High-slump-preserving super high performance concrete and preparation method thereof

Abstract

The application discloses high-slump super high performance concrete and a preparation method thereof, and the concrete comprises the following components in percentage by mass: cement 27-38%, silica flour 8.5-9.5%, carborundum 39-49%, steel fiber 5.5-8%, water reducing agent 2-4%, and viscosity reducing slump retaining agent 1-5%. The viscosity reducing slump retaining agent is a mixture of steady agent and mixed dispersion of molybdate / tungstate. The preparation method comprises the following steps: (1) preparing the mixed dispersion of molybdate / tungstate; (2) weighing and stirring cement, silica flour and carborundum according to the proportion to obtain premix; (3) mixing and uniformly stirring water reducing agent, the mixed dispersion of molybdate / tungstate, steady agent and water in a container to obtain liquid mixture; and (4) pouring the liquid mixture into the premix, uniformly stirring, adding steel fiber and continuously stirring to obtain high-slump super high performance concrete slurry. The application can improve the slump and retention of concrete mixture and reduce the viscosity of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of concrete, specifically to a kind of high slump ultra high performance concrete (UHPC) and its preparation method, applied in building structure, road, bridge and other fields. BACKGROUND

[0002] At present, as a new type of high performance concrete, ultra high performance concrete (UHPC) has been widely used in building, road, bridge and other fields. However, the traditional UHPC has short setting time, easy to solidify, poor retention, high viscosity, poor construction and other problems, which seriously limits its application range.

[0003] To solve these problems, a new type of UHPC high performance concrete is needed, which can have long working performance and also ensure construction performance without affecting strength. Therefore, it is of great significance to develop a kind of ultra high performance concrete (UHPC) with high slump property to expand its application range. SUMMARY

[0004] The purpose of the present application is to provide a kind of high slump ultra high performance concrete, which can keep the concrete 2h extension degree without loss, can have long working performance and also ensure construction performance without affecting its strength.

[0005] Another purpose of the present application is to provide a preparation method of the high slump ultra high performance concrete.

[0006] To achieve the above-mentioned purposes, the technical solution adopted by the present application is: a kind of high slump ultra high performance concrete, by mass percentage, including the following components: cement 27-38%, silica fume 8.5-9.5%, corundum 39-49%, steel fiber 5.5-8%, water reducing agent 2-4%, viscosity reducing slump agent 1-5%;

[0007] The viscosity reducing slump agent is a mixture of steady agent and sulfomolybdate / sulfotungstate mixed dispersion.

[0008] In the above technical solution, the mass ratio of steady agent to sulfomolybdate / sulfotungstate mixed dispersion is (3-3.5) :(1.5-2).

[0009] In the above technical solution, the sulfomolybdate / sulfotungstate mixed dispersion is prepared by the following method:

[0010] S1. Add water, nano MoS2 and nano WS2 into a container, and disperse at high speed to a uniform slurry; the mass ratio of nano MoS2 and nano WS2 is 1 :(0.2-0.3);

[0011] S2. Ultrasonic dispersion of the slurry obtained in S1;

[0012] S3. The slurry obtained in S2 is heated to the reaction temperature under reflux with stirring, and silica sol is added at a uniform rate. After the addition is completed, 1-2% of the total mass of heptadecafluorodecyltrimethoxysilane is added, and the reaction is continued under reflux with stirring.

[0013] S4. The slurry obtained in S3 is stopped heating under reflux with stirring, and is naturally cooled to room temperature. The stirring is stopped to obtain a mixed dispersion of molybdate / tungstate.

[0014] In S3, the reaction temperature is 45-50℃.

[0015] In the above technical solution, the water requirement of the silica ash is ≤110%; and the grit size of the corundum is ≤1.18mm.

[0016] The water reducing agent is a polycarboxylic acid high-performance water reducing agent.

