A common feature of most fiber plants is their similar biological composition, an organic and mineral conglomerate mainly in the form of cellulose, lignin, hemicellulose, inorganic materials, and extractive substances such as pectin, fats, wax, and other. In particular, simple sugars formed in an aqueous environment inhibit the process of hydration of the cement binder. In paper extensive laboratory tests were conducted on the effect of different types and methods of organic filler mineralization on the compressive strength of the composite. They focused on eliminating the problem related to the instability of cement composites containing organic fillers due to the presence of simple sugars. Based on the test results the authors proposed a two-stage mineralization of organic filler in cement composites. First, an extractant was selected in the form of an aluminum sulfate solution, which leaches simple sugars from the organic aggregate (mainly from its surface layers) and partially neutralizes them, and then a neutralizer was selected in the form of a calcium oxide solution, whose task is to bind carbohydrates and increase the pH of the solution from acid to alkaline. The optimal contents of aluminium sulphate and calcium oxide in relation to organic fillers were also experimentally determined. The use of two-stage mineralization of organic fillers allowed an increase of the compressive strength of composites by approximately 70%, an increase of volume density as well as significantly reducing their water absorption. This solution enables more efficient use of organic waste in building materials, which is consistent with the idea of sustainable development.

This article explores the potential and accuracy of spring–mass–damper (SMD) pedestrian load modelling strategies for assessing human-induced vibrations of in-service footbridges. To this aim, a recent SMD modelling proposal based on uncoupled single-body measures (SMD-0, in the following) is specifically used for the calibration of key input parameters. Finite element numerical assumptions and findings are robustly supported by original experimental tests carried out on a case-study footbridge in Poland, proving that the proposed approach can serve as an effective tool for analysing vibrations in pedestrian systems. The research study, most importantly, integrates theoretical modelling with empirical and experimental validations, to enhance the credibility of the obtained results, as well as to support the general applicability of the presented methodology. Complex in-field tests are in fact conducted on the selected footbridge, aiming to assess the effects of pedestrians on its dynamic response. Numerical analyses, which are successively performed in ABAQUS/Standard, for a set of examined walking configurations, confirm the high sensitivity of the footbridge to resonance, which was also observed during the in-field tests. The presently used SMD-0 approach is further assessed towards past SMD literature proposals. As shown, the comparison of standard structural performance indicators (such as the peak acceleration value, root mean square and CREST factor) reveals a significant sensitivity of the footbridge response to the input parameters for the analyzed SMD models. Besides, the presently addressed SMD-0 model has the advantage of being based on single-body sensor measurements and its calibration is not affected by structural features. As such, potential applications of present findings could include the improvement of design standards and safety measures for similar structures.

Over the past few decades, the demand for retrofitting reinforced concrete members has risen dramatically. Retrofitting reinforced concrete slabs with carbon-fiber-reinforced polymer (CFRP) rods and ultra-high-performance-fiber-reinforced-concrete (UHPFRC) jackets is the one of significantly effective techniques. However, the main challenge of employing CFRP rods and UHPFRC jackets technique to strengthen existing reinforced concrete members is the efficiency of using CFRP rods and the debonding issue between old and fresh new concrete jacketing. Debonding mostly occurs between CFRP rods and old concrete, as well as the surfaces of old and new concrete, and is especially prevalent when the slab is subjected to daily repetitive loads such as cyclic loads. In this study, a new retrofitting system utilizing a mechanical anchor system was proposed to improve the bond between the UHPFRC layer and existing slab. This mechanical system incorporates an expandable anchorage bolt and steel plates. Therefore, a benchmark RC slab and two retrofitted RC slabs were experimentally tested under a five-point incremental repeated load (cyclic load) employing the dynamic actuator. The influence of embedded CFRP rods into the jacket of UHPFRC on the performance of system were studied. The experimental results showed that the newly proposed approach was significantly effective in preventing early debonding. In addition, the mechanical system played an essential role by improving the attachment between the jacket and the slab, ensuring better load transfer. A new proposed retrofitting technique improved the capacity of slabs from 164 to 298kN, illustrating an improvement of over 82%. On the other hand, the FE models have been developed to provide both practical validation and deeper analytical insights, ensuring a comprehensive evaluation of the proposed retrofitting system. Experimental data were used to validate the results of the finite-element models, which showed good agreement and high accuracy. Finally, a parametric study was executed to evaluate the impact of various parameters on the performance and efficacy of the new suggested strengthening technique, and to optimize the proposed system parameters, including the diameter of bolts, a normal strength concrete (NSC) jacket with various grades rather than the UHPFRC, applying the proposed retrofitting technique on a compressive side instead of a tension zone, and rebar steel of varying diameters in the jacket instead of CFRP rods. Findings indicated (parametric study) that using anchor bolts with a diameter greater than 12 mm improved the slabs’ ultimate load capacity.