Concrete viscosity modification material and preparation method thereof

Abstract

The invention discloses a concrete viscosity modified material and a preparation method thereof, and belongs to the technical field of building materials. The concrete viscosity modifying material comprises the following components in percentage by mass: 65%-85% of a mineral admixture, 15%-35% of a modified tackifier, 1%-5% of an inorganic thixotropic agent and 1%-5% of an organic thixotropic agent, wherein the modified tackifier is obtained by taking rice hull ash obtained by calcining rice hulls, pretreated biogel and a silane coupling agent as raw materials, and performing dispersion, standing and spray drying. The modified tackifier is prepared from the rice hull ash, the biological glue and the silane coupling agent, then the mineral admixture, the inorganic thixotropic agent and the organic thixotropic agent which have high-quality thixotropic performance are compounded, the finally prepared concrete viscosity modified material has excellent thixotropy, the working performance of concrete can be improved, and meanwhile, the concrete viscosity is improved. The problems of bleeding, segregation and the like of mortar and concrete are effectively solved, and the application value is high.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a concrete viscosity modifying material and a preparation method thereof. Background Art

[0002] With the advancement of science and technology and the development of society, a large number of projects such as highways, railways, hydropower stations, and civil construction have been built, and the application of high-performance and ultra-high-performance concrete has become increasingly widespread. At the same time, with the increasing consumption of natural sand and gravel resources and the increasing national environmental awareness, a large amount of machine-made sand has been applied to concrete. Machine-made sand is made from natural rocks, pebbles, mine tailings, industrial slag, construction solid waste and other parent materials through crushing and screening. The change of machine-made sand parent materials can easily cause fluctuations in the quality of machine-made sand. Machine-made sand has sharp corners, irregular surfaces, and discontinuous grading, which is prone to grading faults. When it is applied to concrete, especially when it is applied to high-performance and ultra-high-performance concrete, problems such as segregation, bleeding, and stratification often occur. At the same time, because its stone powder content is difficult to control, it is easy to have compatibility problems with admixtures, which further affects the performance of concrete.

[0003] In order to solve the above problems, people often add polymer thickeners such as Wenlun gum, xanthan gum, cellulose ether, polyacrylamide, polyvinyl alcohol, etc. to concrete. Although these thickeners can alleviate the problems of concrete segregation and bleeding to a certain extent, they will also have a negative impact on the working performance and strength of concrete. In this context, concrete viscosity modification materials have gradually become a research hotspot.

[0004] Patent CN 117623666 A discloses a concrete viscosity modifier and its preparation method and application, which mainly comprises reacting a carboxylated multi-walled carbon nanotube aqueous solution with a mass fraction of 0.1% to 3%, a hydroxyethyl cellulose aqueous solution with a mass fraction of 0.1% to 1.5% and an appropriate amount of p-toluenesulfonic acid at 105-120°C for 2-3 hours, and then centrifuging, washing and drying to obtain a concrete viscosity modifier, which increases the viscosity of concrete while reducing the effect on fluidity and increasing the workability of concrete. However, carbon nanotubes are tubular structures and are likely to be in a disordered arrangement in the concrete slurry, so the effect on fluidity is very limited, and carbon nanotube materials are expensive and difficult to promote. Patent CN108863148A discloses a self-compacting concrete viscosity modifier, which is composed of 30% to 40% nano-silicon dioxide, 10% to 20% ultrafine mineral powder, 30% to 45% heavy calcium carbonate, 2% to 8% redispersible latex powder, 2% to 8% hydroxypropyl methylcellulose, and 1% to 5% polyvinyl alcohol by mass percentage. Although the self-compacting concrete viscosity modifier can solve the problems of concrete bleeding and segregation, it will inevitably affect the fluidity because it contains a large amount of nano-silicon dioxide, redispersible latex powder, hydroxypropyl methylcellulose, polyvinyl alcohol and other thickening materials in the ratio. Although the above technical scheme can solve the problems of concrete bleeding and segregation to a certain extent, it will more or less have a negative impact on the fluidity of concrete, and then affect the workability of concrete. Summary of the invention

[0005] In view of the above deficiencies in the prior art, the present invention provides a concrete viscosity modifying material and a preparation method thereof, which can effectively solve the problems of water bleeding and segregation of mortar and concrete while improving the working performance of concrete.

[0006] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0007] A concrete viscosity modifying material, comprising the following components in percentage by mass: 65% to 85% of a mineral admixture, 15% to 35% of a modified viscosity enhancer, 1% to 5% of an inorganic thixotropic agent, and 1% to 5% of an organic thixotropic agent;

[0008] Wherein, the preparation method of the modified tackifier comprises the following steps:

[0009] (1) Drying, grinding and sieving rice husks to obtain rice husk powder, soaking the rice husk powder in an acid solution, sieving, washing and drying, and then calcining to obtain rice husk ash; crushing the bio-glue into ultrafine powder, and evenly dispersing the ultrafine powder bio-glue and a silane coupling agent in anhydrous ethanol to obtain a dispersion;

[0010] (2) Add rice husk ash to the dispersion and disperse it evenly to obtain a mixture. After the mixture is sealed and allowed to stand for 24 hours, it is spray-dried to obtain a modified thickener.

