Micro-Mechanical and 3D Fractal Analysis, Durability, and Thermal Behaviour of Nano-Modified Cementitious Lightweight Composites for Building Facades

There are increasing research endeavours on the application of nanotechnology in the construction industry and lightweight composites. In this study, the influence of different percentage (1%, 2%, and 3% by weight of cement) colloidal nano-silica particles on the mechanical, thermal, and durability properties of lightweight cementitious composites was studied through measurement of compressive strength, flexural response, micro-hardness measurement, pore structure analysis, thermal conductivity, water permeability, and chloride penetration. Moreover, 3D X-ray Compute Tomography together with digital image analysis and 3D fractal analysis was used to characterize the nano-silica, micro-structures, and the fracture surfaces. The experimental results show that incorporating nano-silica particles resulted in a mechanical strength increase up to 45.4 % and a water permeability and chloride migration decrease up to 51.2% and 48.2%, respectively. The micro-structural and 3D fractal analysis also indicated that dense, flaw-free, and thus more resistant, interfaces to micro-cracks were formed and greater fractal dimensions were obtained with the increase of the nano-silica content. Finally, the 3D views confirmed that the nano-silica clusters were well interconnected which further increase the carrying capacity and reducing the heat flow.

Microstructure and Mechanical Behavior of AlCoCrFeNi HEA Particles Reinforced 6063Al Alloy Matrix Composites

Lightweight composites consisting of 6063 aluminum alloy matrix reinforced with AlCoCrFeNi high-entropy alloy (HEA) particles were fabricated by the powder metallurgy through hot pressing and hot extrusion under vacuum. A detailed microstructural characterization was carried out along with the analysis of mechanical properties. The results revealed that the observed uniform distribution of HEA powders and a good bonding strength resulted in an effective strengthening and increased plastic strain of the reinforced composite. The tensile properties of composites were effectively improved by the addition of 10 and 30 vol % of reinforcing HEA particles.

Cementitious Composites with High Compaction Potential: Modeling and Calibration

There is an increasing need for the development of novel technologies for tunnel construction in difficult geological conditions to protect segmental linings from unexpected large deformations. In the context of mechanized tunneling, one method to increase the damage tolerance of tunnel linings in such conditions is the integration of a compressible two-component grout for the annular gap between the segmental linings and the deformable ground. In this regard, expanded polystyrene (EPS) lightweight concrete/mortar has received increasing interest as a potential “candidate material” for the aforementioned application. In particular, the behavior of the EPS lightweight composites can be customized by modifying their pore structure to accommodate deformations due to specific geological conditions such as squeezing rocks. To this end, novel compressible cementitious EPS-based composite materials with high compaction potential have been developed. Specimens prepared from these composites have been subjected to compressive loads with and without lateral confinement. Based on these experimental data a computational model based on the Discrete Element Method (DEM) has been calibrated and validated. The proposed calibration procedure allows for modeling and prognosis of a wide variety of composite materials with a high compaction potential. The calibration procedure is characterized by the identification of physically quantifiable parameters and the use of phenomenological submodels. Model prognoses show excellent agreement with new experimental measurements that were not incorporated in the calibration procedure.