scholarly journals Effect of Dry–Wet Cycle Periods on Properties of Concrete under Sulfate Attack

2021 ◽  
Vol 11 (2) ◽  
pp. 888
Author(s):  
Jin-Jun Guo ◽  
Peng-Qiang Liu ◽  
Cun-Liang Wu ◽  
Kun Wang

Dry–wet cycle conditions have significant effects on the corrosion of concrete under sulfate attack. However, previous studies have only applied them as a method for accelerating sulfate attack and not systematically studied them as an object. In order to explore the impact of sulfate attack with different dry–wet cycle periods on concrete, in this study, four dry–wet cycle periods (3, 7, 14, and 21 days) were selected. The flexure strength, relative dynamic modulus, and mass were tested, and the microstructures of the eroded specimens were also analyzed. The intensity and depth of sulfate erosion were influenced by the wet–dry cycle period. The results show that the deterioration of concrete first increased and then decreased with an extension of the dry–wet cycle period. Microstructural analysis indicated that, with an increase in the dry–wet cycle period, the corrosion depth of sulfate attack increased. Moreover, the erosion products such as ettringite and gypsum were greatly increased, in agreement with the macroscopic variations. However, excessively prolonging the dry–wet periods does not significantly further the deterioration of concrete’s performance. Therefore, considering the strength and depth of corrosion caused by sulfate attack, it would be appropriate to employ dry–wet cycle periods of 7–14 days under natural dry conditions in studies on concrete.

2021 ◽  
Vol 13 (14) ◽  
pp. 2692
Author(s):  
Mauri Pelto ◽  
Prajjwal Panday ◽  
Tom Matthews ◽  
Jon Maurer ◽  
L. Baker Perry

Recent observations of rising snow lines and reduced snow-covered areas on glaciers during the October 2020–January 2021 period in the Nepal–China region of Mount Everest in Landsat and Sentinel imagery highlight observations that significant ablation has occurred in recent years on many Himalayan glaciers in the post-monsoon and early winter periods. For the first time, we now have weather stations providing real-time data in the Mount Everest region that may sufficiently transect the post-monsoon snow line elevation region. These sensors have been placed by the Rolex National Geographic Perpetual Planet expedition. Combining in situ weather records and remote sensing data provides a unique opportunity to examine the impact of the warm and dry conditions during the 2020 post-monsoon period through to the 2020/2021 winter on glaciers in the Mount Everest region. The ablation season extended through January 2021. Winter (DJF) ERA5 reanalysis temperature reconstructions for Everest Base Camp (5315 m) for the 1950–February 2021 period indicate that six days in the January 10–15 period in 2021 fell in the top 1% of all winter days since 1950, with January 13, January 14, and January 12, being the first, second, and third warmest winter days in the 72-year period. This has also led to the highest freezing levels in winter for the 1950–2021 period, with the January 12–14 period being the only period in winter with a freezing level above 6000 m.


2010 ◽  
Vol 10 (16) ◽  
pp. 7709-7722 ◽  
Author(s):  
G.-J. Roelofs ◽  
H. ten Brink ◽  
A. Kiendler-Scharr ◽  
G. de Leeuw ◽  
A. Mensah ◽  
...  

Abstract. In May 2008, the measurement campaign IMPACT for observation of atmospheric aerosol and cloud properties was conducted in Cabauw, The Netherlands. With a nudged version of the coupled aerosol-climate model ECHAM5-HAM we simulate the size distribution and chemical composition of the aerosol and the associated aerosol optical thickness (AOT) for the campaign period. Synoptic scale meteorology is represented realistically through nudging of the vorticity, the divergence, the temperature and the surface pressure. Simulated concentrations of aerosol sulfate and organics at the surface are generally within a factor of two from observed values. The monthly averaged AOT from the model is 0.33, about 20% larger than observed. For selected periods of the month with relatively dry and moist conditions discrepancies are approximately −30% and +15%, respectively. Discrepancies during the dry period are partly caused by inaccurate representation of boundary layer (BL) dynamics by the model affecting the simulated AOT. The model simulates too strong exchange between the BL and the free troposphere, resulting in weaker concentration gradients at the BL top than observed for aerosol and humidity, while upward mixing from the surface layers into the BL appears to be underestimated. The results indicate that beside aerosol sulfate and organics also aerosol ammonium and nitrate significantly contribute to aerosol water uptake. The simulated day-to-day variability of AOT follows synoptic scale advection of humidity rather than particle concentration. Even for relatively dry conditions AOT appears to be strongly influenced by the diurnal cycle of RH in the lower boundary layer, further enhanced by uptake and release of nitric acid and ammonia by aerosol water.


