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Memo from Surendra P. Shah: Ignorance, Inquiry and Innovation-driven cutting-edge research in cement and concrete
No full textDeveloping 3D Printable Concrete using Quarry By-Products as Partial Replacement for Cement
No full text3D concrete printing (3DCP) is rapidly growing due to its wide range of advantages over conventional cast concrete. However, one major concern is that it 3DCP mixes typically have high cement contents and have a high carbon footprint as a result. To address this concern, this study incorporates quarry by-products (e.g., pond fines, screenings) in 3DCP mixes, which serves as a rheology modifier and serves to reduce the cement content. Pond fines were used as a partial replacement of cement, and screenings were used as the fine aggregate. The resultant mixtures demonstrated adequate compressive strength, higher compressive strength, and improved rheological properties relative to the control mix without quarry by-products
Form Optimization Applications of 3D Concrete Printing: From Bridge to Protective Structures
No full textIn construction, 3D concrete printing (3DCP) is emerging as a technology that has the potential to create a significant impact on the state of practice and overcome several limitations of conventional construction processes. 3DCP focuses on delivery systems that build a structure using layer deposition. 3DCP technology is, however, still in a nascent stage in construction-related applications. Techniques for printing free-standing structures are not sufficiently developed for large- scale applications. In this paper, the concept of form-specific structural system optimization that broadly follows ‘material-follows-force’ is used to arrive at a shape that reduces weight while minimizing the requirement of conventional reinforcement. This concept of form optimization is demonstrated with the design of two structures: (a) a bridge that is off-site printed; and (b) an on-site printed protective structure against blast and ballistic threat
Mechanics of Fracture in Layered Architected Materials
No full textThis talk asks the role of mechanics of materials, particularly fracture mechanics in design and engineering civil infrastructure materials. Concrete, a quasi-brittle material is the backbone of the civil infrastructure. Decades of research on engineering and fracture mechanics of concrete led by the hundreds of pioneering works of great scholars, have helped us understand mechanism of crack initiation and propagation in heterogeneous materials. However, there remain a significant need to continue understand mechanics of damage in conventional and novel heterogeneous infrastructure materials. Growth in automation and robotics (e.g., 3D-printing), innovative cementitious composite materials (e.g., architected material), and numerical frameworks (e.g., coupled and multi-physics) have enabled us to expand on the design domain and performance characteristics. Here, we highlight how revisiting fundamental frameworks for representing heterogeneity via proposed statistical mechanics methods and developing computational algorithms through coupled phase-field and cohesive zone model can help understand fracture in layered and architected materials and design for it
Effect of absorption kinetics of superabsorbent polymer on 3D printing characteristics
No full textThis study evaluates the effect of different superabsorbent polymers (SAP) types on rheological properties, printability, and mechanical properties of 3D concrete printing (3DCP). Three types of SAP, including two acrylamide-co-acrylic polymers with coarse and fine particle sizes (S1 and S2) and an acrylic copolymer (S3), were employed. Results showed that the use of S1 and S2 SAP exhibiting high retention ability enhanced thixotropy, whereas the S3 SAP with rapid desorption reduced thixotropy. The S1 SAP was the most significant in maintaining a higher internal relative humidity, thus resulting in higher 28-d compressive strength. The reduction in 28-day compressive strength for printed specimens was correlated with the increase of static yield stress in 5 min (τfloc). The S3 SAP acted as a rheology-modified agent to reduce τfloc and the loss of 28-day compressive strength for printed specimens by 10%-20%
Responsive functional polymers and nano-particles for active control of concrete during processing
No full textThe presentation summarizes two options to achieve active rheology control of concrete: switchable functional polymers and responsive nano-particles. Some potential applications are described, and remaining challenges are discussed
Hempcrete as low carbon solution for thermal retrofitting of buildings
No full textThermal mortars are developed with hemp shives and pozzolans for thermal retrofitting of cultural heritage buildings, including concrete architecture from the 50s. The goal is to improve the thermal performance of the building, while reducing the carbon footprint. This research is within the framework of European Union’s Horizon 2020 (Sincere). A range of mixtures were developed based on standard mortar for plaster, as a reference. The research investigates the possibility of partly replacing the cement with pozzolans, as well as the sand in the mortar with fine hemp shives, to obtain lower EE and EC of the mixture, as compared to the reference. Replacing 60% of the cement with pozzolans improves the compression strength. Replacing the sand with several percentages of fine hemp shives reduces the compression strengths, while expected to significantly improve the thermal conductivity of the mortar
The synergy between SFRC and structural steel in increasing the ductility of composite structures
No full textOur research on the compressive behavior of steel-fiber reinforced concrete (SFRC) led to a constitutive model in Annex L ofthe new Eurocode 2. This recognition piqued the interest of ArcelorMittal, who requested that we explore the implications of increased compression ductility for composite structures, particularly beams with embedded structural steel sections. The findings from this research demonstrate that the compressive ductility of SFRC enables us to fully utilize the tensile capacity of structural steel in composite structures, resulting in unprecedented levels of structural ductility
Experimental Study of Mineral Carbonation of High-Calcium Fly Ash: CO₂ Sequestration and Its Effect on Pozzolanic Reactivity
No full textMineral carbonation of industrial wastes offers a sustainable approach to carbon sequestration and waste valorization. This study investigates the aqueous mineral carbonation of three high-calcium fly ashes under ambient conditions using recyclable sodium carbonate solutions. The effects of operational parameters, including liquid-to-solid ratio (L/S), sodium carbonate concentration, and carbonation duration, were systematically analyzed using response surface modeling. A degree of carbonation (DOC) up to 52% was achieved within one hour under ambient conditions, with calcite (CaCO3) identified as the dominant product phase. Advanced characterization techniques revealed significant transformations in the physicochemical properties of carbonated fly ashes (CFAs), including increased particle size and reduced density. Notably, the carbonation process induced a linear decrease in pozzolanic reactivity, with a reduction in cumulative heat release from 19.2 J/g to 15.8 J/g per gram of CO2 sequestered. Despite the reduction, CFA with 9.5 wt% CO2 sequestered meets RILEM criteria for pozzolanic reactivity, demonstrating its potential as a sustainable component in low-carbon concrete systems
A Novel Approach for Geopolymer Setting Control: Heat Pre-treatment of Ground Granulated Blast Furnace Slag
No full textThis study aimed to develop a technology for delaying the setting of geopolymer (GP) or alkali-activated material (AAM) that utilizes ground granulated blast-furnace slag (BFS) as a precursor. The approach involved pre-treating the BFS through heating. A detailed investigation was conducted to understand how the heating temperature and duration influenced the chemical characteristics of the BFS, as well as the setting behavior and compressive strength of the resulting GP. The experimental results indicated that when BFS was heat-treated at temperatures below 750°C, it maintained its amorphous state regardless of the heating time. Consequently, its reactivity remained almost equivalent to that of unheated BFS. A stable and effective delay in setting time was specifically observed after a 12-hour heat treatment at 700°C. In contrast, BFS heat-treated at 800°C led to its crystallization, which significantly increased the setting time but also reduced its reactivity. The results demonstrate that by blending the heat-treated crystalline BFS with the untreated amorphous BFS in an appropriate ratio, it is possible to achieve a desired GP setting time, providing a viable method for precise control