Low-shrinkage anti-cracking ultra-high performance concrete, and preparation method and application thereof

Abstract

This invention provides a low-shrinkage, crack-resistant ultra-high performance concrete, its preparation method, and its application, comprising the following raw materials in parts by weight: 33-50 parts silicate cement, 19-28 parts slag powder, 20-38 parts fly ash, 12-28 parts silica fume, 22-40 parts crushed stone, 18-36 parts modified fine aggregate, 15-26 parts high-performance expansive agent, 12-28 parts crack-resistant admixture, 17-29 parts retarder, 2-8 parts water-reducing agent, and 0-6 parts ice chips; the ultra-high performance concrete obtained by this invention... The concrete exhibits low shrinkage and crack resistance. By rationally selecting and scientifically proportioning raw materials, their properties are synergistically utilized, resulting in low shrinkage, strong mechanical properties, and resistance to cracking. The resulting concrete has a 7-day flexural strength of 39-43 MPa, a 28-day flexural strength of 35-39 MPa, a 7-day compressive strength of 201-206 MPa, a 28-day compressive strength of 180-185 MPa, no cracks, a shrinkage rate of 0.10-0.15‰, and a fracture energy of 3.8-4.2 × 10⁻⁶ MPa. 4 J / m 2 It has low shrinkage while also having high mechanical strength, good durability and load-bearing capacity, and its application in the preparation of fire evacuation platforms has good prospects.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a low-shrinkage, crack-resistant, ultra-high performance concrete, its preparation method, and its application. Background Technology

[0002] With population growth and urbanization, urban rail transit construction is becoming increasingly important. Elevated subway bridges are a crucial component of urban rail transit construction. Evacuation platforms are essential components of elevated bridges, effectively improving passenger safety and protecting the bridge structure. Therefore, the construction technology of concrete evacuation platforms for elevated subway bridges is extremely important. Evacuation platforms are components on elevated bridges, located near the entrances and exits of subway stations, used for the emergency evacuation of passengers. The structural characteristics of evacuation platforms include high load-bearing capacity, capable of withstanding large gatherings and evacuations of people, and the use of ultra-high-performance concrete, which possesses excellent durability and load-bearing capacity.

[0003] Ultra-high performance concrete, also known as reactive powder concrete (RPC), refers to concrete with a cubic compressive strength greater than 100 MPa. However, due to its high content of cementitious materials, low water-cement ratio, and high amount of admixtures, coupled with the ultra-reactive material silica fume, ultra-high performance concrete has high heat of hydration, severe shrinkage cracking, and high viscosity, which has led to various problems in its application. Summary of the Invention

[0004] In view of this, the present invention proposes a low-shrinkage, crack-resistant, ultra-high performance concrete and its application to solve the above problems.

[0005] The technical solution of this invention is achieved as follows: A low-shrinkage, crack-resistant, ultra-high performance concrete comprising the following raw materials by weight: 33-50 parts silicate cement, 19-28 parts slag powder, 20-38 parts fly ash, 12-28 parts silica fume, 22-40 parts crushed stone, 18-36 parts modified fine aggregate, 15-26 parts high-performance expansive agent, 12-28 parts crack-resistant admixture, 17-29 parts retarder, 2-8 parts water-reducing agent, and 0-6 parts ice chips; wherein the high-performance expansive agent is a CAL fiber composite quaternary expansive agent with a mass ratio of (10-20):(18-22):(2-10), and lightly calcined magnesium oxide. The retarder consists of sodium tripolyphosphate, sodium gluconate, and sodium carboxymethyl cellulose in a mass ratio of (7.6-8.8):(1.0-3.8):(5.6-10.2). The main characteristic of the high-performance expansive agent is that it can resist cracking and prevent seepage after being added to concrete. Its expansion properties can compensate for shrinkage during the hardening process of concrete. The retarder's molecular structure has a large number of hydroxyl and carboxyl groups, which helps to slow down the pouring speed, facilitate heat dissipation, regulate the concrete setting time, reduce slump, adjust workability, and adjust the compatibility with cement and water-reducing agents. Adding ice chips reduces the temperature generated during concrete mixing and reduces the heat of hydration.