2017 ◽  
Author(s):  
Bin Zhao ◽  
Kuo-Nan Liou ◽  
Yu Gu ◽  
Jonathan H. Jiang ◽  
Qinbin Li ◽  
...  

Abstract. The interactions between aerosols and ice clouds represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. In particular, the impact of aerosols on ice crystal effective radius (Rei), which is a key parameter determining ice clouds' net radiative effect, is highly uncertain due to limited and conflicting observational evidence. Here we investigate the effects of aerosols on Rei under different meteorological conditions using 9-year satellite observations. We find that the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters. While there is a significant negative correlation between Rei and aerosol loading in moist conditions, consistent with the Twomey effect for liquid clouds, a strong positive correlation between the two occurs in dry conditions. Simulations based on a cloud parcel model suggest that water vapor modulates the relative importance of different ice nucleation modes, leading to the opposite aerosol impacts between moist and dry conditions. When ice clouds are decomposed into those generated from deep convection and formed in-situ, the water vapor modulation remains in effect for both ice cloud types, although the sensitivities of Rei to aerosols differ noticeably between them due to distinct formation mechanisms. The water vapor modulation can largely explain the difference in the responses of Rei to aerosol loadings in various seasons. A proper representation of the water vapor modulation is essential for an accurate estimate of aerosol-cloud radiative forcing produced by ice clouds.


2021 ◽  
Author(s):  
hamid Kardan moghaddam ◽  
Zahra Rahimzadeh kivi ◽  
Fatemeh Javadi ◽  
Mohammad Heydari

Abstract This study evaluates and predicts the ground subsidence that happens due to the haphazard operation of groundwater resources. Also, several strategies have been developed to control this unpleasant phenomenon. For this purpose, groundwater flow simulation has been conducted using MODFLOW numerical model, and subsidence simulation in Najafabad plain has been done using SUB package under three climatic scenarios for future periods. Examination of the simulation results shows that the amount of land subsidence will increase with the aquifer operation's continuation. The maximum amount of subsidence for 6 years in drought conditions will be 23 cm at the aquifer's outlet. According to the land subsidence results at the aquifer, risk zoning of the aquifer operation was done to develop a solution to reduce the withdrawal of groundwater resources to control subsidence. Therefore, risk zoning was performed using land use and the extent of operation of groundwater resources. The results showed that the north-eastern part of the aquifer has the maximum risk of subsidence. According to the obtained results from subsidence risk zoning, scenarios of reduced water withdrawal from the aquifer in its outlet were developed. The treatment strategies results showed that the maximum amount of subsidence in wet, normal and dry conditions will be 10, 14 and 18 cm, respectively. These results indicate a 14% improvement in the quantitative condition of the aquifer in wet conditions, 10% in normal conditions and 7% in dry conditions in the total aquifer of Najafabad. Improvement of conditions by simulation shows the impact of the importance of optimal utilization of groundwater resources.


2009 ◽  
Vol 60 (8) ◽  
pp. 730 ◽  
Author(s):  
P. R. Ward ◽  
K. Whisson ◽  
S. F. Micin ◽  
D. Zeelenberg ◽  
S. P. Milroy

In Mediterranean-type climates, dryland soil water storage and evaporation during the hot and dry summer are poorly understood, particularly for sandy-textured soils. Continued evaporation during summer, and any effects of crop stubble management, could have a significant impact on annual components of the water balance and crop yield. In this research, the effect of wheat stubble management on summer evaporation and soil water storage was investigated for a sandy soil in south-western Australia, during the summers of 2005–06 and 2006–07. Treatments comprised: retained standing stubble; retained flattened stubble; removed stubble; and removed stubble followed by burying the crowns with topsoil from an adjacent area. Under ‘dry’ conditions, evaporation continued at ~0.2 mm/day. In contrast to previous results for finer textured soil types, stubble retention did not decrease the rate of evaporation, but marginally (10–30%) increased evaporation on 7 out of 14 days when measurements were taken. Significant differences due to stubble management were observed in two successive summers, but only for relatively dry soil conditions. There were no significant differences observed for several days after irrigation or rainfall. Under dry conditions in the absence of rainfall, total decrease in water storage during a 90-day summer period could be ~20 mm, but differences attributable to stubble management are likely to be a few mm.


2016 ◽  
Vol 16 (3) ◽  
pp. 1747-1760 ◽  
Author(s):  
L. Brégonzio-Rozier ◽  
C. Giorio ◽  
F. Siekmann ◽  
E. Pangui ◽  
S. B. Morales ◽  
...  

Abstract. The impact of cloud events on isoprene secondary organic aerosol (SOA) formation has been studied from an isoprene ∕ NOx ∕ light system in an atmospheric simulation chamber. It was shown that the presence of a liquid water cloud leads to a faster and higher SOA formation than under dry conditions. When a cloud is generated early in the photooxidation reaction, before any SOA formation has occurred, a fast SOA formation is observed with mass yields ranging from 0.002 to 0.004. These yields are 2 and 4 times higher than those observed under dry conditions. When the cloud is generated at a later photooxidation stage, after isoprene SOA is stabilized at its maximum mass concentration, a rapid increase (by a factor of 2 or higher) of the SOA mass concentration is observed. The SOA chemical composition is influenced by cloud generation: the additional SOA formed during cloud events is composed of both organics and nitrate containing species. This SOA formation can be linked to the dissolution of water soluble volatile organic compounds (VOCs) in the aqueous phase and to further aqueous phase reactions. Cloud-induced SOA formation is experimentally demonstrated in this study, thus highlighting the importance of aqueous multiphase systems in atmospheric SOA formation estimations.


2014 ◽  
Vol 14 (4) ◽  
pp. 2139-2153 ◽  
Author(s):  
S. Crumeyrolle ◽  
G. Chen ◽  
L. Ziemba ◽  
A. Beyersdorf ◽  
L. Thornhill ◽  
...  

Abstract. During the NASA DISCOVER-AQ campaign over the US Baltimore, MD–Washington, D.C., metropolitan area in July 2011, the NASA P-3B aircraft performed extensive profiling of aerosol optical, chemical, and microphysical properties. These in situ profiles were coincident with ground-based remote sensing (AERONET) and in situ (PM2.5) measurements. Here, we use this data set to study the correlation between the PM2.5 observations at the surface and the column integrated measurements. Aerosol optical depth (AOD550 nm) calculated with the extinction (550 nm) measured during the in situ profiles was found to be strongly correlated with the volume of aerosols present in the boundary layer (BL). Despite the strong correlation, some variability remains, and we find that the presence of aerosol layers above the BL (in the buffer layer – BuL) introduces significant uncertainties in PM2.5 estimates based on column-integrated measurements (overestimation of PM2.5 by a factor of 5). This suggests that the use of active remote sensing techniques would dramatically improve air quality retrievals. Indeed, the relationship between the AOD550 nm and the PM2.5 is strongly improved by accounting for the aerosol present in and above the BL (i.e., integrating the aerosol loading from the surface to the top of the BuL). Since more than 15% of the AOD values observed during DISCOVER-AQ are dominated by aerosol water uptake, the f(RH)amb (ratio of scattering coefficient at ambient relative humidity (RH) to scattering coefficient at low RH; see Sect. 3.2) is used to study the impact of the aerosol hygroscopicity on the PM2.5 retrievals. The results indicate that PM2.5 can be predicted within a factor up to 2 even when the vertical variability of the f(RH)amb is assumed to be negligible. Moreover, f(RH = 80%) and RH measurements performed at the ground may be used to estimate the f(RH)amb during dry conditions (RHBL < 55%).


2020 ◽  
Author(s):  
José Manuel Vaquero ◽  
María Cruz Gallego ◽  
Víctor M. S. Carrasco ◽  
Nieves Bravo-Paredes ◽  
María Ángeles Obregón ◽  
...  

&lt;p&gt;Our efforts to a better understanding of the historical climate of the region of Extremadura (interior of the SW Iberia) have been directed in two main aspects. First, we have tried to recover all the meteorological data of the pre-instrumental period. Second, we have been working on the localization and analysis of proxy data, including &amp;#8220;pro-pluvia&amp;#8221; rogation ceremonies and a chronology of catastrophic floods in this region.&lt;/p&gt;&lt;p&gt;The recovery of historical meteorological data from libraries and archives and the subsequent digitization to obtain readable-machine version has been a main task in our research. Meteorological data from different sources (manuscripts, books, newspapers, etc.) and eight different locations in Extremadura have been recovered and digitized. The oldest data were read in 1824 (Fern&amp;#225;ndez-Fern&amp;#225;ndez et al., 2014). Other important meteorological series can be highlighted as the actinometric measurements in C&amp;#225;ceres for the period 1913-1920 (Bravo-Paredes et al., 2019).&lt;/p&gt;&lt;p&gt;&amp;#8220;Pro-pluvia&amp;#8221; rogations were celebrated during dry conditions to ask God for rain. In our case, 35 &amp;#8220;pro-pluvia&amp;#8221; rogations were retrieved for the period 1824-1931 from different locations in Extremadura. The winter climate of this region is strongly dominated by the North Atlantic Oscillation (NAO) and, therefore, these pro-pluvia rogations were associated to the NAO index to analyze this relationship. The results of our analysis show that the rogation ceremonies in Extremadura can be considered a good proxy for the NAO index. Also, it is important to know the magnitude and the impact of the catastrophic floods occurred in Extremadura. In total, 40 floods occurred in Badajoz were recovered from different documentary sources for the period 1545-1989.&lt;/p&gt;&lt;p&gt;All these research efforts will allow for a better understanding of the past climate in the region of Extremadura, where such studies have been very scarce.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Bravo-Paredes, N. et al. (2019) &amp;#8220;Analysis of actinometric measurements under different sky conditions in C&amp;#225;ceres (Spain) for the period 1913-1920&amp;#8221; Tellus B 71, 1663597. DOI: 10.1080/16000889.2019.1663597&lt;/p&gt;&lt;p&gt;Fern&amp;#225;ndez-Fern&amp;#225;ndez, M.I. et al. (2014) &quot;The climate of Zafra from 1750 to 1840: History and description of weather observations&quot; Climatic Change 126, 107&amp;#8211;118. (doi: 10.1007/s10584-014-1201-5)&lt;/p&gt;


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2671-2671
Author(s):  
Filippo Russo ◽  
Gino Svanera ◽  
Paola Della Cioppa ◽  
Gaetano Corazzelli ◽  
Ferdinando Frigeri ◽  
...  

Abstract To improve ABVD results we first developed a protocol which adds G-CSF to the standard ABVD treatment. From March 1997 to May 2004 69 patients with HL were treated with ABVD+G-CSF and 22 with a standard ABVD. Recently we designed a new dose-dense and dose-intensity ABVD scheme (escABVD-21) for advanced HL; in this new schedule the adriamycin was escalated from 25 to 35 mg/m2 (cycles 1,2,3,4) and the inter-cycle period was shortened from 28 to 21 days (for all 6 cycles); primary G-CSF was administered from d3 to d8 and drugs were delivered at d10 and d21 of every cycle. From June 2004, 19 patients were treated with this protocol. Relative dose-intensity (RDI) was calculated for any of these 110 newly diagnosed HL patients treated with ABVD. The results were also compared with a historical group of 70 patients who had undergone hybrid MOPP/ABVD. HL patients received from 4 to 8 cycles of CT +/− IF-RT. Patients were divided in 4 groups according to the RDI. The first group included 20 (11%) pts with RDI less than 0.80; the 2nd group, 64 (36%) pts with RDI values between 0.80 and 0.95, the 3rd group, 74 (42%) pts with RDI values between 0.96 and 1.10 and, finally, the 4th group included pts with RDI values of more than 1.10. In Tab 2 we report the CR, EFS and OS rates according to the 4 levels of RDI. Figures 1 shows EFS curve according to Kaplan-Meyer. Response and survival rates of groups 1,2,3 and 4 were: 50%vs91%vs97% vs 100%, for CR (p<0.0001); 20%vs78%vs92%vs100% for EFS (p< 0.0001); and 25%vs91%vs99%vs100% for OS (p< 0.0001). The best progression rates of CR, EFS and OS were seen in patients with RDI >1.10. In particular, the new dose-dense and dose-intensity escABVD-21 protocol seems very promising in terms of complete response and toxicity profile: 19/19 pts (100%) obtained an early CR; (PET negative at the end of the 2nd cycle), and, as on 8th August 2005, all these19 patients were disease-free. The dose-escalation of adriamycin and the dose-density of the schedule were well-tolerated; toxicity was mild. These results show that subptimal RDI may compromise outcomes proportionally to the level of RDI reduction. On the contrary, Primary G-CSF permits to deliver dose-dense and dose intense schedules such as escABVD-21 maintaining the same profile of toxicity of standard ABVD, higher RDI levels, and consequently, a significant impact on complete response and survival rates. tab1 Presentation features n. of pts male sex age>45 yrs advanced stage E sites>1 bulky B symptoms IPI score ≥ 3 180 92 43 148 23 80 83 56 % 51% 24% 82% 13% 44% 46% 31% tab.2 Response and Survival according to 4 RDI levels RDI level (range 0.5–1.5) N. of pts. (%) CR rate Fisher’s Exact test (2-sided) EFS rate log-rank statistic 0S rate log-rank statistic overall 180(100%) 90% 80% 88% <0.80 20 (11%) 50% 20% 25% 0.80–0.95 64 (36%) 91% 28.391 78% 74.99 91% 96.76 0.96–1.10 76 (42%) 97% 92% 99% >1.10 20 (11%) 100% 100% 100% significance <0.0001 <0.0001 <0.0001 Figure Figure


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