CN116735371A - Test method for strength ratio of construction sand and application thereof - Google Patents

Test method for strength ratio of construction sand and application thereof Download PDF

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Publication number
CN116735371A
CN116735371A CN202310202025.9A CN202310202025A CN116735371A CN 116735371 A CN116735371 A CN 116735371A CN 202310202025 A CN202310202025 A CN 202310202025A CN 116735371 A CN116735371 A CN 116735371A
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China
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sand
strength
test
testing
strength ratio
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张大康
邝文辉
符元姣
陈伟业
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Guangdong Zhidao Advanced Civil Engineering Materials Technology Research Co ltd
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Guangdong Zhidao Advanced Civil Engineering Materials Technology Research Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/20—Investigating strength properties of solid materials by application of mechanical stress by applying steady bending forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/36—Embedding or analogous mounting of samples
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/36—Embedding or analogous mounting of samples
    • G01N2001/366—Moulds; Demoulding
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0001—Type of application of the stress
    • G01N2203/0003—Steady
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0019—Compressive
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0023—Bending
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/006—Crack, flaws, fracture or rupture
    • G01N2203/0067—Fracture or rupture
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/067—Parameter measured for estimating the property
    • G01N2203/0676—Force, weight, load, energy, speed or acceleration

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Sampling And Sample Adjustment (AREA)

Abstract

The invention discloses a test method of sand strength ratio for construction, which comprises the following steps: (1) screening and setting reference sand; (2) treating the produced sand; (3) Mixing the standard sand or the production sand with cement and an additive to prepare cement mortar, and testing the mortar strength; (4) And calculating the strength ratio of the standard sand to the cement mortar prepared by the produced sand. According to the invention, the strength ratio is calculated by adopting the compressive strength of the cement mortar in the production sand test and the compressive strength value of the cement mortar in the standard sand test, so that the strength of the mortar or the concrete is represented, the original test method for indirectly representing the strength of the mortar or the concrete by adopting the crushing value is replaced, the surface influence of sand raw materials can be removed, and the accuracy of testing the strength of the mortar or the concrete is improved. The method for testing the difference between the characterization produced sand and the reference sand is more direct and accurate, and the accuracy of the strength characterization of the construction sand is further improved.

Description

Test method for strength ratio of construction sand and application thereof
Technical Field
The invention relates to a test method for sand strength ratio for construction, relates to G01N, and in particular relates to testing or analyzing materials by means of measuring chemical or physical properties of the materials.
Background
The prior sand for construction in the national standard adopts a crushing value to represent the parent rock strength of mortar, but the crushing value is not a single influencing factor of the mortar strength, when the mortar strength is represented, the surface of the used gravel can be weathered or semi-weathered, the weathered gravel has little influence on the crushing value, but the overall strength of the mortar can be influenced, and the compressive strength result of the mortar is represented inaccurately by adopting the single crushing value. The strength of the mortar is also related to the elastic modulus and the poisson ratio between various aggregates in the mortar, and the matching relationship of the elastic modulus and the poisson ratio between the aggregates has obvious influence on the strength of the mortar, but the relationship of the strength cannot be simply represented by the crushing value.
The Chinese patent No. 202111333760.0 discloses a method for calculating the compressive strength of pervious concrete, which comprises the steps of preparing a concrete test piece, testing the apparent density of the concrete test piece and the corresponding compressive strength of 28d age, and then carrying out linear regression analysis by taking the apparent density as a horizontal axis and the compressive strength of 28d age as a vertical axis to obtain a relation between the compressive strength of 28d age and the apparent density. The influence of the size effect generated by the non-uniform test piece on the compressive strength can be avoided, whether the ready-mixed concrete meets the requirement can be predicted by substituting the apparent density obtained by the test into the fitting equation, but the concrete strength is represented by the apparent density, and the accuracy of the method is not high. Chinese patent No. 201810246655.5 discloses a method for testing mechanical properties of 3D printing building mortar, which comprises the steps of cutting a sample from a 3D printing member reaching a testing age, detecting interlayer joint strength, flexural strength, compressive strength and various mechanical properties of a printing layer of the 3D printing building mortar member by using the sample to obtain mechanical property parameters of the 3D printing building mortar, and providing theoretical basis for improving the mechanical properties of the 3D printing building material when the method is applied to actual production, wherein the technical equipment requirement of 3D printing is higher, and the cost is higher when the method is applied to actual production at present.
