Mahmoud Shakouri

Design professionals play a pivotal role in shaping the built environment, not only through the development of drawings and technical specifications but also by serving as a proxy between project owners and constructors in certain project delivery methods. Every design must fulfill the owner’s objectives and project specific criteria that include quality, cost, time, and, crucially, construction safety, all of which can vary across projects. The study objective was to investigate the extent to which designers prioritize worker safety during the design phase across three categories of project delivery methods: non-collaborative, collaborative, and mixed. To achieve the study objective, an online survey was utilized to collect data from 62 designers working in the Architecture, Engineering, and Construction (AEC) industry. Following survey data collection, statistical analysis was used to examine the extent to which designers focus on worker safety relative to other design criteria for each delivery method. The survey findings reveal that, within the studied sample, designers’ attention to construction worker safety remained relatively consistent regardless of the delivery method employed. Thus, no statistically significant relationship was found between the delivery method and the degree of safety emphasis among designers. However, collaborative delivery methods that foster greater transparency and interdisciplinary engagement are expected to positively influence project safety performance. Industry stakeholders interested in improving safety performance are encouraged to adopt collaborative delivery approaches and implement structured interventions, such as formal safety constructability reviews, to actively integrate safety into the early stages of project design.

Developing electrically functional geopolymer composites requires conductive fillers that improve electrical response while maintaining mechanical performance. This study examined that formulation tradeoff using graphene nanoplatelets (GNPs) in fly ash geopolymer mortar. An aqueous screening program comprised 48 dispersions prepared with sodium dodecyl sulfate (SDS), Triton X-100, or polyvinylpyrrolidone, combining four GNP concentrations with four dispersant-to-GNP mass ratios. Conductivity, pH, and visual observations over 12 days supported selecting SDS for subsequent mortar preparation, although these measurements did not establish superior nanoscale dispersion or long-term alkaline stability. Subsequent testing evaluated 16 SDS-GNP mortar mixtures alongside four SDS-only reference mixtures. Dispersion concentrations of 0.05, 0.10, 0.50, and 1.00 wt.% corresponded to approximately 0.0043, 0.0085, 0.0426, and 0.0852 wt.% GNP relative to fly ash. Compressive strength ranged from approximately 5.5 to 16.8 MPa, with higher loading generally associated with lower strength. At the lowest SDS-to-GNP ratio, increasing dispersion concentration from 0.10% to 1.00% reduced strength from about 11.8 to 7.2 MPa, a decrease of approximately 39%. Ultrasonic pulse velocity followed a similar trend, reaching about 3.0 km/s at lower concentrations compared with 2.08 to 2.50 km/s for the 1.00% mixtures. Bulk electrical resistivity generally ranged from 60 to 180 Ω·m after ambient storage and from 5 to 29 Ω·m after water immersion, without a consistent decrease as the GNP concentration increased. Factorial analyses indicated formulation interactions, while desirability analysis favored selected low-concentration mixtures for their combined mechanical and electrical responses. Lower GNP-dispersion concentrations therefore provided a more favorable balance under the tested conditions, but incomplete SDS-dose matching prevents attribution of the observed changes to GNPs alone. These results support formulation screening without establishing conductive-network formation or validating sensing and heating applications.

The durability of concrete structures exposed to chlorides is critically governed by chloride ingress, which induces reinforcement corrosion. While ordinary Portland cement (OPC) has been extensively studied, alternative binders such as calcium aluminate cement (CAC) and calcium sulfoaluminate (CSA) cement offer distinct microstructures that may enhance chloride resistance. Understanding how cement type and the water-to-cementitious material ratio (w/cm) influence the apparent chloride diffusion coefficient (D_a) is paramount for designing durable infrastructure. This study systematically quantifies the influence of cement type (OPC, CAC, CSA) and w/cm ratio (0.45, 0.55, 0.65) on D_a using a full-factorial experimental design and bulk diffusion testing. The results reveal a significant interaction between cement type and w/cm (p < 0.001). OPC exhibits predictable porosity-driven degradation, with D_a increasing exponentially from 8.42 × 10⁻¹² to 1.46 × 10⁻¹⁰ m²/s as w/cm increases from 0.45 to 0.65. CAC shows a non-linear response, with optimal performance at w/cm = 0.55 (D_a = 2.90 × 10⁻¹¹ m²/s) due to microstructural refinement from hydrate conversion but suffers severe degradation at w/cm = 0.65. CSA cement is extremely water-sensitive, with D_a increasing by an order of magnitude (from ~4 × 10⁻¹¹ to 3.37 × 10⁻¹⁰ m²/s) at w/cm = 0.65, marking a critical failure threshold. Model fit quality (R²) serves as a leading indicator of microstructural instability, which is corroborated by XRD phase analysis. This study concludes that CSA presents a high risk for field applications with poor w/cm control, while OPC offers more predictable performance, advocating for cement-specific, performance-based specifications beyond traditional OPC-centric limits.

