Effect of Different Curing Regimes on Strength and Transport Properties of UHPC Containing Recycled Steel Tire Wires as Micro Steel Fibers

Kasaei, Jamil; Esmaeili, Jamshid

doi:10.21838/uhpc.2016.72

Cited by 2 publications

(1 citation statement)

References 7 publications

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“…Additionally, by the availability of water released with the decomposition of ettringite at temperatures above 70°C [14,19] the large amount of unhydrated cementitious components commonly remaining in hardened UHPC can be activated. In this way, the early strength is always considerably increased and in certain cases also the 28 days strength [13][14][15][20][21][22]. The intensified pozzolanic and hydraulic reactions result in a denser and more homogeneous microstructure of the cement paste matrix corresponding to an improved durability [23].…”

Section: Thermal Treatmentmentioning

confidence: 99%

Thermal and hydrothermal treatment of UHPC: influence of the process parameters on the phase composition of ultra-high performance concrete

et al. 2021

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Several studies show that thermal and hydrothermal treatment can further improve the excellent properties of UHPC in terms of mechanical strength and durability. While for the thermal treatment the increase in strength is attributed to an intensified pozzolanic and hydraulic reaction, for the hydrothermal treatment previous studies accredited it mostly to the formation of tobermorite. In the presented study thermal and hydrothermal treatment of UHPC samples was systematically varied and the phase formation analysed related to the strength development of a reference sample cured for 28 days in water. For the thermal treatment the results show that the strength increase depends on the protection against desiccation and can be ascribed to an improved pozzolanic reaction of the siliceous fillers. To achieve a significant enhancement of strength, a pre-storage time of few days and a long dwell time at elevated temperature/pressure are required. For the hydrothermal treatment already heating the specimens up to 185 °C in saturated steam followed by an immediate cooling leads to a substantial increase in compressive strength. Pre-storage time did not affect the result as far as a minimum of several hours is guaranteed. The improved performance is due to an increase in the pozzolanic and hydraulic reaction. Surprisingly, tobermorite was only found within a very thin layer at the surface of the sample, but not in the bulk. Sulphate and aluminium stemming from the decomposition of the ettringite are bound in the newly formed phases hydroxylellestadite and hydrogarnet.

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