CN111454024A

CN111454024A - Sulfate-resistant concrete and preparation method thereof

Info

Publication number: CN111454024A
Application number: CN202010476113.4A
Authority: CN
Inventors: 周杰; 张保; 刘志强; 唐荣; 白琴琴
Original assignee: Xi'an Gao Ke Xin Da Concrete Co ltd
Current assignee: Xi'an Gao Ke Xin Da Concrete Co ltd
Priority date: 2020-05-29
Filing date: 2020-05-29
Publication date: 2020-07-28

Abstract

The invention relates to sulfate-resistant concrete and a preparation method thereof in the field of concrete preparation, wherein the sulfate-resistant concrete comprises a cementing material, sand, stones, an alkali activator and water; the cementing material comprises cement and slag powder, wherein the cement accounts for 15-20% of the cementing material by weight, and the slag powder accounts for the rest. The preparation steps are as follows: mixing the sand and stones and stirring to obtain a first mixture; adding a cementing material and an exciting agent into the first mixture, and stirring to obtain a second mixture; and adding water into the second mixture and stirring to obtain the sulfate-resistant concrete. The slag powder is added into the cementing material to replace 80-85% of the cement dosage, so that the dosage of single cement is less, and the calcium hydroxide, calcium silicate hydrate and calcium aluminate hydrate generated by cement hydration are reduced to control the probability of ettringite generation. And the activity of the slag powder is excited under the action of the alkali activator by increasing the dosage of the slag powder in the single-side concrete, so that the dosage of cement is reduced, the workability and the strength of the concrete are not changed, and the sulfate corrosion resistance of the concrete is improved.

Description

Sulfate-resistant concrete and preparation method thereof

Technical Field

The invention relates to the technical field of concrete preparation, in particular to sulfate-resistant concrete and a preparation method thereof.

Background

The concrete is cement concrete prepared with cement as cementing material, sand and stone as aggregate, water and additive in certain proportion and through mixing, and has the advantages of easy formation, low power consumption, high durability, low cost and capacity of being combined with steel material to form various bearing structures.

The sulfate corrosion of concrete is an erosion damage with great harm and also one of important factors influencing the durability of concrete. For example, large areas of salinized land exist in northwest of China, and seawater in coastal areas is rich in a large amount of sulfate. The concrete is buried underground for a long time and is contacted with the saline soil and the seawater, and can be damaged by corrosive medium sulfate in the saline soil and the seawater, so that the service life of the concrete is seriously damaged, and potential safety hazards are brought to building structures. Therefore, the research and development of the sulfate-resistant concrete have great practical value.

The prior application document with publication number CN108585661A discloses a sulfate-resistant concrete and a preparation method thereof, which are prepared from the following components, by weight, 60-70 parts of sulfate-resistant cement, 30-40 parts of mineral admixture, 50-90 parts of washed sand, 40-80 parts of machine-made sand, 160 parts of coarse aggregate 110-doped sand, 4-6 parts of polypropylene fiber, 2-3 parts of carboxymethyl cellulose, 70-90 parts of slurrying water, 0.5-0.8 part of absolute ethyl alcohol, 2-3 parts of SBT-RAM concrete preservative and 1-2 parts of admixture.

The preparation method of the sulfate-resistant concrete comprises the following steps: s1, weighing the anti-sulfate cement, the mineral admixture, the washed sand, the machine-made sand, the coarse aggregate, the polypropylene fiber, the carboxymethyl cellulose, the prepared slurry water, the absolute ethyl alcohol, the SBT-RAM concrete preservative and the admixture according to the weight parts; s2: adding carboxymethyl cellulose into the prepared slurry water, continuously stirring and heating to 50 ℃, uniformly stirring, and cooling to room temperature to obtain an emulsion; s3: adding absolute ethyl alcohol into the emulsion obtained in the step S2, stirring for 1-2min, then adding sulfate-resistant cement, mineral admixture and polypropylene fiber, and stirring uniformly; s4: and (5) adding water washed sand, machine-made sand and coarse aggregate into the mixture obtained in the step (S3), stirring for 2-3min, and finally adding the SBT-RAM concrete preservative and the additive, and fully and uniformly stirring.

