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In this study researchers investigated the influence of fineness of locally available basaltic volcanic ash (VA) and its blend with other potential supplementary cementitious materials (SCMs) on compressive strength of mortar. Local quarry sites and steel making industries in the eastern province of Saudi Arabia produces tons of wastes commonly known as quarry dust (QD) and electric arc furnace slag (EAFS), respectively. Including the CM, a total of 19 mortar mixtures were prepared by substituting cement with various SCMs (VA, FA, QD, EAFS), their different percentages in binary mixes, fineness of VA, and blends of ultra-fine VA with other SCMs (ternary and quaternary). After casting, specimens were subjected to different curing temperature (20, 40, and 60 °C) and moisture conditions (continuous and partially moist). Compressive strength was measured according to ASTM C 109 at ages 7, 28, and 91 days and an average value of three identical 50-mm 3 specimens was reported. The test results indicated that improved fineness of VA up to 30% mass replacement of cement demonstrated compressive strength comparable to control and reference FA mortars at all ages particularly under high curing temperatures. Moreover, a quaternary blend of ultra-fine VA (20%) with EAFS (10%) and QD (10%) produced strength higher than all other ternary and quaternary blends at all ages and comparable 91 days strength to control mortar. [ABSTRACT FROM AUTHOR]

This research focuses on the development and evaluation of heavy density concrete (HDC) for radiation shielding, utilizing both experimental and machine learning techniques. Various HDC specimens with different proportions (25 %, 50 %, 75 %, and 100 %) of grit iron aggregate replacing normal weight aggregate, in addition to control specimens with no grit iron scale aggregate, were cast. These samples were subjected to testing at temperatures ranging from room temperature to 1200°C to assess properties such as compressive strength, rebound number, ultrasonic pulse velocity, density loss, mass loss, linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP). Ensemble learning algorithms were employed using experimental data to predict compressive strength and new empirical expressions were formulated for mechanical and radiation shielding properties, including LAC, HVL, and TVL. The addition of grit iron aggregate, combined with MgO, demonstrated a significant improvement in the mechanical and radiation shielding properties of HDC. This research holds promise for applications in nuclear reactors operating at high temperatures. • Development of Heavy-Density Concrete (HDC) containing MgO and grit-scale iron aggregate (0 %, 25 %, 75 %, and 100 %). • Investigation of the mechanical and radiation shielding properties of HDC at temperatures up to 1200°C. • Formulation of empirical expressions for mechanical and radiation shielding properties using Ensemble learning algorithms. • The developed concrete can be utilized for radiation shielding across a range of temperatures. [ABSTRACT FROM AUTHOR]

• The influence of eggshell powder on 90-day compressive strength cement mortar was explored. • The response of cement mortar modified with treated eggshell powder under an acidic environment was studied. • The incorporation of eggshell powder improved the resistance of cement mortar to acid attack. • The developed machine learning models exhibited good agreement with the test results. The effectiveness of cementitious composites in an aggressive environment is the primary issue since their performance deteriorates when exposed to harmful elements. Also, to promote sustainable building materials, waste materials are gaining popularity. This work employed testing followed by machine learning (ML) modeling to study the impact of eggshell powder (ESP) in cement mortar exposed to an acidic environment. The ESP was used to partially replace cement and sand, and the samples were subjected to a 5% H 2 SO 4 solution. The dataset obtained through experimentation was utilized to construct ML-based predictive models for the reduction in compressive strength (CS) of cement mortar. According to the test results, the integration of ESP controlled the loss of cement mortar when used at lower substitutional levels. The lowest reduction in CS was seen when ESP was used as a cement substitute of 5%, which was up to 7.71% lower, and as a sand substitute of 7.5%, which was up to 7.03% lower than the same mix placed in plain water as a reference. Furthermore, the developed ML models exhibited a satisfactory level of concurrence with the experimental findings, thereby indicating their potential applicability in assessing the CS reduction percentage in cement mortar that incorporates ESP subsequent to an acid attack. [ABSTRACT FROM AUTHOR]

Current research work presents the seismic response of brick masonry houses retrofitted by different composite materials under dynamic shake table tests. Tests were performed on 1:4 scaled unreinforced masonry (URM), Polypropylene (PP-band) retrofitted, Glass Fiber Reinforced Polymer (FRP) retrofitted and FRP + PP-band retrofitted house models. A minimum reinforcement ratio of FRP was selected to use with PP-band as FRP + PP-band composite. Results show that URM is highly brittle and can hardly withstand an ordinary ground motion, whereas PP-band retrofitting has increased the ability of URM houses to withstand a severe ground motion with intense cracking and separation of wall segments. However, despite no collapses, PP-band retrofitted house model had lost its serviceability when subjected to strong input ground motion. Unlike PP-band, FRP retrofitted houses were collapsed suddenly without giving any warning with respect to ductility and energy dissipation. The sudden failure of FRP houses is attributed to very low FRP reinforcement ratio (0.0006), as it is an expensive material and its sole use in higher amounts would result in significant increase of retrofitting costs. Results show that a potential use of FRP in combination with PP-band is a good alternative as it significantly enhances the shear capacity, energy dissipation as well as the ductility of URM masonry structure at a very low retrofitting costs. [ABSTRACT FROM AUTHOR]

Highlights: [•] We described actual restraint and temperature conditions via stress device in mass concrete. [•] We obtained consistent results in construction site and indoor stress device. [•] We could reasonably predict the internal stress due to hydration heat in mass concrete. [•] Stress device could facilitate the prediction of hydration-induced stress in mass concrete. [Copyright &y& Elsevier]

