Method for preparing recycled concrete based on activated water and recycled concrete
阅读说明：本技术 基于活化水制备再生混凝土的方法及再生混凝土 (Method for preparing recycled concrete based on activated water and recycled concrete ) 是由 刘全喜 冼德明 高青峰 于 2021-11-11 设计创作，主要内容包括：本申请涉及基于活化水制备再生混凝土的方法及再生混凝土,涉及建筑材料技术领域。再生混凝土包括如下重量份的原料制成：再生粗骨料1000-1500份、细骨料550-660份、普通硅酸盐水泥220-320份、硅藻土改性层状双氢氧化物微胶囊15-40份、矿物掺合料25-40份、减水剂1-6份和活化水150-220份,所述硅藻土改性层状双氢氧化物微胶囊包括囊芯、囊壁和硅藻土,所述硅藻土负载于囊壁表面,所述囊芯包括层状双氢氧化物,所述囊壁为温度敏感材料。本申请具有提升混凝土耐久性的效果。(The application relates to a method for preparing recycled concrete based on activated water and the recycled concrete, and relates to the technical field of building materials. The recycled concrete is prepared from the following raw materials in parts by weight: the composite material comprises the following components, by weight, 1000 parts of regenerated coarse aggregate, 660 parts of fine aggregate, 220 parts of ordinary portland cement, 15-40 parts of diatomite modified layered double hydroxide microcapsules, 25-40 parts of mineral admixture, 1-6 parts of a water reducing agent and 220 parts of activated water, wherein the diatomite modified layered double hydroxide microcapsules comprise a capsule core, a capsule wall and diatomite, the diatomite is loaded on the surface of the capsule wall, the capsule core comprises layered double hydroxide, and the capsule wall is a temperature sensitive material. This application has the effect that promotes concrete durability.)
1. The preparation method of the recycled concrete based on the activated water is characterized by comprising the following steps of: the composite material comprises the following components, by weight, 1000 parts of regenerated coarse aggregate, 660 parts of fine aggregate, 220 parts of ordinary portland cement, 15-40 parts of diatomite modified layered double hydroxide microcapsules, 25-40 parts of mineral admixture, 1-6 parts of a water reducing agent and 220 parts of activated water, wherein the diatomite modified layered double hydroxide microcapsules comprise a capsule core, a capsule wall and diatomite, the diatomite is loaded on the surface of the capsule wall, the capsule core comprises layered double hydroxide, and the capsule wall is a temperature sensitive material.
2. The activated water-based recycled concrete prepared according to claim 1, wherein: the capsule wall is prepared from the following raw materials in parts by weight:
40-45 parts of PLGA-PEG-PLGA copolymer;
30-35 parts of N-isopropyl acrylamide;
2-3 parts of acrylic acid;
2-3 parts of azobisisoheptonitrile;
1-2 parts of diethylaminopropylamine;
1-2 parts of lecithin;
10-24 parts of polyurethane resin;
and a proper amount of distilled water.
3. The activated water-based recycled concrete produced according to claim 2, wherein: the preparation method of the diatomite modified layered double hydroxide microcapsule comprises the following steps: dissolving PLGA-PEG-PLGA copolymer and N-isopropyl acrylamide in distilled water in an inert gas atmosphere to obtain a first mixture, mixing the first mixture with acrylic acid, azodiisoheptanonitrile, diethylaminopropylamine and polyurethane resin, heating to 65-80 ℃, stirring for 10-15h, cooling, dialyzing to obtain a capsule wall prepolymer, adding layered double hydroxide into the capsule wall prepolymer, uniformly stirring, carrying out suction filtration and drying to obtain layered double hydroxide microcapsules, and loading diatomite on the surface of the capsule wall of the microcapsules.
4. The activated water-based recycled concrete prepared according to claim 3, wherein: the method for loading the diatomite on the surface of the microcapsule wall comprises the following steps: mixing 1-3 parts of diatomite, 10-15 parts of layered double hydroxide capsules, 1-3 parts of silane coupling agent and 20-25 parts of toluene, ultrasonically dispersing, reacting at room temperature, centrifuging, and drying to obtain the diatomite modified layered double hydroxide microcapsules.
5. The activated water-based recycled concrete prepared according to claim 3, wherein: the layered double hydroxide is nitrite ion modified layered double hydroxide or nitrate ion modified layered double hydroxide.
6. The activated water-based recycled concrete produced according to claim 5, wherein: the layered double hydroxide is washed with acetone and dried before being added to the wall prepolymer.
