Accelerated Carbonation Curing Research Articles

Effectiveness and microstructure change of alkali-activated materials during accelerated carbonation curing

Alkali-activated materials (AAMs) have two major environmental benefits compared to traditional cement-based materials: reducing greenhouse gas emissions and recycling industrial by-products. To evaluate the possibility of using AAMs for well construction in carbon capture, utilization and storage (CCUS) projects, the carbonation resistance performance of AAMs was investigated under accelerated carbonation conditions. The results showed that the loss ratios of the AAMs compressive strength were 89.75% and 88.20% in the gas and liquid phase carbonation environments during the first 3 days, respectively. The structural damage in the AAMs was mainly caused by the leakage of Ca2+ from the calcium silicate hydrate (C-S-H) phase of the matrix, converting it into crystalline calcium carbonate after CO2 attack. From 7 days of the start of carbonation, the cumulative pore volumes of the AAMs samples increased from 0.97 to 5.02 ml/g and from 0.97 to 4.37 ml/g in the gas and liquid phase carbonation environments, respectively. The presented work indicates that under accelerated carbonation conditions, the rate of destruction of AAMs is too rapid for such material to be used for the construction of CCUS wells.

Strength Development and Products Evolution of β-C2S and γ-C3S Induced by Accelerated Carbonation Curing

Strength Development and Products Evolution of β-C2S and γ-C3S Induced by Accelerated Carbonation Curing

Intensive Ways of Producing Carbonate Curing Building Materials Based on Lime Secondary Raw Materials

The article is dedicated to the research and development of intensive methods for curing products by capturing and binding CO2. It aims to improve and increase the productivity of technologies for the production of artificially carbonated building materials and products. Soda production wastes, limestone dust and finely dispersed limestone dust were used as the research objects. Secondary raw materials have been investigated using modern methods of phase composition and granulometry test. Intensive methods of production of accelerated carbonation of systems consisting of soda wastes were tested using multi-parameter optimization methods. The effects of recycled lime materials on the strength and hydrophysical properties of the obtained material were determined. The secondary raw materials effect depended on the composition of the raw mixture, molding conditions, CO2 concentration applied to the carbonate curing chamber, and the duration of exposure to environments with high CO2 content. It was found that the most effective way of providing accelerated carbonation curing of construction materials and products is a combined carbonation method, combining the principles of dynamic and static methods. It was concluded that the optimal CO2 concentration in the gas-air mixtures used for carbonate curing is 30%–40%.

Accelerated carbonation of C2SH based dense concrete

In this work the possibility of producing a CO2 hardened concrete where the binder is a calcium silicate hydrate instead of anhydrous silicates was investigated and the technological parameters for obtaining calcite based products, combining Ca2(HSiO4)(OH) (α-C2SH) hydrothermal synthesis and accelerated carbonation curing were presented. α-C2SH was synthesized in a stirred suspension (water to solid ratio 10, 100 rpm) after 16 h at 200 °C from lime-opoka (silica-calcite sedimentary rock) mixture with molar ratio CaO/SiO2 = 2.0. Pressed cylindrical samples from synthesized binder and its mixtures with sand were carbonated in the CO2 environment at 1.5 MPa and at 45 °C from 8 to 48 h. It was shown that α-C2SH is, in fact, a binder that hardens in a carbon dioxide atmosphere. Compressive strength of the samples carbonated for 8 h was ~10 MPa and with extended curing, reached ~35 MPa and ~60 MPa after 24 and 48 h, respectively. By XRD and STA it was found that most of the α-C2SH sample carbonates within the first 8 h of curing. Amount of CaCO3 continues to grow gradually but steadily for up to 48 h. SEM and 29Si MAS NMR indicated that the compressive strength development is rather more reliant on the calcite crystal growth than silica gel polymerization. Concrete products from binder/sand mixture (1:3 by mass) with a compressive strength of ~25 MPa can be produced when carbonation is performed at 1.5 MPa CO2 pressure, 45 °C, and 24 h duration. α-C2SH binder, compared to Ordinary Portland cement, has a significantly lower negative impact on the environment due to lower amounts of calcareous raw materials and the elimination of high-temperature combustion.