[0011] Preferably, the grinding is performed using a planetary ball mill for 20 to 40 min.

[0012] Preferably, the acid solution is a 2-4 mol / L nitric acid solution at 60-80°C.

[0013] Preferably, the rice husk powder is soaked in the acid solution for 2 to 4 hours.

[0014] Preferably, the calcination is a two-stage calcination, wherein the heating rate of the first stage calcination is 10 to 20 °C / min, the temperature is raised to 500 °C and calcined for 2 to 3 h, and the heating rate of the second stage calcination is 5 to 10 °C / min, the temperature is raised to 600 °C and calcined for 1 to 2 h.

[0015] Preferably, the bio-gum is one or more of xanthan gum, Brunei gum, guar gum, alginate and carrageenan.

[0016] Further preferably, the bio-gum is xanthan gum.

[0017] Preferably, the bio-glue is crushed by using a jet mill to crush the bio-glue; the particle size of the ultrafine powder bio-glue is ≤10 μm, and the average particle size is 2 to 5 μm.

[0018] Preferably, the weight ratio of the bio-glue to anhydrous ethanol is (0.1-0.5):100.

[0019] Preferably, the weight ratio of the silane coupling agent to the bio-glue is (1-5):100.

[0020] Preferably, the silane coupling agent is KH570 (triaminosilane).

[0021] Preferably, the weight ratio of the rice husk ash to the dispersion is (10-20):100.

[0022] Preferably, the spray drying method is: spray drying is performed using a nitrogen closed-loop circulation spray dryer, and the inlet air temperature of the spray drying is 85-100°C.

[0023] Preferably, the mineral admixture is a compound of mineral powder, fly ash and metakaolin, and the weight ratio of the mineral powder, fly ash and metakaolin is (30 ~ 50): (20 ~ 40): (30 ~ 50).

[0024] Further preferably, the mineral powder is ultrafine mineral powder, and the specific surface area of ​​the ultrafine mineral powder is ≥ 700 m 2 / kg, CaO content ≥ 45%, SiO2 content ≥ 25%, Al2O3 content ≥ 10%, 28d activity index ≥ 125%.

[0025] Further preferably, the fly ash is primary fly ash, and the specific surface area of ​​the primary fly ash is ≥ 450m 2 / kg, activity index ≥ 75%.

[0026] Further preferably, the high-activity ore is a low-temperature calcined high-activity ore, wherein the Al2O3 content of the high-activity ore is ≥50%, the SiO2 content is ≥40%, the particle size is ≤18 μm, and the specific surface area is ≥4000 m 2 / kg.

[0027] Preferably, the organic thixotropic agent is one or more of cellulose ether, starch ether and polyacrylamide.

[0028] Further preferably, the organic thixotropic agent is cellulose ether, and more preferably, the organic thixotropic agent is hydroxypropyl methylcellulose ether with a viscosity of 400.

[0029] Preferably, the inorganic thixotropic agent is fumed silica, and the specific surface area of ​​the fumed silica is ≥ 200m 2 / g, bulk density ≤ 50g / L, SiO2 content ≥ 99.8%.

[0030] The present invention prepares a modified tackifier based on rice husk ash-bioglue by first making rice husk into rice husk ash, and then mixing and drying the mixture with ultrafine powder bioglue and a silane coupling agent. Then, a mineral admixture, an inorganic thixotropic agent and an organic thixotropic agent with high-quality thixotropic properties are compounded. The concrete viscosity modifying material finally prepared has excellent thixotropy, can effectively solve the problems of bleeding, segregation and the like of mortar and concrete while improving the working performance of concrete. Among them, the rice husk ash of the present invention is a volcanic ash admixture obtained by burning rice husks at a specific temperature, mainly composed of nano-scale amorphous SiO2, and its structure not only has a large number of micron-scale honeycomb pores, but also contains a large number of nano-scale pores formed by non-tight adhesion of SiO2 gel particles, so it has a large specific surface area and ultra-high volcanic ash activity; using it in mortar or concrete in conjunction with bio-glue and silane coupling agent can greatly improve the compressive strength, impermeability and durability of concrete; in addition, rice husk ash retains its special porous structure in the modified thickener, has extremely strong adsorption, can absorb excess water in cement slurry, and store it in the pores, which can effectively alleviate the segregation and water seepage problems of mortar or concrete; as hydration proceeds, the water content in the hardened slurry gradually decreases, and when the internal humidity of the concrete drops to a critical value, under the action of osmotic pressure, the stored water will gradually be released into the interior of the concrete, and internal curing will be performed on it, further improving the strength of the concrete.