Este artigo apresenta uma análise sistemática da literatura sobre a avaliação do ciclo de vida (ACV) e eficiência energética em habitação social, com foco na interação desses aspectos com a rede elétrica. O estudo avalia diferentes metodologias de ACV aplicadas a projetos habitacionais, considerando as variações nos parâmetros construtivos, no desempenho energético, no contexto climático e nas escolhas metodológicas. A revisão revelou lacunas importantes nas abordagens existentes, especialmente no que tange à ausência de uma metodologia padronizada para a avaliação dos impactos ambientais além das emissões de carbono e do consumo de energia. As principais questões abordadas no artigo foram: (i) estratégias de mitigação para a eficiência energética em habitação social (RQ1), que destacam o uso operacional de energia como o principal responsável pelo impacto ambiental durante o ciclo de vida das habitações sociais; (ii) alternativas de design para habitação social com foco em eficiência energética (RQ2), que evidenciam a importância do contexto climático, da tipologia do edifício e do sistema de isolamento para a eficiência energética; e (iii) estratégias de intervenção material (RQ3), que discutem os impactos incorporados de materiais de isolamento, ressaltando a importância de considerar esses efeitos na avaliação de alternativas de materiais e técnicas construtivas. A revisão conclui que, embora as alternativas de design e os materiais de construção tenham um impacto significativo na eficiência energética, a falta de uma avaliação abrangente que considere todos os aspectos do ciclo de vida limita a capacidade de tirar conclusões definitivas sobre as melhores práticas. O artigo enfatiza a necessidade de adotar uma metodologia integrada e abrangente de avaliação ambiental que contemple não apenas as emissões de carbono e o consumo de energia, mas também outros impactos ambientais relevantes. A implementação de uma abordagem mais sistêmica é essencial para avançar na construção de habitação social mais sustentável, atendendo aos princípios de economia circular e promovendo a transição para sistemas de eletricidade de baixo carbono.

This study investigates the potential of corn stover, an abundant agricultural byproduct, as a sustainable additive in concrete masonry units (CMUs). Preliminary trials were conducted to determine the optimal fiber length (~3 mm and ~10 mm), fiber content (0%, 1%, 3%, and 5% by volume), and alkalinization method (soaking in 0.5 M NaOH, KOH, or synthetic concrete pore solution) for corn stover fibers (CSFs). The results indicated that short fibers treated with synthetic concrete pore solution yielded the best compressive strength and workability, and were thus selected for the main study. A novel mixture was developed by replacing 10% of cement with corn stover ash (CSA) and incorporating 1% alkaline-treated CSF by volume. The resulting blocks (termed “Corncrete”) were evaluated for mechanical and durability properties, including strength, water absorption, bulk and surface electrical resistivity, rapid chloride permeability (RCPT), and fire resistance. Compared to conventional CMUs, Corncrete exhibited an 11–13% reduction in 28- and 91-day compressive strength, though the difference was statistically insignificant. Physically, Corncrete had a 4.4% lower bulk density and a 7.9% higher total water absorption compared to the control. However, its water absorption rates at early stages were 32% and 48% lower, indicating better resistance to moisture uptake shortly after exposure. Durability tests revealed a 13.7% reduction in chloride ion permeability and a 33% increase in bulk and surface electrical resistivity after 90 days. Fire performance was comparable between the two mixtures, with both displaying ~10.5% mass loss and ~5% residual strength after high-temperature exposure. These findings demonstrate that Corncrete offers balanced mechanical performance and enhanced durability, making it a viable eco-friendly option for non-structural masonry applications.

