CN116751015A - Physical and nano technology modified recycled concrete member and preparation method thereof - Google Patents
Physical and nano technology modified recycled concrete member and preparation method thereof Download PDFInfo
- Publication number
- CN116751015A CN116751015A CN202310835745.9A CN202310835745A CN116751015A CN 116751015 A CN116751015 A CN 116751015A CN 202310835745 A CN202310835745 A CN 202310835745A CN 116751015 A CN116751015 A CN 116751015A
- Authority
- CN
- China
- Prior art keywords
- recycled concrete
- recycled
- cement
- concrete
- calcium carbonate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000004567 concrete Substances 0.000 title claims abstract description 199
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 238000005516 engineering process Methods 0.000 title abstract description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 112
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims abstract description 88
- 239000004568 cement Substances 0.000 claims abstract description 59
- 239000002245 particle Substances 0.000 claims abstract description 51
- 229910000019 calcium carbonate Inorganic materials 0.000 claims abstract description 44
- 230000006835 compression Effects 0.000 claims abstract description 44
- 238000007906 compression Methods 0.000 claims abstract description 44
- 239000002086 nanomaterial Substances 0.000 claims abstract description 44
- 239000005543 nano-size silicon particle Substances 0.000 claims abstract description 39
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 39
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 36
- 239000000084 colloidal system Substances 0.000 claims abstract description 29
- 238000002156 mixing Methods 0.000 claims abstract description 28
- 239000004576 sand Substances 0.000 claims abstract description 28
- 239000002994 raw material Substances 0.000 claims abstract description 22
- 239000012615 aggregate Substances 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims description 31
- 238000005266 casting Methods 0.000 claims description 10
- 239000007787 solid Substances 0.000 claims description 6
- 239000011398 Portland cement Substances 0.000 claims description 5
- 239000011859 microparticle Substances 0.000 claims description 5
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 238000012360 testing method Methods 0.000 description 26
- 230000000052 comparative effect Effects 0.000 description 22
- 239000011148 porous material Substances 0.000 description 19
- 238000003756 stirring Methods 0.000 description 19
- 230000007704 transition Effects 0.000 description 14
- 230000008569 process Effects 0.000 description 8
- 238000011049 filling Methods 0.000 description 7
- 239000011159 matrix material Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 230000004048 modification Effects 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- 239000004570 mortar (masonry) Substances 0.000 description 6
- 238000005498 polishing Methods 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000006703 hydration reaction Methods 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 4
- 239000011178 precast concrete Substances 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 238000010276 construction Methods 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 230000036571 hydration Effects 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 229910052753 mercury Inorganic materials 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 244000137852 Petrea volubilis Species 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009435 building construction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000012669 compression test Methods 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 239000013505 freshwater Substances 0.000 description 1
- 239000004574 high-performance concrete Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
Abstract
The invention relates to the technical field of recycled concrete, and particularly discloses physical and nano technology modified recycled concrete and a preparation method thereof. The preparation method provided by the invention comprises the following steps: mixing the raw materials of the recycled concrete to obtain fresh recycled concrete; the raw materials of the recycled concrete comprise: water, cement, recycled aggregate, sand and nanomaterial; the nano material comprises nano silicon dioxide colloid and calcium carbonate particles; the mass of the nano silicon dioxide colloid accounts for 1-3% of the mass of the cement; the mass of the calcium carbonate particles accounts for 0.5-1.5% of the mass of the cement; and (3) placing the newly-mixed recycled concrete into a die, performing physical compression pouring, and releasing pressure and demoulding to obtain the recycled concrete. The invention can prepare the recycled concrete product with high strength and low porosity, does not greatly influence the manufacturing cost of the recycled concrete, and promotes the high-quality application of the recycled concrete in practical engineering.
Description
Technical Field
The invention belongs to the technical field of recycled concrete, and particularly relates to a physical and nano technology modified recycled concrete member and a preparation method thereof.
Background
With the acceleration of urban construction, rapid economic development and acceleration of industrialization process in China, the demand of commercial concrete is increasing. According to related data issued by the national statistical bureau, the national commercial concrete yield in 2019 was 25.5 hundred million m 3 The growth rate is 14.5% compared with 2018. The common concrete is used as one of the most main consumables for building construction, and the annual consumption is further increased along with the urban progress. The composition of the common concrete comprises: natural sand, fresh water and ordinary cement, the raw materials are subject to the problems of resource shortage, environmental pollution and the like, so that the realization of the resource sustainability of the building materials has important significance.
Firstly, natural sand is not renewable, and the ecological environment is damaged by excessive exploitation; meanwhile, the amount of building wastes generated in China is huge each year, the stacking and the treatment of the building wastes are the problems to be solved urgently, and the preparation of recycled concrete by taking the solid wastes as recycled aggregate is an ideal way for promoting the sustainable development of the building industry.
However, the recycled aggregate for the building has certain defects that mortar is adhered to the surface of the aggregate, a weaker aggregate-mortar contact interface and internal pores are main reasons for poor performance of recycled concrete, and each performance of the recycled concrete prepared by using the recycled aggregate is inferior to that of common concrete, so that the defect limits the practical application of the recycled concrete to a great extent. Therefore, the performance of the recycled concrete is improved, and the recycled concrete is an essential process for the application of the recycled concrete in the construction engineering.