[0031] The bio-glue of the present invention is a long-chain polymer of polysaccharide, and the molecular side chain contains a large number of hydrophilic functional groups, has good water solubility, is dissolved in water, and the main chain and the side chain are intertwined to form a spatial network structure. Due to its unique molecular structure, it has extremely excellent water retention, thickening, suspension and other properties. It is used in mortar or concrete in coordination with rice husk ash and silane coupling agent, and can achieve excellent water retention and thickening effects and unique rheological properties at a very small dosage, and can effectively prevent the segregation and bleeding of mortar concrete. The bio-glue is prepared into an ultrafine powder, which can promote the adsorption of the porous structure of rice husk ash on the bio-glue. In addition, the present invention uses an air flow mill to crush the bio-glue, and then uses a nitrogen closed-loop spray dryer to spray-dry the composite material composed of rice husk ash-ultrafine bio-glue, which can avoid the oxidation of the surface of the colloidal molecules or the destruction of other molecular structures caused by factors such as high temperature and friction in the conventional crushing process, and avoids the destruction of the pore structure in the composite material composed of rice husk ash-ultrafine bio-glue.

[0032] The present invention utilizes the micron-scale honeycomb pore structure of rice husk ash to adsorb pretreated ultrafine bio-glue, so that the bio-glue is slowly released, and then spray-dried to obtain a modified thickener, which can reduce the influence of the bio-glue on the fluidity of the slurry; at the same time, the modified thickener also has the dual effects of early water absorption and thickening of rice husk ash and thickening effect of the bio-glue in the slow release process, which can further reduce the risk of water seepage and segregation of mortar concrete.

[0033] The preparation method of the concrete viscosity modifying material comprises: uniformly mixing a mineral admixture, a modified viscosity enhancer, an inorganic thixotropic agent and an organic thixotropic agent to obtain the viscosity modifying material.

[0034] Compared with the prior art, the present invention is beneficial in that:

[0035] (1) The present invention pre-treats a bio-glue with excellent thixotropy but great influence on fluidity, and then adsorbs it into rice husk ash to prepare a modified thickener; then, a mineral admixture, an inorganic thixotropic agent and an organic thixotropic agent with high-quality thixotropic properties are compounded to finally prepare a concrete viscosity modifying material, which is used in mortar or concrete. This not only reduces the influence of pure bio-glue on the fluidity of mortar or concrete, but also the modified thickener has the dual effects of water absorption and thickening of rice husk ash and slow-release thickening of bio-glue, and can effectively solve the problems of water seepage and segregation of mortar and concrete.

[0036] (2) The rice husk ash in the modified viscosity enhancer prepared by the present invention is rich in a large amount of nano-silicon dioxide and has extremely strong volcanic ash activity. The modified viscosity enhancer is used to prepare a concrete viscosity modifier, which can increase the strength, impermeability and durability of the concrete. At the same time, the modified viscosity enhancer also contains a large number of micron-scale honeycomb pores and nano-scale pores brought by the rice husk ash. The prepared concrete viscosity modifier can absorb excess free water in the slurry and slowly release it in the later stage of hydration to achieve the effect of internal curing, further improve the strength of the concrete, and effectively offset the negative effects of bio-glue and organic thixotropic agent on the strength of concrete.

[0037] (3) In the process of preparing the modified thickener, the present invention uses a jet mill to perform ultrafine grinding on the bio-glue, and then uses a nitrogen closed-loop spray dryer to spray-dry the composite material composed of rice husk ash and ultrafine bio-glue, thereby avoiding the damage to the molecular structure of the bio-glue and the pore structure of the rice husk ash caused by traditional grinding methods and subsequent treatment processes. At the same time, the anhydrous ethanol can be recycled and reused, which is safe and environmentally friendly.

[0038] (4) The active mineral admixture of the present invention is obtained by compounding ultrafine mineral powder, ultrafine fly ash and low-temperature calcined high-activity kaolin. When used in concrete viscosity modifying materials, it can increase the cohesion of concrete, improve the strength of concrete, and synergistically improve the cohesion of concrete and prevent segregation and bleeding. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The present invention provides a concrete viscosity modifying material, comprising the following components in percentage by mass: 65% to 85% of a mineral admixture, 15% to 35% of a modified viscosity enhancer, 1% to 5% of an inorganic thixotropic agent, and 1% to 5% of an organic thixotropic agent;

[0041] Wherein, the preparation method of the modified tackifier comprises the following steps:

[0042] (1) Drying, grinding and sieving rice husks to obtain rice husk powder, soaking the rice husk powder in an acid solution, sieving, washing and drying, and then calcining to obtain rice husk ash; crushing the bio-glue into ultrafine powder, and evenly dispersing the ultrafine powder bio-glue and a silane coupling agent in anhydrous ethanol to obtain a dispersion;

[0043] (2) Add rice husk ash to the dispersion and disperse it evenly to obtain a mixture. After the mixture is sealed and allowed to stand for 24 hours, it is spray-dried to obtain a modified thickener.

