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Population growth has increased, causing more and more housing needs; Indonesia is one of the countries where bricks are still used as the primary material in building walls. It has resulted in increased demand for bricks. One of Indonesia's regions, Deli Serdang Regency, produces traditional bricks that burn a lot, but the process of making traditional bricks can cause environmental pollution. This research aims to find a way to reduce the effects of environmental pollution by making pressed bricks without burning and utilizing agricultural waste, namely rice husk ash (RHA). After that, a comparison was made between traditional burnt bricks from 15 sub-districts in Deli Serdang Regency and unburnt bricks made from rice husk ash (RHA). This study uses two methods, namely the method of sampling burned bricks and the method of making bricks without burning, both of which are tested for physical and mechanical properties. The results of this study use the requirements of SNI 15-2094-2000, where the test of physical properties of fuel bricks obtained a value of 76%, which meets the requirements, while bricks without burning obtained a value of 87.5%, which meets the requirements. For the results of the size of fuel bricks obtained, 66.6% of the value meets the requirements, while for bricks without burning, 100% meet the requirements. Mechanical properties test for absorption testing on fuel bricks obtained 0.135% while unburned bricks 0.130%, where the value meets the SNI requirements of a maximum absorption of 20%. Salt content testing obtained a value of 0.15% for burned bricks and 0.002% for unburned bricks, where the value meets the SNI requirements that are below 50%. Testing the compressive strength of bricks with a standard value of 5 MPa from the test results of the compressive strength of fuel bricks 3.01 MPa decreased by 39.8%, while the test of compressive strength of unburned bricks 5.17 MPa increased by 3.45%, but unburned bricks with added rice husk ash 1.98 MPa decreased by 60.4%. Based on the study's results, the absorption and salt content parameters follow the standard. At the same time, the strength test of firebricks and unburned bricks with added rice husk ash does not meet the SNI 15-2094-2000 standard, but the results of the compressive strength test of unburned bricks meet the SNI 15-2094-2000 standard. [ABSTRACT FROM AUTHOR]

West Sumatra is a province in Indonesia that is known for its high levels of seismic activity. Brick-walled buildings are particularly vulnerable during earthquakes. As the property sector continues to grow, the demand for red bricks in construction is rising. The brick industry in West Sumatra is thriving despite economic pressures. Red brick remains popular among the public, particularly as the main component of walls in simple house buildings. However, each manufacturer uses different raw materials, resulting in varying levels of quality, which still need to meet the Indonesian National Standard (SNI). This research aims to determine which brick composition has the best elemental properties in West Sumatra and investigates the effect of temperature on the chosen brick and its characteristics. The X-ray fluorescence Spectroscopy (XRF) test results indicate that the composition of Pariaman bricks is the closest to the required standards and so they were selected as test specimens to evaluate brick characteristics. The highest compressive strength results were obtained in bricks at a temperature of 800 oC and they also fulfilled the requirements of SNI 15-2094-2000, with a water absorption capacity under 20% of the water absorption rates. Based on the density testing, the increase in the firing temperatures of the specimens increases the bulk density. This is related to the lower porosity of brick at higher temperature firings. The modulus of elasticity was directly proportional to the compressive strength; the higher the temperature, the higher the brick stiffness. [ABSTRACT FROM AUTHOR]

According to the national standard body in Indonesia, the compressive strength of 20 MPa concrete is medium quality concrete. Medium-strength concrete is usually used for floors, light construction, houses, warehouse factories, and sidewalks. The use of medium-strength concrete is very broad, it is necessary to continuously conduct research to produce new innovations. Previous research on the utilization of waste rubber tires has been carried out. Research on the development of concrete with the use of waste tire rubber powder is very interesting to do considering the waste of used tires that continues to increase along with the increase in the number of motorized vehicles in Indonesia. Portland Cement (OPC) and Portland Pozzolan Cement (PPC) are the two types that will be used in this research to see its effect on concrete with waste rubber powder. These two cements also have different corrosion resistance. And seawater is one of the triggers of high concrete corrosion. Research on the development of concrete with the use of waste tire rubber powder is very interesting to do considering the waste of used tires that continues to increase along with the increase in the number of motorized vehicles in Indonesia. Portland Cement (OPC) and Portland Pozzolan Cement (PPC) are the two types that will be used in this research to see its effect on concrete with waste rubber powder. These two cements also have different corrosion resistance. And seawater is one of the triggers of high concrete corrosion. This study aims to analyze how the compressive strength of PPC concrete compares with OPC and the addition of used tire powder under seawater treatment conditions. Six concrete variants were made and then tested for compressive strength. The compressive strength values of variants 1 to 6 were obtained as 20.78 MPa, 18.26 MPa, 19.56 MPa, 16.58 MPa, 13.03 MPa. The results show that tile powder is not effective in increasing construction strength, but the use of PPC cement is more effective than the use of OPC in improving construction, especially for cement use in buildings close to sea water. [ABSTRACT FROM AUTHOR]

