Accelerated Carbonation Curing Research Articles

Utilization of Aluminosilicate Industrial Wastes as Precursors in CO2-Cured Alkali-Activated Precast Concrete Pavement Blocks

This research focuses on the utilization of recently investigated aluminosilicate industrial wastes as precursors to produce non-structural precast alkali-activated concrete pavement blocks. For this purpose, conventional blocks (200 mm × 100 mm × 80 mm) were produced using electric arc furnace slag and municipal solid waste incineration bottom ashes as the sole binders. Portland cement and fly ash blocks were produced as references. The blocks underwent a curing regimen comprising thermal, dry, and carbonation curing stages. Control uncarbonated specimens were subjected to dry curing instead of CO2-based curing to evaluate the influence of carbonation on the blocks’ strength development. The specimens were subsequently examined following EN 1338, which is the European standard for assessing and ensuring the conformity of conventional concrete pavement blocks. The carbonated blocks revealed improved mechanical and physical properties in relation to the uncarbonated ones. All blocks met standard dimensions, showed minimal skid potential (most indicating extremely low potential for slip for reporting unpolished slip resistance values exceeding 75), and had enhanced abrasion resistance due to carbonation, showing 30% and 11% less volume loss due to abrasion for fly ash and bottom ash, respectively. Carbonated blocks performed better than non-carbonated ones, displaying lower water absorption (0.58% and 0.23% less water absorption for bottom ash and slag, respectively) and higher thermal conductivity (20%, 13%, and 8% increase in values for fly ash, slag, and bottom ash, respectively). These results confirm the effectiveness of the accelerated carbonation curing technique in improving the block’s performance. Despite the promising outcomes, further optimization of the alkaline solution and carbonation curing conditions is recommended for future research.

Accelerated carbonation curing of concrete incorporating calcium carbide residue

The synergic effect of accelerated carbonation curing and cement replacement by calcium carbide residue (CCR) on the carbon sequestration potential and performance of concrete was examined. The concrete mixes included 0, 5, 10, and 20 % (by mass) CCR as partial cement replacement and were subjected to different initial air curing durations (0, 4, and 20 h) and subsequent carbonation curing durations (4 and 20 h). The performance was evaluated based on the CO2 uptake, 1-, 7-, and 28-day compressive strengths, and volume of permeable voids. Scanning electron microscopic (SEM) imaging was used to characterize the microstructure of the carbonated concrete. The environmental footprint of concrete produced herein was assessed. The experimental results showed that using CCR enhanced the CO2 uptake of concrete, with 5 and 10 % replacement levels providing superior outcomes in concrete subjected to 4- and 20-h carbonation curing. The compressive strength and a volume of permeable voids improved upon replacing cement with 5 % CCR. Such findings were validated by examining the void space in the SEM micrographs. Furthermore, prolonging the initial air curing and carbonation durations to 20 h each and incorporating 20 % CCR resulted in the highest CO2 uptake and lowest carbon footprint. Among the developed mixes, the most suitable was the mix subjected to 20 h of each initial air curing and carbonation curing with 20 % CCR replacement by mass. Nevertheless, all developed mixes satisfy the minimum strength requirement for concrete masonry unit applications.

A new method for improving the resistance of cement-based materials to carbonic acid water corrosion: Carbonation curing and further water curing

Accelerated carbonation curing has several advantages compared with traditional moisture curing in terms of decreasing the duration time of early curing and improving the mechanical properties, dimensional stability and durability of concrete. This study investigated the effect of accelerated carbonation curing and further water curing on corrosion behavior, corrosion products, and pore structure of cement mortar and paste samples exposed to carbonic acid water corrosion. The results indicate the accelerated carbonation curing reduces corrosion depth and mitigates the decline in compressive strength caused by carbonic acid water corrosion. The accelerated carbonation curing can lead to the decalcification of C-S-H gel, and the formation of a large amount of CaCO3 and silica gel (SiO2·γH2O) on the surface of the C-S-H gel, which play a crucial role in the corrosion resistance of carbonic acid water. CaCO3, firstly, fills pores and optimizes the pore structure, slowing down the diffusion rate of carbonic acid water. Meanwhile, an essential "protective layer" forms on the surface due to abundant CaCO3, effectively preventing further corrosion of internal C-S-H gel, CH, C2S, and C3S. At the later age of corrosion, the carbonic acid water can lead to the decalcification shrinkage of CaCO3, and the deterioration of pore structure, which adversely affects the mechanical properties of cement-based materials.

