CN115650645A - Fly ash-slag powder based geopolymer concrete mix proportion design method - Google Patents
Fly ash-slag powder based geopolymer concrete mix proportion design method Download PDFInfo
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Abstract
A design method of a mixing proportion of a pulverized fuel ash-slag powder based geopolymer concrete comprises the following steps of (1) determining the compressive strength and the slump value of the geopolymer concrete according to engineering requirements; (2) determining the total dosage of the alkali-activator; (3) Determining the molar concentration of a sodium hydroxide solution in an alkaline activator and the ratio of a sodium silicate solution to the sodium hydroxide solution; (4) Determining the proportion of slag powder and fly ash in the silicon-aluminum raw material; (5) Determining the proportion of the dosage of the alkali activator to the dosage of the silicon-aluminum raw material, namely the alkali-glue ratio; (6) determining the proportion between coarse and fine aggregates; (7) Determining the use amounts of two silicon-aluminum raw materials of fly ash and slag powder; (8) Determining the dosage of sodium hydroxide solution and sodium silicate solution in the alkaline excitant; (9) determining the dosage of the water reducing agent; (10) determining the use amount of coarse and fine aggregates; and (11) calculating the amount of each component of the geopolymer concrete. The invention meets the strength requirements of various projects on materials, and is beneficial to popularization of application of geopolymer concrete.
Description
Technical Field
The invention relates to the field of building materials, in particular to a design method of a fly ash-slag powder based geopolymer concrete mixing proportion.
Background
The amount of concrete consumed worldwide is as high as several billion tons every year, and concrete remains one of the largest building materials in the field of civil engineering. 1m per production 3 The concrete needs to consume a large amount of cement, the use amount of the cement is over 42 hundred million tons in 2018, and the trend is obvious increase. Carbon dioxide released during cement manufacturing accounts for about 5% to 7% of the total carbon dioxide emissions, and is considered to be a significant cause of accelerated global warming. On the other hand, industrial production discharges a large amount of solid waste, such as fly ash from thermal power plants, slag powder from the steel industry, tailings from the mineral industry, and the like, every year. Therefore, finding building materials to replace cement and disposing of solid waste with reasonable technical means are two challenges facing current researchers. At present, a feasible solution is to use geopolymer concrete instead of cement-based concrete, and the use of geopolymer concrete can not only reduce or even avoid the use of cement, but also promote the resource utilization of industrial solid wastes.
Geopolymers are binding materials obtained by reacting an alkaline activator with a silica-alumina-rich raw material, and the concept was first proposed by the french scholars Davidovits. Adding alkali activator into the silicon-aluminum raw material, and opening silicate and aluminateThe dissolved silicate ions and aluminate ions form silicon-oxygen tetrahedral monomer (SiO) after undergoing diffusion, orientation and polycondensation processes 4 ]And tetrahedral aluminum oxide monomer [ AiO ] 4 ]The polymer monomers form a high molecular polymer with a three-dimensional structure after polycondensation reaction. The reaction process of geopolymers is called geopolymerization, which usually takes place at normal or high temperatures. The alkali activator is usually composed of an alkali metal hydroxide (NaOH, KOH, etc.) and an alkali metal silicate (Na) 2 SiO 3 And K 2 SiO 3 Etc.) are mixed.
The geopolymer concrete has the advantages of high early strength, high temperature resistance, sulfate corrosion resistance, small drying shrinkage and the like, and has wide application prospect in a plurality of fields such as manufacturing ultrahigh-strength materials, fireproof materials, engineering repair materials and the like. Although geopolymer concrete has so many advantages and broad prospects, the whole is still in the laboratory research stage and is not widely applied to actual engineering. One problem that has been severely limiting the development and use of geopolymer concrete is that the design methods for geopolymer concrete mix ratios remain limited. The performance of geopolymer concrete is affected by various factors, such as the molar concentration of NaOH, the modulus of water glass, the curing temperature, the curing age, the amount of water used, the type of silica-alumina raw material, the stirring method and the stirring time, and the like, which make the mixing ratio process of geopolymer concrete very complicated. Scholars and engineers at home and abroad have conducted a lot of research work in the preparation of geopolymer concrete, and various silicon-aluminum raw materials such as fly ash, metakaolin, rice hull ash, red mud, slag powder and tailings are used at the same time. However, most of the mix proportion designs for preparing geopolymer concrete are based on experience, on one hand, the mix proportion does not consider the specific gravity of raw materials and the amount of aggregate is fixed, and on the other hand, most of the mix proportions lack standardized or normalized design procedures, do not consider the influence of the aggregate gradation and the amount of the alkaline activator on the performance of geopolymer concrete, and cannot be adjusted or designed according to expected mechanical performance requirements, which is also a common problem of the geopolymer concrete preparation methods in a large number of patents at present. Therefore, it is necessary to provide a geopolymer mix design method that can be easily followed to adjust the strength according to the engineering requirements and meet the working performance.
In addition, if the geopolymer concrete is prepared by only using the fly ash as the silicon-aluminum raw material, a curing mode of high-temperature curing is required to reduce the setting time, and the strength of the obtained geopolymer concrete is low, so that the popularization and the use of the geopolymer concrete are very unfavorable. A large number of researches show that the addition of the slag powder in the fly ash can effectively shorten the setting time and obviously improve the compressive strength. In addition, for common concrete, the compressive strength of the concrete is mainly determined by the water-cement ratio (mass ratio of water to the cementing material), and is less influenced by other factors, so that most of the mix proportion specifications of the concrete at home and abroad determine the water-cement ratio according to the compressive strength of the common concrete.
Disclosure of Invention
The method comprises the steps of considering the influence of slag powder on the performance of geopolymer concrete and the theory of the mixing proportion of common concrete, taking the slag powder and the fly ash as silicon-aluminum raw materials, taking a mixed solution of a sodium hydroxide solution and a sodium silicate solution as an alkaline activator, adjusting the compressive strength by establishing the equivalent relationship between the mass ratio and the water-to-glue ratio of the alkaline activator and the silicon-aluminum raw materials, optimizing the aggregate gradation, and calculating the using amount of each component by adopting an absolute volume method.
By using the idea of JGJ55-2011 common concrete mix proportion design rule for reference, the geopolymer concrete mix proportion design method provided by the invention is clear in idea and easy to follow, can meet the strength requirements of numerous projects on materials, is beneficial to popularization of application of geopolymer concrete, further replaces cement-based concrete, and reduces CO 2 The discharge of the solid waste is accelerated, and the resource utilization process of the solid waste is accelerated.
The technical scheme adopted by the invention is as follows:
the raw material used for the fly ash-slag powder based geopolymer concrete consists of coarse aggregate, fine aggregate, fly ash, slag powder, water, metal hydroxide solution, metal silicate solution and water reducing agent.
A design method for a mixing proportion of fly ash-slag powder based geopolymer concrete adopts an absolute volume method to calculate the dosage of each component:
(1) And determining the compressive strength and the slump value of the geopolymer concrete according to engineering requirements.
(2) Determining the total dosage of the alkali-activating agent: the alkaline activator is the most expensive component in all raw materials for preparing geopolymer concrete, and the single dosage of the alkaline activator is selected to be 190-210kg in order to reduce the production cost of the geopolymer concrete and ensure the workability of fresh concrete. Table 1 shows the recommended single dosage of the alkali-activator under the maximum particle size of two different coarse aggregates, wherein the coarse aggregates are broken stones; the concrete dosage of the alkaline activator is determined after the slump of the fresh concrete is selected according to factors such as the type of components, the application occasion, the environmental condition, the spacing between reinforcing steel bars and the like in the actual engineering. It should be noted that table 1 is applicable to geopolymer concrete, and the alkali-binder ratio (ratio of the amount of the alkali activator to the amount of the silica-alumina raw material) is in the range of 0.3 to 0.7; when the alkali-cement ratio is more than or equal to 0.7, the slump of the geopolymer concrete mixture prepared by adopting the dosage of the alkali activator in the following table is more than 70mm, because when the alkali-cement ratio is larger, the dosage of powder materials is less, the water demand is correspondingly reduced, and the slump of the geopolymer concrete mixture is increased; for geopolymer concrete with the glue reducing ratio of more than or equal to 0.7, 190kg of single dosage of the alkaline activator is selected to ensure the strength performance of the geopolymer.
