CN113248202A - Cement-based recycled concrete - Google Patents
Cement-based recycled concrete Download PDFInfo
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- CN113248202A CN113248202A CN202110531981.2A CN202110531981A CN113248202A CN 113248202 A CN113248202 A CN 113248202A CN 202110531981 A CN202110531981 A CN 202110531981A CN 113248202 A CN113248202 A CN 113248202A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/20—Resistance against chemical, physical or biological attack
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Chemical Kinetics & Catalysis (AREA)
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- Organic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention provides cement-based recycled concrete, and relates to the technical field of building materials. According to the invention, the waste granite powder and the silica fume are simultaneously doped to replace part of cement, and the proportion of the waste granite powder to the silica fume is adjusted, so that under the condition of reducing the use of cement raw materials, the waste granite powder and the silica fume can play good synergistic effect and complementary effect, thereby overcoming the problems of low activity of the doped granite waste stone powder and cracking in a curing stage caused by the hydrated volume expansion of the silica fume, and further effectively improving the mechanical property and durability of the cement-based recycled concrete; the performance of the cement-based recycled concrete meets the use requirement, the recycling rate of the waste granite is effectively improved, and the resource recycling is realized.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to cement-based recycled concrete.
Background
Granite stone is widely applied to the construction of hard landscapes such as urban buildings, municipal roads, garden sculptures and building sundries due to the advantages of fine structure and hard texture. However, a large amount of stone waste and waste stone powder are generated in the granite mining and processing process, and the recycling is difficult, so that the problems of resource waste and environmental pollution are serious. A large number of researches show that the granite powder belongs to inert substances and basically has no activity, so that the recovery rate of the granite powder is low, and other active materials need to be compounded when the granite powder is applied to the preparation of recycled concrete to a greater extent.
The existing active admixture comprises fly ash, blast furnace slag, silica fume and the like, wherein the fly ash and the blast furnace slag are relatively short in resources, and the silica fume has a large reserve compared with the fly ash and the blast furnace slag, and has more pozzolanic activity. Although the doped silica fume can promote the hydration reaction to a certain extent, the defect that the gel system is easy to expand due to the large heat of hydration exists, so that the concrete is easy to crack when being cured.
Therefore, how to improve the performance of the cured cement-based recycled concrete while reusing the waste granite waste to prepare the cement-based recycled concrete becomes a difficult problem to be solved urgently at present.
Disclosure of Invention
The cement-based recycled concrete provided by the invention can reuse waste granite waste to replace part of cement, realizes resource recycling, and simultaneously can enable the cement-based recycled concrete to have good mechanical property and durability.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides cement-based recycled concrete which is prepared from the following raw materials in parts by weight: 16.2-34.2 parts of cement, 7.2-21.6 parts of waste granite powder, 2.88-3.6 parts of silica fume, 45.57-65.1 parts of river sand, 0-120.9 parts of broken stone, 18-22.5 parts of water and 0.3-0.4 part of water reducing agent; the mass ratio of the waste granite powder to the silica fume is (2-6) to 1.
Preferably, the raw materials for preparing the cement-based recycled concrete further comprise 79.98-140.43 parts of waste granite aggregate according to parts by weight.
Preferably, the particle size of the waste granite powder is 1-200 μm.
Preferably, the components of the silica fume comprise, by weight: SiO 22 92.5～94.5％，Al2O3 3.06～4.26％，Fe2O31.51-2.71%, CaO 1.32-1.52% and MgO 0.47-0.67%.
Preferably, the particle size of the silica fume is less than 0.3 μm.
Preferably, the waste granite aggregate comprises a waste granite coarse aggregate and a waste granite fine aggregate; the mass ratio of the waste granite coarse aggregate to the waste granite fine aggregate is (3-6.2): 1.
preferably, the particle size of the waste granite coarse aggregate is 5-9.5 mm; the particle size of the waste granite fine aggregate is 3-4.9 mm.
Preferably, the river sand has a particle size of < 5 mm.
Preferably, the particle size of the crushed stone is 5-9.5 mm.
Preferably, the water reducing rate of the water reducing agent is 16-20%.
