CN110451826B

CN110451826B - 32.5 mixed portland cement for rural towns and anti-crack concrete and preparation method thereof

Info

Publication number: CN110451826B
Application number: CN201910883331.7A
Authority: CN
Inventors: 蔡炳煌; 罗俊雄; 冷发光; 王紫娴; 周永祥; 宋笑; 王祖琦; 刘山; 赵林林
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-09-18
Filing date: 2019-09-18
Publication date: 2020-08-07
Anticipated expiration: 2039-09-18
Also published as: CN110451826A

Abstract

The invention relates to the field of cement and concrete, and discloses 32.5 mixed portland cement for rural towns and anti-crack concrete and a preparation method thereof, wherein the mixed portland cement is prepared by mixing clinker which requires index control in production or outsourcing and other raw materials and grinding, and the mixture ratio is as follows according to the mass of the cement: 40 to 65 percent of Portland cement clinker, 10 to 25 percent of limestone, 3.0 to 6.0 percent of gypsum, 6 to 45 percent of mixed material and 0.05 to 0.5 percent of grinding aid; part of control parameters are as follows: the mass content of the 3 um-32 um particles is more than or equal to 70 percent; SO of 2.2% or less₃The cement has the advantages of simple preparation process and wide raw material sources, the cement can be directly prepared into C35-C20 grade concrete by adding water, sand, stone and an additive into the cement, no admixture is needed, the concrete is mainly used for common structural engineering in rural towns, the crack resistance grade reaches at least L-III, the compactness, the homogeneity, the durability and the working performance of the concrete can be improved, the engineering cracks are reduced, and the cement is economical and improves the construction efficiency.

Description

32.5 mixed portland cement for rural towns and anti-crack concrete and preparation method thereof

Technical Field

The invention relates to the fields of cement and concrete production technology and solid waste comprehensive utilization, in particular to 32.5 mixed portland cement for rural towns and anti-crack concrete and a preparation method thereof.

Background

In 2018, the total national cement yield and consumption is 21.8 hundred million tons, wherein the 32.5 grade cement yield is about 10 hundred million tons and accounts for 45-50 percent. The cement clinker consumption of the C30 concrete with the largest consumption is below 200kg/m3, and the total cementing material (clinker and admixture) is about 400kg/m3, so the cement clinker coefficient of the ordinary concrete is below 0.5. In 2018, the yield of the premixed concrete in Hunan is 9600 ten thousand cubic meters, and the strength grade concrete of C15-C35 accounts for more than 85% of the total concrete.

At present, about 50 percent of cement in China is used for non-premixed concrete and mortar, a considerable part of the cement is 32.5 grade cement, and the cement is mainly used for a large number of small and medium-sized structural projects of rural houses, township houses and the like. Because the concrete is not premixed, the conditions of field mixing, metering, storage and the like are not met, and the conditions of mixed material powder resources, production, special vehicles, storage and the like are limited, so that the admixture is inconvenient to be doped. From the aspects of energy conservation and emission reduction, convenient construction, economy, practicality and the like, the method is suitable for being used for completely doping admixtures in cement plants, providing suitable cement varieties with corresponding lower grades, directly adding water, sand and stone to prepare concrete, and improving the durability of the concrete.

The conventional concrete strength of each part of the rural building is classified into ① basic beams, plates, bearing platforms and columns which are C20-C35 generally, ② wallboard columns which are C20 generally, ③ floor slabs which are C20-C25 generally and ④ civil structure concrete of prefabricated products such as towns, channels, small and medium-sized prefabricated products and the like which are C20-C30 generally according to the building engineering design, construction and acceptance specifications, wherein the conventional concrete strength of each part of the rural building is lower than 5 floors.

The grade division of the early crack resistance of the concrete according to JGJ/T193-2009 concrete durability test evaluation Standard is shown in the following table

GB/T3183 and its each grade masonry cement can only be applied to masonry, plastering, cushion concrete, that is, it can not be used for structural concrete, such as column, beam, floor, partial concrete wall, etc. GB/T3183 does not limit the clinker consumption, the mixed material variety and the mixing amount, greatly relaxes the requirements of the mixed material variety and the mixing amount compared with GB175, and the performance index of the product of the same level is much lower than that of GB 175.

If the amount of the mixed material is poor, the activity index is low and the grain composition is unreasonable, a large amount of portland cement clinker is needed when preparing the 32.5 general portland cement, which is not beneficial to energy conservation and emission reduction and cement production cost reduction and is difficult to meet part of engineering performance requirements. The clinker coefficient of the cement in the cement material of the strength grade of C30 and below is actually below 0.5, and when the cement with the strength of 42.5 or above is used for preparing the concrete with the strength range of C15-C35. In order to ensure the performance and the compactness of concrete, 100-200 kg of admixture is additionally doped into each cubic concrete, otherwise, too little slurry is contained in the concrete, the compactness of the concrete is influenced, and the working performance such as fluidity and the like cannot meet the construction requirements easily. The stirring time of premixed concrete is usually within 30 seconds, and the problems that cement, admixture, sand, stone, functional additive are difficult to stir uniformly and the like generally exist. Furthermore, sulfur trioxide in concrete directly affects not only the setting time but also the deformation properties, water demand properties, strength development and compatibility with additives. When 42.5 cement is used for preparing C15-C35 concrete, because the admixture is more in doping amount and little or no sulfur trioxide is in the admixture, sulfur trioxide is introduced into the cement only, so that sulfate ions required by hydration reaction of a cementing material in the concrete are seriously insufficient or deficient, and the performance of the concrete is seriously influenced.