7. The activated water-based preparation recycled concrete of claim 1, wherein the preparation of the recycled coarse aggregate comprises the following steps:
(1) crushing and sieving the waste concrete to obtain coarse aggregate with the particle size of 5-30 mm;
(2) acidifying the coarse aggregate to obtain acidified coarse aggregate;
(3) and cleaning the acidified coarse aggregate until the pH value of the cleaning solution is neutral, and drying the cleaned acidified coarse aggregate to obtain the recycled coarse aggregate.
8. The method for preparing recycled concrete based on activated water as claimed in any one of claims 1 to 7, comprising the steps of:
s1: mixing and stirring activated water and a water reducing agent uniformly to obtain a first mixture;
s2: uniformly stirring the portland cement, the diatomite modified layered double hydroxide microcapsule and the mineral admixture to obtain a second mixture;
s3: uniformly mixing and stirring the second mixture, the fine aggregate and the recycled coarse aggregate to obtain a third mixture;
s4: and mixing and stirring the first mixture and the third mixture to prepare the recycled concrete.
Technical Field
The application relates to the technical field of building materials, in particular to a method for preparing recycled concrete based on activated water and the recycled concrete.
Background
The regenerated concrete is prepared by crushing, cleaning and grading waste concrete blocks, mixing the crushed, cleaned and graded waste concrete blocks with a grading agent according to a certain proportion, partially or completely replacing natural aggregates such as sand stones and the like, and adding cement, water and the like.
In the related technology, waste building concrete is crushed and screened to obtain recycled concrete coarse aggregate to replace partial concrete coarse aggregate, and the recycled concrete is formed by matching the recycled concrete coarse aggregate with sand, cement, water and the like. However, the regenerated aggregates obtained after crushing and screening have more edges and corners and can generate micro cracks inside, compared with natural coarse aggregates, the regenerated coarse aggregates have large crushing index, high water absorption rate and large porosity, so that the regenerated concrete has lower strength and poorer durability, and in order to improve the durability of the regenerated concrete, mineral admixtures or specific admixtures are often added into the regenerated concrete to realize the effect of improving the durability of the concrete. The layered double hydroxide is used in the field of concrete because of its ion exchange characteristics, and when concrete is formed, cement and the layered double hydroxide are generally mixed in advance by a dry mixing method, and then concrete forming operation is performed.
In view of the above-mentioned related technologies, the layered double hydroxide is a nano-scale particle, and is not uniformly stirred in the micron-scale cement powder, and is easily agglomerated, so the inventors believe that there is a problem that the durability of the concrete needs to be improved.
Disclosure of Invention
In order to improve the durability of concrete, the present application provides a method for preparing recycled concrete based on activated water and recycled concrete.
In a first aspect, the activated water-based recycled concrete provided by the application adopts the following technical scheme:
the preparation of the recycled concrete based on activated water is prepared from the following raw materials in parts by weight: the composite material comprises the following components, by weight, 1000 parts of regenerated coarse aggregate, 660 parts of fine aggregate, 220 parts of ordinary portland cement, 15-40 parts of diatomite modified layered double hydroxide microcapsules, 25-40 parts of mineral admixture, 1-6 parts of a water reducing agent and 220 parts of activated water, wherein the diatomite modified layered double hydroxide microcapsules comprise a capsule core, a capsule wall and diatomite, the diatomite is loaded on the surface of the capsule wall, the capsule core comprises layered double hydroxide, and the capsule wall is a temperature sensitive material.
By adopting the technical scheme, the components are combined with each other to form a concrete basic skeleton, and then the diatomite modified layered double hydroxide microcapsule is added into the concrete basic skeleton, wherein the layered double hydroxide has interlayer anion exchangeability, so that the diatomite modified layered double hydroxide microcapsule can be used for adsorbing erosive ions in concrete, larger pores in a regenerated concrete skeleton can be filled after the diatomite modified layered double hydroxide microcapsule is added into the concrete, the compactness of the concrete is improved, in addition, the diatomite modified layered double hydroxide microcapsule improves the particle size of the layered double hydroxide and the compatibility with the concrete, the dispersion uniformity of the layered double hydroxide in silicate cement is improved, the micropores on the wall of the microcapsule are expanded by hydration heat generated in the hydration process of the concrete, the uniformly dispersed layered double hydroxide is released from the microcapsule and participates in the hydration process, the durability of the concrete is greatly improved, and the manufacturing process of the concrete is more green and environment-friendly.