Currently, researchers are conducting research on improving the comprehensive properties of recycled concrete with nanomaterials. The nano material has small particle size and high surface activity, can fill pores and cracks in the concrete, and meanwhile, part of nano materials have pozzolanic activity, so that a large amount of gel materials can be generated in the hydration process of the concrete, the interface transition area and the micro-pore structure of the concrete material can be improved, the structure is more compact, the early hydration reaction of the cement-based material can be effectively promoted, and the compressive strength of the concrete is enhanced. Most nanomaterials are relatively expensive and if used in large quantities, they raise the cost of concrete. Therefore, the application prospect of the nanomaterial is limited due to the economic consideration.
Disclosure of Invention
The invention aims to provide a physical and nano technology modified recycled concrete member and a preparation method thereof, and the recycled concrete member prepared by the method has excellent mechanical properties and durability, does not greatly influence the manufacturing cost of the recycled concrete, and promotes the high-quality application of the recycled concrete.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a physical and nano technology modified recycled concrete member, which comprises the following steps:
mixing the raw materials of the recycled concrete to obtain fresh recycled concrete; the raw materials of the recycled concrete comprise: water, cement, recycled aggregate, sand and nanomaterial; the nano material comprises nano silicon dioxide colloid and calcium carbonate particles; the mass of the nano silicon dioxide colloid accounts for 1-3% of the mass of the cement; the mass of the calcium carbonate particles accounts for 0.5-1.5% of the mass of the cement;
and filling the newly mixed recycled concrete into a mould, then carrying out physical compression pouring, selecting the shape of the selected mould according to actual requirements, and releasing pressure and demoulding to obtain the recycled concrete member.
Preferably, the pressure of the physical compression pouring is 3-30 MPa, and the dwell time is 5min.
Preferably, the particle size of the recycled aggregate is 5-20 mm, and the recycled aggregate is continuously graded;
the fineness modulus of the sand is 3.0;
the cement is Portland cement.
Preferably, the solid content of the nano silicon dioxide colloid is 25-35%, and the pH value is 9.0-10.5; the average grain diameter of the nano silicon dioxide is 11-13 nm, and the bulk density is 1.2g/cm 3 。
Preferably, the bulk density of the calcium carbonate microparticles is 0.69 to 0.73g/cm 3 An average particle diameter of 1250nm and a specific surface area of 2.15m 2 And/g, the water content is less than or equal to 5 percent.
Preferably, the mixing method of the fresh recycled concrete comprises the following steps:
mixing the calcium carbonate particles with cement to obtain cement mixed with the calcium carbonate particles;
mixing the nano silicon dioxide colloid with part of water to obtain a nano silicon dioxide solution;
and mixing the recycled aggregate, sand, cement mixed with calcium carbonate particles, nano silicon dioxide solution and the rest water to obtain the fresh recycled concrete.
Preferably, the method comprises the steps of releasing pressure, demolding and then directly obtaining an initial recycled concrete member, and curing the initial recycled concrete member to obtain the recycled concrete member; the curing temperature is 20+/-2 ℃, the relative humidity is 95%, and the curing time is 28 days.
The invention provides the physical and nano technology modified recycled concrete member prepared by the preparation method.
The invention provides a preparation method of a physical and nano technology modified recycled concrete member, which comprises the following steps: mixing the raw materials of the recycled concrete to obtain fresh recycled concrete; the raw materials of the recycled concrete comprise: water, cement, recycled aggregate, sand and nanomaterial; the nano material comprises nano silicon dioxide colloid and calcium carbonate particles; the mass of the nano silicon dioxide colloid accounts for 1-3% of the mass of the cement; the mass of the calcium carbonate particles accounts for 0.5-1.5% of the mass of the cement; and (3) placing the newly-mixed recycled concrete into a die, performing physical compression pouring, and releasing pressure and demoulding to obtain the recycled concrete member. Aiming at the problems of porous recycled aggregate concrete and poor mechanical property, the preparation method provided by the invention is improved by adding nano materials (nano silica colloid and calcium carbonate particles); meanwhile, the high cost of the nano material is considered, and the mass of the nano silicon dioxide colloid accounts for 1-3% of the mass of the cement; meanwhile, the mass of the calcium carbonate particles accounts for 0.5-1.5% of the mass of the cement, and the method of physical compression pouring is combined, and the excess air and slurry in the concrete are discharged by physical compression pouring extrusion, so that the nano materials, the recycled aggregate and the cement slurry are more tightly bonded, the compactness of the recycled concrete is obviously enhanced under the condition of small consumption of the nano materials through the cooperation of the nano materials and the physical compression pouring, the porosity is reduced, and the aim of improving the performance of the recycled concrete is fulfilled. Therefore, the invention can prepare the recycled concrete member product with excellent mechanical property and durability, and can not obviously improve the manufacturing cost of the recycled concrete and promote the high-quality application of the recycled concrete. In addition, the invention not only solves the problems of difficult treatment of construction waste and environmental pollution, but also changes the original defective recycled aggregate into valuable, becomes a raw material of high-performance concrete, and opens up a new way for the application mode of the recycled concrete.
