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Manajemen Aset Utilitas Bawah Tanah

Pemasangan, deteksi, pemeliharaan, pemetaan, dan pengelolaan aset utilitas bawah tanah menghadirkan tantangan bagi pemilik, insinyur, dan kontraktor. Praktik di seluruh industri mencakup penggunaan teknologi geofisika dan serupa untuk menentukan kedalaman dan lokasi, dan rencana as-built 2D yang terintegrasi dengan database GIS untuk manajemen informasi. Kelayakan menggabungkan model BIM 3D dari bawah permukaan untuk menggantikan rencana 2D untuk meningkatkan visualisasi dan manajemen data diperiksa dalam makalah ini. Mendapatkan gambaran yang akurat dari infrastruktur bawah tanah akan membantu meminimalkan kecelakaan penggalian karena tabrakan peralatan-utilitas dan mencegah kerusakan properti. Lebih lanjut, penyertaan fitur pengumpulan dan berbagi data otomatis yang diwujudkan melalui teknologi BIM dapat meningkatkan operasi kota pintar. Metodologi penelitian terdiri dari tinjauan mutakhir dari sistem manajemen utilitas bawah tanah saat ini, dikombinasikan dengan analisis statistik dari tanggapan survei yang diterima dari penyedia utilitas dan pusat panggilan di AS. Tiga kategori praktik utilitas diidentifikasi berdasarkan tingkat integrasi teknologi digital. Ditemukan bahwa sebagian besar perusahaan utilitas telah mengadopsi database GIS dengan rencana 2D, kedalaman dan informasi aset lainnya, sementara persentase yang lebih kecil dari penyedia telah mencapai integrasi GIS-BIM penuh, menggabungkan berbagai data aset. Kemajuan masa depan pada implementasi yang lebih luas tampaknya dibatasi oleh literasi digital personel dan biaya akuisisi dan aplikasi teknologi yang tinggi. Kerangka kerja tiga langkah untuk mengonversi rencana 2D ke model BIM 3D juga disajikan dan dibahas. Model proses yang diusulkan untuk tujuan ini memungkinkan pemanfaatan perangkat lunak yang tersedia secara komersial dengan kebutuhan minimal untuk pengkodean tambahan.

Kelayakan menggabungkan model BIM 3D dari bawah permukaan untuk menggantikan rencana 2D untuk meningkatkan visualisasi dan manajemen data diperiksa dalam makalah ini. Mencapai tujuan ini juga akan meningkatkan keamanan penggalian yang terkait dengan lokasi dan pemetaan utilitas bawah tanah sekaligus mencegah kerusakan properti. Selain itu, fitur konektivitas yang dibangun melalui integrasi teknologi digital diharapkan dapat memainkan peran yang bermanfaat dalam pengoperasian kota pintar di masa depan.

Infrastruktur bawah tanah, terutama di pusat kota, terdiri dari jaringan utilitas kompleks yang mencakup saluran listrik, gas, dan telepon, kabel serat optik dan televisi, saluran air, dan pipa saluran pembuangan, dan aset lainnya seperti sirkuit penerangan jalan, sistem drainase. , dan fasilitas pengendalian banjir. Ada lebih dari 35 juta mil utilitas layanan terkubur di Amerika Serikat, dan dengan urbanisasi yang berkelanjutan, jaringan ini terus diperluas dan ditingkatkan untuk mengakomodasi pertumbuhan populasi dan kebutuhan masyarakat yang terus berubah [1]. Penentuan, pencatatan, dan pengelolaan informasi kunci (lokasi dan atribut) yang akurat yang berkaitan dengan jaringan infrastruktur yang luas ini sering menimbulkan tantangan karena sulitnya akses fisik langsung ke bawah tanah dan tingginya biaya untuk membangun dan memelihara basis data yang up-to-date . Masalahnya diperparah dengan adanya utilitas yang ditinggalkan yang mungkin telah dipasang di tanah beberapa dekade yang lalu, yang catatannya mungkin tidak lengkap atau tidak ada. Dalam praktik kontemporer, rencana as-built dari jaringan bawah tanah aktif paling sering diwakili oleh gambar CAD 2D; namun, ketika informasi kedalaman kurang atau tidak akurat, nilai gambar menjadi dipertanyakan. Perubahan topografi akibat konstruksi baru, renovasi dan pemeliharaan, erosi tanah, serta keterbatasan alat pendeteksi dan kesalahan manusia dalam mencari utilitas, mengganggu keakuratan pemetaan ruang bawah tanah [2].

