Natural Sand Research Articles

Nonlinear Analysis of Steel Fiber Reinforced Recycled Aggregate Concrete under Compression, Tension, and Elevated Temperatures

In this study, we report on experiments conducted to determine the compressive behaviour of steel fibre reinforced-recycled coarse aggregate concrete (SFRCAC). Many researchers are interested in exploring the utilize of recycled aggregate in concrete for its potential to reduce environmental impact. By using recycled materials in place of natural ones, Recycled Aggregate Concrete (RAC) represents a novel environmentally friendly construction material. Processing waste concrete with a high proportion of building waste yields recycled aggregates. Natural sand & gravel reserves have been drastically depleted, and natural resources used, as a result of the expansion of the construction sector. Fire damage caused by spalling is a major issue when considering the use of such concrete in construction. SFRAC could help with this. In this research, we provide the outcomes of an investigational study into the compressive properties, particularly the compressive strength, of SFRAC cylinders subjected to extreme temperatures. Compressive mechanical characteristics of concrete were studied as a function of temperature (room temperature, 200 ℃, 400 ℃, & 600 ℃) & steel fibre volume percentage (0%, 0.5%, 1%, 1.5%). Adding steel fibres to RAC that has been heated at high temperatures greatly improves its ductility & cracking behaviour, making it more appropriate for usage in building construction since it lessens the likelihood of spalling.

Arbuscular Mycorrhizal Fungi and Soil Fungi Associated with Uniola paniculata L. (Sea Oats) on Restored and Natural Sand Dunes on the Georgia Coast, U.S.A.

Arbuscular Mycorrhizal Fungi and Soil Fungi Associated with Uniola paniculata L. (Sea Oats) on Restored and Natural Sand Dunes on the Georgia Coast, U.S.A.

Possibilities of replacing natural sand in concrete

This study explores the potential of using fine recycled aggregate (FRA) to replace natural sand in concrete production. The research was divided into two parts. In the first part, natural aggregate’s complete fine fraction (0‑4 mm) was replaced with FRA in conventional concrete for two strength classes. In the second part, individual fine components of high-performance concrete (HPC) were substituted with a similar fraction of fine recycled HPC and concrete aggregate. The physical and mechanical properties of these mixtures with recycled aggregate were evaluated against reference mixtures that contained only natural aggregate, following European standards. Results showed that while most of the concrete and HPC mixtures with recycled aggregate showed slight decreases in properties compared to the reference mixes, the most significant reduction in mechanical properties was observed in the flexural tensile strength of the concrete mixture with FRA, which decreased by over 50 %. The absorption by immersion increased by up to 85 %. The deterioration in properties must be considered during the design stage and only used in applications where it will not affect the functionality of the structures.

Performance of Sustainable Green Concrete Incorporating Quarry Dust and Ferronickel Slag as Fine Aggregate.

This paper presents a study on the combined use of two by-products, namely quarry dust (QD) and ferronickel slag (FNS), as a full substitute for natural sand to improve the greenness of concrete production. Quarry dust was used in increments of 25% to a maximum of 75% substitution, where nickel slag was used as the remaining proportion of fine aggregate. All the combinations of quarry dust and nickel slag were found to be compliant with AS 2758.1 and they showed notably better grading than 100% sand. In this research, standard concrete tests, such as the slump test for fresh concrete, and compression, tensile and shrinkage tests for hardened concrete, were conducted. Scanning electron microscopy and X-ray diffraction analysis were also conducted for microstructural investigation. The results concluded that the combinations of quarry dust and nickel slag in concrete as a whole substitution of sand provide similar results for these properties. Specifically, 25% quarry dust with 75% nickel slag proved to be the most promising alternative to sand, with compressive and splitting tensile strengths of 62 and 4.29 MPa, respectively, which were 16% and 20% higher than those of the control mix. Also, lower drying shrinkage was observed for this combination compared to the control mix. The higher strength is attributed to the rough texture and angular shape of both quarry dust and nickel slag providing a better mechanical interlocking. The validity of this result has also been confirmed through image analysis of micrographs from various specimens. In microstructural investigations, specimens with QD and FNS exhibited fewer voids and a more compact surface compared to the control specimen. This shows the potential for further research into the use of quarry dust and nickel slag in the production of green concrete.

