Concrete material based on mixed granular coal gangue and preparation method thereof

Abstract

The invention provides a concrete material based on mixed granular coal gangue and a preparation method thereof, and belongs to the technical field of concrete.The preparation method comprises the following steps that S1, activated coal gangue powder is prepared; s2, preparing a composite colloid; s3, mixing and stirring the composite colloid and water to obtain mixed water; adding Portland cement, the activated coal gangue powder, limestone powder, gypsum and the pretreated fine aggregate into a stirrer for dry mixing, adding mixing water for stirring, then adding a polycarboxylic acid water reducer solution for stirring, and finally adding the pretreated coarse aggregate for stirring to obtain the concrete material based on the mixed particle coal gangue. According to the invention, the purposes of fast improvement of early strength, high later strength and strong impermeability of the concrete can be achieved.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to a concrete material based on mixed granular coal gangue and its preparation method. Background Technology

[0002] Traditionally, the application of coal gangue in concrete has been limited to its use as a low-grade aggregate or low-volume admixture after simple crushing. However, due to the low activity of unactivated coal gangue and its weak interfacial bond with cement paste when used as aggregate, the mechanical properties and durability of concrete are often poor, thus limiting its application. High-performance concrete not only requires high mechanical strength but also excellent durability (such as impermeability and erosion resistance) and good workability.

[0003] Patent application CN110002825A discloses a method for preparing coal gangue concrete, comprising the following steps: taking coal gangue, crushing it, and sieving it to obtain coal gangue powder, fine coal gangue particles, and coarse coal gangue particles; ball milling the coal gangue powder to obtain coal gangue micro powder; crushing the fine coal gangue particles again to obtain fine coal gangue aggregate; crushing the coarse coal gangue particles again to obtain coarse coal gangue aggregate; taking the fine coal gangue powder, fine coal gangue aggregate, coarse coal gangue aggregate, water, ordinary silicate cement, alkali activator, and water-reducing agent, and mixing them to obtain coal gangue concrete. The coal gangue concrete prepared in this application only makes simple use of coal gangue without improving the performance of the concrete material. The strength and impermeability of the prepared coal gangue concrete cannot meet the construction requirements.

[0004] Therefore, there is a need to provide a concrete material based on mixed granular coal gangue and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0005] In view of this, the present invention provides a concrete material based on mixed granular coal gangue and its preparation method, which can achieve the purpose of rapid early strength improvement, high later strength and strong impermeability of concrete.

[0006] To achieve the above objectives, the present invention provides a method for preparing concrete material based on mixed granular coal gangue, comprising the following steps: Step S1: Mix lightly calcined coal gangue powder, calcium hydroxide and triethanolamine, and ball mill to obtain activated coal gangue powder; Step S2: Add Ca(NO3)2·4H2O and LiNO3 to deionized water to dissolve, obtaining solution A; add Na2SiO3·9H2O and H3BO3 to deionized water to dissolve, obtaining solution B; add solution A to solution B and stir, adjust the pH to 10.8-11.2, let stand for aging, wash and purify, to obtain the composite colloid; Step S3: Mix the composite colloid with water to obtain mixing water; add silicate cement, activated coal gangue powder, limestone powder, gypsum and pretreated fine aggregate to the mixer and dry mix; add mixing water and mix; then add polycarboxylate superplasticizer solution and mix; finally add pretreated coarse aggregate and mix to obtain concrete material based on mixed granular coal gangue.

[0007] Activated coal gangue powder is obtained by reacting calcium hydroxide with lightly calcined coal gangue powder. When used as an admixture in concrete, it can reduce the amount of cement used. At the same time, it fills the capillaries through pozzolanic reaction, reduces porosity, improves impermeability and resistance to chemical erosion, and can also enhance the later strength of concrete.

[0008] Directly adding lithium and boron salts to the concrete mixing system makes it difficult to achieve uniform distribution within the concrete. Lithium ions preferentially contact the initial hydration products and undergo localized, intense reactions, leading to significant differences in hydration rates in some areas, resulting in false setting. This, in turn, causes uneven stress development and an increase in microcracks. Simultaneously, B(OH)4... - It easily competes with the surface of newly formed cement clinker for calcium ion adsorption sites, resulting in a strong retarding effect and disrupting hydration. In addition, the introduction of additional soluble salts increases the ion concentration of the pore fluid, causing uneven dispersion of the water-reducing agent, leading to increased loss of concrete paste fluidity, reduced concrete structural strength, and increased construction difficulty.