Kekhawatiran penting yang timbul dari ketidakpastian seputar jenis, posisi, dan konfigurasi aset bawah permukaan adalah kemungkinan tabrakan antara peralatan penggalian dan utilitas yang terkubur. Diketahui bahwa kecelakaan yang menyebabkan cedera atau kematian pada pekerja dan personel lokasi terjadi karena ledakan dan sengatan listrik saat tanah sedang digali untuk memasang utilitas. Kecelakaan ini juga menyebabkan kerusakan properti, menurunkan produktivitas penggalian, dan mengganggu layanan penting kepada konsumen. Dengan tidak adanya data geospasial yang andal, kemungkinan terjadinya kecelakaan seperti itu nyata [3].

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Cangkang Kelapa Sawit Sebagai Agregat

Beton Oil Palm Shell (OPS) dapat digunakan di berbagai bidang konstruksi. Untuk menentukan bidang aplikasi yang lebih akurat, penting untuk mengetahui dan memahami perilaku beton OPS dalam jangka panjang dan ketika berada di Cangkang Kelapa lingkungan yang agresif. Makalah ini menyajikan hasil studi yang dilakukan terhadap durabilitas beton OPS. Kapasitas penyerapan air, resistivitas listrik dan difusi nyata ion klorida telah diukur pada sampel beton yang berbeda. Selain itu, perilaku beton Cangkang Kelapa OPS terhadap karbonasi dipelajari di lingkungan yang kaya akan karbon dioksida. Hasil penelitian menunjukkan bahwa beton OPS memiliki daya serap 0,97 kg/m2·h1/2, resistivitas listrik 64,37 ·m dan koefisien difusi ion klorida sebesar 3,84 × 10-12 m2/s setelah 90 hari. Semua hasil beton OPS ini sangat mirip dengan beton dengan agregat normal dan beton ringan lainnya, yang berarti beton OPS memiliki sifat yang baik secara global dalam hal daya tahan.

Penggunaan tempurung kelapa sawit (OPS) sebagai agregat dalam beton merupakan alternatif yang menarik untuk mengurangi dampak negatif dari industri beton. Cangkang Kelapa Selama dua dekade terakhir, penulis telah menunjukkan potensi penggunaan OPS untuk menghasilkan beton struktural ringan [1] [2] [3]. Beton yang menggunakan OPS sebagai agregat memiliki kerapatan berkisar antara 1725 hingga 2050 kg/m3 yang setara dengan pengurangan 15% – 25% dibandingkan dengan kerapatan beton biasa [1]. Pengurangan ini mengarah pada pengurangan beban mati pada struktur, dan akibatnya pada pengurangan biaya konstruksi [4]. Namun, sifat mekanik beton menurun dengan meningkatnya Cangkang Kelapa kandungan OPS [5] [6]. Penurunan kinerja beton OPS ini disebabkan oleh sifat intrinsik OPS. Agregat alami ini sangat berpori, memiliki kapasitas penyerapan air yang tinggi dan memiliki daya rekat yang buruk dengan matriks semen. Mempertimbangkan kekurangan ini dan untuk meningkatkan sifat akhir beton, artikel sebelumnya membahas pengaruh perlakuan OPS yang berbeda terhadap sifat fisik dan mekanik beton [7].

Beton OPS dapat digunakan sebagai beton struktural, untuk konstruksi dinding penahan beban atau dinding pengisi. Mereka diharapkan bertahan dari waktu ke waktu, membutuhkan sedikit atau tanpa perawatan. Untuk memastikan hal ini dan mendorong penggunaan beton OPS dalam skala yang Cangkang Kelapa lebih besar, penting untuk menentukan perilakunya dalam jangka panjang dalam kaitannya dengan lingkungan di mana beton tersebut terpapar. Sangat sedikit penelitian yang berfokus pada perilaku jangka panjang beton OPS. Dalam studi ini, durabilitas beton OPS kemudian dievaluasi dengan memperhatikan lingkungan basah melalui indikator durabilitas klasik seperti kapasitas penyerapan air, resistivitas listrik dan difusi semu ion klorida. Selain itu, uji karbonasi dalam atmosfer terkontrol memungkinkan untuk mempelajari beton di lingkungan yang tercemar karbon dioksida.