[0006] Preferably, a low-shrinkage, crack-resistant, ultra-high performance concrete comprises the following raw materials in parts by weight: 42 parts silicate cement, 25 parts slag powder, 29 parts fly ash, 19 parts silica fume, 31 parts crushed stone, 28 parts modified fine aggregate, 20 parts high-performance expansive agent, 18 parts crack-resistant admixture, 22 parts retarder, 6 parts water-reducing agent, and 3 parts ice chips.

[0007] Preferably, the crushed stone is selected from natural rocks, pebbles or mine waste rock that are mechanically crushed and screened, and the rock particles have a particle size greater than 5 mm.

[0008] Preferably, the modified fine aggregate is prepared by mixing manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of (3.2-5.8):(1.3-3.9):(8.6-9.5), grinding the mixture in a mixer for 1-3 hours, adding 5-8% silane coupling agent by mass, ultrasonically mixing for 5-10 minutes, washing, and drying to obtain modified fine aggregate with a particle size of less than 4.75 mm. The modified fine aggregate can effectively improve the flexural and compressive strength of concrete while maintaining good frost resistance.

[0009] Preferably, the crack-resistant additive is any one of lauryl ketone, dialkyl sulfosuccinate, or SY-T type high-efficiency special expandable fiber crack-resistant agent.

[0010] Preferably, the water-reducing agent is any one of acrylic polycarboxylic acid, sodium lauryl sulfate, and calcium lignosulfonate.

[0011] Furthermore, a method for preparing low-shrinkage, crack-resistant ultra-high performance concrete includes the following steps:

[0012] Step S1: Mix silicate cement, slag powder, fly ash and silica fume to obtain a mixture, then add water and put it into a concrete mixer for mixing. The mixing speed is 300-500 rpm and the mixing time is 15-50 min to obtain the concrete precursor.

[0013] Step S2: Add crushed stone and modified fine aggregate to the concrete precursor prepared in S1 and mix. While mixing, circulate cold water or cold air is introduced to obtain concrete mix. Circulating cold water or cold air is introduced to accelerate heat dissipation and make the temperature distribution more uniform. At the same time, it is easier to vibrate and compact to improve the elastic modulus.

[0014] Step S3: Add high-performance expansion agent, crack-resistant admixture, retarder, water-reducing agent and ice chips to the above-mentioned initial set mixture, stir at high speed for 15-60 minutes at a stirring speed of 2000-2500 rpm to obtain the initial set mixture, pour it into the mold, compact it, water it for curing, demold it, and cure it to obtain high-performance concrete.

[0015] Preferably, in step S1, the mass-volume ratio (g / mL) of the mixture and water is 39-52:5-10.

[0016] Preferably, the flow rate of the circulating cold water in step S2 is 2-10 m³ / h. 3 / h, the injection rate is 1 / 8-1 / 5 of the concrete precursor volume; the cold air injection flow rate is 12-28mL / min, and the injection volume is 200-800mL.

[0017] Application of a low-shrinkage, crack-resistant, ultra-high performance concrete in the preparation of fire evacuation platforms.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] The ultra-high performance concrete prepared by this invention exhibits low shrinkage and crack resistance. The raw materials are rationally selected and scientifically proportioned to synergistically enhance their performance, resulting in low shrinkage, strong mechanical properties, and resistance to cracking. The high-performance expansive agent and retarder, after being proportionally adjusted and incorporated into the concrete, provide crack resistance and impermeability. Their expansive properties compensate for shrinkage during the concrete hardening process. The retarder's molecular structure contains numerous hydroxyl and carboxyl groups, which help slow down the pouring speed, facilitating heat dissipation, regulating concrete setting time, reducing slump, adjusting workability, and improving compatibility with cement and water-reducing agents. The addition of ice chips lowers the temperature generated during concrete mixing, reducing hydration heat. Simultaneously, the surface of fine aggregates is modified to form a dense polymer film, reducing cracks caused by plastic shrinkage and effectively improving the flexural and compressive strength of the concrete. Through the synergistic effect of the raw materials, this high-performance concrete has promising applications in the preparation of fire evacuation platforms. Detailed Implementation