Experimental Investigations on Mineral Admixtures and Steel Fibers in High Strength Concrete

In the process of manufacturing of concrete sand is the most commonly used fine aggregate. The main sources for the natural sand are river beds. These characteristic assets are getting depleted because of over abuse and defilement by chemicals and waste from nearby industries. The waste generated from the demolition of existing structures for various reasons causes great concern and ecological issues. In this project our main objective is to study the influence of partial replacement of F.A with recycled fine aggregate and to compare it with the compressive strength and workability of high strength M60 concrete. We are also trying to replace the various percentages of recycled fine aggregate to study the tendency of the Characteristic strength of concrete.

Gas permeability characteristics of granite-manufactured sand concrete and its numerical simulation using NMR-MIP modified method

Natural sand resources are becoming increasingly scarce with the rapid development of infrastructure. Therefore, manufactured sand usage is inevitable. However, the significant differences in granite powder content between manufactured- and natural sand have a remarkable impact on the pore structure and permeability of cement-based materials, which are crucial for material durability. In this work, several granite powder dosages (0–32 %) of granite-manufactured sand were considered for preparing manufactured sand concrete, and a suitable physical filling model was chosen to quantify the material particle filling for characterizing the overall pore-filling effect. Mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) were used to examine the pore structure of the specimens. The quasi-stationary flow method was used to test the gas permeability of concrete. Finally, a random hierarchical bundle model using the NMR-MIP method is proposed to predict the gas permeability of cementitious materials based on their pore size distribution. The results show that granite-manufactured sand and an appropriate amount (i.e., 8 %) of granite powder can improve the filling effect and anti-permeability performance of concrete. There is a good correlation between the pore structure parameters and gas permeability, where the physico-mathematical relationships can be modeled. The maximum relative difference between the predicted and experimental values of the random tube bundle model was reduced to 30.93 % using the NMR-MIP method compared to 70.87 % with the traditional MIP method.

Pull-out response of a geogrid buried in recycled sands

Recycled construction and demolition waste (RCDW) has demonstrated geotechnical properties that encourage it to be used in reinforced soil structures (RSS) with geosynthetics. However, the interaction between RCDW and reinforcements needs to be better understood, given its importance for design. This paper presents a qualitative study on the interaction between geogrid and recycled sands by means of pull-out tests performed on small equipment. Tests with the same degree of compaction and a geogrid buried in different types of recycled and natural sands (for comparison purposes) were performed. The characterisation of the materials was carried out in the laboratory and the variability of their geotechnical properties was evaluated. In addition, fill material moisture content was investigated as another potential factor influencing soil-geogrid interface shear. The results of the pull-out tests demonstrated the specific influences of the factors investigated. The comparative study showed that recycled sands can be suitable materials to be used as backfill in geosynthetic reinforced soil structures, meeting physical, mechanical and environmental requirements for this kind of work.

Combined application of CDWs as precursors and aggregates in geopolymer composites: A comprehensive rheological analysis

