Method for determining maximum addition amount of flocculant in concrete and method for judging qualified content of flocculant in sand

Abstract

The present invention belongs to the technical field of building materials and provides a method for determining the maximum amount of flocculant added to concrete and a method for determining whether the flocculant content in sand is qualified. The present invention prepares clean mortar raw materials according to the formula of C30 concrete; adds 0%, 0.01%, 0.02%, 0.03% ... 0.0n% of the total mass of the cementitious material to the clean mortar raw materials to obtain raw materials for preparing a series of mortars; mixes the raw materials for preparing the series of mortars to obtain a series of mortars; measures the fluidity of the series of mortars to obtain the fluidity q0, q1, q2, q3 ... q of the series of mortars. n ; Calculate fluidity loss I n =q0‑q n ; when I n ≥60mm, take I n The minimum value of q n The amount of flocculant added to the corresponding mortar is the maximum amount of flocculant added to the concrete. The determination method of the present invention can accurately determine whether the flocculant content in the sand is qualified.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, in particular to a method for determining a maximum amount of flocculant added in concrete and a method for determining whether the flocculant content in sand is qualified. Background Art

[0002] Sand generally accounts for over 30% of concrete's volume and is a key raw material component. With restrictions on river sand mining, manufactured sand, made from crushed stone, has entered the market on a large scale. The raw stone for manufactured sand is often mixed with mud, requiring water washing to remove the mud. However, due to environmental protection requirements, water used in manufactured sand fields cannot be discharged and must be recycled. Therefore, flocculants such as polyacrylamide are often used to treat the water generated during production, clarifying it in sedimentation tanks for recycling. During the process of washing and demuding the manufactured sand with circulating water, the flocculant in the circulating water will be present in the manufactured sand as an aqueous solution or absorbed into the mud. As the manufactured sand has a high moisture and mud content, the sand produced by the facility contains a high amount of flocculant.

[0003] Flocculants like polyacrylamide have a significant impact on concrete. As a water-soluble polymer, the bridging effect of polyacrylamide's molecular chains and the charge of its anionic groups cause polyacrylamide to dissolve in water, not only transforming its coiled macromolecular structure into a curved shape, increasing the solution viscosity, but also dissociating into multi-charged, high-molecular-weight ions, disrupting the water's ionization equilibrium and causing cement colloid particles to flocculate. Tests have shown that adding just 0.4% polyacrylamide to the concrete binder can reduce the mortar's spread from 380 mm to 320 mm. Using 0.5% polyacrylamide reduced the mortar's spread from 380 mm to 265 mm, severely impacting the paste's flow properties. Therefore, the presence of flocculants in construction sand significantly impacts the flow properties of the resulting concrete. Workability is a crucial factor in evaluating commercial concrete, affecting not only its working state and pumpability but also its ease of construction. Therefore, commercial concrete mixing stations need to strictly control the flow properties of concrete. If the sand used contains flocculants, it will make it difficult for the commercial concrete mixing station to control the working performance of concrete. It will also increase the difficulty of pumping and construction, causing hidden dangers of pipe blockage and pipe burst.

[0004] Currently, flocculants in construction sand are present at concentrations below one thousandth of water, primarily in sand, mud, and water. Due to the extremely low concentration and interference from other factors, conventional chemical analysis makes them difficult to detect. The current method for determining flocculants in sand involves conducting trial mixes of flocculant-containing sand and clean sand, comparing the concrete's performance, and thereby measuring the flocculant content and its impact on concrete. However, this method is subject to significant error, primarily due to two factors. Firstly, numerous factors influence this test, including the particle size distribution, particle size, morphology, and mud content of the two sand types, making it difficult to control these variables for rigorous comparative analysis. Secondly, experimental results are also highly susceptible to operator manipulation and skill. These factors make it difficult to determine whether the sand used contains flocculants and the extent of their impact on the mixture by directly evaluating the working properties of the mixture. Consequently, commercial concrete mixing plants struggle to assess the quality of the sand they purchase, and are forced to limit the flocculant content of purchased sand to control the quality of commercial concrete. Summary of the Invention

