Key Engineering Materials Vol. 1028

Abstract: Relative humidity (RH) can have a significant impact on bamboo products, leading to issues such as swelling, shrinking, and even cracking. Unfortunately, these effects are often difficult to detect in bamboo bundles. This research aims to investigate how RH affects the moisture expansion coefficient (β) of bamboo bundles. Samples from the stem of the Dendrocalamus genus were dried in an oven at 105 °C until they reached a stable weight. The samples were then hand-pulled and cut to create cross-sections with areas ranging from 0.06 mm² to 0.09 mm² and a length of 60 mm. The expansion coefficient of the bamboo bundles was measured using a tensile test, following the ASTM D3379 standard. This was conducted at a constant temperature of 27 °C and a force of 10 N in a controlled chamber with RH levels between 50% and 85% for a full day, with five replicates for accuracy. The results indicate that the strain in bamboo bundles is influenced by both relative humidity (RH) and tensile load. When the RH ranges from 85% to 50%, the bamboo bundles tend to stretch under tensile load. However, when the RH drops to 50% without tensile load, the bundles can return to their original shape. This suggests that while the initial changes in strain may be small, bamboo bundles gradually experience increased strain over time, and prolonged use could result in more significant alterations. Another important factor to consider when using bamboo bundles is the effect of changes in relative humidity (ΔRH) on the average value of β. Indeed, bamboo bundles need time to absorb or release moisture as the surrounding environment changes. The average value of β tends to decrease dramatically in an exponential decay pattern. When ΔRH exceeds 5% in both charge and discharge conditions, the average value of β can be considered equal and constant, as it becomes extremely small and negligible. However, at ΔRH levels higher than 20%, the average value of β converges to 1.5 x 10-4 (%RH)-1, indicating that the bamboo bundles have already adapted to the surrounding humidity. Therefore, it is crucial to carefully assess application areas with rapid humidity fluctuations when using bamboo bundles to prevent potential damage during use.

Abstract: Bamboo can be used for a variety of purposes, whether using the bamboo culm in structures works or using bamboo bundle or bamboo fibers as a reinforcement in composite materials. However, the critical item that should be considered when using bamboo materials is the humidity condition of the environment. The influence of humidity on the mechanical properties of bamboo materials can potentially lead to damage or degradation. The objective of this research is to investigate the influence of relative humidity (RH) on elastic modulus of bamboo bundle. In this research, 3 years old Dendrocalamus bamboo stem at 3-6 m in height without node was used to prepare the bundle samples. The bamboo stem was dried in the oven at 105 °C then hand pulled and cut to get the bamboo bundle with 30 mm in gage length and 0.06-0.09 mm² in cross-section areas. The elastic modulus of bamboo bundles was determined according to ASTM D3379 standard under 8 different relative humidity; 30%, 35%, 50%, 55%, 70%, 75%, 80%, and 85% RH, whereas paper grips technique was applied to prevent damage from the machine clamps. The results indicated that the relative humidity does not affect the value of the loaded or unloaded elastic modulus of bamboo fiber bundle. For the low value of relative humidity, here 35%-55%, the value of elastic modulus of bamboo bundle is quasi-stable with the RH with the average value 25.93 GPa while the elastic modulus was gradually decreased for the high value of RH (>70%) with the minimum value of 24.43 GPa at 85% RH. Implying at high humidity condition, the humidity or the amount of water vapor in the air affects to the bamboo bundle be softened or more flexible, which helps the process of bending or forming bamboo bundles easier.

Abstract: The urban surface contains a large amount of asphalt concrete pavement, which is also one of the main causes of the urban heat island effect. This study aims to explore the effect of BOFS on radiative cooling when applied to asphalt concrete pavement, and to review it as strategies to mitigate the urban heat island effect. This study chooses the density grading certified by TAF commonly used by road design units at present. Setting up thermometers on the actual construction site, the temperature of each layer would be measured. It is hoped that through comparison at actual on-site paving of BOFS pellets and natural pellets, the difference in effectiveness in radiant cooling can be evaluated. The results show that BOFS pellets for road paving have significant potential for radiative cooling.

Abstract: The article examines the physical-chemical features of the formation of the garnish on the lining of rotary kilns for firing cement clinker, the functional necessity of the garnish and the material science difficulties for its creation when developing new types of refractories, which solves the problem of the formation of Cr(VI) compounds in Portland cement. Thus, the analyzed problem of the formation of Cr(VI) compounds in Portland cements that are dangerous for the biocenosis and humans is the result of scientific and technological progress, the pursuit of leading manufacturers for the recycling of secondary raw materials and energy resources. At the same time, the timeliness of identifying the problem and its proactive, comprehensive solution with state support give a new impetus to the scientific and technical development of not only cement, but also related enterprises and scientific organizations. In Ukraine, the problem has been solved only in relation to the development and experimental testing of a new type of refractory material to replace magnesia-chromite for lining high-temperature zones of rotary kilns for firing cement clinker.

