Jafril Tanjung’s research while affiliated with Andalas University and other places

High-strength concrete made with large amount of cement augmented with additives causing high hydration heat and large shrinkage during hardening process, making it susceptible to cracks at early age due to its still low tensile capacity. These cracks must be mitigated early. Self-healing method using ureolytic bacteria Bacillus sp. as concrete crack-healing can be smart solution to overcome this problem. Urease enzyme produced by ureolytic bacteria can hydrolyze urea and Ca ²⁺ (derived from CaCl 2 ) added as precursors to precipitate CaCO 3 as concrete cracks closure biologically. This study aims to analyze effect of ureolytic bacteria Bacillus sp. cultivated from local landfill Gampong Jawa, Banda Aceh as crack self-healing on flexural tensile strength of high-strength concrete. Bacteria were immobilized into diatomaceous earth to increase viability during casting and after residing in harsh environment of concrete which used as 10% substitution for fine aggregates. Concentration of bacteria and growth media used were varied by 0%; 0.5%; 0.6%; and 0.7% of cement weight. Specimens were beams measuring 100×100×400mm which was given 1D10 mm tensile reinforcement to prevent brittle failure during testing. First, an initial crack load of 60% of 7 days concrete flexural tensile strength was given, then treatment was carried out for 28 days in water to observe crack healing for 7, 14, 21 and 28 days. After completing crack healing phase, flexural tensile capacity testing was carried out until the specimens collapsed. The results showed that flexural tensile capacity of high-strength concretes was 5.49 ton, 5.69 ton, 5.89 ton and 5.86 ton respectively and the percentage of concrete crack closure after healing phase for 28 days after being initially cracked was 4.76%; 77.90%; 87.09%; and 89.09% each, at variations of Bacillus sp. 0.0%; 0.5%; 0.6%; and 0.7%. Optimum value was obtained at bacterial percentage of 0.7% resulting in an increase both in flexural tensile capacity of 6.74% and in crack healing efficacy of 84.27% compared to non-bacteria concrete.

This study conducts a preliminary investigation to determine the material properties of Cross- Laminated Timber (CLT) made from the bark of unproductive palm trunks. One-third of the lower part of palm trunks, aged over 20 years, was used for this purpose. CLTs were created by laminating palm boards into three and five layers, each measuring 200 mm x 20 mm x 1500 mm. A chemical epoxy was employed for lamination. The palm stems were dried in an oven at 110°C for 24 hours. Test results revealed a water content of 6.79% and a specific gravity of 0.23 gr/cm3 in oil palm stems. According to ASTM D143-94- 2005 and JIS Z210-21118 standards, wood's acceptable moisture content ranges from 12% to 20%. Given its low specific weight and minimal water content, palm oil trunks, including infill walls, show promise for use in earthquake-resistant construction.

Reinforced concrete is a construction that is vulnerable to damage during an earthquake if not done properly. This article focuses on the results of field observations after the earthquake disaster in Lombok and Palu in 2018, with the aim of identifying the type of damage that occurred in reinforced concrete buildings. This identification is important to understand the potential causes of damage and/or collapse in reinforced concrete buildings. The results of field observations show that low concrete quality and lack of standard reinforcement detailing processes are the main factors contributing to the large number of buildings experiencing damage and/or collapse during the earthquake. Poor quality concrete, such as a mismatch in the mix or a lack of strength, can make a structure brittle and unable to withstand excessive earthquake forces. Apart from that, lack of attention to the reinforcement detailing process is also a cause of significant damage. Non-standard reinforcement detailing includes a lack of the required amount of reinforcement in the structure, installation of shear reinforcement that does not meet the requirements, and a lack of shear reinforcement at beam and column connections. Lack of reinforcement in structural connections reduces the strength and stiffness of the structural system, thereby increasing the risk of collapse during an earthquake. The location and method of installing brick walls is also one of the factors causing building damage. Through analysis of the results of these observations, it can be concluded that good quality concrete and the process of detailing reinforcement and brick walls according to standards are very important to reduce damage and increase the resistance of reinforced concrete structures to earthquakes. Proper implementation of structural design specifications and careful monitoring during construction can help reduce the risk of damage caused by earthquakes.