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A B S T R A C TThe aim of this work was to demonstrate the feasibility of producing Portland cement clinker upon direct exposure of the raw materials under concentrated solar radiation using the PSA high concentration solar furnace SF40. For this purpose, a short thermal cycle (< 40 min) was devised including 5 min dwell times at temperatures in the range 900-950°C and 1250-1300°C, followed by 10-15 min at 1500-1550°C. The chemical and mineralogical data of the grey clinker produced are encouraging since values of 51.0 ± 6.9% C 3 S, 22.7 ± 5.3% C 2 S, 8.6 ± 0.4% C 3 A and 10.8 ± 0.7% C 4 AF are similar to those observed for conventional clinker used for the production of Portland cement in accordance to EN 197-1 standard. White clinker, in turn, could not be produced by direct irradiation in this setup conditions because of its low absorptance of solar energy.

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.

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The service life of reinforced concrete structures is assessed for carbonation environments using mathematical models based on different tests: carbonation test-based modelling and air permeability test-based modelling. The study includes experimental testing of five concrete mixes with respect to compressive strength, accelerated carbonation and air permeability with different types of cement, in order to assess the models using probabilistic calculus. Both mathematical models are part of the Portuguese National Annex to the European standard EN 206 for the estimation of design service life. Engineers have the option of choosing which of the two models to use, which means that using either model should produce similar results. The design service life results show that the two models do not converge. The different principle of each test – accelerated carbonation and air permeability – and their different characteristics regarding the various parameters of the modelling equations are some of the aspects discussed.

This 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 parameters of the modelling equations are some of the features discussed, including the possibility of using different safety factors as function of the model and definition of possible correlation between tests.

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