Therefore, in order to meet the requirements of engineering construction and market, aiming at the C15-C35 structural concrete with low strength grade in rural areas and towns and improving the durability thereof and reducing engineering cracks, the suitable 32.5 mixed portland cement variety is researched and developed, the C35 and the following common structural concrete can be prepared by directly adding water, sand, stone and additives without adding admixtures, and the admixtures in the concrete cementing material are added when preparing cement products, so that the engineering cracking and durability are improved, and the like. Has great significance and social and economic benefits and good application prospect.

The invention aims at the problems of early cracking of concrete, homogeneity of a cementing material of premixed concrete and the like, and the objective requirements (about half of the total output of cement) of a large amount of 32.5 and other low-strength grade cement in rural and urban areas, and aims at comprehensively solving the practical problem of engineering application. On the basis of summarizing the prior art, a large number of experimental researches and analyses are carried out through extensive research and study, and corresponding technical schemes and measures are provided. According to the design, construction specification and standard of common concrete structural engineering of C15-C35, the 28-day compressive strength of the cement is required to be more than or equal to 32.5MPa and less than or equal to 42.5MPa, and the cement composition, the early-stage crack resistance grade, the 3-day compressive strength, the content of particles of 3 um-32 um and the SO content are simultaneously improved₃The content, alkali content, chloride ion and the compatibility with the water reducing agent are all required.

Disclosure of Invention

The invention aims to provide 32.5 mixed portland cement for rural towns and anti-crack concrete and a preparation method thereof, aiming at solving the problems in the prior art.

The technical scheme adopted by the invention is as follows:

a32.5 mixed silicate cement for anti-crack concrete in rural towns and villages adopts a mode of mixing clinker with production or outsourcing required control parameters with other raw materials and grinding, and the mixture ratio is calculated according to the mass of the cement: 40 to 65 percent of Portland cement clinker, 3.0 to 6.0 percent of gypsum, 10 to 25 percent of limestone, 6 to 45 percent of mixed material and 0.05 to 0.5 percent of grinding aid;

the portland cement clinker is calcined in a predecomposition kilnClinker, the control parameters of which are: except meeting the requirement of GB/T21372, the compressive strength of the material is more than or equal to 12MPa in 1 day, more than or equal to 28MPa in 3 days, more than or equal to 55MPa in 28 days, the mass content of tricalcium aluminate is less than or equal to 8 percent, the mass content of silicate mineral is more than or equal to 68 percent, the mass content of tricalcium silicate is less than or equal to 58 percent, the mass content of magnesium oxide is less than 5 percent, the mass content of free calcium oxide is less than or equal to 1.5 percent, and the alkali content is (₂O+Na₂O) is less than 0.6 percent.

Further, the mixed material comprises one or more of granulated blast furnace slag, calcined coal gangue and fly ash, 0-8% of sandstone, phosphorous slag, kiln ash, steel slag or other waste residues meeting the requirements are allowed to replace the mixed material in the mixed material, and the mixed material is ground to be more than or equal to 330m in specific surface area²/kg is less than or equal to 380m²Kg, the ratio of the 28-day compressive strength value of the mixture with the test mixture and the reference cement in the mass ratio of 3:7 to the reference cement is more than or equal to 65 percent; the alkali content in the mixed material is equal to (0.658K)₂O+Na₂O) is less than 0.6 percent, and the mass content of the chloride ions is less than 0.06 percent.

Furthermore, the grinding aid is prepared by compounding any one or two of triisopropanolamine cyclic borate and diethanol monoisopropanolamine cyclic borate with tetra sodium hydroxyethylidene diphosphonate.

Furthermore, the limestone meets the requirements that the mass content of aluminum oxide is less than or equal to 2.5 percent and the mass content of calcium carbonate is more than 80 percent; the gypsum is required to meet the requirements of GB/T5483 and GB/T21371.

A preparation method of 32.5 mixed silicate cement for anti-crack concrete in rural towns adopts a mode of mixing and grinding clinker and other raw materials;

firstly, selecting raw materials, detecting portland cement clinker, mixed materials, gypsum, limestone and grinding aids, and putting the raw materials meeting the regulations into the next production procedure.

And step two, when a mixed grinding mode is selected, the portland cement clinker, limestone, the mixed material, gypsum and the grinding aid are ground and prepared by a ball mill or a vertical mill according to a designed proportion.

Step three, controlling the 3-day compressive strength of the 32.5 mixed Portland cement to be more than or equal to 13MPa and the 28-day compressive strengthNot less than 32.5MPa and not more than 42.5MPa, and the specific surface area is not less than 290m²/kg is less than or equal to 360m²Per kg, the mass content of the 3 um-32 um particles is more than or equal to 70 percent; the mass content of SO3 in the cement is controlled to be less than 3.5 percent and more than or equal to 2.2 percent, and the mass content of alkali is controlled to be 0.658K₂O+Na₂The content of O is less than 0.6 percent, the net slurry fluidity of the compatibility index of cement and the water reducing agent is more than or equal to 210mm, and the loss rate of 1 hour over time is less than or equal to 20 percent. And (5) warehousing and storing the finished product.

