Method for detecting content of flocculating agent in machine-made sand through sedimentation filtration backstepping method

Abstract

The invention belongs to the technical field of building material detection, and particularly relates to a method for detecting the content of a flocculating agent in machine-made sand through a sedimentation and filtration backstepping method. Comprising the following steps: (1) drying slow quantitative filter paper to constant weight for later use; (2) original sample treatment: adding machine-made sand into purified water, stirring and dispersing, standing, taking supernate, filtering, drying, weighing and calculating the mass of stone powder; (3) pretreatment of the machine-made sand: drying the machine-made sand at 110 DEG C to destroy the flocculation effect, and measuring the water content w; (4) flocculation adsorption experiment: preparing a PAM solution with gradient concentration, adding the dried machine-made sand into the solution, repeating the settling and filtering operation, and measuring the mass of the stone powder in the supernatant under each concentration; (5) drawing a standard curve; (6) reversely deducing the content of the flocculating agent in the standard curve according to the mass of the to-be-detected sample stone powder; the method provided by the invention can rapidly and quantitatively detect the residual amount of the flocculant, provides data support for concrete mix proportion design, and improves the application quality of machine-made sand.

Description

Technical Field

[0001] This invention relates to the field of building material testing technology, specifically to a method for detecting the flocculant content in manufactured sand using a sedimentation filtration backpropagation method. Background Technology

[0002] With the rapid development of my country's construction industry, the demand for construction sand continues to rise. Long-term mining has led to a growing scarcity of high-quality river sand resources in China, while the overexploitation of natural river sand has severely damaged the ecological balance and hydrological stability of river channels, exacerbating soil erosion and biodiversity degradation. Therefore, the state has introduced a ban on natural sand mining, strictly limiting its extraction. Against this backdrop, manufactured sand has become the inevitable choice for replacing natural sand as fine aggregate in concrete.

[0003] To meet environmental protection requirements, the wet production of manufactured sand requires water washing to remove stone powder and relies on flocculants (such as polyacrylamide, PAM) for wastewater recycling. However, this process has several pressing issues, such as the impact of residual flocculants on concrete properties. Recycled water leads to flocculant accumulation on the surface of the manufactured sand, causing problems like decreased concrete fluidity, increased viscosity, and accelerated loss over time. To compensate for this, the amount of admixtures needs to be increased by 30%–40%. It is worth noting that due to the low level of supervision over flocculant addition by manufacturers during the manufactured sand production process and the uncertainty of the number of times the manufactured sand is washed, the amount of residual flocculant in the manufactured sand is unpredictable, thus making it impossible to determine the appropriate amount of admixtures.

[0004] Therefore, it is of great importance and significance to invent a detection method that can quickly and quantitatively detect the content of residual flocculants in manufactured sand and provide data support for concrete mix design, so as to promote the wider application of manufactured sand and improve the quality of concrete. Summary of the Invention

[0005] This invention addresses the technical problem of determining the amount of residual flocculant in manufactured sand by providing a method for detecting the flocculant content in manufactured sand using a sedimentation filtration backpropagation method. Manufactured sand in commercial concrete still contains varying degrees of stone powder, and the residual flocculant within it still has a flocculating effect. This invention utilizes the flocculation effect of the residual flocculant, comparing it with the flocculation effect of a known concentration of flocculant, to determine the content of residual flocculant in the manufactured sand.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for detecting the flocculant content in manufactured sand by sedimentation filtration reverse propagation, characterized by comprising the following steps: (1) Place the slow-speed quantitative filter paper in a forced-air drying oven and dry it at 60°C until constant weight, then set aside for later use; (2) Determination of the quality of raw stone powder Add M1 grams of the tested manufactured sand to V ml of pure water and stir for ≥3 min. After standing for 1 min, take 25 mL of the supernatant 2 cm above the liquid surface, filter it with slow quantitative filter paper, dry it and weigh it to obtain the mass increment m of the filter paper, which is the mass of the stone powder. (3) Pretreatment of manufactured sand Take ≥6 kg of manufactured sand and dry it at 110℃ to destroy the flocculation effect, and determine the moisture content w; (4) Prepare PAM standard solution The mass fraction gradients are 0.001‰, 0.005‰, 0.01‰, 0.02‰, 0.03‰, 0.04‰, 0.05‰, 0.1‰, and 0.2‰. (5) Flocculation and Adsorption Experiment Weigh 9 portions of dried manufactured sand, with the mass of each portion of dried manufactured sand being M2 = M1 g / (1 + w). Then, add PAM solutions of different concentrations to each portion of dried manufactured sand, with a volume of V mL + M1 g × w / ρ, where ρ is the density of pure water. After stirring and standing for 1 min, take 25 mL of the supernatant 2 cm from the liquid surface and filter it with slow quantitative filter paper. Dry and weigh the filter paper to obtain the mass increment, which is the mass of stone powder in the supernatant. (6) Draw the standard curve With PAM concentration as the abscissa and the corresponding supernatant stone powder mass obtained in step (4) as the ordinate, a standard comparison curve was established by fitting a B-spline curve. (7) Back-calculation of flocculant content: Substitute the mass of stone powder obtained in step (1) into the standard curve to back-calculate the flocculant content in the manufactured sand.

