Key Engineering Materials Vol. 998

Abstract: In a laboratory setting under consolidation conditions, this study investigated the performance of saturated silty sand improved by stone columns. The studies were carried out with area replacement ratios of 0.03, 0.06, and 0.11, and relative soil densities of 40% and 90%. The properties of the stone column were analyzed by measuring settlement and stress distribution on the soil and column. The performance improvements are mainly due to the stiffness and high bearing capacity of silty sand under dry conditions. However, when in contact with water, there is a high risk of failure because the soil becomes saturated or partially saturated. The soil transitions from a solid to a liquid state, resulting in a loss of strength and stiffness under applied vertical pressure. The test results displayed that the settlement reduction ratio of the stone column ranged from 1.12 to 2.18. The stress concentration ratio ranged from 5.04 to 6.78, and column efficacy ranged from 0.126 to 0.459. Thus, the stone column significantly improved the silty sand by decreasing settlement, increasing stress on the column-supported embankment, and reducing stress on the soil.

Abstract: The erosion problem is an issue environment, that decreases the fertility of soil surface, causing damage to farmers or on various slopes. Erosion leads to soil deposition and long-term changes in topography. This study investigates and compares the performance of geocell erosion control systems across different installation areas. The erosion experiment test under various conditions, the different geocell-installed areas, the three rainfall intensities, and the three slope gradients. The erosion characteristics were tested in a laboratory erosion flume model. The investigation shows the erosion control process of the geocell wall blocks the surface runoff flow and sediment. Geocell installation reduces runoff energy, distributes water mass, and helps retain soil particles. This study shows the performance of geocell-installed on erosion control, the cell wall of geocell reduces the flow energy and the water mass to smaller, which can decrease the erosion damage in the geocell-installed area or areas below slopes. The sediment reduction ratio of the fully geocell-installed flume test was 84% and decreased by approximately 10% with every 20% reduction in the geocell installation area.

Abstract: The aim of this study is to investigate the influence of temperature on the shear strength and elastic stiffness of sand under triaxial compression (TC) test. Air-dried Ottawa sand specimens were prepared to avoid pore pressure induced during shearing. Ottawa sand, widely used in geotechnical engineering research, was selected for these TC tests. The sample was first drained and then heated to different target temperatures (i.e., 30, 45 and 60°C), which were maintained constant during the tests. After heating, the sample was sheared under a constant cell pressure and temperature. Small strain-amplitude cyclic loading was applied successively at different shear stress levels to investigate the elastic Young’s modulus (E_eq) behaviour. The results revealed that the peak shear strength increased with increasing temperature. For E_eq values, a clear relationship with temperature was observed, indicating that elastic stiffness of Ottawa sand also increased with temperature. These findings are significant as they demonstrate that temperature variations can markedly affect the mechanical behaviour of sand, which is important for understanding and predicting the performance of geotechnical structures subjected to thermal effects. Moreover, a sudden drop of stress can be observed as a phenomenon commonly observed in round particle shapes.

Abstract: In geotechnical engineering, the enhancement of soil properties is crucial for cost-effective construction practices. This study investigates the impact of incorporating microcrystalline cellulose into styrene-butadiene emulsion modified cement-stabilized soils. The mechanical properties, including unconfined compressive strength (UCS) and indirect tensile strength (ITS), were evaluated alongside morphological analysis using scanning electron microscopy. Results indicate that the addition of microcrystalline cellulose influences the mechanical behavior of the composite material in a nuanced manner. At lower microcrystalline cellulose content (1%), an improvement in tensile strength is observed due to enhanced interfacial bonding between cellulose hydroxyl groups and styrene-butadiene emulsion surfactants. However, at higher microcrystalline cellulose content (2% and 3%), a reduction in tensile strength occurs, attributed to hindered cement hydration. Nonetheless, the incorporation of styrene-butadiene emulsion contributes to the transition from brittle to ductile behavior, enhancing toughness. Morphological analysis corroborates these findings, highlighting the complex interactions between microcrystalline cellulose, styrene-butadiene emulsion, and cement-stabilized soils. This study provides valuable insights for optimizing the mechanical performance of polymer-modified cement-stabilized soils, paving the way for the development of sustainable construction materials with improved resilience and durability.

Abstract: This study investigates the effects of microcellulose (MCC) and styrene-butadiene (SB) emulsion on the properties of cement-stabilized soil. The addition of MCC to cement-stabilized soil resulted in a reduction in hydraulic conductivity due to its water absorption properties, although it did not significantly improve mechanical properties. In contrast, SB emulsion modified cement-stabilized soil exhibited increased toughness and ductility, transitioning from brittle to ductile behavior. Interestingly, the combination of SB emulsion and MCC yielded a gradual decrease in hydraulic conductivity with increasing SB emulsion content. This was attributed to SB emulsion coating the surface of MCC particles, reducing their water absorption capacity and altering their influence on water flow through the soil-cement matrix. Overall, while MCC alone had limited impact on mechanical properties, SB emulsion showed promise for enhancing toughness and ductility. These findings underscore the importance of understanding additive interactions and their effects on the properties of cement-stabilized soil. Further research is needed to optimize additive compositions for specific engineering applications.

