Cement Hydration Reaction Research Articles

Microstructural evaluation of composites incorporated with industrial waste

Oil sludge is waste, which has a potential impact on nature and human health. Solidification/stabilization technology has stood out as an effective approach to treating this waste by transforming it into non-toxic, insoluble forms. Thus, the objective of the present research was to treat hazardous organic waste, through stabilization by solidification and evaluate the resulting matrix, through X-ray Diffraction Analysis, Scanning Electron Microscopy and Thermogravimetric Analysis. Cementitious matrices were prepared with addition of 5% and 20% oil sludge. After the curing time, the specimens were ground and submitted for characterization analyses. This, indicated a high organic mass to be treated and presented an amount of chromium above the maximum permissible limit. The incorporation of the oil sludge did not have a significant impact on the hydration reactions of the cementitious matrices, as indicated by the characteristic peaks of Portlandite and Calcium Silicate. The scanning electron microscopy analysis pointed out that the oil sludge did not interfere in the cement hydration reactions, resulting in the formation of the main hydration products. There was a significant difference in mass losses between the treatment with 5% and 20% oil sludge, with greater losses when incorporating a larger amount of residue, while the curing time had no significant influence.

Influence of fine recycled concrete aggregates use on the hydration kinetics and mechanical–microstructural properties of hydrated cement: Experimental and numerical approaches

The purpose of this study was to investigate the influence of fine powder (SF fines) obtained from recycled concrete aggregate on the hydration kinetics and mechanical–microstructural properties of hydrated cement through experiments and three-dimensional microstructural modelling using CEMHYD3D. Mixtures prepared with different substitution levels ranging from 0 % to 30 % by volume were examined. The experimental results indicated that the presence of calcite (CaCO3) and residual hydrates in SF powder accelerated the hydration of cement phases, particularly the C3A and C3S phases, at early ages. Increasing the SF fines substitution level led to an increase in the degree of hydration (DoH) of cement compared to that of the reference. The compressive strengths of mortars decreased with SF powder substitution levels; however, a substitution rate of 10 % led to a strength comparable to that of the reference. The modelling results also indicated that increasing the SF fines substitution level increased the DoH of cement. However, at very early ages, the hydration retardation of individual cement phases increased with increasing SF powder substitution levels, particularly for the C3A and C4AF phases. The findings of the study suggest that SF fines can act as fillers, increasing the nucleation zones for cement hydration reactions, and as silico-aluminous sources for pozzolanic reactions.

The prediction of compressive strength for recycled coarse aggregate concrete in cold region

Concrete in cold environments may suffer from frost damage, which effects the hydration reaction and early strength development of cement. This study aims to test the early strength development of recycled coarse aggregate concrete in cold region using an assisted heating method. Based on Nurse-Saul and Hansen-Pedersen maturity calculation methods, the early strength of recycled and natural coarse aggregate concrete is fitted and predicted using exponential and logarithmic type functions. The results showed that active heating and thermal insulation can ensure early concrete hydration. The temperature of recycled coarse aggregate concrete was slightly higher than that of natural concrete, while its strength was slightly lower. The early strength development of natural and recycled coarse aggregate concrete correlated more with the logarithmic type function. The prediction error of natural and recycled coarse aggregate concrete is basically within 10% for the first 14 days of compressive strength.

Исследование продуктов гидратации пенобетонов неавтоклавного твердения

The published work presents an X-ray phase analysis of non-autoclaved foam concrete. According to the results of X-ray phase analysis of non-autoclaved foam concrete, it was found that by 56 days of normal hardening, further reactions of cement hydration and binding of $Ca(OH)_2$ occur, reflections of tobermorite-like low-basic calcium hydrosilicates CSH (II) increase with d = (3.07; 2.10 ) Å, which are involved in the hardening process, which consists in the monolithic foam concrete matrix, the formation of a glossy porous layer, the healing of defects in the interpore partitions, which leads to a significant increase in the operational characteristics of the material.

