A concrete material based on mixed granular coal gangue and a preparation method thereof

Abstract

The application provides a kind of concrete material based on mixed particle coal gangue and a preparation method thereof, and belongs to the technical field of concrete, comprising the following steps: step S1, preparing activated coal gangue powder;Step S2, preparing composite colloid;Step S3, mixing and stirring the composite colloid with water to obtain mixed water;Add Portland cement, activated coal gangue powder, limestone powder, gypsum and pretreated fine aggregate to the mixer and dry mix, add mixed water and stir, then add polycarboxylic acid water reducer solution and stir, finally add pretreated coarse aggregate and stir to obtain the concrete material based on mixed particle coal gangue.The application can achieve the purpose of improving the early strength of concrete, high late strength and strong impermeability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a concrete material based on mixed particle coal gangue and a preparation method thereof. BACKGROUND

[0002] Traditionally, the application of coal gangue in concrete is mostly limited to simple crushing as low-grade aggregate or low-dosage admixture. However, due to the low activity of coal gangue without activation treatment and the weak interface bonding between coal gangue and cement paste when used as aggregate, the mechanical properties and durability of concrete are often poor, which limits its application. High-performance concrete not only requires high mechanical strength, but also needs to have excellent durability (such as impermeability, corrosion resistance, etc.) and good construction workability.

[0003] The patent application file with publication number CN110002825A discloses a preparation method of coal gangue concrete, including the following steps: taking coal gangue, crushing and then screening to obtain coal gangue powder, coal gangue fine particles, and coal gangue coarse particles; ball-milling the coal gangue powder to obtain coal gangue micro-powder; crushing the coal gangue fine particles again to obtain coal gangue fine aggregate; crushing the coal gangue coarse particles again to obtain coal gangue coarse aggregate; taking the coal gangue micro-powder, the coal gangue fine aggregate, the coal gangue coarse aggregate, water, ordinary portland cement, alkali activator, and water reducing agent respectively, and mixing uniformly to obtain coal gangue concrete. The coal gangue concrete prepared in the application file only simply utilizes coal gangue, and the performance of the concrete material is not improved. The strength and impermeability of the coal gangue concrete prepared in the application file cannot meet the construction requirements.

[0004] Therefore, it is necessary to provide a concrete material based on mixed particle coal gangue and a preparation method thereof to solve the problems existing in the prior art. SUMMARY

[0005] Therefore, the present application provides a concrete material based on mixed particle coal gangue and a preparation method thereof, which can achieve the purposes of early strength improvement, high late strength, and strong impermeability.

[0006] To achieve the above-mentioned purposes, the present application provides a preparation method of a concrete material based on mixed particle coal gangue, including the following steps:

[0007] Step S1, mixing coal gangue light calcined powder, calcium hydroxide, and triethanolamine, and ball-milling to obtain activated coal gangue powder;

[0008] Step S2, Ca(NO3)2·4H2O and LiNO3 are added to deionized water for dissolution to obtain solution A; Na2SiO3·9H2O and H3BO3 are added to deionized water for dissolution to obtain solution B; solution A is added to solution B for stirring, and the pH is adjusted to 10.8-11.2, and then aging, cleaning and purification are performed to obtain a composite colloid;

[0009] Step S3, the composite colloid is mixed with water for stirring to obtain mixed water; Portland cement, activated coal gangue powder, limestone powder, gypsum and pretreated fine aggregate are dry-mixed in a mixer, mixed water is added for stirring, then polycarboxylic acid water reducer solution is added for stirring, and finally pretreated coarse aggregate is added for stirring to obtain a mixed particle coal gangue-based concrete material.

[0010] The activated coal gangue powder is obtained by reacting calcium hydroxide with coal gangue light calcined powder, which can be used as an admixture in concrete to reduce the amount of cement used, fill capillary pores through pozzolanic reaction, reduce porosity, improve impermeability and resistance to chemical attack, and also improve the late strength of concrete.

[0011] It is difficult to achieve uniform distribution in the concrete system by directly adding lithium salt and boron salt to the concrete mixing system. Lithium ions will preferentially contact the initial hydration products and undergo local intense reactions, resulting in large differences in hydration rate in some areas, causing false setting phenomena, and thus causing uneven stress development, resulting in an increase in microcracks. At the same time, B(OH)4 - can compete with calcium ion sites on the surface of newly formed cement clinker, causing strong retarding effect and disturbing hydration. In addition, the introduction of additional soluble salts increases the ion concentration of the pore solution, causing uneven dispersion of the water reducer, resulting in an increase in the loss of concrete paste fluidity, a decrease in concrete structural strength, and an increase in construction difficulty.

