Key Engineering Materials Vol. 1000

Abstract: Recently, a lot of research has been developed to determine the usefulness of mortar mixed with rubber tire crumbs, which is often called RTC mortar. The advantages of RTC mortar are that it is lighter, more ductile, and has better damping capabilities than ordinary mortar. However, RTC mortar has a weakness, namely its low compressive strength. Several studies have added fly ash to RTC mortar, and it is known to increase the compressive strength of the mortar. This research aims to determine the diagonal shear strength of masonry walls if the mortar joints use RTC mortar with the addition of fly ash. Laboratory testing uses 1⁄2 brick masonry wall test specimens measuring 300x300 mm² which are composed of clay bricks and mortar joints referring to ASTM E519-02. The research results show that the addition of fly ash to RTC mortar can increase the compressive strength of the mortar, but results in the shear strength of the masonry wall decreasing. To use RTC mortar mixed with fly ash as mortar joints in masonry walls, additional materials need to be considered to increase the bond strength between the mortar and the brick. The effect of adding fly ash to RTC mortar on the bond strength between the mortar and bricks needs to be investigated further.

Abstract: Seawater has the potential to replace fresh water in the production of concrete. Given the restricted availability of freshwater sources and the high cost of transportation, it is crucial to optimize this scenario. On the other hand, agricultural residue is a potential material that can replace cement-based materials, thereby reducing CO2 emissions. Sustainability in the concrete sector is important, hence, research on using alternative renewable resources such as palm oil fuel ash (POFA) for concrete production is necessary. POFA is an agricultural byproduct and industrial waste that is potentially used as a partial substitution for cement due to the presence of pozzolan. The objective of this study is to examine the impact of icluding POFA (Palm Oil Fuel Ash) as a substitute in the paving block, while also considering the influence of seawater mixing and curing water. Further, POFA is used as a supplementary binder for paving blocks at 0%, 10%, 20%, 30%, 40%, and 50% for Portland Composite Cement replacement. The paving blocks properties, such as workability, density, compressive strength, water absorption, and resistance to sulfate attack, were evaluated. The results of the tests confirmed that 10% POFA mixed with seawater and cured with freshwater met the minimum necessity for Class B, as specified by the Indonesian National Standard for parking park applications. As a result of incorporating POFA as a cement replacement, a more environmentally friendly paving block could be established.

Abstract: Fly ash is a solid waste produced by power plants. To overcome the bad effects on the environment, fly ash is used as a substitute for cement in making concrete. Apart from that, the innovation of aggregate replacement materials in mixing concrete also has several alternatives, one of which is the use of sea sand as a substitute for fine aggregate. This research was conducted to determine the best proportion of sea sand use 10–40% with two treatments (washed and unwashed) and the use of fly ash of 20-30% on the corrosion resistance of reinforcing steel and the mechanical properties of concrete. The research results show that using up to 30% washed sea sand and 10% unwashed sea sand can increase compressive strength when compared to normal concrete. The use of up to 30% fly ash together with 20% sea sand has the same compressive strength as normal concrete. Apart from that, the use of sea sand and fly ash together has a low-risk category for reinforcing steel corrosion (10% risk of corrosion).

Abstract: Nutmeg shell waste (CP) has light and hard characteristics which can be used as a replacement material for coarse aggregate for lightweight concrete. The aim of the research is to determine the influence of aggregate characteristics after being mixed with nutmeg shells as a constituent material for concrete and determine the compressive strength value of the concrete. The method used is a laboratory experimental method with CP waste percentages of 2.5%, 5% and 7.5% of the sand volume. The results of the research show the effect of using nutmeg shells in the concrete mixture, where the compressive strength value of the concrete increases along with the increase in CP waste used. The compressive strength values of nutmeg shell concrete (CP) at compositions of 2.5%, 5% and 7.5% were obtained at 234.26, 263.56 kg/cm2, kg/cm2 and 280.14, increasing at 28 days.