Disclosure of Invention
In order to improve the accuracy of the strength characterization of mortar, and to enable the strength characterization to be closer to the numerical value used in actual production, the first aspect of the invention provides a test method of the strength ratio of the sand for construction, which comprises the following steps:
(1) Screening and setting reference sand;
(2) Treating and producing sand;
(3) Weighing the raw materials according to the proportion, placing the raw materials into a mortar stirrer for stirring, preparing cement mortar, preparing a test piece, curing, and testing the mortar strength;
(4) And calculating the strength ratio of the standard sand to the cement mortar prepared by the produced sand.
As a preferred embodiment, the reference sand is round siliceous sand with a silicon dioxide content of not less than 98%.
As a preferred embodiment, the moisture content of the reference sand is less than 0.2% after drying for 1-3 hours at 105-110 ℃.
As a preferred embodiment, the reference sand is ISO standard sand and the particle distribution is shown in table 1.
TABLE 1
As a preferred embodiment, the treatment method for producing sand in step 2 specifically includes the following steps: spreading the produced sand in a flat plate, wherein the thickness of the sand is less than or equal to 20mm, drying at 100-110 ℃ for 3-5h, and cooling to 18-22 ℃ at room temperature.
As a preferred embodiment, the treatment method for producing sand in step 2 specifically includes the following steps: taking produced sand, spreading the produced sand in a flat plate, wherein the thickness of the sand is less than or equal to 20mm, and drying the produced sand at 105 ℃ for 4 hours.
As a preferred embodiment, the particle size of the produced sand is 0.075mm to 2.36mm.
As a preferred embodiment, the cement has a strength grade selected from one or a combination of several of 32.5R, 42.5R, 52.5R, 62.5R, 32.5, 42.5, 52.5, 62.5.
The cement meets the specifications of GB 175.
As a preferred embodiment, when the test of the strength ratio of the sand for construction is performed, the water is drinking water. The additive is water-reducing polycarboxylate water reducer.
As a preferred embodiment, the preparation method of the cement gum sand in the step 3 specifically comprises the following steps: 450 g+ -2 g cement, 1350 g+ -5 g sand, 225 g+ -1 g water, or 225 ml+ -1 ml admixture is weighed (admixture amount is adjusted so that the tested gel sand fluidity is 180-200 mm). The mixing pot and the mixing blade are wiped by wet rag (cleaned, soaked and wrung) until the surface of the mixing pot and the mixing blade is wet and has no water stain. Adding water and an additive into a cement mortar stirring pot, adding cement, fixing the pot on a fixing frame, and lifting to a working position; immediately, the machine was started, and after stirring at a low speed for 30 s.+ -. 1s, sand was added uniformly while starting at the second 30 s.+ -. 1s. The stirrer is regulated to be at a high speed and stirred for 30 s+/-1 s; stopping stirring for 90s, and putting the stirring pot down within 15 s+/-1 s of the start of stopping stirring, and scraping the rubber sand on the blades, the pot wall and the pot bottom into the pot by using a scraper; stirring was continued at high speed for 60 s.+ -.1 s.
As a preferred embodiment, the molding method of the cement mortar in the step 3 specifically comprises the following steps: and (5) immediately molding after the preparation of the rubber sand. The test mould and the mould sleeve with the sizes of 40mm multiplied by 160mm are fixed on a compaction table, the glue sand on the wall of the pot is cleaned into the pot by a spoon, the sand is turned over to be more uniform, and the glue sand is loaded into the test mould in two layers. When the first layer is installed, about 300g of rubber sand is placed in each groove, firstly, a material spoon is used for scratching along the length direction of a test die, then a large distributing device is vertically arranged at the top of a die sleeve and used for distributing a material layer back and forth once along each die groove, and then the material layer is compacted for 60 times. And filling the second layer of rubber sand, and scraping the rubber sand along the length direction of the test die by using a spoon to fully fill the die cavity, wherein the rubber sand cannot be contacted with the compacted rubber sand, and then flattening the rubber sand by using a small distributing device and compacting for 60 times. A piece of cotton yarn cloth which is slightly bigger than the die sleeve in size can be covered on the die sleeve after being wet by water in real time to prevent the glue sand from splashing in real time.
