Method for testing adsorption amount of fine aggregate to water reducing agent and application thereof

Abstract

The present application relates to the field of water-reducing agent adsorption amount test method, in particular to a fine aggregate water-reducing agent adsorption amount test method and application thereof, at least comprising the following steps: (1) instrument and equipment preparation; (2) weighing cement, fine aggregate, water and water-reducing agent raw materials; (3) mixing mortar, adjusting the dosage of water-reducing agent to make the initial spread of mortar at the same value, obtaining mixed mortar, and recording the dosage of water-reducing agent; (4) calculating the adsorption amount of fine aggregate to water-reducing agent according to the formula; (5) using the spread of mortar to characterize the adsorption amount of fine aggregate to water-reducing agent. The present application provides a fine aggregate water-reducing agent adsorption amount test method to fully characterize the adsorption of impurities in sand to water-reducing agent, quantifies the adsorption of spread to water-reducing agent, has high reliability, simple method and easy operation, and is helpful for the preparation of performance-stable concrete.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water-reducing agent adsorption amount test methods, in particular to a test method for the adsorption amount of fine aggregate on water-reducing agent and application thereof. BACKGROUND

[0002] In the field of concrete industry, water-reducing agent, as one of the essential raw materials, affects the comprehensive performance of concrete. However, due to the different production processes and unstable quality of fine aggregate currently used in concrete, clay substances and flocculants in fine aggregate can adsorb water-reducing agent, so that a certain amount of water-reducing agent cannot effectively be used in the concrete mixing process to achieve the water-reducing function, which thus leads to rapid loss of the slump of fresh concrete and difficulty in ensuring transportation, pumping and construction.

[0003] The method of methylene blue test of GB / T 14684-2022 "Construction sand" characterizes the adsorption degree of impurities in sand on water-reducing agent. The premise of this test method is that it cannot fully characterize the adsorption of water-reducing agent. If a certain substance has adsorption on methylene blue, it also has adsorption on water-reducing agent; if a certain substance has no adsorption on methylene blue, it also has no adsorption on water-reducing agent. Further, if a certain substance has obvious adsorption on methylene blue, it also has obvious adsorption on water-reducing agent; if a certain substance has no obvious adsorption on methylene blue, it also has no obvious adsorption on water-reducing agent. That is, the adsorption of impurities in sand on methylene blue and water-reducing agent presents a proportional relationship. However, in fact, this proportional relationship does not exist. For example, the flocculant in sand has adsorption on water-reducing agent, but not obvious adsorption on methylene blue. The "Concrete" magazine (Article No. 1002-3550 (2022) 07-0067-07) published "Thinking about the characterization of clay content in manufactured sand by methylene blue method"; "Jiangxi Building Materials" magazine (Article No. 1006-2890 (2022) 06-0044-04) published "Experimental study on the influence of flocculant residue on the methylene blue value of manufactured sand", which have demonstrated that the methylene blue test method cannot accurately judge the product quality of fine aggregate, which is not conducive to guiding concrete production. Therefore, the methylene blue test method in GB / T 14684-2022 "Construction sand" has certain defects, and the effectiveness of the results cannot be effectively guaranteed.

[0004] Chinese patent application (authorized publication No. CN 103466987 B) discloses a composite clay adsorbent for shielding high content clay adsorption of polycarboxylate superplasticizer in concrete and its preparation method and use method. The composite clay adsorbent is prepared and used for mixing of concrete, and the influence of the composite clay adsorbent on the fluidity of mortar under different dosages is characterized by the fluidity of mortar. However, there is no effective test method for the adsorption amount of fine aggregate on water-reducing agent. SUMMARY

[0005] Therefore, the application provides a method for testing the adsorption amount of fine aggregate on water reducing agent to fully characterize the adsorption on water reducing agent, quantifies the adsorption of fine aggregate on water reducing agent by spread degree, has high result reliability, is simple and easy to operate, and is helpful to the preparation of performance-stable concrete.