Experimental investigation into the self-carbonation mechanism of magnesium oxide carbon sequestration foamed concrete

A novel technique involves the preparation of foamed concrete utilizing MgO as a substitute for Portland cement (PC) and CO2 foam in place of air foam. This technique is referred to as “magnesium oxide (MgO) carbon sequestration foamed concrete (MCFC)" that enables self-carbonation of Reactive MgO cement-based concrete under ambient conditions without any accelerated carbonation curing conditions. The developed technology enhances the carbonation efficiency of MgO-based materials by combining a foaming agent with CO2 curing. The even mixing of CO2 foam with MgO, referred to the uniform distribution and incorporation of CO2 throughout the sample, facilitated by the foaming agent, leads to the production of ions within the cement, promoting the carbonation of dissolved Mg2+ ions and the formation of hydrated magnesium hydroxyl carbonates (HMHCs). Eight sample groups were prepared to explore the potential of MCFC in CO2 sequestration. XRD, TG-DTA, and SEM techniques were employed to investigate the mineral phase and carbonation products in MCFC. The pore structure, pore-size distribution, and porosity of MCFC under different curing conditions were investigated using X-ray and NMR. The self-carbonation enabled by CO2 foams improved the microstructure and mechanical performance of MgO-based samples. Notably, the morphology, microstructure, and carbonate content improvements resulted in a significant 100% increase in the 28-day compressive strengths (2 MPa) compared to the control sample cured under ambient conditions.

Carbon dioxide sequestration in mortars with excavated soil: Engineering performances and environmental benefits

Globally, substantial volume of excavated soils is generated during construction and demolition activities, which can be utilized in the manufacturing stabilized earth-based construction materials. Furthermore, increasing amount of CO2 is being released into the environment from growing industrial operations that can sequestered in earth-based materials without compromising the engineering properties. This article attempts to explore the effect of CO2 sequestration through accelerated carbonation curing on engineering properties, micro-structure and phase composition of cement-lime stabilized soil mortars. Lateritic soil (clay content of 42 %) is used to replace 25 % and 50 % of natural sand by mass. The experimental findings demonstrate an increase in CO2 uptake by 15–23 % and 33–40 % due to addition of 25 % and 50 % soil respectively compared to control (0 % soil). Precipitation of meta-stable calcium carbonates majorly contributes to the total CO2 uptake, accounting for 62–69 % and 78–87 % of the carbonates formed in 25 % soil-mortars and 50 % soil mortars. These are substantially higher compared to 40–50 % in the case of control mixes. The mentioned finding is attributed to the formation of additional calcium-silicate-hydrate and calcium-aluminate-hydrate due to clay-lime reaction, that binds CO2 and precipitate meta-stable polymorphs of calcium carbonate. Addition of lime and carbon sequestration are found to substantially enhance 1-day strength of cement-soil and cement-lime-soil mortars by 31–36 %, although no prominent effect at 7-day and 28-day marks are observed. Furthermore, capillary water absorption at 28-day age is reduced by 18–31 % in lime-added cement-soil mortars compared to the ones without lime, that reduces moisture sensitivity of the mortars. Overall, the carbon sequestered mortars demonstrate satisfactory strength (20–37 MPa) and water absorption performance of the stabilized mortars for masonry applications, which will provide a promising means to manufacture low-carbon and more durable construction products.

Synergic effect of metal-organic frameworks and process parameters on the properties of concrete subjected to accelerated carbonation

This study aims to develop a novel concrete that integrates a metal-organic frameworks (MOF) and accelerated carbonation curing to offset the emissions attributed to cement production. A MOF, NH2-MIL-125(Ti), was synthesized to sequester CO2 in concrete through accelerated carbonation curing. Its impact on the concrete properties was assessed while examining various process parameters, including MOF content, initial curing duration, carbonation curing duration, and carbonation curing pressure. The parameters were evaluated through CO2 uptake, phenolphthalein indicator solution, compressive strength, water absorption, and volume of permeable voids. The microstructure of carbonated MOF-incorporating concrete was characterized using powder X-ray diffraction analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. Experimental results showed that the addition of MOF promoted a higher degree of carbonation of cement, especially with a longer initial curing duration and higher pressure. Incorporating up to 6% MOF, by cement mass, in concrete cured for 20 h in open air, followed by 20 h of carbonation curing at a pressure of 1 bar, led to a CO2 uptake of 19%, carbonation depth of 11 mm, and 28-day strength of 46 MPa, water absorption of 4%, and permeable pore voids volume of 11%. Exceeding 6% MOF addition did not improve the uptake or performance. Microstructure characterization highlighted the formation of calcite, aragonite, and calcium silicate hydrate and the consumption of calcium hydroxide. The MOF-incorporating concrete can be used in construction applications to mitigate CO2 emissions while maintaining concrete performance.