The very early-age behaviour of Ultra-High Performance Concrete containing ground granulated blast furnace slag

Ultra-High Performance Concrete (UHPC), despite being a relatively new kind of advanced cement-based material (featuring outstanding mechanical performance and excellent durability), has been deemed unsustainable due to its high cement content, thus increasing its carbon footprint. The large amounts of cement and silica fume (SF) can also raise both production costs and cracking risks due to the high early-age autogenous shrinkage. This paper addresses an innovative approach for developing a more sustainable UHPC involving an efficient application of ground granulated blast furnace slag (GGBS). Slags of two fineness levels are used, displaying a Blaine fineness of 420 m2/kg (SL1) and 700 m2/kg (SL2), respectively. These slags have been incorporated as volume replacements for 30% and 50% cement.The results analysis shows that it is indeed possible to produce SL2-based UHPC with a behavior similar to that of classical silica fume-based materials. The partial replacement of ordinary Portland cement (OPC) by 30% of GGBS (SL1 or SL2) improves workability, promotes the hydration reaction of cement and accelerates setting. In this case, the nucleation site effect of GGBS particles dominates; it seems to be directly correlated with the fineness of the slag used. Thus, the finer additions result in a significant acceleration of setting and hydration. The dilution effect is more sensitive at 50% of SL1 substitution. This prevailing effect delays the hydration reaction, prolongs setting times and decreases the peak of heat flow. In contrast however, this delay effect was not observed for the mixture containing 50% of SL2. Shrinkage measurements indicated that 30% of SL1 induces a slight reduction in early-age chemical and autogenous types of shrinkage. The most severe shrinkage is clearly found in mixtures incorporating 30% of SL2. This phenomenon may be due to the distribution of refined pores, which increases capillary tension. A more sustainable UHPC containing a high level of superfine slag (50%) with less autogenous shrinkage has been successfully produced.

Measuring the early-age volumetric change of cement paste through in-situ XRD

Volumetric changes follow Portland cement hydration reactions: aluminates' hydration is generally expansive, whereas silicates' reaction leads to shrinkage. Determining the volumetric variation at very early ages (i.e., first minutes/hours) presents operational challenges; most standards prescribe the measurement on specimens that are already hardened, while measurements from the fresh state are not standardized. This article reports the first attempt to use in-situ X-ray diffraction (XRD) to measure the early-age volumetric variation of a cementitious paste. For this purpose, a C3A + gypsum paste was assessed for 36 h, measuring its vertical displacement over time through XRD. The results showed that the expansion increased in the first ∼13 h, in line with the ettringite formed up to ∼11 h. In addition, the volumetric expansion agreed well with the heat release in calorimetry. It is concluded that the volumetric variation measurement of cementitious pastes through in-situ XRD is a promising technique, but further studies are needed to make this technique consolidated.

Carbon-cement supercapacitors as a scalable bulk energy storage solution.

The large-scale implementation of renewable energy systems necessitates the development of energy storage solutions to effectively manage imbalances between energy supply and demand. Herein, we investigate such a scalable material solution for energy storage in supercapacitors constructed from readily available material precursors that can be locally sourced from virtually anywhere on the planet, namely cement, water, and carbon black. We characterize our carbon-cement electrodes by combining correlative EDS-Raman spectroscopy with capacitance measurements derived from cyclic voltammetry and galvanostatic charge-discharge experiments using integer and fractional derivatives to correct for rate and current intensity effects. Texture analysis reveals that the hydration reactions of cement in the presence of carbon generate a fractal-like electron-conducting carbon network that permeates the load-bearing cement-based matrix. The energy storage capacity of this space-filling carbon black network of the high specific surface area accessible to charge storage is shown to be an intensive quantity, whereas the high-rate capability of the carbon-cement electrodes exhibits self-similarity due to the hydration porosity available for charge transport. This intensive and self-similar nature of energy storage and rate capability represents an opportunity for mass scaling from electrode to structural scales. The availability, versatility, and scalability of these carbon-cement supercapacitors opens a horizon for the design of multifunctional structures that leverage high energy storage capacity, high-rate charge/discharge capabilities, and structural strength for sustainable residential and industrial applications ranging from energy autarkic shelters and self-charging roads for electric vehicles, to intermittent energy storage for wind turbines and tidal power stations.

