Influence of Temperature on the Moisture Transport in Concrete

Zhang, Qingzhang; Kang, Zihan; Ling, Yifeng; Chen, Hui; Li, Kangzong

doi:10.3390/cryst11010008

Cited by 4 publications

(5 citation statements)

References 27 publications

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“…26 If taking into account that the heat flux from the atmosphere or the surface on which the concrete coupon is positioned and Knudsen diffusion, the contribution due to the vapor pressure is much larger than the effect of temperature or relative humidity. 46,50,51 Therefore, temperature and relative humidity at this scale (which is relevant for most scenarios; see introduction) will not dominate the evaporation process of liquid anhydrous ammonia from a porous network such as concrete. This work and the data shown in Figure 4 (diffusion-limited evaporation) and Figure 5 (limited or no effects due to temperature and relative humidity) support this claim.…”

Section: Resultsmentioning

confidence: 99%

“…Additionally, given the short distances that anhydrous ammonia must travel through the coupon, the expected mechanism of evaporation is via diffusion through the capillary to the surface 26 . If taking into account that the heat flux from the atmosphere or the surface on which the concrete coupon is positioned and Knudsen diffusion, the contribution due to the vapor pressure is much larger than the effect of temperature or relative humidity 46,50,51 . Therefore, temperature and relative humidity at this scale (which is relevant for most scenarios; see introduction) will not dominate the evaporation process of liquid anhydrous ammonia from a porous network such as concrete.…”

Section: Resultsmentioning

confidence: 99%

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Evaporation of anhydrous ammonia from small concrete coupons and implications regarding evaporation from a large accidental spill on concrete

Languirand,

Phung,

Hanna

et al. 2023

Process Safety Progress

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Anhydrous ammonia is transported via ship, rail, and road everyday in the United States as a refrigerated liquid at ambient pressure. As a result, unintential release of a large amount of anhydrous ammonia could result from an accident during transportation. The aim of this paper is to provide a better understanding of the evaporation of anhydrous ammonia from porous media. In our investigation, laboratory‐scale concrete coupons were used as a surrogate for a larger concrete pad that could be present in an event involving an unintentional release of liquid anhydrous ammonia. Concrete coupons sized 5 cm × 5 cm × 1.9 cm were saturated in liquid anhydrous ammonia, and measurements of the subsequent evaporation from the coupons were made in an environmental chamber. The ambient air temperature within the chamber varied from 5 to 45°C, and the relative humidity varied from 5% to 75%. Mass‐difference calculation and Berthelot's reaction were used to determine the average evaporation rate from a concrete coupon across all trials, which was found to be 6.5 ± 1.9 mg/s. To validate these evaporation rates, the remaining ammonia in the concrete coupon was measured for each trial. We found that the time‐integrated calculated evaporation rates correlated well with the total mass of ammonia that was lost from the coupons. In addition, it was found that ambient air temperature and relative humidity had little influence on anhydrous ammonia evaporation from the concrete coupons.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Evaporation of anhydrous ammonia from small concrete coupons and implications regarding evaporation from a large accidental spill on concrete

Languirand,

Phung,

Hanna

et al. 2023

Process Safety Progress

View full text Add to dashboard Cite

show abstract

“…The fine aggregate is made of river sand. The measured water content is 4.8% (mass fraction), the fineness modulus is 2.6 (belongs to medium sand), the mud content is less than 1% (mass fraction), and the apparent density is 2.54 g/cm 3 . The mix proportions of cement paste (P-0.3, P-0.4, P-0.5) and mortar (M-0.3, M-0.4, M-0.5) are provided in Table 3.…”

Section: Adsorption and Desorption Experiments On Cement-based Materi...mentioning

confidence: 94%

“…Durability is one of the most prominent problems of cement-based materials. The transport of water in the pore network directly influences the mechanical (shrinkage, creep) and chemical (penetration of aggressive agents) degradation of cement-based materials [1][2][3][4][5]. The adsorptiondesorption curve can reflect the corresponding relationship between the equilibrium water content of porous materials and the relative humidity (RH) of the environment; thus, it is one of the major data used to evaluate durability [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Research on Water Transport during Adsorption and Desorption in Cement-Based Materials

Zhang¹,

Su²,

Wang³

et al. 2023

Computer Modeling in Engineering &Amp; Sciences

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The durability of cement-based materials is related to water transport and storage in their pore network under different humidity conditions. To understand the mechanism and characteristics of water adsorption and desorption processes from the microscopic scale, this study introduces different points of view for the pore space model generation and numerical simulation of water transport by considering the "ink-bottle" effect. On the basis of the pore structure parameters (i.e., pore size distribution and porosity) of cement paste and mortar with water-binder ratios of 0.3, 0.4 and 0.5 obtained via mercury intrusion porosimetry, randomly formed 3D pore space models are generated using two-phase transformation on Gaussian random fields and verified via image analysis method of mathematical morphology. Considering the Kelvin-Laplace equation and the influence of "ink-bottle" pores, two numerical calculation scenarios based on mathematical morphology are proposed and applied to the generated model to simulate the adsorption-desorption process. The simulated adsorption and desorption curves are close to those of the experiment, verifying the effectiveness of the developed model and methods. The obtained results characterize water transport in cement-based materials during the variation of relative humidity and further explain the hysteresis effect due to "ink-bottle" pores from the microscopic scale.

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“…Compared with rectangular and V-shaped cracks, the chloride diffusion process in cracked concrete with a tortuous crack was slower at the early immersion age, while the crack geometry had a marginal influence on the chloride penetration depth in cracked concrete during long-term immersion. Zhang et al [21] built a moisture saturation equilibrium relationship of concrete under different temperatures and relative humidity conditions to develop moisture absorption and desorption curves. They concluded that the moisture absorption rate was lower at higher temperatures and largely dependent on the saturation gradient, while the desorption was increased at higher temperatures and mostly affected by the saturation gradient.…”

mentioning

confidence: 99%