Mechanical Property and Microstructure of Cement Mortar with Carbonated Recycled Powder

Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM,the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM,and the strengthening mechanism was analyzed.The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate.It is suggested that the replacement rate of recycled powder should not exceed 20%.The strength index and activity index of carbonated recycled powder mortar were improved,in which the flexural strength was increased by 27.85%and compressive strength was increased by 20%at the maximum.Recycled powder can be quickly and completely carbonated,and the improvement effect of CH pre-soaking carbonation was the best.The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder.Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect,alkaline polycondensation effect and carbonation enhancement effect.

The impact of connate water saturation and salinity on oil recovery and CO2 storage capacity during carbonated water injection in carbonate rock

Carbonated water injection(CWI)is known as an efficient technique for both CO2 storage and enhanced oil recovery(EOR).During CWI process,CO2 moves from the water phase into the oil phase and results in oil swelling.This mechanism is considered as a reason for EOR.Viscous fingering leading to early breakthrough and leaving a large proportion of reservoir un-swept is known as an unfavorable phenomenon during flooding trials.Generally,instability at the interface due to disturbances in porous medium promotes viscous fingering phenomenon.Connate water makes viscous fingers longer and more irregular consisting of large number of tributaries leading to the ultimate oil recovery reduction.Therefore,higher in-situ water content can worsen this condition.Besides,this water can play as a barrier between oil and gas phases and adversely affect the gas diffusion,which results in EOR reduction.On the other hand,from gas storage point of view,it should be noted that CO2 solubility is not the same in the water and oil phases.In this study for a specified water salinity,the effects of different connate water saturations(Swc)on the ultimate oil recovery and CO2 storage capacity during secondary CWI are being presented using carbonate rock samples from one of Iranian carbonate oil reservoir.The results showed higher oil recovery and CO2 storage in the case of lower connate water saturation,as 14%reduction of Swc resulted in 20%and 16%higher oil recovery and CO2 storage capacity,respectively.

Mechanical performances and microstructural characteristics of reactive MgO-carbonated silt subjected to freezing-thawing cycles

The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering performances.Under the binder content of 15%and initial water content of 25%,MgO-admixed silt specimens were carbonized for 3 h and 6 h and then subjected to different numbers of freezingthawing(F-T)cycles.After different F-T cycles,the physico-mechanical properties of MgO-carbonated silt were analyzed in comparison with Portland cement(PC)-stabilized silt through physical and unconfined compression tests.Besides,a series of micro tests on MgO-carbonated specimens was performed including X-ray diffraction(XRD),scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests.The results demonstrate that both mass change ratio and moisture content of carbonated/stabilized silt decrease,and these values of MgO-carbonated silt are significantly lower while the density is higher compared to PC-stabilized silt.The strengths and moduli of MgO-carbonated silt are still two times higher than those of PC-stabilized specimens and the strength change ratio of keeps above0.8 after F-T cycles.There is no visible transformation between nesquehonite and dypingite/hydromagnesite,although the XRD peaks of nesquehonite decrease and the bonding and filling effects weaken slightly.After 6 and 10 F-T cycles,the pore-size characteristics changed from a unimodal distribution to a three-peak and bimodal distribution,respectively.The total,macro and large pore volumes increase obviously while the medium and small pore volumes decrease except for intra-aggregate pore.The findings show better F-T durability of MgO-carbonated silt,which would be helpful for facilitating the application of MgO carbonation in the soil treatment.

Enhancing the spontaneous imbibition rate of water in oil-wet dolomite rocks through boosting a wettability alteration process using carbonated smart brines

Most fractured carbonate oil reservoirs have oil-wet rocks.Therefore,the process of imbibing water from the fractures into the matrix is usually poor or basically does not exist due to negative capillary pressure.To achieve appropriate ultimate oil recovery in these reservoirs,a water-based enhanced oil recovery method must be capable of altering the wettability of matrix blocks.Previous studies showed that carbonated water can alter wettability of carbonate oil-wet rocks toward less oil-wet or neutral wettability conditions,but the degree of modification is not high enough to allow water to imbibe spontaneously into the matrix blocks at an effective rate.In this study,we manipulated carbonated brine chemistry to enhance its wettability alteration features and hence to improve water imbibition rate and ultimate oil recovery upon spontaneous imbibition in dolomite rocks.First,the contact angle and interfacial tension(IFT)of brine/crude oil systems were measured for several synthetic brine samples with different compositions.Thereafter,two solutions with a significant difference in WAI(wettability alteration index)but approximately equal brine/oil IFT were chosen for spontaneous imbibition experiments.In the next step,spontaneous imbibition experiments at ambient and high pressures were conducted to evaluate the ability of carbonated smart water in enhancing the spontaneous imbibition rate and ultimate oil recovery in dolomite rocks.Experimental results showed that an appropriate adjustment of the imbibition brine(i.e.,carbonated smart water)chemistry improves imbibition rate of carbonated water in oil-wet dolomite rocks as well as the ultimate oil recovery.