A comprehensive investigation on application of microsilica and rice straw ash in rigid pavement

• Rice straw ash (RSA) particles are acicular and hydrophilic in nature. • Up to 10% replacement of OPC by RSA and by microsilica (MS) is possible in mortar cubes. • MS is more effective than RSA in improving the mechanical strengths of concrete. • The admixing of MS and RSA significantly enhances the durability properties of concrete. • The admixing of 10% RSA reduces the slab thickness of rigid pavement by 11%. This study investigated the potential of rice straw ash (RSA) (produced from open-air burning of rice straw) and microsilica (MS) as a pozzolan in rigid pavements. Proportions of RSA (5%–30%), MS (2.5%–10%) and combination of RSA (5%, 10%) + MS (5%, 7.5%) by weight of OPC in the paste and mortar were studied. Various tests like normal consistency, setting time, soundness and X-ray diffraction (XRD) analysis were performed on the cementitious paste. It was observed that the admixing of MS did not affect the setting times and soundness of the cement paste but increased the normal consistency while admixing of RSA remarkably increased all of them. It was also found that OPC can be replaced by RSA up to 10% and by MS up to 7.5% in mortar without any loss of compressive strength. In the assessment of mechanical strengths of concrete, it was found that RSA and MS increase various strengths of concrete up to 7% and up to 24%, respectively. Furthermore, these results were validated by XRD and Scanning electron microscope (SEM) analysis. In the evaluation of durability properties of concrete, it was observed that MS and RSA significantly increase the defense mechanism of concrete to water absorption, chloride ion penetration, acid attack and accelerated carbonation curing (ACC). The design thickness of the concrete slab of the selective concrete mixes was computed as per structural design in accordance with IRC 58:2015. The cost comparison was made on the basis of the total cost of 1 m 3 of concrete and the total cost of constructing 1 km of 4 lane National Highway (NH) (one-way carriageway). The admixing of 10% RSA reduces the slab thickness by 11%, cost of 1 m 3 of concrete by 3% and cost of constructing NH by 14%.

Enhancement of cured cement using environmental waste: particleboards incorporating nano slag

AbstractIndustrial waste is constantly increasing, so measures must be taken to recycle it in more practical and environmentally friendly ways. The aim of this study was to investigate the suitability of sawdust wasted particles for the production of cement bonded particleboards, and to enhance their compatibility with cement by using physical pretreatment processes, addition of nano slag and accelerated carbonation curing. All tests were carried out with different manufacturing parameters: sawdust/cement: (20%, 30% and 40%), treated and untreated wood, CO2curing and the addition of nano slag. Experiments were performed to assess the mechanical properties of produced particleboards such as density (D), water absorption (WA), thickness swelling (TS), bending strength (BS), and microstructural properties of the cement particleboards. For treated sawdust, the outcomes demonstrated an enhancement in the mechanical and microstructural characteristics of produced cement bonded particleboards by using the accelerated CO2curing method for sawdust particleboards. According to Scanning Electron Microscopy (SEM) micrographs, part of the carbonate crystals was found to be diffused into the cell walls and cavities and were found to protrude from sawdust surfaces.

Effect of accelerated carbonation curing on near surface properties of concrete

Accelerated carbonation curing (ACC) is one of the emerging techniques to sequester CO2 in concrete. The present study focuses on assessing the near surface properties of concrete subjected to ACC. Freshly cast concrete was subjected to ACC for a period of 6 hours after an initial preconditioning of 2 hours and was followed by water spray till 3 days. Thermogravimetric analysis (TGA) and X-Ray Diffraction (XRD) analysis revealed presence of CaCO3 and increased quantity of CSH gel in near surface of ACC concrete. The findings of XRD and TGA were also confirmed by Scanning Electron Microscopy which exhibited a densification of microstructure due to precipitation of CaCO3 in voids. Mechanical properties and permeation properties of both bulk concrete and near surface concrete were assessed and results were compared with traditional water curing. Compressive strength and abrasion resistance of concrete was found to increase by 30% at the age of 3 days in ACC concrete. Water absorption, sorptivity, chloride permeability and carbonation depth decreased in case of carbonation cured concrete, showing a reduction in permeability of concrete surface. The effect of ACC was more prominent on near surface properties than on bulk properties at later ages and the same were confirmed by performing analysis of variance.

