ADMET has worked with the concrete industry for decades.
In the early 1990s, most concrete testing machines employed dial gauges with limited resolution and accuracy to indicate force. A stopwatch was used with the dial gauge to provide a crude measurement of loading rate. Operators wrote the maximum force readings for each test on a clipboard; later to be converted into compressive strength then typed into a database. It was clear that there were many opportunities to introduce errors into the test results. ADMET recognized the limitations of the early 1990s equipment and applied its expertise in software, instrumentation and control to develop the first digital indicating system designed for testing concrete according to ASTM C39, C109 and C78. ADMET’s DC12 Digital Indicator included many firsts in concrete testing:
- First to include specimen type/geometries to facilitate compressive and flexural strength measurements
- First to include C39 cylinder correction factor to automatically adjust compressive strength readings according to the length to diameter ratio
- First to provide both load and stress rate indication which enabled the operators to adjust the manual loading valve during test to stay within the specified rate limits
- First to enable operators to store date, time, specimen size, specimen age, specimen weight, cylinder cap type and cylinder break type with each compressive strength result.
- First to allow operators to directly connect a printer to the digital indicator and generate a hardcopy printout of the load/stress vs time curve or a table of results including a statistical summary for a group tests.
- First to allow the test results including specimen information via a RS232 link to be downloaded to a computer for easy import into common spreadsheet programs or a company database designed to generate compressive strength reports for their clients.
- First to offer a single range force measurement system that expanded the ASTM E4 force range for a concrete testing machine and enabled testing on a single machine at lower forces. At the time, equivalent systems required multiple dial gauges to achieve similar results at additional costs. ADMET accomplished this by incorporating a multi point calibration procedure with a piecewise linear fit between calibration points.
These first-of-their-kind ADMET innovations greatly reduced the time and resources required to perform cylinder tests and eliminated many of the manual data entry errors. ADMET digital indicators were adopted quickly in the marketplace. OEM testing machine makers began private labeling ADMET indicators and including them on their testing machines. ADMET also offered upgrade/retrofit kits to calibrators who began installing the ADMET digital indicating systems on existing machines already in use in the field.
By the late 1990s, ADMET indicators were installed on a great number of concrete testing machines. The indicators streamlined testing and eliminated many errors. The indicators could also verify if a test was performed according to ASTM specifications; frequently, stress rate verification had been the exception instead of the norm.
The Genesis of ADMET MegaForce Automatic Loading System
Nearly all concrete testing machines are manually controlled. Operators continuously adjust a valve during testing to control the loading rate over 15 to 30 to 60 second intervals. Since many testing laboratories are paid by the number of cylinders tested, they are motivated to test quickly which can lead to errors and non-compliance with ASTM specifications. ASTM C39 Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens stipulates that the loading rate fall within 28 to 42 psi/sec (0.2 to 0.3MPa/sec). For normal strength concrete, the measured compressive strength will be 2-3% greater for cylinders tested 0.2MPa/sec faster than a second group at the slower rate. A 20% increase in measured compressive strength for high strength concrete is possible when loading rates exceed C39 limits.
Realizing the importance of performing tests within specified ASTM load rate limits, ADMET set out to eliminate the operator and developed an affordable automatically controlled concrete testing system that ensures proper loading rates are maintained throughout each test. The ADMET MegaForce Automatic Loading System was the result of our development efforts. Since its creation, the MegaForce system has been perfected over several iterations and subsequent years of development. Concrete testing machines require up to 10,000 psi of hydraulic pressure to obtain full machine force capacity. Commercially available automatic hydraulic control valves are only capable of operating up to 4,500 psi and are thus not used on these concrete testing machines.
MegaForce became another ADMET first in the concrete testing industry. MegaForce is affordable, can be installed on new or retrofitted to existing testing machines and most importantly ensures that all tests are performed according to ASTM specifications.
Expanding the Capability of ADMET Digital Indicators
When airport and dam construction is taking place, determining Young’s Modulus and Poisson’s Ratio in compression according to ASTM C469 is added to the list of required tests. ASTM C469 requires up to two additional inputs to measure axial and transverse strain. ADMET again provided the answer at a fraction of the cost of the alternative computer based solutions by expanding the capability of it’s digital indicating systems.
New Materials Require New Concrete Testing Standards
In the past 15 years, engineers have begun embedding fibers in concrete to greatly increase their flexural strength and reducing weight and cost. To properly qualify this fiber reinforced concrete, new testing standards needed to be developed and ADMET testing systems and software were used by the engineers who developed the initial test standards. This early work, resulted in ASTM C1609 Flexural Strength of Fiber Reinforced Concrete being adopted as one standard used to qualify fiber reinforced concrete. Today, ADMET is one of a select few of testing machine manufacturers that offers equipment to perform the excruciatingly demanding ASTM C1609 tests.
ADMET has a long and distinguished history of innovation in concrete testing and has been at the forefront of advancing concrete testing from the stone age to the space age. If you want to get the most out of your concrete testing equipment, contact ADMET now.
Case Study: Flood Testing Lab
Flood Testing Labs, Inc. (FTL) is one of North America’s preeminent concrete, asphalt, soils, steel, and weld test laboratories. Based in Chicago, FTL services building and roadway construction with both onsite technical services and certified laboratory testing to provide technical certifications for materials. Its largest service is concrete cylinder compression testing. One of their testing machines, a 400,000 lb. Tinius Olsen system, was showing wear and tear associated with long-term use. After speaking with ADMET engineers, it was determined the best course of action was a retrofit that would put new digital controllers on the machine, improving its accuracy.
The ADMET story started 25 years ago with testing machine retrofits and software and controller design, making the company a leader in its industry. Since then, ADMET has gone on to manufacture its own testing frames and systems, building on the core strength of its robust software design. In addition to our standard offerings, we will also tailor a custom system to meet your special testing requirements. If you would like to improve your material testing processes, contact us.