Long-term strength of shotcrete with improved C12A7 based mineral accelerator

Won,

doi:10.9711/ktaj.2013.16.2.135

Cited by 2 publications

(3 citation statements)

References 3 publications

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“…NaAlO 2 and KAlO 2 are the main components of the aluminate accelerators, which are mainly used when a large thickness (>15 cm) after excavation and high early strength support are required [ 8 ].…”

Section: Test Process and Methodsmentioning

confidence: 99%

“…According to previous studies, an aluminate accelerator is used to improve the cement hydration and its quick setting [ 6 ]. In addition, the alkali-free accelerator has a less alkaline content, pH of 0–7, and a long-term strength effect reduction with a low caustic performance [ 7 , 8 ]. Moreover, cement mineral accelerators (C 12 A 7 ) were used to estimate shotcrete performance after 28 days for compressive and flexural strength showing enhancement and durability [ 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Long-Term Strength Development of Steel Fiber Shotcrete with Cast Concrete Based on Accelerator Type

Yun

Choi

et al. 2020

Materials

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This study analyzed the effect of accelerating agents, such as aluminate, cement mineral, and alkali-free accelerators, on the long-term performance of steel-fiber-reinforced shotcrete. The shotcrete performance was studied based on the type and amount of steel fiber added. Performance tests were performed to identify the accelerator providing better long-term performance to the steel-fiber-reinforced shotcrete. Changes in strength and flexural performance over time were investigated. The compressive strength and flexural strength tests on 1-, 3-, 6-, 12-, and 24-month-old test specimens were performed, wherein 37 kg of steel fiber was added to the cement mineral and aluminate mixes, and 40 kg of steel fiber was added to the alkali-free mix. The 1-month compressive strength result of all the test variables satisfied the Korea Expressway Corporation standard. The compressive strength of the cast concrete and shotcrete specimens increased with age, demonstrating a strength reduction, particularly in the 24-month-old shotcrete specimens. Thus, the shotcrete performance may deteriorate in the long-term. In the 24-month-old specimen, substantial flexural strength reduction was observed, particularly in the aluminate and alkali-free specimens. The relative strength of the specimens was compared with that of the cast concrete mold specimens. The results suggest the use of alkali-free accelerators, considering the long-term performance of tunnels and safety of workers. Moreover, increasing the steel fiber performance rather than the amount of low-performance steel fiber must be considered.

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Section: Test Process and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparison of Long-Term Strength Development of Steel Fiber Shotcrete with Cast Concrete Based on Accelerator Type

Yun

Choi

et al. 2020

Materials

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“…In addition, the alkali-free has less alkaline content, and thus a pH of 0–7, as well as a reduction in the long-term strength effect with a low caustic performance [ 9 , 10 ]. Cement mineral accelerators (C12A7) were used to estimate the performance of the shotcrete of the 28 days compressive and flexural strength with enhanced durability [ 10 , 11 ]. In this research, three types of accelerators were used to determine the mechanical long-term performance of the tunnel shotcrete, and accelerators incorporated with steel fibers were applied for a better shotcrete performance.…”

Section: Introductionmentioning

confidence: 99%

Long-Term Compressive Strength Development of Steel Fiber Shotcrete from Cores Based on Accelerator Types at Tunnel Site

Yun

Choi

et al. 2021

Materials

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In this study, cement minerals, aluminates, and alkali-free accelerators incorporated with steel fiber were used to scrutinize the influence of accelerating agents on the long-term performance of tunneling shotcrete. Performance tests were identified based on the core compressive strength of mix shotcrete specimens with different types of accelerating agents throughout timeframes of 1, 3, 6, and 12 months. Here, 37 kg of steel fiber was incorporated into the cement mineral and aluminate mixes, and 40 kg of steel fiber was incorporated in an alkali-free mix for the shotcrete mix design. The KSF 2784 and ASTM 214 standards were followed for specimen fabrication and core cutting. For all specimens, shotcrete test panels of 250 × 600 × 500 mm were manufactured for core compressive strength tests conducted using 100, 75 and 55 mm diameter cylindrical molds and a length-to-diameter ratio of 2. The 1-month compressive strength of all test variables satisfied the Korea Expressway Co. standard of 21 MPa. The core compressive strength of the shotcrete specimens showed a tendency to increase with age, but a strength reduction occurred in 6 months and increased again at 12 months. Moreover, the impact of the diameter changes in the shotcrete core specimens was analyzed based on the mixing. For 12 months, a large increase in the core compressive strength occurred, particularly in the alkali-free specimens. The comparison also focused on the relative strength compared with a cast concrete mold and shotcrete core specimens. It is necessary to use alkali-free accelerators considering the long-term performance of tunnels and worker safety.

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Long-term strength of shotcrete with improved C12A7 based mineral accelerator

Cited by 2 publications

References 3 publications

Comparison of Long-Term Strength Development of Steel Fiber Shotcrete with Cast Concrete Based on Accelerator Type

Comparison of Long-Term Strength Development of Steel Fiber Shotcrete with Cast Concrete Based on Accelerator Type

Long-Term Compressive Strength Development of Steel Fiber Shotcrete from Cores Based on Accelerator Types at Tunnel Site

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