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: Penggunaan Berbagai Jenis Lateks sebagai Bahan Tambahan pada Mortar untuk Aplikasi Beton Jalan Raya
Abstrak: Lateks karet alam dikenal sebagai bahan yang memiliki elastisitas tinggi. Dengan sifatnya tersebut, lateks diharapkan dapat memperbaiki kekakuan dan kekerasan pada beton. Penelitian ini bertujuan untuk mengetahui pengaruh jenis lateks, kadar karet kering, dan umur mortar terhadap bobot, kuat tekan, dan kuat lentur mortar. Penelitian ini menggunakan rancangan acak lengkap tiga faktorial. Faktor yang digunakan adalah jenis lateks (lateks pekat, lateks pravulkanisasi semi-EV, dan lateks pravulkanisasi semi-Ebonit), kadar karet kering (0, 2, 4, dan 6 %), dan umur mortar (7, 14, dan 28 hari). Jenis lateks, kadar karet kering, dan interaksi antara jenis lateks dan kadar karet kering sangat berpengaruh nyata (P < 0.01) terhadap bobot mortar. Bobot mortar tertinggi dihasilkan pada penggunaan jenis lateks pravulkanisasi semi-Ebonit (1383.25+18.90 gram) dan kadar karet kering nol persen (1389.33+22.15 gram). Semakin banyak kadar karet yang ditambahkan, maka bobot mortar yang dihasilkan semakin ringan.
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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