2. Metode dan Bahan Eksperimen

2.1. Bahan-bahan yang digunakan

Semen yang digunakan adalah CEM I 42,5 dari perusahaan CIMTOGO yang diproduksi sesuai EN 197-1. OPS berasal dari lokasi produksi industri minyak sawit. Sebelum pengolahan dan/atau pemanfaatan, OPS dicuci dalam air untuk menghilangkan residu tanah dan lemak kemudian dikeringkan di udara terbuka. Mereka kemudian diayak: hanya partikel dengan diameter kurang dari 8 mm yang tertahan. Perilaku beton OPS telah dibandingkan dengan beton agregat berbasis granit biasa. Kerikil dan pasir yang digunakan untuk membuat beton, berasal dari sungai lokal di Burkina Faso.

2.2. Sifat Bahan yang Digunakan

Semen yang digunakan memiliki berat jenis, berat jenis dan luas permukaan BET masing-masing sebesar 3150 kg/m3, 1060 kg/m3 dan 2,96 m2/g. Kepadatan relatif OPS adalah 1340 kg/m3, kerapatan curahnya adalah 560 kg/m3 dan kapasitas penyerapan air 24 jam adalah 23,3%. Pasir yang digunakan memiliki massa jenis 2680 kg/m3. Massa jenisnya adalah 1530 kg/m3 dan modulus Kehalusannya adalah 2,90. Kerikil yang digunakan berada pada range yang sama yaitu berat jenis 2660 kg/m3 dan berat jenis 1510 kg/m3.

2.3. Persiapan Beton

Beton telah diproduksi menurut prosedur yang sama seperti untuk Traore et al. [9]. Tiga campuran beton dibuat dengan mengganti 0% (0N), 50% (50N) dan 100% agregat normal dengan OPS. Formulasi dilakukan dengan mempertimbangkan substitusi volume agregat kasar oleh OPS. Beton yang diuji terdiri dari 550 kg/m3 semen dengan rasio W/C 0,4. Rasio pasir terhadap semen dan OPS terhadap semen masing-masing adalah 1,66 dan 0,6. Kemampuan kerja beton dijaga konstan untuk semua formulasi, menggunakan superplasticizer pereduksi air yang tinggi.

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Study of a Photodegradant Polymeric Composite Containing TiO2 and Glass Residue

Glass Residue

Photodegradation or photocatalysis is a Glass Residue chemical degradation process that occurs when an inorganic semiconductor is exposed to ultraviolet (UV) light. UV light Glass Residue (wavelength 320 – 400 nm) has enough energy to detach an electron from the last layer of the semiconductor, leading to the conduction band, leaving a hole in the valence band. In these bands, chemical reduction and oxidation reactions occur, respectively. These reactions degrade diverse surface dirt, dissociating them into simpler and less offensive substances such as CO2 and H2O. In this work, we studied the potential of photocatalysis of a composite based on a semiconductor encapsulated in epoxy resin, in the degradation of Staphylococcus aureus, pathogen with a high degree of hospital contamination, in order to apply it to the construction in hospital facilities. The experiments were carried out with a fabrication of only epoxy resin tablets and tablets with the composite, at various concentrations of the semiconductor and glass powder. Through contamination of these tablets and their exposure to sunlight and the ambient light, contamination on their surfaces was verified. The results indicated potential photodegradation capacity of the composite.

The healthcare-associated infections (HAIs) are vectors of a severe public health problem in Brazil and worldwide. According to [1] , there is, besides of financial and social costs, the dissemination risks of antibiotic resistant bacteria.

It is one of the factors for these infections occurrences the non-efficient cleaning procedures. Studies done by [2] verified that the cleaning, as has been done, just causes the displacement of microbial loads. In [3] , a survey was done about Staphylococcus aureus surface contamination (on bed railings, bedside tables, doors knobs and nursery floors of the Clinics Hospital of Uberlândia Federal University), and it identified that 50% of the nurseries were contaminated.

Caring for biosafety is another important factor to avoid these occurrences and, some health professionals do not take it seriously. On a technical report, [4] describes biosafety failures found in a São José University Hospital (Belo Horizonte―Minas Gerais, Brazil) as remains of bandage, cirurgical materials and biological waste on the floor, not to mention that those responsible for the sector did not use the obligatory personal protective equipment (PPE). In addition, we verified that the nursing technicians did not do the correctly hands sanitation procedures and touched many patients, favoring the crusade contamination. The students who worked on the hospital wore make up, painted nails and lipstick, which propitiates the microbiota impregnation and diseases transportation.

