Pedro Faustino

Lifetime modelling of chloride-induced corrosion in concrete structures with Portland and blended cements

Abstract This article discusses mathematical modelling of the long-term performance of concrete with different supplementary cementitious materials in a maritime environment. The research was carried out in the light of the national Portuguese application of the CEN standards with mandatory requirements for a performance-based design approach. Laboratory investigations were performed on concrete compositions based on CEM I and CEM II/B-L in which the cement was partially replaced by either 0% (reference composition) or 50% of low calcium fly ash (FA). Concrete compositions were made with the objective to achieve service lives of 50 and 100 years with regard to steel corrosion. Test results of compressive strength, chloride potential diffusion and electrical resistivity are reported for different curing ages of 28, 90, 180 and 365 days. Chloride diffusion results were used for the implementation of modelling equations in order to estimate the design lifetime regarding reinforcing steel corrosion. A performance-based approach using a probabilistic method was carried out and the results obtained are compared with the requirements according to the Portuguese prescriptive approach. The modelling results show that FA blended compositions have better performance compared to those with Portland cements, especially if curing ages beyond 28 days are considered.

Lifetime prediction of reinforced concrete structures in carbonation environments carbonation modelling vs air permeability modelling

AbstractThis article compares two models for the prediction of lifetimes of reinforced concrete structures in carbonation environments based on different tests: carbonation test-based modelling and air permeability test-based modelling. The study also includes experimental testing of five concrete mixes with different types of cement in order to validate the models using safety factors. The tests included compressive strength, accelerated carbonation and air permeability. Both models are defined in a European standard as being alternative to each other, meaning that their results for the same concrete composition and the same environment should converge. The results show that both current models can scarcely constitute alternative to each other. Design lifetime results are far from similar for each concrete mix and each exposure class. The different nature of each test – accelerated carbonation and air permeability – and their different characteristic such as the scattering of results and the unrelated pa...

Flexural Strengthening of Columns with CFRP Composites and Stainless Steel: Cyclic Behavior

AbstractThis study presents the testing, completion, and analysis of different external strengthening systems applied to rectangular reinforced concrete columns with rounded corners. The experimental study included confinement strengthening with carbon-fiber-reinforced polymer (CFRP) sheets, longitudinal strengthening with CFRP laminates and confining CFRP jacket, longitudinal strengthening with stainless steel bars and confining CFRP jacket, tested column until reinforcing steel failure, repair and CFRP confining jacket, and longitudinal strengthening with stainless steel bars. The analysis of the experimental results included lateral load-displacement relationship, energy dissipation, ductility, and curvature damage assessment classifications. It was concluded that the use of external longitudinal strengthening combined with CFRP confinement is effective for enhancing performance and is viable in terms of execution. The load capacity increase due to strengthening reached 36–46% with good ductile behavio...