A method for rapidly detecting the activity index of mineral powder

Abstract

The application discloses a kind of quick detection methods of mineral powder activity.The steps are: taking activating agent and water configuration activation solution, according to GB / T 17671 "cement mortar strength test method" method, activation solution, mineral powder and sand are prepared and test block is formed, and after 15-17h in standard mortar curing box, formwork is dismantled, again, it is placed into oven and is maintained 6-8h after film coating, cooling to room temperature carries out compressive strength test, and the activity index of mineral powder is calculated by the calculation formula of compressive strength and activity index.The application utilizes alkali-sulfate and seed compound excitation characteristics, and combines high-temperature rapid curing system to quickly stimulate mineral powder activity, effectively shortens mineral powder hydration period, and the activity index detection time is shortened from original 28d to 1d by test block compressive strength, greatly improves mineral powder activity index detection efficiency, and accuracy is higher, and is suitable for promotion and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete raw material detection, and specifically relates to a rapid detection method for the activity of mineral powder. BACKGROUND

[0002] The application of mineral powder as a mineral admixture in concrete is a main way for comprehensive utilization of mineral powder, the participation of mineral powder in the cement hydration process has a significant influence on the workability, strength development, durability and volume stability of concrete, and fundamentally reduces the use of cement and increases the use rate of waste recycling. Therefore, it is of great significance to ensure that the quality of mineral powder meets the relevant technical indicators to improve the overall quality of concrete.

[0003] The activity of mineral powder directly reflects the quality of the mineral powder itself, but the detection method of the activity index of mineral powder in the concrete mixing station at present mainly uses the strength index method described in the "Ground Granulated Blast Furnace Slag for Use in Cement, Mortar and Concrete" (GB / T18046-2017), and the mortar test piece is prepared according to the molding method of the standard "Cement Mortar Strength Test Method" (GB / T17671-1999), and the curing period needs to reach 28 days to obtain the activity index of mineral powder, so the detection cycle is long and it is not suitable for the rapid production rhythm, and the related quality index detection results often have obvious hysteresis. In addition, the calculation method of the activity of mineral powder based on the mass ratio of the chemical composition of mineral powder, such as the mass coefficient (CaO+MgO+Al2O3) / (SiO2+MnO+TiO2), the activity coefficient Al2O3 / SiO2, and the alkaline coefficient (CaO+MgO) / (SiO2+Al2O3), but due to the complex influence of chemical composition on the structure characteristics of slag, these coefficients have no good correlation with the activity of mineral powder, and it has great limitations to simply use a certain ratio of chemical composition to evaluate the activity of mineral powder. Other detection methods for the activity of mineral admixtures, such as the degree of polymerization evaluation method and the hydration reaction heat method, have the disadvantages of high demand for professional equipment, harsh detection conditions, complex detection process, long detection time and the like, which are not conducive to the rapid detection in actual production application.

[0004] Therefore, in order to improve the detection efficiency of the activity of mineral powder in the process of entering the factory and make the quality of mineral powder more time-effective to guide the production of concrete, the application provides a rapid detection method for the activity of mineral powder based on the actual detection conditions and from the aspects of quick detection and clear results. SUMMARY

[0005] The purpose of the application is to provide a rapid detection method for the activity of mineral powder in order to solve the problems of long detection period and slow quality feedback response of mineral powder in the traditional strength index method.

[0006] To achieve the above purpose, the technical scheme adopted by the application is:

[0007] A rapid detection method of mineral powder activity, comprising the following steps:

[0008] 1) According to the mixing ratio, the activator and water are weighed, the activator is dissolved in water to prepare an activation solution, and the solution is cooled to room temperature after complete dissolution (the dissolution process releases heat); wherein:

[0009] The activator is a mixture of modified mineral powder hydration product, NaOH, Na2SO4 and NaAlO2, and the mass percentage of each component is: modified mineral powder hydration product 70-80%, NaOH 10-20%, Na2SO4 5-10%, and NaAlO2 5-10%;

[0010] The modified mineral powder hydration product is prepared by mixing and stirring raw materials including the following mass percentages in a high-speed mixer at 600-700 r / min for 3-4 h, and finally drying: fine mineral powder hydration product 80-90%, water glass 5-15%, and nano-SiO2 1-5%;

[0011] The fine mineral powder hydration product is a powder obtained by grinding, drying the alkali-activated mineral powder test block prepared by mixing mineral powder, NaOH and water in a ratio of 2:0.1:1, and curing in a standard curing box for more than 28 days, and its fineness is ≥500 mesh.