In addition, the SBT-RAM concrete preservative, the mineral admixture, the absolute ethyl alcohol and the additive influence the sulfate resistance of the concrete to a certain extent, wherein the SBT-RAM concrete preservative, the mineral admixture and the absolute ethyl alcohol can better enhance the sulfate corrosion resistance of the concrete, and particularly the coordination of the SBT-RAM concrete preservative, the mineral admixture and the absolute ethyl alcohol can better enhance the sulfate corrosion resistance of the concrete to a great extent.

But the production cost of the sulfate-resistant concrete is increased by adding the sulfate-resistant cement, the SBT-RAM concrete preservative and the absolute ethyl alcohol into the components, and at present, enterprises with the qualification of producing the sulfate-resistant cement are relatively few, so that the mass production of the sulfate-resistant concrete is not facilitated.

Disclosure of Invention

Aiming at the defects in the prior art, one of the purposes of the invention is to provide sulfate-resistant concrete, which is prepared by replacing a large amount of cement with slag powder and is more suitable for practical use under the action of an alkali activator.

The invention aims to provide a preparation method of sulfate-resistant concrete, which is simple and convenient.

The above object of the present invention is achieved by the following technical solutions:

the sulfate-resistant concrete comprises the following components of a cementing material, sand, stones, an alkali activator and water; the cementing material comprises cement and slag powder, wherein the cement accounts for 15-20% of the cementing material by weight, and the slag powder accounts for the balance.

By adopting the technical scheme, the concrete sulfate erosion is divided into internal erosion and external erosion. Internal erosion refers to the expansion, cracking and destruction of concrete caused by sulfates present in the raw materials. External erosion refers to erosion caused by exposure of concrete to sulfate environments from the atmosphere, soil and water. In general, the vast majority of sulfate attacks are external attacks.

The sulphate attack concrete mechanism is divided into two types, physical attack and chemical attack; the salt crystallization pressure theory in the physical erosion damage mechanism is accepted by most researchers, namely when the salt solution concentration in the external environment is over saturated, crystals are separated out, and the growth of the crystals can generate great crystallization pressure to generate pressure on the capillary pore wall of the concrete, so that the expansion damage of the concrete is caused. The chemical destruction mechanism mainly refers to the process of cement hydration products, such as calcium hydroxide, calcium silicate hydrate, calcium aluminate hydrate and sulfate, which are subjected to chemical reaction to generate expanded products such as ettringite, carbo-sulfur-calcium silicate, gypsum and the like. Most studies have shown that sulfate attack of concrete to produce ettringite causes most of the concrete to expand and damage.

Therefore, in the technical scheme, the slag powder is added into the cementing material to replace 80-85% of the cement dosage, the dosage of single cement is less, and the calcium hydroxide, calcium silicate hydrate and calcium aluminate hydrate generated by cement hydration are reduced to control the probability of ettringite generation. And the working performance and the strength of the concrete are not changed by increasing the using amount of the slag powder in the single-side concrete, so that the sulfate corrosion resistance of the concrete is improved.

Further, by adding an alkali activator into the components, the slag powder is waste slag generated in the process of smelting pig iron from steel, and has higher potential activity. The slag powder is used as one of the raw materials of the traditional cement industry, and is a concrete material which is formed by activating the chemical activity of the slag powder by an alkali activator based on the utilization of the potential activity of the slag powder and has the excellent performances of quick hardening, early strength, high compressive strength, acid and alkali corrosion resistance, good durability and the like.

Meanwhile, the recycling of waste residues generated in the process of smelting pig iron from steel can be improved by using a large amount of slag powder in the components, on one hand, the using amount of cement is reduced, the loss of natural resources is reduced, on the other hand, the waste residues can be utilized, the environment friendliness is achieved, the cement amount is reduced, the capability of improving the sulfate corrosion resistance of concrete can also be achieved, the performance is excellent, the cost is relatively low, and the using effect is excellent.

The component proportion is suitable for concrete with different strength grades such as C10, C15, C20, C25, C30, C35, C40, C45, C50, C55, C60 and the like.

More preferably, the material comprises the following components, by weight, 320-360 parts of cementing material, 780-800 parts of sand, 1050-1060 parts of stone, 3-3.7 parts of excitant and 160-165 parts of water; the cementing material comprises cement and slag powder, wherein the cement accounts for 15-17% of the cementing material by weight, and the slag powder accounts for the balance.