Further, in the invention, the pressure of the physical compression casting is 3-30 MPa. In the preparation method provided by the invention, the mass of the nano silicon dioxide colloid accounts for 1-3% of the mass of the cement; the mass of the calcium carbonate particles accounts for 0.5-1.5% of the mass of the cement, and the invention can greatly improve the compressive strength of the concrete member and reduce the porosity of the matrix by regulating the mixing amount of the nano materials and the pressure of physical compression pouring, so that the bonding between the aggregate and the matrix is more compact, the durability of the concrete member is better than that of the traditional recycled concrete, and the concrete member is more suitable for engineering application.
The invention provides the regenerated concrete member prepared by the preparation method. The recycled concrete member provided by the invention is suitable for prefabricated concrete members with any shapes, including cylinders, prisms, cubes, concrete blocks, beams, plates, columns and the like, and has the advantages of high compressive strength, low porosity and low manufacturing cost.
Drawings
FIG. 1 is a BSE image taken along an interfacial transition region of a precast concrete member prepared in comparative example 1;
FIG. 2 is a BSE image taken along the interface transition region of the precast concrete member prepared in comparative example 2;
FIG. 3 is a BSE image taken along the interface transition region of the precast concrete member prepared in comparative example 3;
fig. 4 is a BSE view taken along the interface transition region of the precast concrete element prepared in example 1.
Detailed Description
The invention provides a preparation method of a physical and nano technology modified recycled concrete member, which comprises the following steps:
mixing the raw materials of the recycled concrete to obtain fresh recycled concrete; the raw materials of the recycled concrete comprise: water, cement, recycled aggregate, sand and nanomaterial; the nano material comprises nano silicon dioxide colloid and calcium carbonate particles; the mass of the nano silicon dioxide colloid accounts for 1-3% of the mass of the cement; the mass of the calcium carbonate particles accounts for 0.5-1.5% of the mass of the cement;
and (3) placing the newly-mixed recycled concrete into a die, performing physical compression pouring, and releasing pressure and demoulding to obtain the recycled concrete member.
In the present invention, all preparation materials/components are commercially available products well known to those skilled in the art unless specified otherwise.
According to the invention, raw materials of the recycled concrete are mixed to obtain new recycled concrete; the raw materials of the recycled concrete comprise: water, cement, recycled aggregate, sand and nanomaterial; the nano material comprises nano silicon dioxide colloid and calcium carbonate particles; the mass of the nano silicon dioxide colloid accounts for 1-3% of the mass of the cement; the mass of the calcium carbonate particles accounts for 0.5-1.5% of the mass of the cement.
In the invention, the mass percentage of the nano silicon dioxide colloid in the cement mass is preferably 2%; the mass of the calcium carbonate particles is preferably 1% of the mass of the cement.
In the invention, the raw materials of the recycled concrete are as follows: the dosage of water, cement, recycled aggregate and sand is determined according to the actual use requirement of the actual prepared recycled concrete material.
In the specific embodiment of the invention, the raw materials of the recycled concrete preferably comprise the following components in parts by mass: 201 parts of water, 368.8 parts of cement, 1128 parts of recycled aggregate, 691 parts of sand, 3.7-11.1 parts of nano silicon dioxide colloid and 1.8-5.5 parts of calcium carbonate particle nano material; more preferably comprises the following components in parts by weight: 201 parts of water, 368.8 parts of cement, 1128 parts of recycled aggregate, 691 parts of sand, 7.6 parts of nano silica colloid and 3.8 parts of calcium carbonate particle nano material.
In the present invention, the cement is particularly preferably Portland cement. In a specific embodiment of the present invention, the cement is specifically preferably Portland cement of P.O42.5.
In the present invention, the particle size of the recycled aggregate is preferably 5 to 20mm, and the recycled aggregate is preferably continuous graded.
In the present invention, the recycled aggregate is preferably washed and screened before use. The invention preferably removes impurities in the recycled aggregate by screening.
In the invention, through water absorption and crushing index tests, the average water absorption of the recycled aggregate is 5.50%, and the average crushing index is 15.80%. The water absorption and crushing indexes of the recycled aggregate are larger than those of the natural coarse aggregate, and the recycled aggregate is inferior to the natural coarse aggregate in strength and quality.
The invention has no special requirements on the type and the source of the recycled aggregate.
In the present invention, the sand is ordinary river sand. In the present invention, the fineness modulus of the sand is preferably 3.0.
In the present invention, the solid content of the nanosilica colloid is preferably 25% to ultra35%, more preferably 30%, and the pH is preferably 9 to 10.5, more preferably 10.1; the average particle diameter of the nanosilica is preferably 11 to 13nm, more preferably 12.1nm, and the bulk density is preferably 1.2g/cm 3 。
In the present invention, the bulk density of the calcium carbonate microparticles is preferably 0.69 to 0.73g/cm 3 More preferably 0.71g/cm 3 The average particle diameter is preferably 1250nm, and the specific surface area is preferably 2.15m 2 The water content per gram is preferably not more than 5% (i.e. the solids content is not less than 95%). In the present invention, the pH of the calcium carbonate microparticles is preferably 8.0.
