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All Journal Semesta Teknika Jurnal Rekayasa Sipil Journal of Renewable Energy and Mechanics Jurnal Riset Teknologi Pencegahan Pencemaran Industri Makara Journal of Science
Harmaji, Andrie
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Automotive Engineering Chemical Engineering, Chemistry & Bioengineering Chemistry Civil Engineering, Building, Construction & Architecture Energy Engineering Environmental Science Industrial & Manufacturing Engineering Mechanical Engineering Social Sciences Transportation

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Mechanical and Physical Properties of Cement Mortar with Recausticizing Solid Byproduct Sijabat, Edwin Kristianto; Harmaji, Andrie; Hendriansyah, Hendriansyah
Semesta Teknika Vol. 27 No. 2 (2024): NOVEMBER
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v27i2.15429

Abstract

The Kraft process is a method used to make paper pulp. This method produces cooking residue that can be recycled again. The recausticizing process produces large amounts of by-products.This research utilizes solid waste from causticizing from the pulp industry as a partial substitute for Portland cement for mortar raw material to obtain a material with good mechanical properties. The solid waste was pulverized, then characterization of Loss on Ignition (LOI), Inductively Coupled Plasma (ICP), Titration, and Total Titrable Alkali was carried out. The percentage of solid waste resulting from recausticizing as a substitute for cement is 0-100%, with a water-cement ratio (w/c) of 0.3. The mixed material is then printed into a 50x50x50mm mold followed by drying using the moist curing method. The hardened samples were tested for Density, Porosity, Water Absorption, and Compressive Strength. Mortar with partial cement replacement with 20-100% solid waste recousticizing produces a compressive strength of 1.3-22.6 MPa. The resulting water absorption ranges from 14.59-31.35%.
Properties of Calcined Oebelo Red Soil Modified Fly Ash based Geopolymer Harmaji, Andrie; Simatupang, Partogi Hasudungan; Ramang, Ruslan; Sinaga, Ari Esclesias
Jurnal Rekayasa Sipil (JRS-Unand) Vol. 18 No. 3 (2022)
Publisher : Civil Engineering Departement, Andalas University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25077/jrs.18.3.222-229.2022

Abstract

Research on fly ash has developed rapidly in recent years, one of which is its use as an environmentally friendly geopolymer concrete material. This research study the effect of calcination temperature and duration of red soil to compressive strength and setting time of fly ash based geopolymer paste. The red soil calcination process was carried out with variations in temperature of 400°C, 600°C, and 800°C for 4 and 8 hours of calcination. The activator solution was prepared by mixing a solution of NaOH with a solution of Na2SiO3 with a 1:1 composition. Sample treatment was carried out in 2 types, with ambient curing type and dry curing type. From the results of this study, the fastest setting time and maximum compressive strength of geopolymer paste of 23.14 MPa achieved at 800°C red soil calcination at 8 hours, and dry curing.
Characterization and Drug Release Evaluation of Chlorhexidine-Encapsulated Silica Nanoparticles for Potential Root Canal Disinfection Rakhmawati, Widya; Harmaji, Andrie; Djati, Fanni Kusuma; Sunendar, Bambang
Makara Journal of Science Vol. 29, No. 2
Publisher : UI Scholars Hub

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Abstract

The failure of root canal treatments is often attributed to bacterial invasion of the dentinal tubules, where pathogens can persist and complicate healing. Chlorhexidine digluconate, a potent antimicrobial agent, has been widely utilized for its broad-spectrum antibacterial effects. However, challenges remain in achieving efficient distribution and sustained release within the root canal system. This study investigates the encapsulation of chlorhexidine digluconate within silica nanoparticles as a novel drug delivery system that is aimed at improving root canal treatment outcomes. Silica nanoparticles were synthesized using the sol-gel method and subsequently immersed in a 2% chlorhexidine digluconate solution for 15 to 30 minutes to achieve encapsulation. The resulting materials were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. SEM analysis revealed particle sizes in the range of 80–150 nm for nanoparticles aged for 15 minutes and in the range of 250–350 nm for those aged for 30 minutes. FTIR spectroscopy confirmed the presence of functional groups characteristic of silica, chitosan, and sodium alginate, indicating successful encapsulation. The UV–Vis spectrophotometry demonstrated that silica nanoparticles aged for 30 minutes exhibited a more stable and controlled release of chlorhexidine digluconate (0.08 ppm) over a 60-minute period. This study presents a novel approach for enhancing root canal treatment, in which silica nanoparticles are utilized for controlled drug delivery. Additionally, the study shows that longer aging times may offer improved stability and efficacy in sustained antimicrobial action. The findings suggest that the use of silica-encapsulated chlorhexidine nanoparticles is a promising strategy for more effective endodontic treatment because it addresses bacterial invasion and supports long-term therapeutic effects.
Impact of Reduced Activator Concentration and Curing Method on Compressive Strength of Metakaolin/Fly Ash-based Geopolymer Mortar Harmaji, Andrie; Haimir, Alexander Syahlendra; Sunendar, Bambang
Jurnal Riset Teknologi Pencegahan Pencemaran Industri Vol. 14 No. 1 (2023): May
Publisher : Balai Besar Standardisasi dan Pelayanan Jasa Pencegahan Pencemaran Industri

