Submitted by the Guyana National Bureau of Standards (GNBS)
For just over two years, the Guyana National Bureau of Standards (GNBS) has been providing the testing of concrete blocks to small block makers and large manufacturers who distribute their products for use within the construction sector. This has resulted in several of these stakeholders becoming aware of the quality of the blocks they manufacture, and at the same time increased the quality consciousness of consumers regarding this widely used building material.
In 2023, with the acquisition of a Rebound/Schmidt Hammer, the GNBS Industrial Metrology and Testing Department has further expanded its scope of testing in relation to construction materials and now offers Non-Destructive Testing (NDT) of concrete structures.
The Non-Destructive Testing (NDT) of concrete structures is a useful service to homeowners concerned about the quality of their concrete floors, walls, posts, fence, bridges etc.; or contractors and engineers who are involved in the construction or the approval of new structures. This third-party testing offers an independent determination as to whether structures were built to expectations or requirements.
The new piece of testing equipment can be used for non-destructive testing of hardened concrete by the rebound method, and it provides a convenient and rapid indication of the compressive strength of the concrete structure. Once the strength of the concrete is determined, a certificate is prepared and provided by the GNBS to clients, and it can be used as a firm basis for the acceptance or rejection of a structure.
The Rebound Hammer Test is used to differentiate the acceptable and questionable parts of a structure or to compare different structures based on strength. The amount of rebound of the mass depends on the hardness of concrete surface. Hence, the equipment can also determine the hardness of concrete used to make concrete electrical poles, columns, foundations, etc. with a range from 0 – 8400 Pounds per Square Inch (PSI) or 0 – 58 Megapascals (MPa).
Based on the specification of the ASTM Standard C805/C805M-18 “Standard Test Method for Rebound Number of Hardened Concrete”, the quality of concrete for respective average rebound numbers is as follows; more than 40 Megapascals being very good, 30 to 40 Megapascals being good, 20 to 30 Megapascals being fair, less than 20 Megapascals being poor, and zero Megapascals being delaminated.
The GNBS is working to make testing of concrete structures affordable and trained Laboratory Technicians are prepared to do onsite visits to provide this vital service, which could be the difference between ensuring a quality long lasting structure and one which prematurely collapses. Meanwhile, the Bureau continues to provide testing of concrete blocks (size three, four or six inches), cubes and cylinders in accordance with the respective national and international standards.