The die sleeve is removed, the test die is taken down from the compaction table, a metal straight edge ruler is used for supporting one end of the top of the test die at an angle of approximately 90 degrees (but slightly inclined towards the strickling direction), then the test die is slowly moved towards the other end along the length direction of the test die in a transverse sawing action, and the rubber sand exceeding the test die part is scraped. The sawing action and the angle of the ruler depend on the thickness degree of the rubber sand, and thicker rubber sand needs to be sawn for a plurality of times, and the sawing action is slow to prevent the rubber sand from being pulled to be compacted. The glue sand at the top of the test mould end plate is wiped clean by a wrung wet towel, and then the surface of the test body is smoothed by the same straight edge ruler at an almost horizontal angle. The number of trowelling is as small as possible, and the total number of trowelling should not exceed 3. Finally, the rubber sand around the test mold is erased.
As a preferred embodiment, the demolding method of the cement mortar in the step 3 specifically comprises the following steps: a rubber hammer or a stripper for stripping. For 24h age, demolding should be performed within 20min before the breaking test. For the age of more than 24 hours, demolding is carried out between 20 and 24 hours after molding. If the curing is carried out for 24 hours, the curing may be delayed until the curing is carried out after 24 hours, when the strength is impaired by the curing, but the curing is described in the test report. The demolded test bodies were determined as 24h age tests (or other tests performed directly without running water) and wet cloth coverage was applied until the time of the test. It is recommended to weigh the total amount of test body in each model.
As a preferred embodiment, the curing method of the cement mortar in the step 3 specifically comprises the following steps: a glass plate is covered on the test mould, and a steel plate with similar size or a plate made of a material which is not water-permeable and has no reaction with cement can be used. The cover plate is not contacted with cement mortar, and the distance between the cover plate and the test die is controlled to be 2-3 mm. For safety, the glass plate should be edged. The marked test chess is put into a curing room or a horizontal rack of a wet box for curing, and wet air can be contacted with each side of the test chess. The test mould should not be placed on other test moulds during curing. And taking out the mold after curing until the specified mold release time.
And (3) immediately horizontally or vertically placing the marked test body in water at the temperature of 20 ℃ and the temperature of 1 ℃ for maintenance, wherein the scraping plane is upward when the test body is horizontally placed. The test body is placed on the grate which is not easy to decay, and a certain distance is kept between the test body and the grate, so that the water contacts with six surfaces of the test body. The interval between the test bodies or the water depth on the upper surface of the test bodies during maintenance should not be less than 5mm. (it is not preferable to use a non-preserved grate). Each curing pool only cures cement test bodies of the same type. The maintenance pool (or container) is initially filled with tap water, and then water is added at any time to maintain a proper level. During curing, no more than 50% of the water may be replaced.
As a preferred embodiment, the method for measuring the strength of the cement mortar in the step 3 specifically comprises the following steps: any test bodies to the age should be removed from the water 15min before the test (breaking) except for those that were 24h old or delayed to 48h demolded. The surface deposits of the test bodies were wiped off and covered with a wet cloth until the test was completed. The age of the test body is calculated from the time of starting the test by adding water into cement and stirring. The different age intensity tests were performed during the following times:
soil for 24 hours for 15min;
72h±45min；
28d±8h。
the flexural strength was measured by a flexural strength tester. One side of the test body was placed on the support cylinder of the tester, the long axis of the test body was perpendicular to the support cylinder, and a load was uniformly applied to the opposite side of the prism by the loading cylinder at a rate of 50N/s 10N/s until broken. The two half prisms are kept in a wet state until the compression test, the flexural strength is calculated according to the formula (1),
R f ＝1.5F f L/b 3 ……(1)
wherein:
R f -flexural strength in megapascals (MPa);
F f -the load applied to the middle of the prism at break, in newtons (N);
l-distance between support cylinders in millimeters (mm);
b-side length of square section of prism in millimeters (mm).
Calculation and representation of flexural strength results: the average of the results of a set of three prism bending resistance was used as the test result. When one of the three intensity values exceeds +/-10% of the average value, taking the average value after eliminating as an flexural strength test result; when two of the three intensity values exceeded the average value.+ -. 10%, then the remaining one was taken as the flexural strength result. The single flexural strength result is accurate to 0.lMPa, and the arithmetic average value is accurate to 0.1MPa.
