A negative carbon high-performance concrete and a preparation method thereof

Abstract

The application relates to the technical field of building materials, and discloses a kind of negative carbon high-performance concrete and a preparation method thereof, adopt ferrochrome slag as aggregate, utilize slag powder, silica fume and waste stone powder to partially replace cement to prepare concrete, which not only reduces natural resource and energy consumption, reduces CO2 emission, but also promotes efficient utilization of industrial solid waste; in addition, the mechanical interlocking structure is formed between the spherical pores on the surface of ferrochrome slag and cement stone, which can improve the interface microstructure between aggregate and cement paste; at the same time, the olivine phase on the surface of the spherical pores dissolves and occurs carbonation reaction under high-temperature alkaline environment during high-temperature carbonization process, and needle-like magnesium carbonate crystals are generated in the spherical pores to fill the interface, thereby further optimizing the interface microstructure and improving the overall mechanical properties of the concrete.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a kind of negative carbon high-performance concrete and preparation method thereof. BACKGROUND

[0002] Concrete is the largest amount of current use, the widest application range of artificial materials. The production preparation process of existing cement concrete, including cement clinker calcination, mechanism aggregate crushing and concrete component steam curing process all need to consume a lot of energy and emit CO2. According to preliminary statistics, the CO2 emission of ordinary portland cement concrete is 200-350 kg / m 3 , and carbon emission accounts for 18%-22% of the total CO2 emission in China. How to reduce the comprehensive carbon emission of concrete materials and prepare low-carbon or negative-carbon concrete is a major issue facing the industry.

[0003] The rapid development of China's steel and metallurgical industry produces a large amount of metallurgical slag, including blast furnace slag, steel slag, chromium iron alloy slag, silicon manganese slag and nickel iron slag, with an annual discharge of more than 200 million tons, which needs to be developed and utilized. Grinding metallurgical slag into mineral admixtures or crushing into aggregates to replace cement and natural sand and stone not only realizes efficient utilization of solid waste resources, but also reduces the consumption of natural resources and energy and CO2 emission. In addition, the large amount of Ca 2+ in cement concrete can also combine with CO2 to occur mineralization reaction, so that CO 2· can be efficiently sequestrated and utilized through carbonation curing of cement concrete.

[0004] However, there is still a problem of poor interface bonding between metallurgical slag as aggregate and cement hardened paste. At the same time, the carbonation reaction of concrete is a neutralization process, which will cause the internal pH value of concrete to decrease, which will have a certain negative impact on CO2 absorption and sequestration. SUMMARY

[0005] In view of the deficiencies and problems of the prior art, the present application provides a kind of negative carbon high-performance concrete and preparation method thereof, the interface microstructure of aggregate and cement stone is optimized by in-situ high-temperature carbonation reaction on the surface of chromium iron slag aggregate, the overall mechanical properties of concrete are improved;The alkaline environment inside the concrete is adjusted by making full use of the neutralization process of carbonation reaction to prepare high-performance green concrete;With the aid of the crystal nucleus effect of waste rock powder, the carbonation reaction in the cement paste is accelerated, and the direct absorption and solidification of CO2 by concrete are promoted.

[0006] To achieve the above technical effects, the technical scheme adopted by the present application is:

[0007] The negative carbon high-performance concrete is made from mixed raw materials through stirring, molding, pre-curing and carbonization curing process steps in sequence; the mixed raw materials comprise, in terms of weight parts, chromium-iron alloy slag aggregate 1810-1850 parts, cement 219-239 parts, slag powder 127-147 parts, silica fume 13-33 parts, waste stone powder 59-79 parts, water reducing agent 0.3-0.5 parts, water retaining agent 0.5-1.0 parts and water 100-120 parts; the chromium-iron alloy slag aggregate is waste slag with a particle size in the range of 15-20 mm obtained from molten slag discharged during smelting of high-carbon chromium-iron alloy by electric arc furnace through air natural cooling, crushing and jigging separation in sequence; the waste slag surface has a large number of closed spherical pores, and the main mineral composition is forsterite, spinel and enstatite.

