Chapter 2 - Fundamentals of hydrodemolition

Abstract

This chapter explains kinematics of high-speed water jets and elaborates the structure of high-speed water jets. If the jet hits a solid surface, a stagnation pressure profile forms at that surface. Several authors measured the profile shape, and approximate equations were derived. Important information about the response of concrete to water jet loading is stored in the structure of fracture faces. Depending on loading regime and material structure, two general types of macroscopic failure can be distinguished: sections without brittle fracture features, and sections with dominant brittle fracture features. Conventional properties of concrete—namely, strength parameters, cannot characterize the resistance against water jet erosion. Resistance is proportional to pore slenderness and it decreases if, for a given pore slenderness, the grain size decreases. The process parameter effects on material removal are also discussed including the pump pressure effects, nozzle diameter effects, stand-off distance effects, traverse rate effects, traverse increment effects, impact angle effects, and nozzle movement effects. Compressive strength is the standard strength parameter of concrete that can be evaluated under site conditions as well. The most common method is to use cylinder cores drilled off the structure. The chapter concludes with the hydrodemolition method for estimating depth of cut as well as material removal rate for hydrodemolition applications.