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.

This article presents the results of a round-robin test performed by 13 international research groups in the framework of the activities of the RILEM Technical Committee 260 RSC "Recommendations for use of superabsorbent polymers in concrete construction". Two commercially available superabsorbent polymers (SAP) with different chemical compositions and gradings were tested in terms of their kinetics of absorption in different media; demineralized water, cement filtrate solution with particular cement distributed to every participant and local cement chosen by the participant. Two absorption test methods were 2 considered; the tea-bag method and the filtration method. The absorption capacity was evaluated as a function of time. The results showed correspondence in behaviour of the SAPs among all participants, but also between the two test methods, even though high scatter was observed at early minutes of testing after immersion. The tea-bag method proved to be more practical in terms of time dependent study, whereby the filtration method showed less variation in the absorption capacity after 24 hours. However, absorption followed by intrinsic, ion-mediated desorption of a respective SAP sample in the course of time was not found by the filtration method. This SAP-specific characteristic was only displayed by the teabag method. This demonstrates the practical applicability of both test methods, each one having their own strengths and weaknesses at distinct testing times.

This paper evaluates the effect of superabsorbent polymers (SAP) on hydration and microstructure of PC-GGBS mortars. Development of autogenous shrinkage, microstructural characteristics (MIP/SEM) and compressive strength were analysed during the first 90 days. Four levels of Portland cement (PC) replacement by GGBS (0%, 25%, 50% and 75%) and two types of SAP with different water absorption capacities were considered. The results proved the efficiency of internal curing by SAPs in PC-GGBS systems due to significant reduction in autogenous shrinkage, especially for higher contents of GGBS. SAP facilitates GGBS hydration activated by portlandite; its products can be deposited into the nano pores leading to a small relative expansion of the hardened bulk volume. This process is initiated during the second week and it lasts until the sixth week. Despite increased total porosity, compressive strength of SAPs modified mortars is comparable to the reference samples for low GGBS contents in advanced ages.

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Resumobagaço é gerado como resíduo do processamento do açúcar e do álcool. Esse resíduo é utilizado para a cogeração de energia por meio da queima em caldeiras, restando ao final as cinzas residuais do bagaço da cana-de-açúcar (CBC). Atualmente, essas cinzas são aproveitadas nas lavouras de cana como adubação orgânica, apesar de ser um material com poucos nutrientes. O objetivo deste trabalho foi avaliar a durabilidade de concretos que utilizaram a CBC em substituição ao agregado miúdo por meio de ensaios de carbonatação e abrasão. Os resultados foram comparados aos obtidos para um concreto sem CBC. Os concretos foram dosados para que tivessem a mesma consistência e o mesmo teor de argamassa. Produziram-se traços com 0%, 30% e 50% de CBC, em substituição ao agregado miúdo em três grupos diferentes. Foram realizados ensaios mecânicos e, a partir dos resultados obtidos, os concretos que apresentaram os melhores resultados foram submetidos ao ensaio de carbonatação, nas idades de 60, 120 e 210 dias, e ao ensaio de abrasão superficial, aos 28 dias. Os resultados obtidos permitiram concluir que a carbonatação e a abrasão do concreto produzido com a CBC como substituto parcial do agregado miúdo e o cimento CP II E 32 são similares ao concreto sem adição da cinza. Palavras-chave:Concreto. Cinza do bagaço da cana-de-açúcar. Durabilidade. AbstractThe bagasse is generated in the sugar and alcohol production process. This waste is used for cogeneration of electricity by burning it in boilers and at the end it produces sugarcane bagasse ash (SBA)

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