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This paper presents experimental results regarding the efficiency of using acoustic panels made with fiber-reinforced alkali-activated slag foam concrete containing lightweight recycled aggregates produced by using Petrit-T (tunnel kiln slag). In the first stage, 72 acoustic panels with dimension 500 × 500 × 35 mm were cast and prepared. The mechanical properties of the panels were then assessed in terms of their compressive and flexural strengths. Moreover, the durability properties of acoustic panels were studied using harsh conditions (freeze/thaw and carbonation tests). The efficiency of the lightweight panels was also assessed in terms of thermal properties. In the second stage, 50 acoustic panels were used to cover the floor area in a reverberation room. The acoustic absorption in diffuse field conditions was measured, and the interrupted random noise source method was used to record the sound pressure decay rate over time. Moreover, the acoustic properties of the panels were separately assessed by impedance tubes and airflow resistivity measurements. The recorded results from these two sound absorption evaluations were compared. Additionally, a comparative study was presented on the results of impedance tube measurements to compare the influence of casting volumes (large and small scales) on the sound absorption of the acoustic panels. In the last stage, a comparative study was implemented to clarify the effects of harsh conditions on the sound absorption of the acoustic panels. The results showed that casting scale had great impacts on the mechanical and physical properties. Additionally, it was revealed that harsh conditions improved the sound properties of acoustic panels due to their effects on the porous structure of materials.

The growth of global construction has contributed to an inevitable increase in the amount of construction and demolition (C&D) waste, and the recycling of C&D waste as aggregates in concrete is receiving increased interest, resulting in less demand for normal aggregates and bringing a potential solution for the landfilling of wastes. Recently, several studies have focused on the use of C&D waste in alkali-activated concrete to move one step closer to sustainable concretes. This paper focuses on the main mechanisms of using C&D waste in the resulting physical, mechanical, and durability properties of alkali-activated concrete in fresh and hardened state properties. The main difficulties observed with recycled aggregates (RA) in concrete, such as high levels of water demand, porous structure, and low mechanical strength, occur in RA alkali-activated concretes. These are associated with the highly porous nature and defects of RA. However, the high calcium concentration of RA affects the binder gel products, accelerates the hardening rate of the concrete, and reduces the flowability of alkali-activated concretes. For this reason, several techniques have been investigated for modifying the water content and workability of the fresh matrix and for treating RA and RA/alkali-activated binder interactions to produce more sustainable alkali-activated concretes.

This experimental study aimed to develop a fiber-reinforced lightweight mineral wool-based alkali activated mortar. The lightweight mineral wool-based alkali activated mortars were produced using premade foam and reinforced by polypropylene (PP) fibers. They were assessed in terms of fresh and hardened-state properties. Fresh-state properties were investigated by mini-slump tests. Hardened-state characteristics were assessed by ultrasonic pulse velocity, dry density, compressive and flexural strengths, drying shrinkage, efflorescence, water absorption, and permeable porosity. For the first time, the resistance of the synthesized lightweight mineral wool-based alkali activated mortars against harsh conditions (carbonation, freeze and thaw, and high temperature) were evaluated. The porous structures of the developed lightweight alkali activated mortars were also analyzed using an X-ray micro-computed tomography (CT) technique. Lightweight mix compositions with densities in a range of 770–1510 kg/m3, compressive strengths of 1–9 MPa, and flexural strengths of 2.6–8 MPa were developed. Increases in both density and strength after carbonation were also recorded, while a decrease of strength was noticed after exposure to freeze/thaw and high temperatures of up to 500 °C.

