Method for estimating cement strength from cement soundness test cubes

Abstract

The present application relates to cement testing technical field, especially cement stability test cake calculates cement strength's method, including the following steps: step 1, preparation material, preparation cement, pour into water after stirring, make cement standard consistency neat paste, take out a part of the prepared cement standard consistency neat paste, divide into equivalent two cement paste;Step 2, making test cake, the cement paste of step 1 is formed into spherical shape, is placed on the glass plate that is coated with a layer of butter in advance, then gently vibrates on the tabletop, and simultaneously through knife from the periphery to the center, so that the cement paste forms a circular test cake with a diameter of 70mm to 80mm, a center thickness of about 10mm and a gradually thin edge;The cement stability is tested by test cake method, and then the pressure value of the test cake is measured by the pressure testing machine, and then the linear relationship value K is brought in, so that the strength of the cement can be calculated, a set of process two tests are completed at the same time, a large amount of time and cost are saved.

Description

Technical Field

[0001] This invention relates to the field of cement testing technology, and in particular to a method for estimating cement strength using cement stability test biscuits. Background Technology

[0002] Cement stability, also known as "cement volume stability," is one of the important indicators of cement quality. It reflects the uniformity of volume change during the setting and hardening process of cement. If cement contains excessive free lime, magnesium oxide, or sulfur trioxide, uneven volume changes will occur during setting and hardening, resulting in unstable phenomena such as cracking, bending, brittleness, and collapse.

[0003] Cement strength is an important indicator for evaluating cement quality and is the basis for classifying cement strength grades; cement strength refers to the ability of a hardened cement mortar specimen to withstand external force damage.

[0004] Currently, cement requires stability and strength tests during construction. After using one stability testing procedure, another procedure is needed to test the cement strength (compressive and flexural strength). Both procedures are time-consuming and costly. Therefore, it is necessary to propose a technical solution to address these issues. Summary of the Invention

[0005] To overcome the shortcomings mentioned above, the present invention aims to provide a technical solution that can solve the above problems.

[0006] The method for estimating cement strength using cement soundness test biscuits includes the following steps:

[0007] Step 1: Prepare materials. Prepare cement, pour in water and stir to make cement paste of standard consistency. Take out a portion of the prepared cement paste of standard consistency and divide it into two equal portions.

[0008] Step 2, make a test cake. Take a portion of cement slurry from Step 1, roll it into a ball, place it on a glass plate that has been coated with butter, and then gently shake it on the table while simultaneously spreading it from the outside to the center with a knife, so that the cement slurry forms a round test cake with a diameter of 70mm to 80mm, a thickness of about 10mm in the center and gradually thinning at the edges.

[0009] Step 3, curing the test cakes: Place the test cakes prepared in Step 2 into a humid curing chamber and cure for 24±2 hours;

[0010] Step 4: Boiling test cake. Take the test cake out of the curing chamber and remove it from the glass plate. Observe the appearance of the test cake for any defects. If there are no defects such as cracks or warping, place the test cake on the test rack of the boiling chamber for boiling.

[0011] Step 5: Test the stability of the test cake. After boiling, open the lid and wait for the test cake to cool to room temperature. Take out the test cake for observation and judgment. When no cracks are found in the test cake by visual inspection and the bottom surface of the test cake is not bent when measured with a ruler, the cement stability of the test cake is considered to be qualified.

[0012] Step 6: Check the pressure value of the test cake. Prepare a steel ring with a diameter of 50-60 mm and an inner diameter of 30 cm. Place the qualified cement test cake on the steel ring, and then place the test cake and the steel ring under the pressure ball of the pressure testing machine. At this time, the press applies pressure, and read and record the pressure value.

[0013] Step 7: Perform cement compressive and flexural tests. Perform cement compressive and flexural tests on another cement slurry from Step 1. This cement slurry is made into test blocks according to the specifications, placed in a moisture curing chamber for 28 days, and then taken out. The distance between supports when the specimen breaks is obtained by a flexural testing machine, and the ultimate load of the specimen is obtained by a compression testing machine.