The study of rheological characterization of construction and demolition waste (CDW)-based geopolymeric materials has gained interest due to digital innovation in construction and the increased focus on sustainable materials. Understanding the rheological behavior of these materials is essential due to their rapid geopolymeric reaction kinetics and viscosity behavior. This study investigated the impact of various CDW-based fine recycled aggregates, including crushed concrete aggregates (CRC), crushed ceramic-tile aggregates (CTA), and crushed brick aggregates (CBA), on the rheological behavior of geopolymer mortars (GPMs). Natural sand (NSA) was utilized as a reference for comparison purposes. In addition to CDW-aggregates, the GPMs were also made from optimized CDW-based precursors of brick waste powder (BP), ceramic-tile waste powder (TP), or concrete waste powder (CP). As a result, twelve different GPMs were considered, each containing 100 % individual CRC, CTA, and CBA fine aggregates, blended with BP, TP, and CP precursors. The study evaluated the relationship between the design variable of SiO2/Al2O3 molar ratio as well as the packing densities (PD) of GPM systems and their rheological characteristics, such as flow, apparent and plastic viscosity, yield and shear stresses, thixotropy and shear strains employing the compressible packing method. The results indicate that all GPMs possess shear-thinning or pseudoplastic characteristics. Enhanced SiO2/Al2O3 molar ratio generally resulted in increased rheological parameters. However, using TP as a precursor and CBA as fine aggregates in GPM matrices led to significant enhancement in rheological parameters due to the higher specific surface area of TP and the greater irregularity, convexity, and absorption capacity of CBA particles. Notably, although the enhanced non-colloidal frictional interactions and colloidal flocculation of CRC, CTA, and CBA resulted in reduced flow tendency of GPMs, they have been found to improve the thixotropy during the initial geopolymeric gelation stage.

Effects of stone powder on microstructure of manufactured-sand concrete and its gas permeability

With the development of infrastructure construction, natural sand resources have become increasingly scarce, and the use of manufactured sand has become inevitable. The unique stone powder in manufactured sand could significantly influent the concrete performance. To characterize the stone powder, a physical filling model was used to quantify the particle grading buildup. Isothermal calorimetry and thermogravimetric analysis determined the corresponding chemical activities. Subsequently, non-destructive testing flow methods were designed, referred to as nuclear magnetic resonance (NMR) and hydrostatic balance (HB), to test the pore structure, and a quasi-stationary flow method was used to test the gas permeability of the manufactured sand concrete. Finally, a random hierarchical bundle model using the NMR-HB method was proposed to predict the gas permeability of concrete based on the pore size distribution. The results showed that a moderate amount of stone powder could reduce the heat of hydration, increase the hydration products, improve the filling effect, and decrease gas permeability. A certain fineness of the stone powder could increase the heat of hydration, increase the hydration products, compact the pores from 4.5 to 50 nm, reduce the filling effect, and increase gas permeability. The maximum relative difference between the predicted and experimental gas permeability values of the random tube bundle model was reduced to 34.38 % using the NMR-HB method, whereas this value was 70.87 % using the mercury intrusion porosimetry (MIP) method.

Regulating sulfur migration and transformation in low water-binder ratio cementitious system incorporating phosphogypsum aggregate: Environmentally friendly clean materials

The paper aims to clarify the regulation mechanism of sulfur migration and transformation in a low water-binder ratio system incorporating phosphogypsum aggregate (LWC-PG). Firstly, the combination of S-containing adhesive material and phosphate gypsum aggregate can reduce the migration of sulfate ions (SO42−) in the phosphate gypsum aggregate. The reaction mechanism and macro and micro properties of LWC-PG are characterized by universal testing machine, low field nuclear magnetic field, isothermal calorimeter, XRD diffractometer, scanning electron microscope and nano-indentation. The results show that the calcium sulfoaluminate cementitious system (CSA) is compatible with PG. The results show that CSA is compatible with PG, and the 28d strength of 80 % phosphogypsum is 83.4 MPa, which can maintain the required strength for high-performance concrete. Secondly, the sulfides in PG react with C4A6S in CSA, resulting in the formation of ettringite that coats the surface of the C–S–H gel, thereby retarding the hydration rate of the slurry. However, due to the presence of phosphate gypsum aggregate, the reaction continues, enhancing the hydration of sulfate cement. Moreover, the interfacial transition zone between the PG and matrix exhibits a strong bond and shows no significant signs of deterioration. Lastly, when using 80 % phosphogypsum aggregate instead of natural sand and gravel to produce 100 m3 of concrete, 42 t of phosphogypsum aggregate can be used, which reduces the consumption of natural sand and gravel by 61.4 t, decreases energy consumption by 3070 MJ, reduces CO2 emissions by 178.06 kg, SO2 emissions by 0.37 kg, NOX emissions by 0.25 kg, and dust emissions by 0.087 kg. Life cycle evaluation demonstrates that the production of LWC-PG is associated with low carbon emissions and environmental friendliness, which significantly reduces environmental burden. This is of significant research importance for solid waste management and energy-saving and carbon reduction efforts.

