This study evaluates a sintered lightweight aggregate produced from a 70:30 mass ratio of loess-like loam to hydraulic ash from the Kyzylorda thermal power plant (TPP), with an external 50:50 TPP-ash–ground-rice-husk dusting mixture. Four dusting regimes (C0–C3) were examined at 1000, 1030, 1060, and 1100 °C using 15 test specimens or portions per condition. C0 was the undusted control; the dusting-mixture-to-raw-granule mass ratios for C1, C2, and C3 were 1:2.5, 1:3.5, and 1:4.9, respectively. Dusting regime and firing temperature affected density, strength, water absorption, pore structure, and thermal conductivity. The selected C2 regime, corresponding to a dusting-mixture-to-granule ratio of 1:3.5, produced at 1060 °C an aggregate with a bulk density of 324 ± 18 kg/m3, cylinder crushing strength of 1.42 ± 0.08 MPa, water absorption of 15.8 ± 0.6%, and effective packed-bed thermal conductivity of 0.078 W/(m·K). Scanning electron microscopy (SEM) showed porous and consolidated regions; local energy-dispersive X-ray spectroscopy (EDS) indicated higher Ca, Al, and Fe in the examined shell region than in the examined core region. Lightweight concrete containing the developed aggregate achieved a dry density of 920 ± 5 kg/m3, 28-day compressive strength of 3.87 ± 0.22 MPa, water absorption of 19.4 ± 0.3%, and thermal conductivity of 0.215 ± 0.010 W/(m·K). The results identify 1060 °C and the C2 dusting regime as a preferred compromise among the tested conditions, based on a comparative assessment of density, cylinder crushing strength, water absorption, and thermal conductivity rather than a weighted numerical optimization.
Cement production generates substantial carbon emissions through clinker calcination and fuel combustion. This study applies a sequentially coupled Time-Dependent Scenario–Carbon Accounting–Slacks-Based Measure Data Envelopment Analysis (TDS–CA–SBM-DEA) framework to assess five South African cement-decarbonization pathways from 2023 to 2050: business-as-usual (BAU), energy efficiency and alternative fuels (EFF_FUEL), clinker substitution and material efficiency (CLINKER_MAT), carbon capture and novel binders (CCS_NOVEL), and an integrated net-zero-oriented pathway (NET_ZERO). Production-stage accounting explicitly accounts for amine-based carbon capture, which requires 3.0 GJ of regeneration heat and 100 kWh of auxiliary electricity per tonne of CO2 captured, including emissions from the natural-gas heat supply. Modeled baseline emissions are 8.49 Mt CO2 in 2023. By 2050, BAU reaches 9.50 Mt CO2, while CCS_NOVEL and NET_ZERO decline to 3.54 and 1.53 Mt CO2, respectively. NET_ZERO achieves a carbon intensity of 0.128 t CO2/t cement and cumulative emissions of 140.1 Mt CO2, avoiding 111.6 Mt, relative to BAU. CLINKER_MAT and NET_ZERO remain on the constructed 2050 DEA frontier. Sensitivity analysis identifies clinker factor as the strongest cumulative-emissions driver, while capture deployment and efficiency most influence residual emissions. The framework distinguishes carbon mitigation from scenario-relative resource efficiency, and highlights the additional thermal burden of selected capture technologies. The results are conditional on prescribed sector-level assumptions.
Reliable evaluation of reinforced concrete (RC) beams strengthened in shear remains challenging because of the complex interaction between concrete properties, strengthening configuration, and material characteristics. This study presents a complementary numerical and data-driven framework for near-surface-mounted (NSM) fiber-reinforced polymer (FRP)-strengthened RC beams. A validated finite element model was used to conduct a parametric study explaining how concrete compressive strength, FRP type, strengthening orientation, and FRP spacing govern the shear response, including beams with residual (post-heating) concrete properties. Independently, a Gene Expression Programming (GEP) model was developed using a database of 126 experimental beam tests collected from the published literature on undamaged and damaged strengthened beams, with damage represented through the residual concrete compressive strength; 70% of the data were used for training and 30% for validation. The proposed GEP model achieved a coefficient of determination (R2) of 0.964 for training and 0.945 for validation, and showed improved predictive accuracy compared with the ACI 440.2R provisions. Concrete strength, FRP orientation, and FRP spacing were identified as governing parameters by both the finite element study and the GEP equation. The developed GEP equation provides a practical and transparent tool for rapid prediction of shear capacity in engineering design and assessment.
Ultra-High-Performance Concrete (UHPC) offers excellent strength and durability but suffers from autogenous shrinkage due to its low water-to-binder ratio. Internal curing using superabsorbent polymers (SAPs) is a promising method for mitigating this issue. This study investigates how different SAP particle sizes (D50: 215 µm and 725 µm) and internal curing water levels (36 kg/m3 and 60 kg/m3) affect the mechanical behavior of slurry-infiltrated fiber concrete (SIFCON) under sealed and drying conditions. Internal curing effectively reduced shrinkage but caused compressive strength losses (12.2–20.3%) and increased permeable pore volume (up to 31.1%). The shrinkage data utilized for this trade-off assessment were obtained from a parallel study conducted by the authors using identical material batches and environmental conditions. The finer SAP enhanced flexural strength by up to 9.3% and toughness, which is hypothesized to be associated with an improved fiber–matrix interfacial transition zone (ITZ), whereas the coarser SAP led to a flexural strength loss of up to 42.9% and reduced toughness, which may result from localized void formation. The multi-variable graphical trade-off assessment showed that the finer SAP achieved a more favorable balance between shrinkage mitigation and mechanical performance, highlighting the importance of SAP characteristics.
This research aims to evaluate the effect of the binder:aggregate ratio on the physical, mechanical and durability properties of air lime mortars. The research focuses on analyzing the technical performance of lime mortars produced with five different binder-to-aggregate ratios. Various tests have been carried out to determine the performance characteristics of mortars produced using lime putty and natural river sand. These tests include methods such as unit weight, ultrasonic velocity, carbonation depth, volumetric shrinkage, modulus of elasticity and compressive strength. The 28-day experimental outcomes revealed a non-linear trend in strength development, which was governed by the coupled variations in both binder content and water levels within the mortar formulations. In the mortar series, shrinkage values decreased inversely proportional to the amount of aggregate after a 28-day curing period. The study highlights that increasing the binder ratio in mortars does not improve all properties, and that the aggregate ratio is also of great importance. This research specifically presents a comparative analysis of mortar performance using different ratios of lime putty in mortar mixtures.
