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- Spent equilibrium catalyst as internal curing agent in UHPFRCPublication . Matos, Ana Mafalda; Nunes, Sandra; Costa, Carla; Aguiar, J. B.The main goal of the current paper is to optimize ultra-high performance cementitious material (UHPC) mixes incorporating the spent equilibrium catalyst (ECat) to mitigate autogenous shrinkage. Design of experiments approach was used to optimize mixtures targeting different engineering properties, namely, self-compactibility, low early-age shrinkage and cracking risk, improved durability and high mechanical performance. The statistical models established indicated that ECat exhibits a strong positive effect on the autogenous shrinkage mitigation of UHPC attributed to the water absorbed in the porous of ECat particles. The proposed optimal UHPC mixture represents the best compromise between low autogenous shrinkage - 32% of reduction - and high resistivity at 28 days without impairing self-compatibility and compressive strength. This optimal UHPC combined with 3% high-strength steel fibres (l(f)/d(f) = 65) proved to be comparable to other Ultra High-Performance Fibre Reinforced Composites (UHPFRC), in terms of mechanical behaviour, and more eco-friendly and cost-efficient than UHPCs reported in the literature.
- Durability of an UHPC containing spent equilibrium catalystPublication . Matos, Ana Mafalda; Nunes, Sandra; Costa, Carla; Aguiar, JoséUHPC is an advanced cementitious material able to meet the current construction industry challenges regarding structural safety and durability. However, new UHPC formulations with limited shrinkage are still being pursued to reduce residual tensile stresses in the UHPFRC layers, for rehabilitation/strengthening applications. This investigation estimates the durability of a non-proprietary UHPC incorporating a by-product originated by the oil refinery industry (ECat), as an internal curing agent. Direct and indirect transport properties measurements as well as the carbonation assessment and evaluation of dimensional resilience to potential deleterious reactions revealed that the new UHPC possesses an excellent durability performance, typical of these materials. These results combined with its self-compacting ability, low autogenous shrinkage and high compressive strength confirm the belief in the role of this new UHPC towards a high-tech construction.