[0017] In the above technical solution, the stabilizing agent is disclosed in Chinese invention patent application CN113336466A. The stabilizing agent can be adsorbed on the surface of cement, stabilize the surface activity of cement hydration products, and keep the distance between cement particles stable. The mixed dispersion of molybdate / tungstate is prepared from MoS2 / WS2, which has a two-dimensional structure similar to graphene, and can be dispersed between clays in concrete sand materials to improve the lubricity between clay particles and reduce the viscosity of concrete. Therefore, the viscosity reducing and slump retaining agent can improve the slump and retention of concrete mixture, and reduce the viscosity of the system. At the same time, molybdate / tungstate can help the stabilizing agent to rapidly penetrate the surface of clay and be adsorbed on the surface of clay, and has a good effect on the viscosity reduction and stability of concrete.

[0018] However, molybdate / tungstate is a powder with very high fineness, which can form clumps when directly added to concrete, reducing the use effect. To solve this problem, the molybdate / tungstate, silica sol and heptadecafluorodecyltrimethoxysilane are first mixed and dispersed at high speed to prepare a mixed solution, which is then compounded with the stabilizing agent for use.

[0019] To achieve another inventive purpose of the present application, a preparation method of high-slump ultra-high-performance concrete is provided, which comprises the following steps:

[0020] (1) Preparation of a mixed dispersion of molybdate / tungstate:

[0021] S1. adding water, nano-sized MoS2 and nano-sized WS2 in a container, and high-speed dispersing to a uniform slurry; the mass ratio of the nano-sized MoS2 and the nano-sized WS2 is 1:(0.2-0.3);

[0022] S2. ultrasonic dispersing the slurry obtained in S1;

[0023] S3. refluxing and heating the slurry obtained in S2 to a reaction temperature under stirring, adding silica sol at a uniform speed, adding 1-2% of heptadecafluorodecyltrimethoxysilane based on the total mass after the addition is completed, and continuing to reflux and heat under stirring; the solid content of the silica sol is 30%, and the addition amount is 4-5 times the total mass of the nano-sized MoS2 and the nano-sized WS2;

[0024] S4. stopping heating the slurry obtained in S3 under stirring and refluxing, naturally cooling to room temperature, stopping stirring, and obtaining a mixed dispersion of molybdate / tungstate;

[0025] (2) weighing and stirring cement, silica fume and corundum according to the proportion to obtain a premix;

[0026] (3) mixing water-reducing agent, the mixed dispersion of molybdate / tungstate, stabilizing agent and water in a container, and stirring uniformly to obtain a liquid mixture;

[0027] (4) pouring the liquid mixture into the premix, stirring uniformly, adding steel fibers and continuing to stir to obtain a high-slump super-high-performance concrete slurry.

[0028] Thanks to the above technical solution, the present application has the following advantages compared with the prior art:

[0029] 1. The stabilizing agent and the mixed dispersion of molybdate / tungstate are used in combination to form a viscosity-reducing slump-retaining agent, which can improve the slump and retention of the concrete mixture and reduce the viscosity of the system. At the same time, the molybdate / tungstate can help the stabilizing agent to rapidly penetrate the clay surface and be adsorbed on the clay surface, which has a good effect on the viscosity reduction and stability of the concrete.

[0030] 2. The mixed solution is prepared by high-speed mixing and dispersing the molybdate / tungstate, silica sol and heptadecafluorodecyltrimethoxysilane, and then the stabilizing agent is compounded, which solves the problem that the molybdate / tungstate directly added into the concrete forms a clump. DETAILED DESCRIPTION

[0031] The present application is further described below in combination with examples: Example 1

[0032] A high slump loss UHPC ultra high performance concrete is prepared from the following raw materials in percentage by mass: cement 35%; silica fume 9%; carborundum 45%; steel fiber 6%; water reducing agent 3%; viscosity reducing slump loss agent 2%. The water-binder ratio is 17%.