[0044] In some examples, the acid solution is a 2-4 mol / L nitric acid solution at 60-80°C.

[0045] In some examples, the rice husk powder is soaked in the acid solution for 2 to 4 hours.

[0046] The calcination is a two-stage calcination.

[0047] In some examples, the heating rate of the first calcination is 10 to 20 °C / min, and the temperature is raised to 500 °C for 2 to 3 h. The heating rate of the second calcination is 5 to 10 °C / min, and the temperature is raised to 600 °C for 1 to 2 h.

[0048] In some examples, the bio-gum is one or more of xanthan gum, Brunei gum, guar gum, alginate, and carrageenan.

[0049] In some examples, the weight ratio of the bio-glue to anhydrous ethanol is (0.1 ~ 0.5): (10 ~ 20): 100; the weight ratio of the silane coupling agent to the ultrafine powder bio-glue is (1 ~ 5): 100; the weight ratio of the rice husk ash to the dispersion is (10 ~ 20): 100.

[0050] In some examples, the organic thixotropic agent is one or more of cellulose ether, starch ether, and polyacrylamide.

[0051] In some examples, the mineral admixture is a mixture of mineral powder, fly ash, and kaolin, and the weight ratio of the mineral powder, fly ash, and kaolin is (30 ~ 50): (20 ~ 40): (30 ~ 50).

[0052] In the following specific embodiments, the particle size of the ultrafine powder bio-glue is ≤10 μm, and the average particle size is 2 to 5 μm; the organic thixotropic agent is hydroxypropyl methylcellulose ether with a viscosity of 400; the spray drying method is: spray drying is performed using a nitrogen closed-loop spray dryer, and the inlet air temperature of the spray drying is 90°C; the mineral admixture is a compound of mineral powder, fly ash, and metakaolin in a weight ratio of 40:30:30; the mineral powder is an ultrafine mineral powder, and the specific surface area of ​​the ultrafine mineral powder is ≥700 m 2 / kg, CaO content ≥ 45%, SiO2 content ≥ 25%, Al2O3 content ≥ 10%, 28d activity index ≥ 125%; the fly ash is first-class fly ash, and the specific surface area of ​​the first-class fly ash is ≥ 450 m 2 / kg, activity index ≥ 75%; the high-activity region is a low-temperature calcined high-activity region, the high-activity region has an Al2O3 content ≥ 50%, a SiO2 content ≥ 40%, a particle size ≤ 18 μm, and a specific surface area ≥ 400 m 2 / kg; the inorganic thixotropic agent is fumed silica, and the specific surface area of ​​the fumed silica is ≥ 200 m 2 / g, bulk density ≤ 50 g / L, SiO2 content ≥ 99.8%.

[0053] Example 1

[0054] A concrete viscosity modifying material, the preparation steps are as follows:

[0055] (1) Preparation of rice husk ash: Wash the rice husk with water to remove the dust on the surface, dry it at 105 °C for 2 h, and then use a planetary ball mill to mill it for 40 min. Pass the milled rice husk powder through a 100-mesh square hole sieve. Take the sieve and soak it in a 60 °C, 2 mol / L nitric acid solution for 2 h. Filter out the rice husk powder with a 200-mesh sieve and wash it repeatedly until the water washing liquid is neutral. Dry the rice husk powder in a 105 °C oven for 2 h and then place it in a muffle furnace. First, heat it to 500 °C at a heating rate of 10 °C / min and keep it at this temperature for 2 h. Then, heat it to 600 °C at a heating rate of 5 °C / min and keep it at this temperature for 2 h. Then, naturally cool it to room temperature. The calcined product is rice husk ash.

[0056] (2) Pretreatment of bio-gum: Xanthan gum was crushed into ultrafine powder in a jet mill. 10 g of ultrafine powder xanthan gum with a particle size range of 2 to 5 μm was mixed with 0.5 g KH570 and 2000 g anhydrous ethanol, and dispersed in an ultrasonic disperser for 30 min to obtain a dispersion.

[0057] (3) Preparing a modified tackifier: adding 200 g of rice husk ash to the dispersion prepared in step (2), and performing ultrasonic dispersion for 15 min to obtain a mixture. After standing for 24 h, the mixture was spray-dried using a nitrogen closed-loop spray dryer to obtain a modified tackifier.

