CN103553494A - C170 strength-grade concrete for formed steel concrete composite structure - Google Patents

Abstract

The invention discloses a C170 strength-grade concrete for a formed steel concrete composite structure, which is composed of 465 parts of cement, 816 parts of fine aggregate, 1094 parts of coarse aggregate, 96 parts of water, 16 parts of concrete superplasticizer, 1 part of defoaming agent, 70 parts of silicon powder, 115 parts of fly ash and 6 parts of activator. The preparation method comprises the following steps: blending the concrete superplasticizer and activator into weighed water to obtain a mixture, sequentially adding the fine aggregate and 1/3 of the mixture into a stirrer according to parts by weight, and stirring; adding the coarse aggregate and 1/3 of the mixture, and stirring; adding the cement, silicon powder and fly ash, and stirring; and adding the defoaming agent and the rest of mixture, stirring and discharging. The concrete can obviously improve the bonding property between the formed steel and the concrete in a natural state, effectively displays the respective mechanical properties and the synergic working performance of the steel and concrete, greatly enhances the loading capacity, service performance and durability of the structural member, and has favorable working performance and economical efficiency.

Description

A kind of concrete with C170 strength grade for steel-concrete composite structure

technical field

The invention belongs to the technical field of building materials, and relates to an ultra-high-strength high-performance concrete with a strength grade of C170 for steel-concrete composite structures.

Background technique

The invention of Portland cement in 1824 led to the rapid development of concrete technology. Its consumption is large and its scope of application ranks the highest in the world. Although concrete is a traditional man-made building material, because of its irreplaceable advantages (abundant raw materials, simple production process, high cost performance, etc.) and the continuous progress of concrete material science and technology, concrete has become the main body of civil engineering materials. , It will also be one of the indispensable main materials in future civil engineering and national construction. At the same time, with the continuous expansion of the city, the continuous increase of the population, the continuous increase of the land price, the harsh environment of the building, the continuous improvement of the construction technology and the rapid development of the economy, the buildings are more and more open to the air, underground and other places. Water extension, that is, the development of (super) high, (super) long span, underground, lightweight and heavy-duty structures, especially the development of steel concrete structures in super high, super long span, underground, sea or underwater Applications in novel or giant construction engineering fields such as miniaturization and lightweighting have higher and higher requirements for concrete as a building material. Therefore, the research and practice of super-strengthening and super-durability of concrete will become the development trend in this field.

Steel-concrete composite structure (SRC structure for short) is a main form of steel-concrete composite structure. It is more and more widely used in long-span, heavy-duty structures, underground, underwater or offshore engineering and high-rise and super high-rise buildings in earthquake/typhoon areas. Compared with the steel structure, the SRC structure can save a lot of steel, enhance the rigidity of the section, overcome the shortcomings of the steel structure such as poor fire resistance, corrosion resistance, durability, and easy buckling instability, so that the ability of the steel can be fully utilized; compared with ordinary reinforced concrete Compared with the RC structure (referred to as RC structure), the steel concrete structure can reduce the cross-sectional size of the components, reduce the occupied space, and thus increase the building use space; in construction, the steel skeleton of the steel concrete structure itself can be used as concrete hanging formwork 1. The skeleton of the sliding form not only greatly simplifies the formwork support, but is also a supporting system that bears all construction loads (including hanging, sliding formwork and poured concrete); in addition, due to the advantages of strong integrity and good ductility of the SRC structure, It can greatly improve the brittleness of reinforced concrete under shear failure, significantly improve the seismic performance of the structure, and the bearing capacity and ductility are greatly improved compared with the RC structure. Therefore, in developed countries such as Japan, Europe and the United States, the SRC structure with good seismic performance has become a recognized new type of seismic structure system, and is called the four major structures together with steel structure, wood structure, and reinforced concrete structure. my country is also an earthquake-prone country. Most of the areas are earthquake areas, and some are located in high-intensity and frequent-earthquake areas. It is of great practical significance to promote SRC structures in these areas. Therefore, the SRC structure has very broad application prospects in our country, especially with the continuous enhancement of my country's economic strength and the successful development of (ultra) high-strength steel and (ultra) high-strength high-performance concrete (which are recognized materials in the 21st century) It will greatly promote the promotion, application and development of this structural system. Studies have shown that the higher the strength of ultra-high-strength high-performance concrete, the higher its brittleness and poorer ductility. Under high stress or complex stress state, the failure process of ultra-high-strength high-performance concrete components will be controlled by brittleness. Reduced reliability. However, the application of this new type of high-tech concrete in steel-concrete composite structures (referred to as SRC structures), that is, steel-shaped ultra-high-strength high-performance concrete composite structures (referred to as USUPSRC structures), can maximize strengths and circumvent weaknesses, and overcome the brittleness and ductility of ultra-high-strength high-performance concrete. The weakness of poor performance enables it to give full play to its superior performance and economic benefits.

In the SRC structure, the good bonding between steel and concrete is the basis for ensuring the coordinated work of steel and concrete in SRC components. The three material elements of steel, steel and concrete work together to resist various effects, so that they can be fully utilized. its advantages. However, one of the significant differences between the SRC structure and the RC structure is that the bond between the steel and concrete is much smaller than the bond between the steel and the concrete, and the bond between the steel and the ordinary concrete is only about equal to that of the smooth steel. 45% of knot force. Many domestic and foreign experimental research results show that there is a bond-slip phenomenon between steel and concrete, and it has a significant impact on the mechanical properties and even the bearing capacity of SRC components. Therefore, how to ensure that steel and concrete work together effectively has become one of the focuses of SRC structural research. At present, there are generally two ways to deal with the bond-slip problem between steel and concrete in engineering design: one is to add a certain number of shear connectors on the surface of the component through calculation, which will inevitably cause inconvenience in construction. It increases the cost, and it is easy to cause defects such as congenital micro-cracks in the concrete; the second is not to set up or only a small amount of shear connectors, and the influence of bond-slip is considered in the calculation of the bearing capacity, and the bearing capacity of the components is correspondingly reduced. There must be uneconomical factors. On the other hand, in the design of engineering structures, there is a common phenomenon of emphasizing strength and ignoring durability. There have been many problems in the safety and durability of concrete structures during use at home and abroad. Some concrete structure projects completely lose their function and bearing capacity due to alkali-aggregate reaction, chloride ion erosion and other reasons when the service life is less than half of the design period. Some projects even collapse partially or overall, causing casualties or damage to building facilities. Therefore, in the USUPSRC structure, improving the natural bonding performance between the steel section and ultra-high-strength high-performance concrete can ensure that the section steel and ultra-high-strength high-performance concrete can be effectively bonded without setting up a small amount of shear connectors on the surface of the steel section or only according to the structural requirements. The study of collaborative work is of great significance; at the same time, the durability of concrete structure engineering has increasingly attracted people's close attention and great attention, and has become a problem to be solved.