The invention provides cement-based recycled concrete which is prepared from the following raw materials in parts by weight: 16.2-34.2 parts of cement, 7.2-21.6 parts of waste granite powder, 2.88-3.6 parts of silica fume, 45.57-65.1 parts of river sand, 0-120.9 parts of broken stone, 18-22.5 parts of water and 0.3-0.4 part of water reducing agent; the mass ratio of the waste granite powder to the silica fume is (2-6) to 1. According to the invention, the waste granite powder and the silica fume are simultaneously doped to replace part of cement, and the proportion of the waste granite powder to the silica fume is adjusted, so that under the condition of reducing the use of cement raw materials, the waste granite powder and the silica fume can play good synergistic effect and complementary effect, thereby overcoming the problems of low activity of the doped granite waste stone powder and cracking in a curing stage caused by the hydrated volume expansion of the silica fume, and further effectively improving the mechanical property and durability of the cement-based recycled concrete; the performance of the cement-based recycled concrete meets the use requirement, the recycling rate of the waste granite is effectively improved, and the resource recycling is realized.
The results of the examples of the invention show that the compressive strength of the cement-based recycled concrete prepared in the examples of the invention is 15.32-25.34 MPa when cured for 3d, 21.63-33.89 MPa when cured for 7d, 28.93-41.06 MPa when cured for 28d, the flexural strength of the cement-based recycled concrete is 1.65-2.89 MPa when cured for 3d, 2.03-3.58 MPa when cured for 7d, 2.366-4.42 MPa when cured for 28d, and the cement-based recycled concrete is carbonized in 3d, 7d, 14d and 28d respectively, and the carbonization depth of the cement-based recycled concrete is 4.63-4.71 mm when cured for 3d, 4.71-5.34 mm when cured for 7d, 5.28-5.98 mm when cured for 14d, and 6.24-7.57 mm when cured for 28 d. Therefore, the cement-based recycled concrete 3d provided by the invention has the best mechanical property and durability, namely the early strength of the cement-based recycled concrete can be effectively improved, but the performance of the finally prepared cement-based recycled concrete can meet the use requirement of C40 ordinary cement-based concrete.
Detailed Description
The invention provides cement-based recycled concrete which is prepared from the following raw materials in parts by weight: 16.2-34.2 parts of cement, 7.2-21.6 parts of waste granite powder, 2.88-3.6 parts of silica fume, 45.57-65.1 parts of river sand, 0-120.9 parts of broken stone, 18-22.5 parts of water and 0.3-0.4 part of water reducing agent; the mass ratio of the waste granite powder to the silica fume is (2-6): 1.
the raw materials for preparing the cement-based recycled concrete comprise, by mass, 16.2-34.2 parts of cement, preferably 19.8-30.6 parts of cement, and more preferably 21.6-27.0 parts of cement. According to the invention, the cement-based recycled concrete can be ensured to have good mechanical property and durability by adding a small amount of cement.
In the invention, the particle size of the cement is preferably 5-45 μm, and more preferably 10-35 μm. By selecting the particle size range, the invention is more beneficial to ensuring that the cement-based recycled concrete and other ashes form a gel system with good hydration effect under the condition of larger specific surface area, thereby fully bonding aggregate to form cement-based recycled concrete with good mechanical property and durability.
In the present invention, the cement is preferably portland cement, and more preferably P · O42.5 portland cement. According to the invention, the cement of the above kind is selected, so that the performance of the waste granite powder is improved, and the activity of a gelling system is improved.
The raw materials for preparing the cement-based recycled concrete further comprise 7.2-21.6 parts by mass of waste granite powder, preferably 10.8-14.4 parts by mass, and more preferably 11.52-14.5 parts by mass of cement, wherein the mass part of the cement is 16.2-34.2 parts by mass. According to the invention, by adding the granite powder in parts by mass, the mechanical property and durability of the cement-based recycled concrete can be ensured on the basis of a larger recovery utilization rate.
In the invention, the particle size of the waste granite powder is preferably 1-200 μm. According to the invention, the particle size of the waste granite powder is selected to be within the range, so that the particle size of the waste granite powder is matched with the particle size of cement, the waste granite powder is fully contacted with the cement, the activity of the waste granite is effectively improved, and the hydration effect of a gelling system is improved.
The raw materials for preparing the cement-based recycled concrete also comprise 2.88-3.6 parts of silica fume, preferably 2.95-3.3 parts of silica fume, and more preferably 3.0-3.1 parts of cement by mass part of 16.2-34.2 parts of cement. According to the invention, by controlling the content of the silica fume within the range, the silica fume can be matched with cement to improve the activity of the waste granite powder, so that the cement-based recycled concrete with excellent mechanical property and durability can be obtained under the condition of larger mixing amount of the granite powder.