Strategies for OPC Paste Carbonation: Relationship between Microstructure, Performance and Net CO2 Balance

Carbon capture storage and utilization is the main technology for reducing CO2 emissions, accounting for 56% of the overall reduction required to achieve the carbon neutrality of concrete by 2050. Different strategies have been explored in cement-based materials towards this end, namely, in concrete. However, the impact on carbonated concrete differs depending on the moment at which cementitious material comes into contact with CO2, either in terms of CO2 uptake or in terms of its lifetime performance. This paper presents three leading strategies that rely on the direct carbonation of a cementitious binder to reduce the carbon footprint. For each strategy, the effect of the carbonation process on the kinetics and microstructure of cementitious paste, the estimation of its carbon capture capability and the application feasibility are discussed. Accelerated carbonation curing is one approach widely studied by academics. However, despite some CO2 capture effectiveness, its industrial processing is still a long way off. A second strategy consists of incorporating CO2 during the mixing process, which has been shown to speed up the hardening reactions of cement. However, this effect is of short term and may negatively affect its long-term performance. Finally, the carbonation of hydrated cement waste is shown to be a very promising strategy that enables the recycling of hydrated cement waste as a supplementary cementitious material which also has a potentially high CO2 uptake. The integrated analysis of the three strategies highlights a wide variability in the reduction of CO2 emissions from 1% to 37% in relation to current emissions, where the best result was achieved using carbonated waste (third strategy) in the production of a concrete subjected to carbonation curing (first strategy).

Long term performance of concrete using accelerated carbonation curing: an effective CCUS technique

The induction of accelerated carbonation curing (ACC) as carbon capture, utilization, and sequestration (CCUS) technique helps in achieving the net zero target. ACC is one of the potential techniques to sequester the CO2 in concrete. However, the usage of ACC in reinforced concrete is still debatable. This paper investigates the effect of ACC on mechanical, permeation, mineralogy, hydration and microstructural characteristics of concrete with the long-term performance of reinforced concrete using linear polarization resistance (LPR) and carbonation depth. In order to study the effect of ACC duration on the properties of concrete, the specimen was subjected to 6, 12, and 24 hours (h) of carbonation curing. The results were compared with conventional water-curing specimens. ACC at 12 h provided the best results for tested properties. The results were varied by statistical analysis using ANOVA and stoichiometry. Based on the best 12-h duration, 2.13 kg of CO2 can be sequestered in 1 m3 (0.89 kg/t) of concrete.

Utilization of magnesium slag to prepare CO2 solidified fiber cement board

Magnesium slag is a solid waste produced during industrial magnesium refining. The large amount of magnesium slag produced each year not only causes environmental pollution, but also poses a risk to human health. This paper proposes the use of magnesium slag as a carbonation binder, to produce a new type of CO2 solidified fiber cement board (CSFCB) by accelerated carbonation curing. The mechanical properties, microstructure, durability, and volumetric stability of CSFCB were investigated, and its environmental benefits were evaluated. The results indicate that, under optimal process conditions, CSFCB can attain a water-saturated flexural strength of more than 14 MPa, a carbonation degree higher than 40%, and a water absorption rate as low as 14.9% after 24 h carbonation curing. Phase assemblage and microstructure analysis attribute the high performance mainly due to the voluminous precipitation of calcium carbonate, and the strong bonding of reinforcing pulp fibers with the matrix. This also leads to the improved freeze-thaw resistance and negligible warping deformation. Furthermore, compared to traditional fiber cement board (TFCB), CSFCB exhibits added benefits of carbon absorption and solid waste valorization by the ecologic assessment. The results of the pilot production of CSFCB show that the production and utilization of CSFCB will significantly reduce environmental pollution.