Flow Lattice Model for the simulation of chemistry dependent transport phenomena in cementitious materials

This study presents the formulation and validation of a three-dimensional Flow Lattice Model (FLM) with application to the Hygro-Thermo-Chemical (HTC) model for analysis of moisture transport and heat transfer in cementitious materials. The FLM is a discrete transport model formulated in association with meso-mechanical models, such as the Lattice Discrete Particle Model. This enables the simulation of transport phenomena at the length scale at which the material exhibits intrinsic heterogeneity. The HTC theoretical formulation is based on mass and energy conservation laws, written using humidity and temperature as primary variables, and considering explicitly various chemical reactions, for example, cement hydration and silica fume reaction, as internal variables. In this work, the HTC formulation was extended to include the effect of temperature on the sorption isotherm. The FLM solutions were compared with those of a continuum finite element implementation of the HTC model and experimental data available from the literature; the overall agreement demonstrates the reliability of the proposed approach in reproducing phenomena such as cement hydration, self-desiccation and temperature-dependent moisture drying.

Mechanical Properties of Composite Silty Soil Modified with Cement and Zirconia-Based Nanopowder.

This study assessed the modification effects of zirconia-based nanopowder and cement contents and curing age on the mechanical properties of silty soil. The orthogonal test design was applied to derive the best combination of each influencing factor using the lateral unconfined compressive test. Two-dimensional particle flow code (PFC2D) distinct-element modeling software was also used to fit and analyze the test curves, as well as simulate the triaxial test with the derived parameters. The test results reveal the optimal combination of 20% cement, 2% zirconia-based nanopowder, and 28 d curing age. The extreme difference table was used to plot the orthogonal trend diagram, and cement content was found to be the most significant factor controlling the silty soil strength. The maximum peak stress was 2196.33 kPa under the optimum combination of factors, which could be obtained through the index estimation, and these results were experimentally verified. According to the predicted strength envelope, the cohesive force of nanopowder-cement-modified silty soil in the optimal proportion was 717.11 kPa, and the internal friction angle was 21.05°. Nano zirconium dioxide will accelerate the hydration reaction of cement, the flocculent structure produced by the hydration of cement and soil particles connected to each other, play the role of filling and anchoring, and thus increase the strength of the nano-zirconium dioxide, and the optimal dosage of nano-zirconium dioxide is 2%.

Experimental Investigation of Mechanical Properties of Clay–Cement Slurry Containing Graphene Oxide

As a widely used material in underground engineering, clay–cement slurry grouting is known for its initial poor anti-seepage and filtration capacity, the low strength of the resulting stone body, and its tendency towards brittle failure. To explore efficient and environmentally friendly grouting materials, industrial-grade graphene oxide (GO) was incorporated into a clay–cement slurry to create a new type of slurry called a GO composite. These GO composites were then utilized to reinforce fractured formations. Uniaxial compression tests, shear strength tests, permeability tests, and electron microscopy scans were conducted to investigate the strength, permeability, and microscopic features of the GO composite-reinforced fractured formations. Furthermore, the optimization effect and application prospects of graphene oxide on clay–cement slurry materials were evaluated. The experimental results demonstrated that the modified slurry effectively improved the compressive strength (increased by 7.2% to 32.5%) and shear strength (increased by 28.6% to 105.3%) of consolidated fractured gravel. By conducting orthogonal experiments with range analysis, variance analysis, and multiple regression analysis, it was shown that there was a strong correlation between the consolidated body and three factors influencing the permeability coefficient. Among these factors, the OPC content had the most significant impact on the permeability coefficient, followed by the GO content. Graphene oxide was found to promote cement hydration reactions, guide the growth of hydration products on the surface of graphene oxide nanosheets, optimize the pore structure in grouting materials, and reduce microcracks between the slurry and the fractured gravel interface. Electron microscopy characterization and fractal analysis revealed that the addition of graphene oxide effectively reduced the degree of microdamage during the sample’s failure process. This ensured the integrity of the sample during the unstable failure process, enhanced the material’s toughness, and improved its ability to resist loads.

Investigation of the Mechanical Properties of Iron Tailings Concrete Subjected to Dry-Wet Cycle and Negative Temperature.