Abstract: To accurately estimate the temperature effects on autogenous shrinkage of concrete, a new prediction model based on time–temperature dependent activation energy is proposed in this study. For this purpose, a series of autogenous shrinkage tests are performed considering different water to cementitious materials ratios and curing temperatures. Results revealed that the temperature dependency of autogenous shrinkage cannot be described solely by the simple time shift of the existing maturity method. In particular, maturity cannot incorporate the cross-over effect of autogenous shrinkage by which later age autogenous shrinkage of concrete, subjected to low curing temperature, usually exceeds the autogenous shrinkage of concrete subjected to relatively high curing temperature. Therefore, to overcome the shortcomings of the maturity method, a new prediction model based on time–temperature dependent activation energy is proposed. Reasonably good agreement is observed between experimental and predicted autogenous shrinkage, thus indicating that the proposed prediction model can be successfully used to estimate the time–temperature effects in the development of autogenous shrinkage. However, the absolute value of autogenous shrinkage strain still cannot be obtained from the proposed model, because the model gives only the development of autogenous shrinkage. Therefore, a prediction model for the absolute value of autogenous shrinkage is needed in order to obtain predicted autogenous shrinkage strain. [Copyright &y& Elsevier]

• Development of Heavy-Density Concrete (HDC) containing MgO and grit-scale iron aggregate. • Mechanical and radiation shielding properties of HDC at different temperatures. • Grit iron scale aggregate variations (0 %, 25%, 75% and 100%). • The developed concrete can be used for radiation shielding at various temperatures. This research focuses on the development and evaluation of heavy-density concrete containing Magnesium oxide and grit scale iron aggregate as potential radiation shielding material for water cooled reactors operating at temperatures between 28 °C and 300 °C. Concrete samples were prepared using varying proportions of grit iron scale aggregate (25 %, 50 %, 75 % and 100 %) along with a reference sample of normal weight concrete without grit iron scale. Various physical properties and characteristics such as fresh density, hardened density, compressive strength, X-ray radiography, Rebound hammer, Ultrasonic pulse velocity, Scanning electron microscopy, attenuation coefficients, half-value layer, tenth-value layers and mean free path of the concrete samples were investigated before and after exposure to various temperatures. The findings revealed a substantial enhancement in the radiation shielding effectiveness and overall concrete properties when grit iron scale was incorporated in combination with MgO, compared to the concrete samples without MgO. [ABSTRACT FROM AUTHOR]

[Display omitted] • Formulation of one-part alkali-activated material based on the fly and hydraulic lime as main precursors. • Prediction modeling of compressive strength, yield stress, and plastic viscosity by using GEP algorithms. • Evaluation of the impact of each ingredient on compressive strength, plastic viscosity, and yield stress of AAM-developed specimens. • SHAP analysis for the interpretation of the GEP algorithm by sensitivity and impact analysis. One-part alkali-activated material (AAM) is a new eco-friendly developed low-carbon binder that utilizes alkaline activators in solid form. This study deals with the experimental synthesis of one-part alkali-activated mortar (AAM) based on the partial replacement of fly ash (FA) with hydraulic lime (LM) as a precursor, and machine learning-based gene expression modeling (GEP) modeling for the optimization of the developed AAM. The datasets were established by the experimental work performed during this current study. The chosen input parameters were fly ash, hydraulic lime, sodium silicate, sodium hydroxide, sand/binder, water/binder, curing age, and time after mixing. The experimental results showed greater compressive strength and rheological parameters for the specimens having a high quantity of hydraulic lime. The GEP model has shown a strong generalization capability and prediction capacity for the future estimation of compressive strength, plastic viscosity, and yield strength. All the models showed a strong correlation of 0.92, 0.89, and 0.96 for compressive strength, plastic viscosity, and yield stress respectively. SHapely Additive exPlanations (SHAP) were employed to explore the effect of each input parameter of AAM on the predicted outcomes. The results revealed a strong interaction and positive effect of LM on the YS and PV while a negative impact was observed for the compressive strength. While fly ash has shown a negative impact on three outcomes of PV, YS, and CS respectively. The addition of LM and SS-activator leads to earlier structural build-up due to the flocculation of particles caused by the faster geopolymerization reactions. [ABSTRACT FROM AUTHOR]

• Micro silica extracted from RHA (EMS) possessed very high fineness and reactivity. • Addition of EMS increases strength and decreases porosity of the mortar samples. • Incorporation of EMS to mortar bar samples showed better resistance to ASR. • EMS improved both micro and pore structure due to its high fineness and reactivity. Utilization of high-performance and highly reactive sustainable materials in concrete are gaining popularity nowadays for the development of strong, durable and sustainable infrastructures. Therefore, current study focuses on viable use of highly reactive silica extracted from rice husk ash (RHA) for the production of high-performance sustainable cement mortar. Mortar containing various percentages of extracted micro-silica (EMS) as a partial substitute of cement (5%, 15%, and 25%) were cast to test fresh as well as hardened properties, and compare its results to that of control mortar. Test results showed that the standard consistency increased with increasing percentage of EMS, whereas, a delay in the setting time was observed. The compressive and flexural strengths of all mortar mixes containing EMS were improved with aging and an effective role played by EMS in mitigating the expansion caused by the alkali–silica reaction was observed. However, a slight reduction of strength at later ages was observed in mortar having 25% EMS. At relatively low addition of EMS (5% and 15%), micro- and pore structural investigations revealed the formation of improved high-density C-S-H phases, which aid the formation of refined and homogenous microstructures. The agglomeration was observed through micro- and pore structural investigations in high dosage EMS mortars that occurred due to the oversaturation and poor dispersion, which consequently affected the hydration products and increased the porosity of the paste matrix. The current findings suggest that the reactive silica resource extracted from RHA can be used as a potential revenue stream in concrete industry for the development of high-performance and sustainable cement mortar. [ABSTRACT FROM AUTHOR]