Pengaruh Silica Fume sebagai Subtitusi Semen terhadap Nilai Resapan dan Kuat Tekan Mortar (Hal. 12-21)

ABSTRAKBeton dan mortar banyak digunakan sebagai bahan konstruksi di seluruh dunia. Meningkatnya permintaan beton dan mortar juga meningkatkan permintaan semen di pasar yang berdampak negatif bagi lingkungan. Industri semen menghasilkan sekitar 6 hingga 7 persen dari seluruh CO2 di seluruh dunia. Oleh karena itu, para peneliti mencoba mengembangkan gagasan tentangbeton ramah lingkungan, dengan mengurangi penggunaan semen dengan menggunakan bahan alternatif seperti silica fume. Silica fume adalah bahan pozzolan yang kaya akan silika dan dapat bereaksi kimia dengan kalsium hidroksida, membentuk gel kalsium silikat (CSH) pada beton. Tujuan dari penelitian ini adalah untuk menyelidiki pengaruh silica fume sebagai pengganti parsial semen terhadap nilai resapan dan kekuatan tekan mortar. Persentase silica fume bervariasi 0%, 5%, 10%, 12% dan 15%. Hasil pengujian menunjukkan nilai resapan minimum adalah 3,276% diperoleh campuran dengan 15% silica fume dan kuat tekan maksimum 312,574 kg/cm2 diperoleh campuran dengan 8% silica fume.Kata kunci: silica fume, nilai resapan, kuat tekan, mortar ABSTRACTConcrete and mortar are widely used as contruction materials. The increasing demand of concrete and mortar also increase the demand of cement in the market which has negative impact for environment. The cement industry produced for approximately 6 to 7 percent of all CO2 worldwide. Therefore, the researches try to develop the idea of green concrete with reducing the utilize of cement with using the alternative materials such as silica fume. Silica fume is a pozzolanic material that contain rich of silica and has chemical reaction with calcium hydroxide forming calcium silicate hydrate (C-S-H) gel in concrete.The aimed of this research is to investigate the influence of silica fume as partial replacement of cement on absoption and compressive strength of mortar.The percentage of silica fume were varied from 0%, 5%, 10%, 12% and 15%. The test result showed that the minimum absorption value is 3.276% obtain from the mixture with 15% of silica fume and the maximum compressive strength is 312.574 kg/cm2 obtain from the mixture with 8% of silica fume.Keywords: Silica fume, absorption, compressive strength, mortar

Evaluation of the anticorrosive performance of epoxy coatings containing new core/shell pigments

Purpose Core-shell is structured particles having several chemical compositions. The advantage of these particles arise from their specific design, to be used in decreasing costs by using inexpensive material (natural ore or waste material) as carrier for thin shell of active material. This study aims to prepare ferrites/silica core-shell pigments and compare their inhibition efficiency to original ferrites. These pigments have shells of different ferrites that comprise 10-15 per cent of the prepared pigments on silica fume. Silica fume which is the core is a byproduct in the ferro–silicon industry; this core comprises 85-90 per cent of the prepared pigments. Design/methodology/approach The prepared core-shell pigments were characterized using transmission electron microscopy analysis, energy-dispersive X-ray analysis and sequential wavelength dispersive X-ray fluorescence. These pigments were integrated in epoxy-based paint formulations, and the physical, mechanical and corrosion properties of dry films were examined. The corrosion properties were studied by using immersion test in 3.5 per cent NaCl for 28 days. Findings This study showed that these new eco-friendly and inexpensive pigments are similar to ferrites in their inhibition performance, i.e. they exhibited high corrosion prevention. Research limitations/implications Domestic waste materials were reused in paints and only simple modification was used, and then, their effectiveness showed similar performance to that of the original pigments. Originality/value Ferrite and ferrite/silica pigments are environmentally friendly pigments that can replace other hazardous pigments (e.g. chromates) with almost the same quality in their performance; also, they can be used in industries other than paints (e.g. paper, rubber and plastics composites).