[0006] In one aspect, the application provides a method for testing the adsorption amount of fine aggregate on water reducing agent, which at least comprises the following steps:

[0007] (1) instrument and equipment preparation;

[0008] (2) weighing cement, fine aggregate, water and water reducing agent raw materials;

[0009] (3) mixing mortar, adjusting the dosage of water reducing agent to make the initial spread degree of mortar at the same value, obtaining mixed mortar, and recording the dosage of water reducing agent;

[0010] (4) calculating the adsorption amount of fine aggregate on water reducing agent according to the formula;

[0011] (5) using the spread degree of mortar to characterize the adsorption amount of fine aggregate on water reducing agent.

[0012] As a preferred technical solution, the instrument processing specifically comprises: wiping the stirring pot and stirring leaves with a wet cloth until the surface of the stirring pot and stirring leaves is wet but without water stains. Before mixing the mortar, the stirring pot and stirring leaves are wiped to avoid introducing water error and affecting the accuracy of the adsorption effect of fine aggregate on water reducing agent, and to avoid loss of powdered raw materials due to too dry surface of the stirring pot and stirring leaves, thereby ensuring the accuracy of the test method results.

[0013] As a preferred technical solution, the fine aggregate is dried to an absolutely dry state at 100-110 DEG C and then cooled to 18-22 DEG C for standby.

[0014] As a preferred technical solution, the fine aggregate is treated as follows: when the amount of fine powder less than 0.075 mm in the fine aggregate is less than or equal to 5%, the part with a nominal diameter less than 2.36 mm is taken as the fine aggregate raw material to mix mortar and perform subsequent tests; when the amount of fine powder less than 0.075 mm in the fine aggregate is greater than 5%, the fine aggregate with a nominal diameter of 0.15 mm-2.36 mm and less than 0.15 mm is taken as the fine aggregate raw material to mix mortar and perform subsequent tests.

[0015] As a preferred technical solution, the raw materials are weighed according to the amounts in Table 1:

[0016] Table 1,

[0017]

[0018]

[0019] As a preferred technical solution, the raw materials are weighed according to the amounts in Table 2:

[0020] Table 2,

[0021]

[0022] As a preferred technical solution, the test method for the initial spread of the mortar is:

[0023] The mixed mortar is quickly placed in a truncated cone round mold, leveled with a ruler, the test mold is lifted in the vertical direction, and the mortar is allowed to flow freely on the glass plate until it stops flowing (30s after the test mold is lifted), the maximum diameters of the two directions perpendicular to each other of the flowing part are measured with a steel ruler, and the average value is taken as the initial spread of the mortar.

[0024] Preferably, the truncated cone round mold and the glass plate are wiped with a wet cloth before use to maintain a wet surface without water stains.

[0025] As a preferred technical solution, the mortar tested for initial spread also needs to be tested for spread over time, and the test method for spread over time is: the mortar tested for initial spread is scraped into the mixing pot with a ruler, covered with a wet cloth and left for 30-60 min, then the mixing pot is placed on the mortar mixer fixed rack and raised to the fixed position; turn on the mixer and stir slowly for 30s (or stir by hand for 30s), then quickly place the mixed mortar in a truncated cone round mold, level it with a ruler, lift the test mold vertically, and allow the mortar to flow freely on the glass plate until it stops flowing (30s after the test mold is lifted), measure the maximum diameters of the two directions perpendicular to each other of the flowing part with a steel ruler, and take the average value as the spread over time.

[0026] As a preferred technical solution, the mixed mortar is specifically: water and cement are added to the mixing pot in sequence, the mixing pot is placed on the mortar mixer fixed rack and raised to the fixed position, the automatic mortar mixer program is started, and fine aggregate and water reducing agent are added in sequence during the mixing process to obtain the mixed mortar.

[0027] Preferably, the automatic mixing program is specifically: low-speed stirring for 60s, high-speed stirring for 30s, stopping for 90s, and then high-speed stirring for 60s.

