Judul: Pemanfaatan Karet Alam Sebagai Aditif Pada Mortar Untuk Meningkatkan Mutu Jalan Semen Beton
Abstrak: Nowadays, natural rubber consumption in Indonesia is relatively low. By diversification of natural rubber uses as additional mixture for concrete road is expected to increase its consumption. At this time, concrete road doesn’t use latex, so it will less flexible and susceptible to crack. Also this matter can’t make concrete road comfortable to use. Therefore, with admixture of latex to the cement may be able to increase flexural strength. The objectives of this research were to know type and dose of stabilizing agent for suitable admixture of latex and cement, and to know the effect of type of latex and rubber dose as additional mixture for mortar. This research consisted of two steps. First step was preliminary research which used type (Emal, Emulgen and Casein) and dose (1, 3, 5 and 7%) of stabilizing agents to determine a suitable admixture of latex and cement. Second step was main research where the effects of latex on mortar was determined. Types of latex tried were Centrifuge Latex (LP), Double Centrifuge Latex (LDS) and Deproteinized Natural Rubber Latex (LDPNR). Rubber doses of 0 (control), 1, 3, 5, 7 and 9 were used. When latex was mixed with cement, it agglomerated. Therefore, suitable type and dose of stabilizing agent was needed. The best stabilizing agent was Casein of 7% because it could maintain the setting time to almost 210 minutes. This combination was used in main research. The highest initial weight was obtained from LDS, i.e. 261.25 g, whereas final weight, i.e. 266.70 g. Rubber dose of 1% gave the highest initial weight, i.e. 268.70 g and final weight, i.e. 272.83 g. Final weight would be heavier than initial weight. The more rubber dose used in mixture mortar, the less weight of mortar produced. Mortar added by latex showed lighter weight than its control. LDS gave a significant effect on mortar’s compressive strength, whereas LDPNR didn’t have significant effect. LDS gave the highest compressive strength, i.e. 176.60 kg/cm2. Rubber dose of 1% gave the highest compressive strength, i.e. 200.67 kg/cm2. The more rubber dose used, the less compressive strength of mortar produced. LDS gave highest flexural strength than LP and LDPNR, i.e. 33.62 kg/cm2. Rubber dose of 1%, i.e. 36.77 kg/cm2 gave the highest flexural strength. LDS dose of 7% gave the highest flexural strength, but its compressive strength was low. Therefore, to produce strong and flexible mortar could be used LDS with dose of 1%.
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Judul: Pemanfaatan Lateks Karet Alam Sebagai Bahan Pemodifikasi Aspal Untuk Meningkatkan Mutu Perkerasan Jalan Aspal.
Abstrak: Indonesia is the second largest producer of natural rubber in the world after Thailand. Indonesia's natural rubber production in 2007 reached 2.55 million tons per year. However, Indonesia's natural rubber production has decreased due to the global crisis that occurred in 2008. One of the sectors directly affected by the crisis is the automotive industry which is the largest consumer of natural rubber in the world. On the other hand, economic growth will increase the traffic load in terms of quantity, weight and speed. The burden of heavy traffic, road surface temperature reaches 70oC, high rainfall and the poor drainage, causing the road can be easily damaged. Therefore, paving way’s modification is required to fulfill those needs, one with the latex modified asphalt. The purposes of this study were to determine the effect of types and additional doses of latex in the asphalt toward penetration value and softening point which affecting the quality of asphalt pavement and to get the best mixture of asphalt to improve the quality of asphalt road pavement. This research methodology consiststed of two stages, namely preparation of raw materials (determination of the nature and characteristics of latex and latex depolymerization process) and the main research (the mixing process of latex into the asphalt and testing). Experimental design used in this study was Complete Random Factorial design with two replications for each treatment. Factors that influence were types and additional doses of latex rubber in the asphalt with each level of 8 and 3. There were two types of latex used in this study, namely concentrated latex which have dry rubber content (DRC) and depolimerization latex (latex which has decreased due to the molecular weight of polymer bonds break). Depolimerization latex in this study employed chemical methods with reduction-oxidation reaction (redox) with hydrogen peroxide (H2O2) as an oxidant and sodium hypochlorite (NaClO) as a reductant. In general, asphalt modification which has produced fulfill the quality requirements or quality standards for asphalt polymer at the value of penetration and softening point. Quality standard of penetration value is 50-75 dmm, whereas minimum value for softening point is 54oC. Modification of asphalt penetration values ranged from 49.33 to 61.25 dmm. There are two types of asphalt modifications outside the standard value, namely the modification of asphalt with a penetration of 49.52 and 49.33. Softening point value of asphalt modification ranged from 56.11oC to 65.27oC. The best asphalt modification was L5K5 sample (depolimerization latex with 5% additional doses of rubber in asphalt). Selection of the best asphalt modification was not only determined by the suitability of the penetration value and softening point with quality standard, but also was determined by homogenity between the asphalt dan rubber.
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Judul: Pengaruh Infeksi Virus pada Phytoplankton dan Racun yang Dihasilkan Phytoplankton dalam Model Interaksi Phytoplankton-Zooplankton
Abstrak: Interaction of phytoplankton and zooplankton can be considered as a prey-predator interaction, where phytoplankton as prey and zooplankton as predator. This interaction is modeled into mathematical equations that was investigated by Gakkhar & Negi (2005). This model studied the effect of viral infection on phytoplanktons and the toxin produced by phytoplankton. In this model, phytoplanktons are divided into two groups, suspectible phytoplankton and infected phytoplankton. Hopf bifurcation describes the stability changes of population. The Hopf bifurcation occurs when the rate of viral infection and the toxin quantity produced by phytoplakton were changed. Both phytoplankton and zooplankton populations stable when the infection rate and toxin quantity are low. If the viral infection rate and toxin quantity increase then phytoplankton and zooplankton populations became unstable. If the viral infection rate and the toxin quantity relatively high then the zooplankton population would lead to extinction
Keyword: zooplankton, phytoplankton, toxin, viral infection, Hopf bifurcation