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The Effects of Calcium Carbonate on Sodium Metasilicate-Activated Metakaolin-Based Geopolymer Pastes

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SSRN 2024年

作者： Ren, Jie Dowdy, Nicolas D. Acarturk, B. Cansu Srubar, Wil V. Department of Civil Environmental and Architectural Engineering University of Colorado Boulder 1111 Engineering Drive ECOT 441 UCB 428 BoulderCO80309 United States Materials Science and Engineering Program University of Colorado Boulder 4001 Discovery Drive BoulderCO80303 United States College of Civil Engineering

The influence of calcium carbonate (CaCO3) on the alkali-activation kinetics, microstructure, and compressive strength of alkali-activated metakaolin (MK) geopolymer cements was investigated herein. Experimental results showed that replacing 10-50% of MK with ground CaCO3 particles delayed the acceleration stage of alkali-activation regardless of replacement amount. However, 10% CaCO3 replacement increased the overall degree of reaction and yielded pastes with similar 14- and 28-day compressive strengths compared to the experimental control with no CaCO3 addition. In comparison, 50% CaCO3 replacement led to a lower overall degree of reaction and lower compressive strengths through 28 days of curing. Experimental evidence substantiates that N-A-S-H gel forms in samples containing 0% and 10% CaCO3, while N-(C)-A-S-H gel and/or C-(N)-A-S-H are also present in the binding matrix near CaCO3 particles in samples with higher CaCO3 contents (i.e., 30% and 50%). While the CaCO3 particles were primarily composed of calcite, vaterite, a less stable form of CaCO3, was also evident in the samples containing 30% and 50%, suggesting that the CaCO3 particles were moderately reactive during the alkali-activation. © 2024, The Authors. All rights reserved.

关键词： Calcium carbonate

Contributions of Cleaning Solution Residues to Indoor Organic Surface Films

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ACS ES&T Air

ACS ES&T Air 2024年第2期1卷 129-138页

作者： Rachel O’Brien Emily Heery Catherine Shirilla Sumit Sankhyan Ashley Fowler Marina E. Vance Department of Civil and Environmental Engineering University of Michigan Ann Arbor Michigan 48109 United States Department of Chemistry William & Mary Williamsburg Virginia 23185 United States Department of Mechanical Engineering University of Colorado Boulder 1111 Engineering Drive 427 UCB Boulder Colorado 80309 United States Environmental Engineering Program University of Colorado Boulder 4001 Discovery Drive Boulder Colorado 80309 United States

Indoor surfaces become coated with a thin organic film that plays important roles in indoor chemistry. The sources for these films are important to understand to improve our ability to model and pr...

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The Influence of Synoptic Wind on Coastal Circulation Dynamics

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arXiv

arXiv 2023年

作者： Allouche, Mohammad Bou-Zeid, Elie Iipponen, Juho Department of Civil and Environmental Engineering Princeton University NJ United States Program in Atmospheric and Oceanic Sciences Princeton University NJ United States

Particularly challenging classes of heterogeneous surfaces are ones where strong secondary circulations are generated, potentially dominating the flow dynamics. In this study, we focus on land-sea breeze circulations (LSBs) resulting from surface thermal contrasts in the presence of increasing synoptic pressure forcing. The relative importance and orientation of the thermal and synoptic forcings are measured through two dimensionless parameters: a bulk Richardson number Ri = W*2/Mg2 (Mg is the geostrophic wind magnitude and W* a convective buoyant velocity scale), and the angle α between the shore and geostrophic wind. Large eddy simulations reveal the emergence of various regimes where the dynamics are shown to be asymmetric with respect to α. Along-shore cases result in deep LSBs similar to the quiescent scenario (zero synoptic background), irrespective of the strength of Mg. Across-shore simulations exhibit a circulation cell that decreases in height with increasing synoptic forcing. However, at the highest synoptic winds simulated, the circulation cell is advected away with sea-to-land winds, while a shallow circulation persists for land-to-sea cases. Scaling analysis that relates the internal parameters Qshore (net shore volumetric flux) and qshore (net shore advected heat flux) to the external input parameters Mg and W* results in a succinct model of the shore fluxes that also helps explain the physical implications of the identified LSBs. Finally, the vertical profiles of the shore-normal velocity and shore-advected heat flux are used, with the aid of k-means clustering, to independently classify the LSBs in the (Ri –1, α) regime space diagram (canonical LSB, sea-driven LSB, land-driven LSB, and advected LSB), corroborating our visual categorization. © 2023, CC BY.