This study aims to determine the effect of the sintering temperature of nanosilica on physical, mechanical, dielectric, and output voltage properties. The nanosilica particles used in this experiment were produced using the alkaline fusion method from natural sand. The green bodies were uniaxially formed with a pressure of 75 MPa and then were pressureless sintered at various temperatures of 1330, 1360, 1390, 1420, and 1450°C for 2 hours in an air atmosphere. The results of sintering showed that the highest bulk density and the relative density of 2.49 ± 0.03 g/cm3 and 94.03 ± 0.01% respectively were achieved at a sintering temperature of 1390°C. The XRD patterns of the sintered silica indicated phases of quartz, tridymite, and cristobalite, with the strongest peak corresponding to the cristobalite phase. The highest compressive strength and diametral tensile strength values of 17.23 ± 0.27 MPa and 6.06 ± 0.71 MPa respectively were obtained on specimens sintered at 1390°C. However, the highest values of the dielectric constant of 544.28, dielectric loss of 195.94, and output voltage of 1.58 mV were obtained at a sintering temperature of 1330°C. Various sintering temperatures do not significantly influence the characteristic of dielectric and output voltage of the sintered specimens. [ABSTRACT FROM AUTHOR]

The coronavirus causing the Covid-19 pandemic has been experienced by us since 2020, which has led to an increase in the use of disposable medical masks in Indonesia and even worldwide. Polypropylene is a thermoplastic polymer used as the main ingredient in medical masks that takes more than 25 years to decompose in landfills. This research offers an innovative way to use medical mask waste in high-performance concrete. The resulting medical mask waste is subjected to a sterilization process and cut into fibers to analyze the effect of its addition on the compressive strength and splitting tensile strength of high-performance concrete. The research began with testing the physical and mechanical properties of the materials, designing a concrete mix using the absolute volume method, and taking samples for compression and splitting tests. The variation in the ratio of water-cement and pozzolanic materials w (c+p) is 0.32. As a result, the compressive strength of concrete increased with a fiber size of 5×0.5 cm and 2×0.5 cm. An increase is up to 7 % with an optimum value of 72.37 MPa with a fiber size of 2×0.5 cm and a content of 0.15 %. However, there was a decrease in the compressive strength with a 5×1 cm mask fiber size. The overall split tensile strength value of all variations in waste fiber size and content increased with an optimum value of 7.29 MPa at 0.20 % fiber content with a fiber size of 5×0.5 cm. This indicates that polypropylene fibers from medical mask waste have a positive effect on high-performance concrete, namely improve the properties of concrete with a low tensile strength, which is expected to inhibit the propagation and reduce the size of cracks in reinforced concrete structures. [ABSTRACT FROM AUTHOR]

Background: The prevalence of dental caries in Indonesia in 2018 is 45.3% of the population. Tooth filling is done so that dental caries does not spread further. The restorative material that is commonly used is composite resin. The compressive strength of composite resin is affected by the polymerization process. The surface of the composite resin exposed to air causes the formation of oxygen inhibited layer (OIL). Glycerin acts as a surface coating that can inhibit contact between the composite resin and air so that polymerization can run optimally. Changes in the mechanical properties of composite resins are also influenced by salivary pH and food intake. The acid contained in fermented milk can affect the matrix and filler bonds in composite resins. Further research is needed to determine the compressive strength of nanohybrid composite resins after the application of glycerin in fermented milk immersion. Purpose: To find out whether there is a change in the compressive strength of nanohybrid composite resin after the application of glycerin immersed in fermented milk, also to find out whether the glycerin application and immersion in fermented milk play a role in causing changes of the compressive strength. Methods: Laboratory experimental research with a total sample of 28 which was divided into 4 groups. Composite resin samples were made with a thickness of 3 mm and a diameter of 5 mm, followed by measuring the compressive strength using the Universal Testing Machine. Results: Independent T-Test test showed significantly different results. The compressive strength value of the group with glycerin application was higher than without glycerin application. Meanwhile, the group immersed in fermented milk drinks had lower compressive strength compared to saline immersion. Conclusion: The compressive strength of the nanohybrid composite resin changed after the application of glycerin immersed in fermented milk. [ABSTRACT FROM AUTHOR]

