1. ASTM-Shrinkage Ring
Standard Test Method for Determining Age at Cracking and Induced Tensile Stress Characteristics of Mortar and Concrete under Restrained Shrinkage
This test method describes a laboratory procedure for determining the age at cracking and the induced tensile stress characteristics of mortar or concrete specimens under restrained shrinkage conditions. It helps assess the impact of varying proportions and material properties of mortar or concrete on cracking caused by drying shrinkage, autogenous shrinkage, and heat of hydration.
A sample of freshly mixed mortar or concrete is compacted into a circular mold around an instrumented steel ring. The compressive strain in the steel ring, due to the shrinkage of the mortar or concrete, is measured using four strain gauges from the time of casting.
A sudden decrease in the steel ring strain indicates cracking in the test specimen. The age at cracking and the rate of tensile stress development in the specimen provide insight into the material's resistance to cracking under restrained shrinkage (as cited from the standard).
Steel ring strain vs. time. The specimen begins to crack after 6.8 days at a strain of approximately 100 µm/m, according to ASTM C1581.
Each steel ring is equipped with a strain-gage amplifier and a type K thermocouple input. Data from up to six rings are digitally transferred to the data logger.
The system’s data logger records strain gage data and temperature, storing it as standard ASCII files. Optionally, it can also synchronously register environmental temperature and humidity.
The logger features a network interface (Ethernet), allowing easy integration into a local intranet. Using a standard web browser, you can read and visualize the data. For further data handling, we recommend Microsoft Excel® or any similar visualization program. The data are displayed online both graphically and numerically on the screen. No special PC software is necessary; you only need your browser software, such as Firefox, Chrome, Edge
Shrinkage Ring Order Code: S00031:
This ASTM Shrinkage ring is made of steel (1.0570) and includes 4 strain gages. It has a thickness of 13 mm, an outer diameter of 330 mm, a height of 150 mm, and weighs 15.5 kg. Other sizes are available upon request.
The strain gage amplifier, thermocouple type K input, and digitizing unit are mounted inside the inner ring. It features a serial digital SMB bus interface to the data logger S0003. The outer ring is made of stainless steel with an inner diameter of 406 mm and a height of 150 mm.
The specimen volume is approximately 6.6 liters (1.74 US liquid gallons) with a specimen thickness of about 35.5 mm. The base is made of PP and measures 480 x 480 x 20 mm³. Bolts, nuts, and washers are included for fixing the rings to the ground plate. A stainless steel ring is provided for covering the specimen.
Data Logger - Order Code: S0003:
This data logger can interface with up to 6 rings (S00031). It includes a network interface and a built-in web server with pre-installed software. The sampling rate ranges from 10 seconds to 1 hour, and it can store data for at least 1 year (2 GB). An optional feature for environmental temperature and humidity measurement (S0016) is available. The data logger comes with a user manual and has dimensions of 24 x 21 x 6 cm, weighing 1.8 kg. All specifications are subject to change without notice.
2. AASHTO Shrinkage Ring
Standard Method of Test for Estimating the Cracking Tendency of Concrete
This test method outlines the laboratory procedure for determining the age at which cracking occurs and the induced tensile stress characteristics of mortar or concrete specimens under restrained shrinkage. It can be used to assess the impact 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 the 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 in the steel ring, caused by the shrinkage of the mortar or concrete specimen, is measured using four 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 material's resistance to cracking under restrained shrinkage.
Dimensions of the Shrinkage Ring AASHTO T334
The dimensions of the Shrinkage Ring AASHTO T334 are similar to the ASTM ring, but there are some differences. The inner ring has an outer diameter of 305 mm (12 inches) and a height of 152 mm (6 inches). The outer ring has a diameter of 457 mm (18 inches).
This results in a concrete layer that is approximately 76 mm (3 inches) thick and 152 mm (6 inches) high.
As you can see, the AASHTO ring is slightly smaller (maximum size 324 mm) compared to the ASTM ring (330 mm). The AASHTO ring height is 2 mm higher (152 mm vs. 150 mm). The outer AASHTO ring is significantly larger at 457 mm (18 inches) compared to the ASTM ring’s 406 mm (16 inches).
The required specimen volume for the Shrinkage Ring AASHTO T334 is 13.83 liters (3.65 US gallons).
Instrumentation and Data Logging
Each steel ring is equipped with a strain-gage amplifier and a type K thermocouple input. Data from up to six rings are digitally transferred to the data logger.
The data logger, supplied with the system, records strain gage data and temperature, storing it as standard ASCII files. Optionally, it can also synchronously register environmental temperature and humidity.
The logger features a network interface (Ethernet), allowing easy integration into a local intranet. Using standard web browser software, you can read and visualize the data. For further data handling, we recommend Microsoft Excel® or any similar visualization program.
The data are displayed online both graphically and numerically on the screen. No special PC software is necessary; you only need your browser software, such as Firefox, Chrome, Edge, Opera, or Internet Explorer®. The system is compatible with Windows, MacOS, Android, and Linux operating systems.
Shrinkage Ring Order Code: S00131:
The AASHTO-Shrinkage ring is made of steel (1.0570) and includes 4 strain gages. The inner ring has an outer diameter of 305 mm (12 inches) and a height of 152 mm (6 inches). The ring thickness is 12.7 mm (0.5 inches).
The strain gage amplifier, thermocouple type K input, and digitizing unit are mounted inside the inner ring. It features a serial digital SMB bus interface to the data logger S0003. The outer ring is made of stainless steel with an inner diameter of 457 mm (18 inches) and a height of 152 mm (6 inches).
The specimen volume is approximately 13.8 liters (3.65 US liquid gallons) with a specimen thickness of about 35.5 mm. The base is made of PP and measures approximately 540 x 540 x 20 mm³. Bolts, nuts, and washers are included for fixing the rings to the ground plate. A stainless steel ring is provided for covering the specimen.
Data Logger - Order Code: S0003:
This data logger can interface with up to 6 rings (S00031). It includes a network interface and a built-in web server with pre-installed software. The sampling rate ranges from 10 seconds to 1 hour, and it can store data for at least 1 year (2 GB).
An optional feature for environmental temperature and humidity measurement (S0016) is available. The data logger comes with a user manual and has dimensions of 24 x 21 x 6 cm, weighing 1.8 kg. All specifications are subject to change without notice.
