Eco-efficient cements: Potential economically viable solutions for a low-CO2 cement-based materials industry

Sustainability in the construction industry: A review of recent developments based on LCA

American Society of Civil Engineers

A review of the present and future utilisation of FRP composites in the civil infrastructure with reference to their important in-service properties

This paper concerns the use of fine recycled concrete aggregates to partially or globally replace natural fine aggregates (sand) in the production of structural concrete. To evaluate the viability of this process, an experimental campaign was implemented in order to monitor the mechanical behaviour of such concrete. The results of the following tests are reported: compressive strength, split tensile strength, modulus of elasticity and abrasion resistance. From these results, it is reasonable to assume that the use of fine recycled concrete aggregates does not jeopardize the mechanical properties of concrete, for replacement ratios up to 30%.

Mechanical behaviour of concrete made with fine recycled concrete aggregates

Properties of concrete made with recycled aggregate from partially hydrated old concrete

The microstructure of recycled aggregate prepared from the crushing of old concrete was studied. It was found that the recycled aggregate is covered with loose particles that may prevent good bonding between the new cement matrix and the recycled aggregate. The old cement paste that remained on the natural aggregate was porous and cracked, leading to weak mechanical properties of the recycled aggregate. Treatment of the recycled aggregate by impregnation of silica fume solution and by ultrasonic cleaning was studied with the objective of overcoming the above-mentioned limitations. An increase of ~30 and ~15% in the compressive strength at ages 7 and 28 days was observed after the silica fume treatment. Ultrasonic treatment led to an improvement of ~7%.

Treatments for the Improvement of Recycled Aggregate

A novel methodology to estimate the evolution of construction waste in construction sites

Utilization of industrial by-products for the production of controlled low strength materials (CLSM)

The effect of high temperature on the bond between fiber reinforced polymers (FRP) reinforcing bars (rebars) and concrete was studied. The bond strength exhibited a severe reduction of 80–90% at relatively low temperature (up to 200°C), accompanied by changes in the pullout load-slip behavior. A semi-empirical model was developed in order to describe the extent of reduction in the bond strength as the temperature rises. The model is based on the following parameters: glass transition temperature of the polymer layer at the surface of the rod; polymer's degree of crosslinking; the residual bond strength at high temperature after the polymer of the external layer of the rebar ceased to contribute to the bond. The parameters of the rods that were tested for pullout at various temperatures were introduced into the model. The output curves of bond–temperature relationships showed good agreement with the test results.

Amnon Katz

Papers

Properties of concrete made with recycled aggregate from partially hydrated old concrete

Treatments for the Improvement of Recycled Aggregate

A novel methodology to estimate the evolution of construction waste in construction sites

Utilization of industrial by-products for the production of controlled low strength materials (CLSM)

Modeling the effect of high temperature on the bond of FRP reinforcing bars to concrete