PERBAIKAN SIFAT FISIK DAN REAKTIFITAS FLY ASHSEBAGAI CEMENTITIOUS PADA BETON Improvement of  The Physical Properties and Reactivity of Fly Ash As Cementitious On ConcreteErwin Rommel1, Dini Kurniawati2, Arman Putra Pradibta31,2,3Jurusan Teknik Sipil Fakultas Teknik – Universitas Muhammadiyah MalangAlamat korespondensi : Jalan Raya Tlogomas 246 Malang 65144email : erwin67pro@yahoo.comAbstractVariety of materials researchs is curently underway to develop environmentally friendly concrete is very varied in order to meet the demands of higher cement production. One way is to replace some of the cement with the rest of coal burning PLTU or commonly known as fly ash. Purpose of this study was to determine the effort to improve the physical and chemical properties of fly ash as a partial cement replacement material and influence the reactivity of fly ash has improved by incubating the silica synthesis. The physical examination, fly ash decreased in term of quality and fineness increase in the adsorption of the water content. The chemical test showed that a decline in the percentage of the elements Si and Al but an increase in elemental Fe. It also affects the content of the main compound SiO2 and Mullite are dominated by 77 – 80% fly ash decreased after a treatment process. Reactivity test using XRD found that fly ash has decreased the amount of 3,47% amorphous structure after experiencing the treatment. Fly ash that would be dominated by the reactive silica is a form of amorphous silica, is because the contact surface af amorphous silica is greater than crystalline. This reduction causes no more reactive fly ash after going through the process of treatment and no better used as a partial replacement for cement in concrete. Keyword : fly ash, environmentally friendly concrete, and synthesisAbstrakTeknologi bahan dan teknik untuk mengembangkan beton ramah lingkungan sangat bervariatif guna menjawab tuntutan produksi semen yang semakin tinggi. Salah satu caranya ialah mengganti sebagian semen dengan sisa pembakaran batubara dari PLTU atau yang biasa disebut fly ash. Tujuan dari penelitian ini adalah untuk mengetahui upaya memperbaiki sifat fisik dan kimia dari fly ash sebagai material pengganti sebagian semen serta pengaruh reaktifitas dari fly ash yang telah mengalami perbaikan dengan pensintesisan silika. Hasil pemeriksaan fisik, fly ash mengalami penurunan dalam segi kualitas kehalusan dan mengalami kenaikan dalam penyerapan kadar air setelah mengalami proses treatment.Hasil pemeriksaan kimia menunjukkan bahwa terjadi penurunan persentase pada unsur Si dan Al akan tetapi mengalami peningkatan pada unsur Fe. Hal tersebut juga berpengaruh terhadap kandungan senyawa utama SiO2 dan Al6Si2O13 (Mullite) yang mendominasi fly ash sebesar 77 – 80 % mengalami penurunan setelah mengalami proses treatment. Hasil uji reaktifitas dengan menggunakan XRD didapatkan bahwa fly ash mengalami penurunan jumlah struktur amorf sebesar 3,47 % setelah mengalami proses treatment. Penurunan ini menyebabkan fly ash tidak lebih reaktif setelah melalui proses treatment dan tidak lebih baik digunakan sebagai bahan pengganti sebagian semen dalam beton secara keseluruhan.Kata Kunci :  fly-ash, beton ramah lingkungan,  sintesis