TABLE 1 recommended single dosage of alkali activator for two different coarse aggregates with maximum particle size
(3) Determining the molar concentration of the sodium hydroxide solution in the alkaline activator and the ratio of the sodium silicate solution to the sodium hydroxide solution: the molar concentration of the sodium hydroxide solution and the ratio between the sodium silicate solution and the sodium hydroxide solution have an important influence on the geopolymeric concrete performance, and the optimum sodium hydroxide solutionThe molar concentration of the solution and the ratio of the sodium silicate solution to the sodium hydroxide solution can change along with the chemical composition of the silicon-aluminum raw material; thus, the molar concentration of the sodium hydroxide solution is selected to be 13-15M, the modulus of the sodium silicate solution is 2.9-3.4, and the ratio between the sodium silicate solution and the sodium hydroxide solution is 1.4-1.6; the range of main oxide components of the silicon-aluminum raw material is as follows: siO 2 2 42% -58% of Al 2 O 3 22% -30% of CaO and Fe 2 O 3 15 to 21 percent. Only when the oxide component of the silica-alumina raw material is within this range, the compressive strength of the geopolymer can be ensured by the gel product formed by the reaction of the alkaline activator and the silica-alumina raw material.
(4) Determining the proportion of slag powder and fly ash in the silicon-aluminum raw material: the silicon-aluminum raw material consists of slag powder and low-calcium fly ash, wherein the slag powder is S95 or S105 slag powder, and the specific surface area of the slag powder is required to be more than 400m 2 The dosage of the silicon-aluminum raw material is 27 to 33 percent of the total amount of the silicon-aluminum raw material; the fly ash is first-grade or second-grade low-calcium fly ash, and the using amount of the fly ash is 67-73% of the total amount of the silicon-aluminum raw material. The ratio of main oxide components in the silicon-aluminum raw material can be calculated according to formula 1:
equation 1,c = a · F c +(1-a)·S c ；
In the formula: c is the percentage of certain oxide component in the silicon-aluminum raw material; a is the proportion of the fly ash in the silicon-aluminum raw material; f c Is the percentage of the oxide component in the fly ash; s c Is the percentage of this oxide component in the slag powder. Once the oxide component ratio calculated according to the use amounts of the fly ash and the slag powder exceeds the specified range of the oxide, the use amounts of the fly ash and the slag powder are adjusted to ensure that the oxide component ratio meets the specified range;
preferably, the slag powder accounts for 30% of the silicon-aluminum raw material, and the fly ash accounts for 70% of the silicon-aluminum raw material; the silicon-aluminum raw material consists of 30% of slag powder and 70% of fly ash, and the reaction of the silicon-aluminum raw material and the alkaline activator in the proportion is favorable for improving the compressive strength of geopolymer concrete.
(5) Determining the proportion of the dosage of the alkali activator to the dosage of the silicon-aluminum raw material, namely the alkali-glue ratio: the method simulates the principle that the concrete strength is controlled by a water-to-cement ratio in JGJ55-2011 'design rule for mix proportion of common concrete', replaces the water-to-cement ratio with the ratio of an alkaline activator to a silicon-aluminum raw material, determines the 28d compressive strength of geopolymer concrete by changing the ratio of the alkaline activator to the silicon-aluminum raw material, and for convenience of description, the ratio of the alkaline activator to the silicon-aluminum raw material is simply referred to as the alkali-to-cement ratio. Equation 2 gives the relationship between the alkali-cement ratio and the 28-day compressive strength of geopolymer concrete (see FIG. 2):
in the formula 2, the first and second groups,
the modification of equation 2 is
In the formula: f. of cu,0 Is the 28-day compressive strength of geopolymer concrete cubes (cube size 150 mm), MPa; AAC/CM is the ratio of alkali to gum. Calculating the alkali-cement ratio according to the compressive strength of the geopolymer concrete by using a formula 2; it should be noted that equation 2 is applicable to the formulation of geopolymer concrete with compressive strength grade C30-C65.
(6) Determining the proportion of coarse and fine aggregates: the optimized coarse and fine aggregate gradation has the effects of reducing the gaps among aggregates, reducing the use amount of net slurry, reducing the manufacturing cost, increasing the strength of concrete and the like; in order to reduce the gaps among coarse and fine aggregates as much as possible so as to achieve the 'tightest state' of an aggregate framework, the aggregate gradation is optimized by adopting the following steps: firstly, selecting a plurality of volume proportions of coarse aggregates and fine aggregates, and uniformly mixing the coarse aggregates and the fine aggregates according to the selected proportions; then filling the mixed aggregate into a cylindrical measuring container for three times, tamping and compacting the mixed aggregate after each time of filling, wherein a tamping rod does not need to touch the bottom of the container and the top surface of the tamped aggregate on the previous layer in the tamping and inserting process, calculating the density and the void ratio of the mixed aggregate, and determining that the volume of the fine aggregate is r times of the total volume of the aggregate and the volume of the coarse aggregate is (1-r) times of the total volume of the aggregate according to the principle of maximum density and minimum void ratio; generally, the sand ratio (the mass of sand as a percentage of the total mass of the sand) is preferably controlled to be between 33% and 45%.
(7) Determining the use amounts of two silicon-aluminum raw materials of fly ash and slag powder: the total amount of the silicon-aluminum raw material (composed of fly ash and slag powder) is determined according to the alkali-binder ratio and the total amount of the alkali activator, and the value is calculated by a formula 3:
in the formula 3, the first and second phases,
in the formula: m is cm The dosage of the silicon-aluminum raw material in per cubic geopolymer concrete is kg; m is aac The dosage of the alkaline excitant in the geopolymer concrete per cubic meter is kg;
from the step (4), if the ratio of the fly ash to the silicon-aluminum raw material is α, the single-component usage amounts of the fly ash and the slag powder are determined by calculation according to the formulas 4 and 5:
formula 4,m fl ＝m cm ·α；
Equation 5,m sl ＝m cm ·(1-α)；
In the formula: m is fl The dosage of the fly ash in the geopolymer concrete per cubic meter is kg; m is sl Is the amount of slag powder in each cubic geopolymer concrete in kg.
(8) Determining the dosage of a sodium hydroxide solution and a sodium silicate solution in the alkaline activator: at present, the combination of sodium hydroxide solution and sodium silicate solution is one of the most common and widely accepted alkali activators, and the invention selects the mixed solution of the sodium hydroxide solution and the sodium silicate solution as the alkali activator; according to the step (3), the ratio of the sodium silicate solution to the sodium hydroxide solution is selected to be beta, namely, the dosage relation of the sodium silicate solution to the sodium hydroxide solution conforms to a formula 6 and a formula 7:
equation 6,m ss /m sh ＝β；
Equation 7,m aac ＝m ss +m sh ；
In the formula: m is ss The dosage of sodium silicate solution in per cubic geopolymer concrete is kg; m is sh For mixing polymers per cubicThe dosage of sodium hydroxide solution in the concrete is kg;
from equation 6 and equation 7, equation 8 can be derived:
equation 8,m aac ＝m sh ·(1+β)；
In combination with equations 7 and 8, the single usage of sodium hydroxide solution and sodium silicate solution is calculated by equations 9 and 10, respectively:
equation 9,m sh ＝m aac /(1+β)；
(9) Determining the dosage of the water reducing agent: compared with water, the alkaline activator is more viscous, the workability of geopolymer concrete can be reduced by adding the alkaline activator in the preparation process, and particularly when the alkali cement ratio is low, the workability of geopolymer concrete is poorer than that of cement-based concrete; the workability of the geopolymer concrete based on the fly ash-slag powder can be effectively improved by adding the naphthalene water reducing agent into the geopolymer concrete; the dosage of the naphthalene water reducer is determined according to the percentage of the water reducer in the silicon-aluminum raw material, when the alkali-glue ratio is 0.3-0.8, the dosage of the naphthalene water reducer is not more than 2.0% of the silicon-aluminum raw material, and the naphthalene water reducer is in a liquid type; when the mass ratio of the water reducing agent to the cementing material is gamma, calculating the single dosage of the water reducing agent according to a formula 11:
equation 11,m sp ＝m cm ·γ；
In the formula: m is a unit of sp The dosage of the water reducing agent in each cubic geopolymer concrete is kg.