The strength grades of concrete used for steel-concrete composite structures in the prior art include high-strength high-performance concrete of C60, C70, C80, C90 and C100 and the preparation technology of ultra-high-strength high-performance concrete of C110, C120, C130, C140 and C150, the above-mentioned Concrete of each strength grade significantly improves the bonding performance between steel and (ultra) high-strength concrete, and improves the durability of the structure; however, there are still ultra-high-strength high-performance concrete that cannot be extended to higher strength, and will When it is used in steel-concrete composite structures, it cannot solve the problem of poor natural bonding between steel and ultra-high-strength high-performance concrete, so it cannot meet the needs of civil engineering buildings extending to the air, underground and water, that is, super-high buildings, super-large spans The application and development trend of modernization, undergroundization, sea or underwater, ultra-durability and heavy, giant and novel structural engineering. In addition, in the prior art, there are also some preparation technologies for ultra-high strength and ultra-durability of concrete, but none of them involve or solve the poor natural bonding performance between steel and ultra-high-strength high-performance concrete when used in SRC structures The problem.

Contents of the invention

The object of the present invention is to provide a super-high-strength high-performance concrete with a strength grade of C170 for steel-concrete composite structures. The concrete is applied in the steel-concrete composite structure, which can significantly improve the bonding performance between the steel and concrete under the natural state (that is, no setting on the surface of the steel or only a small amount of shear connectors according to the structural requirements), and effectively play the role of steel and concrete. The mechanical properties and mutual synergistic performance of the two materials of concrete can greatly improve the bearing capacity and service performance of structural members; in addition, the concrete can improve the durability of the structure, and has good working performance, high volume stability and economy.

In order to solve the above-mentioned technical problems, the present invention is implemented in the following way: a concrete for steel-concrete composite structure C170 strength grade, characterized in that the mix ratio of the concrete is (unit: kg/m ³ ):

Cement: fine aggregate: coarse aggregate: water: concrete superplasticizer: defoamer: silica fume: fly ash: activator (kg/m ³ )=465:816:1094:96:16:1: 70:115:6.

The cement is selected from 625R ordinary Portland cement with stable quality and good performance. Before use, it needs to carry out the adaptability test between the two with polycarboxylate concrete superplasticizer. The test method adopts the current building materials industry standard " Cement and superplasticizer compatibility test method "JC/T1083-2008 method, and select cement varieties with good compatibility with polycarboxylate concrete superplasticizers. The performance indicators of the selected cement (including fineness, SO ₃ content, MgO content, initial setting time, final setting time, 3-day strength, 28-day strength) should not be lower than the requirements of the current relevant national standards, and the cement with less alkali content, Cement with low heat of hydration and low water demand.

The fine aggregate is medium-to-coarse river sand with smooth particles, hard texture and good gradation. The quality of the sand should not be lower than the current building material industry standard "Sand and Stone Quality and Inspection Method Standard for Ordinary Concrete" JC/T52 -High-quality sand standards stipulated in 2006 and the national standard "Sand for Construction" GB/T14684-2001. The fineness modulus is between 2.8 and 3.2, the mud content and mud block content should not be greater than 0.4%, and the chloride ion content should not be greater than 0.05% (based on the mass of dry sand).

The coarse aggregate is artificial crushed stone mainly composed of granite and basalt, which is dense and hard, high in strength, rough in surface, approximately spherical in grain shape, small in needle flake content, and well graded. The quality of the crushed stone should be Not lower than the requirements of relevant standards such as JC/T52-2006, the current building materials industry standard "Sand and Stone Quality and Inspection Method Standards for Ordinary Concrete". The cubic compressive strength of aggregate parent rock should not be lower than 140MP. The maximum particle size should be controlled at 10mm, the mud content should not be greater than 0.2% (by mass), the mud block content should not be greater than 0.1% (by mass), and the content of needle and flake particles should not be greater than 0.5% (by mass). mass meter), and must not be mixed with weathered particles. When preparing the concrete, the continuous particle size gravel Φ5～Φ10 is used for feeding.

After a lot of tentative comparison tests and compatibility tests with cement, the high-efficiency water reducer selected in this invention is a polycarboxylate concrete superplasticizer, and its quality should not be lower than the current national standard "Concrete Admixture" GB8076- 2008 and other relevant standards require that the water reducing rate of the selected high-efficiency water reducing agent should be greater than 30%. The maximum saturated content of the selected high-efficiency water reducer is not less than 2.5% of the total amount of cementitious materials. The same mixing method is adopted, and a compatibility test with the selected cement variety is required before use.

Described defoamer selects AGITANP803 powder defoamer.

The silica fume adopts 30nm nano silica fume and submicron silica fume with a mass ratio of 3:2, and its quality should not be lower than that of the national standard "Mineral Admixtures for High-Strength and High-Performance Concrete" GB/T18736-2002 and other relevant standards. According to regulations, at the same time, the moisture content of 30nm nano-silica fume and (sub-) micro-silica fume should not exceed 1%, the loss on ignition should not exceed 3%, the chloride ion content should not exceed 0.01%, and the pozzolanic activity index should not exceed 1%. Should be greater than 95%. Among them, the specific surface area of 30nm nano silicon powder should not be less than 40000m ² /kg, ^and the silicon content should not be less than 99.9%; %.

