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CN-116297729-B - Method for testing pH value of concrete pore solution

CN116297729BCN 116297729 BCN116297729 BCN 116297729BCN-116297729-B

Abstract

The invention discloses a method for testing the pH value of a concrete pore solution, and belongs to the technical field of building materials. S1, drilling holes on the surface of a concrete test piece, adding deionized water into the holes, sealing, carrying out standard curing until the pH value of the solution in the holes is not increased, wherein the measured pH value is recorded as X1, S2, taking out all the solution in the holes, adding deionized water with the same volume as that of the step S1 into the holes again, sealing, carrying out standard curing, curing for the same days as that of the step S1, testing the pH value of the solution in the holes, recording as X2, S3, calculating the pH value of the solution in the holes of the concrete according to the following formula, wherein the concentration of OH ‑ in the solution in the holes of the step S1 is 1=10 (X1‑14) mol/L, the concentration of OH ‑ in the solution in the holes of the step S2 is 2=10 (X2‑14) mol/L, the concentration of actual OH ‑ in the solution in the holes of the concrete is Y1×Y1/Y2mol/L, and the pH value of the solution in the holes of the concrete is 14+lgY. According to the method, the actual OH ‑ concentration in the concrete pore solution is calculated according to the pH value of the concrete pore solution for two times, so that the dilution effect caused by large pore diameter can be eliminated, and the pH value of the pore solution close to the true value can be obtained.

Inventors

  • LI PENGXIANG
  • WANG JIMIN
  • FAN ZHIQIANG
  • DONG YUN
  • HE JINRONG
  • LIAO LINGMIN
  • ZHOU JIFANG
  • FENG JING
  • ZHANG JIAN

Assignees

  • 长江水利委员会长江科学院
  • 雅砻江流域水电开发有限公司

Dates

Publication Date
20260505
Application Date
20221220

Claims (9)

  1. 1. The method for testing the pH value of the concrete pore solution is characterized by comprising the following steps of: s1, drilling holes on the surface of a concrete test piece, adding deionized water into the holes, sealing, and standard curing until the pH value of the solution in the holes is not increased any more, wherein the measured pH value is recorded as X1; s2, taking out all the solutions in the holes, adding deionized water with the same volume as that in the step S1 again into the holes, sealing, carrying out standard maintenance, wherein the number of days of maintenance is the same as that in the step S1, and then testing the pH value of the hole solution and marking as X2; S3, calculating the pH value of the concrete pore solution according to the following formula: Step S1 concentration y1=10 (X1-14) mol/L of OH - in the well solution; Step S2 pore solution OH - concentration y2=10 (X2-14) mol/L; Actual OH - concentration Y=Y1×Y1/Y2 mol/L in the concrete pore solution; ph=14+lgy of the concrete pore solution.
  2. 2. The method for testing the pH value of a concrete pore solution according to claim 1, wherein the size of the concrete test piece is not smaller than phi 100mm by 150mm, the diameter of the pore is 20mm, and the depth is not smaller than 100mm.
  3. 3. The method for testing the pH value of a concrete pore solution according to claim 1, wherein the size of the concrete sample is not less than 150mm by 150mm, the diameter of the pore is 20mm, and the depth is not less than 100mm.
  4. 4. The method for testing the pH of a concrete pore solution according to claim 1, wherein standard curing conditions in the steps S1 and S2 are the same.
  5. 5. The method for testing the pH of a concrete pore solution according to claim 4, wherein the standard curing conditions are such that the temperature is 20.+ -. 3 ℃ and the relative humidity is not less than 95%.
  6. 6. The method for testing the pH of a concrete pore solution according to claim 1, wherein said pore is located at a central location on the surface of a concrete test piece.
  7. 7. The method of claim 1, wherein the deionized water is added in an amount of 20mL in both steps S1 and S2.
  8. 8. The method for testing the pH value of the concrete pore solution is characterized by comprising the following steps of: S1, drilling holes on the surface of a concrete test piece, adding deionized water into the holes, sealing, carrying out standard maintenance for 28d, taking out the solution in the holes, marking the solution as hole solution a, and measuring the pH value of the hole solution a by adopting a pH meter, and marking the pH value as X1; S2, adding deionized water with the same volume as that of the step S1 into the hole again, sealing, carrying out standard maintenance for 28d, taking out the solution in the hole, marking the solution as hole solution b, and measuring the pH value of the hole solution b by adopting a pH meter, and marking the pH value as X2; S3, calculating the pH value of the concrete pore solution according to the following formula: Concentration of OH - in the pore solution a y1=10 (X1-14) mol/L; Concentration of OH - in the pore solution b y2=10 (X2-14) mol/L; Actual OH - concentration Y=Y1×Y1/Y2 mol/L in the concrete pore solution; ph=14+lgy of the concrete pore solution.
  9. 9. The method of claim 8, wherein the pH meter is calibrated using a buffer having a ph=9.18 and a ph=12 prior to the testing.