Taking into consideration the careful procedures related to the use of PPE, the correct hands sanitization and materials disinfections, products that are responsible to disinfect the health services environments are still used. However, [5] said that the use of these products brings unwelcome secondary and dangerous effects such as skin dryness, eye irritation and mucosa; in case of some phenolic products, their use are prohibited in nursery and areas that are in contact with food, due their oral toxicity. Thus, to avoid the use of these aggressive chemical products should mean an environmental and social gain, by means of antimicrobial materials development.

One of the ways to diminish the use of aggressive products and the infecting agents quantities, is the advent of self-cleaning surfaces. The self-cleaning surfaces use incorporated catalysts, which promote chemical reactions on the surface interacting with infecting agents to prevent their actions, perhaps even killing them. This process, in which the catalysts act against the infecting agents, is called photocatalysis or photodegradation. The photocatalysis occurs by an irradiation of a photocatalyst, which is an inorganic semiconductor that has sufficient energy to induce an electronic excitation.

This energy has to be higher than the band gap. The band gap is the distance between the Valence Band (VB) and the Conduction Band (CB). Thereby, with this photonic energy, an electron-hole pair is generated, on which an electron is extracted from the VB, jumping to the CB. During this process, two regions are created, one positive hole (h+) on the VB and the other with a free electron (e−) on the CB [6] . These e− and h+ reduce and oxidize, respectively, chemical species on the photocatalysis surface, unless they recombine [7] .

According to [8] , these detached electrons in contact with water and O2 form oxidizing and reducing regions. Various infectants and dirtiness, both organic and inorganic, in touch with these regions, suffer electronic degradation, dissociating in simpler and less offensive substances, like CO2 and H2O. Some of these materials have already been using this mechanism, with the specific aim of removing infecting agents and dirt, besides other specific functions to which the photocatalysis can attribute.

To improve photocatalytical activity, there are studies about the use of glass mixed to the material and semiconductor. [9] used crushed recycled waste glass, by-product from drinking bottles, in replacement of part of the aggregate of the superficial layers from a photocatalytical concrete. The results showed a significant improvement on the photodegradant action. The authors justified this improvement due to light transmission property of the glass.

The aim of this paper was to study the capacity of a composite containing titanium dioxide (TiO2), an inorganic semiconductor encapsulated in an epoxy resin, to degrade Staphylococcus aureus bacteria with the photocatalysis mechanism. Thus, it was verified that the photocatalytical effect of the composite, when directly exposed to the sunlight and to the ambient light (indirect sunlight and fluorescent lamp light).

The percentages of semiconductors were based on [10] work. It is expected with the results of this paper that the composite shows potential to be used as a coating on health services that, on top of its photocatalyst capacity, also has durability, easy maintenance and is less harmful to the environment.

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Soil-Structure Interaction under the Effect of High Groundwater Table

Soil-Structure

This paper gives an account of a study performed for the raft foundation of a Soil-Structure commercial building of considerable height and area. A raft 175 m long was designed Soil-Structure without due consideration to the buoyancy effect due to high groundwater table as the building is near the sea. Although the raft was designed as an uninterrupted system, the designer used different, and insufficient, thicknesses for the foundation in order to lower costs. A 3D study was subsequently undertaken to analyze the settlements of the raft using finite elements. There was reasonable agreement between the computed and the measured settlements. However, the front block of the raft was observed to float as soon as pumping for lowering of the groundwater table was halted. This instigated the analyzers to tie this portion of the raft to the surrounding piled curtain that was used for excavation of the foundation pit, by means of reinforced concrete beams. The computations show that the heave of the floor was restrained at acceptable levels. It is planned to stop pumping in the near future and compare the computed and measured vertical movements.

It is nowadays standard practice to found high rise buildings on piled rafts mostly by unjustified approaches to the issue. This over conservative approach can partly be attributed to excessive reaction to the effects of potential earthquake damage as well as the general tendency to employ elastic methods for the calculation of footings. These methods emanate from the Winkler approach where only two parameters σ all and ks are needed (Winkler, 1867) [1] .

The Winkler hypothesis is the source of several defects. The semi-infinite medium, on which the foundation is placed, is represented by independent and rarely interconnected springs. Soil layering and the effect of the Ground Water Table are ignored. The software using the Winkler hypothesis results in conservative design simply because the concept of “allowable stress” for the soil is not a realistic parameter.

The geotechnical engineer has, in the past 30 years, been provided by numerical solutions such as the method of finite elements which enable him to model the soil as a non-linear-heterogeneous medium as well as including the mechanism of soil-structure interaction in the analyses.