By adopting the technical scheme, the concrete with the grade of C30 can be prepared according to the mixture ratio of the components.

Further preferably, the material comprises the following components, by weight, 360-390 parts of a cementing material, 750-780 parts of sand, 1050-1060 parts of stones, 3.7-4 parts of an exciting agent and 160-165 parts of water; the cementing material comprises cement and slag powder, wherein the cement accounts for 15-18% of the cementing material by weight, and the slag powder accounts for the balance.

By adopting the technical scheme, the concrete with the grade of C35 can be prepared according to the mixture ratio of the components.

Further preferably, the cement comprises the following components, by weight, 390-420 parts of a cementing material, 750-800 parts of sand, 1060-1080 parts of stones, 4-4.5 parts of an exciting agent and 160-165 parts of water; the cementing material comprises cement and slag powder, wherein the cement accounts for 18-20% of the cementing material by weight, and the slag powder accounts for the balance.

By adopting the technical scheme, the concrete with the grade of C40 can be prepared according to the mixture ratio of the components.

More preferably, the alkali activator is a mixture of sodium hydroxide and any one of silica fume, potassium silicate and sodium silicate.

More preferably, the alkali activator is a mixture of potassium hydroxide and any one of silica fume, potassium silicate and sodium silicate.

More preferably, the alkali activator is a mixture of aluminum oxide and any one of silica fume, potassium silicate and sodium silicate.

By adopting the technical scheme, when the sodium hydroxide, the potassium hydroxide or the aluminum oxide is used together with the silicon ash, the sodium silicate or the potassium silicate, the slag powder and the fly ash are rapidly dissociated into a silicon-oxygen tetrahedron and an aluminum-oxygen tetrahedron, and then the silicon-oxygen tetrahedron and the aluminum-oxygen tetrahedron are condensed into a three-dimensional network structure, so that the time required by concrete curing is short, and the formed sulfate-resistant concrete has good durability and mechanical property, is quick to set and is early strong and compact in structure.

Furthermore, the silicon ash is used for replacing sodium silicate or potassium silicate, so that the energy consumption of high temperature and high pressure required in the preparation process of the sodium silicate can be reduced; compared with sodium silicate, the silicon content in the silica fume is higher, the comparison area is larger, and the using effect is better and excellent.

More preferably, the stones are 5-25mm continuous graded broken stones, the crushing index is less than 12%, and the flake content is less than 5%.

By adopting the technical scheme and adopting the continuous graded stones for configuration, the produced concrete has good workability, low porosity, reduced dosage of cementing materials and good fluidity.

More preferably, the slag powder is S95-grade slag powder.

By adopting the technical scheme, the activity index 7d of the S95-grade slag powder is greater than 75%, the activity index 28d is greater than 95%, the specific surface area is greater than 350m/kg, the ignition loss is less than 3%, and the sulfate-resistant concrete is suitable for being used in the sulfate-resistant concrete.

The second aim of the invention is realized by the following technical scheme: a preparation method of sulfate-resistant concrete comprises the following preparation steps:

step 1: mixing the sand and the stones, and stirring for 20-30s to obtain a first mixture;

step 2: adding a cementing material and an exciting agent into the first mixture, and stirring the mixture for 30 to 35 seconds to obtain a second mixture;

and step 3: and adding water into the second mixture and continuously stirring to obtain the sulfate-resistant concrete.

By adopting the technical scheme, the preparation of the sulfate-resistant concrete is completed in the processes of the step 1 to the step 3, and the operation is simple and convenient. .

In summary, the invention includes at least one of the following beneficial technical effects:

1. the slag powder is added into the cementing material to replace 80-85% of the cement dosage, so that the dosage of single cement is less, and the calcium hydroxide, calcium silicate hydrate and calcium aluminate hydrate generated by cement hydration are reduced to control the probability of ettringite generation. The working performance and the strength of the concrete are not changed by increasing the using amount of the slag powder in the single-side concrete, so that the sulfate corrosion resistance of the concrete is improved;

2. the utilization of a large amount of slag in the components can improve the reutilization of waste slag generated in the process of smelting pig iron from steel, so that on one hand, the consumption of cement is reduced, the loss of natural resources is reduced, on the other hand, the waste slag can be utilized, the environment friendliness is achieved, meanwhile, the cement amount is reduced, the sulfate corrosion resistance of concrete can be improved, the performance is excellent, the cost is relatively low, and the using effect is excellent;

3. the concrete with the components can be prepared into concrete with various strength grades, and the application range is wide.