[0012] By preparing a composite colloid, B and Li are uniformly assembled into the nanostructure of C-S-H gel, and "nucleation seeds" are obtained before concrete hydration. The composite colloid added to the concrete can serve as a ready-made nucleation site to guide the ordered growth of Ca 2+ and SiO4 - on its surface, making the accelerating effect of lithium ions mild and controllable, which helps to rapidly improve the early strength of concrete. At the same time, B is no longer in a free state and does not compete with calcium ions for sites, which can avoid retarding and also increase the stability of C-S-H gel, thereby reducing the porosity of concrete, optimizing the pore structure, enhancing the impermeability of concrete, and improving the durability. In addition, the lubricating effect of the composite colloid helps to reduce friction, resulting in lower loss of concrete slump, thereby improving construction quality.

[0013] The limestone powder has a fine particle size, can fill the gap between the cement particles to play a filling role, form a more compact structure, help to strengthen the early strength of the concrete, and can reduce the porosity, reduce the infiltration of water and chloride ions and other erosion molecules, and improve the durability of the concrete; in addition, the limestone powder can also react with aluminum in the cement to generate hydrated calcium aluminum carbonate, which can stabilize the early hydration, consume C3A, avoid the direct and rapid reaction of C3A with water, and the generated hydrated calcium aluminum carbonate and C-S-H gel together constitute the skeleton to improve the mechanical properties of the concrete.

[0014] Gypsum can also control the hydration of C3A and prevent flash setting. The dissolution of gypsum will provide sulfate to react with C3A to generate a dense ettringite (AFt) protective film on the surface of C3A particles. When the gypsum is consumed, the ettringite (AFt) will be converted into monosulfate type calcium aluminate (AFm) with unhydrated C3A. Through this process, gypsum can play a role in making the C3A hydration reaction proceed smoothly and avoid the lack of early strength of the concrete.

[0015] Preferably, in the step S1, the preparation of the coal gangue light calcined powder comprises the following steps:

[0016] The crushed coal gangue powder of 3-5 mm is uniformly spread in the refractory tray, and then pushed into the muffle furnace for heating, holding and cooling to obtain the coal gangue light calcined powder.

[0017] By preparing the coal gangue light calcined powder, the structural water is released and the layered ordered structure is destroyed to obtain amorphous aluminum-silicon phase with high pozzolanic activity, so that the reactivity of the coal gangue is improved.

[0018] Preferably, the heating speed is 8-12℃ / min, the temperature is 700-800℃, and the holding time is 1-2h.

[0019] Preferably, the ball milling speed is 300-450rpm, and the time is 60-90min.

[0020] By ball milling, the specific surface area of the coal gangue powder can be increased to promote the reaction rate.

[0021] Preferably, in the step S2, the stirring speed is 600-800rpm; and the speed of adding the solution A to the solution B is 1-1.5mL / min.

[0022] Preferably, in the step S3, the mixing and stirring speed is 300-500rpm, and the time is 1-2min.

[0023] Preferably, the preparation of the pretreated coarse aggregate comprises the following steps: mixing CaCl2.2H2O with water to obtain solution C, mixing (NH4)2HPO4 with water to obtain solution D; dipping the coarse coal gangue aggregate into solution C, draining, and then dipping into solution D, draining, to obtain the pretreated coarse aggregate.

[0024] The preparation of the pretreated fine aggregate comprises the following steps: dipping the fine coal gangue aggregate into solution C, draining, and then dipping into solution D, draining, to obtain the pretreated fine aggregate.

[0025] Directly adding calcium phosphate into the concrete system for mixing, the introduction of phosphate leads to easy retardation of the concrete, resulting in insufficient early strength of the concrete. The present scheme adopts a pretreatment method to avoid retardation and improve the interfacial strength.

[0026] Under acidic conditions, Ca 2+ and HPO4 2- The precipitation reaction occurs on the surface of the aggregate to form a dicalcium phosphate coating, and when the aggregate is added to the concrete system, the environment has a pH>12, the dicalcium phosphate can be converted into hydroxyapatite in situ, which nucleates and interlocks with the concrete hydration products to form a continuous interfacial layer of mineral bridging and chemical bonding, improving the adhesion of the aggregate and the cement paste and enhancing the mechanical properties, which helps to improve the strength of the aggregate-cement interfacial transition zone.

[0027] Preferably, the particle size of the coarse coal gangue aggregate is 5-20mm, and the particle size of the fine coal gangue aggregate is 0.15-5mm.

[0028] Preferably, in the step S3, the concentration of the polycarboxylate superplasticizer solution is 30-50wt%.