Furthermore, the compressive strength of the cement in 3 days in the third step is detected according to GB/T17671; detecting the 1-day compressive strength according to JC/T738 'Cement Strength Rapid test method' and detecting the 28-day actual compressive strength according to GB/T17671, summarizing the strength growth rules of the two through a large amount of test data, establishing a prediction formula (model), and predicting and controlling the 28-day compressive strength; selecting a polycarboxylate superplasticizer to judge the compatibility indexes of the detection and control cement and the superplasticizer; detecting the content of particles less than or equal to 3um and between 3um and 32 um.

Further, the method for detecting and controlling the uniformity of the 32.5 mixed portland cement comprises the following steps: the batching adopts computer, metering scale and intelligent network control of on-site camera shooting, and the ground cement sample is collected by a continuous automatic sampler, the CaO mass content is measured once every 1 hour, and the SO content is measured once every 2 hours₃The quality content, the detection information is fed back to the batching control system, the cement component proportion is adjusted until the characteristic values CaO and SO₃Reaching the control parameter range; the single measurement result should not exceed 2.0% of the CaO control value and the single measurement result should not exceed SO₃The deviation of the control value is within 0.3%, and the maximum value is less than 3.5%.

Furthermore, the 32.5 mixed Portland cement is specially used for preparing common or ordinary C35-C20 grade anti-crack concrete without adding admixture, the concrete components comprise 32.5 mixed Portland cement, water, aggregate and admixture, and the early anti-crack performance grade of the concrete reaches at least L-III.

Compared with the prior art, the invention has the beneficial effects that:

1) the invention discloses 32.5 mixed portland cement for anti-crack concrete in rural towns, which takes limestone with wide source as a necessary material of the 32.5 mixed portland cement, is beneficial to fully utilizing local resources, and has great significance for promoting energy conservation, consumption reduction, emission reduction, waste utilization and the like.

2) The invention controls the quality content of the raw material alkali by the alkali content (0.658K) in the cement₂O+Na₂O) is less than 0.6 percent, which is beneficial to reducing the alkali aggregate reaction of the concrete and improving the durability of the concrete. The chloride ions brought into the cement by the mixed material are controlled, and the mass content of the chloride ions calculated by the cement is less than 0.06 percent, so that the corrosion to the steel bars in the concrete is reduced; when the mixed material and the reference cement are matched according to the mass ratio of 3:7, the ratio of the 28-day compressive strength value of the test mixture to the reference cement is more than or equal to 65%, and the variety and the technical indexes of raw materials are optimized, so that the requirement on the early strength of the cement is met, and the continuous increase of the later strength of the cement can be ensured. The net slurry fluidity of the compatibility index of cement and the water reducing agent is controlled to be more than or equal to 210mm, and the time loss of 1 hour is controlled to be less than or equal to 20 percent, so that the concrete has good working performance when the 32.5 mixed Portland cement is used for preparing concrete.

3) The grinding aid is doped, so that the grinding aid plays a role in grinding aid, more importantly, the grinding aid is compounded with related component raw materials, the activity of the ferro-aluminate mineral in the clinker can be activated, the using amount of the clinker is reduced, and the grinding aid also plays an important role in protecting reinforcing steel bars in concrete and preventing or reducing corrosion of reinforcing steel bars such as chloride ions and the like in an alkaline environment by virtue of the borate and the tetra-sodium hydroxy ethylidene diphosphonate after hydrolysis, so that the cracking of the concrete is reduced.

4) The invention provides 32.5 mixed portland cement for common structural concrete and a production technical scheme thereof, all admixtures in the concrete are added in the form of mixed materials when being produced in a cement plant, the 32.5 mixed portland cement does not need to be added with concrete admixtures again when being used for preparing C35 and the following common structural concrete, only water, sand, stone and concrete admixtures need to be added, the mixed materials are added from two places of the cement plant and a mixing plant and are adjusted to be added at one place of the cement plant, so that the engineering quality is controlled and improved, the mixed materials and the quality can be reasonably screened and controlled, and the performance parameters of the structural concrete are effectively ensured to meet the requirements.

5) The invention is especially suitable for the engineering of beam, column and cast plate concrete structure, which is not suitable for the operation in towns and villages and inconvenient for traffic or is not suitable for mechanized operation, has less consumption of disposable cement, and has great effects of improving the homogeneity of a cementing material system, reducing engineering cracks, improving the compactness, the homogeneity, the workability and the durability of concrete, prolonging the service life of buildings, reducing energy consumption, being economical, simplifying the preparation process and improving the working efficiency.

6) CaO and SO of the invention₃As a technical scheme for uniformity characteristic value control and proportioning optimization, the method adjusts actual proportioning and control parameters in time so as to give full play to the effects of optimized compounding and superposition of each component of the cement.