This research investigates the effects of iron tailings content on the mechanical properties and durability of concrete under dry-wet cycling and negative temperature conditions (-10 °C), where iron tailings replace river sand at rates of 0%, 10%, 20%, and 30%. A variety of tests were conducted on the iron tailings concrete, including compressive strength, flexural strength, splitting tensile strength, mass loss, and relative dynamic modulus, and its pore characteristics were analyzed using low-field nuclear magnetic resonance (NMR) experiments. The results reveal that when 20% of the river sand was replaced with iron tailings, the concrete achieved optimal splitting strength, compressive strength, and flexural strength at 28 days, improving by 0.46 MPa, 3.14 MPa, and 0.41 MPa, respectively, compared to conventional concrete. Furthermore, the concrete containing this proportion of iron tailings demonstrated superior mechanical properties and durability in both negative temperature conditions and dry-wet cycling experiments. Due to the excellent physical and chemical properties of iron tailings, they enhance the performance of concrete when incorporated in appropriate quantities. The fine granularity of iron tailings helps to compensate for the granularity defects in concrete aggregates by filling internal voids, optimizing the pore structure, and improving the concrete's density and integrity. This enhances the concrete's mechanical properties and its resistance to external solutions and harmful ion penetration. Additionally, the active substances in iron tailings promote the hydration reaction of cement, leading to the formation of an increased amount of C-S-H gel and other hydration products in the cement system.

Converting coastal silt into subgrade soil with biochar as reinforcing agent, CO2 adsorbent, and carbon sequestrating material

Large amounts of coastal silt produced annually is urgent to be treated with a feasible strategy. This study converted it into subgrade soil by cement solidification for resource utilization. Biochar was used as exogenous additive for enhancing compressive strength of the product, simultaneously achieving carbon sequestration. Three biochars derived from peanut shells (PSBC), cow dung (CDBC) and sewage sludge (SSBC) at 300 °C, 500 °C and 700 °C pyrolysis, were added into raw materials with 1%, 2% and 5%, respectively. All biochars significantly improved the compressive strength of the subgrade soil by 20–110%. Biochar catalyzed cement hydration reactions to produce more Ca(OH)2, CaCO3 and calcium silicate hydrates (C–S–H gel). The catalytic capacity of different biochars followed the order of SSBC > PSBC > CDBC. Addition of 2% SSBC500 induced the greatest increase in 28 d-strength from only 1.0 MPa–2.1 MPa, which was due to that 500 °C biochar had a suitable specific surface area and porosity. Biochar facilitated CO2 capture (absorption) during the hydration reactions at the initial 48 h with 55–70 mg g−1. The high alkalinity and water holding capacity of biochar contributed to the absorption of CO2; the high content of minerals in SSBC compared to CDBC and PSBC promoted chemical conversion of CO2 to carbonate. Besides, the biochar itself as carbon rich material was encapsulated in the subgrade soil, which can be regarded as a long-term carbon sequestration strategy. Carbon budget analysis demonstrated that converting one ton dry silt into subgrade soil with addition of 2% biochar could increase CO2 sequestration from 11 kg to 36–94 kg. This study proposes a novel strategy of using biochar to strengthen the subgrade soil simultaneously achieve long-term carbon sequestration.

The Macro and Micro Effects of Graphene Oxide and Silica Fume on the Performance of Concrete under Standard Curing Conditions

Herein, the properties of concrete containing graphene oxide (GO) and silica fume (SF) are systematically investigated. The results show that the excellent properties of GO and SF have a significant improvement effect on the performance of concrete. Among them, the compressive, splitting tensile, and flexural strength of B‐1 group (GO, 0.01 wt% and SF, 2.5 wt%) are increased by 11.04%, 12.23%, 20.11% compared with the reference group after 3 days of curing. Meanwhile, the water penetration height of B‐1 group is decreased by 59.67% compared with reference group. The mass loss and relative dynamic modulus loss are 5.32% and 8.89% after 75 freeze‐thaw cycles, which are much lower than the reference group. Moreover, the micromodification mechanism of GO and SF on the concrete is investigated by using X‐ray diffraction analysis, scanning electron microscopy, and mercury intrusion porosimetry. The results show that the incorporation of GO and SF promotes the early hydration reaction of cement, improves the internal structure of the matrix, and enhances the compactness of the matrix.

