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Synergistic Effects of CO2 Curing and Recovered Carbon Black Nano additives on Early Age Performance of Cementitious Composites
No full textBoth CO2 curing, a potential precast plant treatment, and nano-additives can enhance the strength and reduce the porosity of cementitious composites. However, their simultaneous application may lead to interactions that influence curing effectiveness, particularly as nanoparticles may alter the effectiveness of CO2 curing. This study investigates the combined effects of CO₂ curing and nanomodification on the early-age strengths of precast cementitious composites, given its importance for precast industry productivity. Mortar and paste batches incorporating recovered carbon black (rCB), a nanomaterial derived from recycled waste rubber, were prepared with 0% and 2% rCB by cement weight. Specimens form each mixture were subjected to both normal curing and CO2 curing. Compressive strength of mortars and thermogravimetric analysis of cement paste were performed at 7 days. The results indicate that rCB additive can enhance the early-age strength of CO2-cured cementitious composites, presenting a potential opportunity for waste valorization of a recovered nanomaterial
Carbon-negative concrete by using biochar
No full textIn this paper we present the realization of carbon negative concrete by substituting cement and aggregate with biochar. By conveniently choosing feedstock and properties of biochar, it is possible to maintain the same compression strength of standard concrete. Several biochar types derived from different vegetal feedstocks were used, that were characterized for their composition and physical properties. The effect of biochar type and grain size distribution was studied, demonstrating the possibility of maintaining or even slightly improving the mechanical properties of mortar and concrete, depending on the biochar content. The physical properties and pore distribution of mortar containing biochar was also studied in detail in order to understand the reason behind the mechanical properties improvement observed at low biochar content
Mechanistic study of the improvement of LC3 rheological properties by PCE superplasticizers- A comparative study with OPC system
No full textRecently, LC3 attracts more and more attentions due to low CO2 emission. Understanding the mechanisms of PCEs on LC3 rheology is crucial for advancing its application. This study investigates the rheological properties of LC3 and ordinary Portland cement (OPC) in response to PCE superplasticizers. HPEG PCEs were successfully synthesized via free radical copolymerization with varying acrylic acid (AA) to macromonomer (MM) ratios, and their quality were characterized using Gel Permeation Chromatography (GPC). Fluidity tests and rheology measurements revealed that PCEs enhance fluidity and reduce dynamic yield stress and plastic viscosity in both systems, although LC3 requires a higher PCE dosage than OPC. At the same time PCEs in OPC improves with increasing AA:MM ratios, whereas in LC3, the optimal ratio was found to be medium. The total organic carbon and PCE anionic charge amount measurements were applied to discover the mechanisms. Clacined clay consumed a large amount of PCE which was not contributing to dispersion due to its high specific surface area rather than surface charge. Furthermore, the performance of PCEs in the LC3 system is governed by the synergistic effect of their anionicity and side chain density. These findings provide insights into the distinct mechanisms of PCEs in LC3 compared to OPC, offering a theoretical basis for developing tailored PCEs for LC3 applications
Functionalized carbon material in cement-based composites, a multivariate approach
No full textThis work describes the process that led to the optimization of compressive strength and fracture energy of a cement-based composite material enhanced with carbon allotropes: carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and carbon fibers (CFs). The goal was achieved through the use of a multivariate analysis system, modifying three variables corresponding to the quantities of CNTs, GNPs, and CFs. All the allotropes used in the study were subjected to functionalization to improve their wettability and interaction with the cement matrix. A face-centered central composite design (FCCD) was used as the experimental design, where these three variables were modified at three levels. The levels were predetermined to ensure that the total amount of functionalized carbon allotropes (CNTs, GNPs, and CFs) do not exceed 0.2% of the weight of the cement used in the mix design. For the graphical visualization of the data, the response surface methodology (RSM) was employed to identify the relative maxima for each response studied. The RSM, supported by the FCCD, represents a powerful method for improving the understanding of relationships between variables and optimizing results. The experimentation led to a significant improvement in compressive strength by 27% and fracture energy by 690% compared to the reference sample. Subsequently, the model was validated to assess the reproducibility of the obtained results, exploring how consistent the results could be over time
Comparison of Magnetorheological Properties of Fayalite Slag and Nano-Fe3O4 Incorporated Cement Mixtures
No full textOne of the active rheology control methods involves adding magnetically-responsive mineral particles to fresh concrete and activating them by an external magnetic field, turning it into a magnetorheological (MR) fluid with controllable rheological properties. Nano-Fe₃O₄ is the most common material for MR cement, but other minerals also contain magnetizable phases. This study compares the MR properties of cement mixtures with fayalite slag and nano-Fe₃O₄
Concrete Material Bank in Japan toward CO2 recycling