(10) Determining the dosage of coarse and fine aggregates: the mixing proportion of the geopolymer concrete is designed by adopting an absolute volume method, and the total volume of the prepared geopolymer concrete is assumed to be 1m 3 Its volume satisfies equation 12:
equation 12, V agg +V fl +V sl +V sh +V ss +V sp +V air ＝1m 3 ；
In the formula: v agg M is the sum of the volumes of coarse and fine aggregates 3 ；V fl Is the volume of fly ash, m 3 ；V sl Is the volume of slag powder, m 3 ；V sh Volume of sodium hydroxide solution, m 3 ；V ss Volume of sodium silicate solution, m 3 ；V sp Is the volume of the naphthalene water reducer, m 3 ；V air Volume of air content, m 3 ；
Referring to JGJ55-2011 'design rule for mix proportion of common concrete', when the gas content in geopolymer concrete is not measured, V air The value is 1%. Thus, the total volume of the coarse and fine aggregate is calculated according to the following equations 13 and 14:
equation 13, V agg ＝0.99m 3 -V fl -V sl -V sh -V ss -V sp ；
In the case of the formula 14,
in the formula: ρ is a unit of a gradient fl Is the apparent density of the fly ash in kg/m 3 ；ρ sl Is the apparent density of slag powder, kg/m 3 ；ρ sh The density of the sodium hydroxide solution is kg/m 3 ；ρ ss Is the density of sodium silicate solution, kg/m 3 ；ρ sp The density of the naphthalene water reducer;
to obtain the total volume V of the aggregate agg And (5) calculating the single-component dosage of the fine aggregate by adopting a formula 15:
formula 15,m fag ＝r·V agg ·ρ fag ；
In the formula, m fag The dosage of the fine aggregate in each cubic geopolymer concrete is kg; rho fag Apparent density of fine aggregate in kg/m 3 ；
The single use amount of the coarse aggregate is calculated by formula 16:
formula 16,m cag ＝(1-r)·V agg ·ρ cag ；
In the formula: m is a unit of cag The dosage of the coarse aggregate in the geopolymer concrete per cubic meter is kg; rho cag Apparent density of coarse aggregate, kg/m 3 。
(11) Calculating the use levels of all components of the geopolymer concrete according to the steps (2) to (10), firstly, dry-mixing all solid components uniformly according to the use levels of all components, wherein the solid components comprise fly ash, slag powder, coarse aggregate and fine aggregate, stirring for 3 minutes, then adding an alkaline activator, continuing stirring for 4 minutes, finally adding a naphthalene water reducer, stirring for 3 minutes, and testing the geopolymer concrete mixture after ensuring uniform stirring; firstly, checking the working performance of geopolymer concrete mixture, then pouring the mixture into a mold of 150mm multiplied by 150mm, vibrating and molding the mold, then placing the mold in an environment with the temperature of 20 +/-2 ℃ for 1d, then removing the mold, placing a test block in an environment with the temperature of 20 +/-2 ℃ and the humidity of 95% for curing for 28d after removing the mold, and then testing the 28d compressive strength of the geopolymer concrete test piece; if the expected working performance and strength requirements are met, the preparation work of the geopolymer concrete is completed; if the expected requirements are not met, the adjustment strategy is as follows: the working performance of geopolymer concrete is controlled by adjusting the dosage of the water reducing agent, and the compressive strength of the geopolymer concrete is controlled by adjusting the alkali-cement ratio.
The invention has the beneficial effects that: aiming at the blindness of selecting materials when preparing geopolymer concrete in the prior art, the invention adjusts the workability and the strength performance of the geopolymer concrete by changing the dosage of an alkali activator and the alkali-binder ratio, optimizes the aggregate gradation according to the aggregate accumulation theory, and provides a normalized geopolymer concrete mix proportion design method capable of adjusting the material performance according to engineering requirements. Overall, the invention has the following advantages: (1) The relation between the maximum particle size of the coarse aggregate and the dosage of the alkaline activator under different slump is established, and the requirement of most projects on the workability of geopolymer concrete can be met; (2) The proper proportion range of the fly ash and the slag powder is determined, and the geological polymerization reaction of the silicon-aluminum raw material and the alkaline activator in the proportion range is favorable for improving the strength of geopolymer concrete, reducing the dosage of the alkaline activator and reducing the manufacturing cost; (3) The combined use of the fly ash and the slag powder allows the geopolymer concrete to be cured at room temperature, avoids the high-temperature curing limitation of the geopolymer concrete, and is beneficial to the popularization and application of the geopolymer concrete; (4) A relational expression of the alkali-binder ratio and the compressive strength of geopolymer concrete is established, the prepared strength meets the strength requirement of most of the current projects on the concrete, and meanwhile, the vacancy that the strength of the geopolymer concrete is difficult to adjust according to the project requirements at present is made up; (5) The geopolymer mix proportion design method has clear overall thought, simple design steps and easy following, avoids the waste of reverse sides such as materials, time, manpower and the like caused by repeated trial and matching, and has good practicability and operability.
Drawings
FIG. 1 is a flow chart of the geopolymer concrete mix proportion design of the present invention.
FIG. 2 is a graph showing the relationship between the alkali-binder ratio of the present invention and the 28-day compressive strength of geopolymer concrete.
Detailed Description
The invention will now be described in more detail with reference to a number of examples, which will first be given in the context of the raw materials used in the examples, all of which are commercially available. It should be noted that the end-of-range values and any values given herein are not limited to the precise range or value, and that such range or value should be a value close to such range or value.
The silicoaluminophosphate raw materials used in the examples include fly ash and slag powder. The fly ash is second-grade F-type low-calcium fly ash, and the apparent density of the fly ash is 2100kg/m 3 Specific surface area of 425m 2 Per kg; the slag powder is granulated blast furnace slag with the grade of S95 and the apparent density of 2850kg/m 3 Specific surface area of 451m 2 In terms of/kg. The chemical composition of the fly ash and the slag powder is shown in table 2.
TABLE 2 chemical composition of fly ash and slag powder
The alkaline activator isThe mixed solution of sodium hydroxide solution and sodium silicate solution. Wherein the sodium hydroxide solution is prepared by adding flake sodium hydroxide (NaOH) solid with purity of more than 99% into deionized water, and mixing, the molar concentration is 13M and 14M, and the apparent density is 1422kg/M 3 (ii) a The sodium silicate solution is water glass, and the molecular formula is Na 2 O·nSiO 2 ·mH 2 O, the water glass modulus n is SiO 2 With Na 2 The molar ratio of O, the original modulus of about 3.3, the baume degree of 40 and the apparent density of 1431kg/m 3 Chemical composition of 8.2% of Na 2 O and 26% SiO 2 . The mixed solution of the water glass solution and the sodium hydroxide solution is used as an alkali activator.
The fine aggregate is common water-washed river sand with particle size less than 4.75mm, fineness modulus of 2.74, and apparent density of 2612kg/m 3 The bulk density was 1601kg/m 3 (ii) a The coarse aggregate is continuous graded broken stone with particle size distribution range of 4.75-20 mm and apparent density of 2705kg/m 3 The bulk density is 1580kg/m 3 。
The additive is a high-efficiency naphthalene water reducing agent, is a brown viscous liquid, has the solid content of 40 percent and the apparent density of 1210kg/m 3 。
The mixing water is daily water.
Example 1: the concrete example is designed by taking the geopolymer concrete mixing ratio with the strength grade of C30 as an example, and the concrete implementation steps are as follows:
(1) Determining the working performance and the compressive strength grade requirement of geopolymer concrete: the 28d target compressive strength was set to 30MPa and the target slump was greater than 100mm.
(2) Determining the total dosage of the alkali-activating agent: considering the production cost, compressive strength and working performance comprehensively, the single dosage of the alkaline activator in the step (2) in the invention content is selected as m aac ＝190kg。
(3) The molar concentration of the sodium hydroxide solution in the alkali activator was selected to be 14M, and the ratio between the sodium silicate solution and the sodium hydroxide solution was 1.5.
(4) The silicon-aluminum raw material consists of 30 percent of S95 slag powder and 70 percent of fly ash which are combinedSiO in silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The ratio of the components is 45.1%, 29.7% and 19.0% respectively. SiO in the silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The proportions are all in an allowable range, so the proportion of the fly ash and the slag powder does not need to be changed.
(5) The 28d target compressive strength is set to be 30MPa, and the preparation strength of the geopolymer concrete can be calculated by referring to relevant regulations in JGJ 55-2011' design rule of mixing proportion of common concrete
f cu,0 ＝30+1.645×5＝38.2MPa
The alkali-to-gel ratio results can be calculated according to the variant of equation 2 as follows:
in the formula 2, the first and second groups,
(6) Determining the proportion between the coarse aggregates: according to the step (6) in the summary of the invention, when the volume of the fine aggregate is 42% of the total volume of the aggregate and the volume of the coarse aggregate is 58% of the total volume of the aggregate, the bulk density of the aggregate is the largest and the void ratio is the smallest, and the skeleton of the aggregate is in the most 'compact state', i.e. r =0.42 and the sand ratio is about 41.2%.