Performance of Alkali-Activated Slag Concrete Masonry Blocks Subjected to Accelerated Carbonation Curing

This study investigates the effect of accelerated carbonation curing on the carbon sequestration potential, performance, and microstructure of alkali-activated slag mixes representing concrete masonry blocks (CMBs). The carbonation curing process parameters varied, including initial curing duration, carbonation curing duration, and carbonation pressure. Research findings showed that a maximum CO2 uptake of 12.8%, by binder mass, was attained upon exposing concrete to 4 h initial curing and 20 h carbonation curing at a pressure of 5 bars. The compressive strength and water absorption capacity improved with longer initial and carbonation curing durations and higher pressure. Upon subjecting to salt attack, the mass and strength of 28-day concrete samples increased, owing to the formation of Friedel’s salt and Halite. All mixes could be used as non-load-bearing CMB, with a 1-day strength greater than 4.1 MPa. Based on the global warming potential index, the carbon footprint of carbonation-cured, alkali-activated slag concrete masonry units was up to 46% lower than non-carbonation-cured counterparts. Research findings offer valuable information on the production of carbonation-cured, cement-free concrete masonry blocks to replenish natural resources, recycle industrial waste, and mitigate CO2 emissions.

Comparative life cycle environmental assessment of recycled aggregates concrete blocks using accelerated carbonation curing and traditional methods

Accelerated carbonization curing has been a technically feasible alternative to the conventional curing method in the production of recycled aggregate concrete blocks (RACB). However, the environmental impacts of the curing scenarios on production have not yet been studied. Therefore, the paper evaluated the environmental feasibility of curing methods to produce RACB based on the LCA framework. The system boundary from the cradle to the door was selected to compare the overall influence of accelerated carbonation curing methods (pressurized carbonation curing, wet carbonation curing) and traditional curing methods (standard curing, autoclave curing) on the environmental impact. CO2 absorption was calculated by the Kim and Chae carbonation model combined with experimental carbonation depth. Environmental emission calculated from the inventory database was distributed to ten midpoint indicators and three endpoint indicators by the CML 2016 baseline and ReCiPe endpoint method. The distribution of contributions to the environmental impacts of the four production stages (raw material processing stage, raw material transportation stage, block manufacture stage, and block curing stage) was subdivided to facilitate decision-making and improve the management of the block plant. A sensitivity analysis ultimately complements the effect of curing time on the environmental sustainability of RACB production. The results showed that the traditional curing method had a more significant environmental impact, while accelerated carbonization curing had a relatively lower environmental impact. Compared with standard curing, the GWP value of pressurized and wet carbonization curing decreased by 33.3% and 52.8%, respectively. The 1 m3 RACB showed the lowest GWP value of 254.7 kg CO2-eq under wet carbonization curing and the highest GWP value of 539.5 kg CO2-eq under standard curing. The CO2 absorption capacity of −73.0 kg CO2-eq and −99.3 kg CO2-eq was demonstrated by pressurized and wet carbonization curing, respectively. The ranking from all midpoint and endpoint indicators is standard curing > autoclaved curing > pressurized carbonization curing > wet carbonization curing. Contribution analysis based on midpoint indicators showed that the raw material handling stage has the highest percentage contribution. Cement is still the most significant contributor to the environmental impact, followed by significant energy consumption, while water consumption hardly negatively impacts the environment. The results of sensitivity analysis indicate that accelerated carbonation curing (especially wet carbonation curing) is less relevant to the variation of curing time, while conventional curing methods are strongly influenced by curing time.

Thermo-mechanical behavior of cementitious material with partial replacement of Class-II biochar with Accelerated Carbonation Curing (ACC)

Using carbon-neutral materials is a promising way to mitigate the CO2 emissions of the construction industry. Biochar prepared from agricultural waste has a great potential to sequester CO2. This study demonstrates a new sustainable method for preparing biochar from rice husk having class II category as it has less than 60% carbon content and is derived at a temperature of 500 ℃. The prepared biochar was partially replaced in cement paste and cured under a CO2 environment for 7 and 28 d. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) showed that the replacement of biochar promoted cement hydration and mechanical properties. Addition of 3 wt% and 5 wt% biochar increased the compressive strength of the composite by 34.7% and 35.6%, respectively. However, a further addition to 10 wt% biochar reduced the compressive strength by 16.7%. Replacement of up to 5 wt% biochar successfully promoted the carbonation with 10.2% CO2 uptake after 28 d of accelerated CO2 curing. Carbonation of biochar-cement composite substantially improves thermal conductivity, specific heat, and thermal diffusivity compared to control samples at 7 and 28 d. Field Emission Scanning Electron Microscope (FESEM) analysis revealed the numerous cement hydrates which enhance the bond strength after carbonation, and the carbonate densifies the microstructure, considerably enhancing mechanical strength and carbon binding capability. Biochar-cement composites with CO2 could be innovative low-carbon building materials for sustainable engineering applications.