In the present invention, the components of the silica fume preferably include, in weight percent: SiO 22 92.5～94.5％，Al2O3 3.06～4.26％，Fe2O31.51-2.71%, CaO 1.32-1.52%, and MgO 0.47-0.67%, more preferably comprising: SiO 22 93.24％，Al2O3 3.16％，Fe2O31.61%, CaO 1.42% and MgO 0.57%. The invention can lead the waste granite powder and the silica fume to be mixed in the slurry by controlling the components of the silica fume to be in the rangeContaining a large amount of SiO2，SiO2May be beta-C2S and C3The hydration of S provides active sites, so that sufficient space is provided for hydration products, cement is completely hydrated, excessive aggregation of the hydration products in local areas is avoided, the distribution of the hydration products is more uniform, the directional enrichment of CH is particularly reduced, the generation of large-particle-size CH on the surface of aggregate is reduced, and the strength of a slurry system is improved.
In the present invention, the particle size of the silica fume is preferably < 0.3 μm, and more preferably 0.1 to 0.3 μm. The silica fume with the particle size less than 0.3 mu m is selected, so that the silica fume has a large specific surface area, and the hydration reaction effect of a gelling system can be effectively improved; meanwhile, the particle sizes of the cement, the waste granite powder and the silica fume in the cement-based recycled concrete are different, so that the micro-aggregate filling effect plays a role, and the waste granite powder and the silica fume are mixed in different particle sizes, so that the capillary pores in the hardened cement paste become thinner and thinner, the porosity is reduced, the structural compactness is improved, and the mechanical property and the durability of the cement-based concrete are further improved.
In the invention, the mass ratio of the waste granite powder to the silica fume is (2-6): 1, preferably (3-5): 1, more preferably 4: 1. According to the invention, the granite powder and the silica fume can play good synergistic effect and complementary effect by controlling the mass ratio of the granite powder to the silica fume, so that the problem of low activity of the waste granite powder doped with granite and the problem of cracking in a curing stage caused by hydrated volume expansion of the silica fume are solved.
The raw materials for preparing the cement-based recycled concrete also preferably comprise 79.98-140.43 parts of waste granite aggregate, more preferably 82-135 parts, and most preferably 85-130 parts of cement by mass part of 16.2-34.2 parts. According to the invention, waste granite can be used as aggregate, and the addition amount of the waste granite is controlled within the range, so that the recovery rate of the waste granite is improved on the basis of ensuring the mechanical property and durability of the cement-based recycled concrete.
In the invention, the waste granite aggregate preferably comprises waste granite coarse aggregate and waste granite fine aggregate; the mass ratio of the waste granite coarse aggregate to the waste granite fine aggregate is preferably (3-6.2): 1, preferably (3.5-5.5): 1, more preferably (4.5 to 5.0): 1.
in the invention, the particle size of the waste granite coarse aggregate is preferably 5-9.5 mm, and more preferably 6-8 mm; the particle size of the waste granite fine aggregate is preferably 3-4.9 mm, and more preferably 3.5-4 mm. According to the invention, the particle sizes of the coarse aggregate and the fine aggregate of the waste granite are controlled within the above range, so that the waste granite aggregate has good gradation, higher compactness is obtained, and the mechanical property and durability of the cement-based recycled concrete are improved.
The raw materials for preparing the cement-based recycled concrete further comprise 45.57-65.1 parts of river sand, preferably 50-62 parts of river sand, and more preferably 55-60 parts of river sand, wherein the mass part of the cement is 16.2-34.2 parts of cement. According to the invention, by controlling the addition amount of the river sand within the range, the mechanical property and durability of the cement-based recycled concrete can be effectively improved.
The source of the river sand is not particularly limited, and the river sand which is generally sold in the market or naturally mined in the field can be adopted.
In the present invention, the river sand preferably has a particle size of < 5 mm. According to the invention, the particle size of the river sand is controlled within the range, and the river sand is added as natural fine aggregate, so that the compactness of the concrete is improved.
The raw materials for preparing the cement-based recycled concrete further comprise 0-120.9 parts of crushed stone, preferably 60.45-100 parts of crushed stone, and more preferably 80-90 parts of cement by mass part of 16.2-34.2 parts of cement. According to the invention, the addition amount of the broken stone is controlled within the range, so that the broken stone and river sand can be cooperatively matched, and the cement-based recycled concrete has good mechanical properties and durability under the condition of ensuring that the waste granite has a high recycling rate.
In the present invention, the crushed stone is preferably natural crushed stone, more preferably pebbles.