Optionally, the capsule wall is prepared from the following raw materials in parts by weight:
40-45 parts of PLGA-PEG-PLGA copolymer;
30-35 parts of N-isopropyl acrylamide;
2-3 parts of acrylic acid;
2-3 parts of azobisisoheptonitrile;
1-2 parts of diethylaminopropylamine;
1-2 parts of lecithin;
10-24 parts of polyurethane resin;
and a proper amount of distilled water.
By adopting the technical scheme, the PLGA-PEG-PLGA copolymer and the N-isopropyl acryloyl are both temperature sensitive polymers, the temperature sensitive polymers are matched with polyurethane resin, azodiisoheptanonitrile is used as an initiator, diethylaminopropylamine is used as a cross-linking agent, lecithin is used as a stabilizing agent, and acrylic acid is used for adjusting the slow release temperature of the temperature sensitive polymers to prepare the temperature sensitive capsule wall prepolymer, so that the raw materials are easy to obtain and the preparation is convenient.
Optionally, the preparation method of the diatomite modified layered double hydroxide microcapsule comprises the following steps: dissolving PLGA-PEG-PLGA copolymer and N-isopropyl acrylamide in an inert gas atmosphere, adding acrylic acid, azodiisoheptanonitrile, diethylaminopropylamine and polyurethane resin, mixing and heating to 65-80 ℃, stirring for 10-15h, cooling, dialyzing to obtain a capsule wall prepolymer, adding layered double hydroxide into the capsule wall prepolymer, uniformly stirring, carrying out suction filtration and drying to obtain layered double hydroxide microcapsules, wherein the diatomite is loaded on the surface of the capsule wall of the microcapsules.
By adopting the technical scheme, at normal temperature, the micropores on the capsule wall are in a closed or open state, when the hydration heat is released in the hydration process of the concrete and the temperature is increased, the micropores on the capsule wall are in an open state, and the layered double hydroxide in the capsule wall is released through the micropores on the capsule wall.
Optionally, the method for loading the diatomite on the surface of the microcapsule wall comprises the following steps: mixing 1-3 parts of diatomite, 10-15 parts of layered double hydroxide microcapsules, 1-3 parts of silane coupling agent and 20-25 parts of toluene, performing ultrasonic dispersion, reacting at room temperature, centrifuging, and drying to obtain the diatomite modified layered double hydroxide microcapsules.
By adopting the technical scheme, the diatomite modified layered double hydroxide microcapsule has larger grain size than layered double hydroxide, and the main components of diatomite are similar to the components of cement, so that the dispersion uniformity of the diatomite modified layered double hydroxide microcapsule in the cement is improved, and the durability of the concrete is improved by the layered double hydroxide.
Optionally, the layered double hydroxide is nitrite ion modified layered double hydroxide or nitrate ion modified layered double hydroxide.
By adopting the technical scheme, the nitrite ion modified layered double hydroxide or the nitrate ion modified layered double hydroxide has better adsorbability on aggressive ions and gases invading into concrete; in addition, nitrite ions can release nitrite ions having a rust-resisting effect on the reinforcing steel bar while adsorbing erosive ions and gas, and the durability of the concrete is further improved.
Optionally, the layered double hydroxide is washed with acetone and dried prior to addition to the wall prepolymer.
By adopting the technical scheme, the organic solvent is used for removing the bound water from the surface of the hydrophilic layered double hydroxide, so that the dispersity of the layered double hydroxide is improved, and the layered double hydroxide is uniformly dispersed in the process of preparing the microcapsule.
Optionally, the preparation of the recycled coarse aggregate comprises the following steps:
(1) crushing and sieving the waste concrete to obtain coarse aggregate with the particle size of 5-30 mm;
(2) acidifying the coarse aggregate to obtain acidified coarse aggregate;
(3) and cleaning the acidified coarse aggregate until the pH value of the cleaning solution is neutral, and drying the cleaned acidified coarse aggregate to obtain the recycled coarse aggregate.
By adopting the technical scheme, the concrete hydration products on the surface of the recycled coarse aggregate are removed, and the raised impurities on the surface are removed, so that the recycled coarse aggregate is fully combined with the cement material hydration products in the recycled concrete, and the strength of the recycled concrete is improved.
In a second aspect, the present application provides a method for preparing recycled concrete based on activated water, comprising the steps of:
s1: mixing and stirring activated water and a water reducing agent uniformly to obtain a first mixture;
s2: uniformly stirring the portland cement, the diatomite modified layered double hydroxide microcapsule and the mineral admixture to obtain a second mixture;
s3: uniformly mixing and stirring the second mixture, the fine aggregate and the recycled coarse aggregate to obtain a third mixture;
s4: and mixing and stirring the first mixture and the third mixture to prepare the recycled concrete.