[0008] Further, the cement is P.O 425R ordinary portland cement meeting the requirements of national standards; the slag powder is S95 grade granulated blast furnace slag powder meeting the requirements of national standards; and the silica fume is ordinary silica fume meeting the requirements of national standards, with a mass percentage of SiO2≧95%.

[0009] Further, the waste stone powder comprises the following mass fractions of chemical compositions: 45-50% CaO, 5-10% SiO2, 0-5% Al2O3, 0-5% MgO, 0-5% FeO, 0-5% (Na2O+K2O) and a loss on ignition of 30-35%.

[0010] Further, the waste stone powder is obtained by putting waste solid particles generated in the processing of limestone, machine-made sand or marble into a Φ500mm*500mm standard cement test mill for grinding for 30 min to obtain a fineness of 0-0.048mm powder material.

[0011] Further, the water reducing agent is a commercially available polycarboxylic acid water reducing agent with a water reducing rate of 25%, and the water retaining agent is a commercially available hydroxypropyl methylcellulose ether in powder form with a viscosity of 40000mPa.s.

[0012] To achieve the above technical effects, the application further provides a preparation method of the negative carbon high-performance concrete, which is used for preparing the negative carbon high-performance concrete and comprises the following steps:

[0013] The raw materials are mixed according to the proportion to make the slurry uniformly wrapped on the surface of the aggregate to obtain fresh concrete;

[0014] The fresh concrete is molded and then vibrated;

[0015] The molded concrete piece is pre-cured for 12-24h, and the curing room temperature is controlled to be 20±2℃ and the relative humidity is controlled to be 50-65% RH;

[0016] After the pre-cured concrete piece is demolded, the concrete piece is placed into a carbonation curing kettle, vacuum in the carbonation curing kettle is controlled to be -0.098~0 MPa, CO2 gas is introduced to stabilize the pressure in the carbonation curing kettle to be 0.1~0.5 MPa, the curing temperature is kept at 50~80 DEG C, and after the carbonation curing process lasts for 5~8 hours, the negative carbon high-performance concrete is obtained.

[0017] Further, the step of mixing the raw materials according to the proportion to make the slurry uniformly wrap the surface of the aggregate to obtain the freshly mixed concrete comprises: mixing the cement, slag powder, silica fume, limestone powder, water reducing agent and water retaining agent in the concrete mixer according to the proportion for 2~5 min to mix uniformly, then pouring all the water to stir for 1~2 min to obtain the uniform slurry, and finally adding the ferrochrome slag aggregate to continue stirring for 1~2 min to make the slurry uniformly wrap the surface of the aggregate to obtain the freshly mixed concrete.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] 1. The present application uses ferrochrome slag as aggregate, and uses slag powder, silica fume and waste stone powder to partially replace cement to prepare concrete, which not only reduces the consumption of natural resources and energy and the emission of CO2, but also promotes the efficient utilization of industrial solid waste; in addition, the mechanical interlocking structure is formed between the spherical pores on the surface of the ferrochrome slag and the cement stone, which can improve the interface microstructure between the aggregate and the cement slurry; at the same time, the olivine phase on the surface of the spherical pores dissolves and undergoes carbonation reaction in the high-temperature alkaline environment during the high-temperature carbonation process, and needle-shaped magnesium carbonate crystals are generated in the spherical pores to further optimize the interface microstructure and improve the overall mechanical properties of the concrete.

[0020] 2. The micro-filling effect of the ground waste stone powder improves the cement hydration microstructure and improves the compressive strength of the concrete, and the calcium carbonate in the waste stone powder can produce a nucleation effect to accelerate the carbonation reaction of the cement slurry and further promote the direct absorption and solidification of CO2 by the concrete.

[0021] 3. The present application accelerates the carbonation and neutralization reaction of the alkaline hydration product with CO2 through high-temperature carbonation, thereby reducing the internal alkalinity and pH value of the concrete, which is beneficial to the growth and development of plants and the construction of the plant-growing concrete ecological system, and plays an important role in promoting ecological environment governance and long-term carbon sink of concrete.

[0022] 4. The present application realizes the comprehensive negative carbon emission of the concrete material in the whole life cycle from preparation, curing to service through the synergistic effect of waste resources, carbon reduction, concrete curing, and long-term carbon sink of the plant-growing concrete ecological system. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1The appearance morphology photo of the chromium-iron slag aggregate in Example 1.