Kapasitas Lentur Balok Beton dengan Bahan Tambah Abu Vulkanik Gunung Gamalama

AbstrakBeton merupakan bahan konstruksi yang mempunyai peranan yang semakin luas seiring dengan laju pembangunan saat ini. Dalam pelaksanaan beton di lapangan kadang digunakan bahan tambah (admixture) untuk memperbaiki sifat atau kinerjia beton. Bahan tambah dapat berupa bahan kimia, serat dan bahan buangan non kimia yang dicampurkan dengan perbandingan tertentu. Usaha yang dilakukan untuk meningkatkan kinerja dan durabilitas beton melalui penggunaan berbagai jenis bahan tambah seperti fume silica, slag, fly ash ataupun natural pozzolan (volcano ash). Bahan tambah yang digunakan yaitu Abu Vulkanik Gamalam (AVG). Penelitiana ini bertujuan untuk mengetahui pengaruh AVG terhadap kuat lentur beton. Benda uji yang digunakan adala balok berukuran (15x15x60) cm, Mutu beton K-225 dengan variasi penambahan AVG 20% terhadap berat semen. Pengujian kuat lentur dilakukan pada umur beton 28 hari. Hasil penelitian diperoleh bahwa pada beton dengan bahan tambah AVG kuat lentur balok sebesar 38,509 kg/cm², sedangkan untuk beton tanpa campuran Abu Vulkanik Gamalama (AVG) sebesar 29,448 kg/cm² atau terjadi kenaikan kuat lentur sebesar 23,53% Kata kunci: abu vulkanik, AVG, kuat lentur, beton. AbstractConcrete is a construction material where its role is broader along with the current development. In field, concrete is sometimes used as an admixture to improve the nature or performance of the concrete. Admixture can be in form of chemical material, fiber and non-chemical waste material that mix with certain ratio. Efforts conducted to improve the performance and durability of concrete through the use of various types of admixture, such as fume silica, slag, fly ash or natural pozzolan (volcano ash). Admixture used was Gamalama Volcanic Ash (AVG). The research aimed to find out the influence of AVG on concrete flexural strength. Testing materials used were concretes with size of (15x15x60) cm, K-225 concrete quality with variation of AVG addition of 20% against the cement weight. Flexural strength test was conducted on 28 days concrete. The research result found that concrete with admixture of AVG the concrete flexural strength was 38.509 kg/cm², whereas for concrete without Gamalama Volcanc Ash (AVG) mixture was 29.448 kg/cm² or an increase in the flexural strength of 23.53%.Keywords: volcanic ash, AVG, flexural strength, concrete.

Research and Application of Corundum Based Self-Flowing Castable Refractories

The effects of different deflocculants, fume silica, reactive micro-alumina powder and high alumina cement on the flowability of corundum based self-flowing castables were investigated using brown corundum as the main starting materials. The behavior of the castables was evaluated according to the self-flow value of the castables. The results showed that the best self-flow characteristics of corundum based self-flowing castables is obtained using sodium hexametaphosphate as deflocculant, suitable amount of alumina micropowder, fume silica, and high alumina cement as binders. The resultant castables were successfully used in the bottom of a refining ladle with capacity of 80 tons. The service life could match that of well blocks and meet the production requirements.

Comparative Study of Different Source of Silica-Filled Epoxy Resin

The mechanical properties and morphologies of fume precipitate and rice husk silica filled EP composites have been compared. The density, specific area of the silica decreases in the order of fume silica, precipitate silica and rice husk silica, while the silica size increases with the order above. It is shown that the fume silica/EP exhibits the highest flexural strength and modulus, followed by the precipitate silica/EP and the rice husk silica/EP. The rice husk silica/EP exhibits the highest in impact strength as silica is 1 phr. Over 5 phr of silica, fume silica/EP has the highest in impact strength, while the rice silica/EP is better than precipitate silica/EP. Scanning electron microscopy (SEM) results show that the fume silica has best dispersion and least filler agglomerates in matrix. The better dispersion will be responsible for the higher reinforcing and processing viscosity of the fume silica.