[0029] The polycarboxylate superplasticizer can be adsorbed on the surface of the cement particles to produce electrostatic repulsion and steric hindrance, improve the fluidity of the concrete paste, allow a lower water-cement ratio, and improve the strength of the concrete.

[0030] In order to achieve the above-mentioned purposes, the present application also provides a mixed particle coal gangue-based concrete material prepared by the above-mentioned preparation method of the mixed particle coal gangue-based concrete material, which comprises the following components in parts by weight:

[0031] Silicate cement 28-56 parts, activated coal gangue powder 11-22 parts, limestone powder 2-4 parts, gypsum 1-2 parts, water 14.5-29 parts, composite colloid 0.9-1.8 parts, polycarboxylate superplasticizer solution 0.24-0.72 parts, pretreated coarse aggregate 100-200 parts, and pretreated fine aggregate 67-134 parts.

[0032] The concrete material based on the mixed particle coal gangue prepared by using the components in the above proportions can realize the purposes of improving the early strength of the concrete, high later strength and strong impermeability.

[0033] The above technical solutions of the present application at least include the following beneficial effects:

[0034] 1. By preparing the composite colloid, B and Li are uniformly assembled into the nanostructure of C-S-H gel in advance as ready-made nucleation sites to guide the Ca 2+ and SiO4 - Growth on the surface in order to make the setting acceleration of lithium ions become mild and controllable, which helps to rapidly improve the early strength of the concrete, avoid the side effects caused by directly adding lithium salt and boron salt, and also helps to optimize the pore structure of the concrete and improve the impermeability.

[0035] 2. The limestone powder plays the filling effect through physical and chemical actions, and can react with aluminum in the cement to generate hydrated calcium aluminum carbonate, consume C3A, avoid the direct and rapid reaction of C3A with water, and avoid the insufficient early strength caused by flash setting; the gypsum provides the calcium aluminate (AFt) generated by the reaction of sulfate with C3A, the calcium aluminate (AFt) will be converted into monosulfate type calcium aluminate (AFm) with unhydrated C3A, and then play a role in controlling the hydration of C3A, further ensuring the early strength of the concrete. DETAILED DESCRIPTION

[0036] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. The described embodiments are part of the embodiments of the present application, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present application belong to the scope of protection of the present application.

[0037] The portland cement used in the following examples and comparative examples is ordinary portland cement P.O 42.5R type; the polycarboxylate superplasticizer is SPF-300 polycarboxylate high-performance superplasticizer, which is purchased from Liaoning Kelong Fine Chemical Co., Ltd.

[0038] Example 1

[0039] The broken coal gangue powder of 3-5mm is uniformly spread in a refractory tray, and is pushed into a muffle furnace, and is heated to 750℃ at a speed of 10℃ / min, and is kept for 1.5h, and is cooled to obtain the coal gangue light calcined powder; the coal gangue light calcined powder 15kg, calcium hydroxide 0.3kg and triethanolamine 10g are mixed, and are ball milled at a speed of 300rpm for 90min, and the discharge is sieved, and the coarse particles are returned to the mill until D50=3-7µm, to obtain the activated coal gangue powder.

[0040] Coarse coal gangue aggregates with a particle size of 5-20 mm were washed and dried. CaCl2.2H2O 2.2 kg was dissolved in water and made up to 100 L, and the pH was adjusted to 4.2 to obtain solution C. (NH4)2HPO41.19 kg was dissolved in water and made up to 100 L, and the pH was adjusted to 4.2 to obtain solution D. The coarse coal gangue aggregates were immersed in solution C, slowly stirred for 5-10 min, drained, and then immersed in solution D, slowly stirred for 10-20 min to obtain pretreated coarse aggregates. Fine coal gangue aggregates were immersed in solution C, slowly stirred for 5-10 min, drained, and then immersed in solution D, slowly stirred for 10-20 min to obtain pretreated fine aggregates.

[0041] Deionized water 3 kg was added to a bucket, Ca(NO3)2.4H2O 0.9 kg and LiNO30.02 kg were dissolved, water was added to make up to 4.0 kg, and the pH was adjusted to 6-7 to obtain solution A. Deionized water 3.6 kg was added to another bucket, Na2SiO3.9H2O 0.8 kg and H3BO30.04 kg were dissolved, water was added to make up to 4.5 kg, and the pH was adjusted to 10.5-11.5 to obtain solution B. The two buckets were placed in a 30°C water bath, the stirrer was started, and the stirring speed was set to 700 rpm. Solution A was added to solution B at a rate of 1.25 mL / min, and the pH was adjusted to 10.8-11.2 with a small amount of NaOH. After mixing was completed, the stirring was continued for 30 min, and the system was aged for 3 h. The supernatant was removed by centrifugation, and the residue was resuspended in deionized water. This process was repeated three times until the solid content reached 20 wt%. The composite colloid was obtained.