[0024] Figure 2 The surface XRD mineral composition analysis chart of the chromium-iron slag aggregate in Example 1.

[0025] Figure 3 The micro-morphology chart of the interfacial bonding zone of the negative carbon high-performance concrete in Example 2. DETAILED DESCRIPTION

[0026] The application will be further described in conjunction with the examples and the accompanying drawings. However, it should not be understood that the above-mentioned subject matter of the application is limited to the following examples only, and any technology realized based on the content of the application falls within the scope of the application.

[0027] Example 1

[0028] A negative carbon high-performance concrete is prepared by mixing raw materials and then sequentially performing the steps of stirring, molding, pre-curing and carbonation curing; the raw materials include, by weight fraction, 1810-1850 parts of chromium-iron alloy slag aggregate, 219-239 parts of cement, 127-147 parts of slag powder, 13-33 parts of silica fume, 59-79 parts of waste stone powder, 0.3-0.5 parts of water reducing agent, 0.5-1.0 parts of water retaining agent, and 100-120 parts of water.

[0029] In this example, the chromium-iron alloy slag is used as the aggregate, and the slag powder, silica fume and waste stone powder are used to partially replace the cement to prepare the concrete, which not only reduces the consumption of natural resources and energy and the emission of CO2, but also promotes the efficient utilization of industrial solid waste; the chromium-iron alloy slag aggregate is the waste slag with a particle size of 15-20 mm obtained by sequentially performing air natural cooling, crushing and jigging separation on the molten slag discharged during the smelting of high-carbon chromium-iron alloy by an electric arc furnace; the waste slag surface has a large number of closed spherical pores, which are mainly formed by the surface air entrained by the molten slag during the slag discharge process, and the waste slag morphology is as shown in Figure 1 The waste slag surface XRD chart obtained by performing XRD analysis on the waste slag surface is as shown in Figure 2As shown, it can be known that the main mineral composition in the spherical hole inside the waste residue surface is forsterite, spinel and a small amount of enstatite. The mechanical interlocking structure is formed between the spherical hole on the surface of the chromium-iron alloy slag and the cement stone, which can improve the interface microstructure between the aggregate and the cement paste; at the same time, the forsterite phase on the surface of the spherical hole is dissolved and carbonation reaction occurs under high temperature and alkaline environment during high temperature carbonation process, and needle-shaped magnesium carbonate crystals are generated in the spherical hole to fill the interface, thereby further optimizing the interface microstructure and improving the overall mechanical properties of the concrete. The micro-filling effect of the ground waste stone powder improves the cement hydration microstructure and improves the compressive strength of the concrete, and the calcium carbonate in the waste stone powder can produce a nucleation effect, which can accelerate the carbonation reaction of the cement paste, and further promote the direct absorption and solidification of CO2 by the concrete.

[0030] On the basis of the above, the carbonation and neutralization reaction of the alkaline hydration product with CO2 is also accelerated during the high temperature carbonation curing process, thereby reducing the internal alkalinity and pH value of the concrete, which is beneficial to the growth and development of plants and the construction of the plant-growing concrete ecological system, and plays an important role in promoting the ecological environment governance and long-term carbon sink of concrete.

[0031] In summary, the present application realizes the comprehensive negative carbon emission of the concrete material from preparation, curing to service life through the synergistic carbon reduction of solid waste resources, the carbon sequestration of concrete and the long-term carbon sink of the plant-growing concrete ecological system.

[0032] In the embodiment, the waste stone powder comprises the following mass fractions of chemical compositions: 45% to 50% CaO, 5% to 10% SiO2, 0% to 5% Al2O3, 0% to 5% MgO, 0% to 5% FeO, 0% to 5% (Na2O+K2O), and a loss on ignition of 30% to 35%.