[0020] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0021] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0022] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0023] Example 1

[0024] A low-shrinkage, crack-resistant, ultra-high performance concrete comprises the following raw materials in parts by weight: 33 parts silicate cement, 19 parts slag powder, 20 parts fly ash, 12 parts silica fume, 22 parts crushed stone, 18 parts modified fine aggregate, 15 parts high-performance expansive agent, 12 parts crack-resistant admixture, 17 parts retarder, and 2 parts water-reducing agent.

[0025] Crushed stone is made from natural rocks, pebbles, or mine waste rock through mechanical crushing and screening, and consists of rock particles with a particle size greater than 5mm.

[0026] Modified fine aggregate is prepared by mixing manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of 3.2:1.3:8.6, grinding them in a mixer for 1 hour, adding 5% silane coupling agent by mass and ultrasonically mixing for 5 minutes, washing and drying to obtain modified fine aggregate with a particle size of less than 4.75 mm.

[0027] The high-performance expanding agent is a CAL fiber composite quaternary expanding agent with a mass ratio of 10:18:2, lightly calcined magnesium oxide, and active calcium oxide;

[0028] The crack-resistant admixture is lauryl ketone;

[0029] The retarder consists of sodium tripolyphosphate, sodium gluconate, and sodium carboxymethyl cellulose in a mass ratio of 7.6:1.0:5.6.

[0030] The water-reducing agent is an acrylic polycarboxylic acid.

[0031] Example 2

[0032] A low-shrinkage, crack-resistant, ultra-high performance concrete comprises the following raw materials in parts by weight: 50 parts silicate cement, 28 parts slag powder, 38 parts fly ash, 28 parts silica fume, 40 parts crushed stone, 36 parts modified fine aggregate, 26 parts high-performance expansive agent, 28 parts crack-resistant admixture, 29 parts retarder, 8 parts water-reducing agent, and 6 parts ice chips.

[0033] Crushed stone is made from natural rocks, pebbles, or mine waste rock through mechanical crushing and screening, and consists of rock particles with a particle size greater than 5mm.

[0034] Modified fine aggregate is prepared by mixing manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of 5.8:3.9:9.5, grinding them in a mixer for 3 hours, adding 8% silane coupling agent by mass and ultrasonically mixing for 10 minutes, washing and drying to obtain modified fine aggregate with a particle size of less than 4.75 mm.

[0035] The high-performance expanding agent is a CAL fiber composite quaternary expanding agent, lightly calcined magnesium oxide, and active calcium oxide in a mass ratio of 20:22:10.

[0036] The crack-resistant additive is dialkyl sulfosuccinate;

[0037] The retarder consists of sodium tripolyphosphate, sodium gluconate, and sodium carboxymethyl cellulose in a mass ratio of 8.8:3.8:10.2.

[0038] The water-reducing agent is sodium lauryl sulfate.

[0039] Example 3

[0040] A low-shrinkage, crack-resistant, ultra-high performance concrete comprises the following raw materials in parts by weight: 42 parts silicate cement, 25 parts slag powder, 29 parts fly ash, 19 parts silica fume, 31 parts crushed stone, 28 parts modified fine aggregate, 20 parts high-performance expansive agent, 18 parts crack-resistant admixture, 22 parts retarder, 6 parts water-reducing agent, and 3 parts ice chips.

[0041] Crushed stone is made from natural rocks, pebbles, or mine waste rock through mechanical crushing and screening, and consists of rock particles with a particle size greater than 5mm.

[0042] Modified fine aggregate is prepared by mixing manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of 4.2:3.1:9.1, grinding them in a mixer for 1-3 hours, adding 7% silane coupling agent by mass and ultrasonically mixing for 8 minutes, washing and drying to obtain modified fine aggregate with a particle size of less than 4.75 mm.

