Effect of production technology on high strain rate characteristics of Reactive Powder Concrete

Abstract

This paper presents an experimental study evaluating the effect of mixing technology and curing conditions on the high strain rate compressive behavior of Reactive Powder Concrete (RPC). Nine sets of specimens were prepared with identical composition, based on Aalborg Portland cement 52.5 R, fine sand, silica fume, micronized quartz, superplasticizer and water. Three different production methods were tested: 1) mixing under ambient pressure+ standard moulding without additional pressure, 2) vacuum mixing+ standard moulding without additional pressure, 3) mixing under ambient pressure+ moulding with subsequent 5 MPa pressure during the setting time. Three curing conditions were adopted: 1) Curing in water at an ambient temperature, 2) Curing under hydrothermal conditions at 190°C for 40 hours, 3) Curing under hydrothermal conditions at 180°C for 8 hours, Quasi-static compressive and flexural strength tests were performed and bulk density was determined. Split Hopkinson pressure bar (SHPB) equipment was used to determine the RPC behaviour at high strain rates. It was observed that vacuum mixing reduces the pore content in the composite, which is accompanied by a significant increase in peak stress values of water cured RPC at both quasistatic and high strain rate regimes (about 20% increase). Further increase in peak stress values is then achieved by hydrothermal treatment, with higher values connected with higher temperature and dwell time. The pressure developed at the first stage of the curing period does not provide a significant benefit in the form of an increase in mechanical parameters. The presented research is a part of the development process of high-performance ballistic resistant composites. The results will be used for the design of the composite panels for protection against ballistic load in the A2-A4 level according to STANAG 2280 standard.