Filler Effect in Shotcrete

Galán, Isabel Moratilla; Briendl, Lukas; Thumann, Maria; Steindl, Florian Roman; Röck, Rudolf; Kusterle, Wolfgang; Mittermayr, Florian

doi:10.3390/ma12193221

Cited by 13 publications

(7 citation statements)

References 45 publications

(74 reference statements)

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“…In the case of shotcrete the use of setting accelerators may induce an earlier activation of the GGBFS [73]. Another commonly used supplementary material is powdered limestone, which forms CO 3 -AFm phases, stabilises ettringite and contributes to the formation of C-(A)-S-H [9,[74][75][76].…”

Section: Clinker Reduced Shotcrete: Influence Of Scmsmentioning

confidence: 99%

Durability of clinker reduced shotcrete: Ca2+ leaching, sintering, carbonation and chloride penetration

et al. 2021

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The reduction of clinker use is mandatory to lower the negative environmental impact of concrete. In shotcrete mixes, similarly to the case of conventional concrete, the use of supplementary cementitious materials (SCMs) and proper mix design allow for the substitution of clinker without compromising the mechanical properties. However, the impact of the substitution on the durability of shotcrete needs to be further assessed and understood. The results from the present study, obtained from real-scale sprayed concrete applications, show a reduction of the Ca2+ leaching and sintering potential of clinker-reduced shotcrete mixes due to the presence of SCMs. This positive effect, crucial for low maintenance costs of tunnels, is mainly related to a reduced portlandite content, which on the other hand negatively affects the carbonation resistance of shotcrete. Additionally, the hydration of SCMs positively influences the chloride penetration resistance presumably due to a combination of microstructural changes and changes in the chloride binding capacity. Differences found in the pore size distribution of the various mixes have low impact on the determined durability parameters, in particular compared to the effect of inhomogeneities produced during shotcrete application.

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Section: Clinker Reduced Shotcrete: Influence Of Scmsmentioning

confidence: 99%

Durability of clinker reduced shotcrete: Ca2+ leaching, sintering, carbonation and chloride penetration

et al. 2021

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“…A recent finding by Bentz et al [10] shows that fine limestone particles, the size of which is smaller than that of cement particles, may act as nucleation sites and accelerate the hydration of C 3 S. In general, the rate of acceleration is influenced by the particle size, crystal structure, and amount of limestone. Galan et al [11] reported that incorporating fine limestone (d 50 : 1.2 µm) into the samples improved the early-age mechanical properties. The early strength at 4 h improved by 150% when limestone powder was incorporated into the concrete.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Nucleation Acceleration Method with Calcium Carbonate and Calcium Silicate Hydrate for Fast-Track Construction

Yeo,

Mo,

Mahmud

2023

Buildings

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This research focuses on achieving early strength of cement-based materials through the hybrid nucleation acceleration method. Through the study of various mortar mixtures, which incorporate components such as ordinary Portland cement (OPC), fine limestone powder (with a particle size of d50: 1 μm), coarse limestone powder (with a particle size of d50: 12 μm), calcium silicate hydrate (C-S-H) nucleation seeding agent, and calcium nitrate (CN), the effect of the hybrid nucleation acceleration method was investigated. When OPC was substituted with 20% fine limestone powder, a strength of 13.5 MPa was achieved at 6 h, whereas the use of coarse limestone powder only yielded 3.5 MPa within the same time frame. The mortar containing 2% C-S-H nucleation seeding agent reached an impressive 16 MPa at 6 h. Meanwhile, through the synergistic combination of fine limestone powder and C-S-H nucleation seeding agent, the 6 h early strength attained an impressive 19 MPa. The micrograph revealed that the hybrid nucleation acceleration method significantly promoted the formation of a dense network of C-S-H within the paste, thus enhancing the packing density. Measuring the heat release demonstrated that the samples accelerated with the C-S-H nucleation seeding agent and fine limestone reached the peak 160 min earlier than the OPC sample, indicating a faster hydration process. The hybrid nucleation accelerated concrete (HNAC) achieved strengths of 20 MPa and 27 MPa within 6 and 8 h, respectively, whereas the 28-day strength surpassed 70 MPa. The concrete equivalent mortar (CEM), derived from concrete, attained a compressive strength of 25 MPa within 8 h, making it suitable for repair applications. The modulus of rupture (MOR) was 7.31 MPa at 8 h and increased to 17.27 MPa at 28 days. Overall, the developed concrete and CEM with the novel hybrid nucleation acceleration method allowed for high early and long-term strength for fast-track construction to be attained.

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“…Secundary ettringite formation in small pores (<50 nm) has been identified according to [5][6] as the main force to weakening the matrix due the cristallization in the pore. Other types can be adressed as gypsum secondary gypsum or thaumasite formation, aluminathe phases can react with Ca2+ or Na+ [6,7] To mitigate the consequences of the attack, most standards and recommendations rely on the specification of sulphate-resisting (SR) cements characterised by a limited C3A content (generally below 5% by cement weight [6][7]).…”

Section: Introductionmentioning

confidence: 99%

“…To illustrate it, Table 1 summarises the variables and experimental methods from studies published in the last 20 years about the ESA in sprayed or cast mixes with and without accelerators. [8,9] b: alkali-free(AF) or alkaline (AR) Notice that only [7] and [8] evaluate the influence of accelerators on the durability of sprayed mixes exposed to sulphates. Their findings suggest a link between the accelerators and the increase in the degradation induced by the ESA.…”

Section: Introductionmentioning

confidence: 99%

External sulphate attack of sprayed mortars with sulphate-resisting cement: Influence of accelerator and age of exposition

Herrera-Mesen

Salvador

Ikumi

et al. 2020

Cement and Concrete Composites

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This work evaluates the influence of the accelerator type, the cement type and age of exposure on the degradation mechanism and the durability of sprayed mortars subjected to external sulphate attack (ESA). Cores and prisms were extracted from panels sprayed with 8 mortar compositions (with 2 sulphate-resisting cement types and 4 setting accelerators) and then exposed to a sulphate solution at the ages of 7 or 28 days for 400 days. The evolution of the ESA was assessed through XRD, SEM, compressive strength, dimensional variation and ultrasonic pulse velocity. Results show that alkaline accelerators increase drastically the vulnerability of the matrix to the ESA. The degradation is enhanced by the higher solubility of aluminate phases and the increased formation of expansive phases. Results reveal that the use of sulphate-resisting cement might not suffice to mitigate severe material degradation.

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Filler Effect in Shotcrete

Cited by 13 publications

References 45 publications

Durability of clinker reduced shotcrete: Ca2+ leaching, sintering, carbonation and chloride penetration

Durability of clinker reduced shotcrete: Ca2+ leaching, sintering, carbonation and chloride penetration

Hybrid Nucleation Acceleration Method with Calcium Carbonate and Calcium Silicate Hydrate for Fast-Track Construction

External sulphate attack of sprayed mortars with sulphate-resisting cement: Influence of accelerator and age of exposition

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