[0043] The high-performance expanding agent is a CAL fiber composite quaternary expanding agent with a mass ratio of 15:20:6, lightly calcined magnesium oxide, and active calcium oxide;

[0044] The crack-resistant additive is SY-T type high-efficiency special expanded fiber crack-resistant agent;

[0045] The retarder consists of sodium tripolyphosphate, sodium gluconate, and sodium carboxymethyl cellulose in a mass ratio of 8.2:2.5:8.1.

[0046] The water-reducing agent is calcium lignosulfonate.

[0047] The above Examples 1-3 were prepared using the following methods:

[0048] Step S1: Mix silicate cement, slag powder, fly ash and silica fume to obtain a mixture, then add water and put it into a concrete mixer for mixing. The mass-volume ratio of the mixture to water (g / mL) is 45:7, the mixing speed is 400 rpm, and the mixing time is 32 min to obtain the concrete precursor.

[0049] Step S2: Add crushed stone and modified fine aggregate to the concrete precursor prepared in S1 and mix. While mixing, circulate cold water is introduced at a flow rate of 6 m³ / s. 3 / h, the feed rate is 1 / 6 of the volume of concrete precursor, to obtain concrete mix;

[0050] Step S3: Add high-performance expansion agent, crack-resistant admixture, retarder, water-reducing agent or ice chips to the above-mentioned initial setting mixture, mix at high speed for 42 minutes at a mixing speed of 2200 rpm to obtain the initial setting mixture, pour it into the mold, compact it, spray water for curing, demold it, and cure it to obtain high-performance concrete.

[0051] Example 4

[0052] A low-shrinkage, crack-resistant, ultra-high performance concrete comprises the following raw materials in parts by weight: 42 parts silicate cement, 25 parts slag powder, 29 parts fly ash, 19 parts silica fume, 31 parts crushed stone, 28 parts modified fine aggregate, 20 parts high-performance expansive agent, 18 parts crack-resistant admixture, 22 parts retarder, 6 parts water-reducing agent, and 3 parts ice chips.

[0053] Crushed stone is made from natural rocks, pebbles, or mine waste rock through mechanical crushing and screening, and consists of rock particles with a particle size greater than 5mm.

[0054] Modified fine aggregate is prepared by mixing manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of 4.2:3.1:9.1, grinding them in a mixer for 1 hour, adding 7% silane coupling agent by mass and ultrasonically mixing for 8 minutes, washing and drying to obtain modified fine aggregate with a particle size of less than 4.75 mm.

[0055] The high-performance expanding agent is a CAL fiber composite quaternary expanding agent with a mass ratio of 15:20:6, lightly calcined magnesium oxide, and active calcium oxide;

[0056] The crack-resistant additive is SY-T type high-efficiency special expanded fiber crack-resistant agent;

[0057] The retarder consists of sodium tripolyphosphate, sodium gluconate, and sodium carboxymethyl cellulose in a mass ratio of 8.2:2.5:8.1.

[0058] The water-reducing agent is calcium lignosulfonate.

[0059] The above-mentioned concrete is prepared using the following method:

[0060] Step S1: Mix silicate cement, slag powder, fly ash and silica fume to obtain a mixture, then add water and put it into a concrete mixer for mixing. The mass-volume ratio of the mixture to water (g / mL) is 39:5, the mixing speed is 300 rpm, and the mixing time is 15 min to obtain the concrete precursor.

[0061] Step S2: Add crushed stone and modified fine aggregate to the concrete precursor prepared in S1 and mix. While mixing, circulate cold air is introduced at a flow rate of 12 mL / min and a volume of 200 mL to obtain concrete mix.

[0062] Step S3: Add high-performance expansion agent, crack-resistant admixture, retarder, water-reducing agent and ice chips to the above-mentioned initial set mixture, stir at high speed for 15 minutes at a stirring speed of 2000 rpm to obtain the initial set mixture, pour it into the mold, compact it, sprinkle water for curing, demold it, and cure it to obtain high-performance concrete.

