CN112194404A - Low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension - Google Patents
Low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension Download PDFInfo
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- C—CHEMISTRY; METALLURGY
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- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
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- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
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- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
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Abstract
The invention discloses a low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension. The compound additive comprises anhydrous calcium sulphoaluminate clinker, calcium sulfate, silica fume, lithium carbonate, styrene polymers, triisopropanolamine, an anti-settling agent and the like, is used for concrete taking ordinary portland cement as a cementing material, provides ettringite crystals through hydration reaction of the anhydrous calcium sulphoaluminate and the calcium sulfate, accelerates the formation speed of the ettringite in a hydration product by utilizing the crystal seed effect of the silica fume and the early strength effect of the lithium carbonate and the triisopropanolamine, achieves the aims of micro-expansion, early strength, low shrinkage and low creep, simultaneously improves the workability of the concrete by the anti-settling agent, and improves the later strength of the silica fume through volcanic ash reaction; the concrete added with the composite additive has the characteristics of early strength, micro-expansion and low creep, is suitable for the early-age prestressed tensioning engineering of the concrete, saves time and shortens the construction period.
Description
Technical Field
The invention relates to a building concrete functional additive material, in particular to a low-shrinkage low-creep concrete composite additive suitable for early-age prestress tensioning, and belongs to the technical field of new building materials.
Background
In the engineering application of post-tensioned prestressed concrete structures, the problem that prestressed concrete cracks before and after tensioning is often encountered. When the concrete structure is operated with cracks, the durability of the engineering structure and the structural performance are affected by the cracks. Therefore, the occurrence of cracks is a particular concern both during the construction process and during the use phase. Crack control is quite critical for prestressed concrete structures, and although cracks created before tensioning may close after tensioning, the creation of cracks before tensioning always has a detrimental effect on the structural properties. In bulk concrete applications, creep in the bulk concrete itself is likely to be the cause of cracking, since the development of heat of hydration and subsequent cooling subjects the already confined bulk concrete to temperature cycling. The rapid rise in temperature within the mass of concrete causes compressive stresses within the concrete which are small due to the small modulus of elasticity of the freshly poured concrete, so that creep is greater at this point, thereby allowing the compressive stresses to relax, so that once cooling occurs the compressive stresses being maintained will gradually disappear, but if the concrete is clandeered further, tensile stresses will develop, possibly resulting in cracks. The creep has a negative effect on most of the performance of the concrete structure, and for some projects with early prestress tensioning requirements, the concrete has low early strength, small elastic modulus, large shrinkage and large creep, and the cracking phenomenon is easy to occur after tensioning, so that the durability of the concrete is affected. Therefore, in order to realize the application of the concrete to early-age prestress tensioning, the development of the early-strength, low-shrinkage and low-creep concrete is very significant by improving the construction performance, the early-strength performance, the crack resistance and the durability of the concrete.
Disclosure of Invention
Aiming at the defects of complex stress, easy cracking, water seepage and the like of a prestressed tensioning concrete structure in the prior art, the invention aims to provide the low-shrinkage low-creep concrete composite additive suitable for early-age prestressed tensioning, and the concrete added with the composite additive can improve the bonding performance of the joint surfaces of new and old concrete, reduce the cracking risk of the interface of the new and old concrete and improve the cracking resistance of the concrete; the early strength of the concrete is improved by promoting the formation of a large amount of ettringite crystals in the early hydration process of the cement, the shrinkage of the concrete is compensated, the creep shrinkage of the concrete is reduced, the problem of large creep during early tensioning of the concrete is solved, and the quality and the durability of the bridge are greatly improved.
In order to achieve the technical purpose, the invention provides a low-shrinkage low-creep concrete composite additive suitable for early-age prestress tensioning, which comprises the following components in percentage by mass: 60-80 parts of anhydrous calcium sulphoaluminate clinker, 5-20 parts of calcium sulfate, 10-20 parts of silica fume, 1-5 parts of lithium carbonate, 1-3 parts of triisopropanolamine, 0.05-0.2 part of anti-settling agent and 3-5 parts of styrene polymer; the anti-settling agent consists of D-glucose and D-galactose.