[0028] As a preferred technical scheme, the mixed mortar is specifically: 240g of mixing water (accurate to 0.5g) is weighed in a 300ml plastic beaker according to table 1 and placed in a stirring pot; 600g of cement (accurate to 0.5g) is weighed according to table 1 and placed in the stirring pot; the stirring pot is placed on the fixed frame of the mortar mixer, and is raised to the fixed position; the automatic stirring program of the mortar mixer is started: low-speed stirring for 60s, fine aggregate is added uniformly during the last 30s, then water reducing agent is added, high-speed stirring for 30s, stopping for 90s, the mortar on the stirring blade and the pot wall is scraped into the middle with a spatula in the first 15s, and then high-speed stirring is continued for 60s to obtain the mixed mortar.

[0029] As a preferred technical scheme, the dosage of the water reducing agent is the amount of the water reducing agent added to the initial expansion degree of the mortar of 220mm±20mm.

[0030] As a preferred technical scheme, when the liquid water reducing agent is used, the solid content of the water reducing agent is converted into the solid content of the powder, and the water content of the liquid water reducing agent is subtracted from the water amount.

[0031] As a preferred technical scheme, the cement is general portland cement.

[0032] In the application, 2.36mm and 0.15mm are taken as the screening standards, which correspond to the particle size of the ISO standard sand in the reference mortar, so that the adsorption error caused by the different particle sizes of the fine aggregate and the ISO standard sand is reduced, and the accuracy of the test results is ensured.

[0033] As a preferred technical scheme, the formula is: when the amount of fine powder less than 0.075mm in the fine aggregate is ≤5%, the increment of the water reducing agent for the fine aggregate obtained by the test method is the test result, and the increment of the water reducing agent for the fine aggregate = the measured dosage of the water reducing agent of the fine aggregate - the measured dosage of the water reducing agent of the reference sand; when the amount of fine powder less than 0.075mm in the fine aggregate is >5%, the increment of the water reducing agent for the fine aggregate is the weighted average value of each part of sand as the test result, and the increment of the water reducing agent for the fine aggregate = the screening residue of the 0.15mm-2.36mm part × the dosage of the water reducing agent thereof + the screening residue of the 0.15mm part × the dosage of the water reducing agent thereof - the measured dosage of the water reducing agent of the reference sand.

[0034] As a preferred technical scheme, the dosage of the reference water reducing agent is obtained by testing the initial expansion degree of the reference mortar.

[0035] The mixing ratio of the reference mortar is shown in table 3.

[0036] Table 3,

[0037]

[0038]

[0039] Another aspect of the present application provides an application of a method for testing the adsorption amount of fine aggregate on water reducing agent, which is applied to the determination of the adsorption amount of fine aggregate on water reducing agent.

[0040] Beneficial effects:

[0041] (1) The present application tests the adsorption amount of fine aggregate on water reducing agent through a mortar expansion test, quantifies the adsorption performance of fine aggregate on water reducing agent through the increment of water reducing agent content, has high reliability, is simple and easy to operate, and is helpful for the preparation of stable performance concrete.

[0042] (2) Before mixing the mortar, the mixing pot and stirring blades are wiped to avoid the introduction of moisture error, which affects the accuracy of the adsorption effect of fine aggregate on water reducing agent, and to avoid the loss of powdered mortar raw materials due to the dry surface of the mixing pot and stirring blades, thereby ensuring the accuracy of the test method results.

[0043] (3) In the present application, 2.36 mm and 0.15 mm are used as the screening standard, which corresponds to the particle size of the standard sand in the reference mortar, thereby reducing the adsorption amount error caused by the different particle sizes of fine aggregate and standard sand, and ensuring the accuracy of the test results. DETAILED DESCRIPTION

[0044] Example 1

[0045] The embodiment 1 of the present application provides a method for testing the adsorption amount of fine aggregate on water reducing agent, which comprises the following steps:

[0046] (1) Instrument and equipment preparation;

[0047] (2) Weigh the cement, fine aggregate, water and water reducing agent raw materials;

[0048] (3) Mix the mortar by adjusting the content of water reducing agent to make the initial expansion of the mortar at the same value, obtain the mixed mortar, and record the content of water reducing agent;

[0049] (4) Calculate the adsorption amount of fine aggregate on water reducing agent according to the formula;

[0050] (5) The adsorption amount of fine aggregate on water reducing agent is characterized by the expansion of mortar and the increment of water reducing agent.