[0033] Example 2

[0034] A preparation method of a negative carbon high-performance concrete, the raw material ratio is: chromium-iron alloy slag aggregate 1810 parts, cement 239 parts, slag powder 127 parts, silica fume 13 parts, waste stone powder 59 parts, water reducing agent 0.5 parts, water retaining agent 1.0 parts, water 100 parts, and the specific preparation process comprises:

[0035] 1) Stirring: first, the cement, slag powder, silica fume, waste stone powder, water reducing agent and water retaining agent and other powder materials are stirred in the concrete mixer for 2 minutes to mix uniformly, then pour all the water into the mixer to stir for 2 minutes to obtain a uniform slurry, and finally add the ferrochrome slag aggregate to continue stirring for 2 minutes to make the slurry uniformly wrap the surface of the aggregate; the waste stone powder used in this embodiment is obtained by putting the waste solid particles generated in the processing of limestone, machine-made sand or marble into a Φ500mm×500mm standard cement test mill to grind for 30 minutes to obtain a fine powder material with a fineness of 0-0.048mm. The water reducing agent used is a commercially available polycarboxylic acid water reducing agent with a water reducing rate of 25%; the water retaining agent is a commercially available hydroxypropyl methylcellulose ether in powder form with a viscosity of 40000mPa.s. It should be noted that other types of concrete water reducing agents and water retaining agents are also suitable for the present application.

[0036] The cement used in this embodiment is P.O 425R ordinary portland cement meeting the requirements of national standards; the slag powder is S95 grade granulated blast furnace slag powder meeting the requirements of national standards; and the silica fume is ordinary silica fume meeting the requirements of national standards with a mass percentage of SiO2≧95%. The slag powder and silica fume have good activity, which helps to reduce the cement dosage, increase the low-carbon properties and mechanical properties of concrete. The waste stone powder is obtained by putting the waste solid particles generated in the processing of limestone, machine-made sand or marble into a Φ500mm×500mm standard cement test mill to grind for 30 minutes to obtain a fine powder material with a fineness of 0-0.048mm, which can fully play the filling effect and crystal nucleus effect of the limestone powder and is beneficial to carbonation curing and improvement of the mechanical properties of concrete.

[0037] 2) Molding: the freshly mixed concrete slurry is loaded into a 100mm×100mm×100mm test mold, then the test mold is placed on a concrete vibrating table to vibrate for 10 seconds, and the molding surface is smoothed with a spatula;

[0038] 3) Pre-curing: the molded concrete test piece together with the test mold is placed in a concrete dry shrinkage curing room for pre-curing for 24 hours, and the temperature and relative humidity in the curing room are controlled at 20±2℃ and 60%RH respectively;

[0039] 4) High-temperature carbonation curing: after the pre-cured concrete test piece is demolded, it is placed in a carbonation curing kettle, the vacuum valve is opened to evacuate the curing kettle to-0.098MPa, the pressure is stabilized for 2 minutes, then the vacuum valve is closed, the CO2 inlet valve is opened and CO2 gas is introduced to stabilize the pressure in the curing kettle at 0.4MPa, the entire carbonation curing process lasts for 5 hours, at the same time, the temperature in the curing kettle is maintained at 80℃ by using an electric heating jacket, after the curing is completed, the CO2 inlet valve is closed and the exhaust valve is opened to reduce the temperature and pressure in the curing kettle to the ambient state, finally the cured test piece is taken out, which is a negative carbon high-performance concrete.

[0040] The macro-porosity of the negative carbon high performance concrete is tested by drainage method, the compressive strength of the negative carbon high performance concrete is tested by uniaxial compression strength test, the broken concrete test piece is crushed, ground, soaked, and filtered, and the internal pH value of the negative carbon high performance concrete is measured by using an acidity meter. The crushed concrete test piece containing the interface bonding area between the aggregate and the cement stone is selected, and the interface micro-morphology is observed by using a scanning electron microscope (SEM) after gold spraying.

[0041] It is tested that the compressive strength of the negative carbon high performance concrete in the embodiment is 33 MPa, the porosity is 28%, and the internal pH value is 9.8. The SEM photo is as shown in FIG. 3. Figure 3 As shown in FIG. 3, the magnesium carbonate crystals in the form of partial needle rods are generated at the interface between the ferrochrome slag aggregate and the cement stone, and the magnesium carbonate crystals are generated by the carbonization reaction of the magnesium olivine on the surface of the ferrochrome slag with CO2 gas under the high-temperature alkaline environment condition.

