-10 adjusting setting components: 5-15 drying components: 25-35 reinforcing components: 3-10 grinding aid components: 2-8 thickening components.

[0007] Furthermore, the flash condensation component in the present invention is one or more of 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3, CaO·2Al2O3, CaO·6Al2O3 and α-Al2O3 in an amorphous state with a certain fineness, and the preparation method thereof is: Step 1: Ore selection and batching. The ore includes bauxite, high calcium limestone and corundum, and the ore is batched according to a pre-selected ratio; Step 2: Electric furnace smelting: put the prepared raw ore into the electric furnace for smelting, the smelting temperature is controlled at 1350℃~1550℃, and the smelting time is not less than 200min; Step 3: Rapid cooling: After smelting, rapid cooling is performed at a cooling rate of 60°C / h~80°C / h to about 25°C; Step 4: Grind into powder, put the cooled material into a ball mill for grinding, adjust the ratio of steel balls and steel segments, and control the fineness of the ground powder to be no less than 300 meshes; Furthermore, the setting adjustment component in the present invention is one of dihydrate gypsum, anhydrous gypsum, hemihydrate gypsum, borax, tartaric acid or a mixture thereof in any proportion, wherein the proportion of dihydrate gypsum is not less than 40%; Furthermore, the dry component in the present invention is one of nano silicon dioxide, ground slag powder, ultrafine fly ash, limestone powder, modified metakaolin, zeolite powder or a mixture thereof in any proportion, wherein the proportion of nano silicon dioxide is not less than 50%; Furthermore, the reinforcing component in the present invention is one of aluminum sulfate, magnesium sulfate, lithium silicate, calcium hydroxide, magnesium fluorosilicate or a mixture thereof in any proportion, wherein the proportion of aluminum sulfate is not less than 65%; Furthermore, the grinding aid component in the present invention is one of triethanolamine, diethanol monoisopropanolamine, magnesium thiocyanate, zirconium dioxide or a mixture thereof in any proportion, wherein the proportion of diethanol monoisopropanolamine is not less than 45%; Furthermore, the thickening component in the present invention is one of cellulose ether, polyacrylamide, acrylic rubber powder, polyvinyl alcohol, bentonite or a mixture thereof in any proportion, wherein the proportion of cellulose ether is not less than 30%.

[0008] Furthermore, the above-mentioned bauxite is special grade or grade I bauxite clinker with W (Al2O3 / SiO2) ≥ 15%, and the CaCO3 content in the high-calcium limestone is not less than 85%.

[0009] Furthermore, the nano-silicon dioxide is preferably a hydrophilic gas phase, and has a specific surface area of ​​not less than 20000m 2 / kg of material.

[0010] Furthermore, the aluminum sulfate preferably has a fineness of 100-200 mesh and a moisture content not exceeding 10%.

[0011] Furthermore, the cellulose ether is preferably hydroxypropyl methylcellulose, and the molecular weight is not less than 50,000.

[0012] Furthermore, the mass ratio of the alkali-free powdered quick-setting material to cement in shotcrete is 2-5:95-98.

[0013] The use of the alkali-free powdered quick-setting material described in the present invention can effectively shorten the setting time of shotcrete, improve the early strength, and solve the problems of difficult water-carrying operation and high rebound rate of shotcrete under the condition of stranded water with a diameter not exceeding 4 cm. Specifically, the compatibility between the alkali-free powdered quick-setting agent and cement is universal. According to the relevant test methods in "Accelerator for Shotcrete" GB / T 35159, the initial setting time of the net slurry is less than 2 minutes, the final setting time is less than 3 minutes, the 1d strength of the mortar is greater than 13MPa, the 28d compressive strength ratio is greater than 105%, and the 90d strength retention rate is greater than 110%.

[0014] Compared with the prior art, the present invention is beneficial in that: 1 The flash setting components are different from inorganic substances such as aluminum hydroxide and aluminum sulfate used in other technologies. Instead, they are made of self-hydraulic amorphous 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3, CaO·2Al2O3, CaO·6Al2O3 and α-Al2O3 mineral materials. Their reaction with the silicate cement system is less affected by external temperature and moisture, so the setting time is faster and the early strength development is higher.

