Influence of ground tire rubber on stone mastic asphalt mixtures and preliminary sustainability studies on rubber-modified asphalt pavements

Over the last few decades, the use of Stone Mastic Asphalt (SMA) has been adopted by several states in the U.S. as a specialty mix for high-traffic volume purposes. Extensive research on these mixes has revealed its unique characteristics, along with significant performance benefits, such as enhanced cracking and rut resistance, that are essential to mitigate critical pavement distresses. However, certain economic issues pertaining to SMA mixtures resulting from the need for high-quality aggregates and elevated binder content make it less favored by state transportation and highway agencies. To offset these costs, numerous studies have been conducted that encourage the incorporation of recycled material, such as recycled asphalt pavement (RAP), recycled asphalt shingles (RAS) and recycled rubber into SMAs. Of these, the rubber modified SMA mixes have exhibited superior performance, and economic and sustainability benefits. The incorporation of recycled scrap tires, as ground tire rubber (GTR), into the asphalt mixtures helps reduce the accumulation of end-of-life vehicle tires in landfills, which is a growing environmental concern. At present, the state of Missouri does not allow the use of recycled material in its SMA mixes. This thesis was proposed to assess GTR as viable means modification suitable for SMA pavements, with respect to the extreme climatic conditions of Missouri. To achieve this, two GTR-modified SMA mixes with 10 percent modification were compared against an unmodified SMA mix. A suite of performance tests was conducted to address prime pavement distresses, namely, Disk-Shaped Compact Tension test (DC(T)) to assess low-temperature cracking, Hamburg Wheel Tracking test (HWTT) for high-temperature deformations, and indirect tensile asphalt cracking test (IDEAL-CT) to determine intermediate-temperature fracture resistance. Further, a performance space diagram was also used to evaluate the overall performance or balance of these mixes. All experimental results concluded that the GTR-modified mixes performed better than the unmodified mix. Nevertheless, all three SMA mixes were within satisfactory performance threshold. The performance space plot clearly indicated that the GTR-modified SMA mixes were ideal for high-traffic volume pavements, in terms of thermal cracking and rutting distresses. To understand the potential of recycled rubber modification in a holistic manner, apart from performance analyses, sustainability studies on rubber-modified asphalt (RMA) pavements were conducted on a preliminary level, as a part of this thesis work. Life Cycle Assessment (LCA) is an environmental impact evaluation tool that has played a significant role in the recent years, for promoting advances in the use of recycled material in asphalt pavements to reduce the overall environmental burden and energy consumption. A widespread and comprehensive literature review was performed with an intention to obtain significant findings and learn the varied approaches used in these pavement LCAs. The defining LCA aspects such as the goal, functional unit, system boundaries and impact categories were analyzed and compared. This study established the following key knowledge gaps and recommendations: the inclusion of the maintenance phase of pavements and end-of-life phase of scrap tires in the system boundaries are critical for RMA pavements, there is a need to assign standardized eco-credit for RMA, using up-todate performance data including functional characteristics, and quantifying additional impact categories can significantly improve sustainability analysis outcomes for rubbermodified pavements. Addressing such issues could contribute to apprehend the full sustainability potential of rubber as a recycled material for pavement application

Hormigones de alta performance con fibras de acero

En este trabajo se presentan algunos resultados obtenidos en LEMIT correspondientes al proyecto de cooperación entre UNLP-LEMIT y UPC (Cataluña, España) sobre el empleo de fibras de acero en hormigones con elevados niveles de resistencia. Se evalúa el comportamiento de hormigones simples y reforzados bajo solicitaciones de compresión y flexión, incluyendo en este último caso diferentes tipos de probetas, configuraciones de ensayo, y distintos tipos y contenidos de fibras. Se discuten los cálculos de tenacidad y resistencia residual conforme los lineamientos de ASTM C 1018. Los resultados muestran cómo es posible caracterizar a los hormigones reforzados empleando probetas con distinta geometría y diferenciar el tipo o contenido de fibras utilizados en cada caso. Asimismo se observa el efecto del tipo de acero de las fibras y del contenido de refuerzo en hormigones con resistencias del orden de 70 MPa.This work presents several results obtained at LEMIT corresponding to the cooperation project between UNLP-LEMIT and UPC (Catalonia, Spain) about the use of steel fibers in concretes with high strength levels. The behavior of plain and fiber reinforced concretes under compressive and flexural loads, including in this last case different types of specimens, test setups, and different contents and fiber types is evaluated. Toughness calculation and residual strength in accordance to ASTM 1018 is discussed. Results show how it is possible to characterize fiber reinforced concretes employing specimens with different geometry, and distinguish the type or content used in each case. In the same way, the effect of the steel type of the fibers and the content of fiber reinforcing in concretes with strengths up to 70 MPa is observed

