Distribution Of CO2 Concentration Research Articles

Seasonal and interannual variability of CO2 above the moist tropical forest of southern Vietnam

The paper presents the results of a study of seasonal and interannual variability of CO2 concentration above the moist tropical forest in southern Vietnam. Experimental data were collected during year-long observation of CO2 directly in the forest from 2012 to 2017. All data were obtained through the use of an air intake tube, placed on a metal tower at a height of 46 m and connected to a Li-Cor 820 gas analyzer (Li-Cor Inc., USA) located in a building at the foot of the tower. The values of the concentration were recorded with a resolution of 1 second; for further analysis, all data was averaged to 0.5 h values. Statistical processing based on the Fourier analysis allowed to evaluate the main characteristics of the annual distribution of CO2 concentration, such as the amplitude and phase, as well as to analyze their variability over the years. The results of the study showed a presence of a well-determined annual course of CO2 concentration above the canopy of the moist tropical forest.

Spatio-Temporal Validation of AIRS CO2 Observations Using GAW, HIPPO and TCCON

Carbon dioxide (CO2) is a significant atmospheric greenhouse gas and its concentrations can be observed by in situ surface stations, aircraft flights and satellite sensors. This paper investigated the ability of the CO2 satellite observations to monitor, analyze and predict the horizontal and vertical distribution of atmospheric CO2 concentration at global scales. CO2 observations retrieved by an Atmospheric Infrared Sounder (AIRS) were inter-compared with the Global Atmosphere Watch Program (GAW) and HIAPER Pole-to-Pole Observations (HIPPOs), with reference to the measurements obtained using high-resolution ground-based Fourier Transform Spectrometers (FTS) in the Total Carbon Column Observing Network (TCCON) from near-surface level to the mid-to-high troposphere. After vertically integrating the AIRS-retrieved values with the column averaging kernels of TCCON measurements, the AIRS observations are spatio-temporally compared with HIPPO-integrated profiles in the mid-to-high troposphere. Five selected GAW stations are used for comparisons with TCCON sites near the surface of the Earth. The results of AIRS, TCCON (5–6 km), GAW and TCCON (1 km) CO2 measurements from 2007 to 2013 are compared, analyzed and discussed at their respective altitudes. The outcomes indicate that the difference of about 3.0 ppmv between AIRS and GAW or other highly accurate in situ surface measurements is mainly due to the different vertical altitudes, rather than the errors in the AIRS. The study reported here also explores the potential of AIRS satellite observations for analyzing the spatial distribution and seasonal variation of CO2 concentration at global scales.

CFD analysis for evaluating and optimizing spatial distribution of CO2 concentration in a strawberry greenhouse under different CO2 enrichment methods

A deeper understanding of the spatial distribution of CO2 concentration inside cultivation facilities (e.g., greenhouses and plant factories) is necessary for the quantitative evaluation and/or the improvement in the performance and efficiency of artificial CO2 enrichment methods. We developed 3D computational fluid dynamics (CFD) models for two CO2 enrichment methods in a strawberry greenhouse – one was for overall greenhouse enrichment, as the usual method, and the other was for localized crop enrichment. We confirmed the model validation by comparing the simulated and measured CO2 concentrations in the greenhouse. With regard to the entire enrichment condition, CO2 accumulated at the upper part of the greenhouse through convection due to the high temperature of CO2 generated while there was low CO2 concentration around the crops. This could be regarded as an ineffectual situation. However, such situation can be alleviated by lowering the temperature of CO2. On the other hand, we found that crop-local enrichment can increase CO2 concentration only around crops albeit with less effect on those at the upper part. Thus, changing the enrichment strategy as well as the equipment could greatly optimize the distribution of CO2 in a greenhouse, thereby improving the efficiency of CO2 enrichment.

Spatiotemporal observations of CH4 and CO2 over Iraq using Atmospheric Infrared Sounder (AIRS) data

Methane (CH4) and carbon dioxide (CO2) are the most important greenhouse gases and most important climate forcing agents due to their significant impact on climate, and their concentrations have been increased since the pre-industrial time by 150 and 40 % respectively, basically from fossil fuel combustion and land-use change emissions. In this research, the atmospheric concentration of CH4 and CO2 over Iraq is measured by the Atmospheric Infrared Sounder (AIRS). Time series and time-averaged maps were generated to study and analyse the distribution of CH4 and CO2 concentrations. The results show a significant increase of these two gases with an average increase (3.5 and 5.11 ppbv/ year ) in a rate of (2.69 % and 4 %) for CH4 at SPL 925 hPa and 400 hPa, respectively ; the average increase of CO2 is (1.85 ppm/ year) represent (3.31%) for the whole period. The considerable increase of CH4 and CO2 concentration can affect human healthiness and earth radiative balance. Also, the Satellite observation of AIRS can efficiently show the spatiotemporal variations of CH4 and CO2 for the study area.

