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"The study was conducted to explore the feasibility of using concrete sludge waste (CSW) and coconut fiber to manufacture paving blocks. The CSW were collected from a ready-mix concrete plant, while the coconut fibers were sourced from a coconut husk processing plant. The CSW was sun-dried for two days and only aggregates passing the No. 4 sieve were used to replace natural sand at replacement levels of 25%, 50% and 100% by weight with an aggregate/cement ratio of 1:3. The untreated coconut fibers were manually cut into a fiber length of 5 cm and were used in the paving block mix at proportions of 0%, 1%, 2% and 3% by weight of cement. The compressive strength, flexural strength, absorption and abrasion resistance of the resulting paving block specimens were tested to study whether or not the paving blocks has sufficient mechanical properties that allow them to have a quality classification grade under Indonesian national standards. The results of the study indicate that the paving blocks show sufficient compressive strength and abrasion properties to achieve a quality grade of A and B, respectively. However, the absorption level turned out to be the limiting constraint, where all of the paving block specimens resulted in an absorption level above the maximum allowable level under national standards.

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Studi ini dilakukan untuk meninjau kelayakan penggunaan limbah adukan beton (CSW) dan serat kelapa untuk memproduksi paving block. CSW diambil dari pabrik beton ready-mix, dijemur selama dua hari dan hanya aggregat yang melewati saring No. 4 digunakan sebagai subtitusi pasir alam pada tingkatan 25%, 50% dan 100% dengan rasio aggregat-semen 1:3. Serat kelapa dipotong secara manual menjadi panjang 5 cm dan digunakan dalam campuran paving block pada proporsi 0%, 1%, 2% dan 3% dari berat semen. Sifat mekanik paving block yang diuji meliputi kuat tekan, kuat lentur, absorpsi dan ketahanan aus. Hasil penelitian menunjukkan bahwa paving block yang dihasilkan menunjukkan kuat tekan dan ketahanan aus yang cukup untuk mencapai kualitas kelas A dan B, berdasarkan SNI 03-0691-1996. Namun, semua spesimen paving block yang dihasilkan menghasilkan absorpsi di atas batas yang ditentukan SNI 03-0691-1996."

"In this paper, the behavior of concrete subjected to biaxial compression and uniaxial fatigue is studied. The tests are performed on 100 x 100 x 100 mm cube specimens. Three Lateral stress levels ( a is defined as the ratio of stress in the horizontal direction that keeps constant during the testing procedure to the uniaxial compressive strength) 0, 0.25 and 0.5 are performed in the tests. The experimental stress-strain curves have been achieved. Empirical Relationship are proposed for predicting the maximum stress level as a function of lateral stress and fatigue life. The experimental results show that an increase of the horizontal stress leads to a change of failure mode and an increase of the maximum vertical load-carrying capacity . Also, the observation of the failure modes indicates that concrete possesses similar failure patterns under monotonic and fatigue compression is presented. Comparisons of the theoretical stress-strai curves with the experimental data indicate a good agreement."

"Concrete is a composite building material. Due to its increasing demand in the construction industry, its basic ingredients such as cement, fine aggregate and coarse aggregate have become extremely costly. Studies have been carried out to find better and more economical alternatives to these conventional building materials. One such alternative is fly ash, which can be used to partially replace cement. The main disadvantage of conventional concrete is its brittle failure, which can be avoided by using steel fibers. This study identifies the behavior of concrete with regard to impact resistance and its mechanical properties by adding hooked-end steel fibers at levels of 0, 0.75, 1.15 and 1.55% and partially replacing 40% of the cement with 40% fly ash. In addition to the control concrete, there has been four mixes with respective addition of steel fibers. The behavior of normal and fly ash concrete with steel fibers was compared. The combination of fly ash and steel fibers provided a homogeneous and very rich mix, with a delay in the setting time of the concrete. Of all the mixes, the one containing 40% fly ash and 1.55% steel fibers proved to be the best, with a maximum increase in strength of 17% in compression, 25% in split tension, 30% in flexure and 95% in impact energy at 56 days. A multiple linear regression model was also formulated using SPSS (Statistical Package for Social Sciences) software, through which corresponding equations were developed to predict the strength and energy at 28 and 56 days. The equations were also used to predict the strength of the mixes from other researchers’ experimental work. The predicted results corresponded well with the experimental results and the percentage difference was found to be less than 5%."