Mix design and 3D printing correlation performance of Pcc-based 3DPM

This paper presents the experimental results concerning the mix design and 3D printing correlation performance of a completely new printing material, Portland cement clinker (Pcc). According to the results, the cement-sand ratio is 0.6–1.0, the water-cement ratio is 0.34–0.4, and the setting time of Pcc paste is approximately 5 min. When it increases, the rheology (G', G″, |η*|, torque) of Pcc paste also increases. Furthermore, when the cement-sand ratio and water-cement ratio increase, the maximum flexural strength and compressive strength of the mortar at 28 days are 7.93 MPa and 44.76 MPa, respectively. The ultimate swelling degree of the mortar increases from 18 cm to 22 cm, the final slump increases from 4.0 cm to 4.5 cm. When the ratio is D-2, the extrusion length is 70 mm, and the maximum number of printing layers is 17 layers. According to the SEM image analysis of the sample, the hydration products primarily include hydrated calcium silicate, calcium hydroxide, and others, which is supported by the XRD test results. In addition, the reaction model of Pcc is proposed. The results of Pcc hydration reaction analysis indicate that adding a water-lowering agent can slow the cement hydration reaction.

Mechanical and Microscopic Properties of Cement Composite Expansive Soil with Graphene Oxide: Ecofriendly Modification Material

Cement composite soil is a more stabilized method in expansive soil foundation projects, but it is essential to find an ecofriendly modification material to reduce the content of cement and its pollution for the environment. A series of unconsolidated–undrained (UU) triaxial tests were conducted to investigate the modification effect of graphene oxide (GO) on cement-stabilized expansive soil (CS), and the contents of GO were 0.05%, 0.1%, 0.15%, and 0.2%, respectively. The test results show that (1) the deviatoric stress–strain curves of CS gradually change from a weakly softening type to a strongly softening one after adding GO. (2) The compressive strength, shear strength, and toughness of GO-modified cement-stabilized expansive soil are better than CS, and the optimal GO content is 0.05%. (3) Microscopic tests show that GO can promote the hydration reaction of cement and reduce the internal pores of CS. Consequently, the mechanical properties and microstructure of CS can be significantly improved after adding GO, and it is feasible to replace a part of the cement with GO in expansive soil foundation projects.

Mix proportion optimization and early strength development in modified foam concrete: an experimental study

The influence of the single polycarboxylate superplasticizer (PCE) and blending it mixed hydroxypropyl methylcellulose (HPMC) on hardening moulding quality and surface pulverisation of foam concrete was investigated. An orthogonal experimental design was employed to determine the optimum combination of parameters for four property indexes (PIs) in this paper. A multi-index matrix analysis method was used to evaluate the parameter combinations and obtain the overall optimal performance for the PIs. The effect of calcium formate (CaF) on the early compressive strength of modified foam concrete with the most optimal combination in different density grades was also studied. The results indicate that the incomplete cement hydration reaction is the essential cause of pulverisation, which can be alleviated by adding a suitable PCE. Defoaming and precipitation occur when the PCE incorporated exceeds 0.1%, which can be mitigated by the addition of 0.02 to 0.06% HPMC. The orthogonal analysis indicates that the anti-cracking agent has a more substantial effect on the strength of the foam concrete than the thickening agent. The most significant factor of mechanical properties is PP fiber followed by dispersible latex powder (DLP). The optimal combination of foam concrete is 0.06% HPMC, 0.3% DLP, and 0.5% PP fiber. The early compressive strength of foam concrete can be significantly enhanced by increasing the CaF content. However, increasing the density level results in a decrease in the 28-day compressive strength of the foam concrete.

Molecular simulation for the relationship between the functional groups of chemical admixtures and cement hydration product Ca (OH)2 in the grouting process

Complex geological problems caused by natural environment have emerged constantly, causing serious damage to the land use and groundwater ecological environment in the western region. How to deal with the relationship between the above factors and ecological environment protection is a new research topic at present. Broken rock mass, cracks and water inrush during construction can be blocked and reinforced by grouting to achieve environmental protection. Therefore, to develop accurate quantitative models for the hydration of cement and predict the properties of grouting materials plays a crucial role during the protection process. In this study, the hydration product Ca(OH)2 is taken as an example, and the adsorption processes of different functional groups on the surface of Ca(OH)2 were investigated using DFT. The adsorption energy of the (101) surface was −0.38 Ha in sulfonic group, the lowest on different crystal planes of Ca(OH)2, while the adsorption energy of different functional groups is sulfonic group > carboxyl group > amide group > benzene ring. The adsorption energy was the lowest when the hydroxyl and carboxyl ratio was 1:1, suggesting that the adsorption energy and hydration performance in different ratios of hydroxyl and carboxyl groups will also be discrepant. After the adsorption of functional groups with Ca(OH)2, the electron clouds and orbitals rearranged, new characteristic peaks of the s orbital were present in the vicinity of −15 eV, −13 eV, and −10 eV, respectively. Since the relationship between functional groups and cement hydration process of chemical admixtures was explored, the mechanism of the cement hydration reaction and the influence of cement-based admixtures was revealed from an electronic view, also to extract the key influencing factors for the grouting and develop accurate quantitative models to predict and tackle various geo-environmental hazards.

