Techniques for sustainable building materials production: recycling in concrete industry

The excellent mechanical and durability properties, with its large availability and affordable costs, make concrete the most used engineered material, with an estimated worldwide consumption about 6 billion tons per year. The prices of this wide diffusion lie into the relevant environmental emissions associated to concrete industry: concrete production is in fact one of the main responsible of carbon emission in atmosphere, mainly due to cement manufacturing and natural aggregates extraction. Together with the energy requirements, water consumption and generation of construction and demolition waste, these factors contribute to the general appearance that concrete is not particularly compatible with the demands of sustainable development. Several operations can be applied to limit concrete impacts: the replacement of Portland cement with supplementary cementing materials (SCMs) and the use of recycled aggregates in place of natural resources are solutions that may achieve the aim of reducing concrete emissions during all its life cycle. Between the various recycled materials which can be suitable in concrete applications, promising results were obtained when limited quantities of recycled aggregates from construction and demolition wastes (C&DWs) and from electric arc furnace (EAF) slag are used, generally not affecting mechanical properties and environmental compatibility. Nevertheless, in the most of cases a lack of standardized rules hinder their use at market level, in particular when recycled aggregates or mineral additions come from metallurgical industry. In this thesis the use of two types of recycled aggregates for structural concrete production is explored: EAF slag as recycled aggregates and recycled aggregates from C&DW. In addition, the use of supplementary cementing materials is analyzed, paying particular attention on the suitability of the application of co-combustion fly ash in structural concrete. Two extensive experimental campaigns were carried out to analyze the main mechanical and durability-related properties of recycled concrete with EAF slag. Several mixes with increasing substitution ratios were produced, using both the coarse and the fine aggregates. A specific chemical and micro-structural in-depth examination was carried out in order to evaluate the actual stability of the material, the influence of the substitution ratio on hardened concrete properties and to study the aggregates-matrix bond when detrimental cycles were applied to concrete specimens. Once determined the suitability of some of the substitution ratios used, for the first time real-scale reinforced concrete beams with EAF slag were realized and tested for bending and shear failure, and their structural behavior is analyzed and discussed. The second part of the thesis deals with the use of recycled aggregates coming from C&DWs, to assess their influence on the rheological behavior of fresh concrete. An experimental campaign was conducted, and since slump value is often operator-sensitive, a more quantitative estimate was derived in terms of fundamental physical quantities, such as plastic viscosity and yield stress, by means of viscometer measures. The variables analyzed were the aggregates substitution ratio and proportioning method, the super-plasticizer content and the water/cement ratio. Lastly, an experimental campaign was performed to compare the effects of two different (SCMs) on mechanical and durability-related properties of structural concrete. Three mixes were produced, where coal and co-combustion fly ashes were used as partial substitute of cement (20% in volume) and compared with a reference concrete. An environmental impacts’ assessment was also performed, through a Life Cycle Analysis (LCA) framework specifically developed for concrete emissions evaluation, using a cradle-to-gate approach. Assessment is based on Italian LCI data, collected directly from local EAF slag treatment plant, a natural aggregate extractive plant and a C&DW processing plan

Aeronautical Engineering: a Continuing Bibliography with Indexes (Supplement 243)

This bibliography lists 423 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

World Multidisciplinary Civil Engineering- Architecture- Urban Planning symposium

We would like to express our sincere gratitude to all 900+ submissions by 600+ participants of WMCAUS 2018 from 60+ different countries all over the world for their interests and contributions in WMCAUS 2018. We wish you enjoy the World Multidisciplinary Civil Engineering-Architecture-Urban Planning Symposium – WMCAUS 2018 and have a pleasant stay in the city of romance Prague. We hope to see you again during next event WMCAUS 2019 which will be held in Prague (Czech Republic) approximately in the similar period

Simulation and Design of Mixing Mechanism in Fertilizer Automated Proportioning Equipment Based on Pro/E and CFD

International audiencePrecision agriculture is the developing trend of modern agriculture, and the rational utilization of fertilizer is one of the key technologies in the precision agriculture, which needs to fertilize variably according to the crop needs and soil fertility conditions. Thus a fertilizer automated proportioning equipment is developed to Proportion the three fertilizers: Nitrogen fertilizer, Phosphorus fertilizer and Kalium fertilizer. The fertilizer will take greater effect after mixing sufficiently, so this paper mainly researched the mixing mechanism. The simulation and analysis of the velocity field and flow field of the fertilizer for the two paddles worked, the spiral-type paddle and multiple- fan-type paddle, are conducted respectively using Pro/E (Pro/Engineer) and CFD(Computational Fluid Dynamics) fluid dynamics analysis software. During simulation, the paddle models are meshed using the Gambit software. Then the multiple- fan-type paddle is determined to be the more suitable one through the FLUENT software

Association of Architecture Schools in Australasia

"Techniques and Technologies: Transfer and Transformation", proceedings of the 2007 AASA Conference held September 27-29, 2007, at the School of Architecture, UTS