A new drop-weight impact machine for studying fracture processes in structural concrete

Abstract

This paper describes the main characteristics of a new drop-weight impact machine that has been specifically designed for studying the dynamic mechanical behaviour of structural concrete samples. Such a type of equipment has been used to generate simple and measurable fracture processes under moderate-to-fast loading rates, contrary to blast chambers, which produce complicated crack patterns that are difficult to analyse. The machine consists of two main parts, the mechanical structure and the data acquisition system. The former is just a hammer, guided by two robust columns, which can impact the specimen with energy up to 7860 J. The latter consists of piezoelectric force sensors, accelerometers and optical fibre photoelectric sensors plus oscilloscopes and signal conditioners. The paper also presents the results of some preliminary tests on plain-notched specimens that show the sensitivity of the work of fracture of a high-strength concrete to the loading rate. © 2008 Blackwell Publishing Ltd.