Digital reconstruction of a concrete pile from temperature data and boundary element formulation

This paper presents an application of the boundary element method (BEM) in engineering to numerically analyse the integrity of cast-in-place concrete foundations, as in the case of concrete piles, using a developed system composed of an artificial heat source, thermometers coupled with metal reinforcement and mathematical algorithms. This type of integrity monitoring of concrete piles is present in recent articles where temperature measurements occur only during the cement curing process, related to the cement hydration reaction in a time interval of a few days. However, the innovation proposed in this study refers to the possibility of continuous monitoring of the pile, considering the installation of an artificial heat source, whose temperature measurements will allow evaluating the positioning of the metal reinforcement inside the pile, in order to identify possible concreting anomalies and/or exposure of metal rods to the ground, where metal corrosion can be more pronounced. The diffusion equation with heat generation and the D-BEM formulation is used to simulate a cross-section of the set of soil and concrete pile with metal reinforcement in different situations. Details on the formulation of boundary elements used, as well as numerical results on the feasibility of the methodology developed to monitor the integrity of cast-in-place concrete foundations, are presented below.

Influence of brine on hydration reaction of calcium sulfoaluminate and slag blended cement

A study was conducted to develop an eco-friendly, low-carbon cement and to find new applications for waste brine discharged from seawater desalination plants. As the binder, a binary blended binder of calcium sulfoaluminate type K expanding agent (CSA) classified as ACI 223R-10 and slag was used. The CSA content was 0%, 10%, 20%, and 30% substituted. For mixed water, freshwater and brine were used. The brine promoted the hydration reaction of the CSA to promote the formation of ettringite and increased the pore content of 50 nm or less to form a dense matrix, thereby improving the mechanical performance. The 20% CSA sample exhibited the best strength for freshwater and brine samples. However, for the 30% CSA, a decrease in strength was measured, which is due to the excessive expansion effect. Mixing the CSA–slag-blended cement and brine suggests the possibility of its application as a new construction material.

Hydration and material properties of blended cement with ground desert sand

The potential of existing supplementary cementitious materials (SCMs), such as fly ash and slag, has been dramatically decreased after decades of use. For future development, finding new SCMs to address the sustainability issue of cement and concrete is essential. Due to its global distribution and reserves, and the fact that it has not been officially used for construction, desert sand may become a new option for SCM for cement. Since desert sand has a very fine and uniform particle size, regular milling in the field can conveniently transform it into a powder comparable to cement fineness. This study investigated the technical possibility of desert sand powder as an SCM through physical experiments, thermodynamic modeling, and life cycle analysis. The mechanical strength of blended cement with desert sand powder was generally lower than that of pure cement due to the cement reduction and increased effective water-cement ratio. When the dosage of desert sand powder was within 15%, the 28-day strength of blended cement exceeded 75% of that of pure cement, and the strength development of blended cement was better than that of pure cement after 28 days till long curing ages (112 days). Both the initial and renewed stages of early cement hydration were promoted by desert sand powder. The desert sand powder's leading minerals, quartz and calcite, participated in the cement hydration reactions, generating corresponding hydration products, calcium silicate hydrate (C-S-H) and carbonate-based aluminate ferrite mono-sulfate (AFm). The microstructure showed the interactions between the desert sand powder particles and the hydrated cement matrix, including physical and chemical aspects. In the case of high dosage, the hardened matrix's pore structure was apparent with a less dense matrix due to excess water and reduced hydration products. The thermodynamic modeling theoretically quantified the phase assemblage of hydrated cement with desert sand powder, connecting to the observed reactivity of desert sand powder in cement hydration. The life cycle analysis showed that the carbon emission of desert sand powder was comparable to the conventional SCMs (fly ash and limestone powder). However, if it was proposed to be used outside the desert and surrounding regions, the carbon emission may increase due to the extended transportation distance.