By adopting the technical scheme, the raw materials are mixed in batches, so that the raw materials are fully mixed, the raw materials are fully exerted, and are matched for use together to prepare the activated water-based recycled concrete.
In summary, the present application has the following beneficial effects:
1. adding secondary diatomite modified layered double hydroxide microcapsules into recycled concrete, wherein firstly, the layered double hydroxide absorbs aggressive ions invading into the concrete; secondly, after the diatomite modified layered double hydroxide microcapsules are added into concrete, larger pores in a recycled concrete framework can be filled, and the compactness of the concrete is improved; finally, the diatomite modified layered double hydroxide microcapsule improves the particle size of the layered double hydroxide and the compatibility with concrete, improves the dispersion uniformity of the layered double hydroxide in portland cement, the hydration heat generated in the hydration process of the concrete enables the capsule wall of the microcapsule to be dissolved, the uniformly dispersed layered double hydroxide is released from the microcapsule and participates in the hydration process, the durability of the concrete is greatly improved, and the manufacturing process of the concrete is more green and environment-friendly.
2. The layered double hydroxide is cleaned and dried by acetone before the microcapsule is prepared, and the organic solvent removes the bound water on the surface of the layered double hydroxide, so that the dispersibility of the layered double hydroxide is improved, and the layered double hydroxide is uniformly dispersed in the process of preparing the microcapsule.
Detailed Description
The present application will be described in further detail with reference to examples.
Preparation of Mg by coprecipitation method6Al2（OH）16CO3.4H2And O, preparing nitrate radical intercalation layered double hydroxide and nitrite radical intercalation layered double hydroxide by adopting a roasting rehydration method.
Preparation example of diatomaceous earth modified layered double hydroxide microcapsule
Preparation example 1
Dissolving 42kg of PLGA-PEG-PLGA copolymer and 33kg of N-isopropylacrylamide in a nitrogen atmosphere, adding 2.3kg of acrylic acid, 2kg of azobisisoheptonitrile, 1.2kg of diethylaminopropylamine, 1.2kg of lecithin, 18.3kg of polyurethane resin and a proper amount of distilled water, wherein the distilled water is used for dissolving the PLGA-PEG-PLGA copolymer, the N-isopropylacrylamide, the acrylic acid, the azobisisoheptonitrile and the diethylaminopropylamine, the addition amount of the above substances can be used for completely dissolving the substances, mixing and heating the substances, heating the mixture to 65 ℃, stirring the mixture for 12 hours, cooling the mixture, dialyzing the mixture, adding distilled water every 3 hours in the dialysis process, dialyzing the mixture for 5 days to obtain a capsule wall prepolymer, adding 5kg of layered double hydroxide into the capsule wall prepolymer, wherein in the preparation example, the layered double hydroxide is nitrite intercalation double hydroxide, stirring the mixture uniformly, carrying out suction filtration and drying to obtain a layered double hydroxide microcapsule; 10kg of layered double hydroxide microcapsule, 1kg of silane coupling agent and 2kg of diatomite are dissolved in 20kg of toluene, and ultrasonic treatment is carried out for 5min, the centrifugal rotation speed is 1500r/min, and the centrifugal time is 5min, so that the diatomite is loaded on the surface of the microcapsule wall, and the diatomite modified layered double hydroxide microcapsule is obtained.
Preparation example 2
40kg of PLGA-PEG-PLGA copolymer and 30kg of N-isopropylacrylamide are taken to be dissolved in nitrogen atmosphere, 2kg of acrylic acid, 2.5kg of azobisisoheptonitrile, 1.7kg of diethylaminopropylamine, 1.5kg of lecithin, 22.3kg of polyurethane resin and a proper amount of distilled water are added, the distilled water is used for dissolving the PLGA-PEG-PLGA copolymer, the N-isopropylacrylamide, the acrylic acid, the azobisisoheptonitrile and the diethylaminopropylamine as long as the added amount can completely dissolve the substances, the mixture is heated, the heating temperature is up to 65 ℃, the mixture is stirred for 12 hours, the mixture is cooled and dialyzed, distilled water is added every 3 hours in the dialysis process, the dialysis is carried out for 5 days, the capsule wall prepolymer is obtained after the dialysis, 5kg of layered double hydroxide is added into the capsule wall prepolymer, in the preparation example, the layered double hydroxide is the nitrite intercalation layered double hydroxide, stirring uniformly, filtering, and drying to obtain layered double hydroxide microcapsules; 10kg of layered double hydroxide microcapsule, 1kg of silane coupling agent and 2kg of diatomite are dissolved in 20kg of toluene, and ultrasonic treatment is carried out for 5min, the centrifugal rotation speed is 1500r/min, and the centrifugal time is 5min, so that the diatomite is loaded on the surface of the microcapsule wall, and the diatomite modified layered double hydroxide microcapsule is obtained.
