阅读说明：本技术 一种蒸养碱激发矿渣混凝土及其制备方法 (Steam-cured alkali-activated slag concrete and preparation method thereof ) 是由 于琦 万小梅 刘桂宾 朱亚光 张思雨 王腾 赵铁军 王玉璞 许冬 于 2021-06-17 设计创作，主要内容包括：本发明属于建筑材料技术领域,涉及一种蒸养碱激发矿渣混凝土及其制备方法,在高寒地区工程中应用时,蒸养时间缩短了1-2小时,不仅可以利用强度高、抗冻性好和抗氯离子侵蚀性能强的特点,提升构件的质量,适应极端气候条件,还可以解决成型养护时间和施工周期长的问题,缩短构件的蒸养、拆模时间,大幅增加模具周转率,缩短施工周期,缓解冬季施工带来的不利影响；同时,掺入20-30％的粉煤灰取代矿渣,采用蒸养制度有效解决了碱激发混凝土收缩开裂的问题；另外,不使用水泥制备混凝土大大降低了能源消耗和碳排放量,节能环保,采用机制砂取代河砂,降低了自然资源的使用量,节约了生产成本,对建筑业的健康、可持续发展具有重要的意义。(The invention belongs to the technical field of building materials, and relates to steam-cured alkali-activated slag concrete and a preparation method thereof, wherein when the steam-cured alkali-activated slag concrete is applied to engineering in alpine regions, the steam-cured time is shortened by 1-2 hours, the characteristics of high strength, good frost resistance and strong chloride ion corrosion resistance can be utilized, the quality of a member is improved, extreme climatic conditions are adapted, the problems of long molding and curing time and long construction period can be solved, the steam-cured and formwork-removing time of the member is shortened, the turnover rate of a mold is greatly increased, the construction period is shortened, and adverse effects caused by construction in winter are relieved; meanwhile, 20-30% of fly ash is doped to replace slag, and the problem of shrinkage cracking of alkali-activated concrete is effectively solved by adopting a steam curing system; in addition, the concrete prepared without cement greatly reduces energy consumption and carbon emission, saves energy and protects environment, and the machine-made sand is adopted to replace river sand, thereby reducing the usage amount of natural resources, saving production cost and having important significance for the healthy and sustainable development of the building industry.)

1. The steam-cured alkali-activated slag concrete is characterized in that raw materials comprise an exciting agent, slag, fly ash, coarse aggregate and fine aggregate.

2. The steam-cured alkali-activated slag concrete according to claim 1, wherein the mass ratio of the exciting agent to the slag to the fly ash to the coarse aggregate to the fine aggregate is 71: 119: 30: 259: 239.

3. the steam-cured alkali-activated slag concrete according to claim 1 or 2, wherein the activator is water glass having a modulus of 1.8 or 2.0.

4. The steam-cured alkali-activated slag concrete according to claim 1 or 2, wherein the slag grade is S95, the water content is 0.5%, and the density is 2.83g/cm³Specific surface area of 422m²Per kg, loss on ignition < 0.1%, activity index 97%.

5. The steam-cured alkali-activated slag concrete according to claim 1 or 2, wherein the fly ash is of class II grade, has a water content of 0.5%, a fineness of 21.9%, a water demand ratio of 99%, a loss on ignition of 5.9%, and an activity index of 78%.

6. The steam-cured alkali-activated slag concrete according to claim 1 or 2, wherein the coarse aggregate is crushed stone of 5-25mm continuous gradation.

7. The steam-cured alkali-activated slag concrete according to claim 1 or 2, wherein the fine aggregate is continuous graded machine-made sand, the water content is 2%, and the fineness modulus is 2.9.

8. A preparation method of steam-cured alkali-activated slag concrete is characterized by comprising the following process steps:

wetting the coarse aggregate, rinsing the chamber of the stirrer, and weighing 3kg of slag;

according to the set mixing proportion, firstly adding coarse aggregate and fine aggregate in a stirrer for stirring, then adding slag and fly ash for stirring, and finally adding an alkali activator for stirring;

and (3) filling a mold, leveling, covering with a preservative film, standing for 1h in an indoor environment, then placing in a steam curing box, heating to 60 ℃ at a temperature not higher than 15 ℃/h, keeping the temperature for 2h, cooling at a temperature not higher than 15 ℃/h, taking out the mold after cooling to room temperature, and placing in a standard curing room for curing for 1d to obtain the steam-cured alkali-activated slag concrete.