[0058] (4) 75 g of mineral admixture, 15 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0059] Example 2

[0060] A concrete viscosity modifying material, the preparation steps are as follows:

[0061] (1) Preparation of rice husk ash: Wash the rice husk with water to remove the dust on the surface, dry it at 105 °C for 2 h, and then use a planetary ball mill to mill it for 40 min. Pass the milled rice husk powder through a 100-mesh square hole sieve. Take the sieve and soak it in a 60 °C, 2 mol / L nitric acid solution for 2 h. Filter out the rice husk powder with a 200-mesh sieve and wash it repeatedly until the water washing liquid is neutral. Dry the rice husk powder in a 105 °C oven for 2 h and then place it in a muffle furnace. First, heat it to 500 °C at a heating rate of 10 °C / min and keep it at this temperature for 2 h. Then, heat it to 600 °C at a heating rate of 5 °C / min and keep it at this temperature for 2 h. Then, naturally cool it to room temperature. The calcined product is rice husk ash.

[0062] (2) Pretreatment of bio-gum: Xanthan gum was crushed into ultrafine powder in a jet mill. 4 g of ultrafine powder xanthan gum with a particle size range of 2 to 5 μm was mixed with 0.04 g KH570 and 2000 g anhydrous ethanol, and dispersed in an ultrasonic disperser for 30 min to obtain a dispersion.

[0063] (3) Preparing a modified tackifier: adding 200 g of rice husk ash to the dispersion prepared in step (2), and performing ultrasonic dispersion for 15 min to obtain a mixture. After standing for 24 h, the mixture was spray-dried using a nitrogen closed-loop spray dryer to obtain a modified tackifier.

[0064] (4) 75 g of mineral admixture, 15 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0065] Example 3

[0066] A concrete viscosity modifying material, the preparation steps are as follows:

[0067] (1) Preparation of rice husk ash: Wash the rice husk with water to remove the dust on the surface, dry it at 105 °C for 2 h, and then use a planetary ball mill to mill it for 40 min. Pass the milled rice husk powder through a 100-mesh square hole sieve. Take the sieve and soak it in a 60 °C, 2 mol / L nitric acid solution for 2 h. Filter out the rice husk powder with a 200-mesh sieve and wash it repeatedly until the water washing liquid is neutral. Dry the rice husk powder in a 105 °C oven for 2 h and then place it in a muffle furnace. First, heat it to 500 °C at a heating rate of 10 °C / min and keep it at this temperature for 2 h. Then, heat it to 600 °C at a heating rate of 5 °C / min and keep it at this temperature for 2 h. Then, naturally cool it to room temperature. The calcined product is rice husk ash.

[0068] (2) Pretreatment of bio-gum: Xanthan gum was crushed into ultrafine powder in a jet mill. 10 g of ultrafine powder xanthan gum with a particle size range of 2 to 5 μm was mixed with 0.5 g KH570 and 2000 g anhydrous ethanol, and dispersed in an ultrasonic disperser for 30 min to obtain a dispersion.

[0069] (3) Preparing a modified tackifier: adding 400 g of rice husk ash to the dispersion prepared in step (2), and ultrasonically dispersing the mixture for 15 min to obtain a mixture. After standing for 24 h, the mixture was spray-dried using a nitrogen closed-loop spray dryer to obtain a modified tackifier.

[0070] (4) 75 g of mineral admixture, 15 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0071] Example 4

[0072] A concrete viscosity modifying material, the preparation steps are as follows:

[0073] (1) Preparation of rice husk ash: Wash the rice husk with water to remove the dust on the surface, dry it at 105 °C for 2 h, and then use a planetary ball mill to mill it for 40 min. Pass the milled rice husk powder through a 100-mesh square hole sieve. Take the sieve and soak it in a 60 °C, 2 mol / L nitric acid solution for 2 h. Filter out the rice husk powder with a 200-mesh sieve and wash it repeatedly until the water washing liquid is neutral. Dry the rice husk powder in a 105 °C oven for 2 h and then place it in a muffle furnace. First, heat it to 500 °C at a heating rate of 10 °C / min and keep it at this temperature for 2 h. Then, heat it to 600 °C at a heating rate of 5 °C / min and keep it at this temperature for 2 h. Then, naturally cool it to room temperature. The calcined product is rice husk ash.

[0074] (2) Pretreatment of bio-gum: Xanthan gum was crushed into ultrafine powder in a jet mill. 10 g of ultrafine powder xanthan gum with a particle size range of 2 to 5 μm was mixed with 0.5 g KH570 and 2000 g anhydrous ethanol, and dispersed in an ultrasonic disperser for 30 min to obtain a dispersion.

[0075] (3) Preparing a modified tackifier: adding 200 g of rice husk ash to the dispersion prepared in step (2), and performing ultrasonic dispersion for 15 min to obtain a mixture. After standing for 24 h, the mixture was spray-dried using a nitrogen closed-loop spray dryer to obtain a modified tackifier.