(7) Determining the usage amount of the fly ash and the slag powder. According to the formula 3, the single use amount of the silicon-aluminum raw material is determined as follows:
in the case of the formula 3,
from the step (4), the proportion of the fly ash in the silicon-aluminum raw material is 70%, and the single-component usage amount of the fly ash is determined by calculation according to the formula 4:
formula 4,m fl ＝m cm ·α＝257×0.7≈180kg；
Determining the single formula dosage of the slag powder according to the formula 5:
equation 5,m sl ＝m cm ·(1-α)＝257×0.3≈77kg。
(8) Determining the dosage of a sodium hydroxide solution and a sodium silicate solution in the alkaline activator:
as can be seen from step (3), the ratio between the sodium silicate solution and the sodium hydroxide solution is 1.5, i.e. β =1.5, and the single dosage of the sodium hydroxide solution is determined according to the following formula 9:
equation 9,m sh ＝m aac /(1+β)＝190/(1+1.5)＝76kg
The single use amount of the sodium silicate solution is determined according to the following formula 10:
(9) Determining the dosage of the water reducing agent: as can be seen from the step (3) in the summary of the invention, when the alkali-cement ratio is greater than 0.6, the slump of the geopolymer concrete mixture generally exceeds 70mm, and in combination with the slump test of the geopolymer concrete mixture, it is finally found that, in the case of not adding a naphthalene water reducer, the geopolymer concrete mixture with the alkali-cement ratio of 0.74 has a larger slump value, and therefore, the mass ratio of the water reducer to the cementitious material is determined to be γ =0;
the single formula dosage of the water reducing agent is determined according to the following formula 11:
equation 11,m sp ＝m cm ·γ＝0。
(10) Determining the dosage of coarse and fine aggregates: the invention adopts an absolute volume method to design the mixing proportion of the geopolymer concrete, and the total volume of the prepared geopolymer concrete is 1m in calculation 3 In addition, since the gas content in the geopolymer concrete was not measured, V air The value is 1%. The total volume of coarse and fine aggregate is determined according to the following formula 14:
in the case of the formula 14,
the single use amount of the fine aggregate is calculated according to the following formula 15:
equation 15,m fag ＝r·V agg ·ρ fag ＝0.42×0.744×2612＝816kg；
The single-component dosage of the coarse aggregate is calculated according to the following formula 16:
formula 16,m cag ＝(1-r)·V agg ·ρ cag ＝(1-0.42)×0.744×2705＝1167kg。
(11) And (3) calculating the use amount of each component of the geopolymer concrete according to the steps (2) to (10), firstly, dry-mixing all solid components (including fly ash, slag powder, coarse aggregate and fine aggregate) uniformly according to the use amount of each component, stirring for 3 minutes, then adding an alkaline activator, continuing to stir for 4 minutes, finally adding a naphthalene water reducer, stirring for 3 minutes, and testing the geopolymer concrete mixture after ensuring uniform stirring. Firstly, checking the working performance of geopolymer concrete mixture, then pouring the mixture into a mold of 150mm multiplied by 150mm, carrying out vibration molding on the mold, then placing the mold in an environment with the temperature of 20 +/-2 ℃ for 1d, then removing the mold, placing a test block in an environment with the temperature of 20 +/-2 ℃ and the humidity of 95% for curing for 28d after removing the mold, and then testing the 28d compressive strength of the geopolymer concrete test piece.
Example 2: in this embodiment, the concrete implementation steps are as follows, taking the mix proportion design of geopolymer concrete with strength grade of C40 as an example:
(1) Determining the working performance and compressive strength grade requirements of geopolymer concrete: the 28d target compressive strength was set to 40MPa and the target slump was greater than 45mm.
(2) Determining the total dosage of the alkali-activating agent: when the maximum particle size of the coarse aggregate is 20mm, according to the step (2) in the summary of the invention, the single dosage of the alkali-activating agent corresponding to the target slump value (45 mm) is 190kg, that is, the single dosage of the alkali-activating agent is m aac ＝190kg。
(3) The molar concentration of the sodium hydroxide solution in the alkali activator was selected to be 14M, and the ratio between the sodium silicate solution and the sodium hydroxide solution was 1.5.
(4) Preferably, the silicon-aluminum raw material consists of 30 percent of S95 slag powder and 70 percent of fly ash, and SiO in the combined silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The ratio of the ingredients is 45.1%, 29.7% and 19.0% respectively. SiO in the silicon-aluminum raw material 2 、Al 2 O 3 CaO andFe 2 O 3 the proportions are all in an allowable range, so the proportion of the fly ash and the slag powder does not need to be changed.
(5) The 28d target compressive strength is set to be 40MPa, and the preparation strength of the geopolymer concrete can be calculated by referring to related regulations in JGJ 55-2011' design rule for mix proportion of common concrete
f cu,0 ＝40+1.645×5＝48.2MPa
The alkali-to-gel ratio results can be calculated according to the variant of equation 2 as follows:
in the formula 2, the first and second groups,
(6) Determining the proportion between the coarse aggregates: according to the step (6) in the summary of the invention, when the volume of the fine aggregate is 42% of the total volume of the aggregate and the volume of the coarse aggregate is 58% of the total volume of the aggregate, the bulk density of the aggregate is the largest and the void ratio is the smallest, and the skeleton of the aggregate is in the most 'compact state', i.e. r =0.42 and the sand ratio is about 41.2%.
(7) Determining the usage amount of the fly ash and the slag powder. According to the formula 3, the single-component dosage of the silicon-aluminum raw material is determined as follows:
in the formula 3, the first and second phases,
from the step (4), the proportion of the fly ash in the silicon-aluminum raw material is 70%, and the single-component usage amount of the fly ash is determined by calculation according to the formula 4:
formula 4,m fl ＝m cm ·α＝317×0.7≈222kg；
Determining the single formula dosage of the slag powder according to a formula 5:
equation 5,m sl ＝m cm ·(1-α)＝317×0.3≈95kg。
(8) Determining the dosage of a sodium hydroxide solution and a sodium silicate solution in the alkaline activator:
as can be seen from step (3), the ratio between the sodium silicate solution and the sodium hydroxide solution is 1.5, i.e. β =1.5, and the single dosage of the sodium hydroxide solution is determined according to the following formula 9:
equation 9,m sh ＝m aac /(1+β)＝190/(1+1.5)＝76kg
The single use amount of the sodium silicate solution is determined according to the following formula 10:
(9) Determining the dosage of the water reducing agent: according to slump tests of geopolymer concrete mixtures, when the dosage of the naphthalene water reducer is 0.5% of the dosage of the silicon-aluminum raw material, the geopolymer concrete mixture has good working performance and basically does not influence the strength, so that the mass ratio of the water reducer to the cementing material is determined to be gamma =0.5%;
the single formula dosage of the water reducing agent is determined according to the following formula 11:
equation 11,m sp ＝m cm ·γ＝317×0.5％＝1.59kg。
(10) Determining the dosage of coarse and fine aggregates: the invention adopts an absolute volume method to design the mixing proportion of geopolymer concrete, and the total volume of the prepared geopolymer concrete is 1m during calculation 3 In addition, since the gas content in the geopolymer concrete was not measured, V air The value is 1%. The total volume of coarse and fine aggregates is determined according to the following formula 14:
in the case of the formula 14,
the single use amount of the fine aggregate is calculated according to the following formula 15:
formula 15,m fag ＝r·V agg ·ρ fag ＝0.42×0.717×2612＝787kg；
The single-component dosage of the coarse aggregate is calculated according to the following formula 16:
formula 16,m cag ＝(1-r)·V agg ·ρ cag ＝(1-0.42)×0.717×2705＝1125kg。
(11) And (3) calculating the use amounts of all components of the geopolymer concrete according to the steps (2) to (10), firstly, dry-mixing all solid components (including fly ash, slag powder, coarse aggregate and fine aggregate) uniformly according to the use amounts of all the components, stirring for 3 minutes, then adding an alkaline activator, continuing stirring for 4 minutes, finally adding a naphthalene water reducer, stirring for 3 minutes, and testing the geopolymer concrete mixture after ensuring uniform stirring. Firstly, checking the working performance of geopolymer concrete mixture, then pouring the mixture into a mold with the thickness of 150mm multiplied by 150mm, carrying out vibration molding on the mold, then placing the mold for 1d in the environment with the temperature of 20 +/-2 ℃, then removing the mold, placing a test block in the environment with the temperature of 20 +/-2 ℃ and the humidity of 95% for curing for 28d after removing the mold, and then testing the 28d compressive strength of the geopolymer concrete test piece.