The suitability of bamboo's basic characteristics is very important for more specific purposes, such as composite raw materials. Anatomical, physical, mechanical, and chemical characteristics are some of bamboo's fundamental characteristics. This study analyses the basic properties, such as physical, mechanical, and chemical properties of bamboo from the Forest Area with Special Purpose (FASP) Pondok Buluh Sumatera Island, Indonesia (I); analyses the relationship between the properties of each type of bamboo (II); and chooses the type of bamboo with the best properties that have the potential to be applied to composite materials, such as laminated bamboo (III). This study used materials consisting of six species of bamboo from the FASP Pondok Buluh. The manufacture of physical and mechanical test samples refers to the ISO 22157 standard, 2004, while the chemical properties test refers to the TAPPI 1999 standard. The chemical, physical, and mechanical properties of bamboo vary widely among species. The lowest holocellulose and α-cellulose content were found in the Kuning Bamboo (B. vulgaris var. vittata). The content of holocellulose and α-cellulose causes the lowest density in Kuning Bamboo (B. vulgaris var. vittata). The Dasar Bamboo (Bambusa vulgaris) has the highest levels of lignin. The substances have an impact on moisture content, T/R ratio, and shear strength. The Dasar Bamboo (Bambusa vulgaris) has the lowest moisture content, the highest T/R ratio, and the highest shear strength. However, Betung Bamboo (Dendrocalamus asper) has the highest density in this study. The compressive strength of the Betung Bamboo (Dendrocalamus asper) has the highest value. Therefore, Betung bamboo and Dasar Bamboo in this study were potentially utilized for composite materials, such as laminated bamboo. [ABSTRACT FROM AUTHOR]

Concrete is one of Indonesia's most widely used construction materials. Thus, the need for concrete materials, mainly sand keeps increasing. Excessive sand mining will harm the environment, causing erosion and landslides. In addition, recent trends in construction have created negative impacts to the nature, such as the dumping of lightweight bricks remnant. This study was conducted to examine the use of lightweight brick waste as a substitute for fine aggregate on the compressive strength of concrete. The design of concrete in this research uses SNI 03 - 2834 - 2002 as the guidelines. The variations are 0%, 10%, 20%, and 30% of lightweight brick waste to replace fine aggregate. This research uses quantitative primary data to obtain the compressive strength of concrete. The tests were held on the seventh, fourteenth, and twentyeighth day of concrete age, and simple regression analysis was used to determine the effect of weight on the use of brick wastes as a partial substitution of fine aggregate on the compressive strength of concrete. The results show that the maximum and minimum compressive strengths were obtained in variation 10% and variation 30%, which produce the compressive strengths 24.45 MPa and 18.03 MPa at the twenty-eighth day of concrete. Based on the results of the simple regression analysis with SPSS, the use of lightweight brick waste has a significant effect on the compressive strength of twenty-eight day of concrete by 64.8% and the linear regression formula in this test can be written as Y = 24.3 -0.170x. [ABSTRACT FROM AUTHOR]

Eggshell waste and husk ash are abundant in Indonesia, with a population of 263 million, which is estimated to reach 483,920 tons and 10 million tons, respectively. However, this waste has not been utilized optimally, so it has a negative impact on the environment. This study aims to analyze the quality (compressive strength and water absorption) of a mixture of eggshells and husk ash as paving blocks for buildings to reduce the environmental burden. The experiment was carried out using a 2 factor factorial design: eggshells (4 levels: 0%, 5%, 7% and 15%); and husk ash (4 levels: 0%, 5%, 8% and 10%). The data were analyzed using analysis of variance, followed by analysis of mean using the least significant difference (LSD). The results showed that the mixture of eggs and husk ash had good quality, so it could reduce the need for Portland cement, which has a negative impact on the environment during production process. The best quality of a paving block was a mixture of 10% of husk ash and 15% of eggshells (A4B4 treatment) with the compressive strength value of 39 Mpa and water absorption of 5.8% (good). [ABSTRACT FROM AUTHOR]