[0009] By preparing a composite colloid, B and Li were pre-assembled uniformly into the nanostructure of CSH gel, thus obtaining "nucleation seeds" before concrete hydration. Adding the composite colloid to concrete can serve as readily available nucleation sites, guiding the Ca produced during cement particle hydration. 2+ and SiO4 - The orderly growth of lithium ions on its surface makes the setting-promoting effect of lithium ions mild and controllable, contributing to the rapid improvement of early-stage strength in concrete. Simultaneously, calcium ions (B) are no longer in a free state and do not compete with calcium ions for sites, thus avoiding retardation and increasing the stability of CSH gel. This reduces concrete porosity, optimizes the pore structure, and enhances the concrete's impermeability and durability. Furthermore, the lubricating effect of the composite colloid helps reduce friction, resulting in lower slump loss and improved construction quality.

[0010] Limestone powder has fine particles that can fill the gaps between cement particles, forming a denser structure. This helps to enhance the early strength of concrete and reduces porosity, decreasing the penetration of corrosive molecules such as moisture and chloride ions, thus improving the durability of concrete. In addition, limestone powder can react with the aluminum phase in cement to form hydrated calcium aluminum carbonate, which can stabilize early hydration, consume C3A, and prevent C3A from reacting directly and rapidly with water. The resulting hydrated calcium aluminum carbonate and CSH gel together form a skeleton, improving the mechanical properties of concrete.

[0011] Gypsum can also control the hydration of C3A and prevent flash setting. The dissolution of gypsum provides sulfate ions that react with C3A to form a dense protective film of ettringite (AFt) on the surface of C3A particles. When the gypsum is completely consumed, the ettringite (AFt) will react with the unhydrated C3A to form monosulfate calcium aluminosulfate (AFm). Through this process, gypsum can slow down the hydration reaction of C3A and avoid insufficient early strength of concrete.

[0012] Preferably, in step S1, the preparation of lightly calcined coal gangue powder includes the following steps: Coal gangue powder, crushed to 3-5mm, is evenly spread into a refractory tray, pushed into a muffle furnace, heated, held at that temperature, and then cooled to obtain lightly calcined coal gangue powder.

[0013] By preparing lightly calcined coal gangue powder, releasing structural water, and disrupting its layered ordered structure, an amorphous aluminum-silicon phase with high pozzolanic activity is obtained, thereby enhancing the reactivity of coal gangue.

[0014] Preferably, the heating rate is 8-12℃ / min, the temperature is 700-800℃, and the holding time is 1-2h.

[0015] Preferably, the ball milling speed is 300-450 rpm and the time is 60-90 min.

[0016] Ball milling can increase the specific surface area of ​​coal gangue powder and promote an increase in reaction rate.

[0017] Preferably, in step S2, the stirring speed is 600-800 rpm; the rate at which solution A is added to solution B is 1-1.5 mL / min.

[0018] Preferably, the mixing speed in step S3 is 300-500 rpm, and the time is 1-2 min.

[0019] Preferably, the preparation of the pretreated coarse aggregate includes the following steps: mixing CaCl2·2H2O with water to obtain solution C, and mixing (NH4)2HPO4 with water to obtain solution D; immersing the coarse coal gangue aggregate in solution C, draining it, transferring it to solution D for immersion, and draining it to obtain the pretreated coarse aggregate; The preparation of the pretreated fine aggregate includes the following steps: immersing fine coal gangue aggregate in solution C, draining, transferring it to solution D for immersion, and draining again to obtain the pretreated fine aggregate.

[0020] Adding calcium phosphate directly to the concrete system during mixing introduces phosphate ions, which retardes the concrete's setting and leads to insufficient early strength. This solution uses a pretreatment method to avoid retarding while still improving interfacial strength.

[0021] Under acidic conditions, the Ca in CaCl2 2+ HPO4 in (NH4)2HPO4 2- A precipitation reaction occurs on the surface of the aggregate to form a calcium phosphate dihydrate coating. When the aggregate is added to the concrete system, if the ambient pH is greater than 12, the calcium phosphate dihydrate can be converted into hydroxyapatite in situ. It can nucleate and intercalate with the concrete hydration products to form a continuous interface layer with mineral bridging and chemical bonding. This improves the bond between the aggregate and the cement paste, enhances the mechanical properties, and helps to improve the strength of the aggregate-cement interface transition zone.

