Study on carbonation resistance and micromechanism of shotcrete in high geothermal tunnels

Carbonation durability is an important subject for recycled coarse aggregate concrete (RAC) applied to structural concrete. Extensive studies were carried out on the carbonation resistance of RAC under general environmental conditions, but limited researches investigated carbonation resistance when exposed to chloride ion corrosion, which is an essential aspect for reinforced concrete materials to be adopted in real-world applications. This paper presents a study on the carbonation durability of two generations of 100% RAC with the effect of chloride ion corrosion. The quality evolution of recycled concrete coarse aggregate (RCA) with the increasing recycling cycles was analyzed, and carbonation depth, compressive strength and the porosity of RAC were measured before and after chloride ion corrosion. The results show that the effect of chloride ion corrosion negatively affected the carbonation resistance of RAC, and the negative effect was more severe with the increasing recycling cycles of RCA. Chloride ion corrosion led to a decrease in compressive strength, while an increase in carbonation depth and the porosity of RAC. The equation of concrete total porosity and carbonation depth was established, which could effectively judge the deterioration of carbonation resistance of RAC.

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Durability and Time-Dependent Properties of Low-Cement Concrete

Materials ◽

10.3390/ma13163583 ◽

2020 ◽

Vol 13 (16) ◽

pp. 3583 ◽

Cited By ~ 1

Author(s):

Keila Robalo ◽

Eliana Soldado ◽

Hugo Costa ◽

Luís Carvalho ◽

Ricardo do Carmo ◽

...

Keyword(s):

Concrete Cover ◽

Time Dependent ◽

Sustainable Construction ◽

Cement Concrete ◽

Carbonation Resistance ◽

Shrinkage And Creep ◽

Binder Ratio ◽

Reference Curves ◽

Long Lifetime ◽

Formulation Parameters

The sustainability concerns of concrete construction are focused both on the materials’ eco-efficiency and on the structures’ durability. The present work focuses on the characterization of low cement concrete (LCC), regarding time-dependent and durability properties. LCC studies which explore the influence of the formulation parameters, such as the W/C (water/cement ratio), W/Ceq, (which represents the mass ratio between water and equivalent cement), W/B (water/binder) ratio, and the reference curves, on the aforementioned properties are limited. Thus, several LCC mixtures were formulated considering two dosages of binder powder, 350 and 250 kg/m3, the former with very plastic consistency and the latter with dry consistency, which were combined with a large spectrum of cement replacement rates (up to 70%), through adding fly ash and limestone filler, and with different compactness levels. The main objectives were to study the influence of the formulation parameters on the properties: shrinkage and creep, accelerated carbonation and water absorption, by capillarity, and by immersion. The lifetime of structures produced with the studied LCC was estimated, considering the durability performance, regarding the carbonation effect on the possible corrosion of the steel reinforcement. LCC mixtures with reduced cement dosage and high compactness, despite the high W/C ratios, have low shrinkage and those with higher strength have reduced creep, however depending on W/Ceq ratio. Those mixtures can be formulated and produced presenting good performance regarding carbonation resistance and, consequently, a long lifetime, which is mandatory for a sustainable construction. LCC with 175 kg/m3 of cement dosage is an example with higher lifetime than current concrete with 250 kg/m3 of cement; depending on the XC exposure classes (corrosion induced by carbonation), the amount of cement can be reduced between 37.5% and 42%, since the LCC with 175 kg/m3 of cement allows reducing the concrete cover below the minimum recommended, ensuring simultaneously the required lifetime for current and special structures.

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Carbonation Resistance of Surface Protective Materials Modified with Hybrid NanoSiO2

Coatings ◽

10.3390/coatings11030269 ◽

2021 ◽

Vol 11 (3) ◽

pp. 269

Author(s):

Kailun Xia ◽

Yue Gu ◽

Linhua Jiang ◽

Mingzhi Guo ◽

Lei Chen ◽

...

Keyword(s):