The Lapindo hot mud in Sidoarjo, Indonesia (Lusi) has caused a detrimental effect on the environment and the community for more than 10 years. On the bright side, the waste mud contains a high amount of silica (SiO2) which makes it promising to be used as a concrete mix. This study tests the use of Lusi as an additive material in concrete lining production to reduce the use of sand. The standard of concrete lining considered is the national standard of Indonesia (SNI 03-4804-1998) for K250 concrete. Experiments were carried out using a mixture of Lusi 0%, 5%, 15%, and 25% of the weight. The results of the analysis of variance demonstrated an F-statistics of 173.883 with a significance value of 0.000 (< 0.05). This means that the compressive strength between concrete samples based on each percentage of the Lusi mixture is significantly different. Furthermore, the regression analysis demonstrates a staggering R-square value of 0.9999, which shows that the addition of Lusi material greatlaffectsct the compressive strength of the concrete. The addition of Lusi material greatly affects the decrease in the compressive strength of the lining concrete. The average compressive strength of concrete based on the addition of Lusi material of 0%, 5%, 15%, and 25% are 347.15 kg/cm², 297.85 kg/cm², 209.68 kg/cm², and 145.04 kg/cm2, respectively. Therefore, it is concluded that a 5% addition of Lusi material is the most recommended level of Lusi material. This finding can be considered a solutive idea for managing the Lapindo mudflow disaster, which can also bring economic advantage in the production of the concrete lining by minimizing the use of sand. [ABSTRACT FROM AUTHOR]

The purpose of this research is to utilize pumice waste as one of the constituent materials of lightweight concrete. Indonesia, as an archipelagic country, has produced coral pumice waste scattered throughout the country. It is expected that by utilizing pumice waste, lightweight and environmentally friendly concrete may be produced. The tests carried out consisted of three series to examine the effect on the composition of light aggregate (series 1), the effect of light aggregate size (series 2), and the effect of the water to binder ratio (series 3). The composition of light aggregate as a substitute for coarse aggregate by 25%, 50%, 75%, and 100%, with a maximum aggregate size of 20 mm and water to binder ratio of 0.50. In the second series, the maximum size of lightweight aggregate is 9.5 mm, 16 mm, 20 mm, and 25 mm, using 100% lightweight aggregate with water to binder ratio of 0.50. In the third series, the water to binder ratio is varied 0.46, 0.48, and 0.50. A slump test was conducted to check the workability of fresh concrete, while the hardened properties test consisted of compressive strength and mass density. The results of the tests show that using a larger amount of lightweight aggregate reduces compressive strength. The variation of the maximum size of lightweight aggregate shows a pattern that the larger the aggregate size produces lower the compressive strength. The decrease in compressive strength also occurs in concrete with high water to binder ratio. [ABSTRACT FROM AUTHOR]

Geopolymer is a renewable construction material that reduces dependence on ordinary portland cement (OPC), where OPC manufacturing impacts carbon dioxide (CO2) emissions. The main aspect of geopolymers being studied is the precursor of pozzolanic material, used as a cement substitute because it contains aluminosilicate (Si-Al). Polymerization occurs between the precursors, reacted by alkaline activator solution (AAS). Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were used as AAS. In this study, local precursors from industrial waste and biomass were utilized. Fly ash was employed as a reference in the precursor by 5% - 10% substitution of glass powder, rice husk ash, bagasse ash, and palm shell ash. Moreover, 2% superplasticizer and 5% extra water were used to increase the flowability of fresh geopolymer. Tests were carried out on the setting time of paste, flow table, and compressive strength of geopolymer mortar. The tests were on the initial setting time of 25-75 minutes and the final setting time of 40-115 minutes. The setting time results revealed that the time of each substitution accelerated geopolymerization due to the substitution of precursors containing higher CaO and SiO2. Setting time and flowability/workability had a linear regression correlation (R2) of 0.95, with the flow table ranging from 180-250 mm. The compressive strength ranged from 25.88 - 36.36 MPa through a curing temperature of 70oC for 24 hours, followed by curing at ambient temperature for up to 28 days. [ABSTRACT FROM AUTHOR]