Example 3: in this embodiment, the concrete implementation steps are as follows, taking the mix proportion design of geopolymer concrete with strength grade of C50 as an example:
(1) Determining the working performance and compressive strength grade requirements of geopolymer concrete: the 28d target compressive strength was set to 50MPa and the target slump was greater than 60mm.
(2) Determining the total dosage of the alkali-activating agent: when the maximum particle size of the coarse aggregate is 20mm, according to the step (2) in the summary of the invention, the single dosage of the alkali-activating agent corresponding to the target slump value (60 mm) is 200kg, that is, the single dosage of the alkali-activating agent is m aac ＝200kg。
(3) The molar concentration of the sodium hydroxide solution in the alkali activator was selected to be 14M, and the ratio between the sodium silicate solution and the sodium hydroxide solution was 1.5.
(4) Preferably, the silicon-aluminum raw material consists of 30% of S95 slag powder and 70% of fly ash, and SiO in the combined silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The ratio of the components is 45.1%, 29.7% and 19.0% respectively. SiO in the silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The ratio of the coal ash to the slag powder is within the allowable range, so the ratio of the coal ash to the slag powder does not need to be changed.
(5) The 28d target compressive strength is set to be 50MPa, and the preparation strength of the geopolymer concrete can be calculated by referring to related regulations in JGJ 55-2011' design rule for mix proportion of common concrete
f cu,0 ＝50+1.645×6＝59.9MPa
The alkali-to-gel ratio results can be calculated according to the variant of equation 2 as follows:
in the formula 2, the first and second groups of the formula,
(6) Determining the proportion between the coarse aggregates: according to the step (6) in the summary of the invention, when the volume of the fine aggregate is 42% of the total volume of the aggregate and the volume of the coarse aggregate is 58% of the total volume of the aggregate, the bulk density of the aggregate is the largest and the void ratio is the smallest, and the skeleton of the aggregate is in the most 'compact state', i.e. r =0.42 and the sand ratio is about 41.2%.
(7) Determining the usage amount of the fly ash and the slag powder. According to the formula 3, the single use amount of the silicon-aluminum raw material is determined as follows:
in the case of the formula 3,
according to the step (4), the fly ash accounts for 70% of the silicon-aluminum raw material, and the single-component usage amount of the fly ash is calculated and determined according to the formula 4:
formula 4,m fl ＝m cm ·α＝426×0.7≈298kg；
Determining the single formula dosage of the slag powder according to the formula 5:
equation 5,m sl ＝m cm ·(1-α)＝426×0.3≈128kg。
(8) Determining the dosage of a sodium hydroxide solution and a sodium silicate solution in the alkaline activator:
as can be seen from step (3), the ratio between the sodium silicate solution and the sodium hydroxide solution is 1.5, i.e. β =1.5, and the single dosage of the sodium hydroxide solution is determined according to the following formula 9:
equation 9,m sh ＝m aac /(1+β)＝200/(1+1.5)＝80kg；
The single use amount of the sodium silicate solution is determined according to the following formula 10:
(9) Determining the dosage of the water reducing agent: according to slump tests of geopolymer concrete mixtures, when the dosage of the naphthalene water reducer is 1.0% of the dosage of the silicon-aluminum raw material, the slump of the geopolymer concrete mixture meets the requirement and the strength is basically not affected, so that the mass ratio of the water reducer to the cementing material is determined to be gamma =1.0%;
the single formula dosage of the water reducing agent is determined according to the following formula 11:
equation 11,m sp ＝m cm ·γ＝426×1.0％＝4.26kg。
(10) Determining the dosage of coarse and fine aggregates: the invention adopts an absolute volume method to design the mixing proportion of geopolymer concrete, and the total volume of the prepared geopolymer concrete is 1m during calculation 3 In addition, since the gas content in the geopolymer concrete was not measured, V air The value is 1%. The total volume of coarse and fine aggregates is determined according to the following formula 14:
in the case of the formula 14,
the single use amount of the fine aggregate is calculated according to the following formula 15:
formula 15,m fag ＝r·V agg ·ρ fag ＝0.42×0.66×2612＝724kg；
The single-component dosage of the coarse aggregate is calculated according to the following formula 16:
formula 16,m cag ＝(1-r)·V agg ·ρ cag ＝(1-0.42)×0.66×2705＝1035kg。
(11) Calculating the use levels of all components of the geopolymer concrete according to the steps (2) to (10), firstly, dry-mixing all solid components (including fly ash, slag powder, coarse aggregate and fine aggregate) uniformly according to the use levels of all the components, stirring for 3 minutes, then adding an alkaline activator, continuing to stir for 4 minutes, finally adding a naphthalene water reducer, stirring for 3 minutes, and testing the geopolymer concrete mixture after ensuring uniform stirring; firstly, checking the working performance of geopolymer concrete mixture, then pouring the mixture into a mold of 150mm multiplied by 150mm, carrying out vibration molding on the mold, then placing the mold in an environment with the temperature of 20 +/-2 ℃ for 1d, then removing the mold, placing a test block in an environment with the temperature of 20 +/-2 ℃ and the humidity of 95% for curing for 28d after removing the mold, and then testing the 28d compressive strength of the geopolymer concrete test piece.
Example 4: in this embodiment, the concrete implementation steps are as follows, taking the mix proportion design of geopolymer concrete with strength grade of C60 as an example:
(1) Determining the working performance and the compressive strength grade requirement of geopolymer concrete: the 28d target compressive strength was set to 60MPa and the target slump was greater than 40mm.
(2) Determining the total dosage of the alkali-activating agent: when the maximum particle size of the coarse aggregate is 20mm, according to the step (2) in the summary of the invention, the single dosage of the alkali-activator corresponding to the target slump value (40 mm) is 190kg, that is, the single dosage of the alkali-activator is m aac ＝190kg。
(3) The molar concentration of the sodium hydroxide solution in the alkali activator was selected to be 14M, and the ratio between the sodium silicate solution and the sodium hydroxide solution was 1.5.
(4) Preferably, the silicon-aluminum raw material consists of 30% of S95 slag powder and 70% of fly ash, and SiO in the combined silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The proportion is respectively 45.1%, 29.7% and 19.0%; siO in the silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The ratio of the coal ash to the slag powder is within the allowable range, so the ratio of the coal ash to the slag powder does not need to be changed.
(5) The 28d target compressive strength is set to be 60MPa, and the preparation strength of the geopolymer concrete can be calculated by referring to related regulations in JGJ 55-2011' design rule for mix proportion of common concrete
f cu,0 ＝1.15×60＝69MPa
The alkali-to-gel ratio results can be calculated according to the variant of equation 2 as follows:
in the formula 2, the first and second groups,
(6) Determining the proportion between the coarse aggregates: according to the step (6) in the summary of the invention, when the volume of the fine aggregate is 42% of the total volume of the aggregate and the volume of the coarse aggregate is 58% of the total volume of the aggregate, the bulk density of the aggregate is the largest and the void ratio is the smallest, and the skeleton of the aggregate is in the most 'compact state', i.e. r =0.42 and the sand ratio is about 41.2%.