The fly ash is high-quality Class I extra-fine fly ash produced by a power plant with advanced coal-fired technology. Its quality should not be lower than the national standard "Fly Ash Used in Cement and Concrete" GB/T1596-2005 and other relevant standards, its loss on ignition should not be greater than 3%, and the content of SO ₃ should not be greater than 2% , the water content should not be greater than 1%, the water demand ratio should not be greater than 95%, the specific surface area should be greater than 700m ² /kg; and its fineness (0.045mm square hole sieve residue, %) should not be greater than 10%.

The stimulator is independently developed by the inventor's research team. After studying the hydration reaction characteristics of ultrafine pulverized coal ash and realizing that its activity needs to be further stimulated and utilized, 55-60% The sodium metasilicate (na ₂ stO3·9H ₂ O), 38-43% slaked lime (Ca(OH) ₂ ) and 1.5-2.5% manganese sulfate (MnSO ₄ ·H ₂ O) are formulated according to mass percentage a chemical stimulant. The activator has good compatibility with early-strength ordinary Portland cement and polycarboxylate concrete superplasticizer.

The mixing water is tap water, the quality of which should not be lower than the requirements of relevant standards such as the Ministry of Construction Standard "Concrete Water Standard" JGJ63-2006, and the alkali content of the selected tap water should not exceed 1000mg/L.

The present invention also provides the preparation method for the concrete of steel-concrete composite structure C170 strength grade, and this method adopts the improved concrete mixing process of cement-wrapped sand-stone method, and concrete process steps are as follows:

1) First, mix 16kg/ ^m3 of concrete superplasticizer and 6kg/ ^m3 of activator into the weighed water 96kg/ ^m3 to obtain the mixture;

2) Then add 816kg/ ^m3 fine aggregate and 1/3 of the total amount of the mixture in step 1) into the forced mixer according to the weight ratio, and stir evenly for 1-2 minutes;

3) Then add 1094kg/m ³ Φ5～Φ10 continuous size gravel coarse aggregate and 1/3 of the total amount of the mixture in step 1), and stir evenly for 2~4min;

4) Then add all the cementing materials: 465kg/ ^m3 of cement, 42kg/ ^m3 of nano-silica fume, 28kg/ ^m3 of submicron silica fume and 115kg/ ^m3 of fly ash, and stir evenly for 2 to 3 minutes;

5) Finally, add 1kg/m ³ defoamer and the mixture of the remaining step 1), stir evenly for 2-3 minutes, stay for 3 minutes, then stir for 2-3 minutes until uniform, and then discharge to obtain a concrete mixture with C170 strength grade .

The beneficial effects of the present invention are:

1. The concrete produced by the present invention is a kind of ultra-high-strength high-performance concrete that is suitable for the steel-concrete composite structure strength grade of C170. The concrete can significantly improve the relationship between the concrete and the section steel on the basis of ensuring its required mechanical properties (ie, C170 strength, plasticity and other indicators) and high durability, high workability, high volume stability and economy. The natural bonding performance between them makes it unnecessary to add shear connectors on the surface of the steel when it is used in the design of steel concrete structures (or only a little according to the structural requirements), so as to ensure the effective cooperation between the steel and the concrete, so that It reduces the construction process, saves steel, improves construction efficiency, and avoids setting a large number of shear connectors on the surface of the steel section and easily causing defects such as congenital micro-cracks inside the concrete. It has significant economic benefits and construction quality improvement effects. The results of the mechanical properties comparison test are shown in Table 2.

2. The high-efficiency water-reducing agent used in the present invention is selected from polycarboxylate concrete superplasticizer (the water-reducing rate should be greater than 30%). It has good capacity and does not contain Na ₂ SO ₄ , which can further improve the durability of the concrete.

3. The defoamer used in the present invention is a powder defoamer, the model is AGITANP803, which can defoam a large amount of microbubbles that are formed during the concrete mixing process and remain in the concrete after vibration and compaction, so that the compactness is effective Improve and enhance the durability and shear stability of concrete.

4. The activator used in the present invention is the self-developed alkaline activator (XJFAA), which can make the concrete mixed with fly ash have a certain micro-expansion and improve the shrinkage performance of concrete; it can enhance the hydration process of fly ash The corrosion of the three-dimensional structure glass body with aluminosilicate as the main hydration component stimulates the potential activity of fly ash, improves the power of positive hydration reaction, and generates more C-S-H gel and calcium aluminate hydrate. And crystals such as calcium silicate hydrate, which can significantly improve the strength and corrosion resistance of the prepared concrete.

5. The nano-silicon powder used in the present invention is a non-toxic, tasteless, pollution-free, high-purity, impurity-free nano-material. The particle size of nano-silica powder is small and the specific surface area is large, which can give full play to its micro-filling effect; there are a large number of unsaturated residual bonds and hydrogen groups in different bonding states on the surface of nano-silicon powder, or it is silicon that deviates from a stable state due to lack of oxygen. Oxygen structure can consume and refine Ca(OH) ₂ crystals, promote hydration speed and degree of hydration, and make the formed calcium silicate hydrate gel more compact; compared with (sub) microsilica fume, it has higher The activity (especially the induced activity) and the free energy state of the concrete can greatly promote the improvement of the microstructure of the concrete and the improvement of the mechanical properties (ie, the C170 strength, plasticity and other indicators).

6. The ultra-high-strength high-performance concrete that is used for the steel-concrete composite structure strength grade that the present invention produces is C170 under the ordinary concrete production process condition, and adopts as far as possible to reduce cement particle and superfine active mineral particle to fly everywhere when concrete mixing The material feeding method of the cement-wrapped sand mixing process is realized, the preparation process is simple and easy to realize, it is suitable for engineering and industrialization, it is convenient for large-scale popularization and application, and it has good social benefits.