After the flexural strength test is completed, two half test pieces are taken out and subjected to a compressive strength test. Compressive strength tests were performed on the sides of the half prisms. The difference between the center of the half prism and the compression center of the pressing plate of the pressing machine is within +/-0.5 mm, and the part of the prism exposed outside the pressing plate is about 10mm. The whole loading process is uniformly loaded at the speed of 2400N/s and 200N/s until the loading is broken. The compressive strength is calculated according to the formula (2), and the compression area is 1600mm 2 :
R c ＝F c /A……(2)
R c -compressive strength in megapascals (MPa);
F c -maximum load at failure in newtons (N);
a-the area under pressure, in square millimeters (mm).
Calculation and representation of compressive strength results: the average of six compressive strength measurements obtained on a set of three prisms was used as the test result. When one of the six measured values exceeds ±10% of the six average values, this result is rejected, and the remaining five average values are taken as results. When there are more than + -10% of the five measured values from their average, this set of results is negated. When two or more of the six measurements are simultaneously over + -10% of the average, then the set of results is voided. The single compressive strength results were accurate to 0.lMPa, and the arithmetic mean was accurate to 0.1MPa.
As a preferred embodiment, the water consumption in the step 3 is constant at 225g, and the admixture dosage is adjusted. When a liquid water reducer is used, the solid content of the water reducer is converted into the solid powder content, and the water content of the liquid water reducer is subtracted from the water addition amount.
As a preferred embodiment, the fluidity of the cement mortar prepared in the step 3 is 180-200mm. The concrete measuring method of the cement mortar fluidity comprises the following steps: if the jump table is not used in 24 hours, the jump table is firstly jumped for 25 times in a period. The test mould is placed in the center of the table-board and covered by wet cotton cloth. Rapidly filling the mixed glue sand into a test die in two layers, wherein the first layer is arranged at the position about two thirds of the height of the truncated cone circular die, and is respectively scratched 5 times in two directions perpendicular to each other by a knife, and is uniformly rammed 15 times from the edge to the center by a rammer; then, the second layer of rubber sand is filled up to about 20mm higher than the truncated cone circular die, and is scratched 5 times in two directions perpendicular to each other by a small knife, and then is uniformly tamped 10 times from edge to center by a tamping rod. The glue sand after tamping should be slightly higher than the test mould. The tamping depth is that the first layer is tamped to half the height of the rubber sand, and the second layer is not tamped to exceed the surface of the tamped bottom layer. When the glue sand is filled and the tamping is carried out, the mould is tested by hand stabilization, and the mould is not required to be moved.
And after the tamping is finished, the die sleeve is taken down, the knife is inclined, the rubber sand higher than the truncated cone circular die is wiped off twice from the middle to the edge at a near horizontal angle, and the rubber sand falling on the tabletop is wiped off. The truncated cone circular mould is lifted slightly vertically upwards. The jump table is immediately started, and 25 jumps are completed within 25s + -1 s at a frequency of once per second. From the beginning of the water addition of the gum sand to the end of the measurement of the diffusion diameter, the completion should be within 6 min. And after the jump is finished, measuring diameters of the bottom surface of the cement mortar in two directions perpendicular to each other by using a caliper, calculating an average value, taking an integer, wherein the unit is millimeter, and the average value is the cement mortar fluidity of the water quantity.
As a preferred embodiment, the test cement is stored in an airtight container that is non-reactive with the cement from sampling to holding for more than 24 hours.
As a preferred embodiment, the temperature of the cement mortar sample forming laboratory should be kept at 20 ℃ and 2 ℃ and the relative humidity should be not lower than 50%; the temperature of a curing box or a fog chamber for curing the cement mortar test body with the mold is kept at 20 ℃ and 1 ℃ with the relative humidity not lower than 90%; the temperature of the cement mortar sample curing pool water is within 20+/-1 ℃; the water temperature of the accelerating curing box is in the range of 90 ℃ and 2 ℃; the laboratory air temperature and relative humidity and the maintenance pool water temperature are recorded at least once a day during operation; the temperature and relative humidity of the curing box or fog chamber are recorded at least once every 4 hours. The number of recordings can be reduced to twice a day recording in the case of automatic control.