7) The invention grinds the mixed material to a specific surface area of more than or equal to 330m²The mass ratio of the mixed material to the reference cement is 3:7, and the ratio of the 28-day compressive strength value of the test mixture to the reference cement is not less than 65%. Because the mixing amount of the mixed material in the 32.5 mixed Portland cement is higher, the activity, the optimized compounding and the overlapping effect of the mixed material directly influence the quality and the performance of the 32.5 mixed Portland cement and concrete, the related technical indexes of the mixed material must be controlled, and the optimized compounding and the overlapping effect are fully exerted.

Drawings

FIG. 1 is a schematic view of a preparation process of 32.5 mixed portland cement for anti-crack concrete in rural towns and villages.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

A32.5 mixed silicate cement for anti-crack concrete in rural towns and villages adopts a preparation method of mixing and grinding clinker and other raw materials, and the mixture ratio is as follows according to the mass of the cement: 40 to 65 percent of Portland cement clinker, 3.0 to 6.0 percent of gypsum, 10 to 25 percent of limestone, 6 to 45 percent of mixed material and 0.05 to 0.5 percent of grinding aid;

the portland cement clinker is calcined clinker of a predecomposition kiln, and the control parameters of the portland cement clinker are as follows: except meeting the requirement of GB/T21372, the compressive strength of the material is more than or equal to 12MPa in 1 day, more than or equal to 28MPa in 3 days, more than or equal to 55MPa in 28 days, the tricalcium aluminate content is less than or equal to 8 percent, the silicate mineral content is more than or equal to 68 percent, the tricalcium silicate content is less than or equal to 58 percent, the magnesium oxide content is less than 5 percent, the free calcium oxide content is less than or equal to 1.5 percent, and the alkali content is (0.658K₂O+Na₂O) is less than 0.6 percent.

The 32.5 mixed Portland cement is particularly suitable for ordinary or general structural concrete engineering in rural areas and towns, and can also be used for large-volume concrete structures, and ultralong concrete structures and hyperstatic concrete structural engineering which particularly focus on the pre-waterproof thermal energy effect and the shrinkage effect. All the admixtures in the concrete are added when cement finished products are produced in a cement plant, and no admixture is needed to be added in a stirring station or a preparation site, and only water, sand, stone and concrete admixtures are needed to be added; the addition of the mixed material from two places of a cement plant and a mixing plant is adjusted to one place of the cement plant, which is beneficial to controlling the quality of the cementing material and the concrete.

Preferably, the mixed material comprises one or more of granulated blast furnace slag, calcined coal gangue and fly ash, 0-8% of sandstone, phosphorous slag, kiln ash, steel slag or other waste residues meeting the requirements are allowed to replace the mixed material in the mixed material, and the mixed material is ground until the specific surface area is more than or equal to 330m²/kg is less than or equal to 380m²Kg, the ratio of the 28-day compressive strength value of the mixture with the mass ratio of the mixed material to the reference cement being 3:7 to the reference cement is more than or equal to 65 percent; the alkali content in the mixed material is equal to (0.658K)₂O+Na₂O) is less than 0.6 percent, and the content of chloride ions is less than 0.06 percent.

By controlling the quality and the mixing amount of the mixed materials, the proportion of the 32.5 mixed Portland cement is optimized aiming at different engineering requirements on the premise that the working performance of the concrete is not reduced and the durability such as the impermeability, the carbonization resistance, the corrosion resistance and the like of the concrete can not be reduced, and the condition of preparing the common structural concrete on the spot is met.

Preferably, the grinding aid is prepared by compounding one or two of triisopropanolamine cyclic borate and diethanol monoisopropanolamine cyclic borate with tetra sodium hydroxy ethylidene diphosphonate.

Preferably, the limestone meets the requirements that the content of aluminum oxide is less than or equal to 2.5 percent and the content of calcium carbonate is more than 80 percent; the gypsum is required to meet the requirements of GB/T5483 and GB/T21371.

A preparation method of 32.5 mixed silicate cement for anti-crack concrete in rural towns adopts a mode of mixing and grinding clinker and other raw materials; grinding aid is added during grinding;

firstly, selecting raw materials, detecting portland cement clinker, mixed materials, gypsum, limestone and grinding aids, and putting the raw materials which meet the regulations into the next production process.

Step three, controlling the 3-day compressive strength of the 32.5 mixed Portland cement to be more than or equal to 13MPa, the 28-day compressive strength to be more than or equal to 32.5MPa and less than or equal to 42.5MPa, and the specific surface area to be more than or equal to 290m²/kg is less than or equal to 360m²The content of 3-32 um particles is more than or equal to 70 percent; the content of SO3 in the cement is controlled to be less than 3.5 percent and more than or equal to 2.2 percent, and the content of alkali is controlled to be (0.658K)₂O+Na₂O) is less than 0.6 percent, the net slurry fluidity of the compatibility index of the cement and the water reducing agent is more than or equal to 210mm, and the loss rate of 1 hour over time is less than or equal to 20 percent. And (5) warehousing and storing the finished product.

Preferably, the compressive strength of the cement in the third step for 3 days is detected according to GB/T17671; detecting the 1-day compressive strength according to JC/T738 'Cement Strength Rapid test method' and detecting the 28-day actual compressive strength according to GB/T17671, summarizing the strength growth rules of the two through a large amount of test data, establishing a prediction formula (model), and predicting and controlling the 28-day compressive strength; selecting a polycarboxylate superplasticizer to judge the compatibility indexes of the detection and control cement and the superplasticizer; detecting the mass ratio of the micro powder less than or equal to 3um and the content of the particles between 3um and 32 um.