Abstract: Adhesive bonding is often found for engineering construction technology applications in industries such as aeronautics, automotive, electronics, and aerospace. Single lap joint type connections can be applied to dissimilar materials so that they can reduce the weight of construction. The objective of this study to determine the effects of adding natural latex adhesive to aluminum-cocofiber composites single lap joints. The research material uses two types of adherend, namely aluminum and cocofiber-reinforced composite with an Unsaturated Polyester matrix (UPRs) type Yukalac BQTN with a MEXPO catalyst. Adhesive bonding material uses epoxy resin and the addition of natural latex. The connection is carried out using a single lap joint adhesive bonding method between two different adherend materials. The adhesive material in the single lap joint is 0.2 mm thick using variations in the addition of natural latex adhesive to epoxy with variations of 5%NK: 95%EP, 15%NK: 85%EP, 25%NK: 75%EP, and 35%NK: 65%E.P. The adherend surface treatment was given by roughing the surface with sandpapering grid #150. The single lap joints shear test refers to ASTM D-1002. The test results indicated that the shear strength increases with the addition of 5% natural latex to the epoxy. The roughness treatment applied to the surface provides an irregular effect, thus increasing the bond between the adhesive and the adherend. In addition, it also improves the mechanical interlocking of the single lap joint. The failure modes after the shear stregth test that occur based on macro observations are cohesive, stock-break, thin layer cohesive, and fiber pull-out.

Abstract: Indonesia generates abundant sago pith waste (SPW) because the country is the world's largest producer of sago starch. Although many efforts and studies have been devoted to processing this waste, SPW has not been utilized properly, and a large amount of SPW remains unprocessed and thrown away. On the other hand, increasing noise levels have become a problem in Indonesia due to the rapid industrialization in recent years. In this study, SPW is tested for use as a sound-absorbing material by first converting it into composite materials. The composites were manufactured by using unsaturated polyester resin mixed with SPW particles in three different volume fractions: 20% SPW, 30% SPW, and 40% SPW. SEM micrographs were performed to observe the morphology of the SPW particles and the composites. SEM micrographs revealed honeycomb structures of the SPW, and the average diameter of dried sago starch particles was observed to be around 5 μm. Further SEM examination on the composite specimens only found pores and holes previously occupied by sago starch particles, while the honeycomb structures were difficult to find except for the specimens with 40% SPW. The acoustics tests of all composite specimens were conducted using a set of impedance tubes between 0 and 6000 Hz. The plot lines of the coefficient of sound absorption are complex, and the SPW volume fraction that produces the best coefficient is affected by the sound frequency. However, the composite specimen with 30% SPW appears to have the best overall sound absorption properties.

Abstract: The use of hemp fiber is capable of increasing the compressive and tensile strength, along with enhanced ductility in concrete. Shell ash also contains calcium compounds that improve the properties of concrete. Therefore, this study aimed to measure the compressive and tensile strengths of concrete as well as the chemical functional groups of hemp fiber. To achieve this, hemp fiber (additive) and 6% shell ash (filler) were added to the concrete mixture, targeting a design strength of 25MPa. The results showed that the average compressive strength of concrete after 28 days obtained a minimum value of 25.668MPa with 0.5% fiber and the maximum strength was 33.446MPa with 1.5% fiber. The split tensile strength test of the concrete after 28 days obtained a minimum value of 1.982MPa, and a maximum of 2.831MPa. These results showed that adding hemp fiber at approximately 1.5% to concrete improved the compressive strength by 4.74% and the split tensile strength by 3.47% compared to conventional concrete. Furthermore, the FTIR test showed that the shape of the wavelength spectrum diagram and the area of chemical bond peaks were the same among hemp, plastic, and other natural fibers.

Abstract: High-strength concretes made with a lot of cement and good quality aggregates added with additives and admixtures causing expensive costs. Conversely, cement manufacturing is not environment friendly due to using many natural raw materials and delivers CO₂ to atmosphere triggering global warming. Moreover, aggregates availability deriving from river reduces over time, almost 60% of civil engineering infrastructures in world are made with concrete. The purpose of this research is to study effectiveness of using cement substitute materials derived from natural geopolymer pozzolanic ash and aggregates substitute derived from palm oil mill waste in high-strength reinforced concrete beams. These local materials are abundantly available in nature but have not been used, which are utilized together to produce hybrid high-strength concrete. The test investigated was shear capacity of reinforced concrete beams in anticipating earthquake-prone areas of Indonesia. Hybrid reinforced concrete beams made with 10% pozzolanic ash as cement substitution, 20% palm oil blast furnace slag as fine aggregates substitution, and 40% palm oil shell chunks as coarse aggregates substitution. Dimensions of beams were 150 x 300 x 2200mm. To ensure shear failure emergence, beams were strengthened with longitudinal tensile reinforcement 4 D 18.9mm, longitudinal compression reinforcement 2 D 15.8mm, and shear reinforcement Ø 6 – 300 mm, resulting in capacity ratio of bending to shear 2.29. Results showed that hybrid high-strength reinforced concrete beam could reach 81.14% of shear capacity of plain beam without material substitutions, but compressive strength could significantly be increased by 130.54% and flexural tensile strength of 122.67% compared to plain high-strength concrete.