[0022] Preferably, the coarse coal gangue aggregate has a particle size of 5-20 mm, and the fine coal gangue aggregate has a particle size of 0.15-5 mm.

[0023] Preferably, in step S3, the concentration of the polycarboxylate superplasticizer solution is 30-50 wt%.

[0024] Polycarboxylate superplasticizers can be adsorbed onto the surface of cement particles, generating electrostatic repulsion and steric hindrance, improving the fluidity of concrete paste, allowing for a lower water-cement ratio, and increasing concrete strength.

[0025] To achieve the above objectives, the present invention also provides a concrete material based on mixed granular coal gangue prepared by the above-described method for preparing a concrete material based on mixed granular coal gangue, comprising the following components in parts by weight: The composition includes 28-56 parts silicate cement, 11-22 parts activated coal gangue powder, 2-4 parts limestone powder, 1-2 parts gypsum, 14.5-29 parts water, 0.9-1.8 parts composite colloid, 0.24-0.72 parts polycarboxylate superplasticizer solution, 100-200 parts pretreated coarse aggregate, and 67-134 parts pretreated fine aggregate.

[0026] The concrete material based on mixed granular coal gangue prepared using the above-mentioned proportions of components can achieve the goals of improving early-stage strength, high later-stage strength, and strong impermeability.

[0027] The above-described technical solution of the present invention has at least the following beneficial effects: 1. By preparing a composite colloid, B and Li are pre-assembled uniformly into the nanostructure of CSH gel as ready-made nucleation sites to guide the Ca generated during the hydration of cement particles. 2+ and SiO4 - The orderly growth of lithium ions on its surface makes the setting-promoting effect of lithium ions mild and controllable, which helps to rapidly improve the early strength of concrete, avoids the side effects of directly adding lithium salts and boron salts, and also helps to optimize the pore structure of concrete and improve its impermeability.

[0028] 2. Limestone powder acts as a filler through physical and chemical processes, and can also react with the aluminum phase in cement to generate hydrated calcium aluminum carbonate, consuming C3A and preventing C3A from reacting directly and rapidly with water, thus avoiding insufficient early strength caused by flash setting. Gypsum provides sulfate ions to react with C3A to generate ettringite (AFt), which will then react with unhydrated C3A to convert into monosulfate calcium sulfoaluminate (AFm), thereby controlling the hydration of C3A and further ensuring the early strength of concrete. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0030] The silicate cement used in the following examples and comparative examples is ordinary silicate cement PO 42.5R type; the polycarboxylate superplasticizer is SPF-300 polycarboxylate high-performance superplasticizer, purchased from Liaoning Kelong Fine Chemical Co., Ltd.

[0031] Example 1 Coal gangue powder, crushed to 3-5 mm, is evenly spread in a refractory tray and fed into a muffle furnace. The temperature is increased to 750°C at a rate of 10°C / min, held for 1.5 h, and then cooled to obtain lightly calcined coal gangue powder. 15 kg of lightly calcined coal gangue powder, 0.3 kg of calcium hydroxide, and 10 g of triethanolamine are mixed and ball-milled at 300 rpm for 90 min. The discharged material is sieved and then re-milled to obtain coarse particles until D50 = 3-7 µm, thus obtaining activated coal gangue powder.

[0032] Coarse coal gangue aggregate with a particle size of 5-20 mm and fine coal gangue aggregate with a particle size of 0.15-5 mm are washed and dried. 2.2 kg of CaCl2·2H2O is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution C. 1.19 kg of (NH4)2HPO4 is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution D. The coarse coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated coarse aggregate. The fine coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated fine aggregate.