Preparation example 3
Dissolving 45kg of PLGA-PEG-PLGA copolymer and 35kg of N-isopropylacrylamide in a nitrogen atmosphere, adding 3kg of acrylic acid, 3kg of azobisisoheptonitrile, 2kg of diethylaminopropylamine, 2kg of lecithin, 10kg of polyurethane resin and a proper amount of distilled water, wherein the distilled water is used for dissolving the PLGA-PEG-PLGA copolymer, the N-isopropylacrylamide, the acrylic acid, the azobisisoheptonitrile and the diethylaminopropylamine, the adding amount can completely dissolve the substances, mixing and heating the substances, heating the mixture to 65 ℃, stirring the mixture for 12 hours, cooling the mixture, dialyzing the mixture, adding distilled water into the mixture every 3 hours during the dialysis process, dialyzing the mixture for 5 days to obtain a capsule wall prepolymer, adding 5kg of layered double hydroxide into the capsule wall prepolymer, and in the preparation example, the layered double hydroxide is nitrite intercalation double hydroxide, stirring uniformly, filtering, and drying to obtain layered double hydroxide microcapsules; 10kg of layered double hydroxide microcapsule, 1kg of silane coupling agent and 2kg of diatomite are dissolved in 20kg of toluene, and ultrasonic treatment is carried out for 5min, the centrifugal rotation speed is 1500r/min, and the centrifugal time is 5min, so that the diatomite is loaded on the surface of the microcapsule wall, and the diatomite modified layered double hydroxide microcapsule is obtained.
Preparation example 4
The difference from preparation example 1 is that the layered double hydroxide is washed and dried with acetone before being added to the wall prepolymer to obtain the diatomite modified layered double hydroxide microcapsule.
Preparation example 5
The difference from the preparation example 1 is that nitrate radical intercalation layered double hydroxide with equal mass is used for replacing nitrite radical intercalation layered double hydroxide when preparing the diatomite modified microcapsule, so as to obtain the diatomite modified layered double hydroxide microcapsule.
Preparation example 6
The difference from the preparation example 5 is that the diatomite modified layered double hydroxide is obtained by cleaning and drying the nitrate radical intercalated layered double hydroxide by using acetone before adding the nitrate radical intercalated layered double hydroxide into the capsule wall prepolymer.
Preparation example 7
Except for the difference from preparation example 6 that in the heating step, heating was performed to 55 ℃ to obtain a diatomaceous earth-modified layered double hydroxide microcapsule.
Preparation example 8
Except for the difference from preparation example 6 that in the heating step, heating was performed to 70 ℃ to obtain a diatomaceous earth-modified layered double hydroxide microcapsule.
Preparation example 9
Except for the difference from preparation example 6 that in the heating step, heating was performed to 80 ℃ to obtain a diatomaceous earth-modified layered double hydroxide microcapsule.
Preparation example 10
Except for the difference from preparation example 6 that in the heating step, heating was performed to 90 ℃ to obtain a diatomaceous earth-modified layered double hydroxide microcapsule.
Examples
Example 1
The preparation of the recycled concrete based on activated water is prepared from the following raw materials in parts by weight: 1300kg of recycled coarse aggregate, 600kg of fine aggregate, 280kg of ordinary portland cement, 30kg of diatomite-modified layered double hydroxide microcapsule, 30kg of mineral admixture, 3kg of polycarboxylic acid water reducing agent and 180kg of activated water, wherein the diatomite-modified layered double hydroxide microcapsule is prepared by the preparation example 1, the mineral admixture is zeolite powder, the recycled coarse aggregate is recycled coarse aggregate with the particle size of 5-30mm sold in the market, the fine aggregate is machine-made sand, and the cement is purchased from P.042.5 produced by Fuping ecological cement Limited liability company in Shaanxi.
The preparation method for preparing the recycled concrete based on the activated water comprises the following steps:
s1: mixing and stirring activated water and a water reducing agent uniformly to obtain a first mixture;
s2: uniformly stirring ordinary portland cement, diatomite modified nitrite intercalation layered double hydroxide microcapsules and a mineral admixture to obtain a second mixture;
s3, mixing and stirring the second mixture, the fine aggregate and the recycled coarse aggregate uniformly to obtain a third mixture;
s4: and mixing and stirring the first mixture and the third mixture to prepare the recycled concrete.