In the invention, the particle size of the crushed stone is preferably 5-9.5 mm. According to the invention, the particle size of the broken stone is controlled within the range, namely the broken stone is added as a natural coarse aggregate, so that the mechanical property and the service performance of the cement-based recycled concrete can be better improved by cooperating with river sand.
The cement-based recycled concrete provided by the invention further comprises 18-22.5 parts of water, preferably 19-21 parts of water, and more preferably 20-20.5 parts of water, based on 16.2-34.2 parts of cement by mass. According to the invention, by controlling the addition amount of water within the range, the proper viscosity of a gelling system formed after mixing can be ensured, and the aggregates can be bonded together sufficiently, so that the mechanical property and the durability of the cement-based recycled concrete can be effectively improved.
The raw materials for preparing the cement-based recycled concrete further comprise 0.3-0.4 part of a water reducing agent, preferably 0.32-0.38 part of the water reducing agent, and more preferably 0.35-0.36 part of the water reducing agent in terms of 16.2-34.2 parts of cement by mass. In the invention, the water reducing rate of the water reducing agent is preferably 16-20%, and more preferably 17-19%. According to the invention, by controlling the addition amount and the water reducing rate of the water reducing agent within the above range, the uniformity of a mixing system can be ensured under the condition of effectively reducing the addition of water, the volume expansion caused by hydration of silica fume due to the addition of more water is avoided, and the cracking problem caused by the evaporation of a large amount of water during curing and drying is reduced.
The cement-based recycled concrete provided by the invention uses the waste granite as the stone powder and can also be used as the aggregate to replace part of cement, river sand and broken stone, so that the recycling rate of the waste granite is further improved and the resource recycling is realized while the performance of the cement-based recycled concrete is ensured to meet the use requirement.
The preparation method and the curing method of the cement-based recycled concrete have no special requirements, and the preparation and the curing can be carried out by adopting the site construction standard well known in the field.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The cement-based recycled concrete prepared in the embodiment comprises the following raw materials:
21.6 parts of P.O 42.5 Portland cement, 11.52 parts of waste granite powder with the particle size of 0.1-75 mu m, 2.88 parts of silica fume with the particle size of 0.1-0.3 mu m, 45.57 parts of river sand with the particle size of 1-5 mm, 60.45 parts of crushed stone with the particle size of 5-10 mm, 18 parts of water and 0.335 part of water reducing agent;
wherein the mass ratio of the waste granite powder to the silica fume is 4:1, the water reducing rate of the water reducing agent is 18 percent, and the silica fume consists of SiO2 93.24％，Al2O3 3.16％，Fe2O31.61%, CaO 1.42% and MgO 0.57%.
Example 2
The cement-based recycled concrete prepared in the embodiment comprises the following raw materials:
21.6 parts of P.O 42.5 Portland cement, 11.52 parts of waste granite powder with the particle size of 0.1-75 mu m, 2.88 parts of silica fume with the particle size of 0.1-0.3 mu m, 79.98 parts of waste granite aggregate, 45.57 parts of river sand with the particle size of 1-5 mm, 60.45 parts of crushed stone with the particle size of 5-10 mm, 18 parts of water and 0.335 part of water reducing agent;
the mass ratio of the waste granite stone powder to the silica fume is 4:1, the waste granite aggregate is a waste granite coarse aggregate and a waste granite fine aggregate, the particle size of the waste granite coarse aggregate is 5-9.5 mm, the particle size of the waste granite fine aggregate is 3-4.9 mm, and the mass ratio of the waste granite coarse aggregate to the waste granite fine aggregate is 3.10: 1, the water reducing rate of the water reducing agent is 18 percent, and the composition of the silica fume is SiO2 93.24％，Al2O3 3.16％，Fe2O31.61%, CaO 1.42% and MgO 0.57%.
Example 3
The mass ratio of the waste granite coarse aggregate to the waste granite fine aggregate in the example 2 is replaced by 6.19: 1, replacing the mass parts of the crushed stones with 0, and the other technical characteristics are the same as those of the embodiment 2.
Comparative example 1
The cement-based concrete prepared by the comparative example consists of the following raw materials:
21.6 parts of P.O 42.5 Portland cement, 65.1 parts of river sand with the diameter of 1-5 mm, 12.09 parts of crushed stone with the diameter of 5-10 mm, 18 parts of water and 0.335 part of water reducing agent; wherein the water reducing rate of the water reducing agent is 18 percent.