[0005] In view of this, the present invention aims to provide a method for determining the maximum amount of flocculant added to concrete and a method for determining the acceptable flocculant content in sand. The determination method provided by the present invention is simple to operate and produces accurate results. When used to determine the acceptable flocculant content in sand, the results are accurate.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for determining the maximum amount of flocculant added to concrete, comprising the following steps:

[0008] Prepare clean mortar raw materials according to the formula of C30 concrete; the clean mortar raw materials include cement, fly ash, mineral powder, clean sand and water;

[0009] Add different amounts of flocculants into the clean mortar raw materials to obtain a series of mortars S0, S1, S2, S3...S n Preparation of raw materials; the series of mortar S0, S1, S2, S3 ... S n The mass of the flocculant in the raw materials for preparation is 0%, 0.01%, 0.02%, 0.03% ... 0.0n% of the total mass of cement, fly ash and mineral powder in the clean mortar raw materials;

[0010] The series of mortars S0, S1, S2, S3...S n The raw materials are mixed to obtain a series of mortars S0, S1, S2, S3...S n ;

[0011] The fluidity of the series of mortars is measured to obtain the fluidity q0, q1, q2, q3...q n ;

[0012] Calculation of fluidity loss I n =q0-q n ;

[0013] When I n ≥60mm, take I n The minimum value of q n , the corresponding mortar S n The amount of flocculant added in is the maximum amount of flocculant added in concrete.

[0014] Preferably, the clean sand is sand without flocculation, and the moisture content of the clean sand is ≤0.5%.

[0015] Preferably, the mass ratio of the cement, fly ash, mineral powder, clean sand and water is 380:220:120:1512:220.

[0016] Preferably, the flocculant includes one or more of polyacrylamide, polyaluminium chloride and ferrous sulfate.

[0017] The present invention also provides a method for determining whether the flocculant content in sand is qualified, comprising the following steps:

[0018] Add flocculant and sand to be tested into two equal parts of zinc chloride solution, perform flocculation, and obtain control solution and test solution respectively;

[0019] Comparing the flocculent content of the control solution and the test solution, if the flocculent content in the test solution is more than that in the control solution, the flocculant content in the sand to be tested is determined to be unqualified; if the flocculent content in the test solution is less than or equal to that in the control solution, the flocculant content in the sand to be tested is determined to be qualified;

[0020] The amount of the flocculant added to the zinc chloride solution is the maximum amount of the flocculant added obtained by the determination method described in the above technical solution;

[0021] The amount of the sand to be tested added to the zinc chloride solution is 1512 g / 4 L.

[0022] Preferably, the density of the zinc chloride solution is 1950-2000 kg / m 3 .

[0023] Preferably, the moisture content of the sand to be tested is ≤0.5%, and the particle size is ≤4.75 mm.

[0024] Preferably, before the sand to be tested is added to the zinc chloride solution, it is further dried and gravel removed in sequence; the drying temperature is ≤40°C; the gravel is removed by sieving, and the aperture of the sieve is 4.75mm.

[0025] Preferably, the flocculation temperature is 20±3° C. and the time is 60 min.

[0026] Preferably, the method further comprises: obtaining flocs in the control solution and the test solution, and comparing the dry weights of the obtained flocs;

[0027] When the dry weight of flocs in the control solution is greater than or equal to the dry weight of flocs in the test solution, the flocculant content in the sand to be tested is considered qualified;

[0028] When the dry weight of flocs in the control solution is less than the dry weight of flocs in the test solution, the flocculant content in the sand to be tested is considered to be unqualified.