Novel typology of accelerated carbonation curing: using dry and pre-soaked biochar to tune carbon capture and mechanical properties of cementitious mortar

One of the challenges of promoting accelerated carbonation curing (ACC) of concrete as a carbon sequestration strategy is ensuring that carbonation will not deteriorate mechanical strength. This study examined the mechanical strength, water sorptivity and carbonation efficiency of ten types of mortar containing dry or pre-soaked biochar subjected to internal and/or external carbonation. The results obtained enabled a typology of ACC to be proposed, in which the carbon dioxide absorption of mortar containing various types of CO2-dosed biochar ranged between 0.022% and 0.068% per unit dosage hour. In particular, the mortar containing dry biochar dosed with carbon dioxide was the top candidate for concurrently increasing both compressive strength (54.9 MPa) and carbon dioxide absorption (0.055% per unit dosage hour). Mortar containing pre-soaked biochar dosed with carbon dioxide was identified as a strategy that achieved the highest carbonation efficiency (0.068% per unit dosage hour), but it also reduced compressive strength (45.1 MPa). Collectively, the proposed typology offers a useful overview of the different ways by which biochar can be used to tune ACC in mortar, according to any technical constraints and/or intended functions of the carbonated concrete components.Graphical

Synergistic Use of CO2 Pretreatment and Accelerated Carbonation Curing for Maximum Recycling of Steel Slag

Synergistic Use of CO2 Pretreatment and Accelerated Carbonation Curing for Maximum Recycling of Steel Slag

Durability performance of self-compacting concrete produced using CO2 as an admixture

This research investigates the fresh characteristics and durability of self-compacting concrete (SCC) made using CO2 as an admixture. In the existing practice, CO2 is added to concrete mainly through accelerated carbonation curing. That has many limitations, such as low diffusion rate, requirements of the large airtight chamber, and use in precast concrete only. To overcome these limitations, the current study employed a CO2 mineralization approach. As cementitious materials hydrate during mixing, CO2 reacts with it and produces more hydration products. In addition, calcium carbonate particles are formed in situ, filling the minute pores and densifying the SCC matrix. The present research results reveal that a small quantity of CO2 mineralization improves the SCC compressive strength and durability; the best durability is achieved at 0.3% mineralization of CO2 by the weight of the cement used. Compare to normal SCC, a 4.3% higher compressive strength of CO2 mineralized SCC was noticed at 28 days of testing. 0.05 % lowers weight gain and 1.88 % higher compressive strength was noticed in CO2 mineralized SCC at 180 days of 5% sodium sulfate exposure condition. Similarly, the rapid chloride penetration test result shows that 11.35% lesser chloride ions pass from CO2 mineralized SCC compared to normal SCC. The fresh characteristics of the SCC as a result of CO2 mineralization behave similarly to reference SCC with small degradation that is considered acceptable. Hence, thepresent study demonstrates that CO2 can be used beneficially in concrete to enhance its properties and lower CO2 emissions into the atmosphere.

Effect mechanism of steel slag on CO2 capture in hydraulic lime

Steel slag (SS) inhibits the early hydration of cement, limiting its application in cement-based materials. In this study, SS was used to prepare hydraulic lime (HL), and the effect of SS on CO2 capture in HL was investigated. SS inhibited the carbonation of HL in the early stages but promoted carbonation in the later stages. Adding more than 10% SS inhibited the formation of hydration products, and the reduction of hydration products inhibited the carbonation product content, increased the porosity of the hydration mortar, promoted the later stage carbonation rate, and reduced the compressive strength. The carbonation area and captured CO2 content of the mortars in SS-HL increased exponentially with an increasing carbonation curing age. With an increasing SS content, the carbonation area and the degree of CO2 capture decreased then increased after 1 day and after 3 days of accelerated carbonation curing, respectively.

Carbonation of Alkali-Activated Materials: A Review.