And (3) performance detection: the cement-based recycled concrete prepared in the embodiments 1-3 and the cement-based concrete prepared in the comparative example 1 are mixed according to a conventional preparation method, and the curing method comprises the steps of placing a formed test block in a room with the temperature of (20 +/-2) DEG C, removing a mold after 1d, moving to a standard curing room with the temperature of (20 +/-2) DEG C and the humidity of more than 95% for curing for 3d, 7d and 28d respectively.
1. Compressive strength detection
The detection standard is used for measuring the compressive strength of a concrete cube test block according to GBT50081-2019 'test method standard for physical and mechanical properties of concrete', the cement-based recycled concrete prepared in examples 1-3 of the invention and the cement-based concrete prepared in comparative example 1 are respectively four groups of test pieces, each group comprises 3 non-standard test pieces, the size of each test piece is 100mm multiplied by 100mm, and therefore, the conversion coefficient is multiplied by 0.95 during calculation; the pressing machine used for detection is a WAW-600D microcomputer control electro-hydraulic servo universal testing machine, the maximum pressure is 3000KN, the precision of the testing machine is less than or equal to +/-1%, and the upper pressing plate and the lower pressing plate of the testing machine are larger than the size of a test block and meet the technical requirements. When in test, the test block is uniformly and continuously loaded at the speed of 0.3 MPa/s-0.5 MPa/s, the accelerator is not adjusted when the test block is about to be damaged until the test block is completely damaged, the damage peak value is recorded, the compressive strength of the test block is obtained by calculating according to the following formula 1.1, each group of calculation results are respectively averaged, and the result is shown in the table 1;
in formula 1.1: f. ofcc-the compressive strength (MPa) of the test piece, the deviation of the calculation results must not exceed 0.1 MPa; f, breaking load (N) of the test piece; a-test piece bearing area (mm)2)。
2. Flexural strength test
The flexural strength of a concrete cube test block is measured according to GBT50081-2019 (Standard for testing physical and mechanical properties of concrete) by a detection standard, the flexural strength of the cement concrete adopts a standard beam type test piece, the cement-based recycled concrete prepared in examples 1-3 of the invention and the cement-based concrete prepared in comparative example 1 are respectively four groups of test samples, each group is 3, and the size of each test sample is 100mm multiplied by 400 mm; the detection equipment is a WAW-600D microcomputer control electro-hydraulic servo universal testing machine, the upper limit of the measuring range is 300KN, the loading speed of the pressing machine is adjusted in a manual adjustment mode during testing, the loading speed is guaranteed to be 0.3-0.5 MPa/s, when a test piece is approximately damaged, the accelerator of the testing machine is not adjusted any more until the test piece is completely damaged, the damage load and the lower edge fracture position of the test piece are recorded, the anti-fracture strength value is calculated according to a formula 1.2, each group of calculation results are respectively averaged, and the results are shown in a table 1;
in formula 1.2: f. offConcrete flexural strength (MPa), the calculation result should be accurate to 0.1 MPa; f, breaking load (N) of the test piece; l-span (mm) between supports; b-the width of the section of the specimen (mm); h-the height (mm) of the section of the test piece.
3. Durability testing
The durability test adopts a carbonization test, the test is carried out according to the requirements of GB/T50082-2009 Standard test method for Long-term performance and durability of common concrete, the anti-carbonization performance test is carried out by using prism concrete test blocks, the cement-based recycled concrete prepared in the embodiments 1-3 of the invention and the cement-based concrete prepared in the comparative example 1 are respectively four groups of test samples, each group is 3, and the size of the test samples is 100mm multiplied by 400 mm. Placing the test block maintained for 28 days into a 60 ℃ baking oven for constant temperature for 48h before carbonization test, taking one opposite side surface on the test block after drying, drawing parallel lines at intervals of 10mm by using a pencil along the length direction to be used as detection points, and using paraffin wax on the other side surfacesAnd (5) sealing. Placing the test block in CO2Accelerating carbonization in a carbonization test box with the concentration of (20 +/-3)%, the humidity of (70 +/-5)%, and the temperature of (20 +/-2) ° C, respectively taking out test pieces when the carbonization reaches 3d, 7d, 14d and 28d, and determining the carbonization depth by breaking; breaking the mold from one end by a splitting method; the thickness of each cutting is half of the width of the test piece, the cut surface of the test piece after the cutting is sealed by paraffin, and the test piece is put into a box to be continuously carbonized until the next test period; then, the cut-off test piece portion should be brushed off the powder remaining on the cross section, and then a phenolphthalein alcohol solution (alcohol solution containing 20% distilled water) with a concentration of 1% should be sprayed; after about 30 seconds, measuring the carbonization depth of each point by using a steel plate ruler according to one measuring point of every 10mm marked originally; when the coarse aggregate particles are just embedded in the carbonization boundary line at the measuring point, the arithmetic mean value of the carbonization depth at two sides of the particles is taken as the depth value of the point, and the results of the carbonization depth test under different accelerated carbonization ages are shown in table 1.
