Effects of key parameters on fluidity and compressive strength of ultra‐high performance concrete

Chang, Wei; Zheng, Wenzhong

doi:10.1002/suco.201900167

Cited by 25 publications

(9 citation statements)

References 44 publications

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“…The pH in the liquid environment can be effectively decreased by silica fume, which also restricts the reaction of fly ash. This phenomenon is also reported in other blended UHPC mixtures (Yu et al, 2015;Zhang et al, 2017;Chang and Zheng 2020).…”

Section: Mechanical Propertiessupporting

confidence: 85%

The Influence of Long-Term Autoclaving on the Properties of Ultra-High Performance Concrete

et al. 2022

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Thermal energy storage is a key component in harnessing renewable resources, compensating for the energy variations across time scales. A popular strategy for thermal energy storage is storing thermal energy in hot water tanks, which are generally made of copper, stainless steel, and vitreous enamel-lined carbon steel. However, these materials usually suffer a high production cost and short life cycle. UHPC with superior strength and durability holds the potential as a construction material for hot water tanks, which are commercially available and affordable for large-scale applications. During the charging process of hot water tanks, the UHPC structures are thus loaded by a long-term temperature-pressure load (autoclaving condition). However, the influence of long-term autoclaving on UHPC is still unclear. Therefore, the influence of long-term autoclaving at 200°C on the mechanical properties and microstructure of UHPC is studied here. The effect of the long-term autoclaving depends on the UHPC compositions. The compressive strength can stay robust owing to the accelerated formation of hydrates, while the flexural strength is vulnerable to the long-term autoclaving. Katoite, hydroxylellestadite, and scawtite are identified as the new hydrates in the autoclaved UHPC with typical components. The transformation of amorphous C-S-H into more ordered phases results in the low flexural strength and the undensified interface between the matrix and steel fibres. The partial replacement of cement by fly ash mitigates the detrimental effect of the long-term autoclaving. The incorporation of fly ash provides additional silica and increases the ratio of silica to cement, leading to more poorly crystallized C-S-H with a low Ca/Si ratio, which benefits microstructure densification and mechanical strength. The decrease of Ca/Si ratio and the increase of Al by fly ash accelerate the decomposition of katoite and hydroxylellestadite and formation of tobermorite. This study clarifies the influence of the long-term autoclaving on UHPC and provides guidance for developing an applicable and sustainable UHPC as the construction material for hot water tanks.

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Section: Mechanical Propertiessupporting

confidence: 85%

The Influence of Long-Term Autoclaving on the Properties of Ultra-High Performance Concrete

et al. 2022

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“…Ultra‐high performance concrete (UHPC) is a new category of fiber‐reinforced cement‐based composite material with ultra‐high strength, high toughness and high durability 1 . Applying UHPC to beams and columns can increase the bearing capacity of the structure, but the problem of brittle failure still exists.…”

Section: Introductionmentioning

confidence: 99%

Flexural behavior of ultra‐high performance concrete filled high‐strength steel tube

Deng

Sun

2021

Structural Concrete

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To research the flexural performance of ultra‐high performance concrete (UHPC) filled high‐strength steel tube (UHPCFST) and UHPC filled double skin high‐strength steel tube (UHPCFDST) under bending load, an experimental investigation was presented. In this paper, four UHPCFST specimens, one UHPCFDST with square tube inner specimen and three UHPCFDST with circular tube inner specimens were designed to evaluate the influence of steel ratio, steel yield strength, and cross‐section combination form on the flexural performance of the specimens. Experimental results indicated that the composite action between UHPC and high‐strength steel tube was efficient, all specimens showed ductile failure under pure bending load. As the steel ratio and steel yield strength increased, the ultimate flexural capacity of specimens significantly increased, but the changes of flexural stiffness were not obvious. The results also demonstrated that when the hollow section ratio was 0.535 to 0.567, the UHPCFDST with circular tube inner specimens had higher ultimate flexural capacity and ductility than the UHPCFST specimens. Compared with square inner tube, when the steel ratio was the same, circular inner tube was recommended for UHPCFDST specimens. An analytical model of ultimate flexural capacity for UHPCFST and UHPCFDST specimens was proposed. Compared with the three current codes, the accuracy of the model was proved.

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“…In addition, the low water ratio and high alkali environment led to a rupture of the Si–O and Al–O bonds within the USL particles. These fractures promoted the dissolution of the Si and Al ions and accelerated the pozzolanic reaction with calcium hydroxide(CH), which improved the compaction and compressive strength of the UHPC [ 41 , 42 ]. The LS particles reacted with the aluminate phase from the USL and the cement.…”

Section: Resultsmentioning

confidence: 99%

The Synergistic Effects of Ultrafine Slag Powder and Limestone on the Rheology Behavior, Microstructure, and Fractal Features of Ultra-High Performance Concrete (UHPC)

et al. 2023

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This study investigated the effect of the interaction between ultrafine slag powder (USL) and limestone (LS) on the rheology behavior, microstructure, and fractal features of UHPC. The results indicated that B2 with mass ratio of 2:1 between the USL and LS obtained the highest compressive strength and the lowest yield stress. The combination of the USL and LS facilitated the cement hydration, ettringite, and monocarboaluminate (Mc) formation, as well as the increase in the polymerization of the C–S–H. The synergistic action between the USL and LS refined the pore structure due to the formation of the Mc, compensating for the consumption of the CH by the pozzolanic reaction, which provided a denser microstructure in the UHPC. The fractal dimension (Ds) of the UHPC was strongly related to the concrete pore structures and the compressive strength, which demonstrated that a new metric called the Ds value may be used to assess the synergistic effect of the UHPC.

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Effects of key parameters on fluidity and compressive strength of ultra‐high performance concrete

Cited by 25 publications

References 44 publications

The Influence of Long-Term Autoclaving on the Properties of Ultra-High Performance Concrete

The Influence of Long-Term Autoclaving on the Properties of Ultra-High Performance Concrete

Flexural behavior of ultra‐high performance concrete filled high‐strength steel tube

The Synergistic Effects of Ultrafine Slag Powder and Limestone on the Rheology Behavior, Microstructure, and Fractal Features of Ultra-High Performance Concrete (UHPC)

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