关键词： Coastal zones

Ammonia Recovery from Organic Nitrogen in Synthetic Dairy Manure with a Microbial Fuel Cell

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SSRN 2023年

作者： Burns, McKenzie Qin, Mohan Department of Civil and Environmental Engineering University of Wisconsin–Madison MadisonWI53706 United States Environmental Chemistry and Technology Program University of Wisconsin–Madison WI53706 United States

Increasing pressures on the animal and cropland agriculture sectors have led to the realization of problems with animal waste management and ammonia-based fertilizer supply. Bioelectrochemical systems (BES) are a new-age technology that offer a way to address these problems. Microbial fuel cells (MFCs), one type of BES, are traditionally used for electricity generation from microbial degradation of organic matters, but can also be used to recover nutrients from wastes simultaneous with treatment. This research investigates an MFC for ammonia recovery from the organic nitrogen (orgN) fraction of synthetic dairy manure, using the simple amino acid glycine as the orgN source. We investigate five different synthetic manure compositions to determine their effect on MFC performance, and found minimal sacrifices in performance under orgN conditions when compared to the base condition without orgN. The MFC achieved greater than 90% COD removal in all orgN conditions. Nitrogen (N) removal efficiencies of between 40% and 60% were achieved in orgN conditions, indicating that organic nitrogen can be used as the substrate for ammonia mineralization and further recovery as fertilizer. Furthermore, we found the MFC to be largely populated by electrogenic organisms from the phyla Bacteroidota, Firmicutes, Proteobacteria, and Halobacterota, with organisms in both Bacteroidota and Firmicutes capable of N mineralization present. Lastly, we found that in conditions where orgN is scarce and the only N source provided, microbes preferentially degrade organic matter from other dead organisms, especially as a N source, instead of available but scarce complex organic N. This increases the concentration of N in the MFC system and introduces important operational constraints for MFCs operated for ammonia recovery from orgN. © 2023, The Authors. All rights reserved.

关键词： Recovery

How to Make Green Building Certification & Rating Systems More Pandemic-Sustainable? 6th

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How to Make Green Building Certification & Rating Systems Mo...

6th Asia Conference on Environment and Sustainable Development, ACESD 2021

作者： Tleuken, A. Tokazhanov, G. Guney, M. Turkyilmaz, A. Karaca, F. Department of Civil and Environmental Engineering School of Engineering and Digital Sciences Nazarbayev University 53 Kabanbay Batyr Ave. Nur-Sultan010000 Kazakhstan Nazarbayev University Nur-Sultan010000 Kazakhstan Master of Engineering Management Program Nazarbayev University Nur-Sultan010000 Kazakhstan

ISBN: (纸本)9789811917035

The present study demonstrates a gap analysis (in response to the COVID-19 pandemic) of the best known widely used green building certification and rating systems (GBC&RSs): LEED, WELL, BREEAM, CASBEE. These systems have been analyzed for their missing responses according to a list of selected pandemic-sustainable indicators. The gap levels for each system have been calculated and then compared to each other. Among four GBC&RSs, BREEAM exhibited the smallest gap score, whereas LEED and WELL held the largest gap scores. Following these results, we suggest courses of action for each system to remove the gaps that will result in achieving a better response under pandemic conditions. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Coronavirus

Sustainable Stabilization of Sandy Soils Using Steel Slag and Biopolymer Cellulose

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SSRN 2025年

作者： Mugula, Julius Nakayenga, Joyce Kido, Ryunosuke GuhaRay, Anasua Hata, Toshiro Civil and Environmental Engineering Program Hiroshima University 1-4-1 Kagamiyama Higashi Hiroshima Hiroshima City739-8527 Japan Department of Civil Engineering BITS Pilani Hyderabad Campus Jawahar Nagar Kapra Mandal Telangana Secunderabad500078 India Hiroshima University Japan

Steel slag, a by-product of the steel-making industry, offers potential for soil stabilization but remains underutilized in sandy soils due to challenges such as slow strength development, low water retention, particle segregation, and bleeding. Cellulose, a plant-based biopolymer, enhances soil water retention and may improve the performance of steel slag-treated *** study investigated the stabilization of Masado granite and Toyoura silica sands using steel slag and two forms of unhydrolyzed cellulose: cellulose powder (CP) and carboxymethyl cellulose (CMC). Sands were treated with steel slag at varying contents (0%, 10%, 15%, 30%, and 50%) to identify the optimal dosage and the most suitable sand based on unconfined compressive strength (UCS) and pozzolanic reactivity over 3, 7, 14, and 28 days. CP and CMC were added at 0%, 0.25%, 0.5%, 0.75%, and 1% to evaluate their effects on the UCS, flowability, compaction, mineralogy, and microstructure. The findings established 30% steel slag as the optimal dosage, enhancing UCS by 99.05%. Masado granite sand exhibited the highest UCS (558.85 kPa), outperforming Toyoura silica sand (34 kPa) due to better pozzolanic reactivity. Incorporating 0.5% cellulose further improved strength, with CMC and CP increasing UCS by 53.29% and 49.23%, respectively, through gel thread and fibrous network formation. These optimized composites reduced cement-related carbon emissions by 2.5% per kilometer of highway embankments, demonstrating their viability as sustainable and eco-friendly construction materials. © 2025, The Authors. All rights reserved.

关键词： Silica sand

Waste Plastics and Microplastics in Africa: Negative Impacts and Opportunities

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Waste Plastics and Microplastics in Africa: Negative Impacts...