Material nonlinear analysis of steel fibre reinforced concrete beams failing in shear

Experimental research has pointed out that fibre reinforcement gives valuable contribution for the shear strength of concrete beams. To obtain data to check the validity of the formulation proposed by RILEM TC 162-TDF for the evaluation of the fibres contribution for the concrete shear strength, sets of concrete beams were tested experimentally. To simulate the behaviour of this kind of structures, a computational code was developed, based on the finite element techniques. An accurate simulation of the behaviour of structures failing in a brittle mode, such is the case of the beams failing in shear, is a true challenge in the computational mechanics domain. To reproduce with enough accuracy the fracturing process of this type of elements, a multifixed crack model is implemented. The ability of the post-cracking stress-strain diagram proposed by RILEM TC 162-TDF to simulate the crack propagation is checked. A strain softening trilinear diagram is also derived from inverse analysis using the force-deflection relationship obtained in RILEM three-point notched beam tests. Its capability to model the fracture mode I is also assessed. The numerical strategy developed is described in the present work and the appropriateness of the model is evaluated simulating some beams tested experimentally.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BSAB/291/2002-POCTI. Fundo Social Europeu (FSE) -SFRH/BSAB/291/2002-POCTI

Reología de hormigones autocompactables

El diseño y aplicación del Hormigón Autocompactable (HAC) constituye uno de los temas de mayor impacto e interés en el mundo en el campo de la tecnología del hormigón. En términos reológicos un HAC se caracteriza por poseer una tensión umbral de cizallamiento muy baja y una viscosidad plástica capaz de garantizar el transporte, llenado y consolidación del hormigón sin segregación. La caracterización reológica en estado fresco brinda información para diseñar diferentes clases de HAC y permite valorar la influencia de los materiales componentes así como el efecto de diversas variables externas. Este trabajo analiza la reología del HAC, en primer lugar se presentan los conceptos reológicos y las variables que modifican la respuesta del hormigón fresco, destacando las características particulares del HAC; en segundo término se muestran resultados correspondientes a un programa de investigación en el que se empleó un BML Viscometer 3 (CONTEC) con el fin de ponderar la influencia de factores que afectan la producción del HAC como la temperatura del hormigón, el tiempo transcurrido luego de finalizar mezclado y las condiciones de exposición luego de la elaboración; finalmente se analiza la vinculación entre los parámetros reológicos y las medidas de los ensayos de tipo ingenieril más frecuentemente utilizados (escurrimiento y embudo en V).The mix design, characterisation, and application of Self-Compacting Concrete (SCC) are undoubtedly key topics of major impact and interest in the field of concrete technology worldwide. In rheological terms, SCC is characterised by a very low yield stress and an adequate plastic viscosity to assure stability during transport, casting and later hardening of the material. The rheological characterisation in the fresh state allows obtaining information for the design of different classes of SCC, including the component materials and the effect of external variables. This work analyses the rheology of SCC; rheological concepts and the variables affecting the response of the fresh concrete are presented firstly, highlighting the specific characteristics of SCC, the second part presents the results of a research program in which a CONTEC 3 viscometer was utilised with the aim of studying the influence of different factors affecting the production of SCC, such as temperature of the material, and time and the exposure conditions after fabrication. Finally, correlations between rheological parameters and the results of frequently-used engineering tests (slump-flow and V-funnel), are analysed

Comportamento da ligação de laminados de CFRP inseridos no betão sob acções cíclicas

Com o objectivo de avaliar a influência do comprimento de aderência e da história do carregamento no comportamento da ligação de laminados de fibras de carbono (CFRP) ao betão, foram efectuadas campanhas de ensaios com três comprimentos de aderência distintos e diferentes tipos de história de carga. O CFRP é inserido em ranhuras efectuadas no betão e é fixo ao betão por intermédio de um adesivo epoxy. No presente trabalho, os ensaios de arranque em flexão efectuados são descritos e os resultados obtidos são apresentados e analisados.Bettor MBT. Cimentos Molins e Grace. Fundação para a Ciência e Tecnologia (FCT) - SFRH/BD/3259/2000. Fundo Social Europeu (FSE) - SFRH/BD/3259/2000

Socio-economic and gender determinants of immunisation coverage in the federal capital territory, Nigeria