Activating solution gas drive as an extra oil production mechanism after carbonated water injection

Enhanced oil recovery(EOR)methods are mostly based on different phenomena taking place at the interfaces between fluid–fluid and rock–fluid phases.Over the last decade,carbonated water injection(CWI)has been considered as one of the multi-objective EOR techniques to store CO2 in the hydrocarbon bearing formations as well as improving oil recovery efficiency.During CWI process,as the reservoir pressure declines,the dissolved CO2 in the oil phase evolves and gas nucleation phenomenon would occur.As a result,it can lead to oil saturation restoration and subsequently,oil displacement due to the hysteresis effect.At this condition,CO2 would act as insitu dissolved gas into the oil phase,and play the role of an artificial solution gas drive(SGD).In this study,the effect of SGD as an extra oil recovery mechanism after secondary and tertiary CWI(SCWI-TCWI)modes has been experimentally investigated in carbonate rocks using coreflood tests.The depressurization tests resulted in more than 25%and 18%of original oil in place(OOIP)because of the SGD after SCWI and TCWI tests,respectively.From the ultimate enhanced oil recovery point of view,the efficiency of SGD was observed to be more than one-third of that of CWI itself.Furthermore,the pressure drop data revealed that the system pressure depends more on the oil production pattern than water production.

The role of CO2 and ion type in the dynamic interfacial tension of acidic crude oil/carbonated brine

The e ects of CO2 and salt type on the interfacial tension(IFT) between crude oil and carbonated brine(CB) have not been fully understood. This study focuses on measuring the dynamic IFT between acidic crude oil with a total acid number of 1.5 mg KOH/g and fully CO2-saturated aqueous solutions consisting of 15,000 ppm of KCl, NaCl, CaCl2 and MgCl2 at 30 °C and a wide range of pressures(500–4000 psi). The results of IFT measurements showed that solvation of CO2 into all the studied aqueous solutions led to an increase in IFT of acidic crude oil(i.e., comparison of IFT of crude oil/CB and crude oil/brine), while no significant e ect was observed for pressure. In contrast, the obtained results of studied salts indicated a positive e ect on the IFT reduction of acidic crude oil/carbonated water(CW)(i.e., comparison of IFT of crude oil/CB and crude oil/CW).

Nanometre Carbonated Hydroxyapatite Powders Synthesis Controlled by Lecithin in Synthetic Body Fluids

Nanocrystal carbonated hydroxyapatite was prepared by lecithin-controlled chemical precipitation in synthetic body fluid （SBF）. The reactant was aged and heated at 850℃ for crystallization. The morphology and microstructure of the carbonated hydroxyapatite were investigated using transmission electron microscope （TEM）, X-ray diffraction （ XRD ） and FTIR. The experimental results demonstrate that the shapes of carbonated hydroxyapdtite particles display spheres with the average size of 20- 28 nm, and carbonated hydroxyapatite contained carbonate ions, similar to mineral of bone tissues.

Association between the Consumption of Carbonated Beverages and Out-of-Hospital Cardiac Arrests of Cardiac Origin in Japan