[0033] Add 3 kg of deionized water to one container, dissolve 0.9 kg of Ca(NO3)2·4H2O and 0.02 kg of LiNO3, and add water to bring the volume to 4.0 kg. Adjust the pH to 6-7 to obtain solution A. Add 3.6 kg of deionized water to another container, dissolve 0.8 kg of Na2SiO3·9H2O and 0.04 kg of H3BO3, and add water to bring the volume to 4.5 kg. Adjust the pH to 10.5-11.5 to obtain solution B. Place both containers in a 30°C water bath, start the stirrer, and stir at 700 rpm. Simultaneously, add solution A to solution B at a rate of 1.25 mL / min, and finely adjust the pH with a small amount of NaOH during the process to maintain the system pH at 10.8-11.2. After mixing, continue stirring for 30 min, let stand for 3 h, centrifuge, remove the supernatant, resuspend in deionized water, and repeat 3 times until the solid content is 20 wt%, to obtain the composite colloid.

[0034] Take 28 kg of silicate cement, 11 kg of activated coal gangue powder, 2 kg of limestone powder, 1 kg of gypsum, 14.5 kg of water, 0.9 kg of composite colloid, 0.24 kg of polycarboxylate superplasticizer solution (concentration of 50 wt%), 100 kg of pretreated coarse aggregate, and 67 kg of pretreated fine aggregate. Add the composite colloid to the water and stir at 400 rpm for 1.5 min to obtain mixing water. Add silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregate to the mixer and dry mix for 30 s. Then add the mixing water and stir for 60 s. After that, add the polycarboxylate superplasticizer solution in two equal portions and stir for 90 s each time. Finally, add the pretreated coarse aggregate and stir for 60 s to obtain concrete material based on mixed granular coal gangue.

[0035] Example 2 Coal gangue powder, crushed to 3-5 mm, is evenly spread in a refractory tray and fed into a muffle furnace. The temperature is increased to 800°C at a rate of 8°C / min, held for 1 hour, and then cooled to obtain lightly calcined coal gangue powder. 15 kg of lightly calcined coal gangue powder, 0.45 kg of calcium hydroxide, and 15 g of triethanolamine are mixed and ball-milled at 350 rpm for 80 minutes. The discharged material is sieved and then re-milled to obtain coarse particles until D50 = 3-7 µm, thus obtaining activated coal gangue powder.

[0036] Coarse coal gangue aggregate with a particle size of 5-20 mm and fine coal gangue aggregate with a particle size of 0.15-5 mm are washed and dried. 2.2 kg of CaCl2·2H2O is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution C. 1.19 kg of (NH4)2HPO4 is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution D. The coarse coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated coarse aggregate. The fine coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated fine aggregate.

[0037] Add 3.2 kg of deionized water to one container, dissolve 0.9 kg of Ca(NO3)2·4H2O and 0.03 kg of LiNO3, and add water to bring the volume to 4.0 kg. Adjust the pH to 6-7 to obtain solution A. Add 3.8 kg of deionized water to another container, dissolve 0.8 kg of Na2SiO3·9H2O and 0.06 kg of H3BO3, and add water to bring the volume to 4.5 kg. Adjust the pH to 10.5-11.5 to obtain solution B. Place both containers in a 25°C water bath, start the stirrer, and stir at 600 rpm. Simultaneously, add solution A to solution B at a rate of 1.0 mL / min, and finely adjust the pH with a small amount of NaOH during the process to maintain the system pH at 10.8-11.2. After mixing, continue stirring for 30 min, let stand for 4 h, centrifuge, remove the supernatant, resuspend in deionized water, and repeat 3 times until the solid content is 22 wt%, to obtain the composite colloid.

[0038] Take 56 kg of silicate cement, 22 kg of activated coal gangue powder, 4 kg of limestone powder, 2 kg of gypsum, 29 kg of water, 1.8 kg of composite colloid, 0.72 kg of polycarboxylate superplasticizer solution (concentration of 30 wt%), 200 kg of pretreated coarse aggregate, and 134 kg of pretreated fine aggregate. Add the composite colloid to the water and stir at 300 rpm for 2 minutes to obtain mixing water. Add silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregate to the mixer and dry mix for 30 seconds. Then add the mixing water and stir for 60 seconds. After that, add the polycarboxylate superplasticizer solution in two equal portions and stir for 90 seconds each. Finally, add the pretreated coarse aggregate and stir for 60 seconds to obtain concrete material based on mixed granular coal gangue.