[0029] The present invention provides a method for determining the maximum amount of flocculant added to concrete, comprising the following steps: preparing clean mortar raw materials according to the formula of C30 concrete; the clean mortar raw materials include cement, fly ash, mineral powder, clean sand and water; adding different amounts of flocculant to the clean mortar raw materials to obtain a series of mortars S0, S1, S2, S3...S n Preparation of raw materials; the series of mortar S0, S1, S2, S3 ... S n The mass of the flocculant in the raw materials for preparing the mortar is 0%, 0.01%, 0.02%, 0.03% ... 0.0n% of the total mass of cement, fly ash and mineral powder in the clean mortar raw materials; the series of mortars S0, S1, S2, S3 ... S n The raw materials are mixed to obtain a series of mortars S0, S1, S2, S3...S n Determine the fluidity of the series of mortars to obtain the fluidity q0, q1, q2, q3 ... q n ; Calculate fluidity loss I n =q0-q n ; when I n ≥60mm, take I n The minimum value of q n , the corresponding mortar S n The amount of flocculant added in the concrete is the maximum amount of flocculant added to the concrete. The determination method provided by the present invention can accurately determine the maximum amount of flocculant added to concrete. Furthermore, C30 concrete is widely used in production and construction, so preparing clean mortar raw materials based on the C30 concrete formula can be applied to determine the maximum amount of flocculant added to various concretes.

[0030] The present invention also provides a method for determining whether the flocculant content in sand is qualified, comprising the following steps: adding a flocculant and a sand to be tested to two equal amounts of zinc chloride solution, respectively, for flocculation to obtain a control solution and a test solution, respectively; comparing the flocculent content of the control solution and the test solution; if the flocculent content in the test solution is greater than that in the control solution, the flocculant content in the sand to be tested is determined to be unqualified; if the flocculent content in the test solution is less than or equal to that in the control solution, the flocculant content in the sand to be tested is determined to be qualified; the amount of the flocculant added to the zinc chloride solution is the maximum amount of flocculant added obtained by the determination method described in the above technical solution; and the amount of the sand to be tested added to the zinc chloride solution is 1512 g / 4 L. Because the determination method provided by the present invention uses the maximum amount of flocculant added to concrete obtained by the determination method described in the above technical solution, it can accurately determine whether the flocculant content in sand is qualified. DETAILED DESCRIPTION

[0031] The present invention provides a method for determining the maximum amount of flocculant added to concrete, comprising the following steps:

[0032] Prepare clean mortar raw materials according to the formula of C30 concrete; the clean mortar raw materials include cement, fly ash, mineral powder, clean sand and water;

[0033] Add different amounts of flocculants into the clean mortar raw materials to obtain a series of mortars S0, S1, S2, S3...S n Preparation of raw materials; the series of mortar S0, S1, S2, S3 ... S n The mass of the flocculant in the raw materials for preparation is 0%, 0.01%, 0.02%, 0.03% ... 0.0n% of the total mass of cement, fly ash and mineral powder in the clean mortar raw materials;

[0034] The series of mortars S0, S1, S2, S3...S n The raw materials are mixed to obtain a series of mortars S0, S1, S2, S3...S n ;

[0035] The fluidity of the series of mortars is measured to obtain the fluidity q0, q1, q2, q3...q n ;

[0036] Calculation of fluidity loss I n =q0-q n ;

[0037] When I n ≥60mm, take I n The minimum value of q n , the corresponding mortar S n The amount of flocculant added in is the maximum amount of flocculant added in concrete.

[0038] In the present invention, unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0039] The present invention prepares clean mortar raw materials according to the formula of C30 concrete; the clean mortar raw materials include cement, fly ash, mineral powder, clean sand and water.

[0040] In the present invention, the cement is preferably a reference cement. In the present invention, the mineral components of the reference cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite, and gypsum. No mixed materials are added, and the components are fixed, so that the test results are more accurate and highly repeatable.

[0041] In the present invention, the fly ash is preferably Class F Grade II fly ash.

[0042] In the present invention, the slag is preferably S75 granulated blast furnace slag.

[0043] In the present invention, the clean sand is preferably flocculant-free; the moisture content of the clean sand is preferably ≤0.5%. In the present invention, the method for preparing the clean sand preferably includes the following steps: washing, drying, and sieving the sand to be tested. In the present invention, the washing agent preferably includes deionized water; the present invention does not impose specific restrictions on the washing agent, as long as it can completely remove soil, mud, and flocculants from the sand to be tested. In the present invention, the drying temperature is preferably ≤40°C. In the present invention, the sieve mesh diameter is preferably 4.75 mm.

[0044] In the present invention, the water preferably includes water without a flocculant.