Background: The consumption of carbonated beverages has been shown to increase the risk of developing metabolic syndrome. The associations between the consumption of carbonated beverages and left arterial dimension or left ventricular mass are believed to be likely related to the greater body weight of carbonated beverage drinkers relative to non-drinkers. Nonetheless, little is known about the association between the consumption of carbonated beverages and out-of-hospital cardiac arrests (OHCAs) in Japan. Methods: We compared the age-adjusted incidence of OHCAs to the expenditures on various beverages per person between 2005 and 2011 in the 47 prefectures of Japan. Patients who suffered from OHCAs of cardiac and non-cardiac origin were enrolled in All-Japan Utstein Registry of the Fire and Disaster Management Agency. The expenditures on various beverages per person in the 47 prefectures in Japan were obtained from data published by the Ministry of Health, Labour and Welfare of Japan. Results: There were 797,422 cases of OHCA in the All-Japan Utstein registry between 2005 and 2011, including 11,831 cases who did not receive resuscitation. Among these 785,591 cases of OHCA, 435,064 (55.4%) were classified as cardiac origin and 350,527 (44.6%) were non-cardiac origin. Non-cardiac origin included cerebrovascular disease, respiratory disease, malignant tumor, and exogenous disease (4.8%, 6.1%, 3.5%, and 18.9%, respectively). The expenditures on carbonated beverages were significantly associated with OHCAs of cardiac origin (r = 0.30, p = 0.04), but not non-cardiac origin (r = -0.03, p = 0.8). Expenditures on other beverages, including green tea, tea, coffee, cocoa, fruit or vegetable juice, fermented milk beverage, milk beverage, and mineral water, were not significantly associated with OHCAs of cardiac origin. Conclusion: Carbonated beverage consumption was significantly and positively associated with OHCAs of cardiac origin in Japan, indicating that beverage habits might play a role in OHCAs of cardiac origin.

Amount of Calcium Elution and Eroded Lesion Depth in Bovine Enamel Derived from Single Short Time Immersion in Carbonated Soft Drink <i>in Vitro</i>

Erosion is one of serious oral health problems among Japanese children. Some dentists argue that brushing just after food/drink intake induces enamel abrasion. Objectives of this study were to evaluate amount of calcium elution from bovine enamel due to single and short immersion into carbonated soft drink, to calculate depth of the eroded lesion, and to determine when to brush teeth after carbonated soft drink intake from the view point of preventing enamel abrasion. Four enamel specimens were made from each of eight bovine teeth. The specimens were covered by quick-cure resin except for enamel surfaces. The four specimens from each bovine tooth were classified into three, six, nine, and 12 minutes immersion (IM3, IM6, IM9, and IM12) groups and immersed separately in five mL of carbonated soft drink. After the immersion, the calcium concentration of the original drink and the drink samples were evaluated using atomic absorption spectrophotometry. The dimension of each enamel specimen was calculated using a planimeter. The amount of eluted calcium per unit area of the enamel specimen into each drink sample was obtained. The depth of the demineralized lesion was obtained by dividing the amount of calcium elution per unit area by the concentration of calcium in enamel and the specific gravity of enamel. The lesion depth of the IM3 group was significantly lower than those in the IM6, IM9, and IM12 groups. The mean lesion depth in the IM12 group which showed the deepest lesion depth was 0.21 μm. As conclusions, the erosive lesion depth due to intake of carbonated soft drink was much shallower than remineralized enamel surface of a white spot lesion which can be repaired in plaque fluid in a short time, suggesting such erosion hardly causes tooth wear, hence it was suggested that brushing teeth just after the intake was recommended.

Measurement of Radioactivity in Carbonated Soft Drinks and Annual Dose Assessment

A set of measurements have been conducted, using gamma spectrometry technique, in order to determine the activity-level in some carbonated soft drinks. The obtained activity is about 0.18 ± 0.07 Bq/l for 137Cs, whereas it is less than 0.13, 0.18 and 4.51 Bq/l respectively for 212Pb, 214Pb and 40K. The total average annual dose is about 3.49, 1.69 and 1.68 μSv/y respectively for 7 - 12, 12 - 17 and >17 years old person leading to a radiological risk about 0.142 for adolescent and adults. The obtained results show no significant radiation dose and radiation hazard on human health due to the consumption of these carbonated soft drinks.

Physico-Chemical and Petrographic Characterization of Carbonated Rocks of Mintom (South-Cameroon) and Their Potential Uses

The characterization of carbonated rocks of Mintom allowed identifying three features (massive limestone, banded limestone and dolomite). Samples taken in these features were subjected to the physico-chemical analyses and to the mechanical tests. The results obtained show a convergence in the mineralogical composition in particular in the calcareous features (smectite, micas and calcite);the dolomite feature being mainly constituted by dolomite associated with the smectite. The chemical composition allows finding contents raised in CaO, in all the samples. However, in the dolomite and the banded limestone, the concentrations in MgO and in SiO2 are also important. The mechanical properties showed a good compression resistance for the massive limestone and the dolomite, the mechanical behavior of the banded limestone being low. The exploitation of these results allows recommending carbonated rocks of Mintom in the production of the clinker, agricultural amendments and in the constructions of the civil engineering.