Examples 2 to 10
Recycled concrete was prepared based on activated water, which is different from example 1 in that the diatomaceous earth-modified layered double hydroxide microcapsules prepared in preparation examples 2 to 10 were sequentially used.
Example 11
The preparation of recycled concrete based on activated water differs from that of example 1 in that it is made from raw materials comprising, in parts by weight: 1000kg of recycled coarse aggregate, 550kg of fine aggregate, 220kg of ordinary portland cement, 20kg of diatomite-modified layered double hydroxide microcapsule, 25kg of mineral admixture, 1kg of polycarboxylic acid water reducing agent and 150kg of activated water.
Example 12
The preparation of recycled concrete based on activated water differs from that of example 1 in that it is made from raw materials comprising, in parts by weight: 1500kg of recycled coarse aggregate, 650kg of fine aggregate, 340kg of ordinary portland cement, 35kg of diatomite-modified layered double hydroxide microcapsule, 40kg of mineral admixture, 6kg of polycarboxylic acid water reducing agent and 220kg of activated water.
Example 13
Recycled concrete was prepared based on activated water, which is different from example 1 in that 15kg of the diatomaceous earth-modified nitrite intercalated layered double hydroxide microcapsules was used in the S2 step.
Example 14
Recycled concrete was prepared based on activated water, which is different from example 1 in that 40kg of the diatomaceous earth-modified nitrite intercalated layered double hydroxide microcapsules was used in the S2 step.
Example 15
The recycled concrete was prepared based on activated water, which is different from example 1 in that the preparation of the recycled coarse aggregate includes the following steps:
(1) crushing and sieving the waste concrete to obtain coarse aggregate with the particle size of 5-30 mm;
(2) acidizing the coarse aggregate by using oxalic acid, wherein the mass concentration of the oxalic acid is 20g/L, and the volume ratio of the coarse aggregate to the oxalic acid is 1: 4, soaking for 2 hours to obtain acidified coarse aggregate;
(3) and cleaning the acidified recycled coarse aggregate until the pH value of the cleaning solution is neutral, and drying the cleaned acidified coarse aggregate to obtain the recycled coarse aggregate.
Comparative example
Comparative example 1
Recycled concrete was prepared based on activated water, which differs from example 1 in that the diatomaceous earth-modified layered double hydroxide microcapsules were not added.
Comparative example 2
Recycled concrete was prepared based on activated water, which is different from example 1 in that the diatomaceous earth-modified layered double hydroxide was replaced with an equal mass of layered double hydroxide.
Comparative example 3
Recycled concrete was prepared based on activated water, differing from example 1 in that the mass of the diatomaceous earth-modified layered double hydroxide was 10 kg.
Comparative example 4
Recycled concrete was prepared based on activated water, differing from example 1 in that the mass of the diatomaceous earth-modified layered double hydroxide was 60 kg.
Comparative example 5
Recycled concrete was prepared based on the activated water, which is different from example 1 in that the activated water used in the step of S1 was replaced with tap water of equal mass.
Performance test
Detection method
Concrete strength detection
The concrete prepared in examples 1-15 and comparative examples 1-5 was subjected to a 28d compressive strength test according to GB/T50081-2002 Standard test methods for mechanical Properties of general concrete. And taking the test piece out of the maintenance place, and then carrying out a test in time, and wiping the surface of the test piece and the surfaces of the upper and lower bearing plates clean. And placing the test piece on a lower pressing plate or a base plate of the testing machine, wherein the pressure bearing surface of the test piece is vertical to the top surface during molding. The center of the test piece is aligned with the center of the lower pressure plate of the testing machine, the testing machine is started, and when the upper pressure plate is close to the test piece or the steel base plate, the ball seat is adjusted to enable contact to be balanced. In the test process, the load is continuously and uniformly applied, when the concrete strength grade is less than C30, the application speed is 0.3-0.5 MPa per second, and when the concrete strength grade is more than or equal to C30 and less than C60, the application speed is 0.5-0.8 MPa per second; when the strength grade of the concrete is more than or equal to C60, 0.8-1.0 MPa is taken per second. When the test piece begins to deform rapidly after approaching the damage, the adjustment of the accelerator of the testing machine is stopped until the test piece is damaged. The failure load was then recorded as in table 1.