[0015] 2. The addition of dry components solves the problem that amorphous 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3, CaO·2Al2O3, CaO·6Al2O3 and α-Al2O3 mineral materials are easy to absorb moisture and agglomerate, and have poor storage stability, and can extend the storage shelf life of the alkali-free powdered quick-setting material of the present invention to more than 1 year.

[0016] 3. The addition of thickening components solves the problems of poor cohesion and granularity at the discharge port of shotcrete, and further reduces the rebound rate of shotcrete. DETAILED DESCRIPTION

[0017] In order to better illustrate the features of the present invention, the content of the invention will be described below in conjunction with specific embodiments, but the content of the present invention is not limited to the content of the embodiments.

[0018] The percentages described in the present invention are all mass percentages unless otherwise specified. The raw materials described can be obtained from public commercial channels unless otherwise specified. The embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation process examples are given to help understand the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0019] The raw material formula of the alkali-free powdered quick-setting material of Examples 1-6 is shown in Table 1: Table 1 Alkali-free powdered quick-setting material raw material formula of Examples 1-6 The alkali-free powdered quick-setting materials of Examples 1-6 were tested according to the test methods for alkali content, slurry setting time and mortar strength in "Accelerator for Shotcrete" GB / T 35159, and the main performance test results of the alkali-free powdered quick-setting materials of Examples 1-6 are shown in Table 2: Table 2 Main performance test results of alkali-free powdered quick-setting materials of Examples 1-6 The adaptability of the alkali-free powdered quick-setting materials of Examples 1-6 to cements of different manufacturers was analyzed. The test results of the setting time of the slurry and the mortar strength are shown in Table 3: Table 3 Compatibility of alkali-free powdered quick-setting materials of Examples 1-6 with cement from different manufacturers It can be seen from Table 3 that the alkali-free powdered quick-setting material of the present invention can still show good adaptability to cement of different brands from different origins under the condition of a dosage range of 2% to 5%, and the slurry setting time and mortar strength can meet the requirements of on-site construction and technical inspection.

[0020] The alkali-free powdered quick-setting materials of Examples 1-6 were subjected to a shotcrete test, with the quick-setting material dosage being 4% of the cement mass. The test was conducted using a wet spraying process, and the quick-setting material was added at the nozzle. The test site was IV (a) grade surrounding rock, the ambient temperature was 15°C~18°C, and there was water seepage in the surrounding rock. In order to compare the test results, Example 1 was compared with an alkali-free powdered quick-setting agent produced by a company in Yunnan, Example 2 was compared with an alkali-free powdered quick-setting agent produced by a company in Wuhan, and Example 3 was compared with an alkali-free powdered quick-setting agent produced by a company in Jiangsu. Other test raw materials include: Basu Conch low-alkali 42.5 grade ordinary Portland cement; machine-made sand with a fineness modulus of 2.9 and a stone powder content of 7%; 5~10mm continuously graded crushed stone; and polycarboxylic acid high-performance water reducer produced by a company in Anhui.

[0021] The mix ratio of shotcrete in the test is shown in Table 4: Table 4 Sprayed concrete mix ratios of Examples 1-6 and Comparative Examples 1-3 The test results of main performance indicators such as strength, rebound rate, density, etc. of shotcrete implemented in Examples 1-6 and Comparative Examples 1-3 are shown in Table 5: Table 5 Main performance test results of shotcrete of Examples 1-6 and Comparative Examples 1-3 As can be seen from Table 5, the alkali-free powdered quick-setting material of the present invention is superior to the comparative example in terms of compressive strength of shotcrete at various ages, shot rebound rate, one-time shot thickness and 28d electrical flux, indicating that the performance of the alkali-free powdered quick-setting material of the present invention is significantly better than other products on the market.

