Gregor Trtnik

Prediction of concrete strength using ultrasonic pulse velocity and artificial neural networks.

Ultrasonic pulse velocity technique is one of the most popular non-destructive techniques used in the assessment of concrete properties. However, it is very difficult to accurately evaluate the concrete compressive strength with this method since the ultrasonic pulse velocity values are affected by a number of factors, which do not necessarily influence the concrete compressive strength in the same way or to the same extent. This paper deals with the analysis of such factors on the velocity-strength relationship. The relationship between ultrasonic pulse velocity, static and dynamic Youngs modulus and shear modulus was also analyzed. The influence of aggregate, initial concrete temperature, type of cement, environmental temperature, and w/c ratio was determined by our own experiments. Based on the experimental results, a numerical model was established within the Matlab programming environment. The multi-layer feed-forward neural network was used for this purpose. The paper demonstrates that artificial neural networks can be successfully used in modelling the velocity-strength relationship. This model enables us to easily and reliably estimate the compressive strength of concrete by using only the ultrasonic pulse velocity value and some mix parameters of concrete.

Recent advances of ultrasonic testing of cement based materials at early ages

To summarize some of the most important findings in the field of ultrasonic (US) testing of early age hydration and formation of structure of different cement based materials (CBMs), a review of literature with focus on US P-wave transmission and S-wave reflection methods is presented in this paper. The review shows a great ability of both US techniques to observe setting phenomena and to determine different milestones during the early age formation of CBMs microstructure. Clear physical basis, high accuracy, and non-destructive nature of the method indicate that US methods could become standardized in the near future.

Monitoring of bitumen hardening with a non-destructive ultrasonic shear wave reflection technique

Abstract The article presents a possibility of using a non-destructive ultrasonic shear wave reflection technique for monitoring hardening process of bitumen. The technique relies on the use of a new measuring instrument called USWR-4 Hardening meter, which was developed to be applicable directly in situ and has been effectively used for cement-based materials so far. It works on the principle of continuous measurement of change of a shear wave reflection coefficient. Three different types of paving grade and two polymer-modified bitumens were used. Results show that the presented ultrasound technique can effectively track a temperature-dependent hardening process of bitumen.

COST Action TU1404—Recent Advances of WG1: Testing of Cement-Based Materials

Work Group 1 (WG1) of COST Action TU1404 entitled “Testing of cement based materials” deals with determination of different properties of early age and hardened cement based materials with the following main objectives: (1) to recommend new advanced standard techniques which have been developed during the last years to become standard in the (near) future, (2) to test the ability of using different waste, recycled, and by-products as raw materials to design sustainable concrete mixture, and (3) to prepare a database of concrete mixtures which could serve designers and engineers to better predict lifespan, durability, and serviceability of concrete mixtures and structures. The paper describes organization and strategic view of WG1, presents its main objectives and gives important details about Round Robin Test, as a main tool that will be employed within WG1.