THE USE OF MULTIPLE COMBINED NON DESTRUCTIVE TESTING IN THE CONCRETE STRENGHT ASSESSENT : APPLICATIONS ON LABORATORY SPECIMENS
In this paper a series of non-destructive tests has been performed with the purpose to investigate on the mechanical properties of the concrete employed in the civil buildings. A series of specimens were prepared in order to correlate the “in situ” concrete strengths obtained by multiple combinated non-destructive methods with the cubical and cylindrical strength obtained by destructive methods. The multiple combined methods (SonReb Methods + Windsor Probe Tests) were used to quality control and strength estimation of the concrete. In particular, a series of specimens by aggregates having various Mohs’Hardness (inert of fluvial origin) and by aggregate with only a class of Mohs’Hardness (crushed aggregate) has been prepared. During the concrete casting a series of cubical specimens has been prepared. The comparison among non-destructive tests, cubical strength and cores strength are carried out.
Post-installed screws for in-situ assessment of mortar strength
: For capacity evaluation, the structural assessment of existing structures is necessary. Concrete strength is an important parameter for such assessment. Non-destructive tests (NDTs) are used along with the traditional approach of core testing for strength assessment of concrete in existing structures. The low reliability of NDT results leads to uncertainty in assessing concrete strength. A new method of non-destructive testing is presented in this paper with the aim of achieving better reliability and reducing uncertainty in the assessment of mortar strength. This approach is based on a modified pullout of post-installed screw anchors. The technique involves a pushin mechanism for a steel screw inside the mortar where a void underneath the screw is left to allow for the uninterrupted movement of the screw inside the concrete. The failure pattern involves local crushing of concrete between the threads of the screw. This paper investigates the load bearing behaviour of threaded screws installed in cement mortar under compressive loading. The results supports the application of the technique in the assessment of compressive strength of mortar. The main parameters affecting the pushin behaviour are presented and their effects are discussed. It is planned to extend the test program to concrete in the future.
Mathematical Modeling of Scour and Deposition
Electronic computers are opening up the field of sedimentation engineering by permitting the analysis of problems which heretofore have required too much time and effort. Movable stream bed profiles are being calculated in addition to water surface profiles. The initial gradation of sediment material in the stream bed may be prescribed to facilitate the calculation of an armor layer. This gradation is continually changed by the computer program in response to sediment particles being deposited on the stream bed and material on the stream bed being removed to satisfy transport capacity. Hydraulic sorting of sediment by grain size is accomodated. The stream bed does not have to be represented by a single grain size. Retardance of motion because of armor layer is calculated.