[0039] Example 3 Coal gangue powder, crushed to 3-5 mm, is evenly spread in a refractory tray and fed into a muffle furnace. The temperature is increased to 700°C at a rate of 12°C / min, held for 2 hours, and then cooled to obtain lightly calcined coal gangue powder. 15 kg of lightly calcined coal gangue powder, 0.15 kg of calcium hydroxide, and 7.5 g of triethanolamine are mixed and ball-milled at 450 rpm for 60 minutes. The discharged material is sieved and then re-milled to obtain coarse particles until D50 = 3-7 µm, thus obtaining activated coal gangue powder.

[0040] Coarse coal gangue aggregate with a particle size of 5-20 mm and fine coal gangue aggregate with a particle size of 0.15-5 mm are washed and dried. 2.2 kg of CaCl2·2H2O is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution C. 1.19 kg of (NH4)2HPO4 is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution D. The coarse coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated coarse aggregate. The fine coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated fine aggregate.

[0041] Add 2.8 kg of deionized water to one container, dissolve 0.9 kg of Ca(NO3)2·4H2O and 0.015 kg of LiNO3, and add water to bring the volume to 4.0 kg. Adjust the pH to 6-7 to obtain solution A. Add 3.5 kg of deionized water to another container, dissolve 0.8 kg of Na2SiO3·9H2O and 0.03 kg of H3BO3, and add water to bring the volume to 4.5 kg. Adjust the pH to 10.5-11.5 to obtain solution B. Place both containers in a 25-35℃ water bath, start the stirrer, and stir at 800 rpm. Simultaneously, add solution A to solution B at a rate of 1.5 mL / min, and finely adjust the pH with a small amount of NaOH during the process to maintain the system pH at 10.8-11.2. After mixing, continue stirring for 30 min, let stand for 2 h to age, centrifuge, remove the supernatant, resuspend in deionized water, and repeat 3 times until the solid content is 18 wt% to obtain the composite colloid.

[0042] Take 42 kg of silicate cement, 16.5 kg of activated coal gangue powder, 3 kg of limestone powder, 1.5 kg of gypsum, 21.75 kg of water, 1.35 kg of composite colloid, 0.45 kg of polycarboxylate superplasticizer solution (concentration of 40 wt%), 150 kg of pretreated coarse aggregate, and 100 kg of pretreated fine aggregate. Add the composite colloid to the water and stir at 500 rpm for 1 min to obtain mixing water. Add silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregate to the mixer and dry mix for 30 s. Then add the mixing water and stir for 60 s. After that, add the polycarboxylate superplasticizer solution in two equal portions and stir for 90 s each time. Finally, add the pretreated coarse aggregate and stir for 60 s to obtain concrete material based on mixed granular coal gangue.

[0043] Example 4 Coal gangue powder, crushed to 3-5 mm, is evenly spread in a refractory tray and fed into a muffle furnace. The temperature is increased to 750°C at a rate of 8°C / min, held for 1.5 h, and then cooled to obtain lightly calcined coal gangue powder. 15 kg of lightly calcined coal gangue powder, 0.25 kg of calcium hydroxide, and 12 g of triethanolamine are mixed and ball-milled at 400 rpm for 70 min. The discharged material is sieved and then re-milled to obtain coarse particles until D50 = 3-7 µm, thus obtaining activated coal gangue powder.

[0044] Coarse coal gangue aggregate with a particle size of 5-20 mm and fine coal gangue aggregate with a particle size of 0.15-5 mm are washed and dried. 2.2 kg of CaCl2·2H2O is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution C. 1.19 kg of (NH4)2HPO4 is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution D. The coarse coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated coarse aggregate. The fine coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated fine aggregate.

[0045] Add 3.2 kg of deionized water to one container, dissolve 0.9 kg of Ca(NO3)2·4H2O and 0.03 kg of LiNO3, and add water to bring the volume to 4.0 kg. Adjust the pH to 6-7 to obtain solution A. Add 3.5 kg of deionized water to another container, dissolve 0.8 kg of Na2SiO3·9H2O and 0.03 kg of H3BO3, and add water to bring the volume to 4.5 kg. Adjust the pH to 10.5-11.5 to obtain solution B. Place both containers in a 30°C water bath, start the stirrer, and stir at 750 rpm. Simultaneously, add solution A to solution B at a rate of 1.3 mL / min, and finely adjust the pH with a small amount of NaOH during the process to maintain the system pH at 10.8-11.2. After mixing, continue stirring for 30 min, let stand for 2.5 h, centrifuge, remove the supernatant, resuspend in deionized water, and repeat 3 times until the solid content is 22 wt%, to obtain the composite colloid.

