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In 2009, a new methodology for the continuous monitoring of E-modulus of cement-based materials since casting was proposed, under the designation EMM-ARM (E-modulus Measurement through Ambient Response Method). This methodology is a variant to classic resonant frequency methods that allows continuous stiffness monitoring from the instant of casting. After the encouraging results obtained in the first applications of EMM-ARM to cement pastes, the present paper gives continuity to previous developments, through validations with additional experimental methodologies and extension to thermal activation testing. At first, a comparison is performed between the results of EMM-ARM and those obtained through: pulse velocity methods (both ultrasonic contact probes and bender-extender elements), penetration resistance (Vicat needle) and cyclic compression on cylindrical specimens. Afterwards, the possibility of studying the activation energy of the stiffness evolution on tests conducted at 20ºC and 40ºC is explored.

The use of embedded relative humidity (RH) sensors for assessing the internal humidity in concrete is widely spread, dully backed by existing standards. Even though the approaches adopted in the literature seem to have several differences between each other, few or none research works were found to focus on the comparison of performance of sensors and methods for RH measurement. In view of this, several sets of experiments comparing the performances of different sensors and monitoring procedures will be presented in this paper, discussing the main findings and providing recommendations for the strategies to be adopted in what concerns the measurement technique. The main points addressed in this work are: (i) comparisons between readily available systems for RH measurement in concrete, as well as custom measurement strategies reported in the literature; (ii) issues related to calibration procedures and re-calibration necessity; (iii) relevance of the existence of an interface porous material between the embedded sensor and the measurement spot in concrete; (iv) importance of the size of the embedment body into which the RH sensor is inserted; (v) equivalence of results obtained when the probe is constantly inserted into the embedment body, or placed inside it at discrete instants.

No abstract

The present work describes an integrated approach that leads to the development of a new model capable of describing the tensile behavior (mode I) of fiber reinforced concrete (FRC), considering the orientation of the fibers, the fibers segregation along the cross-section of the FRC members and the pullout constitutive model of each fiber bridging the two faces of a crack. The possibility of the numerical model to capture the flexural behavior of nonmetallic fiber reinforced concrete members is explored by simulating the response of polypropylene fiber reinforced concrete notched beams submitted to 3-point bending tests.