Strength and deformation characteristics of carbonated reactive magnesia treated silt soil

A series of unconfined compression tests(UCTs) were conducted to investigate the effects of content of reactive magnesia(Mg O) and carbonation time on the engineering properties including apparent characteristics, stress-strain relation, and deformation and strength characteristics of reactive Mg O treated silt soils. The soils treated with reactive Mg O at various contents were subjected to accelerated carbonation for different periods of time and later, UCTs were performed on them. The results demonstrate that the reactive Mg O content and carbonation time have remarkable influences on the aforementioned engineering properties of the soils. It is found that with the increase in reactive Mg O content, the unconfined compressive strength(qu) increases at a given carbonation time(<10 h), whereas the water content and amounts of crack of the soils decrease. A threshold content of reactive Mg O exists at approximately 25% and a critical carbonation time exists at about 10 h for the development of qu. A simple yet practical strength-prediction model, by taking into account two variables of reactive Mg O content and carbonation time, is proposed to estimate qu of carbonated reactive Mg O treated soils. A comparison of the predicated values of qu with the measured ones indicates that the proposed model has satisfactory accuracy.

Chloride resistance of Cr-bearing alloy steels in carbonated concrete pore solutions

The effect of carbonation on the chloride resistance of low-carbon steel and two Cr-bearing alloy steels in simulated concrete pore solutions was investigated.The chloride threshold values of steels were determined on the basis of corrosion potential(Ecorr)and polarization resistance(Rp).Moreover,the chloride-induced corrosion behavior of steels was evaluated using electrochemical impedance spectroscopy,cyclic voltammetry,cathodic potentiodynamic polarization,and scanning electron microscopy/energy dispersive X-ray spectroscopy measurements.Alloy steels have higher chloride resistance than low-carbon steel in carbonated and non-carbonated concrete pore solutions.The chloride resistance of alloy steels improves with increasing Cr content.In addition,the chloride resistance of all steels is negatively affected by the carbonation of concrete pore solution,especially for alloy steel with high Cr content in the presence of high chloride content.

Kinetics of carbonated decomposition of hydrogarnet with different silica saturation coefficients

Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method,which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method.In this study,the effect of the silica saturation coefficient(x)on the carbonation of hydrogarnet was investigated from the kinetic perspective.The results indicated that the carbonation of hydrogarnets with different x values(x=0.27,0.36,0.70,and 0.73)underwent two stages with significantly different rates,and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3.The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and 14.80–34.84 kJ/mol,respectively.Moreover,the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion.

Mechanical Properties and ITZ Microstructure of Recycled Aggregate Concrete Using Carbonated Recycled Coarse Aggregate

The effect of carbonation treatment and mixing method on the mechanical properties and interfacial transition zone（ITZ） properties of recycled aggregate concrete（RAC） was investigated. Properties of recycled concrete aggregate（RCA） were tested firstly. Then, five types of concretes were made and slump of fresh concrete was measured immediately after mixing. Compressive strength and splitting tensile strength of hardened concrete were measured at 28 d. Meanwhile, the microstructure of RAC was analyzed by backscattered electron（BSE） image. It was found that the water absorption ratio of carbonated recycled concrete aggregate（CRCA） was much lower when compared to the untreated RCA. Comparatively, the apparent density of CRCA was not significantly modified. The concrete strength results indicate that the mix CRAC-2 prepared with CRCA by adopting two-stage mixing approach shows the highest compressive strength value compared to the other mixes. The microstructural analysis demonstrate that the mix CRAC-2 has a much denser old ITZ than the untreated RAC because of the chemical reaction between CO2 and the hydration products of RCA. This study confirms that the ITZ microstructure of RAC can be efficiently modified by carbonation treatment of RCA and encourages broadening the application of construction and demolition wastes.

Comparison of properties of traditional and accelerated carbonated solidified/stabilized contaminated soils

The investigation of the long-term performance of solidified/stabilized （S/S） contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four years and sampled at various depths in a controlled manner. The chemical properties （e.g., degree of carbonation （DOC）, pH, electrical conductivity （EC）） and physical properties （e.g., moisture content （MC）, liquid limit CLL）, plastic limit （PL）, plasticity index （PI）） of the samples untreated and treated with the traditional and accelerated carbonated S/S processes were analyzed. Their variations on the depths of the soils were also studied. The result showed that the broad geotechnical properties of the soils, manifested in their PIs, were related to the concentration of the water soluble ions and in particular the free calcium ions. The samples treated with the accelerated carbonation technology （ACT）, and the untreated samples contained limited number of free calcium ions in solutions and consequently interacted with waters in a similar way. Compared with the traditional cement-based S/S technology, e.g., treatment with ordinary portland cement （OPC） or EnvirOceM, ACT caused the increase of the PI of the treated soil and made it more stable during long-term weathering. The PI values for the four soils ascended according to the order： the EnvirOceM soil, the OPC soil, the ACT soil, and the untreated soil while their pH and EC values descended according to the same order.

