240h ​​ultra-slow-setting dry-mixed wet-spraying material for underground engineering and preparation method thereof

Abstract

The invention discloses a 240h ultra-slow-setting dry-mixed wet spraying material and a preparation method for underground engineering, comprising the following components: by weight, 100-105 parts of silicate cement, 280-285 parts of pre-screening soil and stone waste, 25-30 parts of fly ash, 4-6 parts of quick-setting agent, 40-50 parts of mixing water, based on the mass of PO 42.5 R silicate cement, and also comprising 4% to 5% of compound retarder. The unique slow-setting component of the present invention prolongs the transportation time of shotcrete, so that the material does not need to be piled up underground, and the situation of random stacking and cement failure of the material is avoided. The pre-screening soil and stone waste and fly ash in the material of the present invention are both solid waste-based materials. The two are used as the main components of shotcrete, which alleviates the supply pressure of natural sand and gravel, machine-made sand and gravel and cement, turns waste into treasure, and improves resource utilization.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete preparation, and in particular relates to a 240h ultra-slow-setting dry-mix wet-spraying material for underground engineering and a preparation method thereof. Background Art

[0002] Since its application in the Mill Tunnel in 1953, shotcrete has been widely used in water conservancy, tunnels, mines and other projects. In the traditional shotcrete construction of mine shafts and underground projects, most projects choose to use manual on-site mixing, which has some problems. 1. The mass counting of shotcrete materials is inaccurate and does not meet the deviation range of ±3% specified in the "Concrete Quality Control Standard" (GB50164-92); 2. During the construction of underground shotcrete, there is a lot of dust, which will cause irreversible damage to the health of construction workers; 3. During the construction of underground shotcrete, all materials are manually operated from preparation to use, and the tunnels are crowded, materials are piled up randomly, and the work efficiency is extremely low; 4. The underground environment is humid, the air contains a lot of moisture, and the bagged cement is stored underground. When used during construction, cement will agglomerate and fail. Based on the defects of traditional shotcrete materials and processes, the present invention proposes a 240h ultra-slow-setting waste base dry-mixed wet shotcrete material for underground engineering, which can simplify the underground construction process, improve the underground construction efficiency, reduce the cost of shotcrete, reduce the amount of dust and improve the underground working environment. Summary of the invention

[0003] The purpose of the present invention is to replace sand and gravel aggregate with pre-screening soil and stone waste (whose composition is similar to sand and gravel), which is one of the solid waste-based materials, and then add fly ash, a solid waste-based material, to improve the strength of shotcrete, and finally add a compound retarder and other concrete admixtures to prepare a 240h super-slow-setting solid waste-based dry-mixed wet spraying material for underground engineering. The material can improve resource utilization, reduce the cost of underground spraying, simplify the underground spraying process, increase the underground transportation time, and enhance the later strength of the shotcrete.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A 240h super slow setting dry-mix wet spraying material for underground engineering, characterized by comprising the following components: by weight, 100-105 parts of silicate cement, 280-285 parts of pre-screened soil and stone waste, 25-30 parts of fly ash, 4-6 parts of accelerator, 40-50 parts of mixing water, based on the mass of PO 42.5R silicate cement, and also comprising 4% to 5% of compound retarder.

[0006] Preferably, in parts by weight, PO 42.5R silicate cement 100-105 parts, pre-screened soil and stone waste 280-285 parts, Class II fly ash 25-30 parts, accelerator 4-6 parts, water 40-50 parts, based on the mass of PO 42.5R silicate cement, also includes 5% of compound retarder.

[0007] Furthermore, the compound retarder is composed of white sugar, sodium hexametaphosphate, collapse-retaining polycarboxylate water-reducing agent and high water-reducing polycarboxylate water-reducing agent in a mass ratio of 1:5.81:1.63:14.65.

[0008] Furthermore, the preparation method of the compound retarder is as follows: at standard room temperature, white powdery sodium hexametaphosphate and white crystalline sugar are weighed according to a matching ratio and poured into a glass beaker filled with deionized water, and stirred in a clockwise direction with a glass rod until there is no precipitation, and then a collapse-retaining polycarboxylic acid water-reducing agent and a high water-reducing polycarboxylic acid water-reducing agent are added, and stirred evenly until colorless and transparent to obtain the compound retarder; the amount of deionized water is deducted from the mixing water, and the amount of deionized water is 4% to 5% of the mass of the soil and stone waste before screening.