2021 AIChE Annual Meeting

作者： Abdellatif, Gaber Mahmoud, Ahmed S. Peters, Robert W. Mostafa, Mohamed K. Environmental Engineering Program Zewail City of Science and Technology Giza Egypt Badr Egypt Department of Civil Construction and Environmental Engineering University of Alabama at Birmingham BirminghamAL United States Cairo Egypt

ISBN: (纸本)9781713852834

Waste plastics and microplastic pollution are two of the most pressing global issues during the past few decades, since the beginning of plastic mass production either for direct use in packaging and plastic products, or for indirect use for plastic dependent industries. The issue is even more problematic for Africa due to the late catch-up of the industrialization and urbanization boom for most of the African countries, which is usually accompanied with intensive production, consumption, and waste generation of plastics. Moreover, the growing population, cheaper costs of plastic products, and minor importance of environmental conservation in developing countries in Africa are making it an easy choice to expand in plastic use and wastage. African countries have imported about 172 Mton of polymers and plastics valued between 1990 and 2017, and the per capita consumption of plastic in Africa in 2015 was 16 kg/capita/year. While plastic is very important for populations, inappropriate disposal or treatment of plastic waste can introduce hazardous and toxic materials to our environment and ecosystem like microplastics that usually consists of persistent polymers, and other toxic plastic additives like plasticizers, antioxidants, and stabilizers. Moreover, 79% of plastic waste worldwide is being discharged to landfills or open environments. That's why mixed plastic waste was listed as hazardous waste in the Basel Convention. Therefore, this paper provides a review of the life cycle of plastics in. Production and importing will be discussed, important usages will also be elaborated, and most importantly plastic waste production and current plastic waste management techniques will be evaluated and highlighted, and drawbacks of current strategies will be addressed. Finally, recommendations about better waste management strategies will be provided. © 2021 American Institute of Chemical Engineers. All rights reserved.

关键词： Plastic products

Nucleation effects of coccoliths in portland cement

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Matter 2025年

作者： Beatty, Danielle N. Srubar, Wil V. Materials Science and Engineering Program University of Colorado Boulder 4001 Discovery Drive UCB 027 BoulderCO80303 United States Department of Civil Environmental and Architectural Engineering University of Colorado Boulder 1111 Engineering Drive ECOT 441 UCB 428 BoulderCO80309 United States

This work explores the use of photosynthesized coccoliths (intricate CaCO3 particles) as a nucleation agent or cement replacement in portland cement paste. First, coccoliths were produced and harvested from the marine microalgae Emiliania huxleyi and the particle size, morphology, and mineralogy were characterized. Then, the nucleation effects of E. huxleyi coccoliths as seeding agent (0.5, 1, 3, or 5 wt % additions) and limestone filler (5 and 15 wt % cement replacements) were studied using isothermal conduction calorimetry and compressive strength testing. The results were compared with five commercially available CaCO3 sources used as nucleation agents and fillers. While the high surface area of coccoliths (12.22 m2/g) enhanced water demand, it also enhanced nucleation during cement hydration without accelerating hydration, leading to enhanced early-age strength without detriments to 28-day strength. Results highlight a potential carbon reduction strategy, namely employing photosynthesis as a method of mineral admixture production, for the cement and concrete industry. © 2025 Elsevier Inc.

关键词： Portland cement

Ecogenorisk: Developing a Computational Ecological Risk Assessment Tool for Synthetic Biology

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SSRN 2023年

作者： Ulanova, Anna Mansfeldt, Cresten University of Colorado Boulder Department of Civil Environmental and Architectural Engineering 1111 Engineering Drive BoulderCO80309 United States University of Colorado Boulder Environmental Engineering Program 4001 Discovery Drive BoulderCO80309 United States

The expanding field of synthetic biology (synbio) supports new opportunities in the design of targeted bioproducts or modified microorganisms. However, this rapid development of synbio products raises concerns surrounding likely risks when the modified organism contaminates unintended environments. Additionally, new tools are required to screen for these risks during the design phase. EcoGenoRisk is a computational risk assessment tool designed to evaluate the potential environmental risks posed by synthetic organisms. The overall goal of this tool is evaluating the environmental risk associated with synbio organisms establishing a population where genetically similar organisms reside. The first module of the tool, NicheOverlap, aims to identify genetically similar microorganisms to the synthetic biology organism and evaluate the risks posed by analyzing potential competition, mutualism, and inhibition between the organisms. Here, we compiled and analyzed 520 Archaeal and 32,828 Bacterial complete assembly genomes to analyze the tools specificity and accuracy in analyzing input genomes, as well as to characterize the enzymatic capabilities of different taxonomic lineages. Additionally, ecological relationships were analyzed to determine which would result in the greatest ecological disruption. Competition was found to be the primary mode of ecological disruption, resulting in unequal sharing of resources. Furthermore, high genetic similarity between organisms indicated an increase of competition for resources. Although the tool was effective in assessing synthetic organism risk, limitations, and vulnerabilities, such as large variability in scoring for genetically mildly different genomes and reliance on databases with update latencies were identified. Overall, EcoGenoRisk is a valuable tool for evaluating the environmental risks associated with synthetic organisms, but further improvements and validation studies are necessary for real-world applications. © 2023, Th

关键词： Software design