[0012] 2) According to the mixing ratio, the mineral powder is weighed, the activation solution and the mineral powder are mixed uniformly, then the sand is added and mixed uniformly, and the mortar preparation and test block molding are carried out according to the method and mixing ratio described in GB / T 17671 "Cement Mortar Strength Test Method";

[0013] 3) The molded test block is placed in a standard mortar curing box for curing, in order to accelerate the activity of the mineral powder, the test block is demolded after curing in the standard mortar curing box for 15-17 h, and immediately sealed, and then placed in an oven for further curing for 6-8 h;

[0014] 4) The test block is taken out of the oven, naturally cooled to room temperature, and then subjected to compressive strength test, and the activity index of the mineral powder is calculated through the functional relationship between the compressive strength of the test block and the activity index.

[0015] In the above scheme, the NaOH is a white flaky solid, the purity is ≥99.9%, the Na2SO4 is a white crystalline solid, the purity is ≥99.0%, and the NaAlO2 is a white crystalline powder, the purity is ≥93.0%. The NaOH and Na2SO4 as alkali-sulfate activator provide an alkaline environment for the mineral powder system, accelerate the dissolution of the mineral powder silicon-oxygen grid through adsorption, complexation and precipitation, and form hydrated calcium silicate and hydrated calcium aluminate; at the same time, under the coupling effect of the sulfate, the active Al2O3 in the mineral powder and the hydrated calcium aluminate combine to form hydrated calcium sulphoaluminate, which consumes a large amount of calcium and aluminum ions, in turn accelerating the hydration process of the mineral powder. The hydrolysis of NaAlO2 produces NaOH and Al(OH)3 gel, which further improves the alkalinity of the system, promotes the formation and staggered growth of AFt and C-S-H, and thus accelerates the hydration of the mineral powder. The modified mineral powder hydration product and nano-SiO2 as a crystal seed provide nucleation points for the hydration of the mineral powder, reduce the nucleation potential barrier when the hydration product changes from ions to crystals, and induce the accelerated hydration of the mineral powder. At the same time, the crystal nucleus induction effect is conducive to the orderly arrangement of the hydration product and the formation of a more compact structure, thereby improving the activity of the mineral powder.

[0016] In the above scheme, the mixing ratio of the mineral powder, sand and water in steps 1) and 2) refers to GB / T 17671 “Cement mortar strength test method”. Specifically, the mineral powder is 450±2 parts, the water is 225±1 part, and the standard sand is 1350±5 parts by mass fraction. The amount of activator added is 15±0.1 parts.

[0017] In the above scheme, the time for taking the test block out of the standard curing box and placing it into the oven in step 3) should be controlled within 10 minutes; and the oven curing temperature is 75-85℃.

[0018] In the above scheme, in step 4), the compressive strength is the 24h compressive strength; specifically, the compressive strength test time is controlled within 24h±15min from the mixing and stirring time of the activation liquid and the mineral powder.

[0019] In the above scheme, in step 4), the calculation formula of the activity index of the mineral powder is:

[0020] R=A*ln(F-18)+B

[0021] Wherein, R is the activity index of the mineral powder, F is the 24h compressive strength of the mineral mortar test block, and A and B are correction coefficients related to the components of the activator.

[0022] A=-20+60X,B=185-200X.

[0023] Wherein, X is the mass percentage of the modified mineral powder hydration product in the activator.