[0042] Although the specific embodiments of the present application are described in detail, it should not be understood as the limitation of the protection scope of the present patent. Various modifications and changes made by those skilled in the art within the scope described in the claims are still within the protection scope of the present patent.

Claims

1. A carbon-negative high-performance concrete, characterized in that: The negative carbon high performance concrete is made by sequentially mixing, molding, pre-curing and carbonization curing process steps of mixed raw materials; during the carbonization curing process, the carbonization curing kettle is vacuumed to -0.098-0 MPa, and CO2 gas is introduced to stabilize the pressure in the curing kettle at 0.1-0.5 MPa, the curing temperature is maintained at 50-80°C, and the carbonization curing process lasts for 5-8 hours; the mixed raw materials include, by weight, 1810-1850 parts of ferrochrome slag aggregate, 219-23 parts of cement, and 10 parts of chromium slag aggregate. 9 parts, slag powder 127-147 parts, silica fume 13-33 parts, waste rock powder 59-79 parts, water reducer 0.3-0.5 parts, water retaining agent 0.5-1.0 parts, water 100-120 parts; the ferrochrome alloy slag aggregate is waste slag with a particle size of 15-20 mm obtained by naturally cooling, crushing and jigging slag discharged during the smelting of high-carbon ferrochrome alloy in an electric arc furnace; the waste slag has a large number of closed spherical pores on the surface, and the main mineral components are forsterite, spinel and enstatite.

2. The negative carbon high performance concrete according to claim 1, characterized in that: The cement is PO 425R ordinary Portland cement that meets the national standard requirements; the slag powder is S95 grade granulated blast furnace slag powder that meets the national standard requirements; the silica fume is ordinary silica fume that meets the national standard requirements, and the SiO2 mass percentage content is ≥95%.

3. The negative carbon high performance concrete according to claim 1, characterized in that: The waste rock powder includes the following chemical composition by mass fraction: 45% to 50% CaO, 5% to 10% SiO2, 0% to 5% Al2O3, 0% to 5% MgO, 0% to 5% FeO, 0% to 5% (Na2O+K2O), and a loss on ignition of 30% to 35%.

4. The negative carbon high performance concrete according to claim 3, characterized in that: The waste stone powder is waste solid particles generated by limestone, machine-made sand or marble processing, which are put into a Φ500mm×500mm standard cement test mill and ground for 30 minutes to obtain a powder material with a fineness of 0-0.048mm.

5. The negative carbon high performance concrete according to claim 1, characterized in that: The water reducing agent is a commercially available polycarboxylate water reducing agent with a water reduction rate of 25%; the water retaining agent is a commercially available hydroxypropyl methylcellulose ether in powder form with a viscosity of 40,000 mPa.s.

6. A method for preparing negative carbon high performance concrete, the method being used to prepare the negative carbon high performance concrete according to any one of claims 1 to 5, characterized in that: The following steps are involved: Mix the raw materials according to the proportions so that the slurry is evenly coated on the surface of the aggregate to obtain fresh concrete; Filling the fresh concrete into a mold and then vibrating it into shape; Pre-curing the formed concrete pieces for 12 to 24 hours, controlling the temperature in the curing room to 20±2°C and the relative humidity to 50 to 65%RH; The pre-cured concrete parts are demolded and placed in a carbonation curing kettle. The vacuum in the carbonation curing kettle is controlled to be -0.098~0MPa, and CO2 gas is introduced to stabilize the pressure in the curing kettle at 0.1~0.5MPa. The curing temperature is maintained at 50~80℃. After the carbonation curing process lasts for 5~8h, the negative carbon high performance concrete is obtained.

7. The method for preparing negative carbon high performance concrete according to claim 6, characterized in that: The steps of mixing the raw materials according to the proportion so that the slurry is evenly coated on the surface of the aggregate to obtain the fresh concrete include: mixing cement, slag powder, silica fume, waste rock powder, water reducing agent and water retaining agent according to the proportion in a concrete mixer for 2 to 5 minutes to mix them evenly, then adding all the water and stirring for 1 to 2 minutes to obtain a uniform slurry, and finally adding ferrochrome alloy slag aggregate and continuing to stir for 1 to 2 minutes to ensure that the slurry is evenly coated on the surface of the aggregate to obtain the fresh concrete.

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