This paper gives an account of the effort to refine the design of a raft foundation for a hotel building comprising three blocks that had been designed with an excessive amount of piles. In addition, a description of a solution foreseen to counteract the floating effect of rising Ground Water Table on the raft that has been cleared of the redundant piling system is given. A comparison of the computed and measured settlements is also made.

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Effect of the Shear Reinforcement Type on the Punching Resistance of Concrete Slabs

Concrete Slabs

Punching shear failure of flat concrete slabs is a complex phenomenon with brittle failure mode, meaning sudden structural failure and rapid decrease of load carrying capacity. Due to these reasons, Concrete Slabs the application of appropriate punching shear reinforcement in the slabs could be essential. To obtain the required structural strength and performance in slab-column junctions, the effect of the shear reinforcement type on the punching resistance must be known. For this purpose, numerous nonlinear finite element simulations were carried out to determine the behavior and punching shear strength of flat concrete slabs with different punching shear reinforcement types. The efficiency of different reinforcement types was also determined and compared. Accuracy of the numerical simulations was verified by experimental results. Based on the comparison of numerical results, the partial factor for the design formula used in Eurocode 2 was calculated and was found to be higher than the actual one.

Several methods exist for reinforcing concrete slab-column junctions against punching shear. The purpose of all types of shear reinforcement is to increase the shear capacity of concrete members and to add ductility to their post-peak load behavior [1] . Strength and ductility considerations are the most important issues in evaluating the effectiveness of the punching shear reinforcement in slabs, but economy and ease of installation can also have an effect on the choice of the reinforcement type. The most common and widely used solutions are reinforcing bars formed into stirrups, bent down flexural reinforcement or additional transverse inclined bars, structural steel sections and headed shear studs. We could not find any comprehensive, comparative analysis of all the mentioned reinforcing systems together, therefore, we decided to analyze them using non-linear finite element modeling by the commercial finite element software ATENA 3D v5.1.1. The results of this analysis may be used to find the best reinforcing solution in terms of punching shear capacity and economy for flat concrete slabs. For the verification of the numerical model test setups of three experimental campaigns, all together 40 experiments were reproduced.

In order to ensure that the numerical model represents the real experiments adequately, the results of three previous test series were used. The first set of experiments were performed under the guidance of Guadalini [2] , the second one was made by J. Alam [3] and the third one by Lips [4] . The experimental program of Guadalini consisted of 11 square slabs. The specimens were supported on a steel plate and the load was applied in 8 points. J. Alam’s experiments consisted of 15 square reinforced slabs. Each slab was subjected to concentrated loading at the geometric centre. Four steel blocks were used at each corner of the slab as support. Lips investigated sixteen square slab specimens with and without shear reinforcement. His principal aim was the analysis of flat slabs with large amounts of punching shear reinforcement.

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Compressive and Flexural Strength of Recycled Reactive Powder Concrete Containing Finely Dispersed Local Wastes

Recycled Reactive

The main objective of this experimental study is to investigate the behavior of Recycled Reactive Powder Concrete (RRPC) developed from finely dispersed local waste raw materials. In this study, Recycled Reactive RRPC was developed by utilizing local wastes (finely dispersed waste glass powder, waste fly ash and waste ceramic powder) together with Portland cement, fine sand, admixture, steel fibers and water through full replacement of silica fume as well as quartz powder for sustainable construction practice. In this study, all raw materials for making RRPC were analyzed for X-Ray Fluorescence analysis. For sustainability of local construction works, this study employed standard curing method at ambient temperatures instead of steam curing at higher temperatures. Moreover, hand mixing was used throughout the study. To evaluate the structural performances of the developed RRPC mixes, compressive and flexural strengths of RRPC were investigated experimentally and compared with the control mix. The experimental results indicated that replacing the silica fume fully by finely dispersed local waste glass powder (GP) and fly ash (FA) is a promising approach for local structural construction applications. Accordingly, a mean compressive strength of 62.9 MPa and flexural strength of 8.8 MPa were developed using 50% GP-50% FA at 28thdays standard curing. In this study, 17.56% larger compressive strength and 30.6% flexural strength improvements were observed as compared to the control mix.

As a prime composite construction material in Civil Engineering, the rapid rise in the cost of concrete raw materials has led to serious environmental and economic effects. Waste disposal from different sources in Africa has continued to be a complex challenge for the society, both environmentally and economically. Currently, waste materials from different sources are already in utilization as a concrete ingredient to produce either in conventional or in high strength level.