[0024] Preferably, A is 22-28 and B is 25-45.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. The present application is based on the active characteristics of the water hardness of the mineral powder, uses the composite activation characteristics of alkali-sulfate and crystal seeds, and through the addition of an activator, forms a mineral powder mortar test block based on the standard method, and combines a high-temperature rapid curing system to rapidly activate the mineral powder, and through the compressive strength of the test block, the activity is determined instead of the traditional strength index method to efficiently and accurately represent the activity of the mineral powder, effectively shortens the mineral powder hydration period, shortens the mineral powder activity index detection period from the traditional 28d to 1d, greatly improves the detection efficiency of the mineral powder activity index, has high accuracy, does not need to increase other detection equipment, is simple in method, easy to operate, and has wide adaptability.

[0027] 2. The detection method of the present application has good timeliness in evaluating the quality of the mineral powder, which is beneficial to further guide the production of concrete and avoid quality accidents. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0029] In the following examples, 10 kinds of mineral powder samples were selected for rapid detection, and the related technical indexes are shown in Table 1.

[0030] Table 1. Performance test results of 10 kinds of mineral powder samples to be tested

[0031]

[0032]

[0033] Example 1

[0034] A rapid detection method of a mineral powder activity index, comprising the following steps:

[0035] 1) 15 parts of an activator and 225 parts of water are weighed according to the mixing ratio, the activator is dissolved in the water to prepare an activation solution, and the solution is cooled to room temperature after complete dissolution; wherein:

[0036] The activator is a mixture of modified mineral powder hydration products, NaOH, Na2SO4 and NaAlO2, and the mass percentage of each component is: modified mineral powder hydration products 75%, NaOH 10%, Na2SO4 10%, and NaAlO2 5%.

[0037] The modified mineral powder hydration product is prepared by mixing and stirring raw materials in a high-speed mixer at 700 r / min for 4 h, and finally drying, wherein the raw materials include, by mass percentage, 90% of the ground mineral powder hydration product, 5% of water glass, and 5% of nano-SiO2.

[0038] The ground mineral powder hydration product is a powder prepared by grinding and drying an alkali-activated mineral powder test block prepared by mixing mineral powder, NaOH and water in a ratio of 2:0.1:1, and then curing in a standard curing box for more than 28 days, wherein the fineness of the powder is ≥500 mesh.

[0039] 2) 450 parts of mineral powder were weighed according to the mixing ratio, the activated solution obtained in step 1) and the mineral powder were added to a mortar mixer, and the activated solution and the mineral powder were mixed uniformly by sufficient stirring, and then 1350 parts of standard sand were added for mixing, and mortar preparation and test block molding were performed according to the method described in GB / T 17671 "Cement Mortar Strength Test Method"; wherein:

[0040] The mineral powder is 1# mineral powder, 2# mineral powder, 3# mineral powder, 4# mineral powder, 5# mineral powder, 6# mineral powder, 7# mineral powder, 8# mineral powder, 9# mineral powder or 10# mineral powder in Table 1, and the above 10 kinds of mineral powders are detected respectively.

[0041] 3) The molded test block was placed in a standard mortar curing box for curing, in order to accelerate the activation of the mineral powder, the test block was demolded after curing in the standard mortar curing box for 16 h, and immediately sealed with plastic film, and then placed in an oven for further curing at 80℃ for 7 h; wherein the time from taking out the test block from the standard curing box to placing it in the oven should be controlled within 10 min.

[0042] 4) The test block was taken out of the oven and naturally cooled to room temperature, and then subjected to 24 h compressive strength test, and the activity index of the mineral powder was calculated through the functional relationship between the 24 h compressive strength of the test block and the activity index. Wherein:

[0043] The calculation formula of the activity index of the mineral powder is:

[0044] R = 25 * ln (F-18) + 35

[0045] Wherein, R is the activity index of the mineral powder, and F is the 24 h compressive strength of the mineral mortar test block.

[0046] The activity indexes of the 10 kinds of mineral powders obtained in this example were compared with the activity indexes obtained based on the traditional strength index method, wherein the detection of the activity index R was carried out according to the method described in Appendix A of "Ground Granulated Blast Furnace Slag for Use in Cement, Mortar and Concrete" (GB / T18046-2017). The specific test results are shown in Table 2.