Geomechanical analysis using well log can be used to determine the fracable zone. Fracability is a parameter applied in the development of shale hydrocarbon to overcome the weaknesses in determining the fracable zone which was previously only based on high brittleness and considered a good hydraulic fracking candidate. The fracability model from the results of geomechanical analysis is used as the basis for hydraulic fracking planning for the development of Brownshale hydrocarbon in the Bengkalis Trough area, as a case study. Therefore, it has good development prospects. The geomechanical analysis of well BS-03, is the only well that penetrated the Brownshale formation. The geomechanical parameters investigation consists of Young's modulus, Poisson's ratio, unixial compressive strength, brittleness index, and the fracability index. Therefore, the fracability model is built by correlating the depth interval of the Brownshale formation and the geomechanical parameters, in order to determine the Brownshale formation interval as the basis for the location selection process and the hydraulic fracking interval. The results of geomechanical analysis show an interesting phenomenon in the fracability index, with negative and positive depth intervals at the top and bottom, respectively. The upper and lower depth intervals represent fracture barrier and fracable zone interval. Abbreviations vp: primary wave velocity (km/sec); vs: secondary wave velocity (km/sec); ρ: rock density (g/cc); E: Young's Modulus (MPa); υ: Poisson's ratio (dimensionless); UCS: unconfined compressive strength, MPa; Vp: primary wave velocity (km/sec) where; Ebrittleness: Young's modulus of brittleness, fraction; Emin: Minimum Young's modulus, MPa; Emax: Maximum Young's modulus, MPa; FI: Fracability index, fraction; Bn: Brittleness normalization, fraction; En: Young's Modulus normalization, fraction; B: Brittleness at analyzed depth, fraction; Bmin: Minimum brittleness in the formation was investigated, fraction; Bmax: Maximum brittleness in the formation was investigated, fraction; β: Biot's effective stress constant; Bc: Skempton's coefficient [ABSTRACT FROM AUTHOR]

A compacted claystone-bentonite mixture is proposed for use as a clay barrier. This research, in turn, focuses on the effects of bentonite mix on the permeability and shear strength of compacted claystone-bentonite mixtures. The claystone used was obtained from the Banjarbakula landfill project, approximately 10 km from Banjarbaru, the South Kalimantan Government's Administrative Center, Indonesia. The bentonite used is commercially sold in Indonesia. The claystone was mixed with bentonite at a percentage of 5%, 10%, 15%, and 20% bentonite by dry-weight bases. The mixtures were compacted at a moisture content of 10%, 15%, and 20% to reach the dry unit weight of 16kN/m³-19kN/m³. Permeability and unconfined compressive strength tests were performed in this study. The result showed that the permeability of mixtures decreases with increasing bentonite content. The addition of up to 20% bentonite to the mixture reduced the permeability by 4.5 times, as compared to the sample without bentonite. Moreover, the mixtures' shear strength indicated by compressive strength and cohesion increased by increasing the bentonite content to 15%. The maximum shear strength obtained was three times higher than without bentonite. The mixtures' permeability and shear strength were also significantly affected by the sample's density and moisture content. A percentage of 20% bentonite is recommended, considering the wide range of acceptability based on two criteria (i.e., permeability and shear strength). [ABSTRACT FROM AUTHOR]

This paper discusses the shrinkage rheological model of high-performance concrete with a compressive strength of 60 MPa. This is based on experimental research in Indonesia. Three specimens measuring 150 mm × 150 mm × 600 mm were used. Specimens were placed in a conditioned room with a temperature of 28 3oC and relative humidity of 72±5%. Observations were conducted over 7-800 days using an embedded vibrating wire strain gauge for each specimen. As a result, the shrinkage rheological model was single or multi Kelvin-Voigt in series with timedependent disturber flow in it. Disturber flow depends on product hydration growth, weather, pore number, size, and distribution. The model agrees with experimental results. Moreover, it also fits the results using high strength concrete column and high strength self - compacting concrete cylinder. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate volume changes and compressive strength behavior of compacted high expansive soils from lateritic soils (60%) and bentonite (40%) mixture under drying-wetting cycle repetition as a construction materials alternatives. Lateritic soil obtained from waste Nickel mining site in East Halmahera, North Maluku, Indonesia. Laboratory tests of physical properties using ASTM standard test were conducted to lateritic soil, bentonite, and mixture soil, while SEM test for lateritic and mixture soil. The soil samples have optimum moisture content based on Proctor standard compaction test results (28%). Then, samples were treated drying-wetting cycle and repeating four cycles with 25, 50, 75, and 100% series path. The soil suction measurement used the Whatman #42 filter paper placed at the top, middle, and bottom of each sample, and after that, the unconfined compression strength test was performed based on the ASTM standard. The experimental results showed that the drying-wetting cycle repetition has a significant effect on volume change, suction, and compressive strength of the soil. The increasing number of cycle causing void ratio decrease and degree of saturation increase, and soil suction tend to decrease at the certain void ratio; likewise, soil compressive strength decreases at particular water content. Decreasing soil compressive strength causes a decrease in elastic modulus so that soil failure behavior is more brittle and work-softening. Therefore, the study results provide important geotechnical characteristics data of lateritic soil with high swell-shrink potential. Henceforth, some soil improvement innovations can perform to generate high-quality construction materials more effectively and efficiently. [ABSTRACT FROM AUTHOR]