The anhydrous calcium sulphoaluminate and calcium sulfate components in the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension mainly generate ettringite through hydration reaction, the crystal seed effect of silica fume and the early strength effect of lithium carbonate and triisopropanolamine synergistically accelerate the forming speed of the ettringite in a hydration product, and the mass formation of the early ettringite in the concrete is promoted, so that the early strength can be realized, the proportion of the ettringite crystals in the hydration product can be increased, the aim of micro-expansion can be fulfilled, particularly, the proportion in the hydration product in the early age is high, the early strength and the elastic modulus are improved, and the aims of micro-expansion, early strength, low shrinkage and low creep are fulfilled; the styrene polymer is added to fill pores and micro cracks in the cement concrete, so that the compactness of the cement concrete can be improved, the bonding force between cement stones and aggregates is enhanced, the stress concentration at the tip of the crack is relieved, the original performance of the common cement concrete is changed, the common cement concrete has the remarkable advantages of high strength, high adhesion, impermeability, frost resistance, impact resistance, wear resistance, chemical corrosion resistance and the like, and the special anti-settling agent can be used for enhancing the anti-settling capacity and water loss resistance of the concrete, so that the concrete has excellent workability.
The low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension has the comprehensive effects of improving the deformation performance of concrete and enhancing the interface bonding performance of the concrete, and realizes the prevention and treatment of crack of a joint interface. The method adopts an expansion means of promoting the crystallization of inorganic mineral ettringite to prepare the shrinkage-compensating concrete so as to achieve the aim of cracking resistance of the concrete; interface bonding of the new concrete and the old concrete is improved through a modification enhancing technology of the silica fume and the modified polymer on the interface of the new concrete and the old concrete, and interface cracking of the new concrete and the old concrete is avoided; the formation of a large amount of ettringite crystals is promoted in the early hydration process of the cement by lithium carbonate and triisopropanolamine, so that the early strength of the concrete is improved, and the problem of large tension creep of the concrete in the early stage is solved.
As a preferable scheme, the mass percentage of the anhydrous calcium sulphoaluminate in the anhydrous calcium sulphoaluminate clinker is 70-90%. Calcium sulphoaluminate is the main active ingredient of ettringite crystal generated by hydration reaction.
Preferably, the silica fume is non-encrypted silica fume, and the particle size is 0.1-0.3 μm. Preferably, the silica fume has a particle size of 0.1-0.2 μm and is of high quality without being encrypted. The main function of the silica fume is that the silica fume can play a role of seed crystal to promote the formation of ettringite in the early stage, the later-stage strength is improved through volcanic ash reaction in the later stage, and after the silica fume is used, the pore size in hydrated slurry is greatly reduced, the pore size distribution is improved, so that the strength is improved, and the permeability is reduced. Especially, the superfine silica fume with excellent quality is used, so that not only can the early hydration heat of the high-strength concrete be reduced, but also the later strength of the concrete can be ensured.
As a preferred embodiment, the styrene-based polymer is an acrylate-styrene copolymer and/or a styrene-butadiene copolymer. More preferably, the styrenic polymer is a styrene-butadiene copolymer. The optimized styrene polymer can well fill pores and micro cracks in cement concrete, can improve the compactness of the cement concrete, enhance the binding force between cement stones and aggregates, relieve stress concentration at the tips of the cracks, and change the original performance of common cement concrete, so that the cement concrete has the remarkable advantages of high strength, high adhesion, impermeability, frost resistance, impact resistance, wear resistance, chemical corrosion resistance and the like.
As a preferable scheme, the anti-settling agent is prepared from D-glucose and D-galactose according to the mass percentage of 40% -60%: 40% -60%. The preferable anti-settling agent can enhance the anti-settling capacity and the anti-water loss performance of the concrete, so that the concrete has excellent workability.
As a preferable scheme, the specific surface area of the composite additive is 2000-2300 cm2(ii) in terms of/g. The specific surface area is too small, the hydration of active components in the composite additive is insufficient, the activity of the active components cannot be exerted, the specific surface area is too large, the activity of the active components cannot be improved, the grinding energy consumption can be wasted, the proper specific surface area can exert the corresponding activity, and the grinding energy consumption is lowest.
Compared with the prior art, the technical scheme of the invention has the beneficial effects.
1) The invention relates to a low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension, which mainly comprises anhydrous calcium sulphoaluminate clinker, calcium sulfate, silica fume, lithium carbonate, triisopropanolamine, an anti-settling agent, a styrene polymer and the like. The compound additive utilizes hydration reaction of anhydrous calcium sulphoaluminate and calcium sulfate as the source of ettringite, and the hydration reaction of the compound additive promotes the generation quantity of ettringite crystals in hydration products; meanwhile, by utilizing the crystal seed effect of the silica fume and the early strength effect of the lithium carbonate and the triisopropanolamine, the forming speed of the ettringite in a hydration product is accelerated, the mass formation of the early ettringite in the concrete is promoted, the early strength can be realized, the proportion of the ettringite crystals in the hydration product can be increased, the aim of micro-expansion can be fulfilled, particularly, the proportion in the early-age hydration product is high, the early strength and the elastic modulus are improved, the aims of micro-expansion, early strength, low shrinkage and low creep are fulfilled, the compactness of the cement concrete can be improved by adding the styrene polymer to fill pores and micro cracks in the cement concrete, the binding force between the cement stone and the aggregate is enhanced, the stress concentration at the tip of the cracks is relieved, the original performance of the common cement concrete is changed, and the cement concrete has the remarkable advantages of high strength, high adhesion, impermeability, frost resistance, impact resistance, abrasion resistance, chemical corrosion resistance and the like, the anti-settling agent can enhance the anti-settling capacity and the anti-water loss performance of the concrete, so that the concrete has excellent workability.