[0042] Silicate cement 28 kg, activated coal gangue powder 11 kg, limestone powder 2 kg, gypsum 1 kg, water 14.5 kg, composite colloid 0.9 kg, polycarboxylate superplasticizer solution (concentration 50 wt%) 0.24 kg, pretreated coarse aggregates 100 kg, and pretreated fine aggregates 67 kg were used. The composite colloid was added to the water, and the mixture was stirred at a speed of 400 rpm for 1.5 min to obtain mixed water. The silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregates were added to a mixer and dry-mixed for 30 s. The mixed water was then added and stirred for 60 s. The polycarboxylate superplasticizer solution was then added in two equal portions and stirred for 90 s. Finally, the pretreated coarse aggregates were added and stirred for 60 s to obtain a mixed particle coal gangue-based concrete material.

[0043] Example 2

[0044] Spread the coal gangue coarse powder crushed to 3-5 mm evenly in a refractory tray, push into the muffle furnace, and heat up to 800℃ at a speed of 8℃ / min, keep for 1 h, cool down, and obtain the coal gangue light calcined powder; mix the coal gangue light calcined powder 15 kg, calcium hydroxide 0.45 kg and triethanolamine 15 g, ball mill at a speed of 350 rpm for 80 min, sieve the discharge, and return to mill the coarse particles until D50=3-7µm, and obtain the activated coal gangue powder.

[0045] Wash and dry the coarse coal gangue aggregate with a particle size of 5-20 mm and the fine coal gangue aggregate with a particle size of 0.15-5 mm. Dissolve CaCl2·2H2O 2.2 kg in water and make up to 100 L, adjust the pH to 4.2 to obtain solution C, and dissolve (NH4)2HPO4 1.19 kg in water and make up to 100 L, adjust the pH to 4.2 to obtain solution D; dip the coarse coal gangue aggregate into solution C, slowly stir for 5-10 min, drain, and then dip into solution D, slowly stir for 10-20 min to obtain the pretreated coarse aggregate; dip the fine coal gangue aggregate into solution C, slowly stir for 5-10 min, drain, and then dip into solution D, slowly stir for 10-20 min to obtain the pretreated fine aggregate.

[0046] Add deionized water 3.2 kg to a bucket, dissolve Ca(NO3)2·4H2O 0.9 kg and LiNO3 0.03 kg, add water to make up to 4.0 kg, and adjust the pH to 6-7 to obtain solution A; add deionized water 3.8 kg to another bucket, dissolve Na2SiO3·9H2O 0.8 kg and H3BO3 0.06 kg, add water to make up to 4.5 kg, and adjust the pH to 10.5-11.5 to obtain solution B. Place the above two buckets in a 25℃ water bath, start the stirrer to stir at 600 rpm, and at the same time, add solution A to solution B at a speed of 1.0 mL / min, adjust the pH slightly with a small amount of NaOH during the process, keep the system pH at 10.8-11.2, continue stirring for 30 min after mixing, stand for 4 h, centrifuge, resuspend with deionized water, repeat 3 times, and obtain the composite colloid with a solid content of 22wt%.

[0047] Take 56 kg of Portland 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, stir at a speed of 300 rpm for 2 min to obtain mixed water; add the Portland cement, activated coal gangue powder, limestone powder, gypsum and pretreated fine aggregate to the mixer and dry mix for 30 s, then add the mixed water and stir for 60 s; then add the polycarboxylate superplasticizer solution in two equal portions and stir for 90 s, and finally add the pretreated coarse aggregate and stir for 60 s to obtain a coal gangue-based mixed particle concrete material.

[0048] Example 3

[0049] Spread the coal gangue coarse powder crushed to 3-5 mm evenly in a refractory tray, push it into the muffle furnace, and heat it to 700°C at a rate of 12°C / min, keep it at this temperature for 2 h, and cool it to obtain coal gangue light calcined powder; mix 15 kg of coal gangue light calcined powder, 0.15 kg of calcium hydroxide and 7.5 g of triethanolamine, ball mill at a speed of 450 rpm for 60 min, sieve the discharge, and re-mill the coarse particles until D50=3-7 µm to obtain activated coal gangue powder.