[0045] In the present invention, the mass ratio of the cement, fly ash, mineral powder, clean sand and water is preferably 380:220:120:1512:220.

[0046] In the present invention, the ratio of water, clean sand and cementitious materials (including cement, fly ash and mineral powder) is fixed, and the flow time of the obtained mortar is fixed, which is convenient for measuring the fluidity and quantifying the influence of the flocculating components in the sand on the flow properties of the mortar.

[0047] After preparing the clean mortar raw materials, the present invention adds different amounts of flocculants to the clean mortar raw materials to obtain a series of mortars S0, S1, S2, S3...S n Preparation of raw materials; the series of mortar S0, S1, S2, S3 ... S n The mass of the flocculant in the preparation raw materials is 0%, 0.01%, 0.02%, 0.03%...0.0n% of the total mass of cement, fly ash and mineral powder in the clean mortar raw materials.

[0048] In the present invention, the flocculant preferably includes one or more of polyacrylamide, polyaluminium chloride and ferrous sulfate.

[0049] Get a series of mortars S0, S1, S2, S3...S n After the raw materials are prepared, the present invention prepares the series of mortars S0, S1, S2, S3...S n The raw materials are mixed to obtain a series of mortars S0, S1, S2, S3...S n .

[0050] In the present invention, the series of mortars S0, S1, S2, S3...S n The mixing of the raw materials for preparation preferably includes: a first stirring of water, cement, fly ash and mineral powder, and then a second stirring of clean sand is added; when the raw materials for preparation of the series of mortars preferably include a flocculant, the flocculant is preferably added during the first stirring. In the present invention, the revolution stirring rate of the first stirring is preferably 62±5r / min, and the rotation stirring rate is preferably 140±5r / min; the time is preferably 30±1s. In the present invention, the second stirring includes sequentially performing a first high-speed stirring, stopping stirring and a second high-speed stirring; the revolution stirring rate of the first high-speed stirring is preferably 125±10r / min, and the rotation stirring rate is preferably 285±10r / min, and the time is preferably 30±1s. In the present invention, the time of stopping stirring is preferably 90s. In the present invention, within 15±1s of stopping stirring, the stirring pot is lowered, and the mortar on the blades, pot wall and pot bottom is scraped into the pot with a scraper. In the present invention, the second high-speed stirring mode preferably has an orbital stirring rate of 125±10 r / min and an autorotational stirring rate of 285±10 r / min; the stirring time is preferably 60±1 s. The purpose of the second stirring mode is to prevent the rotating blades of the mixer from completely stirring the cementitious material (cement) that has sunk to the bottom of the mixing pot. Removing the mixing pot and scraping up the cementitious material at the bottom with a scraper, and then stirring again, can make the mortar more evenly mixed. Furthermore, stirring in the second stirring mode, i.e., the rapid mode, can break up the flocculent clumps in the mortar, preventing uneven flow during testing and reducing test errors.

[0051] After obtaining the series of mortars, the present invention measures the fluidity of the series of mortars to obtain the fluidity q0, q1, q2, q3...q n .

[0052] In the present invention, the fluidity is preferably determined according to GB / T8077.

[0053] In the present invention, after the flocculant is added, the curvilinear molecules of the flocculant not only increase the viscosity of the mortar, but also dissociate into multi-charged, large-molecular-weight ions, thereby breaking the ionization balance of the mortar paste and causing the colloid to flocculate. This is also the reason why the construction sand containing flocculating components affects the working performance of the mixed concrete. The flowability of the mortar is quantitatively determined by the flow meter, which facilitates the determination of the degree of influence of the flocculant in the construction sand on the working performance of the concrete.

[0054] After obtaining the fluidity of the series of mortars, the present invention calculates the fluidity loss I n =q0-q n .

[0055] In the present invention, when I n ≥60mm, take I n The minimum value of q n , the corresponding mortar S n The amount of flocculant added in is the maximum amount of flocculant added in concrete.