Fast prediction for multi-parameters (concentration, temperature and humidity) of indoor environment towards the online control of HVAC system

Heating, ventilation and air conditioning (HVAC) systems are the most energy-consuming building implements for the improvement of indoor environmental quality (IEQ). We have developed the optimal control strategies for HVAC system to respectively achieve the optimal selections of ventilation rate and supplied air temperature with consideration of energy conservation, through the fast prediction methods by using low-dimensional linear ventilation model (LLVM) based artificial neural network (ANN) and low-dimensional linear temperature model (LLTM) based contribution ratio of indoor climate (CRI(T)). To be continued for integrated control of multi-parameters, we further developed the fast prediction model for indoor humidity by using low-dimensional linear humidity model (LLHM) and contribution ratio of indoor humidity (CRI(H)), and thermal sensation index (TS) for assessment. CFD was used to construct the prediction database for CO2, temperature and humidity. Low-dimensional linear models (LLM), including LLVM, LLTM and LLHM, were adopted to expand database for the sake of data storage reduction. Then, coupling with ANN, CRI(T) and CRI(H), the distributions of indoor CO2 concentration, temperature, and humidity were rapidly predicted on the basis of LLVM-based ANN, LLTM-based CRI(T) and LLHM-based CRI(H), respectively. Finally, according to the self-defined indices (i.e., EV, ET, EH), the optimal balancing between IEQ (indicated by CO2 concentration, PMV and TS) and energy consumption (indicated by ventilation rate, supplied air temperature and humidity) were synthetically evaluated. The total HVAC energy consumption could be reduced by 35% on the strength of current control strategies. This work can further contribute to development of the intelligent online control for HVAC systems.

Spatial Distribution of Rn, CO2, Hg, and H2 Concentrations in Soil Gas Across a Thrust Fault in Xinjiang, China

Spatial distribution characteristics and origin of soil gases were discussed in this study. We also examine the correlation between the spatial variation of soil gases and fault activity, based on the measurements of Rn, Hg, H2, and CO2 concentrations in the eastern segment of the BLT fault zone in the southern Tianshan Mountains, Xinjiang, China. The results show that the Rn and CO2 concentrations on the hanging wall were higher than those near the fault zone and on the footwall of the fault. Moreover, the Hg and H2 concentrations on the footwall were also higher than those near the fault and on the hanging wall of the fault. The main factors affecting the variations in soil gas spatial distribution were gaseous origin structure of the crust, fault activity, fault fracture degree, stratigraphic lithology, and the cover layer. The results of active structural fault mapping show that the BLT fault has been active since the Late Quaternary and the thrust has broken the fault surface. Under the influence of tectonic compressive stress, the tension zone was formed on the hanging wall of the fault and fractures were developed. This result is consistent with the characteristics of soil gas concentrations measured in this study, indicating that the concentrations of Rn, Hg, H2, and CO2 are closely related to the fault activity. These findings can be applied to identify seismic precursors from gas monitoring data of the studied area.

Fire smoke movement and distribution in ventilation shafts

Vertical shafts are common structures in buildings, which accelerate smoke spread in fires due to stack effect. In this study, fire smoke movement and distribution in a ventilation shaft were studied through analysing temperature distributions, velocity distributions, CO2 concentration distributions and pressure distributions. Four exhaust rates were discussed and compared. It was found that the status of gas flow at the bottom of the shaft was firstly disturbed when the exhaust fan was working. Then some eddies appeared. As the number of eddies was increased and eddies got enlarged, gas flow in the entire shaft was influenced from the bottom to the top. A high temperature area and a strong convection area appeared close to the open door which was located at the bottom of the shaft. When the exhaust fan was working, the high temperature area and the strong convection area were both controlled at lower positions. The CO2 concentration and the pressure in the shaft were negatively related to the exhaust rate, while the neutral pressure plane height was positively related to the exhaust rate.

Spatial distribution of greenhouse gases (CO2 and CH4) on expressways in the megacity Shanghai, China.

