Behaviour of alkaline cement mortars reinforced with acrylic and polypropylene fibres

[EN]In the present work, the behaviour of alkaline cement mortars reinforced with fibres of different nature (acrylic and polypropylene fibres) is studied. Also the chemical stability of those fibres in strong alkaline medium has been' investigated. Three different matrixes have been used: glass blast furnace slag activated with NaOII 2M (room temperature, 22 "C); fly ash activated with NaOII 8M, cured at 85 "C during 24 hours and 50% fly ash / 50%j slag activated with NaOII 8M, room temperature. The fibre content was 0,2 and 7% in mortar volume. The tests carried out were: tenacity and tenacity index, impact resistance and drying shrinkage. On the specimens tested, a microstructural study by SEM/EDX was carried out. The results obtained have demonstrated the following: a) The acrylic and polypropylene fibres are stable in strong basic media, although the first undergo hydrolysis/ hydration processes showed by the alteration of the surface texture, b) with low fibre contents (0,2%) in volume), tenacity and tenacity index of these mortars remain unaffected. With higher contents (1%)), an increase of the corresponding values is produced. This increment is higher in mortars with alkaline activated slag, c) For the three matrixes studied, the polypropylene fibres increase the impact strength in higher degree than the acrylic ones. The reinforcement effect is more significative in matrix A and when the fibre content is /% in volume, d) the shrinkage of these mortars is modified depending on the matrix and fibre type. In mortars of activated slag, fibres do not reduce the shrinkage. In mortars of activated fly ash reinforced with acrylic fibres, shrinkage is lower than those containing polypropylene fibres are. Finally, in mortars of fly ash/ activated slag, the two fibres decrease the drying shrinkage.[ES] En el presente trabajo se estudia el comportamiento de morteros de cementos alcalinos reforzados con fibras de distinta naturaleza (acrílica y de polipropileno). Se ha evaluado también la estabilidad química de dichas fibras en medios fuertemente alcalinos. Se han utilizado tres matrices diferentes: escoria vitrea de horno alto activada con NaOII 2M, temperatura ambiente (22 "C); ceniza volante activada con NaOH 8M, curada a 85 "C durante 24 horas y 50%ceniza/50%escoria activada con NaOH 8M, temperatura ambiente. El contenido de fibra fue del 0,2 y J% en volumen de mortero. Los ensayos realizados fueron: tenacidad e índice de tenacidad, resistencia al impacto y retracción al secado. Sobre las probetas ensayadas a impacto se realizó un estudio microestructural por SEM/EDX. Los resultados obtenidos han demostrado que: a) Las fibras acrílicas y de polipropileno son estables en medios fuertemente básicos, aunque las primeras experimentan procesos de hidrólisis/hidratación que se manifiesta con alteración de su textura superficial, b) Con bajos contenidos en fibra (0,2% en volumen), la tenacidad y el índice de tenacidad de estos morteros no se ve afectado. Con contenidos superiores (1%) se produce un incremento en los correspondientes valores. Este incremento es mayor en los morteros de escoria activada alcalinamente, c) Para las tres matrices estudiadas, las fibras de polipropileno incrementan la resistencia al impacto en mayor medida que las fibras acrílicas. El efecto de refuerzo es más significativo en la matriz que contiene escorias y cuando el contenido de fibra es del ¡% en volumen, d) La retracción al secado de estos morteros se modifica dependiendo del tipo de matriz y fibra. En los morteros de escoria activada, las fibras no reducen la retracción. En los morteros de ceniza activada reforzados con las fibras acrílicas, la retracción es menor que cuando contienen fibras de polipropileno o carecen de ellas. Finalmente, en los morteros de ceniza/escoria activada, las dos fibras reducen la retracción al secado.Peer reviewe

Strategi Pembelajaran Problem Solving, Gaya Belajar Kolb, Dan Hasil Belajar Mekanika Rekayasa