Abstracts in English and ZuluImmunisation is a cost-effective public health intervention that contributes to the attainment of the Sustainable Development Goals (SDGs). About 40% of children under the age of five years die from vaccine-preventable diseases in Nigeria. Routine immunisation has been quite low in Nigeria, where national coverage is estimated to be 33%, according to a 2016–2017 survey. This empirical research was aimed at determining the key socio-economic and gender determinants of immunisation in the Federal Capital Territory (FCT), identifying gaps and proffering solutions. Mixed methods of data collection and analysis were used. Data were gathered from several secondary sources and from 11 key informants using semi-structured interviews and 501 household and 26 health-facility surveys using questionnaires mounted on Open Data Kit. Lot quality assurance sampling and probability to population size methodology were used to size the samples and identify survey locations. Odds ratio analysis and logistic regression analysis were conducted to gauge the statistical association between the determinants and the coverage of immunisation. The main finding that was reached on the basis of the documents reviewed and the feedback received from the key informants was that they were gender blind at worst and gender neural at best. Most of the current strategies give little attention to socio-economic and gender barriers. Over 40 immunisation variables were identified. The analysis, particularly using the 2x2 odds ratio, yielded mixed results. The majority of the variables exhibited a close statistical association as far as immunisation indices were concerned. These variables included urban residency, married couples, literacy, birth at a health facility, antenatal care experience, vaccination card possession, immunisation knowledge, child health information, non-farming earnings, socio-economic status and tolerance of spouse beating. On the other hand, variables that were found to have no statistical significance included sex, marital status, marriage type, age, religion, tetanus toxoid (TT) vaccination and adequacy of income. Immunisation and gender are intertwined, particularly because of mothers’ biological and social attachment to their children. At the same time, conducting vaccination avails the opportunity to access almost all households. Moreover, it is important to recognise that socio-economic and gender determinants are not totally in control of one ministry. Single agenda interventions will not produce the desired result. A paradigm shift and the concerted effort of various sectors and partners are required. Therefore, the Nigerian government should galvanise the relevant stakeholders to bring gender and socio-economic variables into the mainstream throughout the immunisation ecosystem and to implement integrated development initiatives by prioritising vulnerable communities.Ugonyo yindlela engcono yokungenela kwezempilo yabantu engathela esivivaneni ekufinyeleleni izinhloso zentuthuko eqhubekela phambili ezaziwa ngelokuthi yi- Sustainable Development Goals (SDGs). Cishe izingane ezifinyelela ku 40% ezingaphansi kweminyaka emihlanu zibulawa yizifo ezivimbelekayo ngomgcabo emitholampilo eNigeria. Ukugonya njalo kusezingeni eliphansi eNigeria, laphokhona ukwengamela kuzwelonke kulinganiselwa ku 33%, ngokuya kocwaningo olwenziwe phakathi kuka 2016-2017. Ucwaningo lokuthola ubufakazi lwalunenhloso yokubona imithelela yezesimo sabantu nomnotho (socio-economic) kanye nobulili ngokugonya kwi-Federal Capital Territory (FCT) ukubona amagebe kanye nokutholakala kwezixazululo. Amamethodi axubene okuqokelela ulwazi kanye nohlaziyo kwasetshenziswa. Ulwazi lwaqokelelwa ngokufunda imithombo yemibhalo (secondary sources) kanye nakubantu ababalulekile abanolwazi (key informants) abangu 11 ngokusebenzisa ama-semi-structured interview kanye nemizi engu 501 kanye namasurvey amafasilithi ezempilo angu 26 ngokusebenzisa uhla lwemibuzo yamaquestionnaire ebifakelwe kwi-Open Data Kit. Kwasetshenziswa nemethodi ye-Lot quality assurance sampling ne-probability, ngemethodoloji yobuningi babantu, ukwenza usayizi wamasampuli kanye nokubona izindawo okumele kwenziwe kuzo ama-survey. Kwenziwa nohlaziyo lwe-Odds ratio analysis kanye ne-logisic regression analysis ukubona ukuhambelana kwamastatistiki phakathi kwezinto eziwumthelela kanye nokunaba kongamelo lokwenziwa kogonyo. Okukhulu okutholakele ngokulandela amadokhumende okufundwe kuwo, kanye nezimpendulo ezivela kulabo abanolwazi ababalulekile (key informants) kube wukuthi bekungaboneleli ubulili (gender blind) kanti futhi bekungachemile ngokulandela ubulili (gender neutral) ngezinga elibi nangokungcono kakhulu. Amasu amaningi amanje awanakekeli kakhulu izihibe ezimayelana nabantu nezomnotho kanye nezobulili. Kwaphawulwa cishe izinto ezehlukene zama-variable ezingu 40 mayelana nogonyo. Uhlaziyo, ikakhulukazi ngokusebenzisa i 2x2 odds ratio, lwaveza imiphumela exubene. Ezinto zama-variable ehlukene eziningi zikhombise ukuhlobana phakathi kwamastatistiki mayelana namaindices ogonyo. Lama variable, abandakanye ukuhlala emadolobheni, abantu abashadile, ikhono lokubhala nokufunda, ukuzalwa kwezingane kumafasilithi ezempilo, izipiliyoni zonakekelo lwengane ngaphambi kokuzalwa, ukuba nekhadi lomgcabo ix wasemitholampilo, ulwazi ngogonyo, ulwazi ngempilo yengane, ukuthola imali ngemisebenzi engeyona eyokulima, isimo sabantu mayelana nezomnotho, kanye nokuqinisela ukuhlukunyezwa ngokushaywa kwabesimame. Kanti ngakolunye uhlangothi, ama-variable atholakale engenakho ukubaluleka ngokwamastatistiki, abandakanya ubulili, isimo ngokomendo, inhlobo yomendo, iminyaka yobudala, inkolo, umgcabo we-tetanus toxoid (TT), kanye nokwenela kwengeniso lemali. Ugonyo kanye nobulili kuyangenelana nokuhambelana, ikakhulukazi ngenxa yokusondelana komama kanye nezingane zabo. Ngaso leso sikhathi, ukwenziwa kogonyo kuhlinzeka ngethuba lokufinyelela cishe kuwo yonke imizi eminingi. Nangaphezu kwalokho, kubalulekile ukwamukela ukuthi isimo sabantu mayelana nezomnotho kanye nobulili kuyizinto ezinomthelela, azinalo ulawulo oluphelele kumnyango kangqongqoshe owodwa. Ungenelo ngento eyodwa ngeke kwaveza imiphumela efiswayo. Ukugudluka ngokomqondo (paradigm shift), kanye nemizamo eqhubekela phambili yemikhakha ehlukene kanye nabasebenzisani kuyadingeka. Ngakho-ke uhulumeni waseNigeria, kumele agqugquzele ababambiqhaza abafanele ukuhlanganisa nokufaka emkhakheni ofanele izinto ezimayelana nabantu nomnotho kanye nobulili, kuyo yonke inqubo yokusebenzisana kwemikhakha okumele isebenzisane nehlangene ukusebenza ngokulandela inqubo yentuthuko ehlangane ngokubonelela imiphakathi ekwizimo ezibucayiDevelopment StudiesD. Phil. (Development Studies