In the invention, the mixing method of the fresh recycled concrete preferably comprises the following steps:
mixing the calcium carbonate particles with cement to obtain cement mixed with the calcium carbonate particles;
mixing the nano silicon dioxide colloid with part of water to obtain a nano silicon dioxide solution;
and mixing the recycled aggregate, sand, cement mixed with calcium carbonate particles, nano silicon dioxide solution and the rest water to obtain the fresh recycled concrete.
The invention mixes the calcium carbonate particles with cement to obtain the cement mixed with the calcium carbonate particles. In the present invention, the mixing of the calcium carbonate microparticles and cement is preferably: and sprinkling the calcium carbonate particles into the cement, and stirring and mixing for 2min. The invention disperses the calcium carbonate particles in the cement, which is beneficial to the uniform dispersion of the calcium carbonate particles in the fresh concrete.
The nano silicon dioxide colloid and part of water are mixed to obtain the nano silicon dioxide solution. The invention has no special requirement on the mixing process of the nano silicon dioxide colloid and part of water. The invention dilutes the nano silicon dioxide colloid by partial water, which is favorable for the uniform dispersion of the nano silicon dioxide in the fresh concrete. In the present invention, the mass ratio of the part of water to the remaining water is preferably 1:1.
After the cement mixed with the calcium carbonate particles and the nano silicon dioxide solution are obtained, the recycled aggregate, the sand, the cement mixed with the calcium carbonate particles, the nano silicon dioxide solution and the rest water are mixed to obtain the fresh recycled concrete.
In the invention, the concrete preparation method of the fresh mixed recycled concrete comprises the following steps:
s1, mixing and stirring the recycled aggregate and sand, wherein the stirring time is preferably 1min;
s2, adding the cement mixed with the calcium carbonate particles into the mixture prepared in the step S1, and stirring for preferably 1min;
s3, slowly pouring the nano silicon dioxide solution into the mixture prepared in the step S2, and stirring for 1min;
s4, slowly pouring the residual water into the mixture prepared in the step S3, and stirring for preferably 2 minutes;
the invention preferably carries out the mixing in the steps, so that the uniform mixing of the raw materials of the recycled concrete can be ensured, and particularly the uniform dispersion of the nano materials can be ensured.
After the newly mixed recycled concrete is obtained, the newly mixed recycled concrete is put into a die and subjected to physical compression pouring, and the recycled concrete member is obtained after pressure relief and demoulding.
The present invention has no special requirements on the shape and size of the mold. In a specific embodiment of the invention, the die is cylindrical in shape, the bottom surface of the cylindrical die is preferably 150mm in diameter and 400mm in depth, so that a standard cylindrical test piece with the diameter of 150mm and the height of 300mm is obtained through pressure casting. In the case of other shapes of prefabricated elements, such as beam panels, etc., special custom molds are required.
In the invention, in the process of filling the fresh concrete body into the mould, the invention preferably vibrates the fresh concrete so as to discharge part of air doped in the mould in the process of filling the fresh concrete, and preliminarily reduce pore generation.
In the invention, the physical compression casting is preferably performed by a compression tool, and in the specific embodiment of the invention, the tool for physical compression casting comprises a jack and a pressure head matched with a mould.
In the invention, the physical compression pouring is preferably carried out by adopting a force transmission compression mode.
In a specific embodiment of the present invention, the specific implementation method of the physical compression casting is as follows: the jack is adopted to apply pressure to the top of the newly-mixed recycled concrete in the die through the die pressure head, the pressure sensor is adopted to measure the pressure applied by the jack in real time, the numerical value is displayed through the numerical value display instrument, and the pressure maintaining compression is carried out when the pressure value reaches the pressure of the physical compression pouring. In the present invention, the pressure sensor is provided at the bottom of the mold.
In the invention, the pressure of the physical compression pouring is preferably 3-30 MPa, more preferably 15MPa; the dwell time is preferably 5min.
In the present invention, the pressure of the physical compression casting should be suitable, and the pressure of the physical compression casting is preferably 3-30 MPa. When the pressure of physical compression casting exceeds the range, the further improvement effect on the concrete performance is obviously reduced, and meanwhile, the risk that the strength is not increased and is not reduced due to crushing of the aggregate in the concrete exists; when the physical compression pouring pressure is lower than the range, the pores in the recycled concrete cannot be effectively reduced, and the cohesiveness of the matrix and the aggregate is not tight, so that the mechanical properties of the concrete member are affected.
In the invention, the initial recycled concrete member is directly obtained after the pressure relief and demoulding, and the invention further comprises the step of curing the initial recycled concrete member to obtain the recycled concrete member. In the invention, the curing temperature is 20+/-2 ℃, the relative humidity is 95%, and the curing time is 28 days.
The invention provides the physical and nano technology modified recycled concrete member prepared by the preparation method.
The invention has no special requirements on the shape and the size of the recycled concrete member, and is suitable for prefabricated concrete members with any shape, including cylinders, prisms, cubes, concrete blocks, beams, plates or columns.
Compared with the defects of low strength, high porosity and poor durability of the traditional recycled concrete, the recycled concrete member prepared by the method disclosed by the invention is modified by adopting the nano material, and meanwhile, the concrete member obtained by combining a physical compression pouring method is greatly improved in compressive strength, the pore defects are also improved, the bonding between aggregate and a matrix is tighter, the durability is better than that of the traditional recycled concrete, and the method is favorable for promoting the high-quality application of the recycled concrete.
