Testing method for evaluating residual hydration capability of cementing material in long-age concrete
By preparing and testing clean slurry specimens for cementitious fine powder and quartz sand fine powder in long-term concrete, the problem that the existing technology is difficult to directly quantify and characterize the residual hydration capacity of cementitious material in long-term concrete is solved, and a simple and reliable test method is achieved, reducing cost and complexity.
Patent Information
- Application Number
- CN202411805751.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-10
- Publication Date
- 2025-02-28
AI Technical Summary
The prior art is difficult to directly quantify the residual hydration capacity of cemented materials in long-term concrete, and the existing NMR test is expensive, complex in operation and large errors.
By preparing cementitious material fine powder and quartz sand fine powder in long-term concrete, replacing cement, preparing slurry test pieces, after standard curing to the prescribed age period, the compressive strength is tested and the residual hydration capacity of the cementitious material is calculated.
It has achieved simple and reliable evaluation of the residual hydration capacity of cemented materials in long-term concrete. The principles are correct, the logic is clear, the results are reliable, the steps are simple, the technical and equipment requirements are low, and the testing costs are low.
Smart Images
Figure CN119534128A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of building material performance testing, in particular to a testing method for evaluating the residual hydration capacity of cementitious materials in long-aged concrete. Background Art
[0002] Many concrete dams at home and abroad have been in service for decades. Maintaining the stability of the built dams and fully ensuring the safe operation of dam projects have become important tasks for the future development of water conservancy and hydropower. The performance evolution prediction and service status evaluation of long-term concrete are important links in dam maintenance work. The residual hydration capacity of cementitious materials is the key to affecting the performance evolution and service status of long-term concrete. Therefore, the testing and evaluation of the residual hydration capacity of cementitious materials in long-term concrete is crucial.
[0003] Residual hydration capacity refers to the ability of cementitious materials in long-term concrete to still undergo hydration reactions, which mainly depends on the degree of cement hydration and the degree of pozzolanic reaction of mineral admixtures. At present, there is no method to directly quantify the residual hydration capacity of cementitious materials in long-term concrete.
[0004] The existing nuclear magnetic resonance (NMR) technology can indirectly evaluate the residual hydration capacity of cementitious materials by testing and analyzing the hydration degree of cement. However, NMR testing is expensive, requires high operation, and is difficult to analyze. In addition, the cementitious materials of concrete are complex and usually contain one or more admixtures such as cement and fly ash, slag powder, and silica powder. Long-aged concrete is often affected by factors such as carbonization, resulting in large errors in the analysis of the degree of hydration. Summary of the invention
[0005] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a simple and reliable test method for evaluating the residual hydration capacity of cementitious materials in long-aged concrete.
[0006] The purpose of the present invention is achieved through the following technical solutions:
[0007] A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete comprises the following steps:
[0008] (1) Preparing fine powder of cementitious materials and fine powder of quartz sand for long-term concrete;
[0009] (2) replacing cement in long-age concrete with finely ground cementitious material powder and finely ground quartz sand powder in a certain proportion to form a mixed material;
[0010] (3) Prepare a slurry specimen by mixing the mixed material with water, and prepare a slurry specimen by mixing cement with water;
[0011] (4) Curing the pure slurry specimens under standard curing conditions to the specified age;
[0012] (5) Test the compressive strength of the pure slurry specimen;
[0013] (6) Based on the measured compressive strength, calculate the residual hydration capacity of the cementitious material in the long-term concrete.
[0014] Furthermore, the method for preparing the fine powder of cementitious material in the long-aged concrete in step (1) is as follows: crushing the long-aged concrete specimen, picking out the hardened cementitious material slurry, drying it in an oven at 60°C to 105°C, grinding it in a corundum mortar, controlling the grinding intensity to minimize the fine aggregates contained in the hardened cementitious material slurry from being ground simultaneously, and then passing it through a 45μm square hole sieve to retain the fine powder under the sieve.
[0015] Furthermore, the preparation method of the quartz sand fine powder in step (1) is: grinding the dry quartz sand by a vibration mill, then passing it through a 45 μm square hole sieve, and retaining the fine powder under the sieve.
[0016] Furthermore, in step (2), the cementitious material powder and the quartz sand powder in the long-age concrete replace cement in a ratio of 10 to 30%, respectively, and the replacement ratio of the two remains consistent.