[0046] Take 28 kg of silicate cement, 11 kg of activated coal gangue powder, 2 kg of limestone powder, 1 kg of gypsum, 14.5 kg of water, 0.9 kg of composite colloid, 0.24 kg of polycarboxylate superplasticizer solution (concentration of 50 wt%), 100 kg of pretreated coarse aggregate, and 67 kg of pretreated fine aggregate. Add the composite colloid to the water and stir at 400 rpm for 1.5 min to obtain mixing water. Add silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregate to the mixer and dry mix for 30 s. Then add the mixing water and stir for 60 s. After that, add the polycarboxylate superplasticizer solution in two equal portions and stir for 90 s each time. Finally, add the pretreated coarse aggregate and stir for 60 s to obtain concrete material based on mixed granular coal gangue.

[0047] Example 5 Coal gangue powder, crushed to 3-5 mm, is evenly spread in a refractory tray and fed into a muffle furnace. The temperature is increased to 700°C at a rate of 9°C / min, held for 2 hours, and then cooled to obtain lightly calcined coal gangue powder. 15 kg of lightly calcined coal gangue powder, 0.45 kg of calcium hydroxide, and 15 g of triethanolamine are mixed and ball-milled at 350 rpm for 75 minutes. The discharged material is sieved and then re-milled to obtain coarse particles until D50 = 3-7 µm, thus obtaining activated coal gangue powder.

[0048] Coarse coal gangue aggregate with a particle size of 5-20 mm and fine coal gangue aggregate with a particle size of 0.15-5 mm are washed and dried. 2.2 kg of CaCl2·2H2O is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution C. 1.19 kg of (NH4)2HPO4 is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution D. The coarse coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated coarse aggregate. The fine coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated fine aggregate.

[0049] Add 3 kg of deionized water to one container, dissolve 0.9 kg of Ca(NO3)2·4H2O and 0.025 kg of LiNO3, and add water to bring the volume to 4.0 kg. Adjust the pH to 6-7 to obtain solution A. Add 3.8 kg of deionized water to another container, dissolve 0.8 kg of Na2SiO3·9H2O and 0.05 kg of H3BO3, and add water to bring the volume to 4.5 kg. Adjust the pH to 10.5-11.5 to obtain solution B. Place both containers in a 35°C water bath, start the stirrer, and stir at 650 rpm. Simultaneously, add solution A to solution B at a rate of 1.5 mL / min, and finely adjust the pH with a small amount of NaOH during the process to maintain the system pH at 10.8-11.2. After mixing, continue stirring for 30 min, let stand for 3.5 h, centrifuge, remove the supernatant, resuspend in deionized water, and repeat 3 times until the solid content is 18 wt% to obtain the composite colloid.

[0050] Take 42 kg of silicate cement, 16.5 kg of activated coal gangue powder, 3 kg of limestone powder, 1.5 kg of gypsum, 21.75 kg of water, 1.35 kg of composite colloid, 0.45 kg of polycarboxylate superplasticizer solution (concentration of 40 wt%), 150 kg of pretreated coarse aggregate, and 100 kg of pretreated fine aggregate. Add the composite colloid to the water and stir at 500 rpm for 1 min to obtain mixing water. Add silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregate to the mixer and dry mix for 30 s. Then add the mixing water and stir for 60 s. After that, add the polycarboxylate superplasticizer solution in two equal portions and stir for 90 s each time. Finally, add the pretreated coarse aggregate and stir for 60 s to obtain concrete material based on mixed granular coal gangue.

[0051] Example 6 Coal gangue powder, crushed to 3-5 mm, is evenly spread in a refractory tray and fed into a muffle furnace. The temperature is increased to 800 °C at a rate of 11 °C / min, held for 1 hour, and then cooled to obtain lightly calcined coal gangue powder. 15 kg of lightly calcined coal gangue powder, 0.15 kg of calcium hydroxide, and 7.5 g of triethanolamine are mixed and ball-milled at 450 rpm for 60 minutes. The discharged material is sieved and then re-milled to obtain coarse particles until D50 = 3-7 µm, thus obtaining activated coal gangue powder.