ИНТЕНСИВНЫЕ СПОСОБЫ ПОЛУЧЕНИЯ СТРОИТЕЛЬНЫХ МАТЕРИАЛОВ КАРБОНАТНОГО ТВЕРДЕНИЯ НА ОСНОВЕ ИЗВЕСТКОВОГО ВТОРИЧНОГО СЫРЬЯ

the article is dedicated to the research and development of intensive methods for curing products by capturing and binding CO2. It aims to improve and increase the productivity of technologies for the production of artificially carbonated building materials and products. Soda production wastes, limestone dust and finely dispersed limestone dust were used as the research objects. Secondary raw materials have been investigated using modern methods of phase composition and granulometry test. Intensive methods of production of accelerated carbonation of systems consisting of soda wastes were tested using multi-parameter optimization methods. The effects of recycled lime materials on the strength and hydrophysical properties of the obtained material were determined. The secondary raw materials effect depended on the composition of the raw mixture, molding conditions, CO2 concentration applied to the carbonate curing chamber, and the duration of exposure to environments with high CO2 content. It was found that the most effective way of providing accelerated carbonation curing of construction materials and products is a combined carbonation method, combining the principles of dynamic and static methods. It was concluded that the optimal CO2 concentration in the gas-air mixtures used for carbonate curing is 30%–40%.

Investigation on the effects of acidic environment and accelerated carbonation on concrete admixed with rice straw ash and microsilica

In this research, the effects of the acidic environment and accelerated carbonation curing (ACC) on concrete admixed with rice straw ash (RSA), microsilica (MS) and combination of both were evaluated. The loss of mass and compressive strength of concrete admixed with RSA and MS were observed at 28 and 365 days of water curing followed by 30 days of immersion in two acidic solutions of 2.5% concentration, i.e., hydrochloric (HCl) and sulphuric (H2SO4) acid. The least loss of mass and compressive strength under acidic environment were observed in concrete admixed with a combination of 10% RSA and 5% MS (mix R2M3). The percentage loss of compressive strength (compared to strength at 58 days of water curing) and percentage loss of mass (compared to initial mass before acidic immersion) of mix R2M3 at 28 days of water curing were 3.69% and 2.19% respectively under HCl immersion and 1.81% and 1.27% respectively under H2SO4 immersion. The corrosive impact of HCl on concrete was higher as compared to H2SO4. The characterization of concrete mixtures after acidic immersion was performed using XRD and SEM analysis. The mechanical strength and carbonation depth of concrete admixed with RSA and MS were observed at 28 days of combined curing (14 days of water curing, 14 days of ACC). The maximum increase in the strength of concrete at 28 days of combined curing as compared to 28 days of water curing was found in mix R2M3. Also, the carbonation depth was highest in mix R2M3 (17 mm).

Mechanical properties, durability characteristics and shrinkage of plain cement and fly ash concretes subjected to accelerated carbonation curing

The paper presents an experimental study on assessment of the effect of accelerated carbonation curing (ACC) on the performance of two concrete mixtures having the same mixture proportions but different cementitious materials (plain-cement and fly-ash-blended-cement). Different sets of specimens were cast utilising both concrete mixtures and were then subjected to ACC for ten hours at a constant pressure of 414 kPa (60 psi). After exposing the specimens to ACC, they were tested for weight gain, carbonation depth, compressive and tensile strengths, modulus of elasticity, water penetration depth, rapid chloride permeability, shrinkage, SEM and XRD. ACC of the concrete specimens for ten hours resulted in a significant weight gain with less than 2 mm of carbonation depth. Both mixtures gained compressive strength above 20 MPa after ten hours of ACC. The strength increased further when ACC-treated specimens were exposed to air, with a significant increase up to seven days for plain-cement concrete and up to 28 days for fly-ash-blended-cement concrete. Compared to reference moist-cured concretes, the ACC-treated concretes were found to exhibit a slightly lower long-term strength (15% for plain-cement and 5% for fly-ash-concrete). However, the overall performance of the ACC-treated concrete mixtures was comparable with the respective moist-cured concrete mixtures.

