Khalifa Al-Jabri

This study presents a framework for developing low-carbon, printable limestone–calcined clay cement (LC³) using locally available clays in Oman that primarily contain kaolinite, illite, and montmorillonite. A dataset of 287 formulations using varying the proportions of these components and limestone, with each mix experimentally tested for compressive strength, flexural strength, and static yield stress to link mechanical performance with printability. Two supervised machine learning models: Gaussian Process Regression (GPR) and a shape-constrained Generalized Additive Model (GAM), were trained on the dataset. GPR showed superior performance, achieving R² values of 0.966 (compressive strength), 0.958 (flexural strength), and 0.736 (yield stress). A multi-objective optimization approach identified an optimal LC³ composition of 60% kaolinite, 5% illite, 5% montmorillonite, and 30% limestone. This mix yielded predicted properties of approximately 35 MPa compressive strength, 4.0 MPa flexural strength, and 720 Pa static yield stress. Experimental validation confirmed improved rheological behavior, with peak shear stress reaching about 950 Pa compared to 670 Pa for an OPC control, while maintaining shear-thinning characteristics. Mechanical testing of 3D-printed elements confirmed anisotropy due to layer interfaces, with 28-day strengths of 33.80 MPa (perpendicular) and 24.00 MPa (parallel), compared to higher values in the control mix. Durability tests using 1% HCl over 120 days showed better residual strength for LC³ (≈24 MPa) than the control (≈22 MPa). Strength degradation followed a Kohlrausch–Williams–Watts model (R² = 0.91), enabling structural parameterization. A validated finite-element model of a 3D-printed wall predicted a 47% reduction in load capacity and 35% stiffness loss after acid exposure. Overall, the study demonstrates a practical, reproducible pathway for sustainable, printable LC³ systems using regional materials. All codes and inputs are provided in Appendix for full reproducibility.

This paper presents a forensic investigation methodology which was adopted to identify the causes of deterioration and damage due to groundwater leakage beneath a reinforced concrete (RC) building. Extensive visual inspection, structural, geotechnical and geophysical investigations were used to identify the causes of the problem, assess the structural stability and integrity of the affected building. This study found that the main cause of underground water intrusion into the basement room is from irrigation of lawn and trees that surround the building where the water level was depicted at a depth of 3 m. The geotechnical and geophysical investigations were consistent and revealed the presence of a variable fill layer followed by a thin top layer of medium dense to dense sand followed by weathered conglomerate overlying sandstone. Shutting off the irrigation systems and the removal of the lawns and trees from the immediate vicinity of the building resulted in the stoppage of water intrusion into the basement within 90 days. The study concluded that the building is stable, while precaution remedial measures are recommended to prevent further deterioration. This study also highlights the effectiveness of combining geophysical and geotechnical methods for forensic analysis of damaged buildings.

Ferrochrome (FeCr) slag is a by-product of high-carbon ferrochromium, which is used in the manufacturing of stainless steel. In this study, FeCr was evaluated as a replacement for natural aggregates in hot-mix asphalt (HMA) bituminous base and wearing course layers. Four mixes were designed according to the Superpave mix design procedure, one control and three mixes, with FeCr slag replacing coarse, fine, or total aggregate. FeCr slag exhibited higher angularity and surface roughness than natural aggregates, resulting in an increased number of voids in mineral aggregate (VMA) and increased binder content. Performance testing using dynamic modulus, finite element analysis, and rutting evaluation using the MEPDG rut model showed that rutting increased with increased slag content. However, mixes with coarse aggregate replacement performed better than those with fine aggregate replacement. TCLP testing indicated that the FeCr slag is environmentally safe. The heavy metal leachate content was well below regulatory limits. Economic analysis showed material cost savings of up to 44% and 4% in the bituminous base and wearing course layers, respectively. The findings support the use of FeCr slag as a coarse aggregate replacement in asphalt mixes, offering both environmental and economic benefits.