(7) Determining the usage amount of the fly ash and the slag powder. According to the formula 3, the single-component dosage of the silicon-aluminum raw material is determined as follows:
in the formula 3, the first and second phases,
according to the step (4), the fly ash accounts for 70% of the silicon-aluminum raw material, and the single-component usage amount of the fly ash is calculated and determined according to the formula 4:
formula 4,m fl ＝m cm ·α＝500×0.7＝350kg；
Determining the single formula dosage of the slag powder according to a formula 5:
equation 5,m sl ＝m cm ·(1-α)＝500×0.3＝150kg。
(8) Determining the dosage of a sodium hydroxide solution and a sodium silicate solution in the alkaline activator:
as can be seen from step (3), the ratio between the sodium silicate solution and the sodium hydroxide solution is 1.5, i.e. β =1.5, and the single dosage of the sodium hydroxide solution is determined according to the following formula 9:
equation 9,m sh ＝m aac /(1+β)＝190/(1+1.5)＝76kg
The single use amount of the sodium silicate solution is determined according to the following formula 10:
(9) Determining the dosage of the water reducing agent: according to slump tests of geopolymer concrete mixtures, when the dosage of the naphthalene water reducer is 1.5% of the dosage of the silicon-aluminum raw material, the slump of the geopolymer concrete mixture meets the requirement and the strength is basically not affected, so that the mass ratio of the water reducer to the cementing material is determined to be gamma =1.5%;
the single formula dosage of the water reducing agent is determined according to the following formula 11:
equation 11,m sp ＝m cm ·γ＝500×1.5％＝7.5kg。
(10) Determining the dosage of coarse and fine aggregates: the invention adopts an absolute volume method to design the mixing proportion of geopolymer concrete, and the total volume of the prepared geopolymer concrete is 1m during calculation 3 In addition, since the gas content in the geopolymer concrete was not measured, V air The value is 1%. The total volume of coarse and fine aggregates is determined according to the following formula 14:
in the case of the formula 14,
the single use amount of the fine aggregate is calculated according to the following formula 15:
formula 15,m fag ＝r·V agg ·ρ fag ＝0.42×0.631×2612＝692kg；
The single-component dosage of the coarse aggregate is calculated according to the following formula 16:
formula 16,m cag ＝(1-r)·V agg ·ρ cag ＝(1-0.42)×0.631×2705＝990kg。
(11) And (3) calculating the use amounts of all components of the geopolymer concrete according to the steps (2) to (10), firstly, dry-mixing all solid components (including fly ash, slag powder, coarse aggregate and fine aggregate) uniformly according to the use amounts of all the components, stirring for 3 minutes, then adding an alkaline activator, continuing stirring for 4 minutes, finally adding a naphthalene water reducer, stirring for 3 minutes, and testing the geopolymer concrete mixture after ensuring uniform stirring. Firstly, checking the working performance of geopolymer concrete mixture, then pouring the mixture into a mold with the thickness of 150mm multiplied by 150mm, carrying out vibration molding on the mold, then placing the mold for 1d in the environment with the temperature of 20 +/-2 ℃, then removing the mold, placing a test block in the environment with the temperature of 20 +/-2 ℃ and the humidity of 95% for curing for 28d after removing the mold, and then testing the 28d compressive strength of the geopolymer concrete test piece.
Example 5: in this embodiment, the concrete implementation steps are as follows, taking the mix proportion design of geopolymer concrete with strength grade of C65 as an example:
(1) Determining the working performance and compressive strength grade requirements of geopolymer concrete: the 28d target compressive strength was set to 65MPa and the target slump was greater than 40mm.
(2) Determining the total dosage of the alkali-activating agent: when the maximum particle size of the coarse aggregate is 20mm, according to the step (2) in the summary of the invention, the single dosage of the alkali-activating agent corresponding to the target slump value (40 mm) is 190kg, that is, the single dosage of the alkali-activating agent is m aac ＝190kg。
(3) The molar concentration of the sodium hydroxide solution in the alkali activator was selected to be 14M, and the ratio between the sodium silicate solution and the sodium hydroxide solution was 1.5.
(4) Preferably, the silicon-aluminum raw material consists of 30% of S95 slag powder and 70% of fly ash, and SiO in the combined silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The ratio of the ingredients is 45.1%, 29.7% and 19.0% respectively. SiO in the silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The ratio of the coal ash to the slag powder is within the allowable range, so the ratio of the coal ash to the slag powder does not need to be changed.
(5) The 28d target compressive strength is set to 65MPa, and the preparation strength of the geopolymer concrete can be calculated by referring to relevant regulations in JGJ 55-2011' design rule of mixing proportion of common concrete
f cu,0 ＝1.15×65＝74.8MPa
The alkali-to-gel ratio results can be calculated according to the variant of equation 2 as follows:
in the formula 2, the first and second groups,
(6) Determining the proportion between the coarse aggregates: according to the step (6) in the summary of the invention, when the volume of the fine aggregate is 42% of the total volume of the aggregate and the volume of the coarse aggregate is 58% of the total volume of the aggregate, the bulk density of the aggregate is the largest and the void ratio is the smallest, and the skeleton of the aggregate is in the most 'compact state', i.e. r =0.42 and the sand ratio is about 41.2%.
(7) Determining the usage amount of the fly ash and the slag powder. According to the formula 3, the single use amount of the silicon-aluminum raw material is determined as follows:
in the case of the formula 3,
from the step (4), the proportion of the fly ash in the silicon-aluminum raw material is 70%, and the single-component usage amount of the fly ash is determined by calculation according to the formula 4:
formula 4,m fl ＝m cm ·α＝576×0.7＝403kg；
Determining the single formula dosage of the slag powder according to the formula 5:
equation 5,m sl ＝m cm ·(1-α)＝576×0.3＝173kg。
(8) Determining the dosage of sodium hydroxide solution and sodium silicate solution in the alkaline excitant:
as can be seen from step (3), the ratio between the sodium silicate solution and the sodium hydroxide solution is 1.5, i.e. β =1.5, and the single dosage of the sodium hydroxide solution is determined according to the following formula 9:
equation 9,m sh ＝m aac /(1+β)＝190/(1+1.5)＝76kg
The single use amount of the sodium silicate solution is determined according to the following formula 10:
(9) Determining the dosage of the water reducing agent: according to slump tests of geopolymer concrete mixtures, when the dosage of the naphthalene water reducer is 1.9% of the dosage of the silicon-aluminum raw material, the slump of the geopolymer concrete mixture meets the requirement and the strength is basically not affected, so that the mass ratio of the water reducer to the cementing material is determined to be gamma =1.9%;
the single formula dosage of the water reducing agent is determined according to the following formula 11:
equation 11,m sp ＝m cm ·γ＝576×1.9％＝10.94kg。
(10) Determining the dosage of coarse and fine aggregates: the invention adopts an absolute volume method to design the mixing proportion of geopolymer concrete, and the total volume of the prepared geopolymer concrete is 1m during calculation 3 In addition, since the gas content in the geopolymer concrete was not measured, V air The value is 1%. The total volume of coarse and fine aggregates is determined according to the following formula 14:
in accordance with the formula 14, the first order,
the single use amount of the fine aggregate is calculated according to the following formula 15:
formula 15,m fag ＝r·V agg ·ρ fag ＝0.42×0.595×2612＝653kg；
The single-component dosage of the coarse aggregate is calculated according to the following formula 16:
formula 16,m cag ＝(1-r)·V agg ·ρ cag ＝(1-0.42)×0.595×2705＝933kg。
(11) And (3) calculating the use amounts of all components of the geopolymer concrete according to the steps (2) to (10), firstly, dry-mixing all solid components (including fly ash, slag powder, coarse aggregate and fine aggregate) uniformly according to the use amounts of all the components, stirring for 3 minutes, then adding an alkaline activator, continuing stirring for 4 minutes, finally adding a naphthalene water reducer, stirring for 3 minutes, and testing the geopolymer concrete mixture after ensuring uniform stirring. Firstly, checking the working performance of geopolymer concrete mixture, then pouring the mixture into a mold with the thickness of 150mm multiplied by 150mm, carrying out vibration molding on the mold, then placing the mold for 1d in the environment with the temperature of 20 +/-2 ℃, then removing the mold, placing a test block in the environment with the temperature of 20 +/-2 ℃ and the humidity of 95% for curing for 28d after removing the mold, and then testing the 28d compressive strength of the geopolymer concrete test piece.
Comparative example 1 (based on example 3, only the ratio of slag powder to fly ash in the raw material of silicon and aluminum is changed):
(1) Determining the working performance and compressive strength grade requirements of geopolymer concrete: the 28d target compressive strength was set to 50MPa and the target slump was greater than 60mm.
(2) Determining the total dosage of the alkali-activating agent: when the maximum particle size of the coarse aggregate is 20mm, according to the step (2) in the summary of the invention, the single dosage of the alkali-activator corresponding to the target slump value (60 mm) is 200kg, that is, the single dosage of the alkali-activator is m aac ＝200kg。
(3) The molar concentration of the sodium hydroxide solution in the alkali activator was selected to be 14M, and the ratio between the sodium silicate solution and the sodium hydroxide solution was 1.5.
(4) The silicon-aluminum raw material consists of 20 percent of S95 slag powder and 80 percent of fly ash, and SiO in the combined silicon-aluminum raw material 2 、Al 2 O 3 CaO and Fe 2 O 3 The proportion is respectively 46.5%, 31.6% and 16.5%; siO in the silicon-aluminum raw material 2 CaO and Fe 2 O 3 The ratio of Al is within the allowable range 2 O 3 Exceeding the allowable range; the effect of the ratio of fly ash to slag powder on geopolymer concrete performance was explored by implementing this comparative example.