9. The method for preparing steam-cured alkali-activated slag concrete according to claim 8, wherein the stirring time for adding the coarse aggregate and the fine aggregate is 60 s; adding the slag and the fly ash, and stirring for 60 s; the stirring time for adding the alkali activator is 90 s.

10. The method for preparing steam-cured alkali-activated slag concrete according to claim 8, wherein the temperature of a standard curing room is 20 ± 2 ℃ and the relative humidity is more than 95%.

The technical field is as follows:

the invention belongs to the technical field of building materials, and relates to steam-cured alkali-activated slag concrete and a preparation method thereof, which are applied to building engineering in alpine regions.

Background art:

extreme environmental conditions in alpine regions: the concrete curing agent has the advantages of high altitude, low air pressure, low air temperature and large day and night temperature difference, has a plurality of adverse effects on the curing of concrete, reduces the mechanical property of the concrete, has more remarkable effects on the concrete of 28d or more age, and simultaneously has remarkably reduced durability, and the concrete is frozen and thawed for many times before being hardened in a severe cold area for a long time at an early stage to generate internal defects, so that the strength and the durability of the concrete are reduced. In addition, because of the weather of ice and snow, the deicing salt widely used on the bridge deck of the traffic route enables the concrete to be easily corroded by chloride ions, and the damage of the concrete structure is aggravated. In the prior art, concrete applied to alpine regions generally has the problems of long forming and curing time and construction period, insufficient mechanical property and salt freezing resistance and the like, brings many adverse effects to winter construction of the alpine regions, and in addition, raw materials mostly adopt natural resources such as river sand and the like, and brings certain burden to the natural resources.

In addition, the building industry belongs to the important pillar industry and is an important force for promoting the development of the economic society, and the traditional building materials generally have the serious problems of high energy consumption, serious environmental pollution, shortage of natural resources and the like: the forecast of the energy consumption of the building is 2042 years in the year of peak-to-year peak value, the peak-to-peak value of the building is 12.18 hundred million tons of standard coal, the forecast of the carbon emission of the building is 2039 years in the year of peak-to-peak value, and the peak-to-peak value of the building is 24.11 hundred million tons of carbon dioxide. The resource utilization of solid waste is also a social concern to be solved urgently, sodium silicate alkali mud is industrial residue discharged after sodium silicate is produced, belongs to high-alkali waste residue, is discharged by about 400 plus one ton every year, and is about 500 ten thousand tons due to the lack of an effective recycling way, most of alkali mud is conveyed to a storage yard, so that alkali in the alkali mud is easy to permeate underground, soil water pollution is caused, and the environmental safety is threatened.

The alkali-activated cementing material is a hydraulic novel inorganic non-metallic cementing material which is generated by taking industrial waste such as ground blast furnace slag, fly ash, electric heating phosphorus slag and the like or natural minerals such as volcanic ash and the like as potential cementing material components and taking an alkali compound or alkali-containing industrial waste residue as an activator through reaction, has the characteristics of quick hardening, early strength, environmental protection and the like, expands the application range of the hydraulic cementing material, and is concerned in the field of building materials. Compared with the common Portland cement (P.O), the alkali-activated cementing material has the advantages of simple preparation process, no need of firing, low energy consumption, low cost, wide market, better mechanical property and more outstanding durability, and is considered as a green sustainable development cementing material with the highest development potential in the 21 st century. However, the hydration products of the alkali slag cement and the ordinary portland cement have difference, and the slag concrete excited by the water glass is easy to shrink and crack, which brings great difficulty to engineering construction.