As a preferred embodiment, the cement mortar prepared in the step 3 is required to be subjected to standard curing and accelerated curing, and then subjected to compressive strength test, wherein the standard curing is carried out for 3d and 28d.
As a preferred embodiment, the concrete method for accelerating maintenance is as follows: mixing the prepared cement mortar, shaping, standing in a cement mortar sample curing box, curing for 23 h+/-15 min, and demoulding. And immediately placing the demoulded test piece into an accelerated curing box. Tap water is injected into the accelerated curing box before the accelerated curing box is placed into a test piece, the water level is preferably 70 mm-100 mm, the water level is 20mm plus or minus 2mm higher than a heat source (an electric heating tube), and the water level is not less than 50mm away from the lower surface of the test piece frame. The water temperature in the accelerating curing box before the test piece is put into the test piece should be 20-35 ℃. Starting the power supply of the accelerating curing box, and heating the water in the accelerating curing box to 90+/-2 ℃ within 50-70 min, and keeping the temperature. Starting to start the power supply of the accelerated curing box for timing, wherein the curing time is 6 hours plus or minus 5 minutes, and the test water is not added in the middle in the whole test process. Taking out the test piece, and standing for 2 h+/-10 min at 20+/-2 ℃. And then, carrying out a cement mortar compressive strength test to measure the compressive strength of the accelerated curing cement mortar. The acceleration test period should be 31h + -15 min.
The method adopts the cement mortar compressive strength of the production sand test and the cement mortar compressive strength of the standard sand test to calculate the strength ratio, is used for representing the strength of mortar or concrete, replaces the original test method for indirectly representing the strength of concrete by adopting the crushing value, can remove the surface influence of sand and improves the accuracy of testing the strength of concrete. The possible reason is that the fine aggregate for preparing concrete contains the impurities such as shells, wood chips, clay and the like, so that the strength of the concrete is reduced, but the crushing value is not greatly influenced when the crushing value is calculated due to the small fineness of the fine aggregate, and the testing accuracy of the strength of the prepared concrete is influenced by the existence of the impurities.
As a preferred embodiment, the standard curing strength ratio has a calculation formula: strength ratio = (cement mortar compressive strength of production sand standard maintenance test/cement mortar compressive strength of standard maintenance test of standard sand) ×100%.
As a preferred embodiment, the calculation formula of the accelerated curing strength ratio is as follows: strength ratio= (cement mortar compressive strength of production sand accelerated maintenance test/cement mortar compressive strength of standard sand accelerated maintenance test) ×100%.
The second aspect of the invention provides application of a test method for the strength ratio of the sand for construction, which is applied to large-scale mortar or concrete production strength detection.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the testing method of the sand strength ratio for construction, the strength ratio is directly calculated by adopting the compressive strength of cement mortar in the sand production test and the compressive strength value of cement mortar in the standard sand test, so that the strength of mortar or concrete is represented, the original testing method of indirectly representing the strength of concrete by adopting the crushing value is replaced, the surface influence of sand raw materials can be removed, and the accuracy of testing the strength of concrete is improved.
(2) According to the testing method of the sand strength ratio for construction, disclosed by the invention, the formula calculation of (the compressive strength of cement mortar in the sand production test/the compressive strength of cement mortar in the standard sand test) multiplied by 100% is adopted, so that the testing method for characterizing the difference between the produced sand and the standard sand is more direct and accurate, and the strength characterization accuracy of the sand for construction is further improved.
(3) The test method of the strength ratio of the sand for construction has good practicability, can be widely applied to the strength ratio test of various sand, and is simple and efficient.
Detailed Description
Example 1
The test method of the sand strength ratio for construction is characterized by comprising the following steps of:
(1) Screening and setting reference sand;
(2) Treating and producing sand;
(3) Weighing the raw materials according to the proportion, placing the raw materials into a mortar stirrer for stirring, preparing cement mortar, preparing a test piece, curing, and testing the mortar strength;
(4) And calculating the strength ratio of the standard sand to the cement mortar prepared by the produced sand.
The standard sand is round siliceous sand with the silicon dioxide content of more than or equal to 98 percent, the moisture content of the standard sand is lower than 0.2 percent after being dried for 2 hours at 110 ℃, and the particle distribution is shown in table 1.
