Basic methods for determining the frost resistance of concrete

The first method

All types of concrete, except for concrete road and airfield coatings and concrete structures operated in mineralized water

Testing aids and assistive devices

  • Freezer, ensuring the achievement and maintenance of the freezing temperature minus (18 ± 2) ° С. The unevenness of the temperature field in the air of the useful volume of the chamber should not exceed 3 ° C.
  • Bath for saturation of samples with water at a temperature of (20 ± 2) ° С.
  • A bath for thawing samples equipped with a device ensuring the maintenance of water temperature (20 ± 2) ° С.
  • Wooden lining with a triangular cross section 50 mm high.
  • Laboratory balance GOST 24104 with a weighing error of ± 1 g.
  • Mesh container for storing basic samples.
  • Mesh rack for placing samples in the freezer.
  • Water by GOST 23732 with a soluble salt content of not more than 2000 mg / l.

Test preparation

  • Concrete samples are made in molds according to GOST 22685.
  • Control and basic samples are saturated with water.

Testing

  • Water-saturated control samples are removed from water, wiped with a damp cloth and tested for compression. GOST 10180 with processing results;
  • The intraseries strength variation coefficient is calculated. A series of samples with an intra-series coefficient of variation in strength exceeding 9% is removed from testing and a new series of samples is tested.
  • Water-saturated basic samples are removed from water, wiped with a damp cloth and placed in a freezer in a container or installed on a mesh rack of the chamber so that the distance between the samples, the walls of the container and the racks located above is at least 20 mm. Turn on the camera and lower the temperature. The start of freezing is considered to be the moment the temperature in the chamber is set minus 16 ° C.
  • The number of freezing and thawing cycles, after which the compressive strength of concrete samples is determined, is taken according to the table.
  • Samples are tested according to the regimen indicated in the table.
  • The minimum duration of freezing of lightweight concrete samples of grades of average density D1500-D1200 is increased by 0,5 hours, grades D1200-D1000 - by 1 hour, grades D900 and less - by 1,5 hours.
  • The air temperature in the freezer is measured in the center of its volume in the immediate vicinity of the samples.
  • After freezing, the samples are thawed in a bath with water at a temperature of (20 ± 2) ° С. When thawing, samples are placed at a distance of at least 20 mm from each other, the walls and the bottom of the bath, the water layer above the upper face of the sample should be at least 20 mm.
  • The temperature of the water in the bath is measured in the center of its volume in the immediate vicinity of the samples.
  • The water in the bath for thawing samples is changed every 100 cycles of alternating freezing and thawing.
  • The main samples after a given number of freezing and thawing cycles are removed from water, wiped with a damp cloth and tested for compression according to 5.1.3.1.
  • If cracks and (or) chips and (or) peeling of ribs appear during testing, the tests are terminated.

The second method

Concrete road and airfield coatings and concrete structures operated in mineralized water

Testing aids and assistive devices

  • Testing tools and auxiliary devices according to 1 method.
  • Sodium Chloride GOST 4233.

Test preparation

  • Concrete samples are made in molds according to GOST 22685.
  • The basic and control samples are saturated with a 5% aqueous solution of sodium chloride before testing.
  • Control samples are removed from the solution, wiped with a damp cloth, weighed and tested for compression.
  • The main samples after saturation are subjected to tests for freezing and thawing according to the regime shown in the table.

Testing

  • Basic samples are placed in the freezer according to 5.1.3.2. The beginning of freezing is considered to be the moment of establishment of the temperature in the chamber minus 16 ° С.
  • The number of freezing and thawing cycles, after which the compressive strength of concrete samples is determined, is taken according to table 4.
  • The aqueous solution of sodium chloride in the thawing bath is changed every 100 cycles.
  • The main samples after conducting a given number of cycles of freezing and thawing are inspected. The material separated from the sample is removed with a stiff nylon brush. Samples are wiped with a damp cloth, weighed and tested for compression.

Order a service: Construction laboratory of materials and structures

  • This field is used for verification purposes and should be left unchanged.


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