Description

Method for testing pH value of concrete pore solution Technical Field The invention belongs to the technical field of building materials, and particularly relates to a method for testing the pH value of a concrete pore solution. Background The Alkali-aggregate reaction (Alkali-AGGREGATE REACTION) of concrete refers to the chemical reaction of Alkali in the concrete and the aggregate with Alkali activity, which causes the volume expansion and cracking of the concrete, reduces the durability of the concrete and shortens the service life of the concrete structure. The three conditions of alkali aggregate reaction are that the wet environment, the aggregate has alkali activity and the alkali content in the concrete reaches a certain limit value. Namely, when the alkali content is below a certain value, the alkali reaction expansion rate of the concrete does not significantly change with the increase of the alkali content even though the aggregate having the alkali content activity is used, and when the alkali content is above this value, the alkali reaction expansion rate of the concrete increases sharply with the increase of the alkali content. Likewise, the safety limits for the alkali content are different for aggregates of different degrees of activity. From this, it is known that the pH of the concrete pore solution is closely related to AAR, and whether AAR occurs or not, the residual reaction risk, etc. can be qualitatively analyzed, reflecting the problem of long-term safety after the use of alkali-activated aggregates. Thus, accurate testing of the pH in concrete is required. The pH value of the concrete pore solution is researched by adopting methods such as on-site dissolution, pressure filtration and the like at home and abroad, the results obtained by the pressure filtration method are commonly used as reference standards of results of other methods, and therefore, the application requirements of the pressure filtration method are increasing. However, since the filter-press pore solution is difficult to obtain for long-term concrete, low-water-ash concrete and full-graded concrete, when the pore solution is prepared by using a pressing method to test the pH value of the concrete, only a small amount of pore solution can be obtained by pressing and cannot represent the real pore solution, and meanwhile, complicated equipment is required for the filter-press method, and the operation cost is high. There is also a method in the prior art of drilling holes in the concrete surface, adding neutral water, and then testing the pH of the hole solution. The method for testing the pH value of the concrete pore liquid comprises the steps of manufacturing a test piece and testing the pH value of the concrete pore liquid, manufacturing the test piece, namely cutting the concrete to be tested into the test piece, drilling holes in the test piece, sealing the hole-carrying organic glass on the hole of the test piece, adding distilled water into the hole of the test piece and sealing the hole, then storing the treated test piece in a test box with 100% humidity and an environment of 22-25 ℃, and testing, namely placing a glass pH microelectrode and an Ag-AgCl micro reference electrode in the hole of the test piece to test the pH value of the pore liquid when the test piece is stored for 14 days and 28 days. However, by drilling holes in concrete, the limiting pH value of the test hole solution after adding neutral water has the problems that if the hole diameter is too small, the added water is too small, the ion exchange in the concrete is insufficient, if the hole diameter is too large, the added water is too much, dilution is caused, and the accuracy of the test result is low. Therefore, the method for accurately testing the pH value of the concrete pore solution is of great significance to AAR evaluation of concrete samples. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide the method for testing the pH value of the concrete pore solution, which is simple to operate, does not need complex equipment, has high accuracy, and can solve the technical problems of complex operation and low accuracy of test results in the prior art. In order to achieve the above purpose, the specific technical scheme of the invention is as follows: The method for testing the pH value of the concrete pore solution comprises the following steps: s1, drilling holes on the surface of a concrete test piece, adding deionized water into the holes, sealing, and standard curing until the pH value of the solution in the holes is not increased any more, wherein the measured pH value is recorded as X1; S2, taking out all the solutions in the holes, adding deionized water with the same volume as that in the step S1 again into the holes, sealing, carrying out standard maintenance, wherein the number of days of maintenance is the same as that in the step S1, and then testing the pH value of the hole solutio