[0052] Coarse coal gangue aggregate with a particle size of 5-20 mm and fine coal gangue aggregate with a particle size of 0.15-5 mm are washed and dried. 2.2 kg of CaCl2·2H2O is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution C. 1.19 kg of (NH4)2HPO4 is dissolved in water and the volume is adjusted to 100 L, and the pH is adjusted to 4.2 to obtain solution D. The coarse coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated coarse aggregate. The fine coal gangue aggregate is immersed in solution C and slowly stirred for 5-10 min, drained, and then immersed in solution D and slowly stirred for 10-20 min to obtain pretreated fine aggregate.

[0053] Add 2.8 kg of deionized water to one container, dissolve 0.9 kg of Ca(NO3)2·4H2O and 0.015 kg of LiNO3, and add water to bring the volume to 4.0 kg. Adjust the pH to 6-7 to obtain solution A. Add 3.8 kg of deionized water to another container, dissolve 0.8 kg of Na2SiO3·9H2O and 0.06 kg of H3BO3, and add water to bring the volume to 4.5 kg. Adjust the pH to 10.5-11.5 to obtain solution B. Place both containers in a 25°C water bath, start the stirrer, and stir at 700 rpm. Simultaneously, add solution A to solution B at a rate of 1.2 mL / min, and finely adjust the pH with a small amount of NaOH during the process to maintain the system pH at 10.8-11.2. After mixing, continue stirring for 30 min, let stand for 3 h to age, centrifuge, remove the supernatant, resuspend in deionized water, and repeat 3 times until the solid content is 20 wt%, to obtain the composite colloid.

[0054] Take 56 kg of silicate cement, 22 kg of activated coal gangue powder, 4 kg of limestone powder, 2 kg of gypsum, 29 kg of water, 1.8 kg of composite colloid, 0.72 kg of polycarboxylate superplasticizer solution (concentration of 30 wt%), 200 kg of pretreated coarse aggregate, and 134 kg of pretreated fine aggregate. Add the composite colloid to the water and stir at 300 rpm for 2 minutes to obtain mixing water. Add silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregate to the mixer and dry mix for 30 seconds. Then add the mixing water and stir for 60 seconds. After that, add the polycarboxylate superplasticizer solution in two equal portions and stir for 90 seconds each. Finally, add the pretreated coarse aggregate and stir for 60 seconds to obtain concrete material based on mixed granular coal gangue.

[0055] The present invention also includes comparative examples and related experiments.

[0056] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no composite colloid was prepared in Comparative Example 1, but silicate cement was used instead. The other components and preparation methods were the same as in Example 1, and a concrete material based on mixed granular coal gangue was prepared.

[0057] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 did not use activated coal gangue powder, but instead used ordinary coal gangue powder. The other components and preparation methods were the same as in Example 1, and a concrete material based on mixed granular coal gangue was prepared.

[0058] Performance testing The concrete materials based on mixed granular coal gangue prepared in Examples 1-6 and Comparative Examples 1-2 were prepared into cubic specimens of 150mm×150mm×150mm. The early strength and late strength of the specimens were tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The compressive strength at 1 day, 3 days and 28 days was tested. The concrete materials based on mixed granular coal gangue prepared in Examples 1-6 and Comparative Examples 1-2 were used to prepare frustum specimens with a top diameter of 175 mm, a bottom diameter of 185 mm, and a height of 150 mm. After curing for 28 days, according to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", a stepwise pressurization method was adopted, starting from 0.1 MPa and increasing the water pressure by 0.1 MPa every 8 hours until 3 out of 6 specimens were permeable. The impermeability grade = maximum pressure value × 10 - 1; According to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the slump values ​​of concrete materials based on mixed granular coal gangue prepared in Examples 1-6 and Comparative Examples 1-2 were tested. In summary, the test results are shown in Table 1.

[0059] Table 1

[0060] As shown in Table 1, compared with Example 1, the 1-day and 3-day compressive strengths of the concrete material based on mixed granular coal gangue prepared in Comparative Example 1 are significantly different, the early strength improvement is slow, and the impermeability is reduced. This indicates that the composite colloid helps to rapidly improve the early strength of concrete and can also optimize the pore structure of concrete to improve impermeability. The 28-day compressive strength of the concrete material based on mixed granular coal gangue prepared in Comparative Example 2 is lower than that of the concrete material based on mixed granular coal gangue prepared in Example 1, and its impermeability grade is the lowest. This indicates that using activated coal gangue powder as an admixture can reduce the porosity of concrete through pozzolanic reaction, thereby improving the later strength and impermeability.