[0056] The present invention also provides a method for determining whether the flocculant content in sand is qualified, comprising the following steps:

[0057] Add flocculant and sand to be tested into two equal parts of zinc chloride solution, perform flocculation, and obtain control solution and test solution;

[0058] Comparing the flocculent content of the control solution and the test solution, if the flocculent content in the test solution is more than that in the control solution, the flocculant content in the sand to be tested is determined to be unqualified; if the flocculent content in the test solution is less than or equal to that in the control solution, the flocculant content in the sand to be tested is determined to be qualified;

[0059] The amount of the flocculant added to the zinc chloride solution is the maximum amount of the flocculant added obtained by the determination method described in the above technical solution;

[0060] The amount of the sand to be tested added to the zinc chloride solution is 1512 g / 4 L.

[0061] The invention adds a flocculant and sand to be tested into two equal amounts of zinc chloride solutions, performs flocculation, and obtains a control solution and a test solution.

[0062] In the present invention, the sand to be tested preferably includes machine-made sand. In the present invention, the water content of the sand to be tested is preferably ≤0.5%, and the particle size is preferably ≤4.75mm. In the present invention, before the sand to be tested is added to the zinc chloride solution, it also includes drying and removing gravel in sequence; the drying temperature is ≤40°C; the method of removing gravel is screening, and the aperture of the sieve holes is 4.75mm. In the present invention, the water content of the sand to be tested is controlled to be ≤0.5%, ensuring that the main body of the sand to be tested under the test procedure is sand and part of stone powder and mud, and the water content of the sand to be tested is ≤0.5%, which can avoid the deviation of the test results due to the difference in water content, resulting in poor repeatability. At the same time, according to the standard GB / T 14684-2011 "Construction Sand", the particle size of construction sand should not exceed 4.75 mm, so the sand to be tested was screened. In addition, the flocculant adsorbed by the construction sand is affected by its mud content and specific surface area. In order to avoid the presence of large particles in the sand to be tested that may have a greater impact on the specific surface area of the sand and cause fluctuations in the flocculant content in the sand to be tested, particle components larger than 4.75 mm were removed.

[0063] In the present invention, the density of the zinc chloride solution is preferably 1950-2000 kg / m 3 In the present invention, zinc chloride is easily soluble in water and hydrolyzes in water to produce insoluble colloid particles, which make the solution colloidally turbid rather than clear and transparent. As time goes by, these insoluble colloid particles gradually aggregate and precipitate.

[0064] In the present invention, the flocculation temperature is preferably 20±3° C., and the time is preferably 60 min. In the present invention, the flocculation is preferably performed under stirring.

[0065] After obtaining the control liquid and the test liquid, the present invention compares the flocculant content of the control liquid and the test liquid. When the flocculant in the test liquid is more than that in the control liquid, it is determined that the flocculant content in the sand to be tested is unqualified; if the flocculant in the test liquid is less than or equal to the control liquid, it is determined that the flocculant content in the sand to be tested is qualified.

[0066] The present invention preferably further includes obtaining flocs in the control liquid and the test liquid, and comparing the dry weights of the obtained flocs; when the dry weight of the flocs in the control liquid is greater than or equal to the dry weight of the flocs in the test liquid, the flocculant content in the sand to be tested is considered qualified; when the dry weight of the flocs in the control liquid is less than the dry weight of the flocs in the test liquid, the flocculant content in the sand to be tested is considered unqualified.

[0067] The determination method provided by the present invention is simple to operate and has high result accuracy.

[0068] In the present invention, the amount of the flocculant added to the zinc chloride solution is the maximum amount of the flocculant added obtained by the determination method described in the above technical solution;

[0069] The amount of the sand to be tested added to the zinc chloride solution is 1512 g / 4 L.

[0070] The following describes in detail the method for determining the maximum amount of flocculant added to concrete and the method for determining the qualified flocculant content in sand provided by the present invention in conjunction with the embodiments. However, they should not be construed as limiting the scope of protection of the present invention.

[0071] Example 1

[0072] The sand to be tested in this embodiment is machine-made sand, and the flocculant commonly present in machine-made sand is polyacrylamide. First, the maximum addition amount of polyacrylamide in concrete is determined, including the following steps:

[0073] (1) The sand to be tested is washed to remove the flocculant and soil in the sand; then dried at 40°C, passed through a 4.75mm sieve to remove gravel, and obtain clean sand.

