Exploring the Impact Performance of Functionally-graded Preplaced Aggregate Concrete Incorporating Steel and Polypropylene Fibres

Abstract This study investigates the impact response of Functionally-graded Preplaced Aggregate Fibrous Concrete (FPAFC) made with steel and polypropylene fibres against falling mass impact. FPAFC is a new type of concrete containing coarse aggregates and fibres pre-mixed and uniquely packed into an empty mold to develop a skeletal system. Subsequently, voids in the skeleton are filled with formulated cement grout. In this experimental study, twelve different concrete mixtures were produced with 2.4% dosage of mono and hybrid combinations of steel and polypropylene fibres to pioneer the potential use of fibres in FPAFC, for structures demanding impact resistance. Two functionally-graded schemes with various combinations of fibre dosage were considered to evaluate the most influential for impact resistance performance in FPAFC. In all, 180 cylindrical discs were prepared and tested under falling mass impact in conformity with ACI Committee 544 suggestions. Besides, Weibull distribution of two parameters was used to analyse discrepancies in the test’s falling mass impact results. Impact strength was provided corresponding to reliability levels. Results revealed that a two-layer FPAFC exhibited lesser impact strength than single layer concrete. Additionally, choosing the appropriate fibre dosage and mono and hybrid fibre combinations showed the potential ability to achieve superior impact strength in FPAFC than a single two-layer concrete specimen. This phenomenon was due to the fibre bridging action and the three layers brought forth alleviated shear stress transfer in the interfacial transition zone. Thus, a superior composite action was attained in the developed FPAFC. The results obtained from this investigation provides the benchmark data for further in-depth scientific exploration of FPAFC under impact.