[0007] As a further limitation of the technical solution of the present invention, the ratio of the amount of the test-tested manufactured sand to the amount of pure water in step (2) is 3g:5mL.

[0008] As a further limitation of the technical solution of the present invention, in step (6), Origin-2018 software is used to perform B-style curve fitting on the PAM concentration and the corresponding stone powder mass data.

[0009] As a further limitation of the technical solution of the present invention, the filtration operation for calculating the mass of stone powder in the supernatant in steps (2) and (5) uses slow quantitative filter paper, and the filter paper is dried in a 60°C forced-air drying oven to constant weight after filtration.

[0010] Compared with the prior art, the present invention has the following beneficial effects: This method can quickly and quantitatively detect the residual amount of flocculant, providing data support for concrete mix design and improving the quality of manufactured sand application. Attached Figure Description

[0011] Figure 1This is a standard comparison curve obtained in Embodiment 1 of the present invention.

[0012] Figure 2 According to Figure 1 A schematic diagram illustrating the reverse calculation of flocculant content. Detailed Implementation

[0013] The present invention will be further described below with reference to specific embodiments.

[0014] A method for detecting flocculant content in manufactured sand by sedimentation filtration reverse impingement method includes the following steps: 1. Determination of the mass of stone powder in the original sample (1) Place the slow quantitative filter paper in a forced-air drying oven and dry it at 60°C until constant weight. Then place it in a desiccator to cool and wait for use.

[0015] (2) Take 300g of the manufactured sand to be tested and add it to 500mL of pure water. Stir the sand to fully disperse the stone powder in the pure water. Stir mechanically for ≥3min to fully disperse the stone powder. (3) After standing for 1 minute, use a pipette to draw 25 mL of supernatant from 2 cm above the liquid surface; (4) Weigh the dry mass m0 of the slow quantitative filter paper, filter the supernatant, and place the filter paper in a 60℃ forced-air drying oven after filtration. (5) Weigh the dried filter paper mass m1 and calculate the original stone powder mass: m = m1 - m0.

[0016] 2. Pretreatment of manufactured sand (1) Take ≥6kg of manufactured sand and dry it at 110℃ to destroy the flocculation effect of the flocculant; (2) Determine the moisture content w of manufactured sand (Calculation method: w = (m 湿 -m 干 () / m dry × 100%).

[0017] 3. Preparation of PAM standard solution Prepare polyacrylamide (PAM) solutions with mass fraction gradients of: 0.001‰, 0.005‰, 0.01‰, 0.02‰, 0.03‰, 0.04‰, 0.05‰, 0.1‰, and 0.2‰.

[0018] 4. Preparation of dried sand samples Calculate the sample quantity of dried manufactured sand: m 干 =m 湿 / (1+w)(where m) 湿 =300g), weigh out 9 portions for later use.

[0019] 5. Flocculant Adsorption Experiment (1) Add each portion of dried machine sand to PAM solution with different mass fractions in sequence; (2) Stir mechanically for ≥3 min, then let stand for 1 min; (3) Determine the mass m of the supernatant stone powder at each concentration according to steps 2 and 3. i (i represents the concentration number).

[0020] 6. Curve Fitting With PAM concentration as the x-axis and the mass of stone powder in the supernatant as the y-axis, a standard comparison curve was established using B-spline curve fitting with Origin-2018 software.

[0021] 7. Sample testing The manufactured sand from the original stone powder sample was tested according to the above procedure, and the flocculant content was inferred from the standard curve based on the stone powder mass m. Example 1

[0022] I. Detection of stone powder content in the original sample 1. Place the slow-speed quantitative filter paper in a forced-air drying oven and dry it at 60°C until constant weight. Then place it in a desiccator to cool and wait for use.

[0023] 2. Measure 500.0 mL of deionized water into a beaker, weigh 300.0 g of the machine-made sand to be tested and add it to the deionized water, and place the beaker in the ultrasonic bath.

[0024] 3. Use a fan-blade mixer to stir at 600 rad / min for 3 minutes. After stirring, place the beaker on the work surface and let it stand for 1 minute.

[0025] 4. Weigh the cooled filter paper; the mass m1 is 1.1200g. Using a pipette, transfer 25mL of the supernatant from the settled beaker at a distance of 2cm from the liquid surface. Filter the supernatant through slow quantitative filter paper, then dry the filter paper in a drying oven. After cooling in a desiccator, weigh the filter paper; the mass m2 is 1.1311g.

[0026] 5. Calculate the mass of stone powder: m = m2 - m1 = 0.0111 g.

[0027] II. Preparation of PAM standard solution 1. Use polyacrylamide chemical reagent from Tianjin Kaitong Chemical Reagent Co., Ltd., with a content greater than 90%.