[0074] (2) Prepare the following raw materials for the clean mortar according to the C30 concrete mix ratio: 380 g of base cement, 220 g of Class F II fly ash, 120 g of S75 granulated blast furnace slag, 220 g of water, and 1512 g of the clean sand obtained in step (1).

[0075] (3) Take 8 parts of the same clean mortar raw materials, add 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06% and 0.07% of the total weight of standard cement, F class II fly ash and S75 granulated blast furnace slag, respectively, to obtain a series of mortars S0, S1, S2, S3...S n Preparation raw materials.

[0076] (4) The series of mortars S0, S1, S2, S3...S n The raw materials are mixed to obtain a series of mortars S0, S1, S2, S3...S nThe specific steps include: fixing the pot on a fixed frame and raising it to the working position; turning on the planetary mortar mixer, first putting the mixer in the standby state and then operating according to the following procedures: adding water to the pot, if the raw materials for preparing the series of mortars contain polyacrylamide, add the polyacrylamide and water to the pot together; then add cement, fly ash and mineral powder, place the pot on a fixed frame, raise it to a fixed position, and then immediately start the machine and stir at a low speed (the revolution stirring rate is 62±5r / min, the rotation stirring rate is 140±5r / min) for 30 ±1s later; add clean sand, and continue stirring at high speed (the revolution stirring rate is 125±10r / min, the rotation stirring rate is 285±10r / min) for 30±1s; stop stirring for 90s, and within 15±1s from the start of stopping stirring, put down the stirring pot, and use a scraper to scrape the mortar on the blades, pot wall and pot bottom into the pot; then stir at high speed (the revolution stirring rate is 125±10r / min, the rotation stirring rate is 285±10r / min) for 60±1s to obtain a series of mortars S0, S1, S2, S3, S4, S5, S6 and S7.

[0077] (5) Repeat steps (3) and (4) 47 times.

[0078] (6) The fluidity test method of mortar GB / T8077 was used to determine the fluidity of the series of mortars. The results are shown in Table 1. The GB / T8077 test method is as follows: the mixed mortar was quickly loaded into the mold twice. The first time, it was loaded to two-thirds of the truncated cone mold. The mortar was scratched 5 times in two directions perpendicular to each other with a spatula, and tamped 15 times evenly from the edge to the center with a tamping rod. Then, the second layer of mortar was loaded to about 20 mm above the truncated cone mold. The mortar was scratched 10 times with a spatula and tamped 10 times with a tamping rod. When loading the mortar and tamping, the truncated cone mold was held down by hand to prevent it from moving. After tamping, the mold sleeve was removed, and the mortar that was above the truncated cone mold was scraped off and smoothed with a spatula. The truncated cone mold was then lifted vertically upward and placed on a table. The diameters of the mortar bottom surface in two directions perpendicular to each other were measured with a caliper. The average value was calculated and the fluidity was obtained by taking the integer. The average value was calculated for 48 tests.

[0079] Table 1 Fluidity results of series mortars

[0080]

[0081]

[0082]

[0083] It can be seen from Table 1 that the average fluidity results of the series of mortars obtained from 48 tests are: q0 = 380 mm, q1 = 374 mm, q2 = 360 mm, q3 = 332 mm, q4 = 316 mm, q5 = 273 mm, q6 = 232 mm, q7 = 201 mm.

[0084] After many tests, the fluidity loss I=60mm causes the slump loss of the trial mix to be 20mm. Therefore, when the fluidity loss I=60mm is obtained, the corresponding flocculant content of q4 is the maximum addition amount of polyacrylamide in concrete, that is, the maximum addition amount of polyacrylamide in concrete is 0.04% of the total mass of cementitious materials (cement, fly ash and mineral powder).

[0085] After obtaining the maximum amount of polyacrylamide added in concrete, the present invention determines whether the acrylamide content in the sand to be tested is qualified, comprising the following steps:

[0086] (7) Prepare 2 portions with a volume of 4 L and a density of 2000 kg / m 3 of zinc chloride solution.