[0051] The instrument and equipment preparation is specifically: wipe the mixing pot and stirring blades with a wet cloth until the surface of the mixing pot and stirring blades is wet but without water stains.

[0052] The fine aggregate is dried at 105 DEG C to an absolute dry state and then cooled to 22 DEG C for standby.

[0053] The processing mode of the fine aggregate is that the amount of fine powder below 0.075 mm in the fine aggregate is ≤5%, and the part below 2.36 mm is taken as the fine aggregate raw material to mix mortar and perform subsequent tests.

[0054] The fine aggregate is machine-made sand (produced in Wuzhou, Guangxi).

[0055] The water is drinking water.

[0056] The water reducing agent is a liquid non-slump-retaining water-reducing polycarboxylic acid water-reducing agent mother liquor (from Guangdong Kexijie New Material Group Co., Ltd.), which is diluted with water to a solid content of 10%.

[0057] The cement is cement meeting the provisions of GB 175, and the cement is Dongguan Hongli PO42.5R.

[0058] The ISO standard sand is standard sand meeting the provisions of GB / T 17671, and the sand is Xiamen ISO standard sand.

[0059] The dosage of the water reducing agent is the dosage of the added water reducing agent to the initial spread of the mortar of 220 mm.

[0060] The formula is: fine aggregate water reducing agent dosage increase value = measured water reducing agent dosage of fine aggregate - measured water reducing agent dosage of reference sand.

[0061] The fine aggregate mortar mixing proportion is shown in Table 4.

[0062] Table 4,

[0063]

[0064] The reference mortar mixing proportion is shown in Table 5.

[0065] Table 5,

[0066]

[0067]

[0068] The spread test includes initial spread test and time-dependent spread test.

[0069] The definition of the initial spread is that the spread is tested immediately after the completion of mortar mixing; and the definition of the time-dependent spread is that the spread is tested after the mortar is stored for a certain time under the specified conditions and then mixed again according to the requirements.

[0070] The fine aggregate mortar initial spread test method specifically includes the following steps:

[0071] S1, before starting the test, wipe the stirring blade and the stirring pot with a wet cloth to make the surface wet but not with water stains;

[0072] S2, in a container with a volume of 100 mL, weigh the water reducing agent according to Table 4 (accurate to 0.02 g), and place the water reducing agent in the stirring pot; in a 300 mL plastic beaker, weigh 240 g of water according to Table 4 (accurate to 0.5 g), wash the container containing the water reducing agent with water for 3 times, and combine the washing water and the remaining water in the water reducing agent in the stirring pot; shake the stirring pot gently to mix the water reducing agent and water;

[0073] S3, weigh 600 g of cement according to Table 4 (accurate to 0.5 g) into the stirring pot; weigh 1350 g of fine aggregate (accurate to 1 g). Place the stirring pot on the fixed frame and raise it to the fixed position; start the automatic stirring program of the mortar mixer; stir at low speed for 60 s, and add the fine aggregate uniformly during the last 30 s; stir at high speed for another 30 s, stop for 90 s, and scrape the mortar on the stirring blade and pot wall into the middle with a spatula during the first 15 s, and continue to stir at high speed for 60 s; record the starting time of the mortar mixer;

[0074] S4, while mixing the mortar, place the glass plate in a horizontal position, wipe the glass plate, truncated cone round mold with a wet cloth, and place them in the center of the glass plate, cover them with a wet cloth for standby; after the stirring machine stops, take out the stirring pot, quickly wipe the glass plate and truncated cone round mold again with a wet cloth, pour the mixed mortar into the truncated cone round mold, scrape it flat with a spatula, lift the truncated cone round mold in the vertical direction, and let the mortar flow freely on the glass plate until it stops flowing (about 30 s after the mold is lifted), measure the diameters of the two directions perpendicular to each other of the flowing part with a steel ruler, and take the average value as the initial expansion degree of the fine aggregate mortar.