[0050] Wash and dry the coarse coal gangue aggregate with a particle size of 5-20 mm and the fine coal gangue aggregate with a particle size of 0.15-5 mm. Dissolve 2.2 kg of CaCl2·2H2O in water and make up to 100 L to obtain solution C, and adjust the pH to 4.2; dissolve 1.19 kg of (NH4)2HPO4 in water and make up to 100 L to obtain solution D, and adjust the pH to 4.2; immerse the coarse coal gangue aggregate in solution C, slowly stir for 5-10 min, drain, and then immerse it in solution D, slowly stir for 10-20 min to obtain pretreated coarse aggregate; immerse the fine coal gangue aggregate in solution C, slowly stir for 5-10 min, drain, and then immerse it in solution D, slowly stir for 10-20 min to obtain pretreated fine aggregate.

[0051] To a bucket, add deionized water 2.8 kg, dissolve Ca(N03)2*4H20 0.9 kg and LiN03 0.015 kg, add water to constant volume to 4.0 kg, adjust pH to 6-7, to obtain solution A; to another bucket, add deionized water 3.5 kg, dissolve Na2Si03*9H20 0.8 kg and H3B03 0.03 kg, add water to constant volume to 4.5 kg, adjust pH to 10.5-11.5, to obtain solution B. Place the above two buckets in a water bath of 25-35 °C, start the stirrer, stir at 800 rpm, at the same time, add solution A to solution B at a speed of 1.5 mL / min, adjust the pH slightly with a small amount of NaOH, keep the system pH at 10.8-11.2, after mixing, continue stirring for 30 min, stand for 2 h, centrifuge, remove the supernatant, resuspend with deionized water, repeat 3 times, until the solid content is 18 wt%, to obtain a composite colloid.

[0052] Take Portland cement 42 kg, activated coal gangue powder 16.5 kg, limestone powder 3 kg, gypsum 1.5 kg, water 21.75 kg, composite colloid 1.35 kg, polycarboxylate superplasticizer solution (concentration of 40 wt%) 0.45 kg, pretreated coarse aggregate 150 kg and pretreated fine aggregate 100 kg; add the composite colloid to the water, stir at a speed of 500 rpm for 1 min, to obtain mixed water; add Portland cement, activated coal gangue powder, limestone powder, gypsum and pretreated fine aggregate to the mixer, dry mix for 30 s, then add mixed water and stir for 60 s; then add polycarboxylate superplasticizer solution in two equal portions and stir for 90 s, finally add pretreated coarse aggregate and stir for 60 s, to obtain a mixed particle coal gangue-based concrete material.

[0053] Example 4

[0054] Spread the coal gangue coarse powder crushed to 3-5 mm evenly in a refractory tray, push into the muffle furnace, heat up to 750 °C at a speed of 8 °C / min, keep for 1.5 h, cool down, to obtain coal gangue light calcined powder; mix coal gangue light calcined powder 15 kg, calcium hydroxide 0.25 kg and triethanolamine 12 g, ball mill at a speed of 400 rpm for 70 min, sieve the discharge, return the coarse particles to the mill, until D50 = 3-7 pm, to obtain activated coal gangue powder.

[0055] 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 were washed and dried. CaCl2·2H2O 2.2 kg was dissolved in water and made up to 100 L, and the pH was adjusted to 4.2 to obtain solution C. (NH4)2HPO4 1.19 kg was dissolved in water and made up to 100 L, and the pH was adjusted to 4.2 to obtain solution D. The coarse coal gangue aggregate was immersed in solution C, slowly stirred for 5-10 min, drained, and then immersed in solution D, slowly stirred for 10-20 min to obtain pretreated coarse aggregate. The fine coal gangue aggregate was immersed in solution C, slowly stirred for 5-10 min, drained, and then immersed in solution D, slowly stirred for 10-20 min to obtain pretreated fine aggregate.

[0056] Deionized water 3.2 kg was added to a bucket, Ca(NO3)2·4H2O 0.9 kg and LiNO3 0.03 kg were dissolved, water was added to make up to 4.0 kg, and the pH was adjusted to 6-7 to obtain solution A. Deionized water 3.5 kg was added to another bucket, Na2SiO3·9H2O 0.8 kg and H3BO3 0.03 kg were dissolved, water was added to make up to 4.5 kg, and the pH was adjusted to 10.5-11.5 to obtain solution B. The two buckets were placed in a 30°C water bath, the stirrer was started, and stirring was carried out at 750 rpm. At the same time, solution A was added to solution B at a rate of 1.3 mL / min, and a small amount of NaOH was used to fine-tune the pH to maintain the system pH at 10.8-11.2. After mixing, stirring was continued for 30 min, and the mixture was allowed to stand for 2.5 h. The supernatant was removed by centrifugation, and the residue was resuspended in deionized water. This process was repeated three times until the solid content reached 22 wt%. The composite colloid was obtained.

