Infrastructure Research & Development (Qatar)

In this study, the influence of graphene oxide nanoparticles on the bond-slip behavior of fiber and fly ash based geopolymer paste was examined. Geopolymer paste incorporating graphene oxide nanoparticles solution was cast in half briquetted specimens and embedded with a fiber. Three types of fibers were used: steel, polypropylene, and basalt. The pullout test was performed at two distinct speeds: 1 mm/second and 3 mm/second. Results showed that the addition of graphene oxide increased the compressive strength of geopolymer by about 7%. The bond-slip responses of fibers embedded in geopolymer mixed with graphene oxide exhibited higher peak stress and toughness as compared to those embedded in normal geopolymer. Each fiber type also showed different mode of failure. Both steel and polypropylene fibers showed full bond-slip responses due to their high ductility. Basalt fiber, on the other hand, because of its brittleness, failed by fiber fracture mode which showed no-slip in pull out responses. Both bond strength and toughness were found to be rate sensitive. The sensitivity was higher in graphene oxide/geopolymer than in conventional geopolymer.

Abstract Beneficiaries prefer renewable energy-based systems over grid-connected electricity. The cost of energy is viewed as the most influential factor while choosing renewable energy systems. Beneficiaries chose to stay linked with renewa­ble energy systems even when they received grid-connected electricity at a lower tariff.Net-metering and feed-in tariff mechanisms, as well as tax cuts and subsidies for renewable energy projects, could be the catalyst for fostering greater uptake of renewables in the electricity generation mix.

ABSTRACT A water footprint analysis was conducted of construction aggregates and aggregate-derived products, given the pressure on this scarce resource in Qatar and the region and the high priority placed on sustainable water management. The total volume of water used for the production of aggregate materials, imported and local, and aggregate-derived construction products of asphalt and concrete was determined on the basis of a ‘cradle to gate’. The overall water footprints associated with the aggregate products ranged from 2.8 l/t for recycled aggregates to 469 l/t for Portland cement C40 concrete. The results highlighted the significance of the contribution of binders to the overall mixtures, in particular, the contribution of Portland cement which far outweighed the contribution of aggregates. The use of small fractions of polymers in asphalt also proved to be significant. Both concrete and polymer-modified asphalt had water footprints at least an order of magnitude higher than aggregate products alone. Substituting Portland cement with cement replacement materials, e.g. GGBS in this study, lowered the water footprint of concrete products. Further reductions could be achieved with the use of recycled aggregate and substituting freshwater demand with TSE.

The State of Qatar went through a massive road construction program in the last decade as part of the ongoing development of its infrastructure and road transport network. Construction of roads in Qatar generally utilizes imported materials such as aggregate and binders as a result of the scarcity of local construction materials. Characteristics of asphalt mixtures are studied in this research program in order to evaluate mixtures properties in terms of aggregate packing, binder content, voids, mixture density, maximum density and Marshall Stability. Actual mixtures used in the Public Works Authority road projects were analyzed in the research program. Mixtures were prepared following the Qatar Construction Specifications Combined aggregate gradations for different asphalt mixtures were compared with maximum density envelopes for different maximum aggregate sizes. Moreover, regression analysis was used to evaluate the strength of correlations established between different asphalt mixtures properties. The analysis of these mixtures is outlined in terms of general characteristics and consequently, recommendations are given to improve asphalt mixtures performance.