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Low-Carbon Supplementary Cementitious Materials (SCMs) from Waste Stamp Sands
No full textAddressing the critical challenge of reducing CO₂ emissions in the cement industry involves utilizing waste stamp sands as a sustainable source for supplementary cementitious materials (SCMs). Stamp sands, abundant in Michigan\u27s Upper Peninsula, contain silicate minerals that can be converted into high-performance SCMs, enabling reductions in clinker usage and overall carbon emissions [1].Therefore, this study investigated the potential of waste stamp sands from Lake Superior (Gay, MI) as SCMs through calcination. Compositional analysis revealed that the sands contained silicate minerals such as albite, diopside, and anorthite, making them suitable for pozzolanic activity [2, 3]. Calcination at 800–900°C transformed these crystalline phases into reactive amorphous silica and metastable calcium carbonate, enhancing their reactivity [4, 5]. Mechanical tests demonstrated substantial improvements in mortar strength and hydration when 10–20% calcined stamp sands replaced cement. Hydration studies indicated increased early reactivity, while SEM and EDS analyses confirmed the formation of calcium-silicate-hydrate (C-S-H) phases and refined pore microstructures. XRD and FT-IR results validated structural changes in silicate minerals post-calcination. These findings demonstrated that calcined stamp sands effectively improved the mechanical properties of cementitious materials, offering a low-carbon solution for sustainable construction and reducing environmental impacts from mining waste
Evaluating the Risk of Internal Sulfate Attack in Concrete Containing High-SO₃ Coal Ashes: A Path Toward Low-Carbon Concrete
No full textHigh-SO₃ fly ashes (FA), including reclaimed landfilled and ponded ashes, present a significant opportunity to decarbonize concrete through clinker substitution. However, their use is restricted by ASTM C618, which limits SO₃ content to 5.0% due to concerns over internal sulfate attack. This study evaluates the expansion risk in concrete containing high-SO₃ fly ashes (both real and doped) and investigates the underlying expansion mechanisms. The results demonstrate that fly ashes exceeding 5.0% SO₃ can be safely used if they pass the ASTM C1038 lime water expansion test at the intended dosage. Specifically, fly ashes with up to 12.0% SO₃ at 20% replacement levels did not exceed the 0.02% expansion limit, as shown in Figure 1. Furthermore, total SO₃ content in the binder (cement + fly ash) was found to be a more reliable predictor of expansion risk than fly ash SO₃ content alone. A maximum limit of 5.0% SO₃ in the binder is recommended to mitigate expansion risk, as supported by Figure 2. To further investigate sulfate-induced expansion, quantitative X-ray diffraction (QXRD) and pore solution analysis were performed on a paste containing 5.6% SO₃ in the binder. The results revealed that ettringite formation—the main driver of expansion—persists until sulfate in the pore solution is depleted, even though solid gypsum depletes within 24 hours (Figure 3). These findings indicate that sulfate availability in the pore solution, rather than cement C₃A content, controls expansion, supporting the safe use of high-SO₃ fly ashes under appropriate dosage conditions
Aqueous Carbonation for CO2 Curing of Construction Materials
No full textThis paper reviews CO2 curing process for construction materials, focusing on conventional and aqueous carbonation methods. While conventional CO2 curing utilizes gaseous CO2 to accelerate early-age strength development, aqueous carbonation introduces CO2-dissolved water as an advanced alternative. The latter approach, particularly when combined with amine solutions, offers improved application efficiency without requiring specialized curing chambers. The applications of aqueous carbonation extend beyond traditional curing to include surface treatment for enhanced durability, recycled aggregate strengthening, and geopolymer concrete production. These developments represent significant progress toward sustainable concrete production while contributing to carbon utilization in construction industry
Using CO2-Embedded Coal and MSWI Fly Ashes as Sustainable Alternative SCMs: A Feasibility Study
No full textThis study explores using carbonated coal fly ash (CCFA) and municipal solid waste incineration (MSWI) fly ash (CMFA) as supplementary cementitious materials. Carbonation treatment typically increase surface area and enable remarkable CO₂ uptake, with CMFA showing improved reactivity compared to uncarbonated ashes. Compressive strength tests revealed that CMFA outperformed uncarbonated MFA, while CCFA-incorporated mortar showed lower strength than uncarbonated counterpart. All blends consisting of Portland-limestone cement and carbonated ashes appear to meet the requirements of ASTM C1157. It suggests carbonated coal and MSWI fly ashes are viable alternative SCMs for sustainable concrete production