[0057] Silicate cement 28 kg, activated coal gangue powder 11 kg, limestone powder 2 kg, gypsum 1 kg, water 14.5 kg, composite colloid 0.9 kg, polycarboxylate superplasticizer solution (concentration 50 wt%) 0.24 kg, pretreated coarse aggregate 100 kg, and pretreated fine aggregate 67 kg were used. The composite colloid was added to the water, and stirring was carried out at a speed of 400 rpm for 1.5 min to obtain mixed water. The silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregate were added to a mixer and dry-mixed for 30 s. The mixed water was then added and stirred for 60 s. The polycarboxylate superplasticizer solution was then added in two equal portions and stirred for 90 s. Finally, the pretreated coarse aggregate was added and stirred for 60 s to obtain a mixed particle coal gangue-based concrete material.

[0058] Example 5

[0059] Spread the coal gangue coarse powder crushed to 3-5 mm evenly in a refractory tray, push into the muffle furnace, and heat up to 700℃ at a rate of 9℃ / min, keep for 2 h, cool down, and obtain the coal gangue light calcined powder; mix the coal gangue light calcined powder 15 kg, calcium hydroxide 0.45 kg and triethanolamine 15 g, ball mill at a speed of 350 rpm for 75 min, sieve the discharge, and return to mill the coarse particles until D50=3-7µm, and obtain the activated coal gangue powder.

[0060] Wash and dry the coarse coal gangue aggregate with a particle size of 5-20 mm and the fine coal gangue aggregate with a particle size of 0.15-5 mm. Dissolve CaCl2·2H2O 2.2 kg in water and make up to 100 L, adjust the pH to 4.2 to obtain solution C, and dissolve (NH4)2HPO4 1.19 kg in water and make up to 100 L, adjust the pH to 4.2 to obtain solution D; dip the coarse coal gangue aggregate into solution C, slowly stir for 5-10 min, drain, and then dip into solution D, slowly stir for 10-20 min to obtain the pretreated coarse aggregate; dip the fine coal gangue aggregate into solution C, slowly stir for 5-10 min, drain, and then dip into solution D, slowly stir for 10-20 min to obtain the pretreated fine aggregate.

[0061] Add deionized water 3 kg to a bucket, dissolve Ca(NO3)2·4H2O 0.9 kg and LiNO3 0.025 kg, add water to make up to 4.0 kg, and adjust the pH to 6-7 to obtain solution A; add deionized water 3.8 kg to another bucket, dissolve Na2SiO3·9H2O 0.8 kg and H3BO3 0.05 kg, add water to make up to 4.5 kg, and adjust the pH to 10.5-11.5 to obtain solution B. Place the above two buckets in a 35℃ water bath, start the stirrer to stir at 650 rpm, and at the same time, add solution A to solution B at a rate of 1.5 mL / min, adjust the pH slightly with a small amount of NaOH during the process to keep the system pH at 10.8-11.2, continue stirring for 30 min after mixing, stand for 3.5 h, centrifuge, resuspend with deionized water, repeat 3 times, and obtain the composite colloid with a solid content of 18 wt%.

[0062] Silicate cement 42 kg, activated coal gangue powder 16.5 kg, limestone powder 3 kg, gypsum 1.5 kg, water 21.75 kg, composite colloid 1.35 kg, polycarboxylate superplasticizer solution (concentration of 40 wt%) 0.45 kg, pretreated coarse aggregate 150 kg, and pretreated fine aggregate 100 kg; the composite colloid is added to water, stirred at a speed of 500 rpm for 1 min to obtain mixed water; the silicate cement, activated coal gangue powder, limestone powder, gypsum, and pretreated fine aggregate are added to a mixer and dry-mixed for 30 s, then the mixed water is added and stirred for 60 s; then the polycarboxylate superplasticizer solution is added in two equal portions and stirred for 90 s, and finally the pretreated coarse aggregate is added and stirred for 60 s to obtain a coal gangue-based mixed particle concrete material.

[0063] Example 6

[0064] The coal gangue coarse powder broken to 3-5 mm is evenly spread in a refractory tray and pushed into a muffle furnace, which is heated to 800°C at a rate of 11°C / min, and kept at this temperature for 1 h, and then cooled to obtain coal gangue light calcined powder; the coal gangue light calcined powder 15 kg, calcium hydroxide 0.15 kg, and triethanolamine 7.5 g are mixed, ball-milled at a speed of 450 rpm for 60 min, the discharge is sieved, and the coarse particles are returned to the mill until D50=3-7 µm to obtain activated coal gangue powder.