7. The raw material used for the ultra-high-strength high-performance concrete of C170 for the steel-concrete composite structure produced by the present invention contains a large amount of fly ash and silica fume, which are industrial waste and waste, and their consumption can protect the environment Making a great contribution and meeting the requirements of sustainable development, it is a kind of green concrete, an environmentally friendly material.

8. The raw materials (including industrial waste) selected in the present invention are mass-produced market circulation, traded products, and the raw materials are easy to get.

9. The ultra-high-strength high-performance concrete used in the steel-concrete composite structure produced by the present invention with a strength grade of C170 is mixed with ultra-fine active minerals (ultra-fine fly ash and ultra-fine silicon powder) by adding active minerals Pozzolanic reaction, reinforcement effect, filling effect, durability improvement effect and temperature peak reduction effect of ultra-high-strength high-performance concrete hydration heat, and make full use of active mineral admixtures and active mineral admixtures and high-efficiency reduction The super-superposition effect produced by the composite admixture of the water agent optimizes the particle gradation of the cementitious material part of the ultra-high-strength high-performance concrete material according to the characteristics that they are not at the same level as the cement particles and the coarse and fine aggregate particle sizes. In high-strength high-performance concrete, the interface structure between the aggregate and the cement stone and the pore structure of the cement stone have been greatly improved, and the density and impermeability of the cement stone have been improved. At the same time, the typical dense structure can be extended to the surface of the aggregate. , so that the ultra-high-strength high-performance concrete is more dense and hard, and the mechanical properties (especially the bonding performance with the steel), durability and workability of the ultra-high-strength high-performance concrete are greatly improved.

Detailed ways

The present invention significantly improves the bonding performance between steel and concrete in the natural state (that is, no shear connectors are provided on the surface of the steel or only a small amount of shear connectors are provided according to the structural requirements), and the respective mechanical properties of steel and concrete are effectively exerted. With the purpose of improving the bearing capacity and performance of structural components and improving the durability of the structure, the preparation technology of ultra-high-strength high-performance concrete with a strength grade of C170 for steel-concrete composite structures is studied. At present, the quality and strength of ordinary Portland cement used in the production of ultra-high-strength high-performance concrete at home and abroad are getting higher and higher, and the processing technology and quality of active mineral admixtures (silica fume, fly ash, etc.) used are continuously improved. The research and application of concrete admixtures such as superplasticizers have made great progress, and the research and application of defoamers and activators in concrete are also gradually developing, thus identifying the basis for the realization of the above research purposes. . At the same time, the amount of cement required for the preparation of ultra-high-strength high-performance concrete is relatively small, and the production of cement means a large amount of carbon dioxide emissions, so to a certain extent, it reduces the greenhouse effect on the earth; it requires a sufficient amount and accounts for cementing materials. High-quality active mineral admixtures such as fly ash and silica fume with a large proportion mean that the rational disposal and utilization of industrial waste will help form a good production cycle and environmental protection, and these high-quality active mineral admixtures are exactly the improvement The performance of the concrete material itself is required. In short, the application of ultra-high-strength high-performance concrete can save cement, turn industrial waste into treasure, prolong the service life of structural engineering, and ultimately protect the ecological environment and natural resources. In summary, the research and development of ultra-high-strength and high-performance concrete for steel-concrete composite structures will lead to a sustainable development path for better use of concrete, which will improve the comprehensive ability and performance of structural engineering and promote the development of steel structures. - Concrete composite structures are popularized and applied in China, especially high-rise and super high-rise buildings, offshore platforms or underwater structures, underground buildings, large-span and heavy-duty structures in high-intensity and earthquake-prone areas, to improve infrastructure and buildings in the living environment The scientific and technological content of the structure, and give full play to its unique advantages such as large bearing capacity and rigidity, good seismic performance, fast construction progress, good durability and fire resistance, and significant social and economic benefits. Therefore, the steel ultra-high-strength high-performance concrete composite structure has high engineering application value and broad market prospects.

The ultra-high-strength high-performance concrete developed by the present invention for the strength grade of steel-concrete composite structures is C170. In addition to using similar materials to ordinary concrete-cement, sand, gravel, water, it has also added its indispensable components: Concrete superplasticizers and active mineral admixtures (silica fume, fly ash), in addition to powdered defoamers and activators. Ultra-high-strength high-performance concrete is different from ordinary concrete, and its strength and performance are greatly improved compared with ordinary and high-strength concrete. The water-cement ratio of ultra-high-strength high-performance concrete is generally less than 0.24, while that of ordinary and high-strength concrete is generally above 0.30. The maximum particle size of coarse aggregate of ultra-high-strength high-performance concrete is also smaller than that of ordinary and high-strength concrete. The above-mentioned differences have led to a great difference in performance between ultra-high-strength high-performance concrete and ordinary and high-strength concrete. By adding ultra-fine active minerals, the pozzolanic reaction and (micro) filling effect of ultra-fine active minerals are used and plasticizing effect, optimizing the particle gradation of the cementitious material in ultra-high-strength high-performance concrete materials not only greatly improves the interface structure between aggregates and cement stones in ultra-high-strength high-performance concrete materials, but also the pore structure of cement stones. Improve the density and impermeability of cement stone, and at the same time, the typical dense structure can be extended to the surface of the aggregate, so that the ultra-high-strength high-performance concrete is more dense and hard, and the mechanical properties of ultra-high-strength high-performance concrete (especially with steel Bonding properties between) and durability have been greatly improved. At the same time, through the incorporation of powder defoamer, it can reduce the large amount of air bubbles that are formed during the concrete mixing process and remain in the cement paste in the concrete or in the interface transition zone between the cement paste and aggregate after vibrating and compacting. Degassing effectively improves the compactness, and makes a significant contribution to the improvement of the mechanical properties (including the bonding properties with steel) and the durability of ultra-high-strength high-performance concrete. In addition, the addition of the activator can make the concrete have a certain micro-expansion and improve the shrinkage performance of the concrete; it can enhance the corrosion of the vitreous body with aluminosilicate as the main hydration component in the hydration process of fly ash, Increase the activity of fly ash, improve the power of positive hydration reaction, generate more crystals such as C-S-H gel, calcium aluminate hydrate and calcium silicate hydrate, which have a significant impact on the strength and corrosion resistance of the prepared concrete improvement.