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21771/jrtppi.2023.v14.no1.p19-28

Abstract

The demand for cement is increasing each year, but the manufacture of 1 tonne of cement produces an equal number of carbondioxide (CO2) gas which is directly related to the increase in global warming. Therefore, we need a substitute material, namely geopolymer. This material has relatively superior properties compared to cement. However, one of the drawbacks of geopolymers is that the production costs are relatively more expensive compared to the manufacture of pre-cast cement because it requires chemical solutions such as sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) to activate the precursor. This research was conducted to replace a specific ratio of alkali activator with water to reduce the use of alkaline hydroxide solutions and sodium silicate while reducing production costs. The experiment was carried out by replacing the activator solution with water at a certain amount with a different curing method. Mechanical properties, X-Ray Diffraction (XRD), and Fourier Transform Infrared (FTIR) spectroscopy characterization were used to analyze the effect of additional water in geopolymer. The compressive test result shows that the maximum water content that can replace the activator solution is 20% by activator mass for fly ash-based geopolymers and 30% by activator mass for metakaolin-based geopolymers, with sealed and bare curing conditions before the compressive strength was decreased sharply. Substitution of 10% water in fly ash-based geopolymer increases the compressive strength to 17.20 MPa. Compressive test results and characterization showed that the optimal curing condition for fly ash-based geopolymer was sealed curing and bare curing for metakaolin-based geopolymer. The strength increase is due to O-C-O bonds representing sodium carbonate (Na2CO3), which affects the compressive strength of fly ash-based and metakaolin-based geopolymers.
Effect of Quenching Medium and Tempering Temperature on Microstructure and Hardness of JIS SUP 9 Steel: Pengaruh Media Pendingin dan Temperatur Tempering pada Mikrostruktur dan Kekerasan Baja JIS SUP 9 Harmaji, Andrie; Korda, Akhmad Ardian; Ramadhan, Rama; Pambudi, Satrio
Journal of Renewable Energy and Mechanics Vol. 6 No. 01 (2023): REM VOL 6 NO 01 2023
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25299/rem.2023.10973

Abstract

JIS SUP 9 steel is one of the materials commonly used for suspension components in motorized vehicles with medium carbon steel base material. It must have good hardness and toughness so that failure does not occur during operational. This research was conducted to increase the hardness of JIS SUP 9 Steel through a heat treatment and various quenching media. The heat treatment was carried out with 830-880ºC temperature with a holding time of 7 minutes then cooled using water and oil. After treatment, tempering was carried out with a holding time of 7 minutes and then cooled in room temperature. Hardness testing was carried out using Microhardness Vickers and then the microstructure was observed using an Olympus Metallurgical Microscope. The results show that heat treatment followed by rapid cooling increases the initial hardness of JIS SUP 9 (229 VHN) steel. The decrease in hardness after the tempering process will be higher with increasing tempering temperature. The results of the microstructure of the sample without heat treatment showed pearlite and ferrite phases. After heat treatment, tempered martensite, residual austenite and carbide phases appear. It can be concluded that changes in the microstructure affect the hardness of JIS SUP 9 steel.
Co-Authors Akhmad Ardian Korda, Akhmad Ardian Bambang Sunendar P Edwin K Sijabat Fanni Kusuma Djati Haimir, Alexander Syahlendra Hendriansyah, Hendriansyah Pambudi, Satrio Partogi H. Simatupang, Partogi H. Rakhmawati, Widya Ramadhan, Rama Ruslan Ramang Sinaga, Ari Esclesias