2) The low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension has the advantages that the silica fume is added, the silica fume in the concrete can play a role of crystal seeds at the early stage to promote formation of ettringite, the later-stage strength is improved through volcanic ash reaction, the silica fume is introduced, the pore size in hydrated slurry can be greatly reduced, the pore size distribution is improved, the strength is improved, and the permeability is reduced. However, although the early relative strength development of silica fume concrete is slower than that of pure cement concrete at the same water-cement ratio, the strength is greatly improved due to the addition of silica fume, and the absolute strength of silica fume concrete is higher than that of pure cement concrete. On the other hand, high strength concrete develops relatively fast early strength, whereas concrete incorporating silica fume may have a somewhat delayed setting time, and hydration after setting is greatly accelerated by the superplasticizer and silica fume, with the result that the strength develops very fast after setting. By using the superfine silica fume with excellent quality, the early hydration heat of the high-strength concrete can be reduced, and the later strength of the concrete is ensured; meanwhile, the slurry performance of the fresh concrete has good cohesiveness and water retention, and the concrete performance is improved.
Detailed Description
The following specific examples are intended to further illustrate the present disclosure, but the scope of the present disclosure is not limited to the following specific examples.
The following examples further illustrate the present disclosure by formulating a 3d prestressed, tensionable, C60 low shrinkage, low creep wet joint concrete with a low shrinkage, low creep concrete admixture suitable for early-age prestressed tensioning.
In the following examples, each raw material was a commercial raw material directly purchased, unless otherwise specified.
Example 1: the preparation method of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension comprises the following steps: 80 parts of anhydrous calcium sulfoaluminate clinker (the content of anhydrous calcium sulfoaluminate is 80 percent), 5 parts of calcium sulfate, 10 parts of silica fume (the particle size is 0.2 mu m), 1 part of lithium carbonate, 1 part of triisopropanolamine, 0.1 part of anti-settling agent (D-glucose: D-galactose = 4: 6) and 3 parts of styrene-butadiene copolymer (AXILAT PSB 150 of Hansen company in America), and the materials are mixed and ground into powder with the specific surface area of 2000cm2Powder per gram.
C60 preparation of low-shrinkage low-creep wet joint concrete: P.O 52.5 ordinary Portland cement 280kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m380kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm broken stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Example 2: the preparation method of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension comprises the following steps: 60 parts of anhydrous calcium sulfoaluminate clinker (the content of anhydrous calcium sulfoaluminate is 80 percent), 20 parts of calcium sulfate, 10 parts of silica fume (the particle size is 0.2 mu m), 2 parts of lithium carbonate, 3 parts of triisopropanolamine, 0.1 part of anti-settling agent (D-glucose: D-galactose = 6: 4) and 5 parts of styrene-butadiene copolymer (AXILAT PSB 150 of Hansen company, USA), mixing and grinding the mixture into powder with the specific surface area of 2000cm2Powder per gram.
C60 preparation of low-shrinkage low-creep wet joint concrete: P.O 52.5 ordinary Portland cement 280kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m380kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Example 3: the preparation method of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension comprises the following steps: 70 parts of anhydrous calcium sulfoaluminate clinker (the content of the anhydrous calcium sulfoaluminate is 70 percent), 10 parts of calcium sulfate, 12 parts of silica fume (the particle size is 0.1 mu m), 1 part of lithium carbonate, 2 parts of triisopropanolamine, 0.2 part of anti-settling agent (D-glucose: D-galactose = 4: 6) and 5 parts of styrene-butadiene copolymer (AXILAT PSB 150 of Hansen company in America), mixing and grinding the mixture into powder with the specific surface area of 2200cm2Powder per gram.