TABLE 1
The treatment method for producing sand in the step 2 specifically comprises the following steps: taking produced sand, spreading the produced sand in a flat plate, wherein the thickness of the sand is less than or equal to 20mm, and drying the produced sand at 105 ℃ for 4 hours. The grain diameter of the produced sand is 0.075mm-2.36mm.
The produced sand is purchased from Guangdong pearl sea desalinated sea sand and Guangdong English machine-made sand.
The cement is cement meeting the specification of GB175, the strength grade is 42.5R, and the variety is courser P.O42.5R;
the water is drinking water, the water reducer is liquid non-collapse-protection water-reducing type polycarboxylate water reducer mother liquor (the non-collapse-protection water-reducing type polycarboxylate water reducer mother liquor is from Jie New Material group Co., ltd.) and is diluted to the solid content of 10% by adding water.
The standard sand is standard sand conforming to the specification of GB/T17671, and the sand is Xiamen ISO standard sand.
The preparation method of the cement gum sand in the step 3 specifically comprises the following steps: the cement dosage is weighed to be 450g, the sand is 1350g, the water is 225g, and the admixture is proper (the admixture dosage is adjusted so that the tested sand flow is 180-200 mm). Wiping the stirring pot and the stirring blade by wet rags (cleaning, soaking and wringing) until the surfaces of the stirring pot and the stirring blade are wet and have no water stain, adding water and an additive into the cement mortar stirring pot, adding cement, fixing the pot on a fixing frame, and lifting to a working position; immediately, the machine was started, after stirring at low speed for 30s, sand was added uniformly while starting at the second 30 s. The stirrer is regulated to be at a high speed and stirred for 30 seconds; stopping stirring for 90s, and in 15s from the start of stopping stirring, putting the stirring pot down, and scraping the rubber sand on the blades, the pot wall and the pot bottom into the pot by using a scraper; stirring was continued at high speed for a further 60s.
The cement mortar molding method in the step 3 specifically comprises the following steps: and (5) immediately molding after the preparation of the rubber sand. The test mould and the mould sleeve with the sizes of 40mm multiplied by 160mm are fixed on a compaction table, the glue sand on the wall of the pot is cleaned into the pot by a spoon, the sand is turned over to be more uniform, and the glue sand is loaded into the test mould in two layers. When the first layer is installed, about 300g of rubber sand is placed in each groove, firstly, a material spoon is used for scratching along the length direction of a test die, then a large distributing device is vertically arranged at the top of a die sleeve and used for distributing a material layer back and forth once along each die groove, and then the material layer is compacted for 60 times. And filling the second layer of rubber sand, scraping the rubber sand along the length direction of the test die by using a spoon to fully fill the die cavity, distributing the rubber sand which is vibrated and is not contacted, and vibrating for 60 times by using a small distributing device. A piece of cotton yarn cloth which is slightly bigger than the die sleeve in size is covered on the die sleeve after being wet by water in real time.
The die sleeve is removed, the test die is taken down from the compaction table, a metal straight edge ruler is used for supporting one end of the top of the test die at an angle of approximately 90 degrees (but slightly inclined towards the strickling direction), then the test die is slowly moved towards the other end along the length direction of the test die in a transverse sawing action, and the rubber sand exceeding the test die part is scraped. The glue sand at the top of the test mould end plate is wiped clean by a wrung wet towel, and then the surface of the test body is smoothed by the same straight edge ruler at an almost horizontal angle. Finally, the rubber sand around the test mold is erased.
The demolding method of the cement mortar in the step 3 specifically comprises the following steps: the mold was removed by tapping with a rubber hammer and then mold was removed 24 hours after molding.
The curing method of the cement mortar in the step 3 specifically comprises the following steps: a glass plate was covered on the test mold. The cover plate is not contacted with cement mortar, and the distance between the cover plate and the test die is 3mm. Immediately placing the marked test mould into a curing chamber, wherein wet air can be contacted with each side of the test mould. And taking out the mold after curing until the specified mold release time.
And (3) immediately horizontally placing the marked test body in water at 21 ℃ for maintenance, and scraping the plane upwards when the test body is horizontally placed. The test body is placed on the grate which is not easy to decay, and a certain distance is kept between the test body and the grate, so that the water contacts with six surfaces of the test body. The interval between the test bodies or the water depth of the upper surface of the test bodies during maintenance is 5mm.