[0087] (8) Add polyacrylamide to one of the 4 L zinc chloride solutions according to the maximum addition amount obtained in step (6), stir thoroughly with a glass rod, and after no more precipitation appears, filter the entire solution with medium-speed quantitative filter paper. After the filtration is completed, the precipitate on the filter paper is naturally air-dried and weighed to obtain 804 g.

[0088] (9) The sand to be tested was dried at 40°C and then passed through a 4.75 mm sieve. 1512 g of the sieved sand to be tested was weighed and added to the other 4 L of 2000 kg / m3 density sand in step (7). 3 The zinc chloride solution was stirred thoroughly with a glass rod, and allowed to stand until no more precipitation appeared. The solution was filtered with medium-speed quantitative filter paper. After the filtration was completed, the precipitation on the filter paper was naturally air-dried and weighed to obtain m13g.

[0089] (10) Since m1≤m0, the content of flocculant acrylamide in the sand to be tested is considered to be qualified.

[0090] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for determining the maximum amount of flocculant added to concrete, characterized in that: The following steps are involved: Prepare clean mortar raw materials according to the formula of C30 concrete; the clean mortar raw materials include cement, fly ash, mineral powder, clean sand and water; Add different amounts of flocculants into the clean mortar raw materials to obtain a series of mortars S0, S1, S2, S3...S n Preparation of raw materials; the series of mortar S0, S1, S2, S3 ... S n The mass of the flocculant in the raw materials for preparation is 0%, 0.01%, 0.02%, 0.03% ... 0.0n% of the total mass of cement, fly ash and mineral powder in the clean mortar raw materials; The series of mortars S0, S1, S2, S3...S n The raw materials are mixed to obtain a series of mortars S0, S1, S2, S3...S n ; The fluidity of the series of mortars is measured to obtain the fluidity q0, q1, q2, q3...q n ; Calculation of fluidity loss I n =q0-q n ; When I n ≥60mm, take I n The minimum value of q n , the corresponding mortar S n The amount of flocculant added in is the maximum amount of flocculant added in concrete; The clean sand is sand without flocculant, and the moisture content of the clean sand is ≤0.5%; The mass ratio of the cement, fly ash, mineral powder, clean sand and water is 380:220:120:1512:

220.

2. The determination method according to claim 1, characterized in that The flocculant includes one or more of polyacrylamide, polyaluminium chloride and ferrous sulfate.

3. A method for determining whether the flocculant content in sand is qualified, characterized in that: The following steps are involved: Add flocculant and sand to be tested into two equal parts of zinc chloride solution, perform flocculation, and obtain control solution and test solution respectively; Comparing the flocculent content of the control solution and the test solution, if the flocculent content in the test solution is more than that in the control solution, the flocculant content in the sand to be tested is determined to be unqualified; if the flocculent content in the test solution is less than or equal to that in the control solution, the flocculant content in the sand to be tested is determined to be qualified; The amount of the flocculant added to the zinc chloride solution is the maximum amount of the flocculant added obtained by the determination method according to any one of claims 1 to 2; The amount of the sand to be tested added to the zinc chloride solution is 1512 g / 4 L.

4. The determination method according to claim 3, wherein: The density of the zinc chloride solution is 1950-2000 kg / m 3 .

5. The determination method according to claim 3, wherein: The moisture content of the sand to be tested is ≤0.5%, and the particle size is ≤4.75 mm.

6. The determination method according to claim 3 or 5, characterized in that: Before the sand to be tested is added to the zinc chloride solution, it is dried and gravel is removed in sequence; the drying temperature is ≤40°C; the gravel is removed by screening, and the aperture of the sieve is 4.75mm.

7. The determination method according to claim 3, wherein: The flocculation temperature is 20±3° C. and the time is 60 min.

8. The determination method according to claim 3, wherein: Also includes: Obtain flocs from the control solution and the test solution, and compare the dry weights of the obtained flocs; When the dry weight of flocs in the control solution is greater than or equal to the dry weight of flocs in the test solution, the flocculant content in the sand to be tested is considered qualified; When the dry weight of flocs in the control solution is less than the dry weight of flocs in the test solution, the flocculant content in the sand to be tested is considered to be unqualified.

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