High-strength concrete incorporating copper slag and ground pumice

University of Technology Sydney. Faculty of Engineering and Information Technology.Nowadays, concrete is the most widely used construction material which mainly consists of Portland cement, aggregate and water. For more than 200 years, concrete has been known as a durable and high strength construction material while its formability during its fresh stage results in building different shapes which are otherwise not possible. Due to widespread construction of high-rise buildings, bridges and other concrete structures, there is a growing demand from clients as well as technical requirements for using high-strength concretes in certain applications such as towers. However, common belief is that more Portland cement should be used for obtaining a higher strength grade. In other words, producing high-strength concrete is synonymous with higher consumption of Portland cement. But, cement production is a high energy-consuming and polluting process to the extent that Portland cement production, on its own, contributes to over 7% of worldwide greenhouse gases (GHG) which is equal to 1.6 billion tonnes of GHGs. On average, production of each tonne of Portland cement results in releasing one tonne of CO₂. Current average consumption of concrete is about one tonne per year per every living human being. Because of large consumption of concrete and Portland cement as well as its energy-consuming and polluting production process, even small reductions in greenhouse gas emissions per tonne of manufactured concrete can make a significant and positive global impact. Recent research shows that Portland cement and coarse aggregates have the highest environmental impacts and greenhouse gas emissions. Therefore, any attempt to make concrete more sustainable should firstly focus on these two materials. On the other hand, using traditional materials such as natural limestone aggregate for producing concrete causes many environmental problems and such procedures are critically under scrutiny in terms of sustainability because it is not possible to renew these natural sources. Therefore, new procedures must be developed to use alternative raw materials for producing concrete. Pumice is a volcanic rock which is made of highly vesicular rough textured volcanic glass. According to US Geological Survey Report, global production of pumice and pumicite was approximately 18 and 17 million tonnes in 2011 and 2012, respectively. Traditionally, pumice as aggregate has been used for producing light weight building blocks, concrete and assorted building products in construction industry. However, technical performance and properties of concretes with pumice aggregate conveys important concerns because of high water absorption of pumice aggregate. On the other hand, main chemical ingredient of pumice is SiO₂ and many researchers have reported that pozzolanic characteristics for pumice powder and its positive effects on mechanical and long-term properties of concrete. Therefore, it can be a good alternative cementitious material which can be used instead of Portland cement. Copper slag is a by-product obtained during the matte smelting and refining of copper. Production of one tonne of copper produces around 2.2-3 tonne of copper slag. In the United States, the amount of copper slag manufactured is approximately four million tonnes, and in Japan is around two million tonnes per year. Although some researchers have attempted to use copper slag powder as a cement additive, a significant part of deposited copper slag is air-cooled slag which results in crystallised structure instead of required amorphous structure for a cement additive. Furthermore, many researchers have reported promising results by using copper slag as coarse aggregates in concrete. This research aims to develop a novel type of green high-strength concrete by using copper slag coarse aggregate and pumice powder with less environmental impacts and carbon footprint with at least similar performance to common high-strength concrete. To achieve this purpose, a comprehensive assessment of results of an extensive experimental program on fresh and hardened concrete specimens including slump, unit weight, air content, compressive and splitting tensile strength measurements was undertaken. 16 different mixture proportions based on different levels of cement replacement with pumice and using copper slag instead of limestone coarse aggregate at two water to binder ratios of 0.3 and 0.4 were investigated. In addition, silica fume was used at level of 10% of cement weight in some mixtures. Compressive strength of concrete specimens were measured at different ages of 7, 28, 56 and 91 days while splitting tensile strength was measured at 7, 28 and 91 days to evaluate effects of pumice, copper slag and their combinations. In general, it can be concluded that the presence of copper slag can increase compressive strength of concrete at different ages. This can be attributed to higher level of strength properties displayed by copper slag aggregate. In addition, the surface texture of coarse aggregate is partly responsible for the bond between the cement paste and aggregate because of the mechanical interlocking between cement paste and copper slag. At age of 91 days, all of concrete mixtures, except those containing finely ground pumice as 20% of Portland cement replacement, showed approximately similar or even better performance in comparison with control mixtures. In general, it can be concluded that using copper slag coarse aggregate increased the splitting tensile strength of concrete by around 12% in comparison with control mixtures with limestone coarse aggregate. In addition, adding finely ground pumice resulted in rapid reduction of the splitting tensile strength at all ages. However, satisfying results were obtained by combined use of pumice powder and copper slag coarse aggregate. With regard to numerous test results of fresh and hardened high-strength concrete with and without copper slag coarse aggregate and finely ground pumice, it can be recommended that the most efficient and optimized value of finely ground pumice when copper slag coarse aggregate is used in concrete is 10% at water to binder ratio of 0.4 and 20% at water to binder ratio of 0.3 with the presence of 10% silica fume in concrete mixture. The 28-day compressive and splitting tensile strength were similar to control normal concrete with limestone coarse aggregate while at later ages they displayed superior performance in comparison with the control normal mixture in terms of compressive and splitting tensile strength. The recommended values of pumice and copper slag showed promising and excellent results at the age of 56 days which is the common age of measuring concrete properties including high level of supplementary cementitious materials. In this study, 30% of Portland cement was successfully replaced by silica fume and finely ground pumice while copper slag coarse aggregate as an industrial waste material was simultaneously used instead of whole of natural limestone coarse aggregate for producing sustainable high-strength concrete. With regard to the Green Building Council of Australia’s Green Star Mat-4, this novel type of high-strength concrete can achieve concrete credits as green concrete