Sustainable Application of Pyrolytic Oxygen Furnace Slag in Cement-Stabilized Macadam: Volume Stability, Mechanical Properties, and Environmental Impact

As an industrial waste, basic oxygen furnace (BOF) slag is an ideal substitute for natural rubble and sand. However, its potential instability of volume restricts the application of the BOF slag in engineering. This study aims at investigating the volume stability and mechanical properties of BOF slag and its application as an aggregate in cement-stabilized macadam. As part of this research, the physicochemical properties, especially the volume stability, of two types of BOF slags and andesite were first studied. Then, mechanical properties, volume stability, and an environment analysis are used to evaluate the application of pyrolytic BOF slag in cement-stabilized macadam. The experimental results show that different types of BOF slags have similar thermal expansion coefficients, which are higher than andesite. The free CaO content of pyrolytic BOF slag is much lower than that of ordinary BOF slag and the volume expansion of pyrolytic BOF slag is less than 0.5%. The unconfined compressive strength (UCS) of cement-stabilized macadam using pyrolytic BOF slag is about 30% higher than that of andesite. Although the water loss rate is higher than a natural aggregate, dry shrinkage of pyrolytic BOF slag cement-stabilized macadam is about 30–50% less than that of a natural aggregate. Meanwhile, its shrinking speed is also slower than that of a natural aggregate. The micro-expansion properties of pyrolytic BOF slag could effectively partially offset the shrinkage characteristics of cement-stabilized macadam. Finally, the Toxicity Characteristic Leaching Procedure (TCLP) test results indicated that the metal leaching concentration meets the Chinese environmental standards. This study provides a direction for the large-scale and effective sustainable application of pyrolytic BOF slag.

Compressive strength and microscopic mechanism of nanosilica modified recycled aggregate mortar

Due to low density, large pores, and numerous cracks, recycled aggregate mortar has defects of lower fluidity and lower strength compared to natural aggregate mortar. In order to modify inherent defects of recycled aggregates, nanosilica (NS) with different dosages (0%, 0.6%, 1.2%, 1.8%, 2.4% and 3%) was added to recycled aggregate mortar (RNC), and 40% natural sand in RNC was replaced by recycled aggregates. Then consistency test, compressive strength test and microscopic tests (SEM, EDS and XRD) were conducted to investigate working performance and microscopic mechanism. It was found that the addition of NS can improve the flowability of RNC, and the consistency value reaches the maximum (53 mm) while NS content is 2.4%, which increases by 14% comparing to the specimen without NS. The compressive strength of RNC increases and decreases with increasing NS content in the ranges of 0–1.8% and 1.8–3% respectively, and compressive strength is 3.3 and 5.9 MPa at curing ages of 7 d and 28 d respectively while NS content is 1.8%, which increase 50% and 14% comparing to the specimen without NS. Meanwhile, the consistency value of the specimen with NS content of 1.8% is 51 mm, which is close the maximum value corresponding to NS content of 2.4%. For that, 1.8% is suggested as the optimal content of NS. Moreover, the addition of NS can reduce the brittleness index and mechanical damage degree, and enhance the energy absorption effect. Microscopic analysis reveals that NS can not only fill the inherent cracks and pores of recycled aggregates, but also promote cement hydration reaction, and more hydration products (C-S-H) can efficiently reduce the cracks and pores of recycled aggregates. It is believed that the finds of this paper can provide theoretical support for the application of recycled aggregates in practical engineering.