Construction Material ◽

Chemical Components ◽

Gravimetric Analysis ◽

X Ray Diffraction ◽

Carbonation Depth ◽

X Ray ◽

Carbonation Resistance ◽

Ideal Situation ◽

Caco3 Content ◽

Reference Samples

To date, reinforcement concrete is the main construction material worldwide. As the concentration of atmospheric CO2 is steadily increasing, carbonation of the reinforcement concrete becomes a pressing concern. In this study, novel surface protective materials (SPMs) modified with hybrid nanoSiO2 (HNS), fly ash, and slag were developed to reduce CO2 emissions and extend the service life of the reinforcement concrete. The carbonation depths were measured by phenolphthalein to reflect the carbonation resistance. X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) were conducted to analyze the chemical components of the samples after carbonation. In addition, MIP was carried out to examine the microstructures of the samples prior to carbonation. Thermodynamic modeling was employed to calculate the changes in the phase assemblages of each blends in an ideal situation. The experimental results showed that the carbonation depth and CaCO3 content of the SPM modified with HNS decreased by 79.0% and 64.6% compared with the reference, respectively. The TGA results showed that after carbonation, the CaCO3 contents were 4.40% and 12.42% in the HNS modified samples and reference samples, respectively. MIP analysis demonstrated that the incorporation of HNS in SPM led to a 48.3% and 58.5% decrease in big pores and capillary pores, respectively. Overall, the SPMs modified with HNS in this study possessed better carbonation resistance and refined pore structures.

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Experimental Studies on the Carbonation Resistance Performance of Iron Tailings Concrete

SSRN Electronic Journal ◽

10.2139/ssrn.3995313 ◽

2021 ◽

Author(s):

Ruolan Zhang ◽

Jianheng Sun ◽

Xinxin Ma ◽

Yuhan Bai ◽

Zhiliang Meng

Keyword(s):

Experimental Studies ◽

Carbonation Resistance ◽

Resistance Performance

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EFFECTS OF DEMOLDING AGE ON THE STRENGTH DEVELOPMENT AND THE CARBONATION RESISTANCE OF LOW-HEAT PORTLAND CEMENT FLY ASH SYSTEM MATERIALS, AND NONDESTRUCTIVE EVALUATIONS OF THEIR SURFACE QUALITIES

Cement Science and Concrete Technology ◽

10.14250/cement.64.203 ◽

2010 ◽

Vol 64 (1) ◽

pp. 203-210

Author(s):

Isao KURASHIGE ◽

Takahiro NISHIDA ◽

Michihiko HIRONAGA

Keyword(s):

Fly Ash ◽

Portland Cement ◽

Strength Development ◽

Carbonation Resistance ◽

Nondestructive Evaluations

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

Materials and Structures ◽

10.1617/s11527-021-01644-7 ◽

2021 ◽

Vol 54 (2) ◽

Author(s):

Marlene Sakoparnig ◽

Isabel Galan ◽

Florian R. Steindl ◽

Wolfgang Kusterle ◽

Joachim Juhart ◽

...

Keyword(s):

Binding Capacity ◽

Cementitious Materials ◽

Chloride Penetration ◽

Supplementary Cementitious Materials ◽

Conventional Concrete ◽

Sprayed Concrete ◽

Carbonation Resistance ◽

Negative Environmental Impact ◽

The Impact ◽

Positive Effect

AbstractThe 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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Relation between carbonation resistance, mix design and exposure of mortar and concrete

Cement and Concrete Composites ◽

10.1016/j.cemconcomp.2015.04.020 ◽

2015 ◽

Vol 62 ◽

pp. 33-43 ◽

Cited By ~ 68

Author(s):

Andreas Leemann ◽

Peter Nygaard ◽

Josef Kaufmann ◽

Roman Loser

Keyword(s):

Mix Design ◽

Carbonation Resistance

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Experimental Study on Durability Improvement of Fly Ash Concrete with Durability Improving Admixture

The Scientific World JOURNAL ◽

10.1155/2014/818103 ◽

2014 ◽

Vol 2014 ◽

pp. 1-11 ◽

Cited By ~ 4

Author(s):

Hong-zhu Quan ◽

Hideo Kasami

Keyword(s):

Fly Ash ◽

Experimental Studies ◽

Drying Shrinkage ◽

Replacement Ratio ◽

Fly Ash Concrete ◽

Air Content ◽

Carbonation Resistance ◽

Binder Ratio ◽

Water Binder Ratio

In order to improve the durability of fly ash concrete, a series of experimental studies are carried out, where durability improving admixture is used to reduce drying shrinkage and improve freezing-thawing resistance. The effects of durability improving admixture, air content, water-binder ratio, and fly ash replacement ratio on the performance of fly ash concrete are discussed in this paper. The results show that by using durability improving admixture in nonair-entraining fly ash concrete, the compressive strength of fly ash concrete can be improved by 10%–20%, and the drying shrinkage is reduced by 60%. Carbonation resistance of concrete is roughly proportional to water-cement ratio regardless of water-binder ratio and fly ash replacement ratio. For the specimens cured in air for 2 weeks, the freezing-thawing resistance is improved. In addition, by making use of durability improving admixture, it is easier to control the air content and make fly ash concrete into nonair-entraining one. The quality of fly ash concrete is thereby optimized.

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