The invention adopts the nano material to fill the pores in the recycled concrete, can effectively improve the performance of the recycled concrete, but has limited gain amplitude, and meanwhile, the cost problem of the nano material is not ignored. The invention adopts a method combining physical compression pouring and nano material modification, can greatly reduce the porosity of concrete, improve the strength and the durability, and simultaneously can keep the price equivalent to that of common concrete products. The preparation method provided by the invention has the advantages of excellent performance of the recycled concrete and economical efficiency, and provides a novel high-quality low-cost building material for engineering application.
The technical solutions provided by the present invention are described in detail below in conjunction with examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.
Example 1
The recycled coarse aggregate used in the embodiment is continuously graded, the grain size range is 5-20 mm, and before the recycled coarse aggregate is used, the recycled coarse aggregate is cleaned and filtered out of impurities. In this example, the average value of the water absorption and the crushing index of the recycled aggregate was 5.50% and the average value of the crushing index was 15.80% by performing the water absorption and the crushing index test on the recycled aggregate.
The sand used in this example was ordinary river sand with a fineness modulus of 3.0.
The cement used in this example was Portland cement of P.O42.5.
The nanosilica colloid used in this example had a solids content of about 30%, a pH of 10.1 and a bulk density of 1.2g/cm 3 The average particle diameter was 12.1nm.
Accumulation of calcium carbonate particles used in the present exampleDensity of 0.71g/cm 3 An average particle diameter of 1250nm and a specific surface area of 2.15m 2 /g, solids content 95% and pH 8.0.
The present example was prepared by weighing the raw materials in the proportions of group 4 in table 1. In order to ensure that the nano material can be uniformly distributed in the recycled concrete, the weighed calcium carbonate particles are sprayed in the cement and stirred for 2min to be uniformly distributed, so that the cement mixed with the calcium carbonate particles is obtained; the nano silicon dioxide colloid is poured into half of water to be evenly dispersed, so as to prepare the nano silicon dioxide solution.
And then pouring the recycled coarse aggregate and sand into a stirring pot, mixing and stirring for 1min, pouring cement mixed with calcium carbonate particles, stirring for 1min, adding the solution uniformly dispersed with nano silicon dioxide, stirring for 1min, and finally adding half of water, and uniformly stirring for 2min to obtain the nano material modified fresh-mixed recycled concrete.
Filling the freshly mixed recycled concrete modified by the nano material into a cylindrical mold, vibrating the concrete, performing experimental study according to a physical compression pouring recycled aggregate concrete performance modification mechanism to enable the concrete to reach a specified height (300 mm), then compressing the freshly mixed concrete by adopting a jack-mold pressure head-freshly mixed concrete force transmission compression mode, measuring the stress by a pressure sensor at the bottom of a mold device, and maintaining the stress for 24 hours after reaching the pressure of 15 MPa. After 24 hours the stress was relieved and the outer mould was removed.
After demoulding, the concrete member is cured for 28 days at a temperature of 20.+ -. 2 ℃ and a relative humidity of 95%. And taking out the concrete after the curing age to obtain the regenerated concrete member subjected to physical compression pouring and nano material modification.
TABLE 1 concrete raw material mixing ratio in example 1 and comparative examples 1 to 3
Comparative example 1
The recycled coarse aggregate, sand and cement used in this comparative example were prepared in the same manner as in example 1, and weighed according to the raw material ratios of group 1 in table 1. And then pouring the recycled coarse aggregate and sand into a stirring pot, mixing and stirring for 1min, pouring cement, stirring for 1min, adding water, and uniformly stirring for 2min to obtain the freshly mixed recycled concrete.
And filling the newly mixed recycled concrete into a cylindrical mould, vibrating the concrete, researching according to a physical compression pouring recycled aggregate concrete performance modification mechanism test to enable the concrete to reach a specified height (300 mm), pouring under the condition that the jack pressing stress is 0MPa, and keeping the stress of 0MPa for 24 hours. After 24 hours the stress was relieved and the outer mould was removed.
After demoulding, the concrete member is cured for 28 days at a temperature of 20.+ -. 2 ℃ and a relative humidity of 95%. And taking out the concrete after the curing age to obtain the recycled concrete member.
Comparative example 2
The recycled coarse aggregate, sand and cement used in this comparative example were weighed in the same proportions as in example 1 and prepared in accordance with the raw materials of group 2 in Table 1. And then pouring the recycled coarse aggregate and sand into a stirring pot, mixing and stirring for 1min, pouring cement, stirring for 1min, adding water, and uniformly stirring for 2min to obtain the freshly mixed recycled concrete.
Filling fresh recycled concrete into a cylindrical mold, vibrating the concrete, researching according to a physical compression pouring recycled aggregate concrete performance modification mechanism test to enable the concrete to reach a specified height (300 mm), then compressing the fresh concrete by adopting a jack-mold pressure head-fresh concrete force transmission compression mode, measuring the stress by a pressure sensor at the bottom of a mold device, and maintaining the stress for 24 hours after reaching the pressure of 15 MPa. After 24 hours the stress was relieved and the outer mould was removed.