This paper presents a literature review on the effects of accelerated carbonation on alkali-activated materials. It attempts to provide a greater understanding of the influence of CO2 curing on the chemical and physical properties of various types of alkali-activated binders used in pastes, mortars, and concrete. Several aspects related to changes in chemistry and mineralogy have been carefully identified and discussed, including depth of CO2 interaction, sequestration, reactions with calcium-based phases (e.g., calcium hydroxide and calcium silicate hydrates and calcium aluminosilicate hydrates), as well as other aspects related to the chemical composition of alkali-activated materials. Emphasis has also been given to physical alterations such as volumetric changes, density, porosity, and other microstructural properties caused by induced carbonation. Moreover, this paper reviews the influence of the accelerated carbonation curing method on the strength development of alkali-activated materials, which has been awarded little attention considering its potential. This curing technique was found to contribute to the strength development mainly through decalcification of the Ca phases existing in the alkali-activated precursor, leading to the formation of CaCO3, which leads to microstructural densification. Interestingly, this curing method seems to have much to offer in terms of mechanical performance, making it an attractive curing solution that can compensate for the loss in performance caused by less efficient alkali-activated binders replacing Portland cement. Optimising the application of such CO2-based curing methods for each of the potential alkali-activated binders is recommended for future studies for maximum microstructural improvement, and thus mechanical enhancement, to make some of the "low-performing binders" adequate Portland cement substitutes.

Property Improvement of Recycled Coarse Aggregate by Accelerated Carbonation Treatment under Different Curing Conditions

Recycled aggregate (RA) made from waste concrete has inferior fundamental properties, i.e., apparent density, water absorption, mass variation, carbonation ratio, etc., compared to those of natural aggregate (NA), severely restricting its application in practical projects. However, using CO2 to accelerate RA carbonation can effectively improve these properties, and this treatment approach can promote energy savings and sustainable development. The accelerated carbonation curing conditions for RA can significantly impact the modification effect of RA. For this purpose, this paper used recycled coarse aggregate (RCA) as a case study. An accelerated carbonation modification treatment experiment for RCA under different accelerated carbonation curing conditions was carried out, and the effects of relative humidity and CO2 concentration on the apparent density, water absorption, moisture content, mass variation and carbonation ratio of RCA under a constant ambient temperature were explored and quantified. The results indicated that the best-accelerated carbonation curing conditions applicable to this paper’s RCA were confirmed as being an environmental temperature of 20 °C and a relative humidity of 70%, as well as a CO2 concentration of 20%. Under these conditions, the apparent density and water absorption of CRCA are approximately 1.04 times and 75.30% higher than those of RCA, and, in addition, the carbonation ratio for RCA under the optimal accelerated carbonation curing conditions is all higher than others, thus improving the properties of RCA to a certain degree. Finally, in this paper, the variation trends of the RCA property indexes in terms of carbonation time treated by the best accelerated carbonation curing conditions are examined, and the time-varying models for the RCA property indexes during the accelerated carbonation are established.

The role of biomass bottom ash in Carbonated Reactive Magnesia Cement (CRMC) for CO2 mineralisation

This work evaluates the incorporation of biomass bottom ashes on Carbonated Reactive Magnesia Cement-based (CRMC) mortars. For this purpose, four mixtures were designed to verify the influence of biomass bottom ash as partial or total sand replacement. The specimens were moulded through static compaction pressure and submitted to an accelerated carbonation curing period of 24 h under controlled conditions. The devised mortars were evaluated through mass, dimension, pH measurements, and compressive strength tests. Furthermore, TG-DTG, SEM, FT-IR, XRD, and MIP analyses were performed to investigate the microstructure of the materials developed in this study. Therefore, the devised mortars reached compressive strength results from 9.9 to 24.5 MPa. The TG-DTG, FT-IR, SEM, and XRD analyses support the formation of HMCs in all mixture designs being their volume carbonated in different degrees. Finally, the use of fine particles of biomass bottom ash collaborated for compressive strength enhancement and higher CO2 uptake degree while larger particles do not.

Effects of nano palm oil fuel ash on hydration of cement under the accelerated carbonation curing

• Accelerated carbonation reaction of cement paste due to the nPOFA. • Conversion of CSH to Ca-modified silica gel and poorly crystalline CaCO 3 . • The synergetic effects of carbonation curing and usage of nPOFA for carbon sequestration. The ultimate goal of usage of supplementary cementitious materials and accelerated carbonation curing in concrete is to reduce the generation of CO 2 . This study firstly investigated the effect of nano Palm Oil Fuel Ash (nPOFA) on the accelerated carbonation curing of cement paste. The results showed that P30 (30% of nPOFA) had larger amounts of Ca-modified silica gel from the decalcification of CSH and calcium carbonate compared to P0 (0% of nPOFA). It might be assumed that high contents of potassium oxide in nPOFA accelerates the ionization of CO 2 and carbonation of calcium silicates and hydration products.