Influence of supplementary cementitious materials on microstructure and transport properties of spacer-concrete interface

Reinforcement spacers are a critical component of concrete structures. Their presence affects microstructure and transport properties of concrete cover though this is not widely appreciated. This paper presents the first study to determine whether the negative effects of spacers can be mitigated through the use of supplementary cementitious materials such as silica fume, fly ash and blast-furnace slag. Concrete samples (>200) with different spacers, binders, curing and drying regimes were prepared and tested for diffusion, permeation, absorption, electrical conductivity, carbonation and microstructure. It was found that spacers increase all transport properties, the extent depending on type of spacer, drying regime and transport mechanism. The spacer-concrete interface is weak, porous and micro-cracked, and this lowers the resistance of concrete to ingress of aggressive agents. The beneficial effects of SCMs (strength enhancement and densification) and prolonged curing (120-day) are insufficient to overcome the negative effects of spacers. Implications for durability are discusse

Improving the Spacer-Concrete Interface for Bond Strength and Durability

Spacers are important devices in reinforced concrete that are used to support reinforcing steel during concreting in order to achieve the required concrete cover. They are placed at every meter length or less of steel reinforcement and left permanently in the structure. However, it has been shown that the weak interface between spacer and concrete is highly porous and microcracked. This lowers the resistance of the concrete cover to ingress of aggressive agents causing degradation. This study aims to address this problem by improving spacer design to enhance bond strength and durability of the spacer-concrete interface. Cementitious spacers with a range of surface textures were produced prior to casting into concrete. Samples were prepared with CEM I Portland cement at a water/cement (w/c) ratio of 0.4 and cured for 3, 7, and 28 days in a fog room and then conditioned at 50°C to equilibrium moisture content. The spacer-concrete interface was then tested for tensile bond strength and mass transport properties including oxygen diffusivity, oxygen permeability, water absorption and electrical conductivity. The results were compared against control samples made of either the entire cementitious spacer or concrete. The measured surface properties were then correlated to the measured bond strength and transport properties to establish the effects of surface texture on the spacer-concrete interface

The Influence of Individual, Environmental, Technology, and Manufacturing Factors on Iraqi Gas and Oil Companies

Implementation of agile technology and its effects on individuals, the environment, technology, and manufacturing factors are the focus of this study, with a special focus on agile technology's moderating effect. Consequently, this study investigates a unique conceptual framework to extend the notions of agile technology implementation in order to address this research gap. This conceptual framework has been subjected to empirical testing, with 380 population-representative employees serving as participants. This study establishes the inclusion requirements for Iraqi oil and gas firms. Using a self-administered questionnaire, data are collected and analyzed using structural equation modelling (PLS). The finding shows that there are various factors that have a positive effect on oil and gas companies in Iraq. The implementation of agile technology also has a partially significant positive moderating effect on these factors, indicating that agile technology can amplify the positive impact of these factors. This can lead to profits and the ability for companies to achieve long-term goals and a competitive advantage in the business environment while achieving sustainability in the oil and gas field. These findings are significant, as they suggest that the implementation of agile technology can have a positive impact on the oil and gas industry in Iraq, leading to long-term sustainability and profitability

Manajemen Rantai Pasok Komoditas Cabai pada Agroekosistem Lahan Kering di Jawa Timur

Komoditas cabai merupakan salah satu komoditas hortikultura yang mendapatkan prioritas pengembangan. Komoditas cabai merupakan komoditas sayuran tidak bersubtitusi dan tergolong komoditas bernilai ekonomi tinggi. Permasalahan utama adalah sering terjadi gejolak harga yang memiliki pengaruh cukup signifikan terhadap inflasi. Tujuan penelitian adalah untuk menganalisis kinerja kelembagaan manajemen rantai pasok komoditas cabai dari hulu hingga hilir. Hasil kajian menunjukkan kinerja USAha tani cabai merah besar, cabai merah keriting, dan cabai rawit cukup menguntungkan dengan keuntungan berkisar antara Rp24,44–83,8 juta/musim/ha, dan dengan nilai R/C ratio bevariasi antara 1,62–2,89 yang merefleksikan USAha tani cabai sangat layak untuk terus diusahakan. Secara nominal berturut-turut nilai tambah terbesar adalah pada pedagang pengecer, pedagang pengumpul, pedagang besar. Meskipun nilai tambah pada pedagang besar dan pedagang pengumpul desa lebih kecil dari nilai pedagang pengecer, namun karena omzet penjualan cabai yang jauh lebih besar maka secara keseluruhan keuntungan yang didapat pedagang besar adalah yang paling besar, kemudian menyusul pedagang pengumpul desa, dan terakhir pedagang pengecer. Strategi untuk meningkatkan efisiensi tata niaga dapat dilakukan dengan pengembangan manajemen rantai pasok komoditas cabai merah secara terpadu