After demoulding, the concrete member is cured for 28 days at a temperature of 20.+ -. 2 ℃ and a relative humidity of 95%. And taking out the concrete after the curing age to obtain the regenerated concrete member subjected to physical compression pouring.
Comparative example 3
The comparative example was prepared by weighing the raw materials of group 3 in table 1 in proportion, and then preparing nanomaterial-modified fresh-mix recycled concrete in the same manner as in example 1.
And filling the freshly mixed recycled concrete modified by the nano material into a cylindrical mould, vibrating the concrete, researching and leading the concrete to reach a specified height (300 mm) according to a physical compression pouring recycled aggregate concrete performance modification mechanism test, pouring under the condition that the jack pressing stress is 0MPa, and keeping the 0MPa stress for 24 hours. After 24 hours the stress was relieved and the outer mould was removed.
After demoulding, the concrete member is cured for 28 days at a temperature of 20.+ -. 2 ℃ and a relative humidity of 95%. And taking out the concrete after the curing age to obtain the nano material modified recycled concrete member.
Test example 1
The present test example was subjected to mechanical properties test for the recycled concrete members produced in example 1 and comparative examples 1 to 3:
(1) Experimental procedure
The compressive strength of each group of concrete was measured according to GB/T50081-2002 Standard of Experimental methods for mechanical Properties of common concrete.
(2) Experimental results
The experimental results are shown in table 2:
table 2 results of concrete mechanical properties test
As can be seen from the contents of table 2, the compressive strength and peak strain of the common recycled concrete (group 1, comparative example 1) are at poor levels, and the strength is low, and the load bearing capacity is easily lost. After physical compression pouring is applied to the recycled concrete (group 2, comparative example 2), the compressive strength is obviously improved, the lifting rate is up to 88.1%, and the peak strain is slightly improved; the test piece obtained by adding the nano material (group 3, comparative example 3) into the common recycled concrete has the same enhancement of compressive strength and peak strain. The mechanical property of the recycled concrete (group 4, example 1) modified by the physical compression pouring and the nano material, which integrates the two improvement methods, has the most obvious improvement effect, the compression strength improvement rate is as high as 141.6 percent, which is far higher than the single improvement effect of the groups 2 and 3, and the peak strain is also better than that of the rest 3 groups. Experimental data results show that the nano material and the physical compression pouring method can both play a role in improving the gain of the recycled concrete, and the novel concrete obtained by combining the two methods can play a role of 1+1 being more than 2, and the two methods are matched with each other to make up the original defect of the recycled aggregate, so that the performance of the recycled concrete is greatly improved, and the recycled concrete has wider application in engineering.
Test example 2
This test example 4 sets of recycled concrete prepared in example 1 and comparative examples 1 to 3 were subjected to mercury intrusion test run:
(1) Experimental procedure
Taking a concrete cylinder test block which is destroyed in 28 days, and taking out a concrete matrix which does not contain coarse aggregate. And (3) tapping a mortar block with the longest dimension not larger than 1cm by using a small hammer, putting the mortar block into a vacuum drying oven at 60 ℃ for drying for 48 hours, removing water in mortar pores, and preventing the influence on test results. A Poremaster-60MIP device was used in the test, and the upper mercury pressure limit during the test was set to 30000psi. And testing the influence of the physical compression pouring behavior on the internal pores of the concrete test piece.
(2) Experimental results
The specific test results are shown in table 3:
table 3 concrete mercury-pressing experimental data sheet
As can be seen from Table 3, the porosity of the conventional recycled concrete (group 1, comparative example 1) was high. And after pressurization (group 2, comparative example 2) and addition of nano materials (group 3, comparative example 3) can effectively reduce the pores in the recycled concrete, the reduction of the porosity means that the internal structure of the concrete is more compact, the performance is improved, and the influence of external environmental factors on the internal structure of the concrete through the pores is reduced, so that the possibility of durability of the concrete is reduced. And group 4 (example 1) combines two methods of physical compression casting and nanomaterial to further reduce the porosity of the recycled concrete, and the performance and durability are better than the effect of the two methods used independently.
Test example 3
The present test example was a back scattering test for 4 sets of recycled concrete prepared in example 1 and comparative examples 1 to 3:
the experimental process comprises the following steps: 1. and taking out a relatively complete sample with the size of about 2cm from the cylindrical test piece which has passed the axial compression test, wherein the sample needs to comprise a relatively obvious interface transition zone and cannot be cracked so as to maintain the relatively complete interface transition zone in the subsequent operation process. 2. The observation surface of the rugged interface transition area is primarily polished by 320-mesh sand paper, absolute ethyl alcohol is required to be added on the polishing surface in time during polishing, the polishing surface is cooled and sequentially polished until the observation surface is smooth, polishing is carried out for 30 seconds each time, and the floating dust on the surface of the observation surface is required to be cleaned by an ultrasonic cleaner after polishing each time, so that further hydration of a sample is avoided, and the cleaning liquid in the ultrasonic cleaner is absolute ethyl alcohol. After the observation surface is flat, an optical microscope is used for preliminary observation, so that the observation surface is ensured not to be damaged by cracks and the like generated by excessive polishing. Then dried in a vacuum oven at 60 ℃ for 48 hours. 3. After the sample is taken out from the vacuum drying oven, epoxy resin with the mass ratio of the curing agent to the resin being 1:3 is prepared, resin pouring is carried out on the epoxy resin by utilizing the vacuum mosaic, the vacuum mosaic can fully fill the resin into the holes of the sample, the structure of the sample is more stably supported, and the shooting result is more convenient to observe. After standing for 1 day, the mold can be removed to obtain a back scattering sample. 4. Scanning electron microscope SEM was used to capture images along the transition zone (ITZ) between the new and old mortar interfaces.
