Micromechanical Study of the Interface Properties in Concrete Repair Systems

Abstract

Micromechanical interface properties in a concrete repair system determine the performance and reliability of a repaired structure. In order to characterize these properties, nanoindentation technique was applied. Three different repair material mixtures, based on Portland cement or partial replacement of Portland cement with blast furnace slag, were tested. Hardness and elastic modulus values obtained from the nanoindentation were used directly as input for simulated direct tension test. This way, the fracture behaviour of original microstructure, "mimicked" by Delft lattice model, is analysed. Backscattered electron (BSE) image analysis is utilized to estimate the average size of the interface zone which is distinguished as locally more porous area. This, together with simulation results, is further used for calculation of the interface stiffness. Simulation results enable prediction and better insight into fracture propagation and micromechanical response of the tested zone. They also indicate the ratio between interface and bulk material fracture properties when different types of repair materials are used. Load displacement diagrams of interface, old and new material can serve as an input for numerical modelling and understanding of fracture behaviour of the repair systems at the higher scale. Potentially, this approach may develop as a tool for verifying and engineering interface properties such that desired performance of the repaired structure is achieved.

Combined experimental and numerical study of fracture behaviour of cement paste at the microlevel

“…Recently, in order to study the micromechanical properties between two materials (interface) and the properties of the bulk material itself, nanoindentation combined with a 2D numerical simulation of fracture was performed [19]. A number of locations, either at the interface between two materials (new and old cement paste) or within one of the materials, were tested by nanoindentation, and the measured properties were directly used as input for a simulated direct tension test.…”

Cracking of SHCC due to reinforcement corrosion

“…The indentation depth was set to 2000 nm.In the E modulus calculation, Poisson's ratio of the indented material (steel, rust, and cementitious material) was set to 0.25 in the calculations. More details about the procedure are given in [10].…”

Análise das propriedades de uma argamassa de reparo de base acrílica

“…Principalmente na zona de ligação entre materiais novos e antigos. As falhas nos serviços de reparo podem continuar prejudicando a estrutura, necessitando de retrabalhos [3].…”