(5) The 28d target compressive strength is set to be 50MPa, and the preparation strength of the geopolymer concrete can be calculated by referring to related regulations in JGJ 55-2011' design rule for mix proportion of common concrete
f cu,0 ＝50+1.645×6＝59.9MPa
The alkali-to-gel ratio results can be calculated according to the variant of equation 2 as follows:
in the formula 2, the first and second groups,
(6) Determining the proportion between the coarse aggregates: according to the step (6) in the summary of the invention, when the volume of the fine aggregate is 42% of the total volume of the aggregate and the volume of the coarse aggregate is 58% of the total volume of the aggregate, the bulk density of the aggregate is the largest and the void ratio is the smallest, and the skeleton of the aggregate is in the most 'compact state', i.e. r =0.42 and the sand ratio is about 41.2%.
(7) Determining the use amounts of two silicon-aluminum raw materials of fly ash and slag powder: according to the formula 3, the single use amount of the silicon-aluminum raw material is determined as follows:
in the formula 3, the first and second phases,
from the step (4), the proportion of the fly ash in the silicon-aluminum raw material is 80%, and the single-component usage amount of the fly ash is determined by calculation according to the formula 4:
formula 4,m fl ＝m cm ·α＝426×0.8≈341kg；
Determining the single formula dosage of the slag powder according to the formula 5:
equation 5,m sl ＝m cm ·(1-α)＝426×0.2≈85kg。
(8) Determining the dosage of a sodium hydroxide solution and a sodium silicate solution in the alkaline activator:
as can be seen from step (3), the ratio between the sodium silicate solution and the sodium hydroxide solution is 1.5, i.e. β =1.5, and the single dosage of the sodium hydroxide solution is determined according to the following formula 9:
equation 9,m sh ＝m aac /(1+β)＝200/(1+1.5)＝80kg；
The single use of sodium silicate solution is determined as follows in equation 10:
(9) Determining the dosage of the water reducing agent: according to slump tests of geopolymer concrete mixtures, when the dosage of the naphthalene water reducer is 1.0% of the dosage of the silicon-aluminum raw material, the slump of the geopolymer concrete mixture meets the requirement and the strength is basically not affected, so that the mass ratio of the water reducer to the cementing material is determined to be gamma =1.0%;
the single formula dosage of the water reducing agent is determined according to the following formula 11:
equation 11,m sp ＝m cm ·γ＝426×1.0％＝4.26kg。
(10) Determining the dosage of coarse and fine aggregates: the invention adopts an absolute volume method to design the mixing proportion of the geopolymer concrete, and the total volume of the prepared geopolymer concrete is 1m in calculation 3 In addition, the gas content in the geopolymer concrete was not measured，V air The value is 1%. The total volume of coarse and fine aggregates is determined according to the following formula 14:
in the case of the formula 14,
the single use amount of the fine aggregate is calculated according to the following formula 15:
formula 15,m fag ＝r·V agg ·ρ fag ＝0.42×0.654×2612＝717kg；
The single-component dosage of the coarse aggregate is calculated according to the following formula 16:
formula 16,m cag ＝(1-r)·V agg ·ρ cag ＝(1-0.42)×0.66×2705＝1026kg。
(11) Calculating the use levels of all components of the geopolymer concrete according to the steps (2) to (10), firstly, dry-mixing all solid components (including fly ash, slag powder, coarse aggregate and fine aggregate) uniformly according to the use levels of all the components, stirring for 3 minutes, then adding an alkaline activator, continuing stirring for 4 minutes, finally adding a naphthalene water reducer, stirring for 3 minutes, and testing the geopolymer concrete mixture after ensuring uniform stirring; firstly, checking the working performance of geopolymer concrete mixture, then pouring the mixture into a mold of 150mm multiplied by 150mm, carrying out vibration molding on the mold, then placing the mold in an environment with the temperature of 20 +/-2 ℃ for 1d, then removing the mold, placing a test block in an environment with the temperature of 20 +/-2 ℃ and the humidity of 95% for curing for 28d after removing the mold, and then testing the 28d compressive strength of the geopolymer concrete test piece.
Comparative example 2: in contrast to example 3, the molar concentration of the sodium hydroxide solution was 13M
Based on the above, the blending ratio of the geopolymer concrete in examples 1 to 5 and comparative examples 1 to 2 is shown in Table 3.
TABLE 3 compounding ratio of geopolymer concrete in examples 1-5 and comparative examples 1-2
The slump value and 28d compressive strength of geopolymer concrete were examined in both examples and comparative examples, and the test results are shown in Table 4.
TABLE 4 slump and 28d compressive strength values of geopolymer concretes
| Sample numbering | Slump (mm) | 28d compressive Strength (MPa) |
| Example 1 | 105 | 37.9 |
| Example 2 | 72 | 49.8 |
| Example 3 | 63 | 58.7 |
| Example 4 | 43 | 67.1 |
| Example 5 | 41 | 75.3 |
| Comparative example 1 | 81 | 48.2 |
| Comparative example 2 | 68 | 55.8 |
As can be seen from Table 4, the slump and the 28d compressive strength of the geopolymer concrete in examples 1 to 5 both meet the requirements, which indicates that the geopolymer concrete meeting the requirements of different working properties and strength properties can be prepared by the method for designing the geopolymer mixing ratio provided by the invention. In addition, it can be found by comparing example 3 with comparative example 1 that, although the slump value of the geopolymer concrete in comparative example 1 is larger than that in example 3 and satisfies the target value of slump, the compressive strength is reduced by 10.5MPa compared with example and does not satisfy the target value of compressive strength, so that when the ratio of the slag powder to the fly ash is adjusted, it is not recommended to exceed the allowable range given in step (3) in the summary of the invention. As can be seen from example 3 and comparative example 2, decreasing the molar concentration of sodium hydroxide increases the slump value of the geopolymer concrete, but decreases the 28d compressive strength value of the geopolymer concrete, although the compressive strength of the geopolymer concrete in comparative example 2 still meets the requirements, indicating that it is feasible to adjust the amount of material within the ranges given in the summary of the invention.
It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention, and it is obvious to those skilled in the art that the present invention can be modified and changed in various forms, such as changing design objective, changing dosage of alkali activator, changing type of aggregate gradation, changing type of raw silica-alumina, changing range of material dosage, changing relation between alkali-binder ratio and compressive strength, and the like, which all belong to the common modifications of the present invention, and all of them should be included in the protection scope of the present invention.