Similar to the bonding between light round steel bars and concrete, the bonding force between steel and concrete is mainly composed of three parts: chemical bonding force, frictional resistance and mechanical bite force. Each component of the bond between steel and concrete is closely related to the performance of concrete.

The chemical bonding force is the chemical adhesion or adsorption force produced by the cement gel in the concrete on the steel surface, and its (shear resistance) limit value depends on the nature of the cement and the roughness of the steel surface. When pouring concrete, the cement paste generates surface tension on the surface of the steel. Under the action of the surface tension, the cement paste on the steel surface will form a self-balance; pouring concrete generally needs to be vibrated, and the vibrating force (disturbance) can be strengthened and Accelerate the penetration of cement paste into the oxide layer on the steel surface; during the curing process, the cement paste crystallizes, and the cement crystal hardens to form chemical bonding force. The chemical bonding force only exists in the original state of the steel concrete member, once the (local) bond slip occurs on the connecting surface, the cement crystal will be sheared and crushed, and the chemical bonding force will be lost. The main factors affecting the chemical bonding strength are concrete strength, surface roughness of section steel, pouring method and vibration degree of specimen, later curing and shrinkage of concrete, etc.

After the chemical bonding force is lost, due to the roughness of the steel surface and the change of the steel surface condition (the unevenness of the steel surface) caused by other reasons, it will bite together with the concrete crystal particles on the contact surface, thus forming a mechanical bite force . For the rolled I-beam and other section steel produced in the factory and post-processed, once the bond slip develops faster, the concrete crystal on the contact surface between the section steel and the concrete is crushed and integrated, and the mechanical bite force is basically lost at this time. The main factors affecting the mechanical bite force are the roughness and surface condition (corrosion degree, etc.) of the steel surface, the aggregate gradation of concrete, the strength of concrete, and the stress mode of steel concrete members.

The frictional resistance of the concrete around the shaped steel to the shaped steel is also formed after the adhesion between the shaped steel and the concrete is broken, and it mainly comes into play after the mechanical occlusal force is basically lost. When the chemical bonding force, especially the mechanical occlusal force, is lost, due to the shearing, crushing and expansion of the concrete crystal on the contact surface with the section steel, coupled with the lateral constraints such as the protective layer and stirrups, it will be formed on the connection surface between the section steel and the concrete. The positive pressure, together with the large friction coefficient on the connecting surface, creates frictional resistance. Frictional resistance exists after the loss of chemical cementation, and is the main part of the late bond between steel and concrete. Factors that affect frictional resistance include the form of steel and its surface characteristics, the size of the bonding surface between steel and concrete, the way members are stressed, the gradation of concrete aggregates, and factors that affect lateral constraints (the thickness of the concrete cover of the steel , hoop ratio, concrete shrinkage), etc.

The key technical problem to be solved by the present invention is, on the basis of ensuring the mechanical properties (i.e. strength and plasticity) and high durability, high workability, high volume stability and economy of ultra-high-strength high-performance concrete, Significantly improve the (natural) bonding performance between concrete and section steel, so that in the design of section steel concrete structure, there is no need (or only a little according to the structural requirements) to add shear connectors on the surface of section steel, so that the section steel and concrete can be guaranteed. There is reliable bonding and anchoring between them, so that the two can work in harmony and work together under load.

From the principles of principle and design, the present invention breaks the limitation of the formula of "Bao Luomi", and considers the relationship between concrete superplasticizer, defoamer and activator and their relationship with cement through orthogonal test method and comparative test method. The compatibility of coarse aggregate, the influence of the maximum particle size of coarse aggregate, the gradation between different particle sizes of coarse aggregate and the particle size of fine aggregate on the strength and performance of concrete, and the (micro) filling effect of active mineral admixtures , volcanic ash activity and other performance factors, select high-quality coarse and fine aggregates and control the particle size and gradation, mix an appropriate amount of concrete superplasticizer and high-quality active mineral ultrafine powder into the ultra-high-strength high-performance concrete preparation materials, and consider defoaming The addition of additives and activators reduces the water-cement ratio. Based on the readily available local materials, the conventional production process is not changed. In order to minimize the flying of cement particles and ultra-fine active mineral particles in concrete mixing, cement-wrapped sand is used. The feeding method of the mixing process utilizes the pozzolanic reaction, enhancement effect, (micro) filling effect, durability improvement effect of the active mineral admixture and the temperature peak reduction effect of the hydration heat of ultra-high-strength high-performance concrete, and makes full use of the active mineral admixture The super-addition effect produced by the composite blending of the mixture and the composite mixture of the active mineral admixture and the high-efficiency water reducer, the defoaming effect of the defoamer and the active excitation of the activator, the mechanical properties (especially Bonding performance between steel and section steel), excellent work performance, good durability, relatively low cost, ultra-high-strength high-performance concrete with a strength grade of C170 suitable for reliable application in steel-concrete structures. The comparative results of the mechanical property test of the present invention are shown in Table 2.