Analisis Sifat Kekuatan Tarik Dan Kekuatan Bending Komposit Hibryd Serat Lidah Mertua Dan Karung Goni Dengan Filler Abu Sekam Padi 5% Bermatrik Epoxy

The use of composite materials is growing at over the development of manufacturing industry. Composites sansevieria and hibiscus canabinus with the addition of rice husk ash filler. The purpose of this study was to analyze the tensile strength and bending strength of hybrid composites sansevieria and hybiscus canabinus with rice husk ash filler epoxy bermatrik with random fiber direction. Variation of fiber volume fraction sansevieria and hybicus canabinus is 0%:35%,10%:25%, 15%:10%, 20%:15%, 25%:10%, 35%:0%. Method for making composite specimens in the form of hand lay up with a fiber length of 2cm. Testing was done by bending test following the ASTM standard D790 tensile test and ASTM D3039 standards. The results showed that the composites with rice husk ash fillers higher bending strength and the strength of its appeal compared to the composite without using rice husk ash fillers, where the highest bending strength on volume fraction 0%/35% as big as 32,00 MPa (using filler), and kekutan lowest bending the volume fraction 0%/35% as big as 21, 69 Mpa (without filler). While the tensile test has the highest power in the volume fraction 15%/20% as big as 8,24 MPa (using filler), and the lowest tensile strength on volume fraction 0%/35%  as big as 3,43 MPa (without filler)

Present Status of Marine Radioecology in Jakarta Bay

Operation of nuclear facilities such as research reactor and it’s supporting installation in Serpong Nuclear Area may release controlled  radionuclides to Cisadane River and then it would flow to Jakarta Bay. There are limited marine radioecology studies or radionuclides monitoring  at Jakarta Bay. Therefore monitoring of 239/240Pu and 137Cs was carried out from Tanjung Pasir to Tanjung Kerawang. The ERICA Assessment Tool was used to evaluate radiological risk in the marine environment of Jakarta Bay area. The 137Cs concentration in sea water and sea sediments were in range of  0.17 – 1.17 Bq.m-3 and  0.34 – 1.21 Bq.kg-1, respectively. Moreover,  result of 239/240Pu measurement showed that concentration at sea water and sea sediment were range from < MDA – 0.53 mBq.m-3 and 2.64 – 55.70 mBq.kg-1 respectively. The results of risk analysis were indicated that all the total dose rates per organism were millions time lower than the screening    rate (10 mGy.h-1)

Arterial stiffness index as a marker for the occurrence of atherosclerotic cardiovascular disease

Background: Arterial functional changes reflected by vascular stiffness might occur at early stages of cardiovascular disease before the morphological alterations reflected by increasing the intima media thickness and it is widely used as a very sensitive indicator of functional vascular damage. Objectives: This study is aimed to correlate ultrasound detected vascular functional changes with the severity and extent of coronary artery disease. Patients and methods: Sonographic scans were performed on 100 Patients (61males, 39 females) with an age range of (40-65years) for measuring carotid and brachial arteries end diastolic and end systolic diameters to calculate vascular stiffness index . Coronary CT angiography has been used to visualize the atherosclerotic plaque to define the degree of luminal stenosis by creation of high-quality images which are obtained by the multislice CT spiral scanners. Results: A positive statistical correlation was observed between the stiffness index of both carotid and brachial arteries in single coronary lesion (SCL), multiple coronary lesion (MCL) and control groups in addition to the significant positive correlation between both arteries stiffness index with the percentage of coronary artery stenosis in SCL group. Significant difference between the arterial stiffness index among the study groups is only noticed for carotid artery between the control and MCL groups (p<0.05). Conclusion: Conduit arterial stiffness index is a good indicator of the severity and extent of coronary artery disease