[0047] Table 2 The results of activity index of 10 kinds of mineral powder by the method of example 1 and traditional method based on strength index

[0048]

[0049]

[0050] As shown in Table 2, the activity index obtained by the method is almost the same as the activity index R obtained by the traditional method based on strength index, with a maximum error of 2%, and the results are accurate and reliable, and the detection period of the activity index can be significantly shortened, and the accurate determination of the activity index of the mineral powder can be realized in 24h.

[0051] Example 2

[0052] The detection method of example 2 is substantially the same as that of example 1, except that the components of the activator are adjusted as follows: modified mineral powder hydration product 70%, NaOH 20%, Na2SO4 5%, and NaAlO2 5%.

[0053] The calculation formula of the activity of the mineral powder in step 4) is:

[0054] R = 22 * ln (F-18) + 45

[0055] The activity index of the mineral powder obtained in this example is compared with the activity index based on the strength index, and the results are shown in Table 3.

[0056] Table 3 The results of activity index of 10 kinds of mineral powder by the method of example 2 and traditional method based on strength index

[0057] Class 24 h compressive strength / MPa Example 2 activity index R / % Standard method 28 d activity index / % 1# ground granulated blast furnace slag 22.1 76 77 2# ground granulated blast furnace slag 22.9 80 80 3# ground granulated blast furnace slag 24.2 85 86 4# ground granulated blast furnace slag 28.7 97 97 5# ground granulated blast furnace slag 29.7 99 99 6# ground granulated blast furnace slag 30.6 101 101 7# ground granulated blast furnace slag 31.1 102 102 8# ground granulated blast furnace slag 32.2 103 104 9# ground granulated blast furnace slag 35.8 108 109 10# ground granulated blast furnace slag 37.4 110 110

[0058] As shown in Table 3, the 24h activity index of example 2 and the activity index obtained by the traditional strength index method can achieve comparable detection results.

[0059] Example 3

[0060] The detection method of example 2 is substantially the same as that of example 1, except that the components of the activator are adjusted as follows: modified mineral powder hydration product 80%, NaOH 10%, Na2SO4 5%, and NaAlO2 5%.

[0061] The calculation formula of the activity of the mineral powder in step 4) is:

[0062] R = 28 * ln (F-18) + 25

[0063] The activity index of the mineral powder obtained in this example is compared with the activity index based on the strength index, and the results are shown in Table 3.

[0064] Table 4 Activity index detection results of 10 kinds of mineral powder by the method of example 3 and the traditional strength index method

[0065] Class 24 h compressive strength / MPa Example 1 activity index / % Standard method 28 d activity index / % 1# ground granulated blast furnace slag 24.3 76 77 2# ground granulated blast furnace slag 25.4 81 80 3# ground granulated blast furnace slag 26.8 86 86 4# ground granulated blast furnace slag 31.2 97 97 5# ground granulated blast furnace slag 32.1 99 99 6# ground granulated blast furnace slag 32.9 101 101 7# ground granulated blast furnace slag 33.7 102 102 8# ground granulated blast furnace slag 34.5 103 104 9# ground granulated blast furnace slag 37.9 109 109 10# ground granulated blast furnace slag 38.6 110 110

[0066] As can be seen from Table 4, the 24h activity index of example 3 can achieve comparable detection results compared with the activity index obtained by the traditional strength index method.

[0067] Comparative example 1

[0068] The detection method of comparative example 1 is basically the same as that of example 1, except that the modified mineral powder hydration product in the activator component is replaced by a finely ground mineral powder hydration product, and the others remain the same.

[0069] The calculation formula of the activity of the mineral powder in step 4) is:

[0070] R = 25 * ln (F-18) + 35

[0071] The activity index analysis results of the mineral powder obtained in this comparative example are compared with the activity index R based on the strength index method, and the results are shown in Table 5.