Preferably, the method for detecting and controlling the uniformity of the 32.5 mixed portland cement comprises the following steps: the ingredients are mixed by a computer and a metering scale,The intelligent network control of on-site camera shooting is realized by collecting ground cement samples through a continuous automatic sampler, measuring the CaO content once every 1 hour and measuring the SO content once every 2 hours₃The content and the detection information are fed back to a batching control system, and the cement component proportion is adjusted until the characteristic values CaO and SO₃Reaching the control parameter range; the single measurement result should not exceed 2.0% of the CaO control value and the single measurement result should not exceed SO₃The deviation of the control value is within 0.3%, and the maximum value is less than 3.5%.

Preferably, the 32.5 mixed Portland cement is specially used for preparing common or ordinary C35 and below grade anti-crack concrete without adding admixture, the concrete components comprise 32.5 mixed Portland cement, water, aggregate and admixture, the early stage anti-crack performance grade of the concrete reaches at least L-III, and the aggregate comprises sand and stone.

The masonry 32.5 cement can be directly stirred on site, and does not need to be added with admixture, but can only be used for masonry, plastering and cushion layer engineering. When 42.5 cement is used for preparing concrete with the structure of C35 and the following structures, the admixture is required to be added.

The reference cement is Portland cement which is ground by Portland cement clinker and gypsum and has the strength grade of more than 42.5, and no mixed material is added. The standards of the industries such as highways, railways, construction works, harbor works and the like are also stipulated, and the quality inspection and selection of the mixed materials of the concrete admixture are carried out by using standard cement. The 28-day compressive strength of the C35, C30, C25, C20 and C15 concrete is respectively required to be more than or equal to 40MPa, more than or equal to 35MPa, more than or equal to 30MPa, more than or equal to 25MPa and more than or equal to 20 MPa.

The 32.5 mixed portland cement of the invention is used for C35 and following common structural concrete projects, refers to structural parts of beams, columns, plates, walls, ladders and the like of buildings which are mainly made of concrete, and comprises a plain concrete structure, a reinforced concrete structure and a prestressed concrete structure; with considerable load bearing, compression resistance and other requirements.

In the embodiment, a clinker and other raw materials are mixed and ground, and the main equipment is a ball mill or a vertical mill.

In the following examples, a special air stirring homogenizing chamber may be provided (but not limited) or the stirring time may be increased to reach the control index for shipment.

Example 1

A32.5 mixed Portland cement for anti-crack concrete in rural towns and villages comprises the following components in percentage by weight: 65% of silicate cement clinker, 6% of gypsum, 15% of limestone, 13.95% of mixed material (slag and granulated blast furnace slag) and 0.05% of grinding aid.

The portland cement clinker is calcined clinker of a predecomposition kiln, and the control parameters of the portland cement clinker are as follows: the 1-day compressive strength is more than or equal to 12MPa, the 3-day compressive strength is more than or equal to 28MPa, the 28-day compressive strength is more than or equal to 55MPa, the mass content of tricalcium aluminate is less than or equal to 8 percent, the mass content of silicate mineral is more than or equal to 68 percent, the mass content of tricalcium silicate is less than or equal to 58 percent, the mass content of magnesium oxide is less than 5 percent, the mass content of free calcium oxide is less than or equal to 1.5 percent, and the₂O+Na₂O) is less than 0.6 percent.

32.5 the mixed Portland cement also comprises a mixed material of granulated blast furnace slag, calcined coal gangue and fly ash, wherein 8 percent of other waste residues meeting the requirements in the mixed material, such as sandstone, phosphorous slag, kiln dust and steel slag, replace the mixed material, and the mixed material is ground to be more than or equal to 330m in specific surface area²/kg is less than or equal to 380m²Per kg; the alkali content in the mixed material is equal to (0.658K)₂O+Na₂O) is less than 0.6 percent, the mass content of chloride ions is less than 0.06 percent, and the ratio of the 28-day compressive strength value of the mixture of the test mixed material and the reference cement with the mass ratio of 3:7 to the reference cement is more than or equal to 65 percent.

32.5 the mixed Portland cement also comprises a grinding aid, and the grinding aid is formed by compounding two of triisopropanolamine cyclic borate and diethanol monoisopropanolamine cyclic borate with hydroxyethylidene tetrasodium diphosphonate.

The limestone meets the requirements that the mass content of aluminum oxide is less than or equal to 2.5 percent and the mass content of calcium carbonate is more than 80 percent; the gypsum is required to meet the requirements of GB/T5483 and GB/T21371.

Step three, controlling the 3-day compressive strength of the 32.5 mixed Portland cement to be more than or equal to 13MPa, the 28-day compressive strength to be more than or equal to 32.5MPa and less than or equal to 42.5MPa, and the specific surface area to be more than or equal to 290m²/kg is less than or equal to 360m²Per kg, the mass content of the 3 um-32 um particles is more than or equal to 70 percent; the mass content of SO3 in the cement is controlled to be less than 3.5 percent and more than or equal to 2.2 percent, and the mass content of alkali is controlled to be 0.658K₂O+Na₂The content of O is less than 0.6 percent, the net slurry fluidity of the compatibility index of cement and the water reducing agent is more than or equal to 210mm, and the loss rate of 1 hour over time is less than or equal to 20 percent. And (5) warehousing and storing the finished product.