Experimental results:
the bonding state and the pore distribution state along the Interface Transition Zone (ITZ) of the recycled aggregate are mainly observed in the back scattering test. In the BSE image obtained by photographing, the brightness of the pixels varies with the number of atoms, so that the darkest areas are pores, and then aggregate particles, hydration products and unreacted water. The upper gray threshold of the porosity is determined by the turning point of the cumulative luminance histogram of the BSE image.
Fig. 1 to 4 are BSE diagrams taken in order of an Interface Transition Zone (ITZ) of a general recycled concrete (comparative example 1 product), a physical compression cast recycled concrete (comparative example 2 product), a recycled concrete added with a nanomaterial (comparative example 3 product), and a recycled concrete cast by physical compression and modified with a nanomaterial (example 1 product), the left diagram in fig. 1 to 4 is a raw picture taken, and the right diagram is a distribution diagram of pores after treatment, wherein a black region represents pores. In fig. 1, the common recycled concrete has more pores in the transition area, dark color and poor bonding performance, and the phenomenon is improved after the nano material is added (fig. 3). On the basis of this, the pressure is applied again to obtain the figure 4, the pores of the interface transition zone are obviously reduced, and the bonding performance of the recycled aggregate and the matrix is the best. As can be seen from a comparison of fig. 1-4, the black portion in the ITZ zone is changed from deep to shallow, from less to less, and represents a decrease in the number of pores in the zone, and a decrease in the number of pores in the interface transition zone indicates that the matrix is more tightly bonded to the aggregate, and that the overall performance exhibited by the concrete is more excellent.
Although the foregoing embodiments have been described in some, but not all embodiments of the invention, other embodiments may be obtained according to the present embodiments without departing from the scope of the invention.
Claims (8)
1. A method for preparing a physically and nanotechnology modified recycled concrete member, comprising the steps of:
mixing the raw materials of the recycled concrete to obtain fresh recycled concrete; the raw materials of the recycled concrete comprise: water, cement, recycled aggregate, sand and nanomaterial; the nano material comprises nano silicon dioxide colloid and calcium carbonate particles; the mass of the nano silicon dioxide colloid accounts for 1-3% of the mass of the cement; the mass of the calcium carbonate particles accounts for 0.5-1.5% of the mass of the cement;
and (3) placing the newly-mixed recycled concrete into a die, performing physical compression pouring, and releasing pressure and demoulding to obtain the recycled concrete member.
2. The method according to claim 1, wherein the pressure of the physical compression casting is 3-30 MPa and the dwell time is 5min.
3. The method according to claim 1, wherein the recycled aggregate has a particle size of 5 to 20mm and is continuous graded;
the fineness modulus of the sand is 3.0;
the cement is Portland cement.
4. The preparation method according to claim 1, wherein the nano silica colloid has a solid content of 25-35% and a pH of 9.0-10.5; the particle diameter of the nano silicon dioxide is 11-13 nm, and the bulk density is 1.2g/cm 3 。
5. The method according to claim 1, wherein the bulk density of the calcium carbonate microparticles is 0.69 to 0.73g/cm 3 An average particle diameter of 1250nm and a specific surface area of 2.15m 2 And/g, the water content is less than or equal to 5 percent.
6. The method of preparing the fresh recycled concrete according to claim 1, wherein the mixing method of the fresh recycled concrete comprises the steps of:
mixing the calcium carbonate particles with cement to obtain cement mixed with the calcium carbonate particles;
mixing the nano silicon dioxide colloid with part of water to obtain a nano silicon dioxide solution;
and mixing the recycled aggregate, sand, cement mixed with calcium carbonate particles, nano silicon dioxide solution and the rest water to obtain the fresh recycled concrete.
7. The method of claim 1, wherein the releasing and demoulding are followed by directly obtaining an initial recycled concrete member, and further comprising curing the initial recycled concrete member to obtain the recycled concrete member; the curing temperature is 20+/-2 ℃, the relative humidity is 95%, and the curing time is 28 days.
