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This article presents the results of an interlaboratory experimental study performed by 13 international research groups within the framework of the activities of the RILEM Technical Committee 225-SAP ''Applications of Superabsorbent Polymers in Concrete Construction''. Two commercially available superabsorbent polymers (SAP) were tested in terms of their influence on the freeze-thaw resistance of ordinary concrete. To test the robustness of the method, all participating laboratories used locally produced materials. Furthermore, following this aim, various accelerated methods were used to estimate the resistance of the concrete to freeze-thaw cycles. The effect of adding SAP was from insignificant to

Superabsorbent polymers (SAP) are a new, promising class of chemical admixtures which offer new possibilities in respect of influencing the properties of cement-based materials in the fresh, hardening, and hardened states. Much research work has been done in the last two decades to set the stage for introducing this truly multipurpose agent into the practice of construction. In particular, three RILEM Technical Committees: 196-ICC, 225-SAP and 260-RSC contributed considerably to the related progress by coordinating and combining the efforts of international experts in the field. The major product of the RILEM TC 225-SAP work was the State-of-the-Art Report published in 2012. This comprehensive document covered all topics relevant to the application of SAP as a concrete admixture. Since then further important progress has been made in understanding the working mechanisms of SAP in concrete and the effects of SAP-addition on various concrete properties. The article at hand presents an update on the state-of-the-art and is the concluding document delivered by the RILEM TC 260-RSC.

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Stress redistribution and stress drop often coincide with fracture processes. The two experiments that were chosen for our b-value analysis generate failure processes with the corresponding stress drops and stress redistributions. Using acoustic emission analysis, the acoustic waves emitted from the different fracture areas are recorded. The cumulative frequency-magnitude distribution, which leads to the b-value, was originally used in seismology to characterize earthquake populations. Concerning acoustic emissions, the b-value decreases with increasing stress levels. Therefore, it was possible to determine the start of the arise of macro-cracks over time using the b-value analysis. Furthermore, a possible application in a monitoring procedure is suggested.