Prüfverfahren zur Bestimmung des Versinterungspotenzials von Spritzbeton – Einflussfaktoren

Kusterle, Wolfgang; Pichler, Walter; Saxer, Andreas

doi:10.1002/best.201100072

Cited by 6 publications

(2 citation statements)

References 2 publications

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“…Upon curing for 28 days, the reduction rate of calcium ion dissolution is 11.19%, and the fly ash dosage is 20%. The mechanism of fly ash is mainly embodied in three aspects: morphological effect, activity effect, and microaggregate effect. , Fly ash mainly acts as a filler for the internal pores of shotcrete in the early stages of cement hydration. Its pozzolanic effect mainly occurs when the content of calcium hydroxide in shotcrete is high in the later stage of cement hydration.…”

Section: Resultsmentioning

confidence: 99%

Reducing Calcium Dissolution in Tunnel Shotcrete: The Impact of Admixtures on Shotcrete Performance

Tong,

Tian,

et al. 2024

Langmuir

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Groundwater infiltration into tunnels causes water to percolate through the fissure channels in the initial support shotcrete. This results in the dissolution and outflow of calcium hydroxide, a key product of cement hydration. This process significantly incurs the formation of crystallization blockages in the tunnel drainage systems. Optimizing the shotcrete mixing ratio is a feasible way to mitigate these blockages. Therefore, this study conducts calcium dissolution tests to investigate the impact of six admixtures, namely, antialkali agent, nanosilica, nanosilica carbonate, fly ash, sodium methyl silicate waterproofing agents, and silane waterproofing agents, on calcium dissolution resistance. Also, mechanical and microscopic tests are carried out to examine their impact on the strength and pore structure of the shotcrete. The objective of this study is to determine the optimal admixture for enhancing the calcium dissolution resistance of shotcrete. Results indicate that the antialkali agent significantly reduces the calcium leaching content of shotcrete. When the dosage is 14%, the calcium leaching amount is reduced by 68.4% in 28 days. Followed by nanosilica and silane waterproofing agents, with optimal dosages of 12 and 0.4%, respectively, the dissolution amount of calcium ions in shotcrete was reduced by 32.87 and 26.5%, respectively. Fly ash curing for 28 days can also reduce the calcium ion dissolution of shotcrete, while nanocalcium carbonate and sodium methyl silicate have little effect on the calcium dissolution of shotcrete. The antialkali agent with a strong calcium ion dissolution effect can improve the tensile strength of shotcrete under long-term curing conditions, which can be increased by 52%, but it compromises the growth of compressive strength. Nanosilica, fly ash, and silane waterproofing agents can improve both the compressive strength and tensile strength of shotcrete under long-term curing conditions. Specifically, at 28 days of curing, the compressive strength increased by 16.83, 28.8, and 20% and the tensile strength increased by 50.24, 60, and 64.5%. In addition, the microscopy results show that the antialkali agent, nanosilica, and silane waterproofing agents promote the hydration process of cement to form ettringite with a low and stable calcium−silicon ratio and reduce calcium hydroxide crystals. Nanosilica and silane waterproofing agents optimize the pore distribution in shotcrete by increasing beneficial pores, decreasing harmful pores, and reducing total porosity.

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Section: Resultsmentioning

confidence: 99%

Reducing Calcium Dissolution in Tunnel Shotcrete: The Impact of Admixtures on Shotcrete Performance

Tong,

Tian,

et al. 2024

Langmuir

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“…Es werden Kenntnisstand und aktuelle Herausforderungen der Bildung und Vermeidung von Versinterungen in Tunnelbauwerken vorgestellt, die in den nachfolgenden Beiträgen dieser Ausgabe der Geomechanics and Tunnelling vertiefend diskutiert werden [6,9,10]. tunnel drainage system [4]. Scale formation in tunnel drainage systems tends to intensify in the presence of calciumand carbonate-rich groundwater in combination with exposed building materials that readily mobilise calcium and hydroxides, e.g.…”

Section: Aktuell Erfolgreiche Ansätze Zur Vermeidung Derartigerunclassified

Prozesse der Versinterung – Kenntnisstand und aktuelle Herausforderungen

Dietzel

Eichinger

2022

Geomechanics and Tunnelling

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Scale formation in water drainage systems occurs in diverse forms. In tunnel drainage systems in particular, calcium carbonate deposition can significantly impair water discharge, resulting in costly maintenance work and tunnel closures. This review paper presents and discusses the state of knowledge as well as the current challenges regarding scale formation in tunnel drainage systems in terms of typification, parameters controlling formation, such as hydrochemistry, interfacial phenomena, microbial activity, and countermeasures, such as appropriate adaptation of construction materials, drainage design, inhibitor use and cleaning. Detailed knowledge of the case‐specific scale formation environment and the scaling capacities of the waters provides the basis for the tailored development and evaluation of suitable strategies for successfully reducing maintenance efforts and tunnel closure. For this purpose, time‐ and site‐resolved monitoring of the composition of the solid phases, waters and the tunnel atmosphere during the implementation of the construction project and during the operation of the tunnel is paramount.

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