Carbon dioxide (CO2) and methane (CH4) are the two major greenhouse gases (GHGs) in the atmosphere that contribute to global warming. Vehicle emissions on expressways cannot be neglected in the megacity Shanghai because oil accounts for 41% of the total primary energy consumption, and the expressway network carries 60% of the total traffic volume. The spatial distributions of CO2 and CH4 concentrations were monitored in situ on the expressways and in road tunnels using a mobile vehicle. The average CO2 and CH4 concentrations were 472.88 ± 34.48 ppm and 2033 ± 54 ppb on the expressways and 1308.92 ± 767.48 ppm and 2182 ± 112 ppb in the road tunnels in Shanghai, respectively. The highest CO2 and CH4 concentrations appeared on the Yan'an Elevated Road and the North-South Elevated Road, respectively, while their lowest values both occurred on the Huaxia Elevated Road passing through the suburban area. The hotspots of CO2 and CH4 were not consistent, suggesting that they have different sources. Tunnels had a "push-pull effect" on GHGs, and the traffic-congested Yan'an East Road Tunnel showed a dramatically increasing trend of GHG concentration from the entrance to the exit. This traffic-congested tunnel could accumulate a very high concentration of GHGs as well as other pollutants, which could introduce unhealthy conditions for both drivers and passengers. Significant correlations between CO2 and CH4 mostly appeared on the expressways and in the tunnels in Shanghai, suggesting the influences of vehicle exhaust. ΔCH4/ΔCO2 (the slope of the linear regression between CH4 and CO2) and the CH4/CO2 ratio could be used as indicators of vehicle exhaust sources because it increases from sources (e.g., road tunnels) to the observatories in the urban area.

Tunnel ventilation during construction and diffusion of hazardous gases studied by numerical simulations

Proper ventilation of tunnels has remained a serious issue for many years. However, only empirical methods are currently utilised for estimating ventilation time scales in construction scheduling. In this study, the forced ventilation system used in tunnels under construction was investigated through computational fluid dynamics modelling. The effects of influencing factors, such as the duct position, distance between the ventiduct mouth and the working face, air velocity in the duct, and cross-sectional area of the tunnel, were examined, and the flow field and CO concentration distributions in the tunnel space were determined. The obtained results revealed that the zone near the working face can be divided into a jet zone, backflow zone, and vortex zone. Pollutant discharge was strongly related to the flow field distribution. The CO concentration distributions were calculated from the data sets generated by various models, and a ventilation time estimation function was derived for the entire tunnel construction period. The blasting cycle can be significantly shortened by allowing construction workers to enter the tunnel within the calculated entry periods, and necessary construction procedures can be reasonably implemented. The flow field distribution and time dependence of the CO concentration deduced in this study can be extended and applied to other similar projects.

Large-scale simulation of gasification reaction with mass transfer for metallurgical coke: Model development

Large-scale simulation of gasification for a highly resolved coke model with hundreds of millions of voxels was carried out. Three-dimensional phenomena could be evaluated by the numerical simulation, while our previous study was limited to one-dimensional distribution due to the high computational load. The coke model was developed from micro X-ray CT images of a cylindrical coke sample with a radius of 20 mm, and the screen resolution was 20.6 µm/pixel. In the resolved pores, the mass transfer with CO2 gasification was analyzed, whereas voxels of the coke matrix adjacent to the pore vanished due to the reaction. Coke was found to degrade non-uniformly as the reaction progressed, and the areas with highly concentrated carbon matrix voxels remained unchanged. These characteristic areas were derived from the X-ray CT images. Focusing on the concentration distribution of CO2, it was found that the rate-controlling step changed from pore diffusion to chemical reaction with structural change at 1573 K.