等）均难以进入混凝土内部，并可减少碱-硅反应的发生几率和次氯酸钙的生成几率，其强度和耐久性能得到大幅度提高。即当水泥石结构和界面结构中大于0.1μm的大孔含量较低时，将有利于所配制超高强高性能混凝土的各项性能的改善,否则，对所配制超高强高性能混凝土的强度、抗渗性能、抗腐蚀性能和耐久性能均不利。When selecting raw materials in the present invention, not only the raw materials are required to be of high quality, but also the raw materials used to prepare the ultra-high-strength high-performance concrete are required to be readily available locally. In addition, considering the high strength of the prepared concrete, the particle gradation of the coarse and fine aggregate in the concrete material is optimized according to the theory of maximum compactness, so that the coarse and fine particles can be well filled with each other to reduce the void ratio of the aggregate; at the same time, The average particle size of general cement is 20-30 μm, and there are not many particles smaller than 10 μm, while the particle size of active mineral admixtures is much smaller than that of cement particles, and the average particle size of ultra-fine fly ash is 3-6 μm , can fill the gaps between cement particles, the average particle size of silica fume is also very small, 0.10-0.26μm, can fill the space between cement particles and ultrafine fly ash particles and between ultrafine fly ash particles The average particle size of nano-silica fume is smaller, ranging from 10nm to 0.1μm, which can fill the tiny gaps or gaps between the gelled particles and the interface structure, so the prepared ultra-high-strength high-performance concrete material Optimizing the particle size distribution of the cementitious material fraction is also crucial. The corrosivity of external deterioration factors (such as sulfate and other factors) to concrete largely depends on the void structure of concrete, which is the main reason for the durability of concrete. The incorporation of active mineral admixtures reduces the porosity between cement particles and the interface, makes the cement stone structure and interface structure more compact, and blocks the possible penetration pathways, so that the prepared ultra-high-strength and high-performance The impermeability of concrete is greatly improved, and water and other erosive media

etc.) are difficult to enter the interior of the concrete, and can reduce the occurrence probability of alkali-silicon reaction and the generation probability of calcium hypochlorite, and its strength and durability are greatly improved. That is, when the content of macropores larger than 0.1 μm in the cement stone structure and interface structure is low, it will be beneficial to the improvement of various properties of the prepared ultra-high-strength high-performance concrete. Otherwise, it will affect the strength, The impermeability, corrosion resistance and durability are all unfavorable.

After replacing part of the cement with the active mineral admixture, part of the moisture in the voids of the cement particles can be replaced by the mineral admixture filled in it, which can increase the fluidity of the cement slurry. But not all mineral admixtures have such a significant plasticizing effect, mainly due to the large specific surface area of some active mineral admixtures or their own porous structure, although they can replace cement after replacing cement. Part of the water in the cement paste, but because it absorbs water or needs more free water to wet the surface, the fluidity of the cement paste does not increase. In order to ensure the high working performance of the developed ultra-high-strength high-performance concrete, the present invention adopts the method of composite mixing of concrete superplasticizer and active mineral admixture, and under the cooperative work of the two, the fine particles of active mineral admixture not only Give full play to their (micro) filling effect, and replace the water filled in the gaps, so that the interval water layer between the particles is thickened; in addition, the fine particles of the active mineral admixture absorb the superplasticization of the concrete Agent molecules, the electrostatic repulsion generated by the electric double layer potential formed on the surface is greater than the gravitational force between powder particles, which promotes the dispersion of powder particles and further intensifies the dispersion of cement particles, increasing the fluidity of cement slurry, thus effectively The fluidity of the mixture is greatly improved; at the same time, the compound incorporation of ultrafine active mineral admixtures reduces the heat of hydration and improves the volume stability of concrete.

The aggregate used in the raw materials for the preparation of ultra-high-strength high-performance concrete should have high inherent strength, toughness and stability, so as to be able to resist various static and dynamic stresses, impacts and abrasions without causing the prepared concrete performance degradation. Due to the different surface states of different aggregates, the bonding strength between cement paste and aggregates is also different. Generally, gravel has higher bonding strength than pebbles; on the other hand, silicon in cement paste When the proportion of powder content is different, the bonding strength is also very different. When silicon powder is mixed, the bonding strength between cement paste and aggregate is much higher than when it is not mixed. When ordinary concrete is damaged, the bonding interface between cement paste and aggregate is a weak link, and cracks appear along the interface between cement paste and aggregate. Generally, the aggregate will not be damaged, and external erosion often occurs from this interface. began to develop, and the bonding interface between cement paste and aggregate in ultra-high-strength high-performance concrete is no longer a weak link, and its failure no longer occurs along the interface, but is caused by the destruction of aggregate, so The performance of the aggregate has a great influence on the performance of ultra-high-strength high-performance concrete. The fine aggregate selected in the research of the present invention adopts medium-coarse river sand with smooth particles, hard texture, good gradation, and low mud content; the coarse aggregate is rough surface, excellent texture, and good gradation, such as granite and basalt. The maximum particle size of artificial gravel as the main component should be controlled at 10mm. In this way, the uniformity of the concrete is further improved, so that the concrete is denser and the strength can be further improved.

The present invention adopts the cement-wrapped sandstone method (also known as the improved SEC method) concrete mixing process during preparation, and stirs in a forced mixer. The feeding sequence is: first, polycarboxylate concrete superplasticizer and activator Stir evenly into the weighed water to obtain a mixture; then add fine aggregate and 1/3 of the total amount of the mixture mixed with superplasticizer and activator → stir evenly (1 to 2 minutes) → add coarse aggregate and mix 1/3 of the total amount of superplasticizer and activator mixture → Stir well (2-4 minutes) → Add all cementing materials (cement, silica fume and fly ash) → Stir well (2-3 minutes) → Add The defoamer and the rest are mixed with superplasticizer and activator mixture → stir evenly (2-3 minutes) → rest for 3 minutes and then stir until uniform (2-3 minutes) → discharge. This process can minimize the flying of cement particles and ultrafine active mineral particles when the concrete is mixed, and can improve the strength of the prepared concrete, and the prepared concrete is not suitable for segregation, less bleeding, and relatively good working performance.