[0076] (4) 65 g of mineral admixture, 25 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0077] Comparative Example 1

[0078] A concrete viscosity modifying material, the preparation steps are as follows:

[0079] (1) Preparation of rice husk ash: Wash the rice husk with water to remove the dust on the surface, dry it at 105 °C for 2 h, and then use a planetary ball mill to mill it for 40 min. Pass the milled rice husk powder through a 100-mesh square hole sieve. Take the sieve and soak it in a 60 °C, 2 mol / L nitric acid solution for 2 h. Filter out the rice husk powder with a 200-mesh sieve and wash it repeatedly until the water washing liquid is neutral. Dry the rice husk powder in a 105 °C oven for 2 h and then place it in a muffle furnace. First, heat it to 500 °C at a heating rate of 10 °C / min and keep it at this temperature for 2 h. Then, heat it to 600 °C at a heating rate of 5 °C / min and keep it at this temperature for 2 h. Then, naturally cool it to room temperature. The calcined product is rice husk ash.

[0080] (2) Bio-gum pretreatment: Place xanthan gum in a jet mill and grind it into ultrafine powder;

[0081] (3) Preparation of modified thickener: 10 g of ultrafine powder xanthan gum with a particle size range of 2 to 5 μm was mixed with 0.5 g KH570 and 200 g rice husk ash to obtain a modified thickener;

[0082] (4) 75 g of mineral admixture, 15 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0083] Comparative Example 2

[0084] A concrete viscosity modifying material, the preparation steps are as follows:

[0085] (1) Pretreatment of bio-gum: Xanthan gum was crushed into ultrafine powder in a jet mill. 10 g of ultrafine powder xanthan gum with a particle size range of 2 to 5 μm was mixed with 0.5 g KH570 and 2000 g anhydrous ethanol, and dispersed in an ultrasonic disperser for 30 min to obtain a dispersion.

[0086] (2) Preparing a modified tackifier: adding 200 g of the mineral admixture to the dispersion prepared in step (2), ultrasonically dispersing the mixture for 15 min to obtain a mixture, standing the mixture for 24 h, and then spray drying the mixture using a nitrogen closed-loop spray dryer to obtain a modified tackifier;

[0087] (3) 75 g of mineral admixture, 15 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0088] Comparative Example 3

[0089] A concrete viscosity modifying material, the preparation steps are as follows:

[0090] (1) Preparation of rice husk ash: Wash the rice husk with water to remove the dust on the surface, dry it at 105 °C for 2 h, and then use a planetary ball mill to mill it for 40 min. Pass the milled rice husk powder through a 100-mesh square hole sieve. Take the sieve and soak it in a 60 °C, 2 mol / L nitric acid solution for 2 h. Filter out the rice husk powder with a 200-mesh sieve and wash it repeatedly until the water washing liquid is neutral. Dry the rice husk powder in a 105 °C oven for 2 h and then place it in a muffle furnace. First, heat it to 500 °C at a heating rate of 10 °C / min and keep it at this temperature for 2 h. Then, heat it to 600 °C at a heating rate of 5 °C / min and keep it at this temperature for 2 h. Then, naturally cool it to room temperature. The calcined product is rice husk ash.

[0091] (2) Grind 400 viscosity hydroxymethyl propyl cellulose into ultrafine powder in a jet mill, take 10 g of 400 viscosity hydroxymethyl propyl cellulose with a particle size range of 2 to 5 μm, mix it with 0.5 g KH570 and 2000 g of anhydrous ethanol, and disperse it in an ultrasonic disperser for 30 min to obtain a dispersion;

[0092] (3) adding 200 g of rice husk ash to the dispersion prepared in step (2), performing ultrasonic dispersion for 15 min, standing for 24 h, and then spray drying the mixture using a nitrogen closed-loop spray dryer to obtain a modified tackifier;

[0093] (4) 75 g of mineral admixture, 15 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0094] Comparative Example 4

[0095] A concrete viscosity modifying material, the preparation steps are as follows:

[0096] (1) Preparation of rice husk ash: Wash the rice husk with water to remove the dust on the surface, dry it at 105 °C for 2 h, and then use a planetary ball mill to mill it for 40 min. Pass the milled rice husk powder through a 100-mesh square hole sieve. Take the sieve and soak it in a 60 °C, 2 mol / L nitric acid solution for 2 h. Filter out the rice husk powder with a 200-mesh sieve and wash it repeatedly until the water washing liquid is neutral. Dry the rice husk powder in a 105 °C oven for 2 h and then place it in a muffle furnace. Heat it to 800 °C at a heating rate of 20 °C / min, keep it at this temperature for 4 h, and cool it naturally to room temperature. The calcined product is rice husk ash.