[0017] Furthermore, the preparation steps of the clean slurry specimen in step (3) include:
[0018] (a) Weighing: Weigh one part of mixed material or cement and half part of water by mass;
[0019] (b) Mixing: Add one part of the mixed material or cement and half part of water into a slurry mixer and mix well;
[0020] (c) Moulding: Place the mixed slurry into a cubic test mould with a side length of 40 mm;
[0021] (d) Vibration: The molded specimen is vibrated on a vibration table for 30 seconds to expel air bubbles;
[0022] (e) Scraping: Use a scraper to smooth the surface of the specimen.
[0023] Furthermore, the slurry curing conditions in step (4) are a temperature of 20±2° C., a relative humidity of not less than 95%, and a curing period of 28 days.
[0024] Furthermore, in step (5), the compressive strength of the pure slurry is tested with the number of specimens tested in each group being no less than 3, and the test results are averaged.
[0025] Furthermore, the calculation method of the residual hydration capacity of the cementitious material in the long-aged concrete in step (6) is:
[0026]
[0027] Where: K is the evaluation index of residual hydration capacity of cementitious materials in long-term concrete;
[0028] C0——Strength of cement paste specimen, MPa;
[0029] C1——Strength of the pure paste specimen of cement and fine powder of cementitious material in long-term concrete, MPa;
[0030] C2——Strength of the pure slurry specimen of cement and quartz sand powder mixture, MPa.
[0031] Compared with the prior art, the present invention has the following beneficial effects:
[0032] The present invention regards the hydration capacity of cement as 100%, quartz sand as an inert material with a hydration capacity of 0, and the hydration capacity of cementitious materials in long-age concrete is between the two. Based on the good correlation between the hydration capacity and strength of cementitious materials, the present invention replaces cement with quartz sand powder and cementitious materials powder in long-age concrete in a certain proportion, and then prepares slurry specimens, and tests the compressive strength after standard curing to the specified age. Finally, the compressive strength is used to calculate and obtain a quantitative index for evaluating the residual hydration capacity of cementitious materials in long-age concrete. Based on the good correlation between the hydration capacity and strength of cementitious materials, the present invention uses the compressive strength of the designed specimen to calculate and obtain a quantitative index for evaluating the residual hydration capacity of cementitious materials in long-age concrete. The present invention has correct principles, clear logic, reliable results, simple steps, low requirements for technology and equipment, and low testing costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 The present invention is a flow chart of a test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete. DETAILED DESCRIPTION
[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0035] Embodiment 1
[0036] This example tests and evaluates the residual hydration capacity of cementitious materials in 60-year-old dam concrete of land water engineering. Figure 1 , including the following steps:
[0037] (1) Crushing the concrete core sample of the 60-year-old dam of the Lushui Project, picking out the hardened cementitious material slurry, drying it in an oven at 105°C, grinding it in a corundum mortar, controlling the grinding intensity, minimizing the fine aggregates contained in the hardened cementitious material slurry from being ground simultaneously, and then passing it through a 45 μm square hole sieve, retaining the fine powder under the sieve; drying the quartz sand in an oven at 105°C, grinding it using a vibration mill, and then passing it through a 45 μm square hole sieve, retaining the fine powder under the sieve;
[0038] (2) Substituting cement (Jiahua 42.5 medium heat silicate cement) with finely ground cementitious material powder and finely ground quartz sand powder in proportions of 10%, 20%, and 30%, respectively, to prepare a mixed material;
[0039] (3) Weigh 450g of mixed material and 225g of water, add them to the slurry mixer and mix them evenly; similarly, weigh 450g of cement and 225g of water, add them to the slurry mixer and mix them evenly. Put the mixed slurry into a cubic test mold with a side length of 40mm for molding, with the number of moldings per group not less than 3. Then put the test mold on the vibration table and vibrate for 30s to expel bubbles. Finally, use a scraper to smooth the surface of the test piece.
[0040] (4) Place the formed pure slurry specimen with the mold in a standard curing box (temperature 20±2℃, relative humidity not less than 95%), remove the mold after 3 days, and then continue to cure in the standard curing box until the age of 28 days;
[0041] (5) The compressive strength of the specimens that have reached the age is tested. The number of specimens in each group shall not be less than 3, and the results shall be averaged. The compressive strength of each group of specimens is shown in Table 1.