The Chinese patent 201910835458.1 discloses a method for preparing steam-cured alkali-activated cement, which comprises mixing industrial alkali, limestone and sodium potassium aluminosilicate, grinding to fineness of 100 mesh, calcining at 1250-1350 deg.C in oxidizing atmosphere, quenching to obtain dry clinker, grinding to fineness of 200 mesh with less than or equal to 10% of screen residue, and mixing with sodium silicate to obtain cement; the potassium sodium aluminosilicateThe raw material is chemical composition necessarily containing SiO₂、Al₂O₃、Na₂O and/or K₂Solid matter of O, which is required to oxidize and calcine at 1100 ℃, SiO in the residue₂+Al₂O₃+Na₂O+K₂The mass ratio of O + CaO + MgO is not less than 95.0%, and the content of SiO in the mixture₂+Al₂O₃+Na₂O+K₂In the total mass of O + CaO + MgO, the contents of all components are respectively CaO: 0-5.0%, MgO: 0-2.0% of SiO₂：50.0-75.0％，Al₂O₃：15.0-35.0％，Na₂O+K₂O: 5.0 to 11.0 percent; the industrial alkali refers to caustic soda and/or calcined soda, and the content of the industrial alkali is Na₂The mass ratio of O to the potassium sodium aluminosilicate raw material after being oxidized and calcined at 1100 ℃ is 0-2.0%; the sodium silicate is water-soluble SiO₂And Na₂O as a raw material in an amount of SiO contained₂+Na₂The mass of O is 3.0-12.0% of clinker powder, the modulus of sodium silicate is 1.0-3.2, and the prepared cement has the characteristics of quick hardening, high strength, wide raw materials, low cost, low consumption, low carbon emission, stable and easily-controlled performance and the like.

Based on higher requirements of severe cold regions on various performances and construction conditions of concrete, particularly frost resistance and chloride ion corrosion resistance of high-strength concrete, the high-strength and high-durability concrete suitable for winter construction in severe cold regions is developed, and the method has important significance for constructional engineering in severe cold regions.

The invention content is as follows:

the invention aims to overcome the defects in the prior art and seek to design a steam-cured alkali-activated slag concrete and a preparation method thereof.

In order to achieve the purpose, the raw materials of the steam-cured alkali-activated slag concrete comprise an exciting agent, slag, fly ash, a coarse aggregate and a fine aggregate, wherein the mass ratio of the exciting agent to the slag to the fly ash to the coarse aggregate to the fine aggregate is 71: 119: 30: 259: 239; wherein the excitant is water glass with the modulus of 1.8 or 2.0; the slag was rated S95, had a water content of 0.5% and a density of 2.83g/cm³Specific surface area of 422m²Kg, loss on ignition < 0.1%, activity index 97%; the grade of the fly ash is II, the water content is 0.5%, the fineness is 21.9%, the water demand ratio is 99%, the loss on ignition is 5.9%, and the activity index is 78%; the coarse aggregate is crushed stone with 5-25mm continuous gradation; the fine aggregate is machine-made sand with continuous gradation, the water content is 2 percent, and the fineness modulus is 2.9.

The steam-cured alkali-activated slag concrete has the advantages that the machine-made sand replaces river sand by 60 percent, the fly ash and slag replace cement in the cementing material by 100 percent, the consumption of the river sand and the cement is greatly reduced, the cost of each concrete is reduced by 40 yuan, and the saving ratio is 6.7 percent; meanwhile, the method reduces the environmental pollution and resource waste, accords with the policy of resource utilization, and has important significance for promoting the low-carbon sustainable development of the building industry and building a conservation-oriented and environment-friendly society.

The invention relates to a preparation method of steam-cured alkali-activated slag concrete, which comprises the following process steps:

wetting the coarse aggregate by using a spraying kettle, weighing 3kg of slag, and rinsing the chamber of the stirrer;

according to the set mixing proportion, firstly adding coarse aggregate and fine aggregate in a stirrer, stirring for 60s, then adding slag and fly ash, stirring for 60s, and finally adding an alkali activator, and stirring for 90 s;

filling a mold by using a vibration method, leveling, covering a preservative film, standing for 1h in an indoor environment, then placing in a steam curing box, heating to 60 ℃ at a temperature not higher than 15 ℃/h, keeping the temperature for 2h, cooling at a temperature not higher than 15 ℃/h, taking out after cooling to room temperature, removing the mold, and placing in a standard curing room with the temperature of 20 +/-2 ℃ and the relative humidity of more than 95% for curing for one day to obtain the steam-cured alkali-activated slag concrete.

Compared with the prior art, when the method is applied to engineering in alpine regions, the steam curing time is shortened by 1-2 hours, the characteristics of high strength, good frost resistance and strong chloride ion corrosion resistance can be utilized, the quality of the member is improved, the method is suitable for extreme climatic conditions, the problems of forming and curing time and long construction period can be solved, the steam curing and mold stripping time of the member is shortened, the mold turnover rate is greatly increased, the construction period is shortened, and the adverse effect brought by winter construction is relieved; meanwhile, 20-30% of fly ash is doped to replace slag, and the problem of shrinkage cracking of alkali-activated concrete is effectively solved by adopting a steam curing system; in addition, the concrete prepared without cement greatly reduces energy consumption and carbon emission, saves energy and protects environment, and the machine-made sand is adopted to replace river sand, thereby reducing the usage amount of natural resources, saving production cost and having important significance for the healthy and sustainable development of the building industry.

