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AASHTO-Shrinkage Ring

 

Measuring the Restrained Shrinkage According to AASHTO T334-08 (2020)

"Standard Method of Test for Estimating the Cracking Tendency of Concrete"

 

This test method covers the laboratory determination of the age at cracking and induced tensile stress characteristics of mortar or concrete specimens under restrained shrinkage. The procedure can be used to determine the effects of variations in the proportions and material properties of mortar or concrete on cracking due to both drying shrinkage and deformations caused by autogenous shrinkage and heat of hydration.

A sample of freshly mixed mortar or concrete is compacted in a circular mold around an instrumented steel ring. The compressive strain developed in the steel ring caused by shrinkage of the mortar or concrete specimen is measured with 4 strain gages from the time of casting. Cracking of the test specimen is indicated by a sudden decrease in the steel ring strain. The age at cracking and the rate of tensile stress development in the test specimen are indicators of the materials resistance to cracking under restrained shrinkage (cited from the standard).

AASHTO Shrinakge Ring

The dimensions of the Schleibinger AASHTO T334 Shrinkage Ring are near the same as the ASTM ring but the sizes are different.
The inner ring dimensions has an outer dimater of 305 mm (12 inch), the height is 152 mm ( 6 inch). And the diameter of the outer ring is 457 mm (18 inch)

So the concrete layer is around 76 mm (3 inch) thick and 152 mm (6 inch) high .

As you may see the ASHTO ring is slightly smaller (max. size 324 mm) the the ASTM Ring (330 mm).
The AHSTO ring height is 2 mm higher (152 mm vs. 150 mm). The outer ASHTO ring is much bigger 457 mm (18 inch) instead of 406 mm (16 inch).

Required specimen volume for the Schleibinger AASHTO Shrinkage Ring: 13.83 l = 3.65 US Gallons


On each steel ring a strain-gage amplifier and one thermocouple type K input is mounted. The data of up to 6 rings are digitally transferred to the data-logger.

A data-logger supplied with the system records strain gage data and temperature  and store it in the logger as standard ASCII files. Optional a synchronous registration of the environmental temperature and humidity  is possible.

The logger has a network interface (Ethernet). So you can easily integrate it into local intranet. With a standard web-browser software you can readout the data and visualize it. For further data handling we recommend Microsoft Excel ® ore any similar visualization program. The data are visualized online graphical and numerical on the screen. No special PC software is necessary. You need only your browser-software like Firefox, Chrome, Edge, Opera or Internet-Explorer ® . Operating system Windows, MacOS, Android, Linux. 

Literature:

 

Shrinkage Ring Order code: S00131:

  • AASTO-Shrinkage ring made of steel (1.0570) with 4 strain gages. The inner ring  has an outer diameter of 305 mm (12 inch), the height is 152 mm ( 6 inch). Thickness of the ring:  12.7 mm (0.5 inch).
  • Strain gage amplifier, thermocouple type K input and digitizing unit, mounted inside the inner ring. Serial digital SMB bus interface to the data logger S0003.
  • Outer ring made of stainless steel. Inner diameter 457 mm (18 inch), height 152 mm (6 inch).
  • Specimen volume ca. 13.8 liters (3.65 US.liq.gal.). Specimen thickness ca. 35.5 mm.
  • Base made of PP ca. 540 x 540 x 20 mm³
  • Bolts, nuts and washers for fixing the rings on the ground plate.
  • Stainless steel ring for covering the specimen.

 

Data Logger - Order Code: S0003:
  • Data logger with an interface for up to 6 rings S00031. 
  • Network interface and built in WEB-Server, software pre-installed.
  • Sampling rate 10s..1h for at least 1 year (2 GByte)
  • Option: environmental temperature and humidity measurement S0016
  • User Manual
  • Size: 24 x 21 x 6 cm, weight 1.8 kg

All specs may be changed without notice!

 

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Meet Schleibinger: CONCREEP12, June, 12-15, 2024, Delft, Netherlands CONCREEP12 will be the 12th conference in a series (which started in 1958) dealing with creep, shrinkage and durability of concrete and concrete structures.

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