: Problem-solving Teaching Strategy, Kolb Learning Styles, and Learning Achievement. This quasi experimental study was intended to investigate the differences in learning achievement in Mechanical Engineering II Course between students taught using problem - solving strategy, taking their learning styles into considerations. The independent variable of problem-solving strategy includes open-ended (Psoe) and closed- ended (Psce), whereas the moderating variable of learning style consists of diverging, converging, and assimilating styles. The subjects were randomly selected from Mechanical Engineering II classes, resulting in 68 students joining Psoe strategy and 64 joining PSce strategy. The data obtained from problem - solving test method revealed that students with Psoe strategy outperformed those with Psce moderated by the learning styles of diverging, assimilating, converging and accommodating

Hormigones reforzados con fibras acrílicas

This article is based on works, carried out at the IETcc, aimed to evaluate the behaviour of concretes reinforced with acrylic polyacrylonitrile fibres, and to study the influence they have on concrete physical and mechanical properties.El presente artículo está basado en trabajos realizados en el Instituto de Ciencias de la Construcción Eduardo Torroja, teniendo por objetivo evaluar el comportamiento de los hormigones reforzados con fibras acrílicas de poliacrilonitrilo, estudiando la influencia que tiene sobre sus propiedades físicas y mecánicas

Prototype Lemari Pengering Pakaian Otomatis

Pemanasan Global yang menyebabkan Perubahan cuaca yang tidak menentu. Perubahan cuaca yang tidak menetukan ini yang menyebabkan kerepotan jika hujan turun menerus, sehingga pakaian yang sudah di cuci tidak bisa kering. Karena hal inilah yang memunculkan ide untuk menciptakan alat pengering pakaian otomatis. Mikrokontroler ATMega328 digunakan sebagai pengontrol dalam proses pengeringan secara elektronik. Hal ini lebih mudah untuk mengeringkan pakaian tanpa harus menunggu cuaca cerah. Sensor suhu dan kelembaban DHT-11 digunakan sebagai pendeteksi suhu didalam ruangan pengeringan pakaian. Lampu bholam yang digunakan sebagai komponen pengering dan kipas fan digunakan untuk menyebarkan panas dalam ruangan pengeringan pakaian. Sedangkan Arduino Uno sebagai software untuk mengontrol Mikrokontroler ATMega328. Hasil penelitian menunjukkan bahwa alat mampu mengeringkan 1pakaian dengan jumlah waktu 17 menit dan panas matahari memerlukan waktu 1 jam 5 menit. Jadi jarak waktu pengeringan otomatis dengan panas matahari sekitar 1 jam. Dengan demikian alat pengering pakaian ini dapat di gunakan sebagai pengganti sinar matahari jika cuaca hujan

Estimating the incidence of equine viral arteritis and the sensitivity of its surveillance in the French breeding stock

Equine viral arteritis (EVA) may have serious economic impact on the equine industry. For this reason, it is monitored in many countries, especially in breeding stock, to avoid its spread during breeding activities. In France, surveillance is mainly based on serological tests, since mares are not vaccinated, but difficulties in interpreting certain series of results may impair the estimation of the number of outbreaks. In this study, we propose specific rules for identifying seroconversion in order to estimate the number of outbreaks that were detected by the breeding stock surveillance component (BSSC) in France between 2006 and 2013. A consensus among multidisciplinary experts was reached to consider seroconversion as a change in antibody titer from negative to at least 32, or as an eight-fold or greater increase in antibody level. Using these rules, 239 cases and 177 outbreaks were identified. Subsequently, we calculated the BSSC's sensitivity as the ratio of the number of detected outbreaks to the total number of outbreaks that occurred in breeding stock (including unreported outbreaks) estimated using a capture-recapture model. The total number of outbreaks was estimated at 215 (95% credible interval 195-249) and the surveillance sensitivity at 82% (CrI95% 71-91). Our results confirm EVA circulation in French breeding stock, show that neutralizing antibodies can persist up to eight years in naturally infected mares and suggest that certain mares have been reinfected. This study shows that the sensitivity of the BSSC is relatively high and supports its relevance to prevent the disease spreading through mating