Influence of accelerated carbonation curing on the properties of self-compacting concrete mixtures containing different mineral fillers

This paper presents a study on the effects of accelerated carbonation curing (ACC) on performance of self-compacting concrete (SCC) mixtures prepared using limestone powder (LSP) alone and blend of limestone powder and silica fume (SF) as mineral fillers. Specimens cast using both SCC mixtures were subjected to ACC that consisted of exposing specimens to CO2 for 10 hours under a constant pressure of 414 kPa. ACC-treated specimens were tested for evaluating effects of ACC on properties of SCC mixtures in terms of CO2 uptake, mechanical and durability properties, morphology, and mineralogy. Test results indicate that the ACC-treatment substantially enhanced the properties of both SCC mixtures. Strength of ACC-treated concrete specimens can be improved further by exposing them to air for a period of first 7 days of the ACC-treatment. ACC-treatment of LSP-SF-C was more effective than that for LSP-C. Properties of ACC-treated SCC mixtures were comparable with that of the same mixtures subjected to moist-curing for 7 days except drying shrinkage, which was higher for ACC-treated specimens than the moist-cured specimens. However, shrinkage of ACC-treated specimens after 7 days was within the permissible limit in case of LSP-C whereas 7-day shrinkage for LSP-SF-C exceeded the permissible limit of 500 µm.

Parameter influence on the rankinite binder paste and mortar accelerated carbonation curing

This paper presents a study based on accelerated carbonation curing of low-lime non-hydraulic calcium silicate—rankinite (3CaO·2SiO2 or C3S2)—binder paste and mortar. Rankinite hardening process involves a reaction with gaseous CO2 in the presence of moisture, resulting in the formation of calcium carbonate and Ca-modified silica gel. The carbonation process of this type of binder depends on many features, among which CO2 pressure, duration, and temperature influence were investigated. Thermogravimetric analysis was performed to quantify the amount of calcium carbonates formed after the carbonation reaction, which were later used to calculate the degree of reaction, thus indicating the process efficiency. XRD and FTIR analysis were conducted to determine the prevailing mineral composition after the curing. Based on experimental results, the mineral composition of carbonated rankinite binder consisted of three polymorphs of calcium carbonate, such as calcite, vaterite, and aragonite, together with Ca-modified silica gel. However, the only polymorph of calcium carbonate observed in the mortar samples was calcite. According to the TGA data, the highest carbonation degree reached by paste samples was less than 40%. Nonetheless, the significant differences observed in the XRD curves, led to a conclusion, that pastes and mortars do not undergo the same path of carbonation reaction, indicating that aggregates, i.e., sand (quartz), has a major impact on the formation and polymorphism of calcium carbonate,in mortars potentially supporting calcite, rather than other polymorph formation.

Determination of CO2 capture during accelerated carbonation of engineered cementitious composite pastes by thermogravimetry

The concerns about greenhouse gas emissions have triggered investigations among the scientific community. The accelerated carbonation curing has been used as a tool to capture CO2 at early stages of cement-based material fabrication. In a previous study, the authors quantified the amount of CO2 captured in portland cement pastes by thermal analysis, at high relative humidity precure conditions. In the present work, the authors quantified the amount of CO2 captured in binary pastes derived from engineered cementitious composites (ECC), a family of composites worldwide used, whose one of their features is the precure at low relative humidity conditions. Two types of ECC pastes (1.2 and 2.2) were submitted to 4 h and 24 h of accelerated carbonation after 24 h of initial hydration. Using thermogravimetry and derivative thermogravimetry, the amounts of captured CO2 and respective carbonation degrees were quantified. The results showed that ECC paste 1.2 presented the highest values of captured CO2 and carbonation degree, considering all reactive components. In contrast, ECC paste 2.2 presented the highest values of these two parameters, when considering only portland cement as reactive component. For both pastes, the hydration degrees of the carbonated samples were higher than those of the non-carbonated references, indicating that in the used operating conditions, carbonation enhances ECC paste hydration.