TABLE 1 mechanical Properties and durability results for the concretes prepared in inventive examples 1-3 and comparative example 1
As can be seen from Table 1, with the increase of the curing age, the cement-based recycled concrete of examples 1 to 3 has basically the same increasing and decreasing trend of the compressive strength and the flexural strength of the cement-based recycled concrete at different blending ratios in different ages, and shows the increasing and decreasing trend; in example 1, the compressive strength of the concrete is increased by 1.38MPa, 1.78MPa and 1.03MPa compared with that of comparative example 1 in the same age, namely, the compressive strength is increased by about 5.76%, 5.54% and 2.53% respectively, which indicates that the early strength of the cement-based recycled concrete prepared by the invention is superior to that of the common cement-based concrete, wherein the early strength is most obvious in 3d, and indicates that the synergistic work of the waste granite powder and the silica fume is beneficial to the improvement of the early strength of the cement-based concrete. In the embodiments 2 to 3, waste granite is used as coarse and fine aggregates, the compressive strength and the folding resistance of the waste granite are reduced to some extent, the reduction is caused by the fact that the gradation of the waste granite coarse and fine aggregates cannot meet the gradation of gravel river sand, but the mechanical property and the durability of the prepared cement-based recycled concrete can meet the use requirements of C40 common concrete, and the high recycling rate of the waste granite is realized.
As can be seen from table 1, the carbonization depth of the cement-based recycled concrete in the embodiments 1 to 3 deepens along with the increase of the carbonization age, but the cement-based recycled concrete in the embodiments 1 to 3 improves the later-stage carbonization resistance of the cement-based concrete due to the addition of the waste granite powder and the silica fume, but the carbonization resistance is reduced along with the replacement of the coarse and fine aggregates, but the basic use requirements can still be met, and the high recycling rate of the waste granite is realized.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. The cement-based recycled concrete is prepared from the following raw materials in parts by weight: 16.2-34.2 parts of cement, 7.2-21.6 parts of waste granite powder, 2.88-3.6 parts of silica fume, 45.57-65.1 parts of river sand, 0-120.9 parts of broken stone, 18-22.5 parts of water and 0.3-0.4 part of water reducing agent; the mass ratio of the waste granite powder to the silica fume is (2-6) to 1.
2. The cement-based recycled concrete according to claim 1, wherein the raw materials for preparing the cement-based recycled concrete further comprise 79.98-140.43 parts by weight of waste granite aggregate.
3. The cement-based recycled concrete according to claim 1 or 2, wherein the particle size of the waste granite powder is 1 to 200 μm.
4. The cement-based recycled concrete according to claim 1 or 2, wherein the silica fume comprises, in weight percent:SiO292.5～94.5％，Al2O33.06～4.26％，Fe2O31.51-2.71%, CaO1.32-1.52% and MgO0.47-0.67%.
5. Cement-based recycled concrete according to claim 1 or 2, characterized in that said silica fume has a particle size < 0.3 μm.
6. The cement-based recycled concrete of claim 2, wherein said waste granite aggregate comprises a waste granite coarse aggregate and a waste granite fine aggregate; the mass ratio of the waste granite coarse aggregate to the waste granite fine aggregate is (3-6.2): 1.
7. the cement-based recycled concrete according to claim 6, wherein the particle size of the waste granite coarse aggregate is 5-9.5 mm; the particle size of the waste granite fine aggregate is 3-4.9 mm.
8. Cement-based recycled concrete according to claim 1 or 2, characterized in that said river sand has a particle size < 5 mm.
9. The cement-based recycled concrete according to claim 1 or 2, wherein the crushed stone has a particle size of 5 to 9.5 mm.
10. The cement-based recycled concrete according to claim 1 or 2, wherein the water reducing agent has a water reducing rate of 16 to 20%.
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| CN202110531981.2A CN113248202A (en) | 2021-05-17 | 2021-05-17 | Cement-based recycled concrete |
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| CN202110531981.2A CN113248202A (en) | 2021-05-17 | 2021-05-17 | Cement-based recycled concrete |
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