Abstract: The aim of the work was to determine the possibility of not taking into account the orientation (vertical or horizontal) of the studied elements of steel-reinforced concrete slabs with a corrugated profile during their heating in a modular small-sized fire furnace. The work investigated the temperature distributions on the outer surface of the corrugated ceiling profile of a steel-reinforced concrete slab of horizontal orientation simulated in the fire furnace chamber. To create geometric models of the fire furnace chamber and the studied element, a CAD software complex was used. To solve the heat engineering problem, mathematical (numerical) methods were used, based on solving systems of differential equations of continuous media such as the Navier-Stokes equation and the Fourier heat conductivity equation. According to the results obtained, the temperature distribution on the outer surface of the steel profile of the reinforced concrete slab is uniform, the temperature deviation in different places on the surface does not exceed 7 %. The maximum temperature on the heating surface of the steel profile of the reinforced concrete slab in the last minute of computer simulation reached 921 °С and the average temperature at this time over the entire surface of the structure was 917 °С. To determine the appropriate orientation of the test sample during fire tests, a comparison of the obtained temperature distributions on the outer surface of the corrugated profile of a horizontally placed reinforced concrete slab with the temperature distributions on the outer surface of the corrugated profile of a vertically placed reinforced concrete slab, which were given in the previous work was made. Analysis of the average surface temperatures of the corrugated profile of a reinforced concrete slab of horizontal and vertical orientation showed that the temperature distribution over the surface of the profile was uniform in both cases and the results obtained show good reproducibility of the experiment during computer simulation. And the orientation of the tested elements does not affect the temperature distribution over the outer surface of the corrugated profile of a reinforced concrete slab in the simulated furnace.

Abstract: The article presents and describes the methodology for determining the fire resistance limit state of loaded thermally stressed steel floor beams. The article describes the methodology for taking into account the uneven temperature distribution along the height of the cross-section of a fireproofed steel floor beam. The author presents a method for refining the stiffness characteristics of an I-beam after exposure to high temperatures from a fire and compares the results with the results of field tests.

Abstract: This study investigates the impact of high temperatures on the structural and physico-chemical properties of concrete, emphasizing the degradation of material strength under fire exposure. Through a review of reference data, it was confirmed that elevated temperatures significantly reduce concrete strength, potentially leading to structural failure. The rebound hammer method, a mechanical non-destructive testing technique, was selected for on-site evaluation due to its accessibility, speed, and ability to provide immediate preliminary results. Field measurements conducted at fire-affected sites allowed for the identification of temperature zones and heat flow directions based on variations in concrete strength. Comparative analysis between intact and damaged areas enabled the identification of critically affected zones and the estimation of structural degradation. The study demonstrates that using the Schmidt hammer, with proper calibration and error consideration, provides reliable data for determining the origin of the fire and for making informed decisions on structural repair or reinforcement.

Abstract: This study aims to develop an innovative natural rubber latex foam (NRLF) composite by incorporating coconut shell activated carbon (Ac) and 2% copper-modified Ac (2%Cu/Ac). The NRLF was prepared using the Dunlop process and mixed with Ac and 2%Cu/Ac at concentrations of 0, 5, and 10 phr. The mechanical properties, morphology, crosslink density, and cadmium ion adsorption performance were investigated. SEM analysis revealed that the additives improved the stability of the foam’s open-cell structure. The results demonstrated that copper particles deposited on Ac enhanced the overall properties of the NRLF composite. The mechanical strength at 50% strain increased significantly, from 5.81 mN/m² for neat NRLF to 12.81 mN/m² with the incorporation of 10 phr 2%Cu/Ac. Crosslink density also improved with the addition of Ac and further increased with Cu-modified Ac. In terms of cadmium adsorption, the optimal performance was achieved with 5 phr 2%Cu/Ac, yielding an adsorption capacity of 0.89 mg/g. These findings highlight the potential of 2%Cu/Ac as a superior additive for enhancing the Cadmium adsorption and the performance of NRLF composites.

Abstract: Waste frying oil (WFO) is a major byproduct of food preparation, containing elevated levels of free fatty acids (FFA), which reduce its potential for reuse in biodiesel production and other applications. This study investigates the use of hydrochloric acid (HCl)-pretreated rice husk ash (RHA) as an adsorbent for removing FFAs, with lauric acid as a model FFA. RHA pre-treated with different HCl concentrations (1 – 5 M) was synthesized and characterized using SEM-EDS and FTIR. SEM analysis revealed that acid treatment improved surface roughness and porosity, while EDS confirmed an increase in silica content, particularly in RHA treated with 4M HCl. FTIR identified key functional groups that contributed to FFA adsorption. Batch adsorption experiments demonstrated the effect of HCl concentration, adsorbent dosage, and initial FFA concentration on adsorption capacity and removal efficiency. The study shows that acid pre-treatment enhances RHA's adsorption properties, offering a potential solution for the sustainable management of WFO and improving its applicability in purification processes.