Mathematical modeling of accelerated carbonation curing of Portland cement paste at early age

Accelerated carbonation curing is considered as a promising method to improve mechanical properties and durability of cement-based materials and it also provides a potential for reducing carbon emission. In this paper, a partial differential mathematical model was developed for the coupling behavior of cement hydration and carbonation reaction of both clinker minerals and hydration products when cement paste is exposed to an accelerated carbonation curing at early age. The numerical simulations show that tricalcium silicate is the major reactant for both hydration and carbonation of early age Portland cement paste. The modeling prediction of porosity, carbonation efficiency and pH value of cement paste was verified by measurement results from accelerated carbonation curing test. The prediction values behaved more close to the experimental results with the longer curing age. Dimensionless analysis was performed to figure out the effects of different carbonation mechanisms. Based on the relationship between Thiele modulus and carbonation efficiency, it was found that early age accelerated carbonation curing is a diffusion limiting process initially and then turns into a rate limiting process as the carbonation proceeds. It was also demonstrated that carbonation depth and rate of early age Portland cement paste are mainly controlled by contents of tricalcium silicate and calcium hydroxide while water to binder ratio is kept constant. Therefore, accelerated carbonation curing process of Portland cement paste can be theoretically predicted using this model and influences of mineral admixtures should be further investigated.

Properties of coal gangue-Portland cement mixture with carbonation

To promote the recycling of self-ignited coal gangue (CG) as a partial substitute for Portland cement (PC) and reduce carbon footprint of fossil fuel, carbonation curing was applied to PC-CG blend pastes as a novel strength enhancement method. Compressive strength, drying shrinkage and chloride ion permeability of PC-CG mixtures with or without carbonation curing were investigated and related mechanisms were demonstrated by X-ray diffraction (XRD), 29Si solid-state nuclear magnetic resonance spectroscopy (NMR), thermogravimetry-differential thermal analysis (TG-DTA), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and back scattered electron imaging (BSE) measurements. Results showed that carbonation curing behaves a better improvement effect on compressive strength of PC-CG pastes with the higher incorporation of CG. The accelerated carbonation curing can improve drying shrinkage and chloride ion penetration resistance of cement paste specimen due to the refinement of pore structure. The captured CO2 content reached around 10% of PC-CG blend by weight with this carbonation curing. On the other hand, up to 20% CG can be recycled to replace PC without sacrifice of strength. Therefore, this technology presents a great potential in both sequestration of carbon dioxide and recycling of coal gangue.

CO₂ Uptake of Carbonation-Cured Cement Blended with Ground Volcanic Ash.

Accelerated carbonation curing (ACC) as well as partial replacement of cement with natural minerals are examples of many previous approaches, which aimed to produce cementitious products with better properties and environmental amicabilities. In this regard, the present study investigates CO2 uptake of carbonation-cured cement blended with ground Saudi Arabian volcanic ash (VA). Paste samples with cement replacement of 20%, 30%, 40%, and 50% by mass were prepared and carbonation-cured after initial curing of 24 h. A compressive strength test, X-ray diffractometry (XRD), and thermogravimetry were performed. Although pozzolanic reaction of VA hardly occurred, unlike other pozzolana in blended cement, the results revealed that incorporation of VA as a supplementary cementitious material significantly enhanced the compressive strength and diffusion of CO2 in the matrix. This increased the CO2 uptake capacity of cement, reducing the net CO2 emission upon carbonation curing.

Development of reactive MgO-based Engineered Cementitious Composite (ECC) through accelerated carbonation curing

The use of reactive magnesium oxide (MgO) is widely recognized in carbonated concrete formulations associated with permanent sequestration of CO2. Engineered Cementitious Composite (ECC) is an advanced fiber reinforced cement-based composite with high tensile ductility and intrinsically tight crack width. In this paper, we investigate an alternative binary binding system for ECC: reactive MgO and fly ash cured with an accelerated carbonation process. Compressive strength, density, carbonation depth, tensile performance and crack pattern of the carbonated reactive MgO-based ECC were investigated at various curing ages. In addition, the CO2 uptake and materials sustainability, in terms of energy consumption, net CO2 emission and cost of the newly developed ECC were assessed. The objective of this research is to further advance the application of reactive MgO and utilization of CO2 in the construction industry through novel ECC material. It was observed that carbonation curing densifies the binding system, thus leading to an increase in both compressive and first cracking tensile strengths of ECC. The tensile strain capacity of the carbonated reactive MgO-based ECC achieved up to 6% with an average crack width below 60 μm after 1-day carbonation. Compared to conventional ECC (M45) and concrete, the 1-day carbonated reactive MgO-based ECC could reduce the net CO2 emission by 65% and 45%, respectively. It is concluded that environmental and technical benefits could be simultaneously achieved for the 1-day carbonated reactive MgO-based ECC incorporated with 50% fly ash. The findings of this research shed light on further applications of reactive MgO cement in the precast industry.