[0014] Step 8: Obtain the bending tensile strength of the specimen. Substitute the support distance and ultimate load data obtained in Step 7 into the specimen bending tensile strength formula: Specimen bending tensile strength = (ultimate load × support distance) / (spectrum width × specimen height × specimen height), calculate and record the specimen bending tensile strength value;

[0015] Step 9: Establish a linear relationship. Following the above method, perform the same operation on cement of different grades to obtain multiple sets of cement soundness pressure values ​​and cement flexural strength values. Perform linear correlation data processing on the pressure values ​​and flexural strength values, and finally obtain the linear relationship value K between cement soundness pressure value and cement compressive and flexural strength, thus obtaining the calculation formula for cement strength by estimating cement strength from cement soundness test cakes.

[0016] Preferably, in step 6, before placing the test cake on the steel ring, a shim is placed under the test cake, and then the test cake with the shim is placed on the steel plate.

[0017] Preferably, the flexural tensile strength of the specimen is measured as the average of three specimens. When the specimen with the highest strength is greater than 15% of the specimen with the median strength, or when the specimen with the lowest strength is less than 15% of the specimen with the median strength, the median value is taken. When the specimen with the highest strength is greater than 15% of the specimen with the median strength and the specimen with the lowest strength is less than 15% of the specimen with the median strength, the test is invalid.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] The stability of cement is tested by using a test pat method, and the pressure value of the test pat is measured by a pressure testing machine. Then, the strength of the cement can be calculated by substituting the linear relationship value K. This allows two tests to be completed simultaneously in one process, saving a lot of time and cost.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In this embodiment of the invention, the method for estimating cement strength using cement stability test patties includes the following steps:

[0023] Step 1: Prepare materials. Prepare cement, pour in water and stir to make cement paste of standard consistency. Take out a portion of the prepared cement paste of standard consistency and divide it into two equal portions.

[0024] Step 2, make a test cake. Take a portion of cement slurry from Step 1, roll it into a ball, place it on a glass plate that has been coated with butter, and then gently shake it on the table while simultaneously spreading it from the outside to the center with a knife, so that the cement slurry forms a round test cake with a diameter of 70mm to 80mm, a thickness of about 10mm in the center and gradually thinning at the edges.

[0025] Step 3, curing the test cakes: Place the test cakes prepared in Step 2 into a humid curing chamber and cure for 24±2 hours;

[0026] Step 4: Boiling test cake. Take the test cake out of the curing chamber and remove it from the glass plate. Observe the appearance of the test cake for any defects. If there are no defects such as cracks or warping, place the test cake on the test rack of the boiling chamber for boiling.

[0027] Step 5: Test the stability of the test cake. After boiling, open the lid and wait for the test cake to cool to room temperature. Take out the test cake for observation and judgment. When no cracks are found in the test cake by visual inspection and the bottom surface of the test cake is not bent when measured with a ruler, the cement stability of the test cake is considered to be qualified.

[0028] Step 6: Check the pressure value of the test cake. Prepare a steel ring with a diameter of 50-60 mm and an inner diameter of 30 cm. Place the qualified cement test cake on the steel ring, and then place the test cake and the steel ring under the pressure ball of the pressure testing machine. At this time, the press applies pressure, and read and record the pressure value.

[0029] Step 7: Perform cement compressive and flexural tests. Perform cement compressive and flexural tests on another cement slurry from Step 1. This cement slurry is made into test blocks according to the specifications, placed in a moisture curing chamber for 28 days, and then taken out. The distance between supports when the specimen breaks is obtained by a flexural testing machine, and the ultimate load of the specimen is obtained by a compression testing machine.

[0030] Step 8: Obtain the bending tensile strength of the specimen. Substitute the support distance and ultimate load data obtained in Step 7 into the specimen bending tensile strength formula: Specimen bending tensile strength = (ultimate load × support distance) / (spectrum width × specimen height × specimen height), calculate and record the specimen bending tensile strength value;

[0031] Step 9: Establish a linear relationship. Following the above method, perform the same operation on different grades of cement to obtain multiple sets of cement sounding pressure values ​​and cement flexural strength values, as shown in Table 1:

[0032]

[0033] Table 1

[0034] By performing linear correlation data processing on the pressure value and flexural strength value, the linear relationship value K between the cement stability pressure value and the cement compressive and flexural strength is finally obtained, and the calculation formula for estimating the cement strength from the cement stability test cake is obtained.

[0035] Preferably, in step 6, before placing the test cake on the steel ring, a shim is placed under the test cake, and then the test cake with the shim is placed on the steel plate.