Example:

(1) Raw materials

1. Cement

Select Qinling brand P·O62.5R cement with stable quality and good performance, and conduct an adaptability test with polycarboxylate concrete superplasticizer before use. The test method adopts the current building materials industry standard "Cement and Reducer Water agent compatibility test method "JC/T1083-2008 method, good compatibility with polycarboxylate concrete superplasticizer. The performance indicators of the selected cement meet the requirements of the relevant current national standards, and its alkali content is low, its heat of hydration is low, and its water demand is also low.

2. Aggregate

The fine aggregate adopts medium-to-coarse and Bahe sand with smooth particles, hard texture, and good gradation. The quality of the sand conforms to the current building material industry standard "Sand and Stone Quality and Inspection Method Standard for Ordinary Concrete" JC/T52-2006 and the national standard. The high-quality sand standard stipulated in the standard "Sand for Construction" GB/T14684-2001. The fineness modulus is 3.0, the mud content and mud block content are controlled below 0.4% (by mass), and the chloride ion content is controlled below 0.05% (by dry sand mass).

Coarse aggregate is dense and hard, with high strength, rough surface, approximately spherical particle shape, small needle and flake content, and well-graded artificial crushed stone. The main components of granite and basalt (by mass) are not less than 90%. The quality of crushed stone meets the current building materials industry standard "Sand and Stone Quality and Inspection Method Standard for Ordinary Concrete" JC/T52-2006 and other relevant standards. The cubic compressive strength of the aggregate parent rock is 150-250MPa. The maximum particle size is controlled at 10mm, the mud content is controlled below 0.2% (by mass), the mud block content is controlled below 0.1% (by mass), and the content of needle and flake particles is controlled below 0.5% (by mass) below, and must not be mixed with weathered particles. When preparing the concrete, the continuous particle size gravel Φ5～Φ10 is used for feeding.

3. Fly ash

High-quality Class I extra-fine fly ash produced by a power plant with advanced coal-fired technology. Its quality meets the requirements of the national standard "Fly Ash Used in Cement and Concrete" GB/T1596-2005 and other relevant standards. The water content is 2.2%, the SO ₃ content is 1.5%, the water demand ratio is less than 95%, and the specific surface area is about 1000m ² /kg.

4. Silicon fume

The quality of the selected 30nm nano-silica fume and (sub-)micro-silica fume meets the requirements of the national standard "Mineral Admixtures for High-Strength and High-performance Concrete" GB/T18736-2002 and other relevant standards. The 30nm nano-silica fume and (sub-)micro-silica The moisture content of the flour is less than 1%, the loss on ignition is less than 3%, the chloride ion content is less than 0.01%, and the pozzolanic activity index is greater than 95%. Among them, the specific surface area of 30nm nano silicon powder is about 42000m ² /kg, and the silicon content is not less than 99.9%; the specific surface area of (sub)micron silicon powder is about 27000m ² /kg, and the silicon dioxide content is not less than 99%.

5. Concrete superplasticizer

After a lot of tentative comparison tests and compatibility tests with cement, the high-efficiency water reducer selected in this invention is a polycarboxylate concrete superplasticizer, and its quality should not be lower than the current national standard "Concrete Admixture" GB8076- 2008 and other relevant standards require that the water reducing rate of the selected high-efficiency water reducing agent should be greater than 30%. The maximum saturated content of the selected high-efficiency water reducer is not less than 2.5% of the total amount of cementitious materials. The same mixing method is adopted, and a compatibility test with the selected cement variety is required before use.

6. Stimulator

The fly ash potential activity activator (XJFAA) independently developed by the research team of the inventor according to the hydration reaction characteristics of ultra-finely ground fly ash and further stimulating and utilizing its activity is selected, that is, 55-60% sodium metasilicate ( Na ₂ StO ₃ 9H ₂ O), 38-43% slaked lime (Ca(OH) ₂ ) and 1.5-2.5% manganese sulfate (Na ₂ St0 ₃ 9H ₂ O) prepared according to mass percentage For chemical stimulants, see Table 1 for details. The activator has good compatibility with early-strength ordinary Portland cement and polycarboxylate concrete superplasticizer.

Different proportions of table 1XJFAA stimulator

7. Mix water

Tap water is selected as the mixing water, and its quality meets the requirements of the Ministry of Construction's standard "Concrete Mixing Water Standard" JGJ63-2006 and other relevant standards, and the alkali content is less than 800mg/L.

(2) Mixing ratio

Table 2 shows the matching ratio provided by the present invention for the ultra-high-strength high-performance concrete with a strength grade of C170 that will be applied in steel-concrete structures.

Table 2 Mix ratio of ultra-high-strength and high-performance concrete for steel-concrete composite structures (unit: k _g /m3)

(3) Mixing process

The invention adopts the cement-wrapped sand-stone method concrete mixing process, and the specific process steps are as follows:

First, mix 16kg/ ^m3 of polycarboxylate concrete superplasticizer and 6kg/ ^m3 of activator into weighed water 96kg/ ^m3 to obtain the mixture; Add 816kg/ ^m3 of fine aggregate and 1/3 of the total amount of the mixture mixed with superplasticizer and activator, and stir evenly for 1 to 2 minutes; then add 1094kg/ ^m3 of coarse aggregate (Φ5~Φ10 continuous Gravel grade crushed stone) and 1/3 of the total amount of the mixture mixed with superplasticizer and activator, after stirring evenly for 2 to 4 minutes; then add all the cementing materials: 465kg/m ³ of cement, 42kg/m ³ of nano Silica fume, 28kg/ ^m3 (sub) microsilica fume and 115kg/ ^m3 fly ash, after stirring evenly for 2 to 3 minutes, add 1kg/ ^m3 AGITANP803 powder defoamer and the rest mixed with superplasticizer Stir the mixture of agent and activator uniformly for 2 to 3 minutes; stay for 3 minutes and then stir for 2 to 3 minutes until uniform, and then discharge to obtain a concrete mixture with C170 strength level.