[0042] Table 1 Compressive strength of pure slurry specimens
[0043]
[0044]
[0045] (6) Based on the measured compressive strength, calculate the residual hydration capacity K of the cementitious material in the long-term concrete.
[0046]
[0047] Where: K is the evaluation index of residual hydration capacity of cementitious materials in long-term concrete;
[0048] C0——Strength of cement paste specimen, MPa;
[0049] C1——Strength of the pure paste specimen of cement and fine powder of cementitious material in long-term concrete, MPa;
[0050] C2——Strength of the pure slurry specimen of cement and quartz sand powder mixture, MPa.
[0051] The test results of the residual hydration capacity of cementitious materials in the 60-year-old dam concrete of the Lushui Project are shown in Table 2.
[0052] Table 2 Test results of residual hydration capacity of cementitious materials
[0053]
[0054]
[0055] From the results in Table 2, it can be seen that according to the method of the present invention, the proportion of cementitious material powder replacing cement in the 60-year-old dam concrete of the land water project is 10-30%, and the measured residual hydration capacity index value of the cementitious material is about 13%.
[0056] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.
Claims
1. A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete, characterized in that: The following steps are involved: (1) Preparing fine powder of cementitious materials and fine powder of quartz sand for long-term concrete; (2) replacing cement in long-age concrete with finely ground cementitious material powder and finely ground quartz sand powder in a certain proportion to form a mixed material; (3) Prepare a slurry specimen by mixing the mixed material with water, and prepare a slurry specimen by mixing cement with water; (4) Curing the pure slurry specimens under standard curing conditions to the specified age; (5) Test the compressive strength of the pure slurry specimen; (6) Based on the measured compressive strength, calculate the residual hydration capacity of the cementitious material in the long-term concrete.
2. A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete according to claim 1, characterized in that: The method for preparing the fine powder of cementitious material in the long-aged concrete in step (1) is as follows: crushing the long-aged concrete specimen, picking out the hardened cementitious material slurry, drying it at 60° C. to 105° C., grinding it in a corundum mortar, controlling the grinding intensity to minimize the fine aggregates contained in the hardened cementitious material slurry from being ground simultaneously, and then passing it through a 45 μm square hole sieve to retain the fine powder under the sieve.
3. A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete according to claim 1, characterized in that: The preparation method of the quartz sand fine powder in step (1) is: dry quartz sand is ground by a vibration mill, and then passed through a 45 μm square hole sieve, and the fine powder under the sieve is retained.
4. A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete according to claim 1, characterized in that: In step (2), the cementitious material powder and the quartz sand powder replace cement in the long-term concrete in a ratio of 10 to 30%, and the replacement ratio of the two is kept consistent.
5. A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete according to claim 1, characterized in that: The preparation steps of the clean slurry specimen in step (3) include: (a) Weighing: Weigh one part of mixed material or cement and half part of water by mass; (b) Mixing: Add one part of the mixed material or cement and half part of water into a slurry mixer and mix well; (c) Moulding: Place the mixed slurry into a cubic test mould with a side length of 40 mm; (d) Vibration: The molded specimen is vibrated on a vibration table for 30 seconds to expel air bubbles; (e) Scraping: Use a scraper to smooth the surface of the specimen.
6. A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete according to claim 1, characterized in that: The curing conditions of the pure slurry in step (4) are a temperature of 20±2° C., a relative humidity of not less than 95%, and a curing period of 28 days.
7. A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete according to claim 1, characterized in that: In step (5), the compressive strength of the pure slurry is tested with a number of specimens of no less than 3 for each group, and the test results are averaged.
8. A test method for evaluating the residual hydration capacity of cementitious materials in long-term concrete according to claim 1, characterized in that: The calculation method of the residual hydration capacity of the cementitious material in the long-aged concrete in step (6) is: Where: K is the evaluation index of residual hydration capacity of cementitious materials in long-term concrete; C0——Strength of cement paste specimen, MPa; C1——Strength of the pure paste specimen of cement and fine powder of cementitious material in long-term concrete, MPa; C2——Strength of the pure slurry specimen of cement and quartz sand powder mixture, MPa.