[0009] Furthermore, the collapse-retaining polycarboxylate water-reducing agent is prepared by diluting the collapse-retaining polycarboxylate water-reducing mother liquor and deionized water in a mass ratio of 1:(4-5); the high water-reducing polycarboxylate water-reducing agent is prepared by diluting the high water-reducing polycarboxylate water-reducing mother liquor and deionized water in a mass ratio of 1:(4-5).

[0010] The preparation method of the 240h super-slow-setting dry-mixed wet spraying material for underground engineering of the present invention comprises the following steps: weighing PO 42.5R silicate cement, pre-screened soil and stone waste, and fly ash according to the mix ratio, pouring them into a forced single-horizontal-shaft concrete mixer and stirring for 2 minutes until they are fully mixed and uniform, then adding a compound retarder while stirring, stirring for another 2 minutes, and finally putting it into a woven bag and sealing it to obtain the 240h super-slow-setting waste-based dry-mixed wet spraying material for underground engineering.

[0011] Preferably, the mass ratio of the PO 42.5R silicate cement: pre-screened soil and stone waste: fly ash is 1:2.86:0.25.

[0012] The present invention also provides a shotcrete made of the 240h super slow setting dry-mix wet shotcrete material for underground engineering. Based on the mass of PO 42.5R silicate cement, the shotcrete also includes 0.06% to 0.09% of a defoamer, 0.05% to 0.25% of an air entraining agent, 0.2% to 0.3% of a foam stabilizer, and 1.5% to 2.5% of an early strength agent.

[0013] Among them, the PO 42.5R silicate cement used conforms to the cement specified in Appendix A of GB 8076-2008 "Concrete Admixtures";

[0014] The pre-screening soil and stone waste used is in the range of medium-grade machine-made sand Class II sand, with good particle gradation; the deionized water used to prepare the solution complies with the "China Deionized Water Standard" GB / T 1146.1-1997; the mixing water used complies with the technical requirements of JGJ63-2006 "Concrete Water Standard", and all admixture tests comply with the specification GB 8076-2008 "Concrete Admixtures".

[0015] The four main components of the compound retarder are high water-reducing polycarboxylic acid water-reducing mother liquor, slump-retaining polycarboxylic acid water-reducing mother liquor, sodium hexametaphosphate and sugar. The four components are added with deionized water and prepared into a solution in a certain proportion; the air entraining agent uses k12 (sodium dodecyl sulfate); the early strength agent uses chloride early strength agent CaCl2; the defoamer uses organosilicon concrete defoamer. The functions of the above various admixtures are as follows:

[0016] Compound retarder: Within 240 hours, the ultra-slow solid waste-based dry-mixed wet spraying material added with the compound retarder will not undergo cement hydration reaction, and the cement will not fail. The present invention uses a polycarboxylic acid water reducer that has a better water-reducing effect than a naphthalene water reducer and has a certain retarding effect, among which the collapse-retaining polycarboxylic acid water-reducing mother liquor has a collapse-retaining performance, and the slump loss of the concrete mixture over time is greatly reduced. Considering the price and retarding effect, the phosphoric acid retarder sodium hexametaphosphate and the disaccharide retarder white sugar are selected as the main retarding components of the compound retarder to achieve the effect of extending the induction period of cement hydration and delaying the cement hydration process.

[0017] Defoamer: Defoamer can inhibit the generation of bubbles and eliminate irregular bubbles in fresh concrete caused by polycarboxylic acid water reducer. It not only makes the fluidity of fresh concrete stronger, but also reduces the honeycomb on the concrete surface and enhances the strength of concrete.

[0018] Air entraining agent: After adding defoaming agent, the bubbles in fresh concrete are reduced and the viscosity of fresh concrete is high. In order to ensure the workability of fresh concrete, air entraining agent needs to be added. During the concrete mixing process, a large number of evenly distributed, closed and stable tiny bubbles are introduced to the air-liquid interface to improve the cohesion and appearance quality of the concrete.