"Pembangunan infrastruktur di Indonesia yang mengalami peningkatan kuantitas dari tahun ke tahun. Pada pembuatan beton di Indonesia sebagian besar menggunakan semen untuk membuat jembatan, jalan tol, gedung dan lain-lain. Hal itu dapat menyebabkan timbulnya emisi gas CO2 pada perusahaan pembuatan semen di Indonesia. Untuk itu diperlukan bahan pengganti semen untuk pembangunan infrastruktur yang lebih ramah lingkungan. Dalam penelitian kali ini dilakukan pembaharuan untuk mengganti beton berbasis semen Portland dengan bahan yang baru, yaitu beton geopolimer. Beton geopolimer yang dibuat pada penelitian kali ini menggunakan terak baja yang berasal dari tailing blast furnace (GGBFS). Dari hasil uji bahan agregat kasar dan halus, dilakukan studi berbagai rancang campuran beton geopolimer dengan variasi umur beton 28, 35, dan 56 hari. Selain itu, komposisi rasio activator/terak juga divariasikan menjadi 0,35 dan 0,23. Dari penelitian ini, didapatkan hasil yang paling optimum saat menggunakan rasio aktivator/terak sebesar 0,35 dan umur beton selama 28 hari untuk uji tekan (5,71 MPa) dan uji belah (8,43 MPa), sedangkan untuk uji lentur (1,23 MPa) pada umur beton selama 35 hari dengan rasio activator/terak yang sama.

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Infrastructure development in Indonesia has increased in numbers for years. In Indonesia, concrete production to construct bridges, toll roads, buildings, etc. uses cement for most cases. Cement manufacturing in Indonesia produces CO2 gas emissions. For this reason, a cement substitute is needed for more environmentally-friendly infrastructure development. In this research, an update was carried out to replace Portland cement-based concrete with a new material, namely geopolymer concrete. The geopolymer concrete made in this research uses steel slag from the tailings blast furnace (GGBFS). From the test of coarse and fine aggregates result, studies were conducted oon various designs of geopolymer concrete mixtures with the concrete age varies from 28,35, to 56 days. In addition, the composition of the activator/slag ratio varies from 0.35 to 0.23 as well. This study points that the most optimum results were obtained when using an activator/slag ratio of 0.35 with a concrete age of 28 days for the compressive test (5.71 MPa) and split test (8.43 MPa). Whereas on the bending test (1.23 MPa), the optimum results were obtained at the concrete age of 35 days with the same activator/slag ratio."

"The Aluminum 7075 (Al 7075) alloy is a precipitation hardening material instead of a strain hardening material. These mechanical properties are of a particular microstructure obtained by thermo-mechanical treatments. Among other things, this is a complicated microstructure which is responsible for the mechanical performance. The evolution of the mechanical properties of aluminum alloys is dependent on aging time parameters after heat treatment. In this study, the material has undergone a tempering heat treatment followed by a series of tensile tests. The experimental data (tensile curves in three directions during maturation time) is used to describe the evolution of the mechanical characteristics in terms of loading directions and maturation time, denoted respectively as: Ψ and t. The tensile curves are the source of data to begin the problem of identifying the behavior law of studied material using Barlat?s model and Hollomon?s isotropic hardening law. Thus, from the identified parameters (anisotropy coefficients and hardening coefficients), the evolution of the Lankford coefficient, deformation rate and load surfaces during the maturation time for three load directions (0°: rolling direction, 45° and 90°) are described. This study allows optimizing the response of the aluminum alloy to plastic strains, resulting from forming processes measured against the best time during maturation and the best load direction."

"The Aluminum 7075 (Al 7075) alloy is a precipitation hardening material instead of a strain hardening material. These mechanical properties are of a particular microstructure obtained by thermo-mechanical treatments. Among other things, this is a complicated microstructure which is responsible for the mechanical performance. The evolution of the mechanical properties of aluminum alloys is dependent on aging time parameters after heat treatment. In this study, the material has undergone a tempering heat treatment followed by a series of tensile tests. The experimental data (tensile curves in three directions during maturation time) is used to describe the evolution of the mechanical characteristics in terms of loading directions and maturation time, denoted respectively as: ? and t. The tensile curves are the source of data to begin the problem of identifying the behavior law of studied material using Barlat’s model and Hollomon’s isotropic hardening law. Thus, from the identified parameters (anisotropy coefficients and hardening coefficients), the evolution of the Lankford coefficient, deformation rate and load surfaces during the maturation time for three load directions (0°: rolling direction, 45° and 90°) are described. This study allows optimizing the response of the aluminum alloy to plastic strains, resulting from forming processes measured against the best time during maturation and the best load direction."