Vision-Based Fuzzy 2D Motion Control of a Model Helicopter

©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or distribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.Presented at NAFIPS 2006 : 2006 Annual Meeting of the North American Fuzzy Information Processing Society : Montréal, Canada, 3-6 June 2006.DOI: 10.1109/NAFIPS.2006.365497In this paper the 2D motion of a model helicopter is studied. The position control of a 2D model helicopter falls into complex nonlinear problems domain which makes it rather hard. In this paper a fuzzy controller is proposed to stabilize the helicopter on a designated target. The 3D model of the helicopter is simplified to derive a 2D model and all the states are assumed to be measurable. Based on the model, it was possible to decouple the position and orientation control of the helicopter. However the two parts are related through a fuzzy rule base. To verify the proposed method a simulation program is written in C++ which takes advantages of OpenGL to enable having 3D features. The response graphs are then presented       

Determining the Moisture Content of Pre-Wetted Lightweight Aggregate: Assessing the Variability of the Paper Towel and Centrifuge Methods

Internally cured (IC) concrete is frequently produced in North America using pre-wetted lightweight aggregate (LWA). One important aspect associated with the production of quality IC concrete is the accurate determination of the moisture content, including absorbed moisture and surface moisture of the LWA. Knowledge of the moisture content enables aggregate moisture corrections to be made for the concrete mixture, thereby enabling an accurate water-to-cement ratio to be maintained. Two methods for determining the moisture content of LWA include the specified ASTM C1761-13b “paper towel method” and a method that uses a centrifuge (Miller, Barrett, Zander, & Weiss, 2014). There are limited data available on the variability associated with either of these approaches when the test is performed by multiple users. In this study, the absorption of four commercially available LWAs was tested by a single operator in a single laboratory using the centrifuge method. In addition, the absorption of three commercially available LWAs was tested by 25 users performing both experimental methods. This article provides an estimation of precision associated with both a single operator and multiple operators performing both the paper towel method and the centrifuge method to find the absorption of pre-wetted lightweight fine aggregate