[0036] Preferably, the flexural tensile strength of the specimen is measured as the average of three specimens. When the specimen with the highest strength is greater than 15% of the specimen with the median strength, or when the specimen with the lowest strength is less than 15% of the specimen with the median strength, the median value is taken. When the specimen with the highest strength is greater than 15% of the specimen with the median strength and the specimen with the lowest strength is less than 15% of the specimen with the median strength, the test is invalid.

[0037] This application obtains two identical cement slurries. One slurry is used to test the cement stability using the slurry test cake method, and the pressure value of the slurry is measured using a pressure testing machine. The other slurry is used to perform cement compressive and flexural strength tests to obtain the cement strength. Then, by performing linear correlation data processing on the pressure value and flexural strength value, a linear relationship value K is obtained. In subsequent cement slurry stability and strength tests, only the cement stability is tested using the slurry test cake method, and the pressure value of the slurry is measured using a pressure testing machine. Then, by substituting the linear relationship value K, the cement strength can be calculated. This allows two tests to be completed simultaneously in one process, saving a significant amount of time and cost.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for estimating cement strength using cement soundness test biscuits, characterized in that, Includes the following steps: Step 1: Prepare materials. Prepare cement, pour in water and stir to make cement paste of standard consistency. Take out a portion of the prepared cement paste of standard consistency and divide it into two equal portions. Step 2, make a test cake. Take a portion of cement slurry from Step 1, roll it into a ball, place it on a glass plate that has been coated with butter, and then gently shake it on the table while simultaneously spreading it from the outside to the center with a knife, so that the cement slurry forms a round test cake with a diameter of 70mm to 80mm, a thickness of about 10mm in the center and gradually thinning at the edges. Step 3, curing the test cakes: Place the test cakes prepared in Step 2 into a humid curing chamber and cure for 24±2 hours; Step 4: Boiling test cake. Take the test cake out of the curing chamber and remove it from the glass plate. Observe the appearance of the test cake for any defects. If there are no cracks or warping defects, place the test cake on the test rack in the boiling chamber for boiling. Step 5: Test the stability of the test cake. After boiling, open the lid and wait for the test cake to cool to room temperature. Take out the test cake for observation and judgment. When no cracks are found in the test cake by visual inspection and the bottom surface of the test cake is not bent when measured with a ruler, the cement stability of the test cake is considered to be qualified. Step 6: Check the pressure value of the test cake. Prepare a steel ring with a diameter of 50-60 mm and an inner diameter of 30 cm. Place the qualified cement test cake on the steel ring, and then place the test cake and the steel ring under the pressure ball of the pressure testing machine. At this time, the press applies pressure, and read and record the pressure value. Step 7: Perform cement compressive and flexural tests. Perform cement compressive and flexural tests on another cement slurry from Step 1. This cement slurry is made into test blocks according to the specifications, placed in a moisture curing chamber for 28 days, and then taken out. The distance between supports when the specimen breaks is obtained by a flexural testing machine, and the ultimate load of the specimen is obtained by a compression testing machine. Step 8: Obtain the bending tensile strength of the specimen. Substitute the support distance and ultimate load data obtained in Step 7 into the specimen bending tensile strength formula: Specimen bending tensile strength = (ultimate load × support distance) / (spectrum width × specimen height × specimen height), calculate and record the specimen bending tensile strength value; Step 9: Establish a linear relationship. Following the above method, perform the same operation on cement of different grades to obtain multiple sets of cement soundness pressure values ​​and cement flexural strength values. Perform linear correlation data processing on the pressure values ​​and flexural strength values, and finally obtain the linear relationship value K between cement soundness pressure value and cement compressive and flexural strength, thus obtaining the calculation formula for cement strength by estimating cement strength from cement soundness test cakes.

2. The method for estimating cement strength using cement stability test patches according to claim 1, characterized in that, In step 6, the test cake is placed in front of the steel ring. First, a shim is placed under the test cake, and then the test cake with the shim is placed on the steel plate.

3. The method for estimating cement strength using cement stability test biscuits according to claim 1, characterized in that, The bending tensile strength of the specimen is measured as the average of the three specimens. When the specimen with the highest strength is greater than 15% of the specimen with the median strength, or when the specimen with the lowest strength is less than 15% of the specimen with the median strength, the median value is taken. When the specimen with the highest strength is greater than 15% of the specimen with the median strength and the specimen with the lowest strength is less than 15% of the specimen with the median strength, the test is invalid.

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