Predicting the ecological impacts of an alien invader: experimental approaches reveal the trophic consequences of competition

1. Ecological theory on the trophic impacts of invasive fauna on native competitors is equivocal. While increased inter-specific competition can result in coexisting species having constricted and diverged trophic niches, the competing species might instead increase their niche sizes to maintain energy intakes. Empirical experiments can test invasion theory on competitive interactions and niche sizes across different spatial scales and complexity. 2. The consequences of increased inter-specific competition from a model alien fish Leuciscus idus were tested on two taxonomically and trophically similar native fishes, Squalius cephalus and Barbus barbus. Competitive interactions were tested in tank aquaria using comparative functional responses (CFRs) and cohabitation trials. The consequences of these competitive interactions for the trophic niche sizes and positions of the fishes were tested in pond mesocosms. 3. CFRs revealed that compared to B. barbus, L. idus had significantly higher attack and consumption rates; cohabitation trials revealed B. barbus growth rates were depressed in sympatry with L. idus. For L. idus and S. cephalus, differences in their functional response parameters and growth rates were not significant. 4. Pond mesocosms used stable isotope metrics to quantify shifts in the trophic niche sizes of the fishes between allopatry and sympatry using a substitutive experimental design. Isotopic niches were smaller and more divergent in sympatric paired species than predicted by their allopatric treatments, suggesting trophic impacts from inter-specific competition. However, an all-species sympatric treatment revealed similar niche sizes with allopatry. This maintenance of niche sizes in the presence of all species potentially resulted from the buffering of direct competitive effects of the species-pairs by indirect effects. 5. Experimental predictions from tank aquaria assisted the interpretation of the constricted and diverged trophic niches detected in the paired-species sympatric treatments of the pond mesocosms. However, the all-species sympatric treatment of this experiment revealed greater complexity in the outcomes of the competitive interactions within and between the species. These results have important implications for understanding how alien species integrate into food webs and influence the trophic relationships between native species

Unraveling the Interplay between Quantum Transport and Geometrical Conformations in Monocyclic Hydrocarbons Molecular Junctions

In the field of molecular electronics, particularly in quantum transport studies, the orientation of molecules plays a crucial role. This orientation, with respect to the electrodes, can be defined through the cavity of ring-shaped monocyclic hydrocarbon molecules. In this manuscript, we unveil the geometrical conformation of these molecules when they are trapped between two atomically sharp electrodes through a combination of dynamic simulations, electronic transport calculations based on density functional theory, and break junction experiments under room conditions. Moreover, we present a novel criterion for determining the molecular orientation of benzene, toluene, (aromatic) and cyclohexane (aliphatic) solvents. Our findings for the identification of the molecular orientations on gold metal nanocontacts and their associated transport properties, can improve the understanding of molecular electronics using more complex cyclic hydrocarbons.Comment: 8 pages,9 figures, suplemental material include

Problems on Commercialization of Genetically Modified Crops in Malaysia

Modern biotechnology is a potential technology to be developed in Malaysia. Advancement in molecular genetics methods such as the recombinant DNA techniques in genetic engineering improves ways to make use of living organisms to benefit human. From the perspectives of agro biotechnology, the methods which enable the introduction of genetic material to be integrated into plant genome called Plant Genetic Modified Technology (PGMT). Since 1980s Malaysia enthusiastically worked on the development of Genetically Modified (GM) Crops. However, with certain barriers and hindrances, the successful development seems unattainable. This study was conducted to explore the six critical factors and issues which affect the successful commercialization of GM Crops in Malaysia using face to face and telephone interview which involved ten respondents from eight universities and research institutions in Malaysia. The data was analyzed using NVIVO computer software. The results from findings, recommendations and implications to practitioners presente