IMPROVEMENT OF INDOOR ENVIRONMENT BASED ON MULTIPLE INTERZONAL AIRFLOW ANALYSIS

In welfare facilities for the elderly, from the viewpoint of hygiene, a lot of attention is paid to ventilation and humidification. However, excessive ventilation in winter promotes the inflow of outdoor air with low temperature and humidity, and brings low humidity, cold draft, and increase in heating load. Furthermore, the airflow route in a facility should be designed to minimize infection or odor diffusion. It is important to grasp the airflow distribution of whole the building quantitatively. However, it is not easy to clarify it by measurements, especially for building with a large scale. In this study, measurements of indoor environment on site along with the multiple interzonal airflow analysis were conducted for a welfare facility for the elderly in Hokkaido. The distributions of air temperature, humidity and CO2 concentration in the building were measured through a winter. As the results, it was shown that the indoor absolute humidity and CO2 concentration became decreased during the operation of an exhaust fan in the kitchen with a large capacity. The decrease occurred even in a room far from the kitchen, and thus it was suggested that the exhausting air from the kitchen predominated the indoor environment of the whole building, and that the air from various spaces in the facility was gathered to the dayroom located next to the kitchen. In addition, an interzonal airflow analysis was performed for this whole building to calculate airflow distribution for a representative day in winter, considering the estimated opening areas, the operating time and airflow rate of all the exhaust fans including kitchen, toilet, bathroom, and the other rooms in the facility, with the air temperature distribution determined based on measured values. The CO2 concentration and absolute humidity balance equations were solved simultaneously, by determining generation rate from persons (CO2 and moisture) and humidifier and bathroom (moisture). The calculated results of distributions of CO2 concentration and absolute humidity were shown to agree well with the measure values. Based on the calculated results of this validated model, it was shown that the air quality of each bedroom satisfied a proper level. The air in the day service center significantly flow into the dayroom of the inhabitants of the facility, which was not proper from the viewpoint of infection control. On the other hand, during nighttime when the exhaust fan in the kitchen was stopped, the airflow was balanced within several blocks dominated by exhaust fans of toilet operated continuously. At last, analysis for two improved cases in ventilation operation were performed; a case of operating the kitchen fan intermittently and a case introducing direct air supply into kitchen equivalent with the exhaust airflow rate of the kitchen fan. As the results, it was shown that the increase in humidity, and saving in heat load are possible within an acceptable levels of increase in CO2 concentration by intermittent operation in the kitchen and introducing direct air supply to the kitchen. Furthermore, in the latter case, although decrease in heat loss by air infiltration into building will be cancelled by heating the air supplied to kitchen, the airflow was balanced within several blocks in the building, which is a merit from the viewpoint of controls of infection or odor diffusion in the facility.

Temporal and distribution characteristic of CO<sub>2</sub> concentration over China based on GOSAT satellite data

Atmospheric CO2 concentration over China has significant effects on the global climate change. To reliably predict the impact of atmospheric CO2 on global climate change, it is necessary to clarify the distribution and variation of atmospheric CO2 concentration. Based on long term short-wavelength infrared CO2 dataset observed by GOSAT, the temporal variation and spatial distribution characteristics and variation trend of atmospheric CO2 concentration was investigated and analysed over China during 2010 to 2016. To ensure the quality of GOSAT CO2 dataset used in this paper, the GOSAT XCO2 dataset was validated with high precise XCO2 from ground-based TCCON sites.Multi-year mean of XCO2 was illustrated to show the spatial heterogeneity of CO2 concentration over China. Interannual variation and annual growth of XCO2 was also presented and discussed. The results showed that GOSAT XCO2 dataset was biased by-1.04±2.10 ppm with respect to TCCON XCO2, and the correlation coefficient was 0.90 between them. Seven years(2010~2016) of GOSAT CO2 dataset showed that high CO2 concentrations were mainly located in Zhejiang-Jiangsu-Anhui region, Beijing-Tianjin-Hebei region, and HunanHubei-Henan-Shanxi region in China. The CO2 concentration reached 400 ppm over most regions in China until 2016. The annual average of CO2 concentration showed an increase trend year by year over China, increasing from 387.76 in 2010 to 402.18 ppm in 2016. The annual growth rate of CO2 concentration was evaluated to be 2.31 ppm/a during this period over China, which was slightly higher than the average in the world. This paper shows that the CO2 concentration observations from satellites could provide some references for the climate change response strategies and atmospheric environment control.

Air quality control in mine refuge chamber with ventilation through pressure air pipeline

A combined experimental and numerical study was performed to improve the performance of the ventilation system in a mine refuge chamber (MRC). In the experiment, CO2 cylinders and dispersion pipes were used to simulate the CO2 release of 50 people, and 0.1L/min per person of fresh air was provided by an air compressor. A new analytical model for a 50-person MRC was proposed and validated against the experimental data. Sensitivity analysis was carried out to investigate the effects of several control factors. The results indicated the following: (1) The ventilation system layout has a significant influence on the CO2 concentration distribution in an MRC, while the uniformity of the CO2 concentration distribution in the MRC may not be effective with increased number of air inlets. (2) Under a well-arranged ventilation system in the 50-person MRC, the average CO2 concentration can be controlled at less than 0.5 % with a ventilation rate of 0.1m3/min per person, and less than 0.2 % with a ventilation rate of 0.3m3/min per person. (3) A quantitative correlation exists between the CO2 concentration and ventilation volume rate, as well as the CO2 release rate, for an MRC under a well-arranged ventilation system.