Secondly, detecting the concrete carbonization depth
The concrete prepared in examples 1 to 15 and comparative examples 1 to 5 were subjected to a carbonation depth test. Firstly, a test block is subjected to a rapid carbonization experiment, and CO in a carbonization box2Rapidly carbonizing at 20% concentration and 20 ℃ and 75% humidity for 56d, and taking out the test block after the carbonization experiment is finished; preparing a phenolphthalein reagent: preparing a phenolphthalein solvent with the phenolphthalein concentration of 1% -2% by using 75% alcohol solution and white phenolphthalein powder, and filling the phenolphthalein solvent into a sprayer for later use, wherein the solvent is colorless and transparent liquid; drilling holes at the measuring points by using a percussion drill provided with a drill bit with the diameter of 20mm, wherein the drilling depth is less than the thickness of the concrete protective layer; after the hole is formed, the round hairbrush is used for removing the scraps and powder in the hole to expose the concreteNew stubble; spraying a phenolphthalein indicator on the wall of the hole to be measured; after the phenolphthalein indicator changes color, measuring the depth from the surface of the concrete to a phenolphthalein color change junction by using a depth measuring caliper to be accurate to 1 mm; the phenolphthalein indicator changes from colorless to purple, the concrete is not carbonized, and the phenolphthalein indicator keeps the concrete carbonized at the colorless place; uniformly numbering the measuring areas and the measuring holes, drawing a schematic diagram, and marking the measuring results; the measured values were collated by calculating the average values and the data are reported in Table 1.
Third, detecting the diffusion coefficient of chloride ion in concrete
The concrete prepared in examples 1 to 15 and comparative examples 1 to 5 was subjected to a chloride ion diffusion coefficient test, which was determined according to the RCM method in GB/T50082-2009 Standard test methods for Long-term Performance and durability of ordinary concrete, and the test results were collated and recorded in Table 1.
Table 1 shows the results of tests on the compressive strength, the depth of carbonation and the diffusion coefficient of chloride ions of the recycled concrete obtained in examples 1 to 15 and comparative examples 1 to 5
Example/comparative example numbering
28d compressive strength/(MPa)
Carbonization depth (mm)
Diffusion coefficient of chloride ion (1O)-6mm2/s）
Example 1
33.6
9.11
8.105
Example 2
32.5
9.35
8.356
Example 3
32.1
9.57
8.425
Example 4
35.2
7.56
6.387
Example 5
33.9
9.05
8.058
Example 6
35.4
7.24
6.148
Example 7
30.1
11.02
10.259
Example 8
33.2
9.13
8.264
Example 9
30.3
10.87
10.015
Example 10
28.7
13.23
12.984
Example 11
33.0
10.02
8.885
Example 12
32.8
10.52
9.834
Example 13
30.5
10.52
9.834
Example 14
34.5
8.71
7.032
Example 15
37.8
7.03
5.031
Comparative example 1
22.7
18.32
15.385
Comparative example 2
25.1
17.05
14.022
Comparative example 3
29.6
11.89
11.034
Comparative example 4
32.9
10.08
8.901
Comparative example 5
32.5
9.56
8.556
It can be seen from the combination of example 1, comparative examples 1-2 and table 1 that the strength of the recycled concrete without adding the diatomite modified layered double hydroxide in comparative example 1 is the lowest, and the carbonization depth and the chloride ion diffusion coefficient are the largest, the strength of the concrete is increased and the carbonization depth and the chloride ion diffusion coefficient are reduced after adding the layered double hydroxide in comparative example 2, while the strength of the recycled concrete with adding the diatomite modified layered double hydroxide microcapsule is the highest and the carbonization depth and the chloride ion diffusion coefficient are the smallest, which indicates that the durability of the recycled concrete can be greatly improved by the diatomite modified layered double hydroxide microcapsule, probably because the diatomite modified layered double hydroxide microcapsule is more uniformly dispersed in the recycled concrete and has stronger compatibility with the recycled concrete, the diatomite modified layered double hydroxide microcapsule is preferred.