This process can minimize the flying of cement particles and ultrafine active mineral particles when the concrete is mixed, and can improve the strength of the prepared concrete, and the prepared concrete is not suitable for segregation, less bleeding, and relatively good working performance. (4) Comparison of mechanical performance test results

Table 2 shows the mechanical performance comparison test results of ultra-high-strength high-performance concrete with a strength grade of C170 suitable for steel-concrete composite structures prepared according to the above mix ratio and general ultra-high-strength concrete (concrete with a strength grade of C170).

Table 3 Concrete mechanical properties comparison test results

It can be seen from Table 3 that the ultra-high-strength high-performance concrete with a strength grade of C170 prepared by this technology has achieved the mechanical properties it should possess (ie, C170 strength, plasticity, etc.) and has high durability, On the basis of high reliability, high workability, high volume stability and economy, it can significantly improve the (natural) bonding performance between concrete and steel, so that it is not necessary (or only according to the structural requirements) in the design of steel concrete structures Slightly) adding shear connectors on the surface of the steel can ensure the effective cooperation between the steel and the concrete, thereby reducing the construction process, saving steel, improving construction efficiency, and avoiding a large number of shear connections on the surface of the steel It is easy to cause defects such as congenital micro-cracks inside the concrete, which can bring significant economic benefits and construction quality improvement effects, and has high engineering application value and broad market prospects.

Claims (10)

1. for a concrete for reinforced concrete composite structure C170 strength grade, it is characterized in that, this concrete is according to kg/m ³proportioning be:

Cement: fine aggregate: coarse aggregate: water: Concrete superplastizer: defoamer: silica flour: flyash: exciting agent=465: 816: 1094: 96: 16: 1: 70: 115: 6.

2. a kind of concrete for reinforced concrete composite structure C170 strength grade according to claim 1, is characterized in that, described cement is selected 625R ordinary Portland cement.

3. a kind of concrete for reinforced concrete composite structure C170 strength grade according to claim 1, is characterized in that, described fine aggregate adopt that fineness modulus is that particle between 2.8～3.2 is round and smooth, quality is hard, grating is good in partially thick river sand; By quality ratio, its silt content and clod content should be not more than 0.4%; In the mass ratio of dry sand, its chloride ion content should be not more than 0.05%.

4. a kind of concrete for reinforced concrete composite structure C170 strength grade according to claim 1, it is characterized in that, described coarse aggregate adopts that quality densification is hard, intensity is high, surface irregularity, particle shape are almost spherical, elongated particles is little, grating is good take the artificial rubble that grouan, basalt is main component, according to continuous size fraction rubble Φ 5～Φ 10, feeds intake; The cubic compressive strength of its parent rock of coarse aggregate should be not less than 140MP, and maximum particle diameter should be controlled at 10mm; By quality ratio, its silt content should be not more than 0.2%, and clod content should be not more than 0.1%, and pin, platy shaped particle content should be not more than 0.5%, and must not sneak into weathering particle.

5. a kind of concrete for reinforced concrete composite structure C170 strength grade according to claim 1, it is characterized in that, described Concrete superplastizer is selected poly carboxylic acid series concrete superplasticizer, water-reducing rate should be greater than 30%, and maximum saturation volume should be not less than 2.5% of whole binder total amounts.

6. the concrete that is C170 for reinforced concrete composite structure strength grade according to claim 1, is characterized in that, described defoamer is selected AGITAN@P803 powder defoamer.

7. the concrete that is C170 for reinforced concrete composite structure strength grade according to claim 1, it is characterized in that, described silica flour adopts 30nm nano silica fume and the sub-micro silica flour that mass ratio is 3:2, the water ratio of 30nm nano silica fume and sub-micro silica flour all should be not more than 1%, loss on ignition all should be not more than 3%, chloride ion content all should be not more than 0.01%, and pozzolanic activity index all should be greater than 95%; Wherein, the specific surface area of 30nm nano silica fume should be not less than 40000m ²/ kg, silicone content should be not less than 99.9%; The specific surface area of submicron silica flour should be not less than 25000m ²/ kg, dioxide-containing silica should be not less than 95%.

8. the concrete that is C170 for reinforced concrete composite structure strength grade according to claim 1, is characterized in that, described flyash adopts the special fine powdered coal of high-quality I level, and its loss on ignition should be not more than 3%, SO ₃content should be not more than 2%, and water content should be not more than 1%, and water demand ratio should be not more than 95%, and specific surface area should be greater than 700m ²/ kg; In 0.045mm square hole sieve, tail over, its fineness should be not more than 10%.

9. the concrete that is C170 for reinforced concrete composite structure strength grade according to claim 1, is characterized in that, described exciting agent is selected self-control flyash excitant XJFAJ, by the raw material of following mass ratio, is prepared from:

Starso 55～60%, white lime 38～43%, manganous sulfate 1.5～2.5%.

10. for the concrete preparation method of reinforced concrete composite structure C170 strength grade, it is characterized in that, the method adopts improved cement to wrap up in sandstone method concrete stirring technology, and concrete technology step is as follows:

1) first by Concrete superplastizer 16kg/m ³with exciting agent 6kg/m ³evenly admix load weighted water 96kg/m ³in, obtain mixture;

2) then according to weight proportion, in forced mixer, add 816kg/m ³fine aggregate and step 1) amount of the mixture 1/3, uniform stirring 1～2min;

3) add again 1094kg/m ³Φ 5～Φ 10 continuous size fraction rubble coarse aggregates and step 1) amount of the mixture 1/3, uniform stirring 2～4min;

4) then add whole consolidating materials: 465kg/m ³cement, 42kg/m ³nano silica fume, 28kg/m ³sub-micro silica flour and 115kg/m ³flyash, uniform stirring 2～3min;

5) finally add 1kg/m ³defoamer and remaining step 1) mixture, uniform stirring 2～3min, stops and after 3 minutes, stirs 2～3min to evenly again, discharging obtains the concrete mix of C170 strength grade.