[0019] Foam stabilizer: The foam stabilizer is adsorbed on the gas-liquid interface, which further reduces the surface tension of the bubbles. The adsorbed foam stabilizer molecules have a protective effect on the liquid film, allowing the liquid film to reach a viscosity suitable for the long-term existence of bubbles, making the liquid film more solid, thereby playing a foam stabilizing role.

[0020] Early strength agent: After adding chloride early strength agent, chloride can react with C3A and Ca(OH)2 to form calcium aluminum hydrotalcite, which increases the solid ratio and plays a skeleton role on the one hand, and reduces the generation of products such as CH, accelerating the hydration process of C3A and C3S. At the same time, it can also promote the dissociation rate of silicate cement clinker minerals. Chloride enhances the effect of promoting cement hydration with the increase of cationic radius and the enhancement of metallic properties, accelerates cement hydration, and can also improve the strength of shotcrete and ensure the support quality of the tunnel.

[0021] Accelerator: The fineness of the accelerator used is less than 12.6%, the initial setting time is 2-3min, the final setting time is 8-10min, and the 1d compressive strength is greater than 8MPa. It can accelerate the hydration and hardening of cement and form sufficient strength in a very short time, but after adding the accelerator, the growth of the later strength of the shotcrete is reduced to a certain extent.

[0022] Compared with traditional shotcrete materials, the 240h ultra-slow-setting waste base dry-mixed wet shotcrete material for underground engineering proposed in the present invention has the following beneficial effects:

[0023] 1. The materials of the present invention are precisely weighed on the ground according to the mix ratio design and then intelligently operated using a twin-horizontal-shaft tank mixer, thereby solving the problems of inaccurate measurement and uneven mixing of traditional shotcrete materials.

[0024] 2. The material of the present invention uses pre-screened soil and stone waste with a high moisture content as coarse aggregate for shotcrete, which greatly reduces the dust concentration during spraying, thereby ensuring a relatively high-quality construction environment and the health of construction workers.

[0025] 3. The material of the present invention is easy to use, and the unique retarding component prolongs the transportation time of shotcrete, so that the material does not need to be piled up underground, avoiding the situation of random stacking of materials and cement failure, and the work site becomes spacious.

[0026] 4. When the material described in the present invention is used, the process is simple and the efficiency is improved. Only 2 to 3 people are needed to meet the construction requirements, which meets the notice of the State Administration of Coal Mine Safety Supervision on "Limited Number of Personnel for Single-Shift Operations in Coal Mines (Trial)" issued on December 25, 2018.

[0027] 5. The pre-screening soil and stone waste and fly ash in the material described in the present invention are both solid waste-based materials. Using the two as the main components of shotcrete can alleviate the supply pressure of natural sand and gravel, machine-made sand and gravel and cement, turn waste into treasure, and improve resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the state of each test group's super slow-setting dry-mixed wet spraying material after storage for 240 hours.

[0029] Figure 2 is the state of fresh concrete in each test group. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention, and those skilled in the art in this field can make some non-essential improvements and adjustments based on the content of the above invention.

[0031] The sources of materials used in the present invention are as follows:

[0032] Sodium hexametaphosphate produced by Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.; (10,000 yuan / ton)

[0033] White sugar produced by Tianjin Komiou Chemical Reagent Co., Ltd. (4,000 yuan / ton)

[0034] Sodium tripolyphosphate produced by Hongyan Reagent Factory in Hedong District, Tianjin; (10,300 yuan / ton)

[0035] Sodium gluconate produced by Shandong Fuyang Biotechnology Co., Ltd.; (4,800 yuan / ton)

[0036] Collapse-resistant polycarboxylic acid water-reducing concentrate and high water-reducing polycarboxylic acid water-reducing concentrate produced by Hunan Zhongyan Building Materials Technology Co., Ltd.