The method for measuring the strength of the cement mortar in the step 3 specifically comprises the following steps: the test bodies to the age were removed from the water 15min before the test. The surface deposits of the test bodies were wiped off and covered with a wet cloth until the test was completed. The age of the test body is calculated from the time of starting the test by adding water into cement and stirring. The different age intensity tests were performed during the following times:
soil for 24 hours for 15min;
72h±45min；
28d±8h。
the flexural strength was measured by a flexural strength tester. One side of the test body is placed on a supporting cylinder of the testing machine, the long axis of the test body is perpendicular to the supporting cylinder, and a load is uniformly and vertically applied on the opposite side of the prism at a speed of 50N/s through a loading cylinder until the test body is broken. The two half prisms are kept in a wet state until the compression test, the flexural strength is calculated according to the formula (1),
R f ＝1.5F f L/b 3 ……(1)
wherein:
R f -flexural strength in megapascals (MPa);
F f -the load applied to the middle of the prism at break, in newtons (N);
l-distance between support cylinders in millimeters (mm);
b-side length of square section of prism in millimeters (mm).
Calculation and representation of flexural strength results: the average of the results of a set of three prism bending resistance was used as the test result. When one of the three intensity values exceeds +/-10% of the average value, taking the average value after eliminating as an flexural strength test result; when two of the three intensity values exceeded the average value.+ -. 10%, then the remaining one was taken as the flexural strength result. The single flexural strength result is accurate to 0.lMPa, and the arithmetic average value is accurate to 0.1MPa.
After the flexural strength test is completed, two half test pieces are taken out and subjected to a compressive strength test. Compressive strength tests were performed on the sides of the half prisms. The difference between the center of the half prism and the compression center of the pressing plate of the pressing machine is within 0.5mm,the portion of the prism exposed outside the platen was about 10mm. The entire loading process was uniformly loaded at a rate of 2500N/s until failure. The compressive strength is calculated according to the formula (2), and the compression area is 1600mm 2 :
R c ＝F c /A ……(2)
R c -compressive strength in megapascals (MPa);
F c -maximum load at failure in newtons (N);
a-the area under pressure, in square millimeters (mm).
Calculation and representation of compressive strength results: the average of six compressive strength measurements obtained on a set of three prisms was used as the test result. When one of the six measured values exceeds ±10% of the six average values, this result is rejected, and the remaining five average values are taken as results. When there are more than + -10% of the five measured values from their average, this set of results is negated. When two or more of the six measurements are simultaneously over + -10% of the average, then the set of results is voided. The single compressive strength results were accurate to 0.lMPa, and the arithmetic mean was accurate to 0.1MPa.
And (3) the water consumption in the step (3) is constant at 225g, and the mixing amount of the additive is adjusted so that the tested sand flow is 180-200mm. When a liquid water reducer is used, the solid content of the water reducer is converted into the solid powder content, and the water content of the liquid water reducer is subtracted from the water addition amount.
The fluidity of the cement mortar prepared in the step 3 is 190mm. The concrete measuring method of the cement mortar fluidity comprises the following steps: the jump table first jumps one cycle 25 times. The test mould is placed in the center of the table-board and covered by wet cotton cloth. Rapidly filling the mixed glue sand into a test die in two layers, wherein the first layer is arranged at the position about two thirds of the height of the truncated cone circular die, and is respectively scratched 5 times in two directions perpendicular to each other by a knife, and is uniformly rammed 15 times from the edge to the center by a rammer; then, the second layer of rubber sand is filled up to about 20mm higher than the truncated cone circular die, and is scratched 5 times in two directions perpendicular to each other by a small knife, and then is uniformly tamped 10 times from edge to center by a tamping rod. The glue sand after tamping should be slightly higher than the test mould. The tamping depth is that the first layer is tamped to half the height of the rubber sand, and the second layer is not tamped to exceed the surface of the tamped bottom layer. When the glue sand is filled and the tamping is carried out, the mould is tested by hand stabilization, and the mould is not required to be moved.