This experimental study aimed to develop alkali-activated concretes containing carbonated basic oxygen furnace (BOF) slag aggregates. In the first stage, the impacts of replacing normal aggregates with carbonated BOF slag aggregates in different alkali-activated concretes were determined by assessing mechanical properties (compressive and flexural strengths), morphology, thermogravimetric analyses (TGA), differential thermogravimetry (DTG) and the crystalline phases using X-ray diffraction analysis. Second, the developed plain alkali-activated concrete was reinforced by different fibre types and dosages to limit the negative impacts of the drying shrinkage and to improve strength. Therefore, the effects of using different fibre contents (1% and 1.5% in Vol.) and types (Polyvinyl alcohol [PVA], Polypropylene [PP], basalt, cellulose and indented short-length steel) on hardened state properties were evaluated. These evaluations were expressed in terms of the compressive and flexural strengths, ultrasonic pulse velocity, mass changes, drying shrinkage and efflorescence. Then, the impacts of aggressive conditions on the hardened properties of fibre-reinforced alkali-activated concretes were evaluated under carbonation, high temperature and freeze/thaw tests. The results showed that using carbonated BOF slag aggregates led to obtain higher strength than using normal aggregates in alkali activated concretes. Moreover, the maximum enhancement due to reinforcing the mixtures was recorded in alkali-activated concretes with steel fibres.

Belitic calcium sulfoaluminate (BCSA) cement is a sustainable alternative to Portland cement that offers rapid setting characteristics that could accelerate throughput in precast concrete operations. BCSA cements have lower carbon footprint, embodied energy, and natural resource consumption than Portland cement. However, these benefits are not often utilized in structural members due to lack of specifications and perceived logistical challenges. This paper evaluates the performance of a full-scale precast, prestressed voided deck slab bridge girder made with BCSA cement concrete. The rapid-set properties of BCSA cement allowed the initial concrete compressive strength to reach the required 4300 psi release strength at 6.5 h after casting. Prestress losses were monitored long-term using vibrating wire strain gages cast into the concrete at the level of the prestressing strands and the data were compared to the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) predicted prestress losses. AASHTO methods for prestress loss calculation were overestimated compared to the vibrating wire strain gage data. Material testing was performed to quantify material properties including compressive strength, tensile strength, static and dynamic elastic modulus, creep, and drying and autogenous shrinkage. The material testing results were compared to AASHTO predictions for creep and shrinkage losses. The bridge girder was tested at mid-span and at a distance of 1.25 times the depth of the beam (1.25d) from the face of the support until failure. Mid-span testing consisted of a crack reopening test to solve for the effective prestress in the girder and a flexural test until failure. The crack reopen effective prestress was compared to the AASHTO prediction and AASHTO appeared to be effective in predicting losses based on the crack reopen data. The mid-span failure was a shear failure, well predicted by AASHTO LRFD. The 1.25d test resulted in a bond failure, but nearly developed based on a moment curvature estimate indicating the AASHTO bond model was conservative.

Alternative cementitious binders, based on industrial side streams, characterized by a low carbon footprint, are profitably proposed to partially replace Portland cement. Among these alternatives, alkali-activated materials have attracted attention as a promising cementitious binder. In this paper, the chemical stability of the matrix, in fiber-reinforced slag-based alkali-activated composites, was studied, in order to assess any possible effect of the presence of the reinforcement on the chemistry of polycondensation. For this purpose, organic fiber, cellulose, and an inorganic fiber, basalt, were chosen, showing a different behavior in the alkaline media that was used to activate the slag fine powders. The novelty of the paper is the study of consolidation by means of chemical measurements, more than from the mechanical point of view. The evaluation of the chemical behavior of the starting slag in NaOH, indeed, was preparatory to the understanding of the consolidation degree in the alkali-activated composites. The reactivity of alkali-activated composites was studied in water (integrity test, normed leaching test, pH and ionic conductivity), and acids (leaching in acetic acid and HCl attack). The presence of fibers does not favor nor hinder the geopolymerization process, even if an increase in the ionic conductivity in samples containing fibers leads to the hypothesis that samples with fibers are less consolidated, or that fiber dissolution contributes to the conductivity values. The amorphous fraction was enriched in silicon after HCl attack, but the structure was not completely dissolved, and the presence of an amorphous phase is confirmed (C–S–H gel). Basalt fibers partly dissolved in the alkaline environment, leading to the formation of a C–N–A–S–H gel surrounding the fibers. In contrast, cellulose fiber remained stable in both acidic and alkaline conditions.