[0022] The above are only some specific embodiments of the present invention (since the formula of the present invention belongs to the numerical range, the embodiments cannot be exhaustive, and the protection scope recorded in the present invention is based on the numerical range and other technical key points of the present invention). The specific content or common sense known in the scheme is not described in detail here. It should be pointed out that the above embodiments do not limit the present invention in any way. For those skilled in the art, all technical solutions obtained by equivalent replacement or equivalent transformation fall within the protection scope of the present invention. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

[0023] Table 1 Raw material formula of alkali-free powdered quick-setting material of Examples 1-6

[0024] Table 2 Performance test results of alkali-free powdered quick-setting materials of Examples 1-6 Table 3 Compatibility of alkali-free powdered quick-setting materials of Examples 1-6 with cement Table 4 Sprayed concrete mix ratios of Examples 1-6 and Comparative Examples 1-3 cement sand gravel water Water reducing agent Accelerator 451 963 757 156 4.51 18.04 Table 5 Main performance test results of shotcrete of Examples 1-6 and Comparative Examples 1-3

Claims

1. An alkali-free powdered quick-setting material, characterized in that: The quick-setting material comprises a flash setting component, a setting adjustment component, a drying component, a reinforcing component, a grinding aid component and a thickening component, wherein the mass ratio of the flash setting component is 45-55: the setting adjustment component is 3-10: the drying component is 5-15: the reinforcing component is 25-35: the grinding aid component is 3-10: the thickening component is 2-8; The flash condensation component is one or more of 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3, CaO·2Al2O3, CaO·6Al2O3 and α-Al2O3 in an amorphous state with a certain fineness, and the preparation method thereof is as follows: Step 1: Ore selection and batching. The ore includes bauxite, high calcium limestone and corundum, and the ore is batched according to a pre-selected ratio; Step 2: Electric furnace smelting: put the prepared raw ore into the electric furnace for smelting, the smelting temperature is controlled at 1350℃~1550℃, and the smelting time is not less than 200min; Step 3: Rapid cooling: After smelting, rapid cooling is performed at a cooling rate of 60°C / h~80°C / h to about 25°C; Step 4: Grind into powder, put the cooled material into a ball mill for grinding, adjust the ratio of steel balls and steel segments, and control the fineness of the ground powder to be no less than 300 meshes; The setting adjustment component is one of dihydrate gypsum, anhydrous gypsum, hemihydrate gypsum, borax, tartaric acid or a mixture thereof in any proportion, wherein the proportion of dihydrate gypsum is not less than 40%; The dry component is one of nano silicon dioxide, ground slag powder, ultrafine fly ash, limestone powder, modified metakaolin, zeolite powder or a mixture thereof in any proportion, wherein the proportion of nano silicon dioxide is not less than 50%; The reinforcing component is one of aluminum sulfate, magnesium sulfate, lithium silicate, calcium hydroxide, magnesium fluorosilicate or a mixture thereof in any proportion, wherein the proportion of aluminum sulfate is not less than 65%; The grinding aid component is one of triethanolamine, diethanol monoisopropanolamine, magnesium thiocyanate, zirconium dioxide or a mixture thereof in any proportion, wherein the proportion of diethanol monoisopropanolamine is not less than 45%; The thickening component is one of cellulose ether, polyacrylamide, acrylic rubber powder, polyvinyl alcohol, bentonite or a mixture thereof in any proportion, wherein the proportion of cellulose ether is not less than 30%.

2. The alkali-free powdered quick-setting material according to claim 1, characterized in that: The bauxite is special grade or grade I bauxite clinker with W (Al2O3 / SiO2) ≥ 15%, and the CaCO3 content in the high calcium limestone is not less than 85%.

3. The alkali-free powdered quick-setting material according to claim 1, characterized in that: The nano-silicon dioxide is preferably a hydrophilic gas phase, and has a specific surface area of ​​not less than 20000m 2 / kg of material.

4. The alkali-free powdered quick-setting material according to claim 1, characterized in that: The aluminum sulfate preferably has a fineness of 100-200 mesh and a moisture content of no more than 10%.

5. The alkali-free powdered quick-setting material according to claim 1, characterized in that: The cellulose ether is preferably hydroxypropyl methylcellulose, and the molecular weight is not less than 50,000.

6. The alkali-free powdered quick-setting material according to claim 1, characterized in that: The mass ratio of the alkali-free powdered quick-setting material to the cement in the shotcrete is 2-5:95-98.

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