[0063] Example 5

[0064] A low-shrinkage, crack-resistant, ultra-high performance concrete comprises the following raw materials in parts by weight: 42 parts silicate cement, 25 parts slag powder, 29 parts fly ash, 19 parts silica fume, 31 parts crushed stone, 28 parts modified fine aggregate, 20 parts high-performance expansive agent, 18 parts crack-resistant admixture, 22 parts retarder, 6 parts water-reducing agent, and 3 parts ice chips.

[0065] Crushed stone is made from natural rocks, pebbles, or mine waste rock through mechanical crushing and screening, and consists of rock particles with a particle size greater than 5mm.

[0066] Modified fine aggregate is prepared by mixing manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of 4.2:3.1:9.1, grinding them in a mixer for 1-3 hours, adding 7% silane coupling agent by mass and ultrasonically mixing for 8 minutes, washing and drying to obtain modified fine aggregate with a particle size of less than 4.75 mm.

[0067] The high-performance expanding agent is a CAL fiber composite quaternary expanding agent with a mass ratio of 15:20:6, lightly calcined magnesium oxide, and active calcium oxide;

[0068] The crack-resistant additive is SY-T type high-efficiency special expanded fiber crack-resistant agent;

[0069] The retarder consists of sodium tripolyphosphate, sodium gluconate, and sodium carboxymethyl cellulose in a mass ratio of 8.2:2.5:8.1.

[0070] The water-reducing agent is calcium lignosulfonate.

[0071] The above-mentioned concrete is prepared using the following method:

[0072] Step S1: Mix silicate cement, slag powder, fly ash and silica fume to obtain a mixture, then add water and put it into a concrete mixer for mixing. The mass-volume ratio of the mixture to water (g / mL) is 52:10, the mixing speed is 500 rpm, and the mixing time is 50 min to obtain the concrete precursor.

[0073] Step S2: Add crushed stone and modified fine aggregate to the concrete precursor prepared in S1 and mix. While mixing, circulate cold water is introduced at a flow rate of 10 m³ / min. 3 / h, the feed rate is 1 / 5 of the volume of concrete precursor, to obtain concrete mix;

[0074] Step S3: Add high-performance expansion agent, crack-resistant admixture, retarder, water-reducing agent and ice chips to the above-mentioned initial set mixture, mix at high speed for 60 minutes at a mixing speed of 2500 rpm to obtain the initial set mixture, pour it into the mold, compact it, spray water for curing, demold it, and cure it to obtain high-performance concrete.

[0075] I. Performance Effect

[0076] The ultra-high performance concrete obtained in Examples 1-5 above was tested for its slump, spread, mechanical properties, and drying shrinkage value. The testing standards and methods are as follows:

[0077] (1) Slump test standard: GB / T50080-2016;

[0078] (2) Standard for testing compressive strength and flexural strength: Refer to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" to make standard test blocks of 10cm×10cm×10cm, and test their flexural strength and compressive strength after curing for 7d and 28d.

[0079] (3) Crack resistance test: Standard test blocks were made in accordance with GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The number of cracks on the concrete surface was recorded after curing for 28 days under an ambient temperature of 42±2℃ to obtain the number of cracks per unit area.

[0080] (4) Shrinkage performance test: Standard test blocks were made in accordance with GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", and cured in an outdoor environment at 42±2℃. Then, the 28-day shrinkage rate data were recorded in accordance with GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete".

[0081] (5) Fracture energy test: The three-point bending method TC50-FMC is used for testing. The sample is placed on the testing machine and the parameters of the testing machine are adjusted according to the standard specifications. A force of 2000N is applied to the center of the sample to induce bending deformation. The fracture energy of the sample is calculated based on the test data.

[0082] The results are as follows:

[0083]

[0084] The results above show that the ultra-high performance concrete prepared according to this invention has high mechanical properties: 7-day flexural strength of 39-43 MPa, 28-day flexural strength of 35-39 MPa, 7-day compressive strength of 201-206 MPa, 28-day compressive strength of 180-185 MPa, no cracks, shrinkage rate of 0.10-0.15‰, and fracture energy of 3.8-4.2 × 10⁻⁶ MPa. 4 J / m 2 It can be seen that the concrete of the present invention has low shrinkage effect, high mechanical strength, good durability and load-bearing capacity, and the effect of Example 3 is the best.