[0028] 2. Weigh 1 mg, 5 mg, 10 mg, 20 mg, 30 mg, 40 mg, 50 mg, 100 mg, and 200 mg of polyacrylamide respectively and dissolve them in 1 L of deionized water to prepare PAM standard solutions with mass fractions of 0.001‰, 0.005‰, 0.01‰, 0.02‰, 0.03‰, 0.04‰, 0.05‰, 0.1‰, and 0.2‰.

[0029] III. Drawing a comparison curve graph 1. Take 6 kg of manufactured sand and dry it in a forced-air drying oven at 110℃ to destroy the flocculation effect of the flocculant. Simultaneously, measure the moisture content of the manufactured sand, w = (m...). 湿 -m 干 ) / m_dry = 13.13%.

[0030] 2. Calculate the sample weight of the dried manufactured sand, in m. 干 =m 湿 / (1 + w) = 300g / (1 + 13.13%) = 265g, weigh out 9 portions for later use.

[0031] 3. Take 500mL + 300mL × w of PAM solution with a mass fraction of 0.001‰ (i.e., 539mL) and add it to the beaker. Then add the weighed machine-made sand to the beaker.

[0032] 4. Use a fan-blade mixer to stir at 600 rad / min for 3 minutes. After stirring, place the beaker on the work surface and let it stand for 1 minute.

[0033] 5. Weigh the cooled filter paper (m) 11 The mass is 1.1250 g. Using a pipette, 25 mL of the supernatant was transferred from the settled beaker, filtered through slow-speed quantitative filter paper, dried in a drying oven, cooled in a desiccator, and weighed. The mass is m. 12 It weighs 1.1430g.

[0034] 6. Calculate the mass m of stone powder. 0.001‰ =m 12 -m 11 =0.0180g.

[0035] 7. Calculate m in the same way for each case. 0.001‰ m 0.005‰ m 0.01‰ m 0.02‰ m 0.03‰ m 0.04‰ m 0.05‰ m 0.1‰ m 0.2‰ Use Origin-2018 to draw a dotted line graph and fit it using a B-style curve, such as... Figure 1 As shown.

[0036] IV. Back-calculation of flocculant content Inserting 0.0111g into the comparison curve graph, the PAM content was found to be 0.0080‰. Figure 2 As shown.

Claims

1. A method for detecting flocculant content in manufactured sand by sedimentation filtration reverse propagation, characterized in that, Includes the following steps: (1) Place the slow-speed quantitative filter paper in a forced-air drying oven and dry it at 60°C until constant weight, then set aside for later use; (2) Determination of the quality of raw stone powder Add the mass of the test material M1 grams to a volume of pure water V ml and stir for ≥3 min. After standing for 1 min, take 25 mL of the supernatant 2 cm above the liquid surface, filter it with slow quantitative filter paper, dry it and weigh it to obtain the mass increment m of the filter paper, which is the mass of the stone powder. (3) Pretreatment of manufactured sand Take ≥6 kg of manufactured sand and dry it at 110℃ to destroy the flocculation effect, and determine the moisture content w; (4) Prepare PAM standard solution The mass fraction gradients are 0.001‰, 0.005‰, 0.01‰, 0.02‰, 0.03‰, 0.04‰, 0.05‰, 0.1‰, and 0.2‰. (5) Flocculation and Adsorption Experiment Weigh 9 portions of dried manufactured sand, with the mass of each portion of dried manufactured sand being M2 = M1 g / (1 + w). Then, add PAM solutions of different concentrations to each portion of dried manufactured sand, with a volume of V mL + M1 g × w / ρ, where ρ is the density of pure water. After stirring and standing for 1 min, take 25 mL of the supernatant 2 cm from the liquid surface and filter it with slow quantitative filter paper. Dry and weigh the filter paper to obtain the mass increment, which is the mass of stone powder in the supernatant. (6) Draw the standard curve With PAM concentration as the abscissa and the corresponding supernatant stone powder mass obtained in step (4) as the ordinate, a standard comparison curve was established by fitting a B-spline curve. (7) Back-calculation of flocculant content: Substitute the mass of stone powder obtained in step (1) into the standard curve to back-calculate the flocculant content in the manufactured sand.

2. The method for detecting flocculant content in manufactured sand by sedimentation filtration reverse propagation according to claim 1, characterized in that, In step (2), the ratio of the amount of the manufactured sand to be tested to the amount of purified water is 3g:5mL.

3. The method for detecting flocculant content in manufactured sand by sedimentation filtration reverse propagation according to claim 1, characterized in that, In step (6), Origin-2018 software was used to perform B-style curve fitting on the PAM concentration and the corresponding stone powder mass data.

4. The method for detecting flocculant content in manufactured sand by sedimentation filtration reverse propagation according to claim 1, characterized in that, In steps (2) and (5), the filtration operation for calculating the mass of the supernatant stone powder was performed using slow quantitative filter paper. After filtration, the filter paper was dried in a 60°C forced-air drying oven to constant weight.

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