C60 preparation of low-shrinkage low-creep wet joint concrete: P.O 52.5 ordinary Portland cement 280kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m380kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Example 4: the preparation method of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension comprises the following steps: 60 parts of anhydrous calcium sulfoaluminate clinker (the content of the anhydrous calcium sulfoaluminate is 90%), 10 parts of calcium sulfate, 20 parts of silica fume (the particle size is 0.3 mu m), 5 parts of lithium carbonate, 1 part of triisopropanolamine, 0.2 part of anti-settling agent (D-glucose: D-galactose = 5: 5) and 4 parts of acrylate-styrene copolymer (Dehydro 7660 of ACQUOS), mixing, grinding into a specific surface area of 2300cm2Powder per gram.
C60 preparation of low-shrinkage low-creep wet joint concrete: P.O 52.5 ordinary Portland cement 280kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m380kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Comparative example 1: zone of this comparative example and example 1The difference is that the C60 concrete does not contain the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension, and the dosage of the composite additive is equivalently replaced by P.O 52.5 ordinary portland cement. Specifically, the method comprises the following steps: P.O 52.5 ordinary portland cement 360kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m30kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Comparative example 2: the comparative example differs from example 1 in that the low shrinkage low creep concrete composite additive suitable for early-age prestressing tension contains no silica fume. Specifically, the method comprises the following steps: the preparation method of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension comprises the following steps: 80 parts of anhydrous calcium sulphoaluminate clinker (the content of the anhydrous calcium sulphoaluminate is 80 percent), 5 parts of calcium sulfate, 0 part of siliceous dust, 1 part of lithium carbonate, 1 part of triisopropanolamine, 0.1 part of anti-settling agent (D-glucose: D-galactose = 4: 6) and 3 parts of styrene-butadiene copolymer (AXILAT PSB 150 of the American Hansen company), mixing and grinding the mixture into powder with the specific surface area of 2000cm2Powder per gram.
C60 preparation of low-shrinkage low-creep wet joint concrete: P.O 52.5 ordinary Portland cement 280kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m380kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Comparative example 3: this comparative example differs from example 1 in that the low shrinkage low creep concrete composite additive suitable for early-age prestressing tension contains no styrene-butadiene copolymer. Specifically, the method comprises the following steps: the preparation method of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension comprises the following steps: anhydrous calcium sulfoaluminate clinker (anhydrous calcium sulfoaluminate containing80%) 80 parts, 5 parts of calcium sulfate, 10 parts of silica fume (particle size of 0.2 μm), 1 part of lithium carbonate, 1 part of triisopropanolamine, an anti-settling agent (D-glucose: d-galactose = 4: 6) 0.1 part of styrene-butadiene copolymer and 0 part of styrene-butadiene copolymer, and grinding the mixture into powder with the specific surface area of 2000cm2Powder per gram.
C60 preparation of low-shrinkage low-creep wet joint concrete: P.O 52.5 ordinary Portland cement 280kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m380kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Comparative example 4: the comparative example differs from example 1 in that the low shrinkage low creep concrete composite additive suitable for early stage prestressing tension does not contain lithium carbonate. Specifically, the method comprises the following steps: the preparation method of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension comprises the following steps: 80 parts of anhydrous calcium sulfoaluminate clinker (the content of the anhydrous calcium sulfoaluminate is 80 percent), 5 parts of calcium sulfate, 10 parts of silica fume (the particle size is 0.2 mu m), 0 part of lithium carbonate, 1 part of triisopropanolamine, 0.1 part of anti-settling agent (D-glucose: D-galactose = 4: 6) and 3 parts of styrene-butadiene copolymer (AXILAT PSB 150 of Hansen company in America), and the materials are mixed and ground into powder with the specific surface area of 2000cm2Powder per gram.
C60 preparation of low-shrinkage low-creep wet joint concrete: P.O 52.5 ordinary Portland cement 280kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m380kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Comparative example 5: the comparative example differs from example 1 in that the C60 concrete does not contain a low shrinkage low creep concrete composite additive suitable for early-age prestressed tension, and the composite additive is replaced by a sodium sulfate early strength agent. Specifically, the method comprises the following steps:
P.O 52.5 ordinary Portland cement 350kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m310kg/m of sodium sulfate early strength agent3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
Comparative example 6: the comparative example differs from example 1 in that the low shrinkage low creep concrete composite additive suitable for early-age prestressing tension does not contain an anti-settling agent. Specifically, the method comprises the following steps: the preparation method of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension comprises the following steps: 79.5 parts of anhydrous calcium sulfoaluminate clinker (the content of the anhydrous calcium sulfoaluminate is 80 percent), 5 parts of calcium sulfate, 10 parts of silica fume (the particle size is 0.2 mu m), 1 part of lithium carbonate, 1 part of triisopropanolamine, 0 part of anti-settling agent and 3 parts of styrene-butadiene copolymer (AXILAT PSB 150 of Vast corporation in America), and the materials are mixed and ground into a powder with the specific surface area of 2000cm2Powder per gram.