Detailed Description

In the examples and the comparative examples, the stones adopt 5-25mm continuous graded broken stones, the crushing index is less than 12 percent, and the positive flake content is less than 5 percent.

The slag powder is S95 grade slag powder.

The present invention will be described in further detail below.

Example 1

The sulfate-resistant concrete comprises 48kg of cement, 272kg of slag powder, 800kg of sand, 1060kg of stones, 3kg of alkali activator and 160kg of water. The alkali activator includes 2.1kg of sodium hydroxide and 0.9kg of silica fume.

The preparation method of the sulfate-resistant concrete comprises the following steps: step 1: mixing the sand and the stones, and stirring for 20s to obtain a first mixture; step 2: adding the cementing material and the alkali activator into the first mixture, and stirring for 30s to obtain a second mixture; and step 3: and adding water into the second mixture and continuously stirring to obtain the sulfate-resistant concrete.

Example 2

Example 2 differs from example 1 in the amount of the components. The alkali activator includes 2.1kg of sodium hydroxide and 0.9kg of potassium silicate.

Example 3

Example 3 differs from example 1 in the amount of the components. The alkali activator includes 2.1kg of sodium hydroxide and 0.9kg of sodium silicate.

Example 4

Example 4 differs from example 1 in the amount of the components. The alkali activator includes 2.1kg of sodium hydroxide and 0.9kg of sodium silicate.

Example 5

Example 5 differs from example 1 in the amount of the components. The alkali activator includes 2.1kg of potassium hydroxide and 0.9kg of silica fume.

Example 6

Example 6 differs from example 1 in the amount of the components. The alkali activator comprises 2.45kg of potassium hydroxide and 1.05kg of potassium silicate.

Example 7

Example 7 differs from example 1 in the amount of the components. The alkali activator includes 2.8kg of potassium hydroxide and 1.2kg of sodium silicate.

Example 8

Example 8 differs from example 1 in the amount of the components. The alkali activator comprises 2.8kg of alumina and 1.2kg of silica fume.

Example 9

Example 9 differs from example 1 in the amount of the components. The alkali activator comprises 2.8kg of alumina and 1.2kg of potassium silicate.

TABLE 1 component contents of examples 1-9

Comparative example 1

Comparative example 1 is different from example 6 in that the cement content of comparative example 1 is 282.2kg and the slag powder content is 57.8 kg. The cement is P.O 42.5 cement.

Comparative example 2

Comparative example 2 is different from example 6 in that the cement content of comparative example 2 is 282.2kg and the slag powder content is 57.8 kg. The cement is sulfate-resistant silicate white cement of Baixin commercial limited company in Jinzhou city.

Comparative example 3

Comparative example 3 differs from example 6 in that comparative example 3 does not contain a trigger.

Test detection

1. Slump test: slump test: (1) fixing the slump cone on a bottom plate, and filling the prepared C30-C40 concrete into the slump cone in three layers; (2) inserting and tamping a tamping rod for 25 times from outside to inside in a spiral manner when each layer of concrete is filled, wherein the tamping rod penetrates through the bottommost part when the bottom layer is inserted and tamped, and the tamping rod penetrates through the surface of the next layer when the second layer and the top layer are inserted and tamped; (3) when the concrete is loaded into the top layer, the concrete should be higher than the slump cone opening and be leveled along the cone opening; (4) removing concrete on the bottom plate at the edge of the slump cone, vertically and stably lifting the slump cone, and slightly placing the slump cone beside the sample; (5) when the concrete sample is not in slump, measuring the height difference between the cylinder height and the highest point of the concrete sample after slump by using a steel ruler, namely the slump value, wherein the unit mm is about 5 mm.

2. Testing the expansion degree: after the steps of the slump tests (1) to (4), when the concrete sample is not expanded, the diameter of the maximum diameter of the expanded surface of the concrete sample in the vertical direction to the maximum diameter is measured by a steel ruler, and when the difference between the two diameters is less than 50mm, the arithmetic mean value of the two diameters is taken as an expansion value, unit mm is obtained, and the value is corrected to be 5 mm. When the difference between the two diameters is larger than 50mm, the test is carried out again.