[0075] The fine aggregate mortar expansion degree over time test method specifically includes the following steps:

[0076] After the initial expansion degree of the fine aggregate mortar is tested, scrape the mortar into the stirring pot with a spatula, cover it with a wet cloth, and place it on the mortar mixer fixed frame after standing, raise it to the fixed position; start the stirring machine, stir at low speed for 30 s, pour the mixed mortar into the truncated cone round mold, scrape it flat with a spatula, lift the truncated cone round mold in the vertical direction, and let the mortar flow freely on the glass plate until it stops flowing (about 30 s after the mold is lifted), measure the diameters of the two directions perpendicular to each other of the flowing part with a steel ruler, and take the average value as the expansion degree of the fine aggregate mortar over time.

[0077] The reference mortar initial expansion degree test method specifically includes the following steps:

[0078] S1, before starting the test, wipe the stirring blade and the stirring pot with a wet cloth to make the surface wet but not with water stains;

[0079] S2, in a volume 100 mL of container according to Table 5, water-reducing agent (accurate to 0.02 g) is weighed, and the water-reducing agent is placed in a stirring pot; 240 g of water (accurate to 0.5 g) is weighed in a 300 mL plastic beaker according to Table 5, the container containing the water-reducing agent is washed with water for 3 times, and the washing water and the remaining water are combined in the water-reducing agent in the stirring pot; the stirring pot is shaken gently to mix the water-reducing agent and the water;

[0080] S3, 600 g of cement (accurate to 0.5 g) is weighed according to Table 5 into the stirring pot; the stirring pot is placed on a fixed frame and raised to a fixed position; the automatic stirring program of the mortar mixer is started; low-speed stirring is performed for 60 s, and the ISO standard sand is uniformly added during the last 30 s; high-speed stirring is performed for another 30 s, stopped for 90 s, and the mortar on the stirring blade and the pot wall is scraped into the middle with a spatula during the first 15 s, and high-speed stirring is continued for 60 s; the starting time of the mortar mixer is recorded;

[0081] S4, while the mortar is being mixed, the glass plate is placed in a horizontal position, the glass plate, the truncated cone round mold are wiped with a wet cloth, and they are placed in the center of the glass plate, covered with a wet cloth for standby; after the mortar mixer is stopped, the stirring pot is taken out, the glass plate and the truncated cone round mold are uniformly wiped again with a wet cloth, the mixed mortar is quickly poured into the truncated cone round mold, leveled with a spatula, the truncated cone round mold is lifted in a vertical direction, and the mortar is allowed to flow freely on the glass plate until it stops flowing (about 30 s after the mold is lifted), the diameters of the two directions perpendicular to each other of the flowing part are measured with a steel ruler, and the average value is taken as the initial expansion degree of the reference mortar.

[0082] The method for testing the expansion degree of the reference mortar over time specifically comprises the following steps:

[0083] The mortar body after the initial expansion degree of the reference mortar is tested is scraped into the stirring pot with a spatula, the stirring pot is placed on the mortar mixer fixed frame after being covered with a wet cloth, and is raised to a fixed position; the mortar mixer is started, and after slow stirring for 30 s, the mixed mortar is quickly poured into the truncated cone round mold, leveled with a spatula, the truncated cone round mold is lifted in a vertical direction, and the mortar is allowed to flow freely on the glass plate until it stops flowing (about 30 s after the mold is lifted), the diameters of the two directions perpendicular to each other of the flowing part are measured with a steel ruler, and the average value is taken as the expansion degree of the reference mortar over time.

[0084] The standing time is 60 min.

[0085] The application of the method for testing the adsorption amount of fine aggregate to water-reducing agent according to the embodiment 1 of the present application is applied to the determination of the adsorption amount of fine aggregate to water-reducing agent.

[0086] Embodiment 2-3

[0087] Embodiments 2-3 of the present application provide a method for testing the adsorption amount of fine aggregate to water reducing agent, the specific implementation is the same as embodiment 1, except that the variety and origin of the fine aggregate and the variety of the cement are different, see table 6 for details.