[0097] (2) Pretreatment of bio-gum: Grind xanthan gum into ultrafine powder in a jet mill, take 10 g of ultrafine powder xanthan gum with a particle size range of 2 to 5 μm, mix it with 0.5 g KH570 and 2000 g anhydrous ethanol, and disperse it in an ultrasonic disperser for 30 min to obtain a dispersion;

[0098] (3) Preparing a modified tackifier: adding 200 g of rice husk ash to the dispersion prepared in step (2), ultrasonically dispersing for 15 min, standing for 24 h, and then spray drying the mixture using a nitrogen closed-loop spray dryer to obtain a modified tackifier;

[0099] (4) 75 g of mineral admixture, 15 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0100] Comparative Example 5

[0101] A concrete viscosity modifying material, the preparation steps are as follows:

[0102] (1) Preparation of rice husk ash: Wash the rice husk with water to remove the dust on the surface, dry it at 105 °C for 2 h, and then use a planetary ball mill to mill it for 40 min. Pass the milled rice husk powder through a 100-mesh square hole sieve. Take the sieve and soak it in a 60 °C, 2 mol / L nitric acid solution for 2 h. Filter out the rice husk powder with a 200-mesh sieve and wash it repeatedly until the water washing liquid is neutral. Dry the rice husk powder in a 105 °C oven for 2 h and then place it in a muffle furnace. First, heat it to 500 °C at a heating rate of 10 °C / min and keep it at this temperature for 2 h. Then, heat it to 600 °C at a heating rate of 5 °C / min and keep it at this temperature for 2 h. Then, naturally cool it to room temperature. The calcined product is rice husk ash.

[0103] (2) Bio-gum pretreatment: 10 g of ordinary xanthan gum (particle size between 75 and 180 μm) was mixed with 0.5 g of KH570 and 2000 g of anhydrous ethanol, and dispersed with an ultrasonic disperser for 30 min to obtain a dispersion;

[0104] (3) Preparing a modified tackifier: adding 200 g of rice husk ash to the dispersion prepared in step (2), ultrasonically dispersing for 15 min, standing for 24 h, and then spray drying the mixture using a nitrogen closed-loop spray dryer to obtain a modified tackifier;

[0105] (4) 75 g of mineral admixture, 15 g of modified viscosity enhancer, 5 g of fumed silica, and 5 g of cellulose ether were mixed evenly to obtain a concrete viscosity modifying material.

[0106] Comparative Example 6

[0107] A concrete viscosity modifying material, the preparation steps are as follows:

[0108] 90 g of mineral admixture, 5 g of fumed silica, and 5 g of cellulose ether were uniformly mixed to obtain a concrete viscosity modifying material.

[0109] The viscosity modified materials prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were subjected to performance tests, wherein the viscosity ratio, water consumption sensitivity, and expansion difference were tested according to TB / T 3275-2018 "Railway Concrete", and the normal pressure water bleeding rate and compressive strength ratio were tested according to GB 8076. The test results are shown in Table 1.

[0110] Table 1: Viscosity modified material performance test results

[0111]

[0112] The viscosity-modifying materials prepared in Examples 1 to 4 all meet the standard requirements. Compared with Example 1, the dosage of xanthan gum and silane coupling agent in Example 2 is reduced, and its viscosity ratio, water consumption sensitivity and expansion difference are all reduced, and the compressive strength ratio is slightly improved; in Example 3, the dosage of rice ash is reduced, and the dosage of xanthan gum in the modified tackifier is increased; in Example 4, the proportion of the modified tackifier in the viscosity-modifying material is increased, which all leads to an increase in the viscosity ratio, water consumption sensitivity and expansion difference, and a slight decrease in the compressive strength ratio.

[0113] Compared with Example 1, in Comparative Example 1, the modified viscosity enhancer was not subjected to the step (3) of using rice ash to adsorb and slowly release the ultrafine powder xanthan gum; in Comparative Example 2, an equal amount of active admixture was used to replace rice husk ash; in Comparative Example 4, the heating rate during calcination of rice husk was too fast and the calcination temperature was too high; and in Comparative Example 5, the xanthan gum was not subjected to ultrafine grinding. In the above comparative examples, the xanthan gum was either not adsorbed or the adsorption effect of rice husk ash on xanthan gum was seriously reduced, making it difficult to achieve the purpose of sustained release of xanthan gum, resulting in an increase in the viscosity ratio and a larger difference in the degree of expansion; in Comparative Example 3, cellulose was used to replace xanthan gum, and in Comparative Example 6, no modified viscosity enhancer was added, resulting in the viscosity ratio, water consumption sensitivity and normal pressure water bleeding rate not meeting the requirements of the viscosity modified material in standard TB / T 3275.

[0114] Application Testing

[0115] The viscosity modified materials prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were applied to self-compacting concrete (the mix ratio is shown in Table 2 below), and the performance of the self-compacting concrete was tested. For Application Examples 1 to 4 and Comparative Application Examples 1 to 6, the slump expansion, expansion time T500, J-ring obstacle height difference, and L-type instrument filling ratio were tested according to Appendix H of Standard TB 10424-2018 "Railway Concrete Construction Quality Acceptance Standard", the water seepage rate was tested according to GB 50080-2016 "Ordinary Concrete Mixture Performance Test Method Standard", and the compressive strength was tested according to GB 50081-2019 "Ordinary Concrete Mechanical Properties Test Method Standard", and the test results are shown in Table 3.