Controlling the 3-day compressive strength of the cement in the third step according to GB/T17671 detection; detecting the 1-day compressive strength according to JC/T738 'Cement Strength Rapid test method' and detecting the 28-day actual compressive strength according to GB/T17671, summarizing the strength growth rules of the two through a large amount of test data, establishing a prediction formula (model), and predicting and controlling the 28-day compressive strength; selecting a polycarboxylate superplasticizer to judge the compatibility indexes of the detection and control cement and the superplasticizer; the mass ratio of the micro powder less than or equal to 3um and the content of the particles between 3um and 32um are detected by a laser particle size analyzer.

The method for detecting and controlling the uniformity of the 32.5 mixed Portland cement comprises the following steps: the batching adopts computer, metering scale and intelligent network control of on-site camera shooting, and the ground cement sample is collected by a continuous automatic sampler, the CaO mass content is measured once every 1 hour, and the SO content is measured once every 2 hours₃The quality content, the detection information is fed back to the batching control system, the cement component proportion is adjusted until the characteristic values CaO and SO₃Reaching the control parameter range; the single measurement result should not exceed 2.0% of the CaO control value and the single measurement result should not exceed SO₃The deviation of the control value is within 0.3%, and the maximum value is less than 3.5%.

The concrete of the embodiment comprises the components of 32.5 mixed portland cement, water, gravel aggregate and an additive, is specially used for concrete with crack resistance grade of common or ordinary C35 and below, and does not need to be added with an additive, and the early crack resistance grade of the concrete reaches at least L-III.

Example 2

A32.5 mixed Portland cement for anti-crack concrete in rural towns and villages comprises the following components in percentage by weight: 40% of portland cement clinker, 3% of gypsum, 25% of limestone, 31.5% of mixed materials (fly ash and granulated blast furnace slag) and 0.5% of grinding aid. The component materials meet the relevant standards and requirements.

The rest is the same as example 1.

Example 3

A32.5 mixed Portland cement for anti-crack concrete in rural towns and villages comprises the following components in percentage by weight: 52.5 percent of Portland cement clinker, 5 percent of gypsum, 10 percent of limestone, 32 percent of mixed material (granulated blast furnace slag) and 0.5 percent of grinding aid. The component materials meet the relevant standards and the aforementioned requirements. The rest is the same as example 1.

Example 4

A32.5 mixed Portland cement for anti-crack concrete in rural towns and villages comprises the following components in percentage by weight: 60% of portland cement clinker, 4.8% of gypsum, 5% of limestone, 30.15% of mixed material and 0.05% of grinding aid. The component materials meet the relevant standards and the aforementioned requirements. The rest is the same as example 1.

Example 5

A32.5 mixed Portland cement for anti-crack concrete in rural towns and villages comprises the following components in percentage by weight: 65% of portland cement clinker, 4.5% of gypsum, 10% of limestone, 20.4% of mixed material (granulated blast furnace slag) and 0.1% of grinding aid. The component materials meet the relevant standards and the aforementioned requirements. The rest is the same as example 1.

Example 6

A32.5 mixed Portland cement for anti-crack concrete in rural towns and villages comprises the following components in percentage by weight: 52.0 percent of Portland cement clinker, 3.0 percent of gypsum, 14.5 percent of limestone, 30.0 percent of mixed material (granulated blast furnace slag and first-grade fly ash) and 0.5 percent of grinding aid. The component materials meet the relevant standards and the aforementioned requirements. The rest is the same as example 1.

Example 7

Rural area32.5 mixed Portland cement for villages, towns and anti-crack concrete, which comprises the following components in percentage by weight: 40% of portland cement clinker, 6.0% of gypsum, 20% of limestone and a mixed material (the specific surface area is 335 m)²/kg calcined coal gangue) 33.5 percent and grinding aid 0.5 percent. The mass ratio of the mixed material to the reference cement in the component materials is 3:7, and the ratio of the 28-day compressive strength value of the test mixture to the reference cement is 57.5%. Other component materials meet the relevant standards and requirements, otherwise the same as in example 1.

Example 8

A32.5 mixed Portland cement for anti-crack concrete in rural towns and villages comprises the following components in percentage by weight: 40% of portland cement clinker, 6.0% of gypsum powder, 20% of limestone and mixed material (the specific surface area is 348 m)²/kg three-level fly ash) 33.5 percent and grinding aid 0.5 percent. The mass ratio of the mixed material to the reference cement in the component materials is 3:7, and the ratio of the 28-day compressive strength value of the test mixture to the 28-day compressive strength value of the reference cement is 60%. Other constituent materials meet the relevant standards and the aforementioned requirements, otherwise as in example 1.

Example 9

Chemical and physical property tests were performed on the 32.5 blended portland cements of examples 1-8 above, respectively, and the test results are shown in tables 1-2 below, and the test results for the strength and early cracking of concrete formulated with the 32.5 blended portland cements of examples 1-8 above are shown in tables 3-5 below.