C60 preparation of low-shrinkage low-creep wet joint concrete: P.O 52.5 ordinary Portland cement 280kg/m3Grade I fly ash 65 kg/m3S95 mineral powder 65 kg/m380kg/m of low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension3Medium sand 720kg/m3226kg/m of 4.75-9.5mm crushed stone3903kg/m of 9.5-20mm crushed stone32.2kg/m of slow-release type polycarboxylate superplasticizer3150kg/m of water3。
The test results of the performance of the 3d prestressed tension C60 low shrinkage low creep wet joint concrete examples and comparative examples are shown in Table 1:
TABLE 1C 60 test results of various properties of low shrinkage and creep wet joint concrete examples and comparative examples
The results show that the wet joint concrete of the examples 1, 2, 3 and 4 has very high early strength, the 3d compressive strength is more than 54MPa, the designed strength is more than 90 percent, the 3d prestressed tensioning requirement is met, a large amount of ettringite is mainly generated in the early stage, the early strength is improved, and the early strength is lower because the comparative example 1 has no low-shrinkage low-creep concrete composite additive suitable for early-age prestressed tensioning. The properties of examples 1, 2, 3 and 4 show that the concrete has a high early strength and a high modulus of elasticity, and therefore the creep strain at the late stage is small, while comparative example 1 has a low early strength and a low modulus of elasticity, and therefore the creep strain at the late stage is large. Comparative example 5 has high early strength and large elastic modulus, but has large creep strain due to the absence of the expansion component. The wet joint concrete is doped with the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension, so that the limited expansion rates of the concrete in 14 d-air in water and 28d in air are higher, while the limited expansion rates of the comparative examples 1 and 5 are lower, and the better expansion performance can compensate the shrinkage of the concrete, so that the concrete has good volume stability. Good volume stability and small post creep strain, and can greatly improve the cracking resistance of concrete.
Comparative examples 1, 5 and 6 show that the workability of concrete is poor and the construction is not facilitated because of the absence of the anti-settling agent. Comparative example 2 it can be seen that silica fume is very beneficial for improving the strength, bonding tensile strength and workability of concrete because silica fume is not present, the 3d and 28d strength of concrete is low, the bonding tensile strength is also low, and the workability of concrete is general. Comparative example 3 it can be seen that since the styrene-butadiene copolymer is not present, the bonding tensile strength is lower than that of example 1, so that the modified polymer is very beneficial in improving the bonding strength of the new and old concrete interfaces, and good bonding performance is very important in improving the cracking of the new and old concrete interfaces. Comparative example 4 it can be seen that the 3d strength of the concrete is lower due to the absence of lithium carbonate.
The reasonable proportioning components are necessary conditions for preparing high-performance concrete, and when the components of the low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension reach a scientific balance condition, the prepared concrete has excellent working performance and mechanical performance, the cracking problem of the concrete is well solved, and the durability of the concrete is improved.
Claims (6)
1. A low-shrinkage low-creep concrete composite additive suitable for early-age prestress tension is characterized in that: the adhesive comprises the following components in parts by mass:
60-80 parts of anhydrous calcium sulphoaluminate clinker,
5-20 parts of calcium sulfate,
10-20 parts of silica fume,
1-5 parts of lithium carbonate,
1-3 parts of triisopropanolamine,
0.05 to 0.2 part of anti-settling agent,
3-5 parts of styrene polymer; the anti-settling agent consists of D-glucose and D-galactose.
2. The low shrinkage low creep concrete composite additive suitable for early-age prestressed tension according to claim 1, wherein: the mass percentage content of the anhydrous calcium sulphoaluminate in the anhydrous calcium sulphoaluminate clinker is 70-90%.
3. The low shrinkage low creep concrete composite additive suitable for early-age prestressed tension according to claim 1, wherein: the silica fume is non-encrypted silica fume with the particle size of 0.1-0.3 mu m.
4. The low shrinkage low creep concrete composite additive suitable for early-age prestressed tension according to claim 1, wherein: the anti-settling agent is prepared from D-glucose and D-galactose according to the mass percentage of 40% -60%: 40% -60%.
5. The low shrinkage low creep concrete composite additive suitable for early-age prestressed tension according to claim 1, wherein: the styrene polymer is acrylate-styrene copolymer and/or styrene-butadiene copolymer.
6. The low shrinkage and creep concrete composite additive suitable for early-age prestress tensioning according to any one of claims 1 to 4, wherein: the specific surface area of the composite additive is 2000-2300 cm2/g。
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