Study of CO Sources and Early-warning Concentration of Spontaneous Combustion at Air Return Corner in Fully Mechanized Mining Faces

ABSTRACT It is imperative to have an in-depth understanding of CO overrun at the air return corner not only for pre-warning concentrations of safety and spontaneous combustion but also for providing scientific guidance for the CO management. In this study, CO sources and early-warning concentration of spontaneous combustion at the air return corner in fully mechanized mining faces were investigated. Through field measurements, the main sources responsible for CO occurring at the air return corner of the fully mechanized mining face were determined and analyzed, and the basic parameters of mining and ventilation conditions were obtained from the field trials. In the laboratory, an enclosed reactor was introduced and a series of simulated experiments of coal oxidation was carried out to explore coal oxidation at ambient temperature; simultaneously, the temperature-programmed oxidation experiments were also carried out to determine the critical temperature of coal spontaneous combustion and to obtain the rate of CO production at a critical temperature. According to the analysis of the CO source and the production mechanism in the working face as well as both the distribution and migration rules of CO concentration in goaf and working face, a mathematical prediction model of the CO concentration at the air return corner of the working face under normal operation was established. And then the prediction of CO safety and spontaneous combustion early-warning concentrations were calculated based on the CO production rates of coal oxidation under ambient temperature and at a critical temperature. Moreover, a detailed operational process for the practical applications of the mathematical prediction model to the return corner of other fully mechanized mining faces was also proposed.

Study on the smoke movement characteristics in large scale interchange tunnel fire

For the interchange tunnel fire, the structural features of bifurcation and convergence will make the smoke movement characteristics different from the traditional single tube tunnel fire. This paper carried out numerical simulations by ANSYS Fluent to study the smoke movement characteristics in large scale interchange tunnel fire. Different heat release rates, ventilation velocities and bifurcation angles were considered to analyze the carbon monoxide concentration distribution and critical velocity. Results showed that the CO concentration decreased as the ventilation velocity increased and the variation gradient of CO concentration decreased as the distance away from the fire increased. The CO concentration distribution was symmetrical about the longitudinal centerline of the tunnel when the fire located far away from the bifurcation point, and the asymmetric distribution phenomenon disappeared while the fire located at the bifurcation point. In addition, the critical velocity increased as the bifurcation angle increased while the fire located at the bifurcation point. However, the bifurcation angle had no direct impact on the critical velocity when the fire located far away from the bifurcation point.

Coke solution-loss degradation model with non-equimolar diffusion and changing local pore structure

To provide a more accurate reference for coke quality evaluation, and to achieve the benefits of coking-coal resource use and energy conservation, a coke solution-loss degradation model was developed by combining non-equimolar diffusion, the parallel pore model, the random pore model and an ever-changing local pore structure. The model could predict the coke solution-loss behavior and degradation behavior to improve the understanding of the coke solution-loss degradation mechanism. The model is of value for application by coking and ironmaking workers. The model was verified by the coke overall weight-loss(%) and local porosity after reaction. The predicted results showed a good fit with the experimental data. The CO2 concentration on the coke outer surface and the CO2 concentration distribution in the inner coke decreased because of the effect of non-equimolar diffusion. The coke solution-loss behavior and degradation behavior were presented by a three-dimensional diagram of CO2 concentration and the local inner coke porosity, respectively. The model was verified by the effectiveness factor and coke strength after reaction (CSR25) separately, and the conclusion could be drawn that the gradient distribution of the CO2 concentration and local-porosity inner coke could cause the greatest degradation and yield the worst coke strength after reaction.