TABLE 1 Performance test results of 32.5 mixed Portland cement for anti-crack concrete in rural towns

TABLE 2 Performance test results of 32.5 mixed Portland cement for anti-crack concrete in rural towns

The data in the table 1-2 show that when the mass ratio of the mixed material to the reference cement is 3:7, the ratio of the 28-day compressive strength value of the test mixture to the reference cement is greater than or equal to 65%, the compressive strength of the prepared cement is greater than 32.5MPa, and the requirement of preparing structural concrete is met.

Table 3 formulated C20 concrete Properties

Table 4 Properties of formulated C25 concrete

Properties of C30 concrete formulated in Table 5

As can be seen from tables 3-5, the concrete prepared by using 32.5 mixed portland cement has less early cracking phenomenon, the crack resistance grades reach L-III and L-IV grades, the indexes such as strength and the like are uniform and stable, and the concrete with the structural concrete, C35, C30, C25, C20 and C15, the 28-day compressive strength of the concrete is respectively required to be more than or equal to 40MPa, more than or equal to 35MPa, more than or equal to 30MPa, more than or equal to 25MPa and more than or equal to 20 MPa.

Example 10

Respectively adopting a plurality of mixed materials: tests were carried out on pozzolanic materials (slag, calcined coal gangue), fly ash (first, second, third grade), granulated blast furnace slag; respectively adopting different mixed material fineness, and respectively grinding the three materials to a specific surface area of 330m by a test phi 500mm small ball mill²/kg-380m²Between/kg.

Selecting standard cement, and comparing sample proportion: 30% of mixed material and 70% of standard cement. The test results of the quality index of the mixed material are shown in Table 6:

TABLE 6 quality index test results of the mixed materials

When the mixed material is selected, the mixed material with different varieties, sources and properties is sampled and detected, and the varieties and quality of the mixed material and relevant technical indexes for control are screened and applied.

Example 11

A test 32.5 sample of mixed cement without grinding aid is prepared, and the mixed cement is ground by a test phi 500mm small ball mill according to the proportion of example 1, wherein 65% of Portland cement clinker, 6% of gypsum, 15% of limestone and 14.0% of mixed materials (slag and granulated blast furnace slag) are referred to as blank reference samples for short.

A32.5 sample of blended cement, which was tested by adding a grinding aid, was prepared and ground in a pellet mill having a diameter of 500mm in the same ratio as in example 1, with 65% of portland cement clinker, 6% of gypsum, 15% of limestone and 13.95% of a blended material (slag, granulated blast furnace slag). 0.05% of grinding aid (which is compounded by triisopropanolamine cyclic borate, diethanol monoisopropanolamine cyclic borate and hydroxyethylidene diphosphonic acid tetrasodium in a ratio of 1: 1: 0.5), which is called a comparative sample for short.

A60-liter single horizontal shaft type concrete mixer is used for preparing a concrete mixture test sample according to the following mass mixing ratio, the basic mixing ratio is that the sample cement comprises water, sand and stone in a ratio of 1: 0.55: 2.35: 3.25, on the basis of the basic mixing ratio, concrete of different grades keeps the ratio of the stone, the cement and the water unchanged in the test, the cement amount is increased, the sand is reduced in an equivalent manner, after the cement, the sand and the stone are put into the test sample at one time, the water and additives are added within 15 seconds, 30 liters of concrete is prepared to prepare a disc of concrete mixture, samples are taken according to GB/T50081 'ordinary concrete mechanical property test method', cubic test blocks of 150mm × 150mm × 150mm are respectively used for measuring the compressive strength of the test sample for 7 days and 28 days, an early crack resistance test is carried out according to GB/T50082-2009 'ordinary concrete long-term property and durability test method standard', and test results are shown in Table 7.

TABLE 7 influence of grinding aid on early crack resistance of cement concrete and the like

As can be seen from Table 7, the early cracking area ratio of the comparative sample doped with the grinding aid is obviously lower than that of the undoped blank sample, and when concrete of different grades is prepared, the early cracking area ratio is reduced from L-IV to L-III along with the increase of the cement dosage, and the test conclusion of Table 7 verifies that the grinding aid has the effect of improving and improving the early cracking resistance of the concrete.

The invention provides a preparation method of 32.5 mixed portland cement for rural towns and anti-cracking common structural concrete, wherein a cementing material in the structural concrete is prepared by cement production enterprises (all mixed material components are added in the cement preparation), a large amount of admixture is not required to be added secondarily when the concrete is prepared, and the anti-cracking effect is achieved, so that the requirement of large-scale on-site stirring and concrete preparation in economically undeveloped areas such as towns and rural areas and areas not covered by commercial concrete stations is met, or the concrete structural engineering such as inconvenient traffic or unsuitable mechanical operation, small using amount of disposable cement, but needing beaming, column making, floor slab pouring and the like is realized, the anti-cracking performance is obviously improved, and the anti-cracking grades reach L-III and L-IV.

The present invention is directed to the different types and customer needs of 32.5 blended portland cements for general structural concrete of moderate to low strength, and the examples are described to facilitate the understanding and use of the invention by those of ordinary skill in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments. Those skilled in the art should appreciate that many modifications and variations are possible in light of the above teaching without departing from the scope of the invention.