Fracture characteristics and damage evolution of manufactured sand-based ultra-high performance concrete using tensile testing and acoustic emission monitoring

To address the challenges posed by the excessive exploitation of natural river sand, manufactured sand (MS) was used as a substitute material for natural sand to produce manufactured sand-based ultra-high performance concrete (UHPMC). This study aims to investigate the effects of MS replacement ratio, stone powder content, steel fiber content, and steel fiber shape on the fracture characteristics and damage evolution of UHPMC under tensile load through tensile tests combined with acoustic emission (AE) technology. The research results indicated that the stress-strain behavior of UHPMC could be divided into low strain hardening, low strain softening, and high strain softening. The tensile strength and energy absorption of the UHPMC were less correlated with MS replacement ratio. The tensile strength showed a trend of first increasing and then decreasing with the increase of stone powder content, and UHPMC with a 4% stone powder content presented the better tensile strength. The tensile damage process of UHPMC was mainly concentrated in the range of tensile strain from 0.0002 to 0.0025. The microstructure analysis of the UHPMC matrix revealed that an optimal amount of stone powder enhances the bond property between MS and mortar, thereby improving tensile performance. AE monitoring indicated that AE amplitude and AE energy provide sensitive identification capabilities for classifying the elastic state, strain hardening, and strain softening stages of UHPMC. The findings of this study contribute to understanding the fracture characteristics and damage evolution of UHPMC, promoting the engineering application of MS in ultra-high-performance concrete.

Dynamic response of ultra-high performance engineered cementitious composites (UHP-ECC) under low-velocity impact: Effect of waste rubber incorporation and low temperatures

This study aims to explore the dynamic response of ultra-high performance engineered cementitious composites (UHP-ECC) incorporating waste crumb rubber (CR) at various temperatures, focusing on its potential to enhance the resilience and sustainability of civil infrastructures against low-velocity impacts. To date, the impact behaviour of UHP-ECC under low temperatures has rarely been explored. Firstly, natural river sand and waste tyre CR was utilized to prepare the UHP-ECC. Then, a series of mechanical tests, including compression test, flexural test and uniaxial tensile test were carried out to investigate the static mechanical properties of rubberised UHP-ECCs. In addition, the effects of different waste CR incorporations (0%, 5%, 10%, and 15%) and various temperatures (25 °C, −5 °C, −30 °C, −50 °C, −100 °C and −196 °C) were comprehensively investigated by low-velocity impact tests with constant impact energy. Lastly, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) model was introduced to evaluate the overall performance of UHP-ECC. It was found that the use of river sand and CR significantly enhanced the tensile ductility and impact toughness of UHP-ECC. Impact energy primarily dissipates through damage such as matrix crack initiation, propagation, and fibre pull-out/rupture within the specimen. Adding CR notably decreased stress fluctuations during impact at room temperature, facilitating steady state energy absorption. Moreover, the time to reach peak impact force decreased with decreasing temperature across all UHP-ECC groups. At room temperature during impact process, fibre failure mode is dominated by pull-out failure, while lower temperatures lead to increased fibre rupture at the cracking surface. In low-temperature conditions, the impact response of rubberised UHP-ECC necessitates a comprehensive consideration of the synergistic effects, including material contraction, fibre bridging capacity, rubber phase transition, and water freezing.

