Building material testing laboratories provide reliable, accurate, and reproducible test results when they test materials used in construction. All the different types of materials that are used in construction are tested by the NABL accredited construction material testing labs according to quality specifications as IS standards. Testing labs carry out the tests on a number of materials particularly iron and steel.
Materials used in construction
A number of materials are used in construction including iron and steel, plastic, wood and polymers. Since these materials are extensively used, builders have to ensure that the materials used as bars, strings, strands, wires have the proper strength and ductility. Ductility is the capability of the material substance to stretch out into a thin wire but still retain its strength so it does not become weak or brittle enough to snap. Building material testing labs accurately test materials which measure the stress-strain tensile properties that you need in quality construction.
This test determines the ductility of the metal so that its performance in bending can be determined. In a bend test it is the angle of the bend that is tested and the inside diameter is bent to test it for bend strength, fracture strength and resistance to fracture. The conditions are varied according to location and type of test sample as well as chemical composition, tensile properties, hardness, type and quality of the metal. Materials need to have the characteristics that will prevent fracture under pressure which is important for the construction process. Testing labs test the material to see if it will fracture during a three or four point bend test because if it does then the material will fail and could lead to construction defects that could be catastrophic.
The elongation is the increase in length of the gage length and it is expressed as a percentage of the original gage length. When testing elongation, testing labs give both the percentage increase and the original gage length. This is required to understand how much the metal will expand once it is used in construction.
Building material testing laboratories run the tensile test till such time as the sample fails or breaks under load. This type of testing measures the tensile strength, ultimate strength, elongation, modulus of elasticity, yield strength and strain hardening. The measurements taken during the test reveal how well a material will withstand tensile load. Ultimate tensile strength is the maximum stress that a material can withstand while being stretched or pulled before necking. This is till the specimen’s cross-section starts to significantly contract.
Proof stress (0.2%) or Yield stress
Yield strength is the lowest stress that can produce a permanent deformation in a material. In some materials, like aluminium alloys, the point of yielding is hard to define, thus it is usually given as the stress required causing 0.2% plastic strain.
The purpose of re-bend test is to measure the effect of strain ageing on steel and similar materials