The Properties of the Carbonated Brick Made of Steel Slag-slaked Lime Mixture

The properties of the carbonated brick made of steel slag-slaked lime mixture such as strength, drying shrinkage, water absorption and soundness were mainly investigated. The experimental results indicate that, after carbonation, the strength of the brick increases, its drying shrinkage reduces, and its soundness becomes eligible. The optimal slaked lime/steel slag（SL/SS） ratio for the carbonated brick is 0.2 and the asprepared brick meets the requirements of the Chinese standard for MU20-grade building bricks, additionally, it also demonstrates prominent environmental benefits. The XRD and pore structure analyses indicate that the excellent properties of this carbonated brick are attributed to the formation of carbonate crystals and the dense structure due to the carbonation.

Chloride diffusion in concrete with carbonated recycled coarse aggregates under biaxial compression

Chloride attack on concrete structures is affected by the complex stress state inside concrete,and the effect of recycled aggregates renders this process more complex.Enhancing the chloride resistance of recycled concrete in a complex environment via carbonization facilitates the popularization and application of recycled concrete and alleviates the greenhouse effect.In this study,the chloride ion diffusion and deformation properties of recycled concrete after carbonization are investigated using a chloride salt load-coupling device.The results obtained demonstrate that the chloride ion diffusivity of recycled concrete first decreases and then increases as the compressive load increases,which is consistent with the behavior of concrete,in that it first undergoes compressive deformation,followed by crack propagation.Carbonation enhances the performance of the recycled aggregates and reduces their porosity,thereby reducing the chloride diffusion coefficient of the recycled concrete under different compressive load combinations.The variation in the chloride ion diffusivity of the carbonized recycled aggregate concrete with the load is consistent with a theoretical formula.

Experimental assessment of hybrid smart carbonated water flooding for carbonate reservoirs

Different methods of enhanced oil recovery have been used to produce trapped oil.One of these methods is carbonated water injection in which CO2 contained water is injected in reservoirs in order to decrease free CO2 injection mobility,increase water viscosity and store/remove produced greenhouse CO2 gas safely.Another enhanced oil recovery method is smart water injection at which the ions in brine are modified in order to make controlled reactions with distributed ions on the surface of rock to cause more hydrocarbon recovery.Therefore,combination of these two methods may also have a great effect on enhancing oil recovery or may result in recovery factor less than each method used alone.In this paper hybrid smart carbonated water injection method is investigated to study its applicability in oil recovery using core flooding setup.The experimental core flooding setup was designed to perform different types of EOR methods for the sake of recovery comparison with the new hybrid method.The effect of both brine content and volume of CO2 is determining in hybrid EOR assessment.The main findings of this work show that the hybrid smart carbonated water results in the highest recovery factor in comparison to the most well-known EOR methods for carbonate cores.

Enabling heterogeneous catalysis to achieve carbon neutrality: Directional catalytic conversion of CO_(2) into carboxylic acids

The increase in anthropogenic carbon dioxide(CO_(2))emissions has exacerbated the deterioration of the global environment,which should be controlled to achieve carbon neutrality.Central to the core goal of achieving carbon neutrality is the utilization of CO_(2) under economic and sustainable conditions.Recently,the strong need for carbon neutrality has led to a proliferation of studies on the direct conversion of CO_(2) into carboxylic acids,which can effectively alleviate CO_(2) emissions and create high-value chemicals.The purpose of this review is to present the application prospects of carboxylic acids and the basic principles of CO_(2) conversion into carboxylic acids through photo-,electric-,and thermal catalysis.Special attention is focused on the regulation strategy of the activity of abundant catalysts at the molecular level,inspiring the preparation of high-performance catalysts.In addition,theoretical calculations,advanced technologies,and numerous typical examples are introduced to elaborate on the corresponding process and influencing factors of catalytic activity.Finally,challenges and prospects are provided for the future development of this field.It is hoped that this review will contribute to a deeper understanding of the conversion of CO_(2) into carboxylic acids and inspire more innovative breakthroughs.