This study investigated the quality of wall bricks that are used by people in Koto Tangah - Padang to rebuild their homes after the 30 September 2009 earthquake. This research covered the nature of looks, size and tolerance, water absorption and compressive strength of bricks, and compared them with Indonesian National Standard of bricks (SNI 15-2094-2000). Primary data were gained from field sampling and laboratory testing (experimental test) and then were analyzed to determine the quality of bricks. The results showed that the bricks do not meet the requirements of the SNI 15-2094-2000. [ABSTRACT FROM AUTHOR]

Abstract: The uniaxial compressive strength is one of important parameter to determine the shear strength of rock mass by the rock classification method. To determine uniaxial compressive strength used by a testing on laboratory or in practically can use t he index method, in this research, alternatively is to use Schmidt Hammer. A method used Schmidt Hammer to determine the uniaxial compressive strength of rock is to calibrate between Schmidt Hammer Rebound (R) and uniaxial compressive strength test of laboratory and its the results are an empirical equation. The advantage of this method can practically to assess the strength of rocks in the field. At this paper is one of the alternative uses of the uniaxial compressive strength determining in sedim entary rocks in Warukin Formation at Tutupan open pit coal, South Kalimantan, Indonesia. And the next research is going to process towards another formation. [Copyright &y& Elsevier]

Abstract: Cooking oil industry in Indonesia produces a massive amount of solid waste, called Spent Bleaching Earth (SBE). Briquetting of this waste can be a good alternative to achieve zero-waste, as well as minimizing energy cost, in this industry. Therefore, the valorization of SBE as briquette was studied using different pressure and maltodextrin dosage. The results show that the physical characteristics of SBE briquette were similar to that of standard value for the wood briquette (Indonesian National Standard or SNI 1-6235-2000). [Copyright &y& Elsevier]

Recently, the global population has increased sharply, unfortunately, the availability of fossil fuel resources has significantly decreased. This phenomenon has become an attractive issue for many researchers in the world so that various studies in the context of finding renewable energy are developing continuously. Relating to this challenge, this research has been part of scientific work in the context of preparing an energy briquette employing palm oil stems and glycerol crude of biodiesel byproducts as inexpensive and green materials easily found in the Riau province, Indonesia. Technically, the palm oil stems are used for the production of charcoal particles and the glycerol crude as an adhesive compound in the production of energy briquettes. The heating value of palm oil stem is 17,180 kJ/kg, which can be increased to an even higher value through a carbonization process followed by a densification process so that it can be used as a potential matrix to produce energy briquettes. In detail, this study was designed to find out several parameters including the effect of sieve sizes consisting of 60, 80, and 100 mesh, respectively, which are used for the preparation of charcoal particles as the main matrix for the manufacture of the briquettes; the effect of charcoal-adhesive ratios (wt) of 60:40, 70:30, and 80:20; and the effect of varied pressures of 100, 110, and 120 kg/cm2 on the briquette quality. The quality of the obtained briquettes is analyzed through the observation of important properties which involve the heating value and the compressive strength using Response Surface Methodology (RSM). The results showed that the produced briquettes had an optimum heating value of 30,670 kJ/kg, while their loaded charcoal particles resulted from the mesh sieve of 80, in which there was a charcoal loading of 53 g and it pressed at 93.1821 bar, whereas, the compressive strength value of the briquette was 100,608 kg/cm2, which loaded charcoal particles from the mesh sieve of 100, the charcoal-adhesive ratio of 53:47 (wt) and the pressure of 93.1821 bar. [ABSTRACT FROM AUTHOR]