[0061] The slump of the concrete material based on mixed granular coal gangue prepared in Comparative Example 1 was significantly lower than that in Examples 1-6, indicating that the addition of composite colloid can reduce the slump loss of concrete and improve the construction quality.

[0062] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing concrete material based on mixed granular coal gangue, characterized in that, Includes the following steps: Step S1: Mix lightly calcined coal gangue powder, calcium hydroxide and triethanolamine, and ball mill to obtain activated coal gangue powder; Step S2: Add Ca(NO3)2·4H2O and LiNO3 to deionized water to dissolve, obtaining solution A; add Na2SiO3·9H2O and H3BO3 to deionized water to dissolve, obtaining solution B; add solution A to solution B and stir, adjust the pH to 10.8-11.2, let stand for aging, wash and purify, to obtain the composite colloid; Step S3: Mix the composite colloid with water to obtain mixing water; add silicate cement, activated coal gangue powder, limestone powder, gypsum and pretreated fine aggregate to the mixer and dry mix; add mixing water and mix; then add polycarboxylate superplasticizer solution and mix; finally add pretreated coarse aggregate and mix to obtain concrete material based on mixed granular coal gangue.

2. The method for preparing concrete material based on mixed granular coal gangue according to claim 1, characterized in that, In step S1, the preparation of lightly calcined coal gangue powder includes the following steps: Coal gangue powder, crushed to 3-5mm, is evenly spread into a refractory tray, pushed into a muffle furnace, heated, held at that temperature, and then cooled to obtain lightly calcined coal gangue powder.

3. The method for preparing concrete material based on mixed granular coal gangue according to claim 2, characterized in that, The heating rate is 8-12℃ / min, the temperature is 700-800℃, and the holding time is 1-2h.

4. The method for preparing concrete material based on mixed granular coal gangue according to claim 1, characterized in that, In step S1, the ball milling speed is 300-450 rpm and the time is 60-90 min.

5. The method for preparing concrete material based on mixed granular coal gangue according to claim 1, characterized in that, In step S2, the stirring speed is 600-800 rpm; the rate at which solution A is added to solution B is 1-1.5 mL / min.

6. The method for preparing concrete material based on mixed granular coal gangue according to claim 1, characterized in that, In step S3, the mixing speed is 300-500 rpm and the time is 1-2 min.

7. The method for preparing concrete material based on mixed granular coal gangue according to claim 1, characterized in that, The preparation of the pretreated coarse aggregate includes the following steps: CaCl2·2H2O was mixed with water to obtain solution C, and (NH4)2HPO4 was mixed with water to obtain solution D. Coarse coal gangue aggregate was immersed in solution C, drained, transferred to solution D for immersion, and drained to obtain pretreated coarse aggregate. The preparation of the pretreated fine aggregate includes the following steps: immersing fine coal gangue aggregate in solution C, draining, transferring it to solution D for immersion, and draining again to obtain the pretreated fine aggregate.

8. The method for preparing concrete material based on mixed granular coal gangue according to claim 7, characterized in that, The coarse coal gangue aggregate has a particle size of 5-20 mm, and the fine coal gangue aggregate has a particle size of 0.15-5 mm.

9. The method for preparing concrete material based on mixed granular coal gangue according to claim 1, characterized in that, In step S3, the concentration of the polycarboxylate superplasticizer solution is 30-50 wt%.

10. A concrete material based on mixed granular coal gangue, prepared by the method for preparing a concrete material based on mixed granular coal gangue according to any one of claims 1-9, characterized in that, The components include the following parts by weight: The composition includes 28-56 parts silicate cement, 11-22 parts activated coal gangue powder, 2-4 parts limestone powder, 1-2 parts gypsum, 14.5-29 parts water, 0.9-1.8 parts composite colloid, 0.24-0.72 parts polycarboxylate superplasticizer solution, 100-200 parts pretreated coarse aggregate, and 67-134 parts pretreated fine aggregate.

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