Description of the drawings:

FIG. 1 is a schematic view showing the change of the compressive strength of a test piece according to the present invention with time.

FIG. 2 is a schematic view showing the change of shrinkage with time of a test piece according to the present invention.

The specific implementation mode is as follows:

the invention is further described below by way of an embodiment example in conjunction with the accompanying drawings.

Example 1:

the raw materials of the steam-cured alkali-activated slag concrete related to the embodiment comprise an exciting agent, slag, fly ash, coarse aggregate and fine aggregate; the mass percentage of the fly ash is 20-30%; the fine aggregate is machine-made sand, the machine-made sand is used for replacing river sand which belongs to non-renewable resources, and is a necessary means for protecting natural resources, and the water content of the machine-made sand has great influence on the mechanical property and the durability of the steam-cured alkali-activated slag concrete, so that the water content of the machine-made sand is preferably 2%.

The preparation method of the steam-cured alkali-activated slag concrete related to the embodiment comprises the following process steps:

the coarse aggregate is wetted by using a spray kettle to achieve a saturated surface drying effect, because the coarse aggregate has high water absorption rate and can absorb water in the mixing process, the difference between the actual water consumption and the water consumption in the mixing proportion is large due to excessive water absorption, an error is generated,

3kg of slag was weighed out,

rinsing the chamber of the stirrer to prevent part of slurry from adhering to the inner wall of the stirrer in the stirring process to cause insufficient slurry;

according to the set mixing proportion, firstly adding coarse aggregate and fine aggregate in a stirrer and stirring for 60s, then adding slag and fly ash and stirring for 60s, and finally adding an alkali activator and stirring for 90 s;

filling a mold by using a vibration method, leveling, covering a preservative film, standing for 1 hour in an indoor environment, then placing in a steam curing box, adjusting the standing time according to the air temperature, wherein the lowest temperature of a standing area is not lower than 5 ℃, the heating speed of the steam curing box is not higher than 15 ℃/h, keeping the temperature for 2 hours after the temperature is raised to 60 ℃, cooling the temperature, the cooling speed is not higher than 15 ℃/h, taking out the mold after the temperature is reduced to the room temperature, removing the mold, and placing in a standard curing room with the temperature of 20 +/-2 ℃ and the relative humidity of more than 95% for curing for one day.

In this example, the steam cured test piece and the control test piece cured at room temperature for 24 hours are placed in a standard curing room to be cured for a corresponding age period to perform a comparative test:

the size of the test piece for the compressive strength test is 100mm multiplied by 100 mm; the frost resistance test is carried out by adopting a quick freezing method, the size of a test piece is 100mm multiplied by 400mm, and the variation of the elastic modulus and the quality is used for representing the frost resistance of the concrete; the size of the concrete dry shrinkage test piece is 100mm multiplied by 515 mm; the concrete chlorine ion penetration resistance test adopts three test methods of an alternating current resistivity method, an electric flux method and an RCM method, the diameter of a test piece is 100 +/-1) mm, and the height is 50 +/-2 mm;

the formulation of the test specimens is shown in the following table:

and (3) test results:

1. mechanical properties

The 1 day, 3 day, 7 day and 28 day strengths of the test specimens are indicated by the following scale:

the change of the compressive strength of the test specimen with time is shown in figure 1, and it can be known that the 1d compressive strength of the steam-cured test specimen (7-I, 7-II and 8-III) is 80% of the 28d compressive strength after the steam curing at 60 ℃, so that the steam curing and the form removal time are greatly shortened, the turnover rate of the mold is increased, and the production efficiency is improved; the early-stage compressive strength of the control test pieces (7-III, 8-I and 8-II) is lower, the 1d compressive strength is less than 10MPa, but the increase is faster, and the 7d compressive strength is 80% of the 28d compressive strength; under the same conditions, the excitation intensity of the 2.0 modulus water glass is about 20 percent higher than that of the 1.8 modulus water glass; the compression strength of the blended fly ash is reduced to a certain degree.