[0085] A comparison ratio is set up for the above-mentioned preferred embodiment 3, as follows:

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 3 is that the low-shrinkage, crack-resistant, ultra-high performance concrete includes the following raw materials in parts by weight: 60 parts silicate cement, 15 parts slag powder, 12 parts fly ash, 10 parts silica fume, 55 parts crushed stone, 10 parts modified fine aggregate, 12 parts high-performance expansion agent, 10 parts crack-resistant admixture, 15 parts retarder, and 12 parts water-reducing agent.

[0088] Comparative Example 2

[0089] The difference between this comparative example and Example 3 is that the fine aggregate is unmodified and is a mixture of manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of 4.2:3.1:9.1.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 3 is that no high-performance expansion agent was added to the raw materials of the low-shrinkage, crack-resistant ultra-high performance concrete.

[0092] Specifically, the raw materials include the following parts by weight: 42 parts silicate cement, 25 parts slag powder, 29 parts fly ash, 19 parts silica fume, 31 parts crushed stone, 28 parts modified fine aggregate, 18 parts crack-resistant admixture, 22 parts retarder, 6 parts water-reducing agent, and 3 parts ice chips.

[0093] Crushed stone is made from natural rocks, pebbles, or mine waste rock through mechanical crushing and screening, and consists of rock particles with a particle size greater than 5mm.

[0094] Modified fine aggregate is prepared by mixing manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of 4.2:3.1:9.1, grinding them in a mixer for 1-3 hours, adding 7% silane coupling agent by mass and ultrasonically mixing for 8 minutes, washing and drying to obtain modified fine aggregate with a particle size of less than 4.75 mm.

[0095] The crack-resistant additive is SY-T type high-efficiency special expanded fiber crack-resistant agent;

[0096] The retarder consists of sodium tripolyphosphate, sodium gluconate, and sodium carboxymethyl cellulose in a mass ratio of 8.2:2.5:8.1.

[0097] The water-reducing agent is calcium lignosulfonate.

[0098] Low-shrinkage, crack-resistant ultra-high performance concrete is prepared using the following methods:

[0099] Step S1: Mix silicate cement, slag powder, fly ash and silica fume to obtain a mixture, then add water and put it into a concrete mixer for mixing. The mass-volume ratio of the mixture to water (g / mL) is 45:7, the mixing speed is 400 rpm, and the mixing time is 32 min to obtain the concrete precursor.

[0100] Step S2: Add crushed stone and modified fine aggregate to the concrete precursor prepared in S1 and mix. While mixing, circulate cold water is introduced at a flow rate of 6 m³ / s. 3 / h, the feed rate is 1 / 6 of the volume of concrete precursor, to obtain concrete mix;

[0101] Step S3: Add high-performance expansion agent, crack-resistant admixture, retarder, water-reducing agent or ice chips to the above-mentioned initial setting mixture, mix at high speed for 42 minutes at a mixing speed of 2200 rpm to obtain the initial setting mixture, pour it into the mold, compact it, spray water for curing, demold it, and cure it to obtain high-performance concrete.

[0102] Comparing Comparative Examples 1-3 and Example 3 above, using the same test methods and standards, the results are as follows:

[0103]