[0065] The coarse coal gangue aggregate with a particle size of 5-20 mm and the fine coal gangue aggregate with a particle size of 0.15-5 mm are washed and dried. CaCl2·2H2O 2.2 kg is dissolved in water and diluted to 100 L, and the pH is adjusted to 4.2 to obtain solution C; (NH4)2HPO41.19 kg is dissolved in water and diluted 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, slowly stirred for 5-10 min, drained, and then immersed in solution D, slowly stirred for 10-20 min to obtain pretreated coarse aggregate; the fine coal gangue aggregate is immersed in solution C, slowly stirred for 5-10 min, drained, and then immersed in solution D, slowly stirred for 10-20 min to obtain pretreated fine aggregate.

[0066] A solution A was prepared by adding deionized water 2.8 kg into a bucket, dissolving Ca(NO3)2·4H2O 0.9 kg and LiNO3 0.015 kg, adding water to make up to 4.0 kg, adjusting pH to 6-7; a solution B was prepared by adding deionized water 3.8 kg into another bucket, dissolving Na2SiO3·9H2O 0.8 kg and H3BO3 0.06 kg, adding water to make up to 4.5 kg, adjusting pH to 10.5-11.5. The two buckets were placed in a 25℃ water bath, and a stirrer was started to stir at 700 rpm, while solution A was added to solution B at a speed of 1.2 mL / min, and a small amount of NaOH was used to fine-tune the pH to keep the system pH at 10.8-11.2 during the process. After mixing, the system was continuously stirred for 30 min, and then aged for 3 h. After centrifugation, the supernatant was removed, and the residue was resuspended with deionized water, and the process was repeated 3 times until the solid content reached 20 wt%, to obtain a composite colloid.

[0067] A silicate cement 56 kg, an activated coal gangue powder 22 kg, a limestone powder 4 kg, gypsum 2 kg, water 29 kg, a composite colloid 1.8 kg, a polycarboxylate superplasticizer solution (concentration 30 wt%) 0.72 kg, pretreated coarse aggregate 200 kg, and pretreated fine aggregate 134 kg were taken; the composite colloid was added to the water, and stirred at a speed of 300 rpm for 2 min to obtain mixed water; the silicate cement, the activated coal gangue powder, the limestone powder, the gypsum, and the pretreated fine aggregate were dry-mixed in a mixer for 30 s, and then the mixed water was added and stirred for 60 s; then the polycarboxylate superplasticizer solution was added in two equal portions and stirred for 90 s, and finally the pretreated coarse aggregate was added and stirred for 60 s, to obtain a concrete material based on mixed particle coal gangue.

[0068] The present application also carried out comparative examples and related tests.

[0069] Comparative Example 1

[0070] Comparative Example 1 and Example 1 differ in that no composite colloid was prepared in Comparative Example 1, but silicate cement was used instead, and the other components and preparation methods were the same as in Example 1, to prepare a concrete material based on mixed particle coal gangue.

[0071] Comparative Example 2

[0072] Comparative Example 2 and Example 1 differ in that no activated coal gangue powder was used in Comparative Example 2, but ordinary coal gangue powder was used instead, and the other components and preparation methods were the same as in Example 1, to prepare a concrete material based on mixed particle coal gangue.

[0073] Performance test

[0074] The mixed particle coal gangue-based concrete materials prepared from Examples 1-6 and Comparative Examples 1-2 were prepared into cubic samples with a size of 150 mm x 150 mm x 150 mm, and the early strength and late strength of the samples were tested according to GB / T 50081-2019 "Standard for Testing Methods of Physical and Mechanical Properties of Concrete", and the compressive strengths at 1 day, 3 days and 28 days were tested;

[0075] The mixed particle coal gangue-based concrete materials prepared from Examples 1-6 and Comparative Examples 1-2 were prepared into circular truncated cone samples with a top diameter of 175 mm, a bottom diameter of 185 mm and a height of 150 mm, and after curing for 28 days, the impermeability grade was tested according to GB / T 50082-2009 "Standard for Testing Methods of Long-term Performance and Durability of Ordinary Concrete", using the step-by-step pressurization method, starting from 0.1 MPa, increasing the water pressure by 0.1 MPa every 8 hours, until 3 out of 6 samples were permeated, and the impermeability grade = maximum pressure value x 10-1;

[0076] The slump values of the mixed particle coal gangue-based concrete materials prepared from Examples 1-6 and Comparative Examples 1-2 were tested according to GB / T 50080-2016 "Standard for Testing Methods of Performance of Concrete Mixtures";

[0077] In summary, the test results are shown in Table 1.