Influence of interphase mass transfer and diffusion processes on CO2-brine displacement in saline aquifers

The geological storage of CO2 in saline aquifers involves various geophysical and geochemical mechanisms, in which different mechanisms play different roles at different time scales and different stages as well. At the initial stage during CO2 continuously injected into saline aquifers, the non-equilibrium mass transfer process is one of the main factors affecting the interfacial evolution of two-phase flow. In this work, a model that couples the two-phase displacement process in saline aquifers with single-phase dissolution-diffusion is established for the initial stage of CO2 injection, which features that the non-equilibrium mass transfer method is used to describe the interfacial evolution during the two-phase flow. The model is numerically solved and verified. The influences of mass transfer and diffusion on the distributions of CO2 plume and CO2 concentration in the wetting phase are investigated. In the initial stage of CO2 injection, the Stanton number (St), representing the ratio between mass transfer process and convection process, significantly affects both the non-wetting phase at the leading edge and the CO2 concentration distribution in the wetting phase. The Peclet number (Pe), representing the ratio between convection process and diffusion process, is a secondary factor and has limited effects on the non-wetting phase saturation and wetting phase CO2 concentration distribution. At the initial stage, the dissolution of CO2 during injection into saline aquifers is dominated by a large St or small Pe. The proposed model provides a useful tool and insight in analyzing the interfacial evolutions of the CO2-brine displacement process when interfacial mass transfer is considered.

Investigation of temperature and CO2 concentration in converter gas flames by a combustion diagnostic system based on TDLAS

In this study, a novel combustion diagnostic system based on tunable diode laser absorption spectroscopy (TDLAS) was developed to simultaneously measure the temperature and CO2 concentration in flames on a turbulent partly premixed burner. This system simulates harsh industrial combustion environment and enables in situ measurements of non-uniform temperature and CO2 concentration distributions in converter gas-air flames. A mixture of CO, CO2, and N2 with the volume percentage ratio 80:15:5 was injected into the fuel stream to simulate effects of converter gas. Temperature and CO2 concentration in flames along the axial direction at the burner centerline were simultaneously measured by online TDLAS. The flame temperature was compared with that obtained by thermocouple measurement. The CO2 concentration was compared with those of samples taken from the flame. The results of online TDLAS measurements showed the same variation trend as temperature in the core of the flames measured using thermocouples and CO2 concentration obtained from the analysis of samples. This work proved that non-uniform temperature and CO2 concentration distributions in converter gas flames could be measured by this system and laid the foundation for further study about the effects of CO2 and/or N2 addition on converter gas/air flames.

Temporal and spatial distribution of the mid-tropospheric CO2 concentrations in Malaysia

Satellite observations of CO2 offer a unique opportunities to improve our understanding of the carbon sources and sinks. Due to the lack of studies of carbon dioxide (CO2) concentration in this region, we first confirmed the reliability of the mid-tropospheric Atmospheric Infrared Sounder (AIRS) CO2 data using atmospheric CO2 concentration data from the only available Global Atmospheric Watch (GAW) ground-based station observation in Malaysia. In this study, the spatial and temporal distribution of mid-troposphere CO2 in Malaysia from January 2009 to December 2012 was analyzed based on AIRS satellite product. The results show that the average CO2 concentrations were high in the eastern part of the study area and lower in the west. From January 2009 to December 2012, the mid-tropospheric CO2 concentrations increased gradually with annual growth rate about 1.293 ppmv/a. There was a significant seasonal CO2 variation with peak concentration was observed during the North-East monsoon (NEM) and the lowest was during South-West monsoon (SWM). The temporal distribution of CO2 concentrations was mainly affected by the amount of sunlight and precipitation received during both monsoons. The study suggested that mid-tropospheric AIRS CO2 data product was able to help in understanding the variations of atmospheric CO2 concentrations comprehensively.

Carbonation modelling for cement-based materials considering influences of aggregate and interfacial transition zone

The influences of aggregate and interfacial transition zone (ITZ) on the carbonation resistance of cement-based materials cannot be ignored. Based on Fick's second law, a CO2 diffusion model considering the influences of aggregate and ITZ is proposed in this work. Subsequently, the computing methods of corresponding parameters in this model are presented. A CO2 reaction model based on the law of conservation of mass is also proposed. The reliability of theoretical modelling was further verified by comparisons with experimental data from the literature. Finally, this model was used to study the concentration distribution of CO2 in C30 and C50 concrete with and without load effects. The results showed that the carbonation prediction method considering the influences of aggregate and ITZ was capable of handling the diffusivity of CO2 in cement-based materials. This theoretical model can predict the carbonation depth values with reasonable accuracy. Therefore, this model can be used as a practical tool considering the existence of aggregate and ITZ as a significant factor to evaluate the durability of concrete. Thus, it can help to design and predict the service life of reinforced-concrete structures.