Concrete can be harmful to the environment due to its high energy consumption and CO 2 emission and also has a potential crack formation, which can promote a drop in its strength. Therefore, concrete is considered as a non-sustainable material. The mechanisms by which bacterial oxidation of organic carbon can precipitate calcite that may fill the voids and cracks on cement-based materials have been extensively investigated to prevent and heal the micro-cracks formation. Hence, this study focused on utilizing a new alkaliphilic bacterial strain indigenous to an Indonesian site, Lysinibacillus sphaericus strain SKC/VA-1, incorporated with calcium lactate pentahydrate, as a low-cost calcium source, with various bacterial inoculum concentrations. The bacterium was employed in this study due to its ability to adapt to basic pH, thus improving the physical properties and rejuvenating the micro-cracks. Experimentally, the addition of calcium lactate pentahydrate slightly affected the mortar properties. Likewise, bacteria-incorporated mortar exhibited an enhancement in the physical properties of mortar. The highest improvement of mechanical properties (an increase of 45% and 36% for compressive and indirect tensile strength, respectively) was achieved by the addition of calcium lactate pentahydrate incorporated with 10% v/v bacterial inoculum [about 7 × 10 7  CFU/ml (colony-forming unit/ml)]. The self-healing took place more rapidly on bacterial mortar supplemented with calcium lactate pentahydrate than on the control specimen. XRD analysis demonstrated that the mineralogical composition of self-healing precipitates was primarily dominated by calcite (CaCO 3 ), indicating the capacity of L. sphaericus strain SKC/VA-1 to precipitate calcite through organic carbon oxidation for self-healing the artificial crack on the mortar. To our knowledge, this is the first report on the potential utilization of the bacterium L. sphaericus incorporated with calcium lactate pentahydrate to increase the mortar properties, including its self-healing ability. However, further study with the water-cement ratio variation is required to investigate the possibility of using L. sphaericus and calcium lactate pentahydrate as an alternative method rather than reducing the water-cement ratio to enhance the mortar properties.

To address sustainability issues by facilitating the use of high-volume fly ash (HVFA) concrete in industry, this paper investigates the early age hydration properties of HVFA binders in concrete and the correlation between hydration properties and compressive strengths of the cement pastes. A new method of calculating the chemically bound water of HVFA binders was used and validated. Fly ash (FA) types used in this study were sourced from Indonesia and Australia for comparison. The water to binder (w/b) ratio was 0.4 and FA replacement levels were 40%, 50% and 60% by weight. Isothermal calorimetry tests were conducted to study the heat of hydration which was further converted to the adiabatic temperature rise. Thermo-gravimetric analysis (TGA) was employed to explore the chemically bound water (WB) of the binders. The results showed that Australian FA pastes had higher heat of hydration, adiabatic temperature rise, WB and compressive strength compared to Indonesian FA pastes. The new method of calculating chemically bound water can be successfully applied to HVFA binders. Linear correlation could be found between the WB and compressive strength. [ABSTRACT FROM AUTHOR]

Osteosynthesis plates are clinically used to fixate and position a fractured bone. They should have the ability to withstand cyclic loads produced by muscle contractions and total body weight. The very high demand for osteosynthesis plates in developing countries in general and in Indonesia in particular necessitates the utilisation of local products. In this paper, we investigated the mechanical properties, i.e. proportional limit and fatigue strength of Indonesian-made Narrow Dynamic Compression Plates (Narrow DCP) as one of the most frequently used osteosynthesis plates, in comparison to the European AO standard plate, and its relationship to geometry, micro structural features and surface defects of the plates. All Indonesian-made plates appeared to be weaker than the standard Narrow DCP because they consistently failed at lower stresses. Surface defects did not play a major role in this, although the polishing of the Indonesian Narrow DCP was found to be poor. The standard plate showed indications of cold deformation from the production process in contrast to the Indonesian plates, which might be the first reason for the differences in strength. This is confirmed by hardness measurements. A second reason could be the use of an inferior version of stainless steel. The Indonesian plates showed lower mechanical behaviour compared to the AO-plates. These findings could initiate the development of improved Indonesian manufactured DCP-plates with properties comparable to commonly used plates, such as the standard European AO-plates., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The enormous need of orthopaedic (surgical) implants such as osteosynthesis plates is difficult to be fulfilled in developing countries commonly rely on imported ones. One of the alternatives is utilization of local resources, but only after they have been proven safe to use, to overcome this problem. Surface properties are some of the determining factors of safety for those implants. We have succeeded in developing prototype of osteosynthesis plate and the results indicate that Indonesian-made plates need improvement with regards to the surface quality of physical characterization.