3. And (3) detecting the workability: fluidity, slump measurement, cohesiveness measurement, visual inspection and empirical judgment; water retention, visual inspection, and empirical judgment.

4. And (3) detecting the compressive strength: manufacturing and testing a concrete sample: filling the prepared concrete into a concrete test mold at one time, and raising the prepared concrete out of a test mold opening; placing the test mold on a concrete vibration table for vibration until the surface returns slurry; stopping vibrating, taking down the test mold, scraping off the excess concrete at the upper opening of the test mold, troweling the concrete when the initial setting of the concrete is close, and placing the concrete in an environment with the temperature of 20 +/-5 ℃; numbering after 24 hours, removing the mold, and putting into a standard curing room for curing; and when the standard curing age of 56 days is reached, taking out the steel plate and performing a compressive strength test.

5. Sulfate resistance test: a concrete test block of 10X 10cm3 was made, demolded after one day of standing, moved to a standard curing room for 28 days, and then subjected to a dry-wet cycle test. The circulation system is as follows: soaking in 5% sodium sulfate solution at room temperature for 16 hr, taking out, air drying for 1 hr, oven drying in 80 deg.C oven for 6 hr, cooling for 1 hr, and weighing or pressing. One cycle was 24 hours. Then put into 5% sodium sulfate solution.

TABLE 2 test results for examples 1-9

As can be seen from Table 1, the strength of the concrete increases with the increase of the cement in the composition, wherein in example 2, the cement is used in the most amount and the strength of the concrete is the strongest.

Further, in comparative examples 3 to 5, the total amount of the cement was kept constant, and the amount ratio of the cement to the slag powder in the cement was adjusted, so that it was found that the strength of the concrete was increased as the slag powder content in the cement ratio was increased.

Continuing to compare example 3 with examples 6 and 7, the strength of the concrete can be increased with the addition of the activator, which can activate the slag powder and thus increase the strength of the concrete. And comparing example 6 with example 7, the intensity will vary more as the amount of activator is increased, wherein the properties of example 6 and example 7 do not differ much, so the preferred amount of activator is selected to be 3.5kg.

In comparative examples 7 to 9, the strength of the concrete was not greatly affected by changing the amount of the stones without changing the other components in the composition, so that the composition of example 6 was finally preferably used as the optimum composition of the C30 concrete. The performance of the final sulfate resistant concrete examples 1-9 met the sulfate resistance KS90 rating.

TABLE 3 test results of comparative examples 1 to 3

Analyzing the comparative example 1 and the example 6, the concrete strength of the concrete which is obtained by selecting a large amount of cement in the comparative example 1 and meets the strength requirement is obtained, so that the slag powder is suitable for being used as the cementing material in the application document. And the sulfate corrosion resistance of the selected slag powder is better.

In further comparative example 2, the sulfate-resistant cement is selected to achieve better sulfate corrosion resistance, but the cost is higher, so that the further mineral sulfate concrete is more suitable for production and use.

And further contrasts, when no excitant is added in the component raw materials, the strength of the concrete is obviously influenced. Therefore, the addition of the excitant can excite the activity of the slag powder, so that the strength performance of the concrete can be improved.

Example 10

The sulfate-resistant concrete comprises, by weight, 54kg of cement, 306kg of slag powder, 750kg of sand, 1050kg of stones, 4kg of an exciting agent and 160kg of water. The alkali activator includes 2.8kg of alumina and 1.2kg of sodium silicate.

The preparation method of the sulfate-resistant concrete comprises the following steps: step 1: mixing the sand and stones, and stirring for 25s to obtain a first mixture; step 2: adding a cementing material and an exciting agent into the first mixture, and stirring for 30s to obtain a second mixture; and step 3: and adding water into the second mixture and continuously stirring to obtain the sulfate-resistant concrete.

Example 11

Example 11 is different from example 10 in the content of components, and the alkali-activator comprises 2.94kg of alumina and 1.26kg of sodium silicate.

Example 12

Example 12 differs from example 10 in the content of components, and the alkali activator comprises 2.94kg of alumina and 1.26kg of sodium silicate.

Table 4 feed compositions for examples 10-12.

Table 5 test results for examples 10-12.

