Utilization of potentially alkali-silica reactive aggregates requires reliable performance tests to evaluate the alkali-silica reactivity of various aggregate combinations, including their alkali threshold dependence on binder type. Several such performance tests have been used worldwide for more than 15 years, but none of the methods have proven to be reliable for use with all aggregate types and all binders. One of the objectives of RILEM TC 219-ACS (2007-2012) is to develop and validate one or more of such performance tests. Several parameters may influence the results obtained in an accelerated performance test compared to the field behavior. Based on a state of the art literature review, this paper discusses which parameters must be considered to be able to develop reliable ASR performance testing methods and provides some tentative recommendations. The internal humidity in the test specimens, the extent of alkali leaching and the storage temperature are of particular importance.

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Problem-Based Learning, a methodology that builds on problems to develop students' new knowledge, can also be useful in helping students to learn Nature of Science. Prospective science teachers' conceptions regarding Nature of Science and its teaching through Problem-Based Learning were analyzed by applying a semi-structured interview. Nine respondents recognized that this methodology promote research activities and contribute to the learning of some aspects of scientific inquiry. Moreover, they specifically considered that Problem-Based Learning may foster the understanding of the tentative nature of scientific knowledge and of the role of creativity implicit in scientific endeavor. Authors consider that more attention should be given to the contemporary Nature of Science views and to its consistent teaching through this methodology.

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