Large-Scale Experimental Model Of Edge Treatments For Constructed Salt Marshes

Large stretches of Canada’s coastlines are lined with legacy dykes (or levees) to provide protection against coastal flooding and erosion. However, future sea-level rise presents a risk to these structures, which may result in the dykes being under designed when exposed to future water levels and wave conditions. Under certain conditions, these dykes can be augmented with a coastal saltmarsh to create a living dyke, which allows for the existing dyke to be more resilient against sea level rise without the need to retrofit the dyke with a higher crest elevation or larger armour stone. The coastal saltmarsh is able to attenuate storm waves, resulting in lower wave energy at the dyke, while also attracting and retaining sediment to combat coastal erosion. The Living Dyke project in Boundary Bay, Canada is a pilot project being used to test the living dyke concept by placing sediment and planting salt marsh vegetation in the foreshore combined with upgrades to the existing dyke. Kerr Wood Leidal Associates Ltd. prepared a preliminary design which incorporated four different edge treatment features that are to be installed at the offshore edge of a newly constructed salt marsh platform in order to attenuate wave energy and retain the placed sediment before the planted vegetation can be established. The proposed edge treatment features included a natural sand edge, a rounded gravel berm, an oyster-shell filled bag berm, and a brushwood dam. Large scale (full scale for all edge treatment feature tests except for the brushwood dam which was conducted at half-scale) physical model experiments were carried out by the National Research Council of Canada’s Ocean, Coastal and River Engineering Research Centre in their Large Wave-Current Flume to investigate the performance, including stability of the edge treatment features, wave attenuation ability, and stability of the salt marsh platform, of these edge treatment features under varying water level and wave conditions that are present at Boundary Bay.

Usability of sand samples in TL Radiation Dosimetry.

This study investigated natural sand thermoluminescence (TL) response as a possible option for retrospective high-dose gamma dosimetry. The natural sand under investigation was collected from six locations with selection criteria for sampling sites covering the highest probability of exposure to unexpected radiation on the Egyptian coast. Dose-response, glow curve, chemical composition, linearity, and fading rate for different sand samples were studied. Energy Dispersive X-ray Spectroscopy (EDX) analysis revealed differences in chemical composition among the various geological sites, leading to variations in TL glow curve intensity. Sand samples collected from Ras Sedr, Taba, Suez, and Enshas showed similar TL patterns, although with different TL intensities. Beach sands of Matrouh and North Coastal with a high calcite content did not show a clear linear response to the TL technique, in the dose range of 10Gy up to 30kGy. The results show that most sand samples are suitable as a radiation dosimeter at accidental levels of exposure. It is proposed here that for high-dose gamma dosimetry with doses ranging from 3 to 10kGy, a single calibration factor might be enough for TL measurements using sand samples. However, proper calibration might allow dose assessment for doses even up to 30kGy. Most of the investigated sand samples had nearly stable fading rates after seven days of storage. The Ras Sedr sands sample was the most reliable for retrospective dose reconstruction.

Experimental study on the preparation of wood aggregate recycled concrete using waste wood and recycled fine aggregate from construction and demolition wastes

As a renewable resource, wood has the advantages of a high strength-weight ratio, high yield and excellent thermal insulation. Meanwhile, the resource utilization of large quantities of waste wood, waste furniture and mixed wood generated by the demolition of old houses and the removal of building formwork are basically in a blank state. Therefore, in this study, construction solid waste—waste wood and recycled fine aggregate were used as coarse and fine aggregates to replace natural sand and gravel, respectively, and synergized with three cementitious materials (sulfoaluminate cement, portland cement and geopolymer cement) to prepare wood aggregate recycled concrete (WARC). Focus on the evolution law of basic property, thermal insulation property, mechanical property, shrinkage property, environmental and economic benefits of WARC. The results showed that the mechanical and shrinkage properties of WARC were deteriorated by using WA and recycled fine aggregate (RFA) instead of natural aggregates. The dry density of WARC was as low as 1770 kg/m3. The 28 d maximum compressive and flexural strength were 34.8 and 5.69 MPa, which were better than traditional C30 concrete. Compared with conventional concrete, WARC has excellent thermal insulation properties. The thermal conductivity was reduced by up to 81.9 % compared to traditional concrete, which would make WARC very promising for non-structural components (green insulated wall materials and precast wall panels, etc.). By calculating CO2 emissions and compressive strength-cost efficiency values, it was found that the WARC prepared with geopolymer cement could reduce CO2 emissions by 31.3 % while possessing good mechanical properties and economic benefits, making it the optimal cement-based material for preparing WARC.

Environmental Markers of Plastics and Microplastics.

