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The Effectiveness of Pumice as a Supplementary Cementitious Material in High Performance Self-Consolidating Concrete
No full textThe primary focus of the experimental research was to evaluate the effectiveness of pumice as a supplementary cementitious material to offset the cement’s carbon footprint within high performance Self-Consolidating Concrete. Two grades of supplementary cementitious material Pumice (Hess NCS-3 and Hess NDS325) were evaluated during the experimental testing, which were compared against Metakaolin and conventional SelfConsolidating Concrete. The experimental research focused on workability, 7-day, and 28-day compressive strength testing. Initial testing was conducted on 0%, 5%, 10%, and 15% replacement alternatives within each mix design to arrive at the optimum percentage of replacement with cement. The mixture proportion was further refined to achieve SelfConsolidating Concrete. The results indicated that NCS-3 Pumice outperformed Metakaolin mixes. Based upon the above findings, it was concluded that NCS-3 Pumice can be used as an effective alternative supplementary cementitious material to Metakaolin for use in high performance Self-Consolidating Concrete
Exploring Use of Biochar from Different Feedstock as Cement Replacement in Cementitious Composites
No full textThe construction industry is a major contributor to global carbon emissions, with cement production alone responsible for significant greenhouse gas outputs. To address this challenge, biochar, a carbon-rich material derived from biomass through pyrolysis, has emerged as a potential supplementary cementitious material (SCM). This study examines the impact of biochar feedstock types (rice husk, hardwood, and softwood) and particle sizes (\u3c20 μm, 53–149 μm, and 149–300 μm) on the performance of cementitious composites. The biochar materials were comprehensively characterized using Fourier Transform Infrared Spectroscopy (FTIR) to analyze their chemical structure and functional groups, X-ray Fluorescence (XRF) spectrometry to determine their chemical composition, and Scanning Electron Microscopy (SEM) to evaluate surface morphology and porosity. Isothermal calorimetry tests assessed the hydration behavior of cement pastes with 5%, 10%, and 20% biochar replacement, monitoring heat flow and cumulative heat release over 78 hours. Additionally, compressive strength tests evaluated the mechanical properties of biochar-incorporated composites, flow table tests examined workability, and thermal conductivity tests assessed the insulating properties of the resulting materials
Rice Straw Ash as a Sustainable Cementitious Binder: Investigations into Pretreatment and Performance
No full textAs part of its sustainable development goals, India has been promoting biomass-to-energy projects to convert agricultural waste into renewable energy and reduce pollution from the open burning of residues. Rice straw-fuelled power plants in northern India generate large quantities of rice straw ash (RSA) as a by-product. RSA has probable use as a supplementary cementitious material (SCM), but there is limited literature. This study aimed to characterise RSA from three different power plants and investigate its feasibility as an SCM. Analysis revealed that RSA contains silica but has a larger proportion of Potassium Chloride (KCl) contributing to a low strength activity index (S.A.I). A washing pretreatment process demonstrated high efficiency in removing the salts and significantly improved its S.A.I indicating excellent pozzolanic activity and potential for utilization as an SCM. Moreover, the wastewater collected from the washing process yielded crystalline KCl, which can be recycled
Mechano-Carbonation of Mineral and Construction Waste Streams: Manufacturing High-Performance Cement Replacements through Advanced CO2 Capture and Utilization
No full textSCM production is far from reaching the levels demanded by industry, with the US relying heavily on fly ash and slag imports to meet this requirement. To address this challenge, we have developed a novel method, referred here to as mechano-carbonation, that utilizes CO₂ during simultaneous milling to manufacture supplementary cementitious materials (SCMs) from abundant volcanic rocks, namely basalt, as well as concrete waste. For basalt, this innovative process accelerates the natural formation of carbonic acid during processing, enabling the creation of pozzolanic silica gels that enhance the reactivity of basalt by 4.5-fold. This presentation will also demonstrate that the formed silica gels not only improve reactivity but also agglomerate into larger particle sizes—up to 1,000 microns—significantly reducing water demand in concrete mixtures. In concrete waste, mechano- carbonation achieves a maximum 34.5 wt% carbonation. This inert filler, comprised primarily of limestone, when combined with pozzolanic carbonated basalt, represents the potential of a new ternary cement blend capable of CO2 storing nearly 10.7 wt% of their mass. Combining these two resources within novel mechano-carbonation processes accelerates CO2 sequestration and produces domestic SCMs and CO2-dense fillers. Thus, our findings here offer a viable pathway to overcoming current SCM shortages and enabling mass storage of CO2 emissions in novel cement replacements
Perovskite materials for photocatalytic reduction of CO2
No full textPerovskite photocatalysts have emerged as promising candidates for carbon dioxide (CO2) reduction due to their outstanding light absorption properties, efficient charge separation, and tunable band structures. Reported research explored the pathways for optimization of the perovskite structures, surface modifications, and doping strategies to enhance the efficiency of CO2 conversion. This research was focused on translating laboratory synthesis into practical applications such as the use of perovskites as coatings on construction materials, improving the materials\u27 resistance to environmental conditions and degradation over time and contribute to effective conversion of carbon dioxide into products with potential use. Further optimization of perovskite coatings will facilitate their integration into sustainable construction materials. Therefore, the use of photocatalytic perovskite materials in for CO2 reduction has a great potential to address climate change by converting CO2 into valuable products