[0104] The results above show that, compared with Comparative Example 1, the concrete raw material of the present invention has reasonable material selection and scientific proportioning, which synergistically exerts its performance effect, resulting in low shrinkage, strong mechanical properties, and resistance to breakage. Compared with Comparative Example 2, after the surface of the fine aggregate is modified, a dense polymer film is formed on the surface of the fine aggregate, which reduces cracks caused by plastic shrinkage, reduces the formation of cracks, and effectively improves the flexural strength and compressive strength of concrete. Compared with Comparative Example 3, the addition of a high-performance expansive agent in Example 3 can play a role in crack resistance and seepage prevention of the concrete raw material, and its expansion performance can compensate for the shrinkage during the hardening process of concrete.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-shrinkage, crack-resistant, ultra-high performance concrete, characterized in that: It is composed of the following raw materials in parts by weight: 33-50 parts silicate cement, 19-28 parts slag powder, 20-38 parts fly ash, 12-28 parts silica fume, 22-40 parts crushed stone, 18-36 parts modified fine aggregate, 15-26 parts high-performance expansive agent, 12-28 parts crack-resistant admixture, 17-29 parts retarder, 2-8 parts water-reducing agent, and 3-6 parts ice chips; The high-performance expanding agent is a CAL fiber composite quaternary expanding agent, lightly calcined magnesium oxide, and active calcium oxide in a mass ratio of (10-20):(18-22):(2-10). The retarder is composed of sodium tripolyphosphate, sodium gluconate and sodium carboxymethyl cellulose in a mass ratio of (7.6-8.8):(1.0-3.8):(5.6-10.2). The modified fine aggregate is prepared by mixing manufactured sand, vermiculite powder, and iron tailings particles in a mass ratio of (3.2-5.8):(1.3-3.9):(8.6-9.5), grinding them in a mixer for 1-3 hours, adding 5-8% silane coupling agent by mass, ultrasonically mixing for 5-10 minutes, washing and drying to obtain modified fine aggregate with a particle size of less than 4.75 mm.

2. The low-shrinkage, crack-resistant ultra-high performance concrete as described in claim 1, characterized in that: It is composed of the following raw materials in parts by weight: 42 parts silicate cement, 25 parts slag powder, 29 parts fly ash, 19 parts silica fume, 31 parts crushed stone, 28 parts modified fine aggregate, 20 parts high-performance expansive agent, 18 parts crack-resistant admixture, 22 parts retarder, 6 parts water-reducing agent, and 3 parts ice chips.

3. The low-shrinkage, crack-resistant ultra-high performance concrete as described in claim 1, characterized in that: The crushed stone is selected from natural rocks, pebbles, or mine waste rock that are mechanically crushed and screened, and consists of rock particles with a particle size greater than 5 mm.

4. The low-shrinkage, crack-resistant ultra-high performance concrete as described in claim 1, characterized in that: The crack-resistant additive is any one of lauryl ketone, dialkyl sulfosuccinate, or SY-T type high-efficiency special expandable fiber crack-resistant agent.

5. The low-shrinkage, crack-resistant ultra-high performance concrete as described in claim 1, characterized in that: The water-reducing agent is any one of acrylic polycarboxylic acid, sodium lauryl sulfate, and calcium lignosulfonate.

6. The method for preparing low-shrinkage, crack-resistant ultra-high performance concrete according to claim 1, characterized in that: Includes the following steps: Step S1: Mix silicate cement, slag powder, fly ash and silica fume to obtain a mixture, then add water and put it into a concrete mixer for mixing. The mixing speed is 300-500 rpm and the mixing time is 15-50 min to obtain the concrete precursor. Step S2: Add crushed stone and modified fine aggregate to the concrete precursor prepared in S1 and mix them while circulating cold water or cold air is introduced to obtain concrete mix. Step S3: Add high-performance expansion agent, crack-resistant admixture, retarder, water-reducing agent and ice chips to the above concrete mix, mix at high speed for 15-60 minutes at a mixing speed of 2000-2500 rpm to obtain initial set mixture, pour into mold, compact, water curing, demold, and cure to obtain high-performance concrete.

7. The method for preparing low-shrinkage, crack-resistant ultra-high performance concrete as described in claim 6, characterized in that: In step S1, the mass volume ratio (g / mL) of the mixture and water is 39-52:5-10.

8. The low-shrinkage, crack-resistant ultra-high performance concrete as described in claim 6, characterized in that: In step S2, the flow rate of the circulating cold water is 2-10 m³ / h. 3 / h, the injection rate is 1 / 8-1 / 5 of the concrete precursor volume; the cold air injection flow rate is 12-28mL / min, and the injection volume is 200-800mL.

9. The application of the low-shrinkage, crack-resistant ultra-high performance concrete as described in any one of claims 1-5 in the preparation of elevated evacuation platforms for high-speed railways and subways.

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