Characterizing CO2 in Cementitious Materials with QXRD and TGA and Remote Fiber Optic Raman Probe
No full textThe urgent need for producing sustainable cementitious materials has led to increased interest in using carbon-negative technology to enhance sustainability. In this regard, measuring the amount of CO2 is one essential issue. This study evaluated the potentials and the limitation of Thermal Gravimetric Analysis (TGA), Quantitative X-ray Diffraction (QXRD), and Optic Raman Probe in characterizing the CO2 in cementitious material with different dosages. traditional methods like TGA are accurate for measuring CO2 but need destructive or extensive sample preparation. This study proposes using a remote fiber optic Raman spectroscopy probe for non-destructive, in situ CO2 analysis in cementitious materials. Raman spectroscopy offers detailed molecular and structural information, enabling direct observation of CO2 uptake in the cement matrix under various conditions
Optimizing Thermoelectric Efficiency in Cementitious Nanocomposites via Hybrid SWCNT/NCF Reinforcement
No full textCement-based materials with thermoelectric functionalities offer new opportunities for harvesting waste heat from civil infrastructure. While carbon nanomaterials have been shown to enhance the electrical conductivity of cementitious composites, achieving efficient thermoelectric energy conversion requires simultaneously controlling the thermal properties while preserving the electrical properties. In this study, insulating cellulose nanofibrils (NCFs) are combined with superconducting single-walled carbon nanotubes (SWCNTs) to develop nano-engineered cementitious materials capable of converting thermal gradients into electrical energy. Results show that the hybrid SWCNT/NCF mortars exhibited a Seebeck coefficient up to 4083.61 μV/K and ZT of 0.46 while maintaining high electrical conductivity of 126.42 S/m and a reduced thermal conductivity of 0.84 W/m·K
Assessment of Textured Epoxy-Coated Rebars in Concrete for Chloride Induced Corrosion
No full textTextured-Epoxy coated rebar (TEC) differs from conventional Epoxy coated rebar (ECR) due to its rougher exterior surface – which aims to reduce cracking in concrete and development length. However, no studies have investigated the long-term corrosion response behavior of both TEC and ECR when subjected to service-level bridge deck displacement criteria. This study utilizes Non-Destructive Testing techniques such as Half-Cell Potential (HCP), Ground Penetrating Radar (GPR), Ultrasonic Pulse Velocity (UPV), and Linear Polarization Resistance (LPR) to characterize the corrosion response behavior of service-level stressed TEC and ECR reinforced concrete samples subjected to a realistic chloride environment
Dome Construction Experiment at EXPO 2025 Utilizing Carbon Negative Concrete Technology
No full textConcrete is a challenging material for achieving a low-carbon society because of the large amount of CO₂ emissions during cement production. Technologies have been developed to separate, recover and reuse CO₂ as a resource. We adopted the following two types of environmentally friendly concrete to reduce CO₂ emissions in the construction of the Expo dome: ECM (Energy CO₂ Minimum) concrete and CO₂-SUICOM (CO₂ Storage Utilization for Infrastructure by Concrete Materials). ECM concrete contains high content granulated blast furnace slag (GGBS) to reduce CO₂ emissions by reducing cement content 1). CO₂-SUICOM can achieve negative CCO₂ emissions by absorbing CO₂ into γ-C2S contained as an admixture through carbonation curing 2). Previously, the curing required a special curing chamber in a factory. Thus, CO₂-SUICOM application was limited to precast components. The aim of this study is to develop a method for carbonation curing of CO₂-SUICOM on-site and to evaluate the CO₂ emission reduction effects of environmentally friendly concrete
Effects of incorporating colloidal nano-silica and metakaolin on mitigating alkali-silica reaction
No full textAlkali-silica reaction (ASR) is a critical durability concern, as it can reduce the service life of structures and increase carbon emissions due to the need for early repair or replacement. In this study, the effects of incorporating colloidal nano-silica (CNS) and metakaolin (MK) to mitigate ASR have been investigated. The results show that the incorporation of CNS and MK effectively suppressed the ASR in mortar. As the CNS content increases from 4% to 6%, ASR induced length expansion decreases by 58%. On day 16, the CH content in the sample containing 10% MK and 2% CNS was 48% lower than that of the reference sample. Moreover, on day 16 following the alkali-silica reaction, the compressive strength of both the MCNS-6% and MMK10CNS-2% samples were approximately 45% higher than that of the reference sample