From Table 5, it can be seen that the strength of the C35 concrete of the examples meets the specification requirements and the corrosion resistance is excellent, so that the compositions of examples 13-15 are also suitable for producing C35 sulfate-resistant concrete.

Example 13

The sulfate-resistant concrete comprises, by weight, 66.6kg of cement, 293.4kg of slag powder, 750kg of sand, 1060kg of stones, 4kg of an activator and 160kg of water. The alkali activator includes 2.8kg of alumina and 1.2kg of sodium silicate.

Example 14

Example 14 is different from example 13 in the content of components, and the alkali-activator includes 2.94kg of alumina and 1.26kg of sodium silicate.

Example 15

Example 15 is different from example 13 in the content of components, and the alkali-activator includes 2.94kg of alumina and 1.26kg of sodium silicate.

TABLE 6 component contents of examples 13-15

TABLE 7 test results for examples 13-15

From Table 7, it can be seen that the strength of the C40 concrete of the examples meets the specification requirements and the corrosion resistance is excellent, so that the compositions of examples 13-15 are also suitable for producing C40 sulfate-resistant concrete.

The sulfate-resistant concrete of the application is also suitable for the proportion of concrete with strength grades of C10, C15, C20, C25, C45, C50, C55, C60 and above, and the common sulfate-resistant concrete with strength grades of C30, C35 and C40 and the performance of the sulfate-resistant concrete are only illustrated in the embodiment.

In other embodiments, the alkali activator can be selected from S.K.F activator produced by Xiiyang Guanteng novel building materials Co.

The embodiments of the present invention are preferred embodiments of the present invention, and the scope of the present invention is not limited by these embodiments, so: all equivalent changes made according to the structure, shape and principle of the invention are covered by the protection scope of the invention.

Claims

1. A sulfate-resistant concrete is characterized in that: comprises the following components of cementing material, sand, stones, alkali excitant and water; the cementing material comprises cement and slag powder, wherein the cement accounts for 15-20% of the cementing material by weight, and the slag powder accounts for the balance.

2. The sulfate-resistant concrete according to claim 1, wherein: comprises the following components, by weight, 320-360 parts of cementing material, 780-800 parts of sand, 1060 parts of stone 1050-containing material, 3-3.7 parts of excitant and 165 parts of water 160-containing material; the cementing material comprises cement and slag powder, wherein the cement accounts for 15-17% of the cementing material by weight, and the slag powder accounts for the balance.

3. The sulfate-resistant concrete according to claim 1, wherein: comprises the following components, by weight, 360-390 parts of cementing material, 750-780 parts of sand, 1060 parts of stone 1050-containing material, 3.7-4 parts of excitant and 165 parts of water 160-containing material; the cementing material comprises cement and slag powder, wherein the cement accounts for 15-18% of the cementing material by weight, and the slag powder accounts for the balance.

4. The sulfate-resistant concrete according to claim 1, wherein: comprises the following components, by weight, 390-420 parts of cementing material, 750-800 parts of sand, 1060-1080 parts of stone, 4-4.5 parts of excitant and 160-165 parts of water; the cementing material comprises cement and slag powder, wherein the cement accounts for 18-20% of the cementing material by weight, and the slag powder accounts for the balance.

5. The sulfate-resistant concrete according to claim 1, wherein: the alkali activator is selected from the mixture of sodium hydroxide and any one of silicon ash, potassium silicate and sodium silicate.

6. The sulfate-resistant concrete according to claim 1, wherein: the alkali activator is selected from the mixture of potassium hydroxide and any one of silicon ash, potassium silicate and sodium silicate.

7. The sulfate-resistant concrete according to claim 1, wherein: the alkali activator is a mixture of aluminum oxide and any one of silicon ash, potassium silicate and sodium silicate.

8. The sulfate-resistant concrete according to claim 1, wherein: the stones are 5-25mm continuous graded broken stones, the crushing index is less than 12%, and the positive flake content is less than 5%.

9. The sulfate-resistant concrete according to claim 1, wherein: the slag powder is S95-grade slag powder.

10. A method of producing sulphate-resistant concrete according to any one of claims 1 to 9, wherein: the preparation method comprises the following preparation steps:

step 2: adding a cementing material and an alkali activator into the first mixture, and stirring the mixture for 30 to 35 seconds to obtain a second mixture;