[0033] The preparation method of the embodiment is as follows:

[0034] Step 1: Preparation of a laminar stacked sulfomolybdate / sulfotungstate mixed dispersion

[0035] S1. A measured amount of water and nanoscale MoS2 / WS2 is added to a container and dispersed at high speed to a uniform slurry, with a stirring speed of 1200-1400 rpm and a dispersion time of 30-40 minutes; wherein the MoS2 and WS2 of 50-80 nm are mixed in a mass ratio of 1:0.2-0.3;

[0036] S2. The slurry obtained in S1 is subjected to ultrasonic dispersion for 30-40 minutes;

[0037] S3. The slurry obtained in S2 is heated to 45-50℃ under reflux with stirring, with a stirring speed of 400-600 rpm, and 30% solid content silica sol is added at a uniform speed, with a dropwise adding time controlled in 20-25 minutes, and 1-2% heptadecafluorodecyltrimethoxysilane is added after the addition is completed, and the reaction is continued under reflux with stirring for 50-60 minutes;

[0038] S4. The slurry obtained in S3 is stopped heating under stirring reflux, with a stirring speed of 300-400 rpm, and naturally cooled to room temperature, and the stirring is stopped to obtain a sulfomolybdate / sulfotungstate / silica sol mixed dispersion.

[0039] Step 2: The cement, silica fume and carborundum are weighed according to the proportion and poured into a double-shaft forced mixer for stirring for 1-2 minutes to obtain a premix.

[0040] Step 3: The water reducing agent, viscosity reducing slump loss agent and water are weighed according to the proportion and poured into a beaker, and stirred uniformly with a glass rod to obtain a liquid mixture.

[0041] Step 4: The liquid mixture is poured into the premix and stirred for 4 minutes, and the steel fiber weighed according to the proportion is added and stirred for 4 minutes to obtain a high slump loss UHPC ultra high performance concrete slurry. Example 2

[0042] A high slump loss UHPC ultra high performance concrete is prepared from the following raw materials in percentage by mass: cement 35%; silica fume 9%; carborundum 44%; steel fiber 6%; water reducing agent 3%; viscosity reducing slump loss agent 2%; and the high slump loss UHPC ultra high performance concrete slurry is prepared according to the preparation method of Example 1 with a water-binder ratio of 17%. Example 3

[0043] A high-slump UHPC ultra-high performance concrete is prepared from the following raw materials in mass percentage: cement 35%; silica fume 9%; corundum 43%; steel fiber 6%; water reducing agent 3%; viscosity reducing slump retaining agent 3%; and the high-slump UHPC ultra-high performance concrete slurry is prepared according to the preparation method of Example 1 with a water-binder ratio of 17%.

[0044] Control group 1:

[0045] The high-slump UHPC ultra-high performance concrete is prepared from the following raw materials in mass percentage: cement 35%; silica fume 9%; corundum 44%; steel fiber 6%; water reducing agent 3%, and the water-binder ratio is 17%. (No viscosity reducing slump retaining agent)

[0046] Control group 2:

[0047] The high-slump UHPC ultra-high performance concrete is prepared from the following raw materials in mass percentage: cement 35%; silica fume 9%; corundum 44%; steel fiber 6%; water reducing agent 3%, and the water-binder ratio is 19%. (No viscosity reducing slump retaining agent)

[0048] Control group 3:

[0049] The high-slump UHPC ultra-high performance concrete is prepared from the following raw materials in mass percentage: cement 35%; silica fume 9%; corundum 44%; steel fiber 6%; water reducing agent 3%, and the water-binder ratio is 19%. (Only the stabilizing agent is added, and no sulfomolybdate / sulfotungstate mixed dispersion is added)

[0050] Control group 4:

[0051] The high-slump UHPC ultra-high performance concrete is prepared from the following raw materials in mass percentage: cement 35%; silica fume 9%; corundum 44%; steel fiber 6%; water reducing agent 3%, and the water-binder ratio is 19%. (Only the sulfomolybdate / sulfotungstate mixed dispersion is added, and no stabilizing agent is added)

[0052] The test refers to JGJ / T 70-2009 "Standard for Testing Methods of Basic Properties of Building Mortar", GB / T 50080-2016 "Standard for Testing Methods of Properties of Ordinary Concrete Mixture", and the test results are shown in Table 1 below:

[0053] Table 1

[0054]

[0055] It can be seen from the results of the above examples and comparative examples that, with the increase of the amount of the viscosity reducing slump retaining agent, the initial expansion degree of the concrete becomes larger, the 1h expansion degree is basically unchanged, and the 2h expansion degree becomes larger. It can be seen from examples 2 and comparative examples 1 and 2 that, with the same water-binder ratio, the expansion degree of example 2 with the viscosity reducing slump retaining agent is obviously higher than that of comparative examples 1 and 2 without the viscosity reducing slump retaining agent, the state of comparative examples 2 has no change after two hours, and the addition of the viscosity reducing slump retaining agent can improve the 28-day strength of the concrete. The effect of the viscosity reducing slump retaining agent used alone is obviously not as good as that of the viscosity reducing slump retaining agent used in combination. Comparative example 3 is a single use of a stabilizing agent, and comparative example 4 is a single use of a mixture of a molybdenum sulfide / tungsten sulfide dispersion.