Claims (5)
1. A fly ash-slag powder based geopolymer concrete mix proportion design method is characterized by comprising the following steps:
(1) Determining the compressive strength and slump value of geopolymer concrete according to engineering requirements;
(2) Determining the total dosage of the alkali-activating agent: the single dosage of the alkali activator is 190-210kg;
(3) Determining the molar concentration of a sodium hydroxide solution in an alkaline activator and the ratio of a sodium silicate solution to the sodium hydroxide solution;
(4) Determining the proportion of slag powder and fly ash in the silicon-aluminum raw material: the silicon-aluminum raw material consists of slag powder and low-calcium fly ash, wherein the slag powder is S95 or S105 slag powder, and the using amount of the slag powder is 27% -33% of the total amount of the silicon-aluminum raw material; the fly ash is first-grade or second-grade low-calcium fly ash, and the using amount of the fly ash is 67-73% of the total amount of the silicon-aluminum raw material;
(5) Determining the proportion of the dosage of the alkali activator to the dosage of the silicon-aluminum raw material, namely the alkali-glue ratio: determining the 28d compressive strength of the geopolymer concrete by changing the ratio of the alkali activator to the silicon-aluminum raw material, wherein the relation between the alkali-cement ratio and the 28-day compressive strength of the geopolymer concrete is given by a formula 2:
in the formula 2, the first and second groups,
the modification of equation 2 is
In the formula: f. of cu,0 The cubic geopolymer concrete has 28-day compressive strength (MPa); the cube size is 150mm, AAC/CM is the alkali-cement ratio, and the alkali-cement ratio can be calculated according to the compressive strength of geopolymer concrete by using a formula 2;
(6) Determining the proportion of coarse aggregates and fine aggregates: optimizing the aggregate gradation, and determining that the volume of the fine aggregate is r times of the total volume of the aggregate and the volume of the coarse aggregate is (1-r) times of the total volume of the aggregate;
(7) Determining the use amounts of two silicon-aluminum raw materials of fly ash and slag powder: the total amount of the silicon-aluminum raw material is determined according to the alkali-glue ratio and the total dosage of the alkali activator, and the value is calculated by a formula 3:
in the formula 3, the first and second phases,
in the formula: m is cm The dosage of the silicon-aluminum raw material in per cubic geopolymer concrete is kg; m is aac The dosage of the alkaline exciting agent in every cubic geopolymer concrete is kg;
from the step (4), if the proportion of the fly ash to the silicon-aluminum raw material is α, the usage amounts of the fly ash and the slag powder are determined by calculation according to the formulas 4 and 5:
formula 4,m fl ＝m cm ·α；
Equation 5,m sl ＝m cm ·(1-α)；
In the formula: m is a unit of fl The dosage of the fly ash in each cubic geopolymer concrete is kg; m is sl The dosage of the slag powder in each cubic geopolymer concrete is kg;
(8) Determining the dosage of a sodium hydroxide solution and a sodium silicate solution in the alkaline activator: according to the step (3), the ratio of the sodium silicate solution to the sodium hydroxide solution is selected to be beta, namely, the dosage relation of the sodium silicate solution to the sodium hydroxide solution conforms to a formula 6 and a formula 7:
equation 6,m ss /m sh ＝β；
Equation 7,m aac ＝m ss +m sh ；
In the formula: m is ss The dosage of sodium silicate solution in per cubic geopolymer concrete is kg; m is a unit of sh The dosage of sodium hydroxide solution in every cubic geopolymer concrete is kg;
from equation 6 and equation 7, equation 8 can be derived:
equation 8,m aac ＝m sh ·(1+β)；
Combining equations 7 and 8, the amounts of sodium hydroxide solution and sodium silicate solution are calculated by equations 9 and 10, respectively:
equation 9,m sh ＝m aac /(1+β)；
Equation 10,m ss ＝m aac -m sh ；
(9) Determining the dosage of the water reducing agent: the dosage of the naphthalene water reducer is determined according to the percentage of the water reducer in the silicon-aluminum raw material, when the alkali-glue ratio is 0.3-0.8, the dosage of the naphthalene water reducer is not more than 2.0% of the silicon-aluminum raw material, the naphthalene water reducer is in a liquid type, and when the mass ratio of the water reducer to the cementing material is gamma, the dosage of the water reducer is calculated according to a formula 11:
equation 11,m sp ＝m cm ·γ；
In the formula: m is a unit of sp The dosage of the water reducing agent in each cubic geopolymer concrete is kg;
(10) Determining the dosage of coarse and fine aggregates: the mixing proportion of the geopolymer concrete is designed by adopting an absolute volume method, and the total volume of the prepared geopolymer concrete is assumed to be 1m 3 Its volume satisfies equation 12:
formula 12,V agg +V fl +V sl +V sh +V ss +V sp +V air ＝1m 3 ；
In the formula: v agg M is the sum of the volumes of coarse and fine aggregates 3 ；V fl Is the volume of fly ash, m 3 ；V sl Is the volume of slag powder, m 3 ；V sh Volume of sodium hydroxide solution, m 3 ；V ss Volume of sodium silicate solution, m 3 ；V sp Is the volume of the naphthalene water reducer, m 3 ；V air Volume of air content, m 3 ；
Referring to JGJ55-2011 'design rule for mix proportion of common concrete', when the gas content in geopolymer concrete is not measured, V air The value is 1%, and thus the total volume of the coarse and fine aggregate is calculated according to the following equations 13 and 14:
equation 13, V agg ＝0.99m 3 -V fl -V sl -V sh -V ss -V sp ；
In the case of the formula 14,
in the formula: rho fl Is pulverized coalApparent density of ash, kg/m 3 ；ρ sl Is the apparent density of slag powder, kg/m 3 ；ρ sh The density of the sodium hydroxide solution is kg/m 3 ；ρ ss The density of the sodium silicate solution is kg/m 3 ；ρ sp The density of the naphthalene water reducing agent is kg/m 3 ；
To obtain the total volume V of the aggregate agg Then, according to the step (5), calculating the amount of the fine aggregate by adopting the formula 15:
formula 15,m fag ＝r·V agg ·ρ fag ；
In the formula: m is fag The dosage of the fine aggregate in each cubic geopolymer concrete is kg; rho fag Is the apparent density of fine aggregate, kg/m 3 ；
The amount of coarse aggregate is calculated using equation 16:
formula 16,m cag ＝(1-r)·V agg ·ρ cag ；
In the formula: m is cag The dosage of the coarse aggregate in the geopolymer concrete per cubic meter is kg; rho cag Is the apparent density of the coarse aggregate, kg/m 3 ；
(11) And (3) calculating the use amounts of all components of the geopolymer concrete according to the steps (2) to (10), firstly, dry-mixing all solid components uniformly according to the use amounts of all the components, including fly ash, slag powder, coarse aggregate and fine aggregate, stirring for 3 minutes, then adding an alkaline activator, continuing stirring for 4 minutes, finally adding a naphthalene water reducer, stirring for 3 minutes, testing the geopolymer concrete mixture after ensuring uniform stirring, and testing the working performance and compressive strength of the geopolymer concrete mixture.
2. The fly ash-slag powder based geopolymer concrete mix proportion design method as claimed in claim 1, wherein: in the step (3), the molar concentration of the sodium hydroxide solution is 13-15M, the modulus of the sodium silicate solution is 2.9-3.4, and the ratio of the sodium silicate solution to the sodium hydroxide solution is 1.4-1.6.
3. According to claim1 the blending ratio design method of the fly ash-slag powder based geopolymer concrete is characterized by comprising the following steps: the range of the main oxide components of the silicon-aluminum raw material in the step (4) is as follows: siO 2 2 42% -58% of Al 2 O 3 22 to 30 percent of CaO and Fe 2 O 3 15 to 21 percent.
4. The fly ash-slag powder based geopolymer concrete mix proportion design method according to claim 3, characterized in that: in the step (4), as a preferable scheme, the usage amount of the slag powder is 30% of that of the silicon-aluminum raw material, the usage amount of the fly ash is 70% of that of the silicon-aluminum raw material, and the silicon-aluminum raw material is composed of 30% of slag powder and 70% of fly ash.
5. The fly ash-slag powder based geopolymer concrete mix proportion design method as claimed in claim 1, wherein the concrete formulation per cubic meeting the various concrete compressive strength grade C30-C65 requirements is as follows: wherein the alkali-cement ratio of the compressive strength grade C30 is 0.74, and the fly ash is 180kg/m 3 77kg/m of slag powder 3 76kg/m sodium hydroxide 3 114kg/m sodium silicate solution 3 1167kg/m of coarse aggregate 3 816kg/m of fine aggregate 3 0kg/m of naphthalene water reducing agent 3 (ii) a Alkali-cement ratio of 0.6 to 222kg/m of fly ash of compressive strength grade C40 3 95kg/m of slag powder 3 76kg/m sodium hydroxide 3 114kg/m sodium silicate solution 3 1125kg/m of coarse aggregate 3 787kg/m of fine aggregate 3 Naphthalene series water reducing agent 1.59kg/m 3 (ii) a Alkali-cement ratio of compression strength grade C50 of 0.47 and coal ash of 298kg/m 3 128kg/m of slag powder 3 80kg/m sodium hydroxide 3 120kg/m sodium silicate solution 3 1035kg/m of coarse aggregate 3 724kg/m of fine aggregate 3 Naphthalene water reducing agent 4.26kg/m 3 (ii) a The alkali-cement ratio of the compressive strength grade C60 is 0.38, and the fly ash is 350kg/m 3 150kg/m of slag powder 3 76kg/m sodium hydroxide 3 114kg/m sodium silicate solution 3 692kg/m coarse aggregate 3 990kg/m of fine aggregate 3 Naphthalene, and mixtures thereofWater reducing agent of 7.5kg/m 3 (ii) a Alkali-cement ratio of compressive strength grade C65 of 0.33 and fly ash of 403kg/m 3 173kg/m of slag powder 3 76kg/m sodium hydroxide 3 114kg/m sodium silicate solution 3 653kg/m of coarse aggregate 3 933kg/m fine aggregate 3 10.94kg/m of naphthalene water reducing agent 3 ；
The fly ash is second-grade F-type low-calcium fly ash; the slag powder is granulated blast furnace slag with the grade of S95; the sodium hydroxide solution is prepared by adding flaky sodium hydroxide solid with the purity of more than 99 percent into deionized water and mixing, and the molar concentration of the flaky sodium hydroxide solid is 14M; the sodium silicate solution is water glass, the original modulus of the water glass is about 3.3, and the Baume degree of the water glass is 40; the fine aggregate is common washed river sand with the grain diameter of less than 4.75mm, and the fineness modulus is 2.74; the coarse aggregate is continuously graded broken stone with the particle size distribution range of 4.75-20 mm, and the liquid high-efficiency naphthalene water reducing agent is used as an additive with the solid content of 40%.
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