8. The physical and nanotechnology modified recycled concrete member prepared by the preparation method of any one of claims 1 to 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310835745.9A CN116751015A (en) | 2023-07-10 | 2023-07-10 | Physical and nano technology modified recycled concrete member and preparation method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310835745.9A CN116751015A (en) | 2023-07-10 | 2023-07-10 | Physical and nano technology modified recycled concrete member and preparation method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116751015A true CN116751015A (en) | 2023-09-15 |
Family
ID=87947843
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310835745.9A Pending CN116751015A (en) | 2023-07-10 | 2023-07-10 | Physical and nano technology modified recycled concrete member and preparation method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116751015A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117805156A (en) * | 2024-02-27 | 2024-04-02 | 太原理工大学 | Method for testing hydration degree of interface transition zone between repair material and base material |
| CN117805156B (en) * | 2024-02-27 | 2024-05-10 | 太原理工大学 | Method for testing hydration degree of interface transition zone between repair material and base material |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108726956A (en) * | 2018-08-08 | 2018-11-02 | 宝辰永宇（滁州）新材料科技有限公司 | A kind of modification regeneration concrete and preparation method thereof |
| CN110104997A (en) * | 2019-04-26 | 2019-08-09 | 四川衡鼎建材有限公司 | A kind of regeneration concrete and its production technology |
| CN112745075A (en) * | 2020-12-31 | 2021-05-04 | 南通友力混凝土有限公司 | Corrosion-resistant recycled concrete and production process thereof |
| CN113501691A (en) * | 2021-07-02 | 2021-10-15 | 广东工业大学 | High-strength nano silicon dioxide recycled concrete and preparation method thereof |
| CN113735619A (en) * | 2021-06-21 | 2021-12-03 | 湖南大学 | Second-order stirring technology for concrete containing recycled brick aggregate |
| CN114714478A (en) * | 2022-04-07 | 2022-07-08 | 深圳大学 | Concrete compression pouring method capable of reducing cement consumption |
-
2023
- 2023-07-10 CN CN202310835745.9A patent/CN116751015A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108726956A (en) * | 2018-08-08 | 2018-11-02 | 宝辰永宇（滁州）新材料科技有限公司 | A kind of modification regeneration concrete and preparation method thereof |
| CN110104997A (en) * | 2019-04-26 | 2019-08-09 | 四川衡鼎建材有限公司 | A kind of regeneration concrete and its production technology |
| CN112745075A (en) * | 2020-12-31 | 2021-05-04 | 南通友力混凝土有限公司 | Corrosion-resistant recycled concrete and production process thereof |
| CN113735619A (en) * | 2021-06-21 | 2021-12-03 | 湖南大学 | Second-order stirring technology for concrete containing recycled brick aggregate |
| CN113501691A (en) * | 2021-07-02 | 2021-10-15 | 广东工业大学 | High-strength nano silicon dioxide recycled concrete and preparation method thereof |
| CN114714478A (en) * | 2022-04-07 | 2022-07-08 | 深圳大学 | Concrete compression pouring method capable of reducing cement consumption |
Non-Patent Citations (1)
| Title |
|---|
| 苏鑫: "纳米二氧化硅和纳米碳酸钙减胶剂改性混凝土性能研究", 《中国优秀硕士学位论文全文数据库 工程科技Ⅰ辑》, 15 November 2022 (2022-11-15), pages 015 - 126 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117805156A (en) * | 2024-02-27 | 2024-04-02 | 太原理工大学 | Method for testing hydration degree of interface transition zone between repair material and base material |
| CN117805156B (en) * | 2024-02-27 | 2024-05-10 | 太原理工大学 | Method for testing hydration degree of interface transition zone between repair material and base material |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| WO2021012309A1 (en) | Inorganic fiber toughened inorganic composite artificial stone panel and preparation method therefor | |
| WO2021012310A1 (en) | High-toughness inorganic composite artificial stone panel and preparation method therefor | |
| WO2022062493A1 (en) | Building waste burn-free regeneration brick and preparation method thereof | |
| CN108609952B (en) | Composite modified concrete and method for testing interface transition zone thereof | |
| CN101033120A (en) | Formulation for producing concrete brick from foundry waste sand and producing method thereof | |
| CN112897956A (en) | Environment-friendly inorganic artificial stone and preparation method thereof | |
| CN115321903A (en) | Inorganic artificial stone plate and preparation method thereof | |
| CN114714478B (en) | Concrete compression pouring method capable of reducing cement consumption | |
| CN112142400A (en) | Concrete with steel slag and waste rubber as fine aggregate and application thereof | |
| CN113896475B (en) | Method for preparing high-strength baking-free solid bricks by using rock wool furnace bottom slag | |
| WO2021012308A1 (en) | Organic fiber toughened inorganic composite artificial stone panel and preparation method therefor | |
| CN103193443A (en) | Method for preparing baking-free slag brick | |
| CN111392738B (en) | Method for preparing high-scour-resistance nano-silica concrete by using modified rice hull ash | |
| CN1944317A (en) | Formula for producing color tile from casting waste sand and its producing method | |
| CN111995322A (en) | Preparation method of recycled brick-concrete aggregate pervious concrete | |
| CN116751015A (en) | Physical and nano technology modified recycled concrete member and preparation method thereof | |
| CN112341121B (en) | Light high-strength concrete for civil engineering | |
| CN115073086A (en) | Modified concrete regenerated from waste fresh concrete and preparation method thereof | |
| CN103193441A (en) | Method for preparing slag steam-cured brick | |
| CN105776986A (en) | Green cement-type binding material and preparation method thereof | |
| CN111233378B (en) | Steel fiber-micro silicon powder concrete and preparation method thereof | |
| CN114835457B (en) | Ultra-high toughness mixture regenerated by waste combined micro powder and preparation method thereof | |
| CN1274623C (en) | Steel slag marble and its preparing method | |
| CN112142408B (en) | Lightweight medium-high pressure die and preparation method thereof | |
| CN115504759B (en) | Compression molding ultra-light high-strength concrete and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |