On the Effects of Relative Humidity and CO2 Concentration on Carbonation of Cement Pastes

The influence of temperature, CO2 concentration and relative humidity on the carbonation depth and compressive strength of concrete was investigated. Meanwhile, phase composition, types of hydration products and microstructure characteristics of samples before and after the carbonation were analyzed by XRD and ESEM. Research results demonstrate that temperature, CO2 concentration and relative humidity influence the carbonation depth and compressive strength of concrete significantly. There is a linear relationship between temperature and carbonation depth, as well as the compressive strength of concrete. CO2 concentration and relative humidity present a power function and a polynomial function with carbonation depth of concrete, respectively. The concrete carbonation depth increases with the increase of relative humidity and reaches the maximum value when the relative humidity is 70%. Significant differences of phase composition, hydration products and microstructure are observed before and after the carbonation. Carbonization products of samples are different with changes of temperatures (10 °C, 20 °C and 30 °C). The result of crystal structure analysis indicates that the carbonation products are mainly polyhedral spherical vaterite and aragonite.

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Occupancy determination based on time series of CO2 concentration, temperature and relative humidity

Energy and Buildings ◽

10.1016/j.enbuild.2017.04.080 ◽

2017 ◽

Vol 147 ◽

pp. 142-154 ◽

Cited By ~ 15

Author(s):

Andrzej Szczurek ◽

Monika Maciejewska ◽

Tomasz Pietrucha

Keyword(s):

Time Series ◽

Relative Humidity ◽

Co2 Concentration

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Slag Blended Cement Paste Carbonation under Different CO2 Concentrations: Controls on Mineralogy and Morphology of Products

Materials ◽

10.3390/ma13153404 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3404

Author(s):

Wei Liu ◽

Shifa Lin ◽

Yongqiang Li ◽

Wujian Long ◽

Zhijun Dong ◽

...

Keyword(s):

Blended Cement ◽

Co2 Concentration ◽

Magic Angle Spinning ◽

Magic Angle ◽

Accelerated Carbonation ◽

X Ray Diffraction ◽

Cement Pastes ◽

Co2 Concentrations ◽

Angle Spinning ◽

Natural Carbonation

To investigate the effect of different CO2 concentrations on the carbonation results of slag blended cement pastes, carbonation experiments under natural (0.03% CO2) and accelerated conditions (3, 20, and 100% CO2) were investigated with various microscopic testing methods, including X-ray diffraction (XRD), 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR) and scanning electron microscopy (SEM). The XRD results indicated that the major polymorphs of CaCO3 after carbonation were calcite and vaterite. The values of the calcite/(aragonite + vaterite) (c/(a + v)) ratios were almost the same in all carbonation conditions. Additionally, NMR results showed that the decalcification degree of C-S-H gel exposed to 0.03% CO2 was less than that exposed to accelerated carbonation; under accelerated conditions, it increased from 83.1 to 84.2% when the CO2 concentration improved from 3% to 100%. In SEM observations, the microstructures after accelerated carbonation were denser than those under natural carbonation but showed minor differences between different CO2 concentrations. In conclusion, for cement pastes blended with 20% slag, a higher CO2 concentration (above 3%) led to products different from those produced under natural carbonation. A further increase in CO2 concentration showed limited variation in generated carbonation products.

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18O enrichment of leaf cellulose correlated with 18O enrichment of leaf sucrose but not bulk leaf water in a C3 grass across contrasts of atmospheric CO2 concentration and air humidity

10.21203/rs.3.rs-596094/v1 ◽

2021 ◽

Author(s):

Juan C. Baca Cabrera ◽

Regina T. Hirl ◽

Rudi Schäufele ◽

Jianjun Zhu ◽

Haitao Liu ◽

...

Keyword(s):

Relative Humidity ◽

Spatial Heterogeneity ◽

Lolium Perenne ◽

Co2 Concentration ◽

Leaf Water ◽

Atmospheric Co2 ◽

Cellulose Synthesis ◽

Source Water ◽

Sucrose Synthesis ◽

Air Humidity

Abstract · The 18O composition of plant cellulose is often used to reconstruct past climate and plant function. However, uncertainty remains regarding the estimation of the leaf sucrose 18O signal and its subsequent attenuation by 18O exchange with source water during cellulose synthesis.· We grew Lolium perenne at three CO2 concentrations (200, 400 or 800 mmol mol-1) and two relative humidity (RH) levels (50% or 75%), and determined 18O enrichment of leaf sucrose (Δ18OSucrose), bulk leaf water (Δ18OLW), leaf cellulose (Δ18OCellulose) and water at the site of cellulose synthesis (Δ18OCelSynW). · Δ18OCellulose correlated with Δ18OSucrose (R2=0.87) but not with Δ18OLW (R2=0.04), due to a variable 18O discrepancy (range 2.0-9.0‰) between sucrose synthesis water (Δ18OSucSynW, estimated from Δ18OSucrose) and bulk leaf water. The discrepancy resulted mainly from an RH effect. The proportion of oxygen in cellulose that exchanged with medium water during cellulose formation (pex), was near-constant when referenced to Δ18OSucSynW (pex-SucSynW = 0.52±0.02 SE), but varied when related to bulk leaf water (pex-LW = –0.01 to 0.46). · We conclude that previously reported RH-dependent variations of pex-LW in grasses are related to a discrepancy between Δ18OSucSynW and Δ18OLW that may result from spatial heterogeneity in 18O gradients of leaf water and photosynthetic sucrose synthesis.