[0037] Silicone concrete defoamers produced by Laiyang Hongxiang Building Admixture Factory; sodium lauryl sulfate produced by Tianjin Zhiyuan Chemical Reagent Co., Ltd.; anhydrous calcium chloride produced by Sinopharm Chemical Reagent Co., Ltd.;

[0038] A new generation of accelerating setting agent produced by Hongfu Building Additives Factory in Dongying District; deionized water produced by Jiangsu Shuyang Xizhimeng Trading Co., Ltd.;

[0039] The soil and rock waste materials are pre-screened soil and rock waste materials provided by Jiaozuo Qianye New Materials Co., Ltd. Unless otherwise specified, other raw materials are commercially available products.

[0040] The experimental mix ratios of the present invention are shown in Table 1 below:

[0041] Table 1 Test mix design

[0042]

[0043]

[0044] Note: FA in the table refers to fly ash, PCE refers to water-reducing polycarboxylate superplasticizer, BPCE refers to slump-retaining polycarboxylate superplasticizer, STPP refers to sodium tripolyphosphate, and SG refers to sodium gluconate.

[0045] Preparation process of 240h ultra-slow-setting waste-based dry-mixed wet spraying material: weigh PO 42.5R silicate cement, pre-screened soil and stone waste, and fly ash according to the mix ratio, pour them into a forced single-horizontal shaft concrete mixer and stir for 2 minutes until they are fully mixed, then add the compound retarder while stirring, and stir for another 2 minutes, and finally put it into a woven bag and seal it. At this point, a 240h ultra-slow-setting waste-based dry-mixed wet spraying material for underground engineering is prepared. Among them, cement: pre-screened soil and stone waste: fly ash = 1:2.86:0.25.

[0046] In the test mix ratio described in Table 1, except for the retarding component of the compound retarder, the masses of the other components are constant. By changing the components of the retarder, single and compound admixtures are performed to observe the state of the 240h super-slow-setting waste-based dry-mixed wet spraying material stored for 240h under laboratory conditions. In Test 1, sodium tripolyphosphate and white sugar are compounded, in Test 2, sodium tripolyphosphate and sodium gluconate are compounded, in Test 3, sodium hexametaphosphate and sodium gluconate are compounded, in Test 4, sodium hexametaphosphate and white sugar are compounded, in Test 5, sodium hexametaphosphate is single-mixed, and in Test 6, white sugar is single-mixed. The total mass of the retarding component remains unchanged. By changing the type of retarder, a control test is carried out to obtain the uniaxial compressive strength of each group of test blocks. By comparing the state of each test group after 240h storage and its uniaxial compressive strength (taking the average value of the uniaxial compressive strength of a group of test blocks as the final result), the optimal group is obtained by combining the material cost and the experimental results of each group, and the optimal retarder formula is determined to prepare a 240h super-slow-setting waste-based dry-mixed wet spraying material.

[0047] Preparation of concrete: Unpack the ultra-slow setting waste base dry-mixed wet spraying material stored at room temperature for 240 hours, pour it into a forced single-horizontal shaft concrete mixer, add water and stir for 5 minutes. The water-cement ratio of the fresh concrete is 0.46. The order of adding defoamer, air entraining agent, early strength agent and accelerator is as follows: ① Add defoamer and stir for 1 to 2 minutes to dissolve the irregular or harmful bubbles generated by the addition of polycarboxylic acid water reducer and concrete itself; ② Add air entraining agent and stir for 1 to 2 minutes to introduce a certain amount of uniformly distributed, closed and stable tiny bubbles into the fresh concrete to improve the workability of the fresh concrete; ③ Add chloride early strength agent and stir for 30 seconds to promote cement hydration in the fresh concrete and the formation of the internal skeleton of the concrete, while improving the strength of the shotcrete; ④ Add the new generation of accelerator and stir for 15 seconds to ensure that the concrete test block can be demolded after 1 day.

[0048] Preparation process of uniaxial compression test block: After completing the above steps, pour the fresh concrete into a 100mm×100mm×100mm mold, demould it after 1 day, and cure it for 3 days under standard curing conditions of temperature of 20℃±2℃ and relative humidity of more than 90%, and then carry out cube uniaxial compression test.

[0049] The above process refers to GB 50086-2015 "Technical Specifications for Geotechnical Anchors and Shotcrete Support Engineering" and GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete".