In this study, a new generation of composite sandwich slab is proposed as a solution for the rehabilitation of slabs in old masonry buildings. The innovative solution proposed includes four components: a Deflection Hardening Cement Composite (DHCC) layer on the top compression skin, a glass fiber reinforced polymer (GFRP) skin at the bottom tension surface, GFRP ribs to transfer shear from top to bottom layers, and foam core for thermal-insulation purposes. The DHCC layer contributes to the load carrying and deflection capacity due to its high stiffness, compressive strength and toughness. It also offers resistance to the occurrence of buckling phenomena in the GFRP ribs, improves the performance of this structural concept against impact and fire, and constitutes an excellent medium for the application of finishing materials, like ceramics or timber. To evaluate the efficiency of the developed innovative slabs, different composite specimens, with various span lengths, were tested under different load conditions, including flexural loading, shear loading, and long term deformation. The obtained results from experimental tests are comprehensively analysed. Advanced numerical simulations on the hybrid slabs are also developed. The influence of considering isotropic or orthotropic behaviour for the GFRP components and linear or nonlinear behaviour for the DHCC is investigated numerically. The results obtained during the experimental tests are used to appraise the performance of the constitutive models adopted in the FEM-based simulations and the quality of the meshes defined. In addition, some analytical models that consider the relation between force and deflection are proposed to evaluate the response of this structural system under static and long-term loadings.

Background Exercise-induced muscle damage typically caused by unaccustomed exercise results in pain, soreness, inflammation, and muscle and liver damages. Antioxidant supplementation might be a useful approach to reduce myocytes and hepatocytes damages. Therefore, the present study was conducted to investigate the effect of short-term vitamin D (Vit D) supplementation on the response to muscle and liver damages indices by Exhaustive Aerobic Exercise (EAE) in untrained men. Methods In this clinical trial, 24 untrained men were randomly divided into experimental (Exp; n = 12) and control (C; n = 12) groups. Exp received 2000 IU of Vit D daily for six weeks (42 days), while C daily received a lactose placebo with the same color, shape, and warmth percentage. Two bouts of EAE were performed on a treadmill before and after six weeks of supplementation. Anthropometric characteristics (Bodyweight (BW), height, Body Fat Percentage (BFP), Body Mass Index (BMI), waist to hip ratio (WHR)) were measured at the Pre 1 and Pre 2. Blood samples were taken to measure the Creatine Kinase (CK), Lactate Dehydrogenase (LDH), Aspartate Aminotransferase (AST), Alanine Aminotransferase (ALT), Gamma-Glutamyl Transferase (GGT), Alkaline Phosphatase (ALP), and Vit D levels at four stages: Pre 1 (before the first EE session), Post 1 (after the first EE session), Pre 2 (before the second EE session), and Post 2 (after the second EE session). The data were analyzed using repeated-measures ANOVA, Bonferroni's post hoc test, independent t test, and dependent t-test at the significant level of P  < 0.05 using SPSS version 26. Results The results show significant differences between Exp and C in alterations of BW ( P  = 0.039), BMI ( P  = 0.025), BFP ( P  = 0.043), and WHR ( P  = 0.035). The results showed that EAE increased muscle and liver damage indices and Vit D ( P  < 0.05). Compared with C, the results of the independent t-test showed significantly lower ALT ( P  = 0.001; P  = 0.001), AST ( P  = 0.011; P  = 0.001), GGT ( P  = 0.018; P  = 0.001), and ALP ( P  = 0.001; P  = 0.001); while significantly higher Vit D ( P  = 0.001, P  = 0.001) in the Exp in both Pre 2 and Post 2; receptivity. The independent t test showed significantly lower ALT ( P  = 0.001; P  = 0.001), AST ( P  = 0.011; P  = 0.001), GGT ( P  = 0.018; P  = 0.001), and ALP ( P  = 0.001; P  = 0.001) and considerably greater Vit D ( P  = 0.001, P  = 0.001) in the Exp in both Pre 2 and Post 2 compared to C. The results of an independent t test showed that LDH and CK levels in the Exp were significantly lower than those in the Post 2 ( P  = 0.001). Conclusions Short-term Vit D supplementation could prevent myocytes and hepatocytes damage induced by EAE.