Superabsorbent Polymers for Internally Cured Concrete

Two commercial superabsorbent polymer (SAP) formulations were used to internally cure cement pastes, mortars, and concretes with a range of water-to-cement ratios (w/c 0.35–0.52). The following properties were determined as a function of cement chemistry and type, use of chemical admixtures, use of slag, and batching parameters: SAP absorption capacity, fresh mixture workability and consistency, degree of hydration, volumetric stability, cracking tendency, compressive and flexural strength, and pumpability. SAP internal curing agents resulted in cementitious mixtures with improved hydration, accelerated strength gain, greater volumetric stability, and improved cracking resistance while maintaining sufficient workability to be pumped and placed without sacrificing compressive or flexural strength. When using SAP, batching adjustments prioritized the use of water reducing admixture instead of extra water to tune workability. While the benefits of SAP internal curing agents for low w/c mixtures were expected, SAP-containing mixtures with w/c ≥ 0.42 displayed accelerated strength development and decreased cracking tendency

Imaging the Anisotropic Nonlinear Meissner Effect in Nodal YBa ₂Cu₃O\u3csub\u3e7-δ\u3c/sub\u3e Thin-Film Superconductors

We have directly imaged the anisotropic nonlinear Meissner effect in an unconventional superconductor through the nonlinear electrodynamic response of both (bulk) gap nodes and (surface) Andreev bound states. A superconducting thin film is patterned into a compact self-resonant spiral structure, excited near resonance in the radio-frequency range, and scanned with a focused laser beam perturbation. At low temperatures, direction-dependent nonlinearities in the reactive and resistive properties of the resonator create photoresponse that maps out the directions of nodes, or of bound states associated with these nodes, on the Fermi surface of the superconductor. The method is demonstrated on the nodal superconductor YBa2Cu3O7-δ and the results are consistent with theoretical predictions for the bulk and surface contributions

Machine learning to predict major bleeding during anticoagulation for venous thromboembolism: possibilities and limitations

Predictive tools for major bleeding (MB) using machine learning (ML) might be advantageous over traditional methods. We used data from the Registro Informatizado de Enfermedad TromboEmbólica (RIETE) to develop ML algorithms to identify patients with venous thromboembolism (VTE) at increased risk of MB during the first 3 months of anticoagulation. A total of 55 baseline variables were used as predictors. New data prospectively collected from the RIETE were used for further validation. The RIETE and VTE-BLEED scores were used for comparisons. External validation was performed with the COMMAND-VTE database. Learning was carried out with data from 49 587 patients, of whom 873 (1.8%) had MB. The best performing ML method was XGBoost. In the prospective validation cohort the sensitivity, specificity, positive predictive value and F1 score were: 33.2%, 93%, 10%, and 15.4% respectively. F1 value for the RIETE and VTE-BLEED scores were 8.6% and 6.4% respectively. In the external validation cohort the metrics were 10.3%, 87.6%, 3.5% and 5.2% respectively. In that cohort, the F1 value for the RIETE score was 17.3% and for the VTE-BLEED score 9.75%. The performance of the XGBoost algorithm was better than that from the RIETE and VTE-BLEED scores only in the prospective validation cohort, but not in the external validation cohort

Rheological, physicochemical, and microstructural properties of asphalt binder modified by fumed silica nanoparticles

Warm mix asphalt (WMA) is gaining increased attention in the asphalt paving industry as an eco-friendly and sustainable technology. WMA technologies are favorable in producing asphalt mixtures at temperatures 20–60 °C lower in comparison to conventional hot mix asphalt. This saves non-renewable fossil fuels, reduces energy consumption, and minimizes vapors and greenhouse gas emissions in the production, placement and conservation processes of asphalt mixtures. At the same time, this temperature reduction must not reduce the performance of asphalt pavements in-field. Low aging resistance, high moisture susceptibility, and low durability are generally seen as substantial drawbacks of WMA, which can lead to inferior pavement performance, and increased maintenance costs. This is partly due to the fact that low production temperature may increase the amount of water molecules trapped in the asphalt mixture. As a potential remedy, here we use fumed silica nanoparticles (FSN) have shown excellent potential in enhancing moisture and aging susceptibility of asphalt binders. In this study, asphalt binder modification by means of FSN was investigated, considering the effects of short-term and long-term aging on the rheological, thermal, and microstructural binder properties. This research paves the way for optimizing WMA by nanoparticles to present enhanced green asphalt technology