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Study and Application on Big Data Information Fusion System Based on IoT

Security and Communication Networks ◽

10.1155/2021/5486162 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Lina Zheng

Keyword(s):

Big Data ◽

Relative Humidity ◽

Light Intensity ◽

Prediction Model ◽

Information Fusion ◽

Co2 Concentration ◽

Training Data ◽

Fusion Technology ◽

Climate Data ◽

Zigbee Technology

In our study, we first illustrated information fusion technology and Internet of Things (IoT), and then we built farmland IoT information collection platform on the basis of ZigBee technology and agricultural sensors to collect climate data including air pressure, temperature, soil water content, light intensity, and relative humidity. Finally, prediction model was used to evaluate crop growth condition. Results show that temperature increases with time and reaches the maximum at 13:00 PM. But relative humidity decreases with time and reaches the maximum at 3:30 AM. Light intensity presents a straight trend with time and reaches the maximum at 13:30 PM. CO2 concentration presents a fluctuation trend with time and reaches high point at 7:00 AM. Prediction model presented a high accuracy outcome with 99% accuracy in training data and 100% in testing set. Therefore, we can conclude that big data fusion technology on the basis of IoT has a good future in many fields excepting agriculture crop, which is also an irreversible trend.

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Monitoring and Assessment of Indoor Environmental Conditions after the Implementation of COVID-19-Based Ventilation Strategies in an Educational Building in Southern Spain

Sensors ◽

10.3390/s21217223 ◽

2021 ◽

Vol 21 (21) ◽

pp. 7223

Author(s):

Antonio J. Aguilar ◽

María L. de la Hoz-Torres ◽

Mª Dolores Martínez-Aires ◽

Diego P. Ruiz

Keyword(s):

Relative Humidity ◽

Natural Ventilation ◽

Co2 Concentration ◽

Quality Level ◽

Indoor Environmental Quality ◽

Effective Measure ◽

Acoustic Environment ◽

Health Authorities ◽

Ventilation Strategies ◽

Ventilation Rates

Since students and teachers spend much of their time in educational buildings, it is critical to provide good levels of indoor environmental quality (IEQ). The current COVID-19 pandemic has shown that maintaining a good indoor air quality level is an effective measure to control the transmission of the SARS-CoV-2 virus. This study used sensors to monitor key IEQ factors and assess several natural ventilation scenarios in a classroom of the University of Granada. Subsequently, the IEQ factors (temperature, relative humidity, CO2 concentration, acoustic environment, and air velocity) were evaluated for the selected ventilation scenarios in the occupied classroom, and the field monitoring was carried out in two different assessment periods, winter and summer. The obtained results show that the CO2 concentration levels were well below the recommended limits. However, the maintenance of the recommended thermal and acoustic IEQ factors was significantly affected by the natural ventilation strategies (temperature and relative humidity values were very close to the outside values, and the background sound pressure level was over 35 dBA during the entire assessment). The proper measurements and careful selection of the appropriate ventilation scenarios become of utmost importance to ensure that the ventilation rates required by the health authorities are achieved.

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Users’ Sensations in the Context of Energy Efficiency Maintenance in Public Utility Buildings

Energies ◽

10.3390/en14238159 ◽

2021 ◽

Vol 14 (23) ◽

pp. 8159

Author(s):

Edyta Dudkiewicz ◽

Marta Laska ◽

Natalia Fidorów-Kaprawy

Keyword(s):

Energy Efficiency ◽

Relative Humidity ◽

Thermal Sensation ◽

Co2 Concentration ◽

Public Utility ◽

Temperature Changes ◽

The Public ◽

Air Movement ◽

Indoor Conditions ◽

The Relationship

Research towards understanding the relationship between maintaining thermal comfort and energy efficiency in the public utility buildings was undertaken among 323 1st year students during class hours. Questionnaires surveys and measurements of indoor conditions were performed. The article identified students’ sensations and perceptions concerning indoor conditions. Temperature, relative humidity, air velocity and CO2 concentration measured to assess room conditions showed that the auditorium had almost comfortable conditions according to the literature guidelines. The indices used to assess students’ perceptions were: Thermal Sensation Vote (TSV), Thermal Preference Vote (TPV), Air Freshness Sensation Vote (AfSV), Air Movement Preference Vote (AmPV), and Relative Humidity Preference Vote (RHPV). The interpretation of these indicators showed that while the students’ requests for temperature changes and increased air movement are adequate for the air conditions in the room, the evaluation of stuffiness and requests for changes in humidity levels are surprising. Striving uncritically to meet the desired room parameters, according to the users votes, can lead to deterioration of the air and not only the increase in energy consumption but even waste it. Better understanding of users’ preferences and behaviour and further application of this knowledge indirectly aim at increasing energy efficiency in buildings.