[0050] The uniaxial compressive strength of the test blocks in each test group is shown in Table 2 below:

[0051] Table 2 3d uniaxial compressive strength

[0052]

[0053] Among the above 6 groups of tests, the mixed group test 1, test 2, test 3, and test 4 were in good condition after 240 hours of storage, with no cement hydration phenomenon and greatly reduced dust pollution; the single-mixed group test 5 became dry after 240 hours of storage, the cement particles showed signs of agglomeration, and the workability of the freshly mixed concrete was extremely poor; the freshly mixed concrete of the single-mixed group test 6 had serious segregation and did not coagulate for a long time. Figure 1 and Figure 2 .

[0054] From the perspective of the workability of fresh concrete, the workability of the four groups of fresh concrete in Test 1, Test 2, Test 3, and Test 4 is good, while the workability of the two groups of fresh concrete in Test 5 and Test 6 is extremely poor. It is difficult to ensure the strength and rebound rate of shotcrete when used in underground construction; and the test of group 6 is difficult to demold within 24 hours, and the 3d strength is extremely low. The uniaxial compressive strength of Tests 1 to 6 is shown in Table 2. In terms of the comprehensive cubic uniaxial compressive strength and cost, Test 4 with sodium hexametaphosphate and white sugar is the best group.

[0055] The test results show that under the same dosage, the uniaxial compressive strength of concrete using sodium hexametaphosphate + white sugar is better than the other five groups. Among them, white sugar is a disaccharide, which has a strong retarding effect at a low dosage. Its retarding effect is equivalent to that of glucose and better than that of sodium gluconate. From the cost calculation, the market price of sodium hexametaphosphate is 10,000 yuan / ton, industrial white sugar is 4,000 yuan / ton, sodium tripolyphosphate is 10,300 yuan / ton, and sodium gluconate is 4,800 yuan / ton. The combination of sodium hexametaphosphate + white sugar obviously has a lower cost price, which can reduce the cost by 1,100 yuan per ton. The test results in Table 2 show that among the test groups, the uniaxial compressive strength of the test block of test 4 is higher, so the combination of sodium hexametaphosphate + white sugar is more advantageous.

[0056] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a 240h ultra-slow-setting dry-mix wet-spraying material for underground engineering, characterized in that The following steps are involved: Weigh PO 42.5 R silicate cement, pre-screened soil and stone waste, and fly ash according to the mix ratio, pour them into a forced single-horizontal shaft concrete mixer and stir for 2 minutes until they are fully mixed, then add the compound retarder while stirring, and stir for another 2 minutes, finally put it into a woven bag and seal it to obtain a 240h super-slow-setting waste-based dry-mixed wet spraying material for underground engineering; The mass ratio of the PO 42.5 R silicate cement: pre-screened soil and stone waste: fly ash is 1:2.86:0.25; The compound retarder is composed of white sugar, sodium hexametaphosphate, collapse-retaining polycarboxylate water-reducing agent and high water-reducing polycarboxylate water-reducing agent in a mass ratio of 1:5.81:1.63:14.

65.

2. The method for preparing the 240h ultra-slow setting dry-mix wet-spraying material for underground engineering according to claim 1, characterized in that: The preparation method of the compound retarder is as follows: at standard room temperature, white powdery sodium hexametaphosphate and white crystalline sugar are weighed according to a matching ratio and poured into a glass beaker filled with deionized water, and stirred in a clockwise direction with a glass rod until no precipitation occurs, and then a collapse-retaining polycarboxylate water-reducing agent and a high-water-reducing polycarboxylate water-reducing agent are added, and stirred evenly until the mixture becomes colorless and transparent, thereby obtaining the compound retarder.

3. The method for preparing the 240h ultra-slow setting dry-mix wet spraying material for underground engineering according to claim 1, characterized in that: The collapse-retaining polycarboxylate water-reducing agent is prepared by diluting the collapse-retaining polycarboxylate water-reducing mother liquor and deionized water in a mass ratio of 1:(4-5); the high-water-reducing polycarboxylate water-reducing agent is prepared by diluting the high-water-reducing polycarboxylate water-reducing mother liquor and deionized water in a mass ratio of 1:(4-5).

4. A shotcrete made of 240h ultra-slow-setting dry-mixed wet-spraying material for underground engineering prepared by the preparation method according to claim 1.

Images