However, in Africa, local wastes are not well utilized for structural concrete applications due to different limitations. First, due to urbanization of cities in Africa, there are vast amounts of construction related wastes. For these wastes, there is a lack of sustainable construction solutions to manage effectively and to reuse with operational technologies to save consumption of biomass resources and related rising of concrete raw material prices for local constructions. Secondly, it is also a challenge to produce high performance concrete for structural applications from locally produced waste materials since less costly components of conventional concrete are eliminated by more expensive elements (such as silica fume) to produce newly emerging concretes such as reactive powder concrete. Thirdly, few ingredients of high performance concrete such as quartz powder need high energy for preparation from quarry site till milling process.

In recent times, a new generation concrete called reactive powder concrete is under development as an ultra-dense mixture of water, Portland cement, silica fume, fine quartz sand, quartz powder, super-plasticizer and steel fibers [1] – [6] . It has been developed through microstructural engineering using very fine powders: sand, crushed quartz and silica fume with low water content [7] [8] . It is also indicated that reactive powder concrete is characterized by high doses of fine-grained cement and a low water-cement ratio [9] , very high silica fume [10] and with the largest particle size as fine quartz sand with a particle size between 150 – 600 μm [11] . Compared to the conventional concrete, the particle size homogeneity, porosity, and microstructure properties were the primary improvements of RPC [12] [13] [14] [15] .

Moreover, reactive powder concrete exhibits greatly ultra-high strength, improved durability and high toughness characteristics compared with traditional or even high performance concrete since it is prepared by eliminating all the coarse aggregates, using very low water to binder ratio by incorporating pozzolanic materials, very fine sand, steel fibers and by applying pressure and heat treatment [16] [17] . Higher strengths can be achieved after water curing at 90oC for 3 days [9] . The incorporation of silica fume in RPC matrix remarkably enhances the steel fiber-matrix bond characteristics [12] . As the main constituent of a typical reactive powder concrete, silica fume plays a significant role in improving both rheological and mechanical properties [18] . As the reactivity of pozzolana is quantified by measuring the amount of Ca(OH)2 in the cement paste at different times, silica fume is much more reactive than fly ash or any other natural pozzolana [10] . However, it is noticed that high Silica fume content is one of the characteristics of Reactive Powder Concretes [19] , which is uneconomical for local construction. The silica fume content in RPC is normally kept in the range of 25% – 30% of the cementitious material [1] in which this quantity within the mix may lead to uneconomical mix. Moreover, higher percentage of silica fume requires higher percentage of water, but as the water/cement ratio increases, the strength of RPC mix decreases [10] . However, higher percentages of silica fume lead to higher dosages of superplasticizer [18] , which is also uneconomical. The development of Ultra High Performance Concrete (UHPC) in the concrete industry can be supported by the substitution of silica fume by another ultra-fine that lower cost, whose availability would not raise particular difficulties [20] . One of the best approaches to make concrete industries sustainable is the use of waste material in place of natural resources [21] . Additionally, to address the environmental concerns in the current situation, utilization of a supplementary cementitious material such as fly ash, or silica fume, or blast furnace slag, as raw material replacement is a value-added approach [22] . Nowadays, many industrial by-products have been standardized as supplementary cementing materials. Among these, fly ash was widely used as a supplementary cementitious material in concrete mixture mostly to replace cement [23] .

In this study, to address the above limitations, desired local wastes were collected from construction sites and cement factories and proposed to develop RRPC. Locally available wastes such as waste glass powder and fly ash were proposed in this study to reduce the silica fume requirement and related cost.

Waste glass powder was used in many research projects for partial replacement of ingredients in concrete production [24] . Waste glass could be used in concrete in powder form to suppress the ASR tendency [2] . Due to finer particles, glass powder is more reactive than silica fume. Because of its high silica content, the use of waste glass powder as a supplementary cementitious material is commonly practiced. But, as per different scholars, its pozzolanic properties will be improved when it was ground finer than 75 um and up to 10% cement replacement in concrete yields similar results to fly ash at the same replacement level after 90-days [25] . Replacing silica fume in UHPC mix designs with fine glass powder could save the silica fume content, which is costly and in limited availability [26] .