[0116] Table 2: Mix proportion of self-compacting concrete (kg / m 3 )

[0117]

[0118] Table 3: Self-compacting concrete performance test results

[0119]

[0120] As can be seen from Table 3, the self-compacting concrete prepared by using the viscosity modifying material of the present invention, i.e., application examples 1 to 4, all performance indicators meet the requirements of the standard QCR 596-2017 "Self-compacting concrete for high-speed railway slab ballastless track". Compared with application examples 1, 2, 4, and 5, the viscosity ratio of the viscosity modifying material used is too large and the fluidity is poor, resulting in low slump expansion and expansion time T 500The self-compacting concrete system is too viscous and has poor fluidity. In contrast, the viscosity-modified materials in Application Examples 3 and 6 do not use bio-glue, and the self-compacting concrete has bleeding, a large difference in the expansion of the J-ring barrier, a low filling ratio of the L-type instrument, a large bleeding rate, and reduced compressive and flexural strengths.

[0121] In summary, the present invention adopts bio-glue, rice husk ash and silane coupling agent to prepare modified viscosity enhancer, and then compound mineral admixtures, inorganic thixotropic agents and organic thixotropic agents with high-quality thixotropic properties. The final prepared concrete viscosity modifying material has excellent thixotropy, which can effectively solve the problems of mortar and concrete bleeding, segregation, etc. while improving the working performance of concrete, and has great application value.

[0122] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A concrete viscosity modifying material, It is characterized in that The composition includes the following components in percentage by mass: 65% to 85% of mineral admixture, 15% to 35% of modified viscosity enhancer, 1% to 5% of inorganic thixotropic agent, and 1% to 5% of organic thixotropic agent; Wherein, the preparation method of the modified tackifier comprises the following steps: (1) preparing rice husk powder from rice husk, soaking the rice husk powder in acid solution, sieving, washing, drying, and then calcining to obtain rice husk ash; crushing the bio-glue into ultrafine powder, and uniformly dispersing the ultrafine powder bio-glue and silane coupling agent in anhydrous ethanol to obtain a dispersion; (2) Add rice husk ash to the dispersion and disperse it evenly to obtain a mixture. After the mixture is sealed and allowed to stand, it is spray-dried to obtain a modified thickener.

2. A concrete viscosity modifying material according to claim 1, It is characterized in that The acid solution is a 2-4 mol / L nitric acid solution at 60-80°C.

3. A concrete viscosity modifying material according to claim 1, It is characterized in that The calcination is a two-stage calcination, wherein the heating rate of the first stage calcination is 10-20°C / min, the temperature is raised to 500°C and calcined for 2-3 h, and the heating rate of the second stage calcination is 5-10°C / min, the temperature is raised to 600°C and calcined for 1-2 h.

4. A concrete viscosity modifying material according to claim 1, It is characterized in that The biological gum is one or more of xanthan gum, Brunei gum, guar gum, alginate and carrageenan.

5. A concrete viscosity modifying material according to claim 1, It is characterized in that The method of crushing the bio-glue is: crushing the bio-glue with a jet mill; the particle size of the ultrafine powder bio-glue is ≤10 μm, and the average particle size is 2~5 μm.

6. A concrete viscosity modifying material according to claim 1, It is characterized in that The weight ratio of the bio-glue to anhydrous ethanol is (0.1-0.5):100; the weight ratio of the silane coupling agent to the bio-glue is (1-5):100; and the weight ratio of the rice husk ash to the dispersion is (10-20):

100.

7. A concrete viscosity modifying material according to claim 1, It is characterized in that The mineral admixture is a compound of mineral powder, fly ash and metakaolin, and the weight ratio of the mineral powder, fly ash and metakaolin is (30 ~ 50): (20 ~ 40): (30 ~ 50).

8. A concrete viscosity modifying material according to claim 1, It is characterized in that The organic thixotropic agent is one or more of cellulose ether, starch ether and polyacrylamide.

9. A concrete viscosity modifying material according to claim 1, It is characterized in that The inorganic thixotropic agent is fumed silica, and the specific surface area of ​​the fumed silica is ≥ 200 m 2 / g, bulk density ≤ 50 g / L, SiO 2 The content is ≥ 99.8%.

10. A method for preparing a concrete viscosity modifier according to any one of claims 1 to 9, It is characterized in that include: The mineral admixture, the modified viscosity enhancer, the inorganic thixotropic agent and the organic thixotropic agent are uniformly mixed to obtain a viscosity modified material.

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