Have higher education institutions mainstreamed gender to contribute towards gender equality and women empowerment? : a case study of the policies and practices of two tertiary institutions in Ethiopia

Several empirical studies have concluded that gender equality is a crucial ingredient for development. Gendered higher education institutions play an important role in this respect. The research problem that this dissertation sought to address was whether Addis Ababa and Unity Universities have mainstreamed gender throughout their systems in order to contribute towards gender equality and women empowerment in Ethiopia. The research employed various data collection methodologies and processed primary and secondary data sources using qualitative and quantitative data analysis techniques. The key finding is that gender has not been integrated into the policies and practices of both Universities in any significant way. The study concludes that the Universities have an inadequate institutional framework and commitment to mainstream gender. Moreover, they lack gender analytical capacity, enforcement mechanisms for accountability, and have not forged strategic partnerships with development partners.Educational StudiesM.A. (Development Studies

Effect of aging on the fracture characteristics and brittleness of a high-strength concrete

Results of notched beam (fracture) tests on a 60 MPa silica fume concrete at the ages of 4, 10, 31 and 232 days are presented. Fracture parameters at the different ages were obtained using the size effect and cohesive crack models, which indicate that the fracture resistance (toughness and energy) decreases and the brittleness increases with the age of the concrete. This trend is attributed to the increase in the strength of the hardened cement paste and the interfaces that leads to less bond cracking and more aggregate rupture, and consequently, to more brittle failure and lower toughening.Peer Reviewe

Creep en estado fisurado en hormigones reforzados con fibras

El fib Model Code 2010 presenta avances significativos para uso de Hormigón Reforzado con Fibras ya que no sólo considera su clasificación en función de los niveles resistentes sino que brinda criterios para el diseño estructural de elementos como losas armadas, losas sin armadura convencional, uniones de columnas, paredes y muros. Sin embargo el documento no considera casos donde las cargas sostenidas den lugar a deformaciones diferidas (fluencia). Esto genera un interés particular para las macrofibras poliméricas y se ha formado un comité de la RILEM “Creep behavior on cracked sections in FRC”. Este trabajo analiza los mecanismos que provocan deformaciones diferidas en hormigones con fibras en estado fisurado y discute en qué casos tales deformaciones adquieren relevancia. Se sintetizan resultados sobre hormigones con fibras de acero y poliméricas

Estimation of the modulus of elasticity for dam concrete

The modulus of elasticity of dam concrete is difficult to determine directly from tests due to the necessity for large specimens and testing machines. In order to study the applicability of simple elastic models for predicting the modulus from standard size specimens, tests were conducted on prisms of 45×45×90 cm fabricated with dam concrete (maximum aggregate of 120 mm). The tests on standard 15×30 cm cylinders were made with the mortar and wet-screened components of this concrete. It is seen that the use of the data from these components together with estimated values of the modulus of the aggregates gives reasonable predictions of the moduli of the dam concrete. This has been verified for a range of ages, from 7 to 180 days.Peer Reviewe