Graphene nanoplatelet aggregates (GNAs) are a low-cost, low-quality alternative to graphene nanoplatelets (GNPs), characterized by their three-dimensional stacked structure and porous surface morphology. Despite their affordability, limited research has been conducted on the effects of GNAs in cementitious systems. This study investigates the impact of GNAs on hydration kinetics, phase assemblage, mortar consistency, mechanical strength, bulk electrical resistivity, water absorption, and pore solution pH. Mortar mixtures with 0%, 0.05%, and 1% GNAs by cement weight were prepared using a water-to-cement ratio of 0.42 and cured for 28 days. The results showed that GNAs had minimal influence on hydration kinetics, with no significant changes in hydration products detected by XRD and TGA analyses. Mortar consistency consistently decreased with increasing GNA content. At 0.05%, GNAs had no significant effect on compressive strength or bulk electrical resistivity, whereas 1% GNAs reduced compressive strength by 10%. Water absorption was significantly lower in specimens with 1% GNAs as well, while pore solution pH increased at this dosage. The findings of this study indicate that the incorporation of GNAs at a 0.05% replacement level does not inherently enhance cementitious properties but can influence specific behaviors, such as workability and water absorption, when used at 1% dosages.

Seashells have been explored as a partial replacement for cement in cementitious matrices to promote sustainable waste management and decrease the carbon footprint associated with cement production. As research in this area expands, it is essential to synthesize current findings and practices to guide future studies on the feasibility of using seashells as a filler. This study analyzed existing research on using seashells as a partial cement replacement in cementitious composites through a systematic literature review conducted across six scientific databases, yielding 44 studies for data analysis and synthesis. Key findings identified the shell processing methods, established typical ranges for shell powder’s physical–chemical properties and dosage, and quantified the impact on mechanical properties in binary mixtures. The reported effects on mechanical properties varied among studies, potentially due to differences in processing techniques and the origins of the shells. Most improvements in composite properties were observed with 5% to 15% cement replacement in binary mixtures. Overall, incorporating shell powder reduces the carbon emissions of the produced composites. Further detailed investigations into shell processing variables and dosages are recommended to better understand how these factors influence the properties of the composites produced.

Introduction: Improper disposal of mollusk shells has led to environmental issues worldwide. Given their primary composition of calcium carbonate, these shells have been studied for their potential use as aggregate in cement composites, offering an environmentally appropriate destination for the waste and reducing virgin raw material use. However, there is a lack of research on the application of Sururu (Mytella falcata) shells, a species of mollusk commonly fished in countries such as Brazil. This study investigated the effects of Sururu shells waste from a Brazilian region on the mechanical and physical properties of mortar when partially replacing natural fine aggregate.Methods: Three mortar mixtures were produced, replacing 10, 20, and 40% of natural sand with Sururu shell aggregate (SSA) by mass. The specimens underwent consistency and density tests in their fresh state, and compressive strength, dynamic modulus of elasticity, and capillary absorption tests in their hardened state.Results: The results showed that workability decreased with the increase in SSA replacement, resulting in a reduction of 31.5% in consistency at 40% SSA replacement level. Compressive strength also decreased with SSA incorporation, but all samples continued to gain strength after 28 days, with 10% SSA samples showing only a 2.7% reduction compared to the control specimens. The dynamic modulus of elasticity was minimally impacted at 10% SSA, but significantly reduced at higher levels. Notably, SSA reduced capillary absorption in samples after 24, 48, and 72 h, indicating potential benefits in moisture management.Discussion: It was concluded that replacing 10% of natural sand with SSA was the most suitable option, considering the investigated mechanical properties of the mortar produced with SSA. However, further research is recommended to examine the durability and environmental impact of this solution.

This study examines the impact of risk models and investors’ risk aversion on the selection of community solar portfolios. Various risk models to account for the volatility in the electrical power output of community solar, namely variance (Var), SemiVariance (SemiVar), mean absolute deviation (MAD), and conditional value at risk (CVaR), were considered. A statistical model based on modern portfolio theory was employed to simulate investors’ risk aversion in the context of community solar portfolio selection. The results of this study showed that the choice of risk model that aligns with investors’ risk-aversion level plays a key role in realizing more return and safeguarding against volatility in power generation. In particular, the findings of this research revealed that the CVaR model provides higher returns at the cost of greater volatility in power generation compared to other risk models. In contrast, the MAD model offered a better tradeoff between risk and return, which can appeal more to risk-averse investors. Based on the simulation results, a new approach was proposed for optimizing the portfolio selection process for investors with divergent risk-aversion levels by averaging the utility functions of investors and identifying the most probable outcome.