It can be seen by combining examples 1, 4-6 and table 1 that the compressive strength of examples 4 and 6 is higher than that of examples 1 and 5, and the compressive strength of example 6 is the highest, which is probably because nitrite intercalated layered double hydroxide has better dispersibility in the microcapsule preparation process after being washed by acetone, and is more uniformly dispersed after being added into concrete, and the effect of improving the strength of the recycled concrete is stable; on the other hand, acetone removes the bound water on the surface of the nitrite intercalation layered double hydroxide, and after the diatomite modified nitrite intercalation layered double hydroxide microcapsule is dissolved, the layered double hydroxide is exposed in the concrete environment, and the activated water participating in the hydration process is absorbed in the hydration process, so that the water-cement ratio of the recycled concrete is reduced to a certain extent, and the strength of the recycled concrete is improved. The carbonization depth of examples 4 and 6 was lower than that of examples 1 and 5, and the carbonization depth of example 6 was the lowest, and the chloride diffusion coefficient of examples 4 and 6 was smaller than that of examples 1 and 5, and the chloride diffusion coefficient of example 6 was the lowest, which is likely due to the larger interlayer spacing of the nitrate intercalated layered double hydroxide, more adsorption sites, and the stronger resistance to aggressive gases and aggressive ions than the nitrite intercalated layered double hydroxide; therefore, acetone-washed diatomaceous earth-modified nitrate intercalated layered double hydroxide microcapsules are preferred.
It can be seen by combining example 1, examples 7-10 and table 1 that the compressive strength of examples 7 and 9 is slightly lower than that of example 1, the compressive strength of example 10 is obviously lower than that of example 1, and the compressive strength of example 8 is slightly higher than that of example 1, which indicates that during the process of preparing the layered double hydroxide microcapsules, the reaction is not favorably carried out at too high and too low temperatures, and the performance of the generated diatomite modified nitrite intercalated layered double hydroxide is unstable, thus affecting the durability of the recycled concrete, therefore, the temperature is preferably 70 ℃.
Combining examples 11-14 and comparative examples 1-4 and combining table 1, it can be seen that the compressive strength, carbonization depth and chloride ion diffusion coefficient of examples 11-12 are all similar to those of example 1, the compressive strength, carbonization depth and chloride ion diffusion coefficient of example 13 are less than that of example 1, the carbonization depth and chloride ion diffusion coefficient of example 13 are greater than those of example 1, the compressive strength of example 14 is greater than that of example 1, and the carbonization depth and chloride ion diffusion coefficient of example 14 are less than those of example 1, indicating that within a certain range, the addition amount of the diatomite-modified nitrite intercalated layered double hydroxide positively correlates with the compressive strength and durability of regeneration to concrete; the compressive strength of comparative example 3 and comparative example 4 is less than that of example 1, and the carbonization depth and the chloride ion diffusion coefficient of comparative example 3 and comparative example 4 are greater than those of example 1; the compressive strength of comparative example 3 is less than that of comparative example 4, and the carbonization depth and the chloride ion diffusion coefficient of comparative example 3 are greater than those of comparative example 4; the fact that excessive diatomite modified nitrite intercalation layered double hydroxide is added has negative effects on the compressive strength and the durability of the concrete is shown, probably because excessive diatomite modified nitrite intercalation layered double hydroxide excessively adsorbs activated water participating in hydration in the recycled concrete, the water-cement ratio of the recycled concrete is greatly reduced, the recycled concrete is not fully hydrated, and the negative effects on the strength and the durability of the recycled concrete are generated; the added diatomite modified nitrite intercalation layered double hydroxide is too little, and the compressive strength improvement and durability improvement effects on concrete are not obvious, which is probably because the too little diatomite modified nitrite intercalation layered double hydroxide cannot be fully and uniformly mixed with the recycled concrete, and the chloride ion adsorption and carbonization resistance of the diatomite modified nitrite intercalation layered double hydroxide reach a saturation value, so the dosage of the diatomite modified layered double hydroxide is preferably 15-40 kg.
As can be seen by combining examples 1, 14-15 with Table 1, example 15 has the greatest compressive strength and the smallest carbonization depth and chloride ion diffusion coefficient, which indicates that the pretreatment of the coarse aggregate has an effect of promoting the strength of the recycled concrete, probably because the neutralization treatment of the acidification treatment removes the hydration products coated on the surface of the recycled coarse aggregate, so that the recycled coarse aggregate and the hydration products of the recycled concrete are cemented together, the compactness of the concrete is improved, the carbonization resistance and the chlorine salt corrosion resistance of the recycled concrete are improved, and therefore, the recycled coarse aggregate subjected to acidification and neutralization is preferably used for preparing the recycled concrete.
Combining example 1 and comparative example 5 with table 1, it can be seen that the strength of the recycled concrete in comparative example 5 is lower than that of the recycled concrete in example 1, and the carbonization depth and the chloride ion diffusion coefficient of the recycled concrete in comparative example 5 are higher than those of the recycled concrete in example 1, indicating that the activated water enhances the binding effect between the components in the concrete, and therefore, the activated water is preferably used for the preparation of the recycled concrete.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.