And after the tamping is finished, the die sleeve is taken down, the knife is inclined, the rubber sand higher than the truncated cone circular die is wiped off twice from the middle to the edge at a near horizontal angle, and the rubber sand falling on the tabletop is wiped off. The truncated cone circular mould is lifted slightly vertically upwards. The jump table is immediately started and 25 jumps are completed within 25s at a frequency of once per second. From the beginning of the water addition of the gum sand to the end of the measurement of the diffusion diameter, the completion should be within 6 min. And after the jump is finished, measuring diameters of the bottom surface of the cement mortar in two directions perpendicular to each other by using a caliper, calculating an average value, taking an integer, wherein the unit is millimeter, and the average value is the cement mortar fluidity of the water quantity.
Standard curing strength age was 3 days and 28 days.
Strength ratio= (cement mortar compressive strength of production sand test/cement mortar compressive strength of reference sand test) ×100%.
Example 2
A test method for the strength ratio of construction sand comprises the following specific steps that are the same as in example 1, wherein the production sand is purchased from the Zhuangdong Zhanjiang desalted sea sand and Guangxi machine-made sand; the strength grade of the cement is 42.5R, and the cement meets the specification of GB175, and the variety is Guangdongguan Hongcypri P.O42.5R.
Example 3
The specific steps of the test method for the strength ratio of the sand for construction are the same as those of the embodiment 1, and the difference is that the produced sand is purchased from the sea sand for the three water desalination of the bergamot and the machine-made sand of Guangdong river gate; the cement is cement meeting the specification of GB175, the strength grade is 52.5R, and the variety is Guangzhou Jinyang P.II52.5R.
Example 4
The specific steps of the test method for the strength ratio of the sand for construction are the same as those of the embodiment 1, and the difference is that the produced sand is purchased from the sea sand for the three water desalination of the bergamot and the machine-made sand of Guangdong river gate; the cement is cement meeting the specification of GB175, the strength grade is 42.5R, and the variety is Guangdongguan Hongcypri P.O42.5R.
Performance testing
The compressive strength and strength ratio of the sand were measured according to the test methods of examples 1 to 4, and the test results are shown in Table 1.
TABLE 1

Claims (10)

1. The test method of the sand strength ratio for construction is characterized by comprising the following steps of:
(1) Screening and setting reference sand;
(2) Treating and producing sand;
(3) Weighing the raw materials according to the proportion, placing the raw materials into a mortar stirrer for stirring, preparing cement mortar, preparing a test piece, curing, and testing the mortar strength;
(4) And calculating the strength ratio of the standard sand to the cement mortar prepared by the produced sand.
2. The method for testing the strength ratio of construction sand according to claim 1, wherein the reference sand is round siliceous sand having a silica content of not less than 98%.
3. The method for testing the strength ratio of construction sand according to claim 1, wherein the moisture content of the reference sand is lower than 0.2% after being dried at 105 ℃ to 110 ℃ for 1 to 3 hours.
4. The method for testing the strength ratio of the sand for construction according to claim 1, wherein the treatment method for producing the sand in the step 2 specifically comprises the following steps: spreading the produced sand in a flat plate, wherein the thickness of the sand is less than or equal to 20mm, drying at 100-110 ℃ for 3-5h, and cooling to 18-22 ℃ at room temperature.
5. The method for testing the strength ratio of construction sand according to claim 1, wherein the grain size of the produced sand is 0.075-2.36mm.
6. The method of testing the strength ratio of construction sand according to claim 1, wherein the cement has a strength grade selected from one or more of 32.5R, 42.5R, 52.5R, 62.5R, 32.5, 42.5, 52.5, 62.5.
7. The method for testing the strength ratio of construction sand according to claim 1, wherein the fluidity of the cement mortar prepared in the step 3 is 180-200mm.
8. The method according to claim 1, wherein the cement mortar prepared in the step 3 is subjected to a compressive strength test after standard curing and accelerated curing, and the standard curing is carried out at 3d and 28d.
9. The method for testing the strength ratio of construction sand according to claim 1, wherein the strength ratio is calculated by the formula: strength ratio = cement mortar compressive strength of production sand test/cement mortar compressive strength of benchmark sand test x 100%.
10. Use of a test method according to any one of claims 1-9 for the strength ratio of construction sand, in mass mortar or concrete production strength testing.
CN202310202025.9A 2023-03-06 2023-03-06 Test method for strength ratio of construction sand and application thereof Pending CN116735371A (en)

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