Carbonation characteristics of γ-dicalcium silicate for low-carbon building material

γ-Dicalcium silicate (γ-C2S) is characterized by its high carbonation reactivity and has the potential to be utilized as a construction material with the added benefit of CO2 sequestration. The present work addresses the characteristics of pressure-molded γ-C2S samples subjected to accelerated carbonation curing, including the developments in microstructure, carbonation degree and mechanical strength. The results indicate that the mechanical strength and surface density of carbonated γ-C2S block correlate well with its carbonation degree, which is attributed to the generation of more voluminous carbonation products. This strengthens the structure and densifies the matrix. The carbonation products include calcite as the primary morphology and aragonite as the minor phase, and amorphous Ca-modified silica gel formed by coordinated SiO4 tetrahedrons. Conductivity and ion concentration measurement elucidates the accelerated Ca2+ ion dissolution in the presence of CO2 is the reason for the high carbonation reactivity of γ-C2S. A conceptual model of carbonation process is proposed based on the distribution of Ca-modified silica gel and calcium carbonates. Additionally, the ecological evaluation demonstrates that γ-C2S would hopefully reduce 40% of the CO2 emissions compared to ordinary cement, which opens up a new area of a novel low-carbon construction material.

Accelerated carbonation curing of cement mortars containing cement kiln dust: An effective way of CO2 sequestration and carbon footprint reduction

Accelerated Carbonation curing (ACC) is an innovative curing procedure for precast concrete units, which results in sequestration of the carbon dioxide gas and its conversion into stable products. The effect of carbonation curing on mortar mixes incorporating cement kiln dust (CKD) as partial replacement of cement has been investigated in the present study. Carbonation curing was carried out for 12 h, followed by either sealed bag curing or water spray curing for 3 days. The effect of carbonation curing was studied in terms of compressive strength, porosity and pH of the mix, along with SEM to study the resultant morphology. It was observed that ACC led to better early age strength and lower porosity as compared to water cured mortars with at least 20% increase in the strength for each mix. The later age strength decreased slightly by ACC due to water loss, but could be compensated by adopting subsequent water spray. The microstructure analysis showed presence of C-S-H gel and CaCO3 for the carbonated mortars, contributing to the additional strength and reduced porosity. Stoichiometric analysis of the control mix at 3 days of casting also confirmed that carbonation curing enhances the compressive strength and decreases porosity of the mix. It was observed that the finer particle size of CKD particles and presence of alkali in CKD further promotes the carbonation reaction, and hence led to large improvement in the properties of the resultant mix.

Mechanical properties and rapid chloride permeability of carbonated concrete containing reactive MgO

Concrete containing reactive MgO can obtain superior mechanical properties to conventional concrete when subjected to accelerated carbonation curing. This study aims to evaluate the influence of r-MgO replacement levels and accelerated carbonation (CO2 concentration of 99%) curing on the mechanical properties and rapid chloride permeability of concrete containing reactive MgO. Concrete cylinders with r-MgO replacement levels of 10%, 30%, 50% 70% and 90% were studied. Experimental results reveal that carbonation curing improves the mechanical properties of reactive MgO concrete compared to uncarbonated specimens, especially during the first three days of carbonation exposure. Influence of accelerated carbonation on concrete specimens with different r-MgO replacement levels, yields the formation of carbonation products, which diminishes the pore volume and affects the rapid chloride permeability. The rapid chloride permeability of concrete is influenced by the decreases in the overall porosity, the conductivity of pore solution and the connectivity of pore structure due to carbonation.