[0088] Performance test method

[0089] (1) The water reducing agent content of the fine aggregate and the reference sand water reducing agent content measured by the test of embodiments 1-3 are shown in table 6.

[0090] (2) The results of the adsorption amount of fine aggregate to water reducing agent in embodiments 1-3 are shown in table 6.

[0091] Table 6

[0092]

Claims

1. A method for testing the adsorption amount of fine aggregate on water reducing agent, characterized by, At least comprising the following steps: (1) instrument and equipment preparation; (2) weighing cement, fine aggregate, water and water reducing agent raw materials; (3) mixing mortar, adjusting the dosage of water reducing agent to make the initial spread of mortar at the same value, obtaining mixed mortar, and recording the dosage of water reducing agent; (4) calculating the adsorption amount of fine aggregate to water reducing agent according to the formula; (5) the adsorption amount of fine aggregate to water reducing agent is characterized by the spread of mortar and the increase of water reducing agent; the formula is: when the amount of fine powder below 0.075mm in the fine aggregate is ≤5%, the increase value of water reducing agent dosage obtained by the test method is the test result, and the increase value of water reducing agent dosage = water reducing agent dosage measured by the test - reference water reducing agent dosage; when the amount of fine powder below 0.075mm in the fine aggregate is >5%, the spread of mortar and water reducing agent value of fine aggregate mortar is the weighted average value of each part of sand as the test result, and the increase value of water reducing agent dosage = 0.15mm-2.36mm part count residue × its water reducing agent dosage + 0.15mm below part count residue × its water reducing agent dosage - reference water reducing agent dosage; the reference water reducing agent dosage is obtained by testing the initial spread of reference mortar; the treatment method of the fine aggregate is: when the amount of fine powder below 0.075mm in the fine aggregate is ≤5%, the part below 2.36mm in nominal diameter is taken as the fine aggregate raw material to mix mortar and perform subsequent test; when the amount of fine powder below 0.075mm in the fine aggregate is >5%, the fine aggregate of 0.15mm-2.36mm part and less than 0.15mm part are taken as the fine aggregate raw material to mix mortar and perform subsequent test.

2. The method for testing the adsorption amount of fine aggregate to water reducing agent according to claim 1, characterized in that, The instrument and equipment preparation is specifically: the stirring pot and stirring blade are washed, soaked and wrung dry with a wet cloth, and the surface of the stirring pot and stirring blade is wiped to be wet but without water stains.

3. The method for testing the adsorption amount of fine aggregate to water reducing agent according to claim 2, characterized in that, The test method of the initial spread of mortar is: the mixed mortar is quickly put into a truncated cone round mold, leveled with a ruler, the mold is lifted in the vertical direction, the mortar is allowed to flow freely on the glass plate until it stops flowing, the maximum diameter of the two directions perpendicular to each other of the flowing part is measured with a steel ruler, and the average value is taken as the initial spread of mortar.

4. The method for testing the adsorption amount of fine aggregate to water reducing agent according to claim 3, characterized by, The truncated cone round mold and glass plate are wiped with a wet cloth before use.

5. The method for testing the adsorption amount of fine aggregate to water reducing agent according to claim 1, characterized by, The mixed mortar is specifically: water and cement are added into the stirring pot in turn, the stirring pot is placed on the mortar mixer fixed frame, raised to the fixed position, the automatic stirring program of the mortar mixer is started, and fine aggregate and water reducing agent are added in turn during the stirring to obtain the mixed mortar.

6. The method for testing the adsorption amount of fine aggregate to water reducing agent according to claim 5, characterized by, The dosage of water reducing agent is the amount of water reducing agent added to the initial spread of mortar of 220mm±20mm.

7. The method for testing the adsorption amount of fine aggregate to water reducing agent according to claim 3, characterized by, The fine aggregate is dried at 100-110℃ to an absolute dry state, and then cooled to 18-22℃ for standby.

8. Use of the method for testing the water-reducing agent adsorption amount of fine aggregate according to any one of claims 1 to 7, characterized by, It is applied to the determination of the adsorption amount of fine aggregate to water reducing agent.

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