[0072] Table 5 Activity index detection results of 10 kinds of mineral powder by the method of comparative example 1 and the traditional strength index method

[0073] Class 24 h compressive strength / MPa Comparative example 1 activity index R / % Standard method 28 d activity index / % 1# ground granulated blast furnace slag 21.6 67 77 2# ground granulated blast furnace slag 23.4 77 80 3# ground granulated blast furnace slag 23.9 79 86 4# ground granulated blast furnace slag 27.6 91 97 5# ground granulated blast furnace slag 28.2 93 99 6# ground granulated blast furnace slag 29.3 96 101 7# ground granulated blast furnace slag 30.1 97 102 8# ground granulated blast furnace slag 31.2 99 104 9# ground granulated blast furnace slag 34.1 104 109 10# ground granulated blast furnace slag 35.2 106 110

[0074] As can be seen from Table 5, the obtained 24h activity index is overall lower than that of example 1, and there is a large difference with the activity index R obtained by the traditional strength index method, indicating that when the modified mineral powder hydration product is not used in the activator, the activity of the mineral powder cannot be fully reflected, and the activity index measured by the rapid detection method is significantly lower.

[0075] The above examples are only for clearly illustrating the examples made, and are not limited to the embodiments. Other different forms of changes or variations can be made on the basis of the above description for those skilled in the art, and here it is not necessary and impossible to exhaust all the embodiments, so the obvious changes or variations still within the protection scope of the present application.

Claims

1. A rapid detection method for the activity of mineral powder, characterized in that, Includes the following steps: 1) Weigh the activator and water according to the mixing ratio, dissolve the activator in the water to prepare an activation solution, and wait for the solution to completely dissolve and cool to room temperature; wherein: The activator is a mixture of modified mineral powder hydration product, NaOH, Na2SO4, and NaAlO2, with the following mass percentages: modified mineral powder hydration product 70-80%, NaOH 10-20%, Na2SO4 5-10%, and NaAlO2 5-10%. The modified mineral powder hydration product comprises the following raw materials in the following mass percentages: 80-90% finely ground mineral powder hydration product, 5-15% water glass, and 1-5% nano-SiO2; it is obtained by mixing and stirring the raw materials in a high-speed mixer at 600-700 r / min for 3-4 h, and finally drying. The hydration product of the finely ground mineral powder is obtained by mixing mineral powder, NaOH and water in a ratio of 2:0.1:1, preparing alkali-activated mineral powder test blocks, curing them in a standard curing chamber for more than 28 days, and then grinding and drying them to obtain powder with a fineness ≥500 mesh. 2) Weigh the mineral powder according to the mix proportion, mix the activation solution and mineral powder thoroughly, then add sand and mix thoroughly. Prepare the mortar and form test blocks according to the method and mix proportion described in GB / T 17671 "Test Method for Strength of Cement Mortar"; wherein: by mass parts, mineral powder 450±2 parts, water 225±1 parts, standard sand 1350±5 parts; activator added amount is 15±0.1 parts; 3) Place the molded test block into a standard mortar curing box for curing. After curing for 15-17 hours, remove the mold and seal it immediately. Then place it in an oven for another 6-8 hours of curing. 4) Remove the test block from the oven and allow it to cool naturally to room temperature. Then, conduct a 24-hour compressive strength test. Calculate the activity index of the mineral powder by using the functional relationship between the 24-hour compressive strength of the test block and the activity index.

2. The method according to claim 1, characterized in that, In step 3), the time from removing the test block from the standard curing chamber to placing it in the oven should be controlled within 10 minutes; the curing temperature of the oven is 75-85℃.

3. The method according to claim 1, characterized in that, In step 4), the compressive strength test time is calculated from the time of mixing and stirring the activation solution and mineral powder, and is controlled within 24h±15min.

4. The method according to claim 1, characterized in that, In step 4), the formula for calculating the activity index of the mineral powder is: R = A ln(F-18)+B in: R The activity index of the mineral powder; F represents the 24-hour compressive strength of the mineral powder mortar test block; A and B are correction coefficients, A = -20 + 60X, B = 185 - 200X, where X is the mass percentage of the modified mineral powder hydration product in the activator.

5. The method according to claim 4, characterized in that, Value A ranges from 22 to 28, and value B ranges from 25 to 45.

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