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WP2_Development and testing of materials

Purpose

The purpose of WP2 is 1) to develop a model for the rheological properties of steel fibre reinforced SCC, including develop principles for producing concrete using steel fibre reinforced SCC, 2) to develop and examine standard testing methods of the mechanical properties of fibre reinforced concrete, 3) to develop new fibres especially suited for load bearing structures.

Research contents

Models will be developed for the relation between the concrete composition and the rheological properties in order to produce a fibre reinforced SCC that meets the stated requirements using local materials. The material model will be based on composite theory, which considers particles (gravel and fibres) part of a liquid fluid (mortar). The model will also use the packing theory for determining the maximum aggregate and fibre contents. Principles must be developed for concrete production of steel fibre reinforced SCC that ensure an adequate dispersion of steel fibres and ensure that the concrete obtains the right rheological properties. This includes optimization of mixing sequence, mixing time and algorithms to manage any adjustments during the process based on online monitoring of the consistency of the concrete in the mixer. For this monitoring, it is the plan to use the Viscoprobe developed by Convi. Examinations will focus on translating parameters measured in the mixer into the fundamental rheological parameters that the manufacturer will encounter in future requirement specifications from consultants and contractors. In this case, the objective is especially to analyse the flow conditions that the Viscoprobe is subjected to during mixing that together with the actual resistance measurement on the Viscoprobe will be used for calibrating against rheological data measured using, e.g., BML viscometer and 4C?]Rheometer. The results of steel fibre reinforced concrete with different rheology will be used to assess the optimum placement and design of the Viscoprobe.

We need a model for describing how the measured tensile properties are to be classified and used in structural design. Furthermore, it is essential to examine and quantify the link to the underlying fracture mechanical properties, described through the mixed mode fracture mechanical models, which will be used for actual design simulation (WP 1.2). A detailed analysis will be carried out of existing, suggested test methods for determining mechanical properties by means of the simulation tool established in WP 1.2. The outcome of the analysis will be recommendations on the use of the results of such test methods in simplified design calculation methods, WP 3. The link between results of standard tests and the fracture mechanical properties of the fibre concrete will be verified through an experimental programme.

Fibre design, including length, thickness and other geometry, greatly impacts the fibres' contribution to the mechanical properties of the concrete. It differs what properties the fibres are to provide the concrete, depending on the different applications. When fibres are used for floors as crack dispersion, certain geometries are preferred, and when fibres are to a have structural function ?] e.g., in load bearing structures ?] other geometries are preferred. The development of steel fibres will aim to create a type of fibre that is especially suited for load bearing structures.

Leader of work package 2

Danish Technological Institute