Advancing Characterization of Cementitious Systems via Raman Imaging
No full textThe drive for sustainability within the cement industry has resulted in the formulation of complex low-carbon cements that show considerable variation in their mineralogical phases, chemical compositions, and particle sizes. These differences can impact the workability, strength, and durability of concrete. Accurately characterizing these properties is challenging and requires a combination of techniques such as microscopy, spectroscopy, and diffraction. Raman imaging is particularly valuable for investigating the entire lifecycle of cement, covering everything from anhydrous cements to hydration and long-term durability. Here, we present its capability to analyze the phase composition of Ordinary Portland Cement (OPC) and Calcium Sulfoaluminate (CSA) cement. We also showcase how Raman imaging can assess the carbonation front in the cementitious system and map the products of alkali-silica reactions (ASR) in mortar samples. This contributes critical insights into the mechanisms of concrete degradation. This positions Raman imaging as a complementary method to electron imaging, facilitating a thorough concrete characterization
Practical Implementation of Internally Cured Concrete Using Superabsorbent Polymers
No full textThis study investigates the practical implementation of internally cured plain and slag cement concrete using superabsorbent polymers (SAPs) through a comprehensive field trial. The objective was to develop strategies to successfully deliver and disperse SAP in concrete, evaluate the internal curing performance of SAP in concrete mixtures containing Type IL cement, slag-cement and colloidal nanosilica and evaluate fresh properties, strength development and durability performance of SAP-modified concrete mixes in real-world applications. The incorporation of SAPs aims to enhance internal curing, reduce shrinkage, and improve the long-term performance of concrete structures. Six concrete mixtures were evaluated with Type IL cement, 30% wt. slag cement replacement, 0.15% SAP by weight of cement, and nanosilica (4 oz/cwt) at a constant w/c ratio of 0.44. Comprehensive characterization was conducted to evaluate workability, air content, compressive strength (7, 28, 56, 90, 365 days) and flexural (at 4 days-driven by opening to traffic requirements), durability (rate of water absorption, drying shrinkage, scaling resistance, chloride penetration depth, and resistivity), and hydration kinetics. The study highlights that incorporating SAP into concrete affects its workability, sustains hydration, and enhances durability
A thermodynamic perspective on reinforcement corrosion in concretes produced with low-clinker blended binders
No full textConcrete produced with blended binders with low clinker content, while having a reduced carbon footprint, pose additional challenges with respect to reinforcement corrosion. As the portland limestone cement is replacing ordinary portland cement, the utilization of conventional supplementary cementitious materials (SCM) has become the norm, and various types of alternative SCM are emerging, the focus has shifted toward the performance of concretes produced with low-clinker blended binders. While the synergetic reactions among clinker, limestone and SCM could provide significant benefits to concrete by reducing porosity, pore connectivity and transport coefficients, hence improving various mechanical and durability properties, they can also make reinforcing steel more vulnerable to corrosion. The corrosion-related factors that can be negatively affected in low-clinker systems comprise the chemistry of the pore solution including its pH, alkali content, and electrical resistivity; hydrated phase composition, including C-(A)-S-H content and types and calcium hydroxide content; pH buffer capacity; chemical and physical binding of alkalis and chloride. In this presentation, thermodynamic calculations are used to provide details on these challenges
Sustainability of Additively Manufactured Cement-based Housing: What\u27s our next move?
No full textAdditive manufacturing of housing has rapidly grown into a nascent industry with numerous demonstration projects recently proving the technological viability of the approach. Goals for the technology, however, are not limited to business ventures that compete in the traditional housing market. Rather, some builders and activists advocate for the technology as a potential key to solving the housing crisis in the US and abroad; though, questions regarding the scalability of economy, environmental impacts and socio-political implications still revolve around the concept. This work focuses on the techno-economics of scale for construction of housing as well as suggests what our next move is to further enable the sustainable implementation in the low-cost, adequate housing domain
Enhanced shape stability of flowable mortar through CO2 injection for 3D concrete printing application
No full textThis study explores the direct injection of CO2 into the 3D printer head during the printing process, enabling real-time control of yield stress evolution in flowable mixtures. CO2 concentrations ranging from 0.5% to 1.4% by cement weight were tested by varying injection times. CO2 injection reduced slump flow of mortar from 250 to 100 mm, as reflected in the decreased width and increased height of printed layers. Mortar with 0.5% CO2 maintained flowability but experienced shape collapse during layer stacking, while higher CO2 concentrations led to nozzle blockages