[0078] Table 1

[0079]

[0080] As can be seen from Table 1, compared with Example 1, the 1d and 3d compressive strengths of the mixed particle coal gangue-based concrete material prepared from Comparative Example 1 are significantly lower, the early strength is slowly improved, and the impermeability is decreased, indicating that the composite colloid helps to rapidly improve the early strength of the concrete and also optimizes the pore structure of the concrete to improve the impermeability; the 28d compressive strength of the mixed particle coal gangue-based concrete material prepared from Comparative Example 2 is lower than that of the mixed particle coal gangue-based concrete material prepared from Example 1, and its impermeability grade is the lowest, indicating that the use of activated coal gangue powder as an admixture can reduce the porosity of the concrete through the pozzolanic reaction, thereby improving the late strength and impermeability.

[0081] The slump of the mixed particle coal gangue-based concrete material prepared from Comparative Example 1 is significantly lower than that of Examples 1-6, indicating that the addition of the composite colloid can reduce the slump loss of the concrete and improve the construction quality.

[0082] The above is the preferred embodiment of the present application, and those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for producing a concrete material based on mixed granular coal gangue, characterized by, The method comprises the following steps: Step S1, mixing coal gangue light calcined powder, calcium hydroxide and triethanolamine, and ball milling to obtain activated coal gangue powder; Step S2, dissolving Ca(NO3)2·4H2O and LiNO3 in deionized water to obtain solution A; dissolving Na2SiO3·9H2O and H3BO3 in deionized water to obtain solution B; stirring solution A into solution B, adjusting pH to 10.8-11.2, aging, washing and purifying to obtain a composite colloid; Step S3, mixing and stirring the composite colloid with water to obtain mixed water; dry mixing Portland cement, activated coal gangue powder, limestone powder, gypsum and pretreated fine aggregate in a blender, stirring after adding mixed water, stirring after adding polycarboxylate superplasticizer solution, and finally stirring after adding pretreated coarse aggregate to obtain a mixed particle coal gangue-based concrete material; The preparation of the pretreated coarse aggregate comprises the following steps: mixing CaCl2·2H2O with water to obtain solution C, and mixing (NH4)2HPO4 with water to obtain solution D; dipping coarse coal gangue aggregate into solution C, draining, and then dipping into solution D, and draining to obtain pretreated coarse aggregate; the preparation of the pretreated fine aggregate comprises the following steps: dipping fine coal gangue aggregate into solution C, draining, and then dipping into solution D, and draining to obtain pretreated fine aggregate.

2. The method of claim 1, wherein the method of preparing a mixed particle coal gangue-based concrete material is characterized by, In the step S1, the preparation of the coal gangue light calcined powder comprises the following steps: Uniformly spreading broken coal gangue coarse powder with a particle size of 3-5 mm in a refractory tray, pushing into a muffle furnace, heating, keeping warm, and cooling to obtain coal gangue light calcined powder.

3. The method of claim 2, wherein the method further comprises the step of: The heating rate is 8-12℃ / min, the temperature is 700-800℃, and the keeping warm time is 1-2h. ​ 4. The method of claim 1, wherein the method of preparing a mixed particle coal gangue-based concrete material is characterized by, In the step S1, the ball milling speed is 300-450rpm, and the time is 60-90min.

5. The method of claim 1, wherein the method of preparing a mixed particle coal gangue-based concrete material is characterized by, In the step S2, the stirring speed is 600-800rpm, and the speed of adding solution A into solution B is 1-1.5mL / min.

6. The method of claim 1, wherein the method of preparing a mixed particle coal gangue-based concrete material is characterized by, In the step S3, the mixing and stirring speed is 300-500rpm, and the time is 1-2min.

7. The method of claim 1, wherein the method further comprises: mixing the coal gangue with the cement, the sand, and the water to form a mixture; and mixing the mixture with the additive to form the concrete material. The particle size of the coarse coal gangue aggregate is 5-20mm, and the particle size of the fine coal gangue aggregate is 0.15-5mm.

8. The method of claim 1, wherein the method of preparing a mixed particle coal gangue-based concrete material is characterized by, In the step S3, the concentration of the polycarboxylate superplasticizer solution is 30-50wt%.

9. A mixed particle coal gangue based concrete material prepared by the method of any one of claims 1-8, characterized in that, The method comprises the following components by weight: Portland cement 28-56 parts, activated coal gangue powder 11-22 parts, limestone powder 2-4 parts, gypsum 1-2 parts, water 14.5-29 parts, composite colloid 0.9-1.8 parts, polycarboxylate superplasticizer solution 0.24-0.72 parts, pretreated coarse aggregate 100-200 parts, and pretreated fine aggregate 67-134 parts.

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