A critical review and assessment for usage of recycled aggregate as sustainable construction material

The properties of new Interfacial Transition Zone (ITZ) and old ITZ in Recycled Aggregate Concrete (RAC) were investigated by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and nanoindentation. From the SEM images, obvious voids and high concentration of calcium hydroxide can be found in both old ITZ and new ITZ in RAC. Based on the nanoindentation study, it is indicated that the thicknesses of old and new ITZs are in the range 40–50 μm and in the range 55–65 μm, respectively. It is also found that the average indentation modulus of old ITZ is 70–80% of that of old paste matrix, while the average indentation modulus of new ITZ is 80–90% of that of new paste matrix. Additionally, the influences of mix proportion, aggregate types and hydration age on the properties of ITZs in RAC are discussed in this study.

Properties of interfacial transition zones in recycled aggregate concrete tested by nanoindentation

Meso-scale computational modeling of the plastic-damage response of cementitious composites

3D experimental investigation of the microstructure of cement pastes using synchrotron X-ray microtomography (μCT)

Pore Segmentation of Cement-based Materials from Backscattered Electron Images

This paper describes the so called interfacial transition zone—ITZ—in concrete. This is the region of the cement paste around the aggregate particles, which is perturbed by the presence of the aggregate. Its origin lies in the packing of the cement grains against the much larger aggregate, which leads to a local increase in porosity and predominance of smaller cement particles in this region. The ITZ is region of gradual transition and is highly heterogeneous, nevertheless the average microstructural features may be measured by analysis of a large numbers of backscattered electron images of polished concrete samples. Such measurements show that the higher porosity present initially is significantly diminished by the migration of ions during hydration.

The Interfacial Transition Zone (ITZ) Between Cement Paste and Aggregate in Concrete

The application of quantitative image analysis to the measurement of microstructural gradients in the interfacial zone in concrete is described. Some preliminary results are presented and discussed.

A Stludy of the Interfacial Region Between Cement Paste and Aggregate in Concrete

The durability of concrete is strongly dependent on the distribution of porosity particularly in the surface layers. To study this distribution, concretes at different water to cement ratios were studied by methanol counter diffusion and by analysis of backscattered electron images. The distribution of porosity in the surface was compared with that in the bulk. Samples of the same concrete were imnersed in sodium sulphate solutions while others were left in lime water as a control. The effects of the immersion on the microstructure was studied with backscattered electrons in the SEM.

Alison K. Crumbie

Papers

The Interfacial Transition Zone (ITZ) Between Cement Paste and Aggregate in Concrete

A Stludy of the Interfacial Region Between Cement Paste and Aggregate in Concrete

The Relationship Between The Porosity And Permeability Of The Surface Layer Of Concrete And The Ingress Of Aggressive Ions