Abstract: Bottom ash (BTA), a by-product of coal combustion in electric power plants, is commonly regarded as waste, presenting challenges in its management. Conversely, laterite, typically used in road construction, has become increasingly expensive due to its high quality. This study aims to investigate the mechanical properties of laterite replaced with BTA and cement. The replacement of BTA ranged from 10% to 50% of the dry weight of laterite, with cement contents of 1% and 3% of the dry weight of the laterite-BTA mixture. Experimental tests, including unconfined compressive strength (USC) and splitting tensile strength (STS), were conducted. The results indicate that replacing laterite with BTA and cement enhances strength by 2 to 8 times that of unstabilized laterite, with 20% BTA replacement yielding the highest strengths. This approach not only provides cost-effective road construction materials but also contributes to sustainable practices by conserving natural resources and reducing pollution.

Abstract: This research explores the feasibility of incorporating dust stone into cement gravel columns to enhance their mechanical properties and sustainability profile. A series of laboratory experiments including unconfined compressive strength (UCS) and permeability tests were carried out. 15 mixture designs were prepared to investigate the effect of stone dust (5-20% of cement and 0, 5, 10, 15, and 20% by weight of highest porous sample) on volume fractions of CG samples on engineering and physical properties of cemented gravel samples, at 7 and 28 days. The findings indicate that the ideal proportion of stone dust is 10%, which significantly enhances the compressibility of the CG mixture while preserving satisfactory permeability. The finding indicates that stone dust is a feasible and efficient additive for improving the performance of cement gravel columns in civil engineering applications. Moreover, stone dust provides sustainability advantages by minimizing waste production and contributing to a circular economy.

Abstract: Bitumen is essential in road construction due to its binding properties, water resistance, and durability, ensuring stable and long-lasting pavements. This study explores the potential of using agricultural waste, specifically biochar, to enhance bituminous materials. Biochar was added to bitumen in increments of 0%, 2.5%, 5%, 7.5%, 10%, 12.5%, and 15% by weight to make biochar modified bitumen (BMB). The results showed that biochar increased the softening point, viscosity, and flash and fire points, indicating improved thermal stability and deformation resistance. Conversely, ductility and penetration values decreased, resulting in a harder, less flexible bitumen with better wear and indentation resistance. The modified bitumen was prepared at 160-180°C using a high shear mixer at 4000 rpm for 30 minutes and tested per IS code standards. To identify the optimal biochar-bitumen mix, Multicriteria Decision Making (MCDM) tools such as TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) and VIKOR were used. These tools provided a comprehensive ranking system to determine the best-performing composition. The study demonstrates that biochar significantly enhances bitumen's properties, making it a viable option for more sustainable and efficient road construction applications.

Abstract: This study investigates the dual benefits of Phase Change Material (PCM) incorporation in concrete for pavement construction, focusing on both performance enhancement and energy efficiency. Through extensive mechanical testing and thermal analysis, the effects of PCM content on concrete strength and temperature stress mitigation were evaluated. Results indicate that while PCM addition led to reductions in compressive and flexural strengths, mixes containing 8% PCM maintained feasible strengths for pavement applications. Furthermore, thermal analysis demonstrated significant reductions in temperature and curling stresses with increasing PCM content, highlighting the potential for enhanced pavement durability and energy efficiency. Multi-criteria decision-making (MCDM) analysis identified the 8% PCM mix as the optimal choice due to its balanced performance across critical parameters. This research underscores the efficacy of PCM-enhanced concrete in improving pavement performance and energy efficiency, emphasizing the importance of careful PCM content selection in achieving sustainable pavement solutions.

Abstract: Internal erosion often occurs in earthen water-retaining structures such as embankment dams, levees, or dikes, which are created by seepage flows through soil or other porous material where coarser and finer particles are mixed. This erosion process may be referred to as suffusion, resulting in the transportation of fine particles carried away from the soil structure by seepage. If internal erosion occurs, the strength of the soil will be changed, and gaps or cavities in the soil structure may be created, leading to the collapse of the soil, posing a risk of damage to earthen water-retaining structures. This research investigates internal erosion behaviour of gap-graded sands with various fine contents using a series of upward seepage tests. An in-house developed apparatus with a measurement of hydraulic gradient and permeability is used to investigate the initiation and progress of internal erosion.