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Erschienen in:
2020 | OriginalPaper | Buchkapitel
Comparative Study on the Effect of Mixer Type on Properties of Self-compacting Mortar
verfasst von : Bart Craeye, Wim Bastiaens, Erik Coppens, Dirk Van Houdt, Wilfried Gijbels, Thomas Rondou
Erschienen in: Rheology and Processing of Construction Materials
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Abstract
For the realisation of safe, permanent and sustainable solutions for the management of short-lived low and intermediate level radioactive waste in Belgium, this radwaste is placed in concrete caissons and subsequently encapsulated with mortar to form a monolith, placed in a near surface disposal facility. This high-performance self-compacting mortar consists of an inert calcareous matrix (filler and sand), blast furnace slag cement, microsilica and naphthalene sulfonate superplasticizer (dry-powder type and liquid-based type), with a water/cement ratio of approximately 0.36. As considerable amount of this cementitious material is needed, it is necessary to come to an easily manageable and repeatable mixing and casting procedure.
Therefore, an intensive experimental program was conducted to evaluate the effect of different mixer types on the consistency of fresh state (slump flow, V-funnel, air content and volumetric weight), the hardened properties at different ages (both compressive and flexural strength, modulus of elasticity and coefficient of thermal expansion) and porosity accessible to water (including segregation risk). Four different mixers were considered in this study, with different working principle and capacity: (i) forced action pan mixer, (ii) ring pan mixer, (iii) paddle mixer (ploughshare), and (iv) twin shaft mixer. For durability related reasons, porosity and segregation risk have a decisive effect on the choice of mixer to be used for further (upscaled) research.
It was found that the mixing procedure, scale and type has an impact on the previously mentioned properties of the self-compacting mortar. Lowest porosity is obtained by means of ploughshare mixer in combination with dry superplasticizer, while the lowest segregation risk is obtained for TS mixer, regardless the type of superplasticizer.