A number of studies have been studied on wastes to develop Reactive Powder Concrete (RPC) by replacing silica fume. Among those studies, Zhn et al. (2016) [27] investigated usage of recycled powder produced from waste of clay bricks with cement solids to develop environmentally-friendly and cost-saving RPC by replacing silica fume at 20%, 40%, 60%, 80% and 100% by weight. Accordingly, the results showed that as the replacement rate of silica fume in RPC by recycled powder increased, the flexural strengths were tended to decrease.

It was also observed that RPC containing high volume ground granulated blast furnace slag (GGBFS) for replacement of silica fume has been producing a compressive strength of over 250 MPa after autoclaving which was a satisfactory mechanical performance. Additionally, the amount of silica fume was decreased with increasing amount of GGBFS [28] . On conventional concrete, flexural strength of fly ash plus glass powder decreases by 1% at 11% of glass powder percentage and thereafter it increases by 8% after 30% of increase in glass powder after 28 days [2] .

In this study, finely dispersed waste glass powder, waste ceramic powder and waste fly ash were utilized for development of Recycled Reactive Powder Concrete (RRPC). The combination of finely dispersed waste glass powder and waste fly ash in three different percentages (at 80% – 20%, 50% – 50% and 25% – 75%) were utilized for full replacement of silica fume. The performance of developed RRPC was evaluated by compressive and flexural strength of RRPC.

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Predicting Nanocrystallites Development in Cement Pastes

Cement Pastes

Cement nanocrystallites constitute the binding phase Cement Pastes in concrete, a material that has been around for more than two thousand years and remains the most widely used of manufactured materials. Thanks to their size, Cement Pastes their disordered nature, their reprecipitation after combination with water, and their rapid evolution when the concrete sets, these nanostructures have only been subjected to careful investigation quite recently. Nanotechnology is now able to control their formation and exploit their evolution (shrinking and swelling) during the setting phase to produce a concrete with a strength and ductility close to those of steels. Furthermore, the analysis of basic nanoscopic reactions occurring during setting, and their modification by polymer additives acting at the interfaces, numerical modelling techniques are potentially able to predict big evolutions and properties of nanocrystallites. Here we discuss the future of these nanocrystallites in new applications.

Cementitious materials, known mainly in the form of concrete, are without doubt the oldest and the most widely used manufactured materials in the world, with more than a tonne produced per year and per person. They comprise a granular assembly bound together by a nanostructured matrix, also called the binding phase, which is the common feature of all such materials.

In fact, this nanostructured matrix is made up of hydrated chunks, each measuring a few tens of nanometers. These are hydrated calcium silicates, but often also hydrated calcium aluminosilicates or ferroaluminosilicates, in proportions that are non-stoichiometric with respect to the oxide content “Figure 1”.

These oxides (CaO, SiO2, Al2O3, Fe2O3, etc.) are already in the cement grain in crystallised form. Upon contact with water, part of these oxides dissolves, then diffuses under the strong concentration gradients and precipitates out again in the form of nanometric hydrates, which are also called nanocrystallites owing to their size and the fact that they are poorly ordered, midway between the amorphous and crystalline phases [1] .

As for any composite structure, it is this matrix that plays the determining role in the mechanical behaviour of the cementitious material. While the setting is under way, which may take a few hours or a few tens of hours, the cementitious material goes from a quasi-Newtonian liquid state to a viscoplastic state, then gradually acquires a visco-elasto-plastic behaviour, until finally it becomes a solid that is both very rigid, with Young’s modulus as high as a few tens of GPa, and very strong, with a compressive yield stress between about ten and a few hundred MPa, depending on the formulation.

It is the exceptional reactivity of this nanostructured matrix, and at room temperature, hence very economical, which is really the strong point of these cementitious materials, because one can control this or that property either at the prefabrication stage or at the building site, depending on the use which the material will be put to. Moreover, its very basic pH favours the use of passive or active reinforcement steel. However, if the setting stage is not properly controlled, the cement matrix can quickly become of very poor quality, exhibiting various pathologies such as carbonatation, sulfation, or the alkali reaction, which may affect both aesthetics and durability. It is also through the matrix that radioactive atoms can penetrate concrete when it plays the role of barrier against radioactivity produced in nuclear power stations. And it is once again the matrix that is responsible in cases of shrinkage and consequent crack formation, with a possible loss of structural integrity.

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Teknik Sipil Sebagai Profesi Modern

Teknik Sipil Sebagai Profesi Modern

Saat ini Teknik Sipil sebagai profesi modern, pekerjaan insinyur sipil cenderung sangat terspesialisasi, mencakup setiap aspek konstruksi publik dan swasta yang dapat dibayangkan, hal ini menbuat profesi teknik sipil menjadi profesi modern.

