![]() ![]() Moreover, construction deficiency such as cavity may widely exist during the preparation of shotcrete materials, thus largely reducing the reliability of tests. This is mainly due to that in situ preparation of shotcrete materials is difficult and uncontrollable. However, dedicated durability studies on the sulfate resistance of shotcrete materials mixed with fly ash (FA)/silica fume (SF) were rare. As for chloride-induced damage, it is generally believed that may combine with the C 3A phase to generate Friedel’s salt. Among them, sulfate expansive products such as ettringite (E), gypsum (G), and thaumasite (T) and crystallization of sulfate salt (mainly sodium sulfate) are regarded as two main hypotheses. ![]() ![]() The individual damage mechanisms caused by these ions on cement-based materials were well-documented in the last few decades. Shotcrete materials usually directly contact with groundwater or rock mass. The corresponding performance-based testing was also rarely reported. Unfortunately, there is dearth of information on sulfate resistance of shotcrete materials in the presence of chloride ions. Since permanent shotcrete linings are increasingly adopted in road slope and underground tunneling engineering, durability of shotcrete under these aggressive environments is becoming crucial at the design and construction stage. These adverse impacts may cause deterioration or even disintegration of shotcrete materials during service period. Meanwhile, chloride ions were also detected to degrade cement pastes. Scrivener 3.1.2 serial free#Free chloride ions mainly corrode the reinforcement steel, and sulfate salt attacks the concrete pastes inch by inch. These ions have adverse impact on the durability of porous shotcrete materials, such as a collapse of mechanical strength. This groundwater is deleterious to shotcrete materials since it was contaminated by certain pernicious species, e.g., and or the combination of two. However, they have the risk to be eroded by contaminated groundwater under harsh ambient environments, such as shotcrete liners of a tunnel underneath a refuse landfill. Among them, shotcrete durability is generally overlooked due to the reliable performance benefited from its technology of high speed jet, high early-age strength and the addition of the accelerator, which differs from conventional concrete materials. IntroductionÄurability of cement-based materials, no matter emerging or conventional ones, has become a major issue in structural engineering over the last few decades. Mercury intrusion porosimetry (MIP) analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests reveal that these consequences were strongly related to the refinement of microstructure resulted from pozzolanic reactions and hydration kinetics. Silica fume (SF) admixture can compensate the undesired reduction of early-age strength caused by FA addition, but make these specimens more susceptible to sulfate attack. Adding fly ash (FA) in shotcrete mixtures enhanced the long-term performance but invited massive white efflorescence on surface layer under partial-immersion exposure condition. Meanwhile, the lower w/b ratio proved to be efficient in increasing the resistance to both sulfate attacks. The presence of chloride ions can globally mitigate these deteriorations. Results show that loss of strength was the typical feature of chemical sulfate attack on shotcrete, while surface spalling dominated in deterioration caused by physical sulfate attack. Scrivener 3.1.2 serial full#Two different laboratorial immersion regimes (continuously full immersion and partial immersion with cycling temperature and relative humidity) were carried out to induce chemical/physical sulfate attack. Three water-to-binder ratios (w/b), i.e., 0.35, 0.45, and 0.55, and two types of supplementary cementitious materials (SCMs), namely, fly ash (FA) and silica fume (SF), were considered in the current study. Durability of in situ shotcrete under external sulfate attack was investigated, taking into consideration the addition of mineral admixtures, along with the presence of chloride ions. ![]()
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