The slow reaction rates to chemical and photochemical degradation are well-known properties of plastics. However, large plastic surfaces exposed to environmental conditions release particles and compounds that affect ecosystems and human health. The aim of this work was to identify compounds associated with the degradation of polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC) microplastics (markers) on silica and sand and evaluate their use to screen microplastics on natural sand. Products were identified by using targeted and untargeted LC-HRMS analysis. All polymers underwent chemical oxidation on silica. PE released dicarboxylic acids (HO2C-(CH2)n-CO2H (n = 4-30), while PS released cis/trans-chalcone, trans-dypnone, 3-phenylpropiophenone, and dibenzoylmethane. PVC released dicarboxylic acids and aromatic compounds. Upon irradiation, PE was stable while PS released the same compounds as under chemical oxidation but at lower yields. Under the above condition, PVC generated HO2C-[CH2-CHCl]n-CH2-CO2H and HO2C-[CH2-CHCl]n-CO2H (n = 2-19) dicarboxylic acids. The same products were detected on sand but at a lower concentration than on silica due to better retention within the pores. Detection of markers of PE and PS on natural sand allowed us to screen microplastics by following a targeted analysis. Markers of PVC were not detected before or after thermal/photo-oxidation due to the low release of compounds and limitations associated with surface exposure/penetration of radiation.

Potassium citrate-activated pure BOF slag-based mortars utilizing carbonated and autoclaved BOF slag aggregates

This study proposes novel basic oxygen furnace (BOF) slag mortars formulated with tri-potassium citrate (TPC) activated BOF slag as binder and treated BOF slag (carbonated (CB) and autoclaved (AB)) as aggregates, aiming to maximize the utilization of BOF slag in the construction industry. Untreated BOF slag (UB) and natural sand (NS) were employed as reference aggregates. The effects of carbonation and autoclaving were investigated, focusing on the interfacial transition zone (ITZ) properties through SEM-BSE greyscale thresholding and constituent segmentation analysis. Results indicate that both treatments reduce the free CaO, promote CaCO3 formation, and modify the aggregate surface. The 28 d compressive strength of pure BOF slag-based mortars with UB, CB, and AB aggregates are 25.8, 29.4, and 34.8 MPa (average at varying TPC dosages), significantly higher than that with NS (19.6 MPa). Pure BOF slag-based mortars also show narrower ITZ thicknesses and the absence of bond cracks. Mortars with CB and AB aggregates exhibit fewer unreacted particles and more hydration products within the integral binder region compared to those with UB. Overall, pure BOF slag-based mortars present a more robust aggregate/binder interface that is further enhanced by the aggregate treatments. Leaching values of all mortars are well below the Dutch legal limits. The findings suggest promising application prospects for pure BOF slag-based mortars in substituting cement mortars and valorizing BOF slag.

Data-Driven Assessment of the Impact of Hurricanes Ian and Nicole: Natural and Armored Dunes in the Aftermath of Hurricanes on Florida’s Central East Coast

Hurricanes Ian and Nicole caused devastating destruction across Florida in September and November 2022, leaving widespread damage in their wakes. This study focuses on the assessment of barrier islands’ shorelines, encompassing natural sand dunes and dune vegetation as well as armored dunes with man-made infrastructure such as seawalls. High-resolution satellite imagery from Planet was used to assess the impacts of these hurricanes on the beach shorelines of Volusia, Flagler, and St. Johns Counties on the Florida Central East Coast. Shorefront vegetation was classified into two classes. Normalized Difference Vegetation Index (NDVI) values were calculated before the hurricanes, one month after Hurricane Ian, one month after Hurricane Nicole, and one-year post landfall. LiDAR (Light Detection and Ranging) was incorporated to calculate vertical changes in the shorelines before and after the hurricanes. The results suggest that natural sand dunes were more resilient as they experienced less impact to vegetation and elevation and more substantial recovery than armored dunes. Moreover, the close timeframe of the storm events suggests a compound effect on the weakened dune systems. This study highlights the importance of understanding natural dune resilience to facilitate future adaptive management efforts because armored dunes may have long-term detrimental effects on hurricane-prone barrier islands.