[0056] In summary, the present application provides a high slump retaining UHPC super high performance concrete. The viscosity reducing slump retaining agent can obviously improve the 1h and 2h expansion degrees of the concrete and maintain the slight increase of the strength of the concrete. The present application has the advantages of simple and convenient production, stable quality and high application value.

Claims

1. A high slump super high performance concrete, characterized by, According to the mass percentage, the cement is 27-38%, the silica ash is 8.5-9.5%, the carborundum is 39-49%, the steel fiber is 5.5-8%, the water reducing agent is 2-4%, and the viscosity reducing and slump retaining agent is 1-5%; The viscosity reducing and slump retaining agent is a mixture of a steady agent and a mixed dispersion; The mixed dispersion is prepared by the following method: S1. adding water, nano-sized MoS2 and nano-sized WS2 in a container, and high-speed dispersing to a uniform slurry; the mass ratio of the nano-sized MoS2 and the nano-sized WS2 is 1:(0.2-0.3); S2. ultrasonic dispersing the slurry obtained in S1; S3. refluxing and heating the slurry obtained in S2 to a reaction temperature under stirring, adding silica sol at a uniform speed, adding 1-2% of heptadecafluorodecyltrimethoxysilane based on the total mass after the addition is completed, and continuing to reflux and heat under stirring; the solid content of the silica sol is 30%, and the addition amount is 4-5 times the total mass of the nano-sized MoS2 and the nano-sized WS2; S4. stopping heating the slurry obtained in S3 under stirring and refluxing, naturally cooling to room temperature, stopping stirring, and obtaining the mixed dispersion.

2. The high slump super high performance concrete according to claim 1, wherein: According to the mass, the steady agent: the mixed dispersion=(3-3.5):(1.5-2).

3. The high slump super high performance concrete of claim 1, wherein: The reaction temperature is 45-50℃.

4. The high slump super high performance concrete of claim 1, wherein: The water demand ratio of the silica ash is ≤110%, and the particle size of the carborundum is ≤1.18mm.

5. The high slump super high performance concrete of claim 1, wherein: The water reducing agent is a polycarboxylic acid high-performance water reducing agent.

6. The method of making the high slump super high performance concrete of claim 1, wherein, The method comprises the following steps: (1) preparing a mixed dispersion: S1. adding water, nano-sized MoS2 and nano-sized WS2 in a container, and high-speed dispersing to a uniform slurry; the mass ratio of the nano-sized MoS2 and the nano-sized WS2 is 1:(0.2-0.3); S2. ultrasonic dispersing the slurry obtained in S1; S3. refluxing and heating the slurry obtained in S2 to a reaction temperature under stirring, adding silica sol at a uniform speed, adding 1-2% of heptadecafluorodecyltrimethoxysilane based on the total mass after the addition is completed, and continuing to reflux and heat under stirring; the solid content of the silica sol is 30%, and the addition amount is 4-5 times the total mass of the nano-sized MoS2 and the nano-sized WS2; S4. stopping heating the slurry obtained in S3 under stirring and refluxing, naturally cooling to room temperature, stopping stirring, and obtaining the mixed dispersion; (2) weighing and stirring the cement, the silica ash and the carborundum according to the proportions to obtain a premix; (3) mixing the water reducing agent, the mixed dispersion obtained in step (1), the steady agent and water in a container, and stirring uniformly to obtain a liquid mixture; (4) pouring the liquid mixture into the premix, stirring uniformly, adding the steel fiber and continuing to stir to obtain a high-slump super-high-performance concrete slurry.

7. The method of preparing high slump super high performance concrete according to claim 6, characterized in that: In S3, the reaction temperature is 45-50℃.

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