Performance of Pull-out Specimens Cast of Modified Reactive Powder Concrete

Abstract

Reactive powder concrete (RPC) is one of the latest developments in concrete technology. It is also known as an ultra-high-performance concrete (UHPC) which is characterized by dense mix, high cement content, very high mechanical strength, high durability, and incorporate in most cases steel fibers to enhance the fracture properties. Modified reactive powder concrete (MRPC) is a special type of concrete that is produced by replacing a portion of quartz sand by natural graded aggregate less than (8 mm). This study aims to modify RPC by incorporating recycled bricks which result from the demolition of construction sites as coarse aggregate as partial replacement of fine aggregate and cementation material to reduce landfill areas. The present work can be divided into two parts according to two main objectives. The first part involves an experimental study of the mechanical properties for RPC and Modified Reactive Powder Concrete MRPC replacing 40% of fine sand and 25% of cementation material by crushed bricks aggregate. The experimental program includes investigating the effect of steel fiber type and the absence of crushed bricks aggregates on some important mechanical and fresh properties of RPC and MRPC such as compressive strength, splitting tensile strength, modulus of elasticity, modulus of rupture and flowability . According to the results of the experiment of test, it can be concluded which is reused waste and demolished bricks as coarse aggregate with (max size 10 mm) was better enough to partially replaced by ratio 40% of silica sand than cementation replacement for RPC, in term of acceptable performance of mechanical and fresh properties. A high compressive strength, i.e. 138 MPa, was achieved by using crushed bricks aggregate in RPC; this result is in contrast with the model proposed to relate the high compressive strength level of RPC to the absence of coarse aggregate . The second part involves an experimental study of the structural behavior for four types of shear connectors: headed stud (with changing steel fibers type), L-shape angle, T-shape, and Perfobond with RPC and MRPC. Eighteen composite push-out specimens were tested individually to investigate their behavior by measuring the slip values for each load increment up to failure, thus determining the ultimate resistance of each connector type and describing the failure mode at the interface .