No full textProviding excellent performance as a structural material, concrete has long been essential for modern civilization and recognized as a material that will continue to maintain and support the development of human society. Now that recycling of concrete in a completely closed loop has become technically feasible, concrete is being seen in a new light. On the other hands, the huge issues regarding carbon dioxide emissions all of the world are a concern in the construction field as well as in society. To solve this problem, a concept for new Calcium Carbonate Concrete (CCC) is proposed. This paper is focused on prediction of the resource amount of CCC, which is manufactured by treating concrete waste as a raw material with calcium hydrogen carbonate in which carbon dioxide is dissolved. It was described the details of the amount of supply potential of concrete waste from the past 1950s to the future in 2050s and analysed a resource recycling scenario based on the long-term transition future perspectives
Properties of Calcined Clay-Limestone Cement Concrete
No full textIncorporating calcined clay (C) and limestone powder (L) into concrete effectively reduces carbon emissions. However, its application is mainly limited by commercial material variability, availability, and specifications. This study presents the properties of concrete made with Type IL cement, 30% C, and/or 15% L from commercially available sources across various U.S. regions. Results indicate that C extended setting time and reduced early-age strength and surface resistivity (SR) but enhanced both at later ages, while further addition of L lowered strength due to dilution effect, as expected. Overall, concrete properties are sufficient for implementation in construction
Challenging the School Boundaries: Exploring Challenges and Opportunities in Homeschooling Engineering Education
No full textHomeschooling sparks controversy regarding the quality of education when compared to the traditional schooling system. However, homeschooling rates have doubled nationwide since the pandemic, especially among minorities. Funding and curricular material resources may be limited for homeschooling families, especially those from diverse backgrounds. Therefore, this essay discusses the need to expand the current boundaries of engineering education to include homeschooling communities. Drawing from our homeschooling experience, we present three recommendations that respect the cultures and unique characteristics of homeschooling to promote engineering practices in these communities. Our proposal challenges negative perceptions of homeschooling, enhancing our understanding of its unique characteristics to foster a strong engineering education preparation for all students
Influence of Printing Speed and Nozzle Size on Buildability of 3D Printed Concrete Walls: A Nonlinear Finite Element Study
No full textThe increasing adoption of additive manufacturing in construction necessitates robust simulation frameworks capable of capturing the time-dependent mechanical behaviour of fresh concrete. This study examines the influence of printing speed and nozzle size on the buildability of infilled concrete walls using finite element (FE) simulations. A nonlinear fracture-plastic constitutive model was employed to simulate the time-dependent mechanical behaviour of fresh concrete, with the modelling framework first validated against previously published experimental data to ensure reliability. Subsequently, six wall configurations were analysed, incorporating nozzle diameters of 30 mm and 40 mm, and printing speeds of 20, 30, and 40 mm/s. The results demonstrate that printing speed exerts a dominant influence on buildability. At the highest simulated speed (40 mm/s), premature structural failure was observed, limiting maximum wall heights to 0.56 m for the 30 mm nozzle and to 0.50 m for the 40 mm nozzle. At the intermediate speed (30 mm/s), structural stability improved markedly, with wall heights of 1.16 m and 1.12 m achieved for the 30 mm and 40 mm nozzles, respectively. At the lowest speed (20 mm/s), both wall models successfully reached the full target height of 3 m without collapse, and displacements remained minimal. While nozzle size had a less pronounced effect overall, it was found that the larger nozzle (40 mm) exhibited earlier collapse at higher speeds due to increased self-weight
Simulation Analysis of Secondary Creep of Corrosion Damaged Reinforced Concrete Beams based on ABAQUS
No full textConcrete creep is defined as deformation over time under a sustained load. When a structure is subjected to additional actions such as corrosion, damage to its components can occur, leading to a deterioration in performance. The structure then develops a long-term deformation known as secondary creep, which is greater than the creep deformation that occurs under sustained loads alone. The problem of secondary creep caused by corrosion of reinforcing steel, which is a common durability issue, is still not well understood. Corrosion-induced degradation, including partial loss of reinforcement, bond degradation and concrete cracking, exacerbates creep deformation by altering stress distribution and accelerating microcrack development. This coupled effect may lead to premature stiffness reduction and unpredictable long-term structural performance. To study the secondary creep law under corrosion damage more conveniently, this paper uses the numerical simulation method. Through Abaqus finite element analysis software, the creep calculation subroutine is written according to creep calculation theory and combined with the constitutive model of corroded reinforced concrete. This allows the secondary creep simulation and analysis of corroded beams to be carried out. The results indicate that a certain degree of corrosion damage can lead to secondary creep in the structure. The reinforcement constitutive model has a significant impact on the short-term stiffness of the beam, while the bond slip constitutive model has a greater impact on the long-term stiffness