PENGARUH PEMBERIAN JUMLAH DAN RASIO (L/d) SERAT BENDRAT TERHADAP SIFAT MEKANIK BETONThe Influence of Steel Fiber Amount And L/D ratio to Mechanical Properties of ConcreteAhmad Hafiz S.G1, Erwin Rommel2, Lukito Prasetyo31 Staf Badan Perencana dan Pengembangan Kampus UMM2,3 Jurusan Teknik Sipil Universitas Muhammadiyah MalangAlamat korespondensi : email: erwin67pro@yahoo.com, ahafizsg16@gmail.com, prasetyo.lukito@gmail.comAbstractFiber concrete is the concrete which is mixed with fiber. The fiber was mixed into the concrete with the addition of fiber percentage. In this research, the fiber used was bendrat fiber. It had a diameter 0.8 mm which was cut be 1 cm, 2 cm, and 3 cm. Thus, the ratio (l/d) of fiber bendrat got 12,5 ; 25; and 37,5. Moreover, the amount of additional fiber used was 1 %, 2 % and 3 % from the amount of each cement ratio.In this research made 60 test concrete cylinder (150x300) mm in each of the 30 cylinder for testing compressive and 30 cylinders for testing tensile of the concrete. As for testing shear strength made 30 concrete specimen the shaped doubel-L (200x300x75) mm.The research results obtained that the wearing of a fiber ratio L/d = 12.5 will be able to enhance the tensile strength and shear stregth of concrete where fiber consumption bendrat as much as 3% obtained the greatest tensile strength 2,41 MPa or increased twice from the concrete without fibres, while for maximum shear strength reach 4,94 MPa with an increase of 54% compared to concrete without fibresKeywords: fiber concrete, steel fiber, tensile strength, shear strengthAbstrakBeton serat adalah bahan beton yang dicampur dengan serat dengan persentase tertentu. Dalam penelitian ini,serat yang digunakan adalah serat bendrat. Serat bendrat berdiamtere 0,8 mm dipotong-potong dengan panjang 1 cm, 2 cm dan 3 cm sehingga menghasilkan rasio L/d masing-masing 12,5; 25; dan 37,5. Sedangkan banyaknya serat yang ditambahkan terhadap volume berat yang digunakan masing-masing ; 1%, 2% dan 3%. Dalam penelitian dibuat 60 silinder diameter 150 mm dengan tinggi 300 mm masing-masing 30 silinder untuk pengujian tekan dan 30 silinder untuk pengujian tarik belah beton. Sedangkan untuk pengujian geser beton dibuat 30 specimen beton berbentuk doubel-L berukuran (200x300x75) mm. Hasil penelitian diperoleh bahwa pemakaian serat dengan rasio L/d=12,5 akan dapat meningkatkan kuat tarik dan kuat geser beton dimana pemakaian serat bendrat sebanyak 3% diperoleh kuat tarik terbesar 2,41 MPa atau meningkat 2 kali dari beton tanpa serat, sedangkan untuk kuat geser maksimal mencapai 4,94 MPa dengan kenaikan 54% dibandingkan dengan beton tanpa serat.Kata kunci : beton serat, serat bendrat, kuat tarik, kuat geser.

TINJAUAN PERMEABILITAS DAN ABSORBSI BETON DENGAN MENGGUNAKAN BAHAN FLY ASHSEBAGAI CEMENTITIOUSReview The Use of Fly-ash as a Cementitious to Concrete Absorbtion and PermeabilityErwin Rommel1, Yusuf Wahyudi2, Rozy Dharmawan31,2Jurusan Teknik Sipil Universitas Muhammadiyah Malang Jl. Raya Tlogomas 246 Malang 65144 Telp. (0341) 464318-319 Pes. 130 Fax. (0341)4604353Alumni Jurusan Teknik Sipil Universitas Muhammadiyah MalangEmail: erwin67pro@yahoo.comAbstractFly-ash material improvement efforts through the process of synthesis of silicawith the activator NaOH 5M solution has been done to improve the properties of reactivity. Repair of concrete permeability resistance trying to do with fly-ash as cementitious 10%, 20%, 30%, 40%. Concrete permeabilitytesting done by making 30 specimen (20x20x12) cm. Beside that alsocarried out testing on the absorption testing by making cylinder concrete (15x30) cm as much as 30 specimen. The comparison is done as the creation of concrete using fly-ash in a conventional fly-ash on concrete. The result of absorption obtained that the use of fly ash tend to be able to reduce the absorption on the concrete, both the conventionalfly-ash or fly-ash treatment. Even the usage of fly-ash  above20% is not contrastive in the absorption of concrete given the fly-ash treatment or conventional fly-ash. The capability of  concrete permeability looksbetter onconcrete using fly-ash treatment comparedto conventional fly-ash.Keywords : fly ash , permeability , absorptionAbstrakUpaya perbaikan material fly-ash melalui proses sintesis silika dengan aktivator NaOH 5M telah dilakukan guna memperbaiki sifat reaktifitasnya. Perbaikan ketahanan permeabilitas beton coba dilakukan dengan mengganti 10%, 20%, 30%, 40% berat semen dengan bahan fly-ash hasil rekayasa. Pengujian permeabilitas beton dilakukan dengan membuat 30 benda uji berukuran (20x20x12) cm. Disamping itu dilakukan juga pengujian pada ketahanan absorbsi beton dengan membuat benda uji silinder diameter 15 cm tinggi 30 cm sebanyak 30 benda uji. Sebagai pembanding dilakukan pembuatan beton dengan menggunakan bahan fly-ash konvensional (tanpa perbaikan) pada campuran beton. Hasil pengujian absorbsi diperoleh bahwa penggunaan fly ashcenderung dapat mengurangi nilai absorbsi pada beton, baik pemakaian fly-ash konvensional maupun fly-ash yang telah melalui hasil rekayasa. Bahkan pemakaian fly-ash diatas 20% tidak memperlihatkan perbedaan nilai absorbsi pada beton yang diberi fly-ash hasil rekayasa maupun fly-ash konvensional. Untuk kemampuan permebilitas terlihat lebih baik pada beton yang memakai fly-ash rekayasa dibandingkan dengan fly-ash konvensional.Kata Kunci : fly ash, permeabilitas, absorbsi

Foam concrete is an alternative wall material that can be used in tropical buildings because of its insulation properties, good thermal conductivity, and sound absorption coefficient when compared with the normal concrete. The percentage of foam agent used in its production affects density and compressive strength. Furthermore, the use of fly-ash also has an effect on its mechanical and insulation properties. In this study, 40 units of foam concrete specimen (200x200x20) mm were tested for thermal conductivity, and cylinder (dia-100x20) mm for sound absorption. The mixture used for the concrete includes cement/sand ratio of 1:2.75 with w/c 0.425 and addition of 20% fly-ash as a cementitious material and foaming agent (ratio fa/w 1:20) at 1%, 2%, 3% and 4% by weight of cement paste, respectively. The result showed that foam concrete with 20% fly-ash and 2% foaming agent or more has a density below 2000 kg/m3 with a maximum compressive strength of 13.24 MPa. The highest sound absorption coefficient was obtained to be a = 0.89 at 20% fly-ash and 4% foaming agent. The thermal conductivity (k) of foam concrete was found to have increased using a 20% fly-ash and 1% foaming agent compared to the mixture without fly-ash at a value of 0,898. It was discovered that the use of fly-ash on foam concrete has the ability to improve thermal conductivity and sound absorption.

There is an immediate need for reinforced concrete (RC) construction to protect natural resources and environmental sustainability due to a gradual decline in natural resources and a problem in many waste disposal sites used. Reducing natural stones as aggregates in concrete using agriculture waste as aggregate to produce lightweight concrete is an effective way to reduce this problem. Lightweight concrete applications for structural design have long been applied because they significantly benefit design and construction costs. However, limited information about the structural performance, such as the bond strength, the compressive strength can be a barrier to applying lightweight concrete in the construction industry, as inadequate bond strength can result in structural deficiencies in RC structures. Therefore, to launch the use of lightweight concrete as a general material of construction, this research was conducted to review the current information on the mechanical behaviour of corroded lightweight concrete structures, while agricultural solid wastes were used as a lightweight aggregate in the concrete mixture.