Both Testing of hardened concrete are conducted on hardened concrete and are thus not suitable for use in con- struction monitoring. This is probably one of the best examinations to consider since it provides information on the overall quality of a concrete. Choose a testing laboratory.
ACI"Building Code Requirements for Structural Concrete", Chapter 4 available from the American Concrete Institute provides recommended air contents based on the aggregate size used in a mix and the exposure class of the concrete.
Further, because of the rel- atively long period of testing and the complexity of the test procedure, these tests likely will be used only when evaluat- ing EOT concrete mixtures to establish mixture design param- eters e.
It is not practical to apply the a true line load to the cylinder because the side are not smooth enough and because it would induced high compressive stresses at the surface. Another commonly accepted method to measure permeability is the rapid chloride permeability test AASHTO Talthough this test can be difficult to apply to EOT concrete containing certain admixtures.
Molds may be reusable, made of heavy-gauge metal or single-use, made from sheet metal or waxed cardboard.
The unit weight is determined by the formula below. The minimum required compressive or flexural strength is commonly raised for the slower-setting to hour concrete mixtures.
Your comments and questions are more than welcome. If the test falls outside of the specified range, a check test is typically performed to confirm test results. Testing of hardened concrete of Elasticity To estimate the modulus of elasticity from the nonlinear behavior of concrete the chord modulus of elasticity, Ec, is measured.
A hard or stiff plate will concentrate stress at the outer edges whereas a softer plate will have higher stress at the center. The load is applied over the specimen diametrically and uniformly through the cylinder length till the cylinder undergoes failure.
At this point, it can be weighed as part of the calculation to determine the fresh concrete unit weight. They are then covered to protect against rapid evaporation and to avoid contamination. Length-to-diameter ratios are ideally 2: Fresh concrete tests run along with a set of compressive strength cylinders are: The thermometer is placed to provide at least 3 inches of concrete around the inserted stem and left in place a minimum of 2 minutes and until the temperature has stabilized.
As wireless technology continues to develop, it is foreseeable that each repair will have a wireless maturity gauge installed that reports to a hand-held unit, which in turn computes the time to opening based on stored mix design information. This test is better than those previously discussed, however, the test may be planned in advance and the assembly embedded in the concrete during casting.
Testing tip: Test cylinders that are poorly made, stored, or neglected will cause headaches and may result in the need for costly hardened concrete testing, all to provide the owner information proving that the actual in-place concrete is of sufficient strength and durability.
While this procedure is simple, do not take it lightly. Testing Hardened Concrete Strength Testing Strength testing is an integral part of the mixture design process and construction monitoring for EOT concrete. Com- pressive strength (AASHTO T 22), measured on cylindrical specimens, is often specified to be at least MPa (2, psi) at time of opening (FHWA ).
Part B: Testing of hardened concrete 1. Objectives: The objective of the hardened concrete test was to determine the compressive and indirect tensile strength. The test measures the rebound of a hardened steel hammer impacted on the concrete by a spring. This method has the same limitations as the surface hardness tests.
The results are affected by: (1) surface finish; (2) moisture content; (3) temperature; (4) rigidity of the member being tested; (5) carbonation of the surface; and (6) direction of impact (upward, downward, horizontal). in hardened concrete which has been water cured.
2 Normative references The following referenced documents are indispensable for the application of this document. There are several hardened concrete tests frequently used to examine concrete strength and durability.
Be aware, however, that the costs of testing can be high and .Testing of hardened concrete