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Prediction Model of Internal Relative Humidity During Self-desiccation in Hardened Cement Pastes

Concrete Research and Technology ◽

10.3151/crt.26.11 ◽

2015 ◽

Vol 26 (0) ◽

pp. 11-19 ◽

Cited By ~ 1

Author(s):

Hideyuki Utsumi ◽

Takehiro Misaka ◽

Wataru Moteki

Keyword(s):

Relative Humidity ◽

Prediction Model ◽

Hardened Cement ◽

Cement Pastes ◽

Internal Relative Humidity ◽

Hardened Cement Pastes

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The triple oxygen isotope composition of phytoliths, a new proxy of atmospheric relative humidity: controls of soil water isotope composition, temperature, CO<sub>2</sub> concentration and relative humidity

10.5194/cp-2021-34 ◽

2021 ◽

Author(s):

Clément Outrequin ◽

Anne Alexandre ◽

Christine Vallet-Coulomb ◽

Clément Piel ◽

Sébastien Devidal ◽

...

Keyword(s):

Relative Humidity ◽

Oxygen Isotope ◽

Soil Water ◽

Isotope Composition ◽

Co2 Concentration ◽

Oxygen Isotope Composition ◽

Growth Chamber ◽

Starting Point ◽

Atmospheric Relative Humidity ◽

Water Isotope

Abstract. Continental atmospheric relative humidity is a major climate parameter whose variability is poorly understood by global climate models. Models’improvement relies on model-data comparisons for past periods. However, there are no truly quantitative indicators of relative humidity for the pre-instrumental period. Previous studies highlighted a quantitative relationship between the triple oxygen isotope composition of phytoliths, and particularly the 17O-excess of phytoliths, and atmospheric relative humidity. Here, as part of a series of calibrations, we examine the respective controls of soil water isotope composition, temperature, CO2 concentration and relative humidity on phytolith 17O-excess. For that purpose, the grass species Festuca arundinacea was grown in growth chambers where these parameters were varying. The setup was designed to control the evolution of the triple oxygen isotope composition of phytoliths and all the water compartments of the soil-plant-atmosphere continuum. Different analytical techniques (cavity ring-down spectroscopy and isotope ratio mass spectrometry) were used to analyse water and silica. An inter-laboratory comparison allowed to strengthen the isotope data matching. Water and phytolith isotope compositions were compared to previous datasets obtained from growth chamber and natural tropical sites. The results show that the δ'18O value of the source water governs the starting point from which the triple oxygen isotope composition of leaf water, phytolith-forming water and phytoliths evolve. However, since the 17O-excess varies little in the growth chamber and natural source waters, this has no impact on the strong relative humidity-dependency of the 17O-excess of phytoliths, demonstrated for the 40–80 % relative humidity range. This relative humidity-dependency is not impacted by changes in air temperature or CO2 concentration either. A relative humidity proxy equation is proposed. Each per meg of change in phytolith 17O-excess reflects a change in atmospheric relative humidity of ca. 0.2 %. The ±15 per meg reproducibility on the measurement of phytolith 17O-excess corresponds to a ± 3.6 % precision on the reconstructed relative humidity. The low sensitivity of phytolith 17O-excess to climate parameters other than relative humidity makes it particularly suitable for quantitative reconstructions of continental relative humidity changes in the past.

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Influence of Environmental Factors Light, CO2, Temperature, and Relative Humidity on Stomatal Opening and Development: A Review

Agronomy ◽

10.3390/agronomy10121975 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1975

Author(s):

Elisa Driesen ◽

Wim Van den Ende ◽

Maurice De Proft ◽

Wouter Saeys

Keyword(s):

Climate Change ◽

Relative Humidity ◽

Environmental Factors ◽

Global Climate ◽

Co2 Concentration ◽

Stomatal Development ◽

Short And Long Term ◽

Use Efficiency ◽

Underlying Mechanisms ◽

The Impact

Stomata, the microscopic pores surrounded by a pair of guard cells on the surfaces of leaves and stems, play an essential role in regulating the gas exchange between a plant and the surrounding atmosphere. Stomatal development and opening are significantly influenced by environmental conditions, both in the short and long term. The rapid rate of current climate change has been affecting stomatal responses, as a new balance between photosynthesis and water-use efficiency has to be found. Understanding the mechanisms involved in stomatal regulation and adjustment provides us with new insights into the ability of stomata to process information and evolve over time. In this review, we summarize the recent advances in research on the underlying mechanisms of the interaction between environmental factors and stomatal development and opening. Specific emphasis is placed on the environmental factors including light, CO2 concentration, ambient temperature, and relative humidity, as these factors play a significant role in understanding the impact of global climate change on plant development.

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