Claims

1. A32.5 mixed silicate cement for anti-crack concrete in rural towns is characterized in that clinker with parameters required to be controlled in production or outsourcing is adopted, mixed with other raw materials and ground to prepare the cement, and the mixture ratio is as follows according to the mass of the cement: 40-65% of Portland cement clinker, 3.0-6.0% of gypsum, 10-25% of limestone, 6-45% of mixed material and 0.05-0.5% of grinding aid;

the portland cement clinker is calcined clinker in a predecomposition kiln, and the control parameters are as follows: except meeting the requirements of GB/T21372, the compressive strength of the material is more than or equal to 12MPa in 1 day, more than or equal to 28MPa in 3 days, more than or equal to 55MPa in 28 days, the mass content of tricalcium aluminate is less than or equal to 8 percent, the mass content of silicate mineral is more than or equal to 68 percent, the mass content of tricalcium silicate is less than or equal to 58 percent, the mass content of magnesium oxide is less than 5 percent, the mass content of free calcium oxide is less than or equal to 1.5 percent, and the alkali content is₂O+Na₂O is less than 0.6 percent; the mixed material comprises one or more of granulated blast furnace slag, calcined coal gangue and fly ash, wherein 0-8% of sandstone, phosphorus slag, kiln dust, steel slag or other waste residues meeting the requirements are allowed to replace the mixed material, and the mixed material is ground to be more than or equal to 330m in specific surface area²/kg is less than or equal to 380m²Kg, the ratio of the 28-day compressive strength value of the mixture with the test mixture and the reference cement in the mass ratio of 3:7 to the reference cement is more than or equal to 65 percent; the alkali content in the mixed material is 0.658K₂O+Na₂The content of O is less than 0.6 percent, and the mass content of chloride ions is less than 0.06 percent; the grinding aid is prepared by compounding any one or two of triisopropanolamine cyclic borate and diethanol monoisopropanolamine cyclic borate with tetra sodium hydroxyethylidene diphosphonate.

2. The 32.5 mixed portland cement for rural towns and anti-crack concrete according to claim 1, wherein the limestone has an aluminum oxide content of less than or equal to 2.5% and a calcium carbonate content of more than 80%; the gypsum is required to meet the requirements of GB/T5483 and GB/T21371.

3. The method for preparing 32.5 mixed portland cement for anti-crack concrete in rural towns and villages according to any one of claims 1-2, characterized in that a mode of mixing and grinding clinker and other raw materials is adopted;

selecting raw materials, detecting portland cement clinker, mixed materials, gypsum, limestone and grinding aids, and putting the raw materials meeting the regulations into the next production procedure;

step two, when a mixed grinding mode is selected, the portland cement clinker, limestone, a mixed material, gypsum and a grinding aid are prepared by grinding through a ball mill or a vertical mill according to a designed proportion;

step three, controlling the 3-day compressive strength of the 32.5 mixed Portland cement to be more than or equal to 13MPa, the 28-day compressive strength to be more than or equal to 32.5MPa and less than or equal to 42.5MPa, and the specific surface area to be more than or equal to 290m²/kg is less than or equal to 360m²Per kg, the mass content of the 3 um-32 um particles is more than or equal to 70 percent; controlling SO in cement₃The content is less than 3.5% and more than or equal to 2.2%, and the alkali content is 0.658K₂O+Na₂The O is less than 0.6 percent, the net slurry fluidity of the compatibility index of the cement and the water reducing agent is more than or equal to 210mm, the loss rate of 1 hour is less than or equal to 20 percent, and the finished product is stored in a warehouse.

4. The preparation method of 32.5 mixed portland cement for rural towns and anti-crack concrete according to claim 3, wherein the compressive strength of the cement in 3 days in the third step is detected according to GB/T17671; detecting the 1-day compressive strength according to JC/T738 'Cement Strength Rapid test method' and detecting the 28-day actual compressive strength according to GB/T17671, summarizing the strength growth rules of the two through a large amount of test data, establishing a prediction formula or a model, and predicting and controlling the 28-day compressive strength; controlling the compatibility index of cement and a water reducing agent, and judging the water reducing agent by selecting a polycarboxylate high-efficiency water reducing agent; detecting the particle content less than or equal to 3um and between 3um and 32 um.

5. The preparation method of 32.5 mixed portland cement for rural towns and anti-crack concrete according to claim 4, wherein the method for detecting and controlling the uniformity of 32.5 mixed portland cement comprises the following steps: the ingredients are intelligently controlled by computer, metering scale and on-site camera shooting through networkingCollecting ground cement sample by a continuous automatic sampler, measuring CaO content once every 1 hour and measuring SO content once every 2 hours₃The content and the detection information are fed back to a batching control system, and the cement component proportion is adjusted until the characteristic values CaO and SO₃Reaching the control parameter range; the single measurement result should not exceed 2.0% of the CaO control value and the single measurement result should not exceed SO₃The deviation of the control values is 0.3%, the maximum value is less than 3.5%.

6. The 32.5 mixed Portland cement is specially used for preparing general or ordinary C35 and below grade concrete according to any one of claims 1-2, wherein no admixture is needed, the concrete components comprise 32.5 mixed Portland cement, water, aggregate and an additive, and the early-stage crack resistance grade of the concrete reaches at least L-III.