Survei

Survei adalah penggambaran posisi dan bentuk kenampakan medan alam atau buatan manusia pada sebidang tanah. Tanah harus disurvei sebelum bangunan dapat dimulai untuk menentukan batas hukum, kemiringan, potensi bahaya, dll.

Mekanika Tanah atau Rekayasa Geoteknik

Ini adalah cabang teknik sipil yang berhubungan dengan karakteristik substrat (tanah atau batuan) yang mempengaruhi kesesuaian situs untuk suatu bentuk konstruksi (misalnya, tegangan geser pada lereng, plastisitas tanah, rembesan tanah) dan sekelilingnya. struktur yang diperlukan untuk membuat situs aman untuk struktur tertentu (misalnya, fondasi, struktur drainase). Mekanika tanah penting tidak hanya untuk eksploitasi yang aman dan ekonomis dari lingkungan yang dikenal, tetapi juga untuk keberhasilan penggunaan lingkungan yang rapuh atau tidak bersahabat (misalnya, PERMAFROST).

Rekayasa Struktural

Teknik struktural, yang berhubungan erat dengan arsitektur, berhubungan dengan desain bangunan. Insinyur struktur menerjemahkan desain arsitektur ke dalam instruksi yang tepat tentang metode bangunan, bahan, konfigurasi struktur (misalnya, desain kolom dan balok), dll. Bangunan inovatif, seperti CN TOWER di Toronto, merupakan monumen abadi bagi keahlian insinyur bangunan.

Teknik Material

Praktisi dari cabang ini menetapkan spesifikasi bahan yang digunakan dalam industri konstruksi (misalnya, aspal yang digunakan pada perkerasan jalan, baja struktural) dan melakukan penelitian untuk memperbaiki bahan tersebut (lihat METALURGI).

Teknik Transportasi

Teknik transportasi melibatkan perencanaan, desain dan pembangunan fasilitas transportasi, termasuk jalan raya, rel kereta api, bandara dan pelabuhan, terminal bus, angkutan cepat dan struktur parkir.

Teknik Hidroteknik atau Sumber Daya Air

Ini berhubungan dengan irigasi, drainase, pengendalian bahaya air (misalnya banjir), pembangunan pelabuhan dan sungai untuk transportasi, peningkatan ketersediaan air dan perlindungan bangunan dari serangan air (misalnya, gelombang laut, aliran sungai normal).

Teknik Lingkungan

Teknik lingkungan berkaitan dengan meminimalkan dampak lingkungan dari skema rekayasa yang diusulkan. Ini biasanya mencakup teknik sanitasi, bagian penting dari PERENCANAAN PERKOTAAN DAN REGIONAL, dan berhubungan dengan desain distribusi air dan sistem pembuangan limbah untuk memastikan bahwa masyarakat memiliki air minum yang bersih dan sehat dan bahwa limbah tidak menjadi bahaya polusi.

Sebelum pergantian abad, seorang insinyur sipil akan merancang banyak struktur berbeda; misalnya, Thomas Keefer memulai survei sambungan kereta api Kingston ke Toronto, dan merancang saluran air untuk Hamilton, Ont (1859) dan Ottawa (1874) dan banyak pekerjaan umum lainnya.

Saat ini, insinyur sipil harus bekerja sama dengan spesialis dari banyak disiplin ilmu non-teknik dan subbidang teknik untuk menyelesaikan satu proyek. Misalnya, insinyur yang berspesialisasi dalam perencanaan kota dan teknik transportasi membantu arsitek dan perencana dalam desain awal pusat perbelanjaan.

Setelah lokasi dan ukuran pusat ditentukan, desain yang lebih rinci dihasilkan. Insinyur lalu lintas merancang pintu masuk dan keluar dan mengatur tempat parkir; insinyur struktur bekerja dengan arsitek untuk merancang bangunan; insinyur lain merancang sistem pemanas dan ventilasi, perpipaan dan kelistrikan dan bergabung dalam proses desain untuk menghasilkan serangkaian gambar dan spesifikasi teknik. Ini adalah dokumen dari mana insinyur konstruksi memperkirakan biaya pendirian pusat tersebut. Gambar dan spesifikasi ini merupakan bagian dari kontrak, yang menjelaskan hak dan kewajiban kontraktor, insinyur, dan pemilik, yang dibuat dengan bantuan pengacara yang berspesialisasi dalam hukum teknik.

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