2. Freezing resistance

The anti-freezing performance test method is carried out according to a quick freezing method in GB/T50082-2009 test method standards for long-term performance and durability of common concrete, the anti-freezing performance of the concrete is represented by measuring mass loss rate and relative dynamic elastic modulus after 50 times, 100 times, 125 times, 150 times, 175 times and 200 times of freeze-thaw cycles, and test results are shown in the following table:

therefore, after 200 times of freeze-thaw cycles, each test piece meets the standard requirements that the mass loss rate is less than or equal to 5% and the relative dynamic elasticity is not less than 60%, and the freezing resistance is good; compared with the control test piece cured at room temperature, the decrease speed of the mass loss rate of the steam-cured test piece after being steamed at 60 ℃ is obviously less than that of the test piece cured at room temperature, and the decrease speed of the relative dynamic elasticity is also less than that of the test piece cured at room temperature. Meanwhile, under the same freeze-thaw cycle times, the mass loss of the test piece after the steam curing at 60 ℃ is less than that of the test piece cured at room temperature, and the relative dynamic elastic modulus is greater than that of the test piece cured at room temperature. As can be seen, the frost resistance of the alkali-activated test piece after steam curing is obviously improved; under the same condition, the frost resistance of the steam-cured test piece is reduced by doping the fly ash, and the result is consistent with the compression strength result.

3. Drying shrinkage performance

The results of the drying shrinkage test are given in the following table:

as shown in fig. 2, it is understood that the early dry shrinkage of the steam-cured specimen is large, and the dry shrinkage gradually becomes gentle as the age increases. The shrinkage rates of the three groups of 7-I, 7-II and 8-III of steam-cured test pieces are obviously smaller than those of other three groups of control test pieces, the drying shrinkage is smaller, and the improvement of the curing temperature is favorable for reducing the early shrinkage of the steam-cured test pieces; when curing is performed at 60 ℃, the dry shrinkage of the steam-cured test piece increases with the increase of the modulus of the water glass, because the hydration products C-S-H gel of the alkali-activated slag increases with the increase of the modulus, and the gel pores increase, resulting in the increase of dry shrinkage.

4. Resistance to chloride ion permeation

The chlorine ion permeability resistance of the steam-cured test piece was measured by an alternating current resistivity method, an electric flux method and an RCM method for resistivity, electric flux and chloride ion mobility coefficient, respectively, and the results are shown in the following table:

it can be known that the three test methods all show that after the steam-cured test piece is subjected to steam curing at 60 ℃, the structure is more compact, and the chlorine ion permeability resistance is better.

The steam-cured alkali-activated slag concrete provided by the embodiment provides an alkaline environment for the interior of concrete, is beneficial to generation of a passivation film on the surface of a reinforcing steel bar, slows down corrosion of the reinforcing steel bar, improves chloride ion permeability resistance, carbonization resistance and corrosion resistance of the concrete, is applied to alpine regions, effectively improves the problems of forming and curing time and long construction period by utilizing the characteristics of quick hardening, early strength and the like of the alkali-activated concrete, shortens the steam curing and mould removing time of a component, greatly increases the turnover rate of a mould, relieves adverse effects caused by construction in winter, and improves the production efficiency; the alkali excites the activity effect of the mineral admixture, so that the structural porosity can be reduced, and the density of concrete is improved; machine-made sand is used for replacing river sand, fly ash is used for partially replacing slag, a steam curing mechanism is used for curing, the working performance, the mechanical property, the freezing resistance and the chloride ion corrosion resistance of concrete are effectively improved, shrinkage cracking of alkali-activated concrete is reduced, and the concrete effectively responds to the situationExtreme conditions in alpine regions; meanwhile, the construction and production cost is reduced, and the environmental pollution and CO are reduced₂The green reduction engineering application is realized.

Compared with the common high-strength concrete applied to the alpine regions, the steam-cured alkali-activated slag concrete has good mechanical properties, better frost resistance and chloride ion permeability resistance, can improve the adverse effects on engineering construction caused by extreme conditions of low temperature and wide distribution of saline soil in the alpine regions, improves the drying shrinkage performance of the alkali-activated concrete, can prolong the service life of a concrete structure, greatly reduces the maintenance cost, has high early strength, can meet the requirement on mechanical properties due to the one-day mold removal strength, greatly shortens the construction period in winter, improves the production efficiency, and reduces the construction cost.