Geopolymer Concrete with Fly Ash

Geopolymer concrete results from the reaction of a source material that is rich in silica and alumina with alkaline liquid. A summary of extensive studies conducted on a fly ash-based geopolymer concrete is presented. Test data are used to identify the effects of salient factors that influence the properties of the geopolymer concrete and to propose a simple method for the design of geopolymer concrete mixtures. Test data of various short-term and long-term properties of the geopolymer concrete and the results of tests conducted on large-scale reinforced geopolymer concrete members show that geopolymer concrete is well-suited to manufacture precast concrete products that can be used in infrastructure developments. The paper also includes brief details of some recent applications of geopolymer concrete

A Plate Type Edge-Lift Anchor: Influence of Reinforcing Configurations on Failure Loads

AS3850 Tilt-up Concrete Construction [1] is the current standard for design of lifting anchors and bracing in Australia. However, this standard does not provide a recommendation for calculating the capacity of edge-lifting anchors (normally placed in the edge of thin wall elements) which are commonly used in the precast industry throughout Australia. These anchors may experience a load under tension or combined tension and shear during the lifting process. The American Concrete Institute (ACI)318-08 Building Code Requirements for Structural Concrete [2], the Precast Concrete Institute (PCI) Design Handbook – Precast and Prestressed Concrete [3], and ComitéEuro-International Du Béton(CEB)Design of Fastenings in Concrete [4] include provisions for general anchorage configurations (such as multiple face lift anchors) rather than what are typically seen in edgelifting anchors. Not only are anchor configurations for edge lifting anchors different from those described in these standards, but the reinforcement around the anchor can vary significantly to those denoted in standards.This paper is an evaluation of pull out test data for edge lift anchors in thin walled elements. Using the formula in the ACI 318-08 [2], developed predominantly for footed anchors, comparisons of the predicted capacity and the test pull out capacity of the edge lift anchors is made. Data is presented on 154 tests; the variables tested include concrete compressive strength at time of testing and the provision and arrangement of reinforcement. In addition to the edge lift anchors, 90 face lift footed anchors were also tested and some of the more relevant data is presented for these tests

Breakout Capacity of Headed Anchors with Delayed Installation

The objective of this research was to evaluate the impact on concrete breakout capacity of anchors in tension due to delay in the nstallation using the puddle-in technique. The puddle-in technique is the process of installing an insert (anchor) into fresh concrete once the surface has been finished. The installation was delayed by up to 160 minutes. Another installation method, pre-installation, is the attachment of the insert to the formwork or reinforcement before the concrete has been poured. The results discussed were obtained from research conducted at Curtin University of Technology, Perth as an undergraduate research project. Twenty four anchors were tested in tension. The principal test variables were anchor installation delay (and hence, loss of slump of the concrete) and concrete compressive strength at the time of anchor tension testing. The anchor type and edge distances were kept constant. The anchors all failed due to concrete cone breakout failure mode. Several statistical analyses were conducted on the data; it was found that the imposed anchor installation delay did not affect anchor concrete breakout capacity, even when installation was delayed significantly resulting in zero slump concrete. However this conclusion is valid only when the anchors were tested with concrete compressive strengths around 15 MPa. The anchors tested at lower concrete compressive strength did exhibit a decrease in capacity when anchor installation was delayed

Fly Ash Based Geopolymer Concrete with Recycled Concrete Aggregate

Concrete is one of the most consumed resources in the world. With an increased global focus on environmental concerns such as global warming, sustainable development and recycling; alternatives to conventional concrete are being researched, such as geopolymer concrete. Geopolymer concrete replaces cement based binder with an alternative binder which contains no Portland cement. One type of geopolymer binder is that which contains fly-ash activated by an alkaline solution of sodium silicate and sodium hydroxide. Utilising recycled concrete waste from construction and demolition sites, that would otherwise be disposed of into landfill, as a source of aggregate offers a potential environmental and economic benefit. The term recycled concrete aggregate (RCA) is used to define aggregate produced from crushed demolition and construction waste.Used together, geopolymer concrete and recycled concrete aggregate eliminate the need for Portland cement and makes use of waste materials. Significant research has been conducted into both recycled concrete aggregate (RCA) ordinary Portland cement concrete and geopolymer concrete; however there was limited published data on using RCA in geopolymer at the time of this research. Thus the aim was to investigate the mechanical properties of geopolymer concrete with recycled concrete aggregate as partial replacement of the natural coarse aggregate. This paper reports on the outcomes of the research which indicate the potential of incorporating RCA in geopolymer concrete mixtures

Balancing the COVID-19 disruption to undergraduate learning and assessment with an academic student support package: implications for student achievement and engagement

In response to the COVID-19 pandemic-induced emergency pivot to online teaching and assessment, an Academic Safety Net was implemented at a regional Australian university to provide academic student support. Bayesian hierarchical models were used to compare student performance between 2019 and 2020. More students withdrew from subjects in 2020, while fewer students remained enrolled but failed. While there was no overall year effect for overall student achievement, exam achievement increased and on-course assessment achievement decreased in 2020. When achievement was analysed according to an assessment task change, a year effect emerged, with the magnitude and direction of the effect dependent on the task changes. The results indicate that the enrolment component of the Academic Safety Net was an effective equity measure that enabled students an extended opportunity to self-withdraw in response to general impacts of the pandemic; while the results component protected the integrity of results awarded during the emergency pivot

Performance of Slabs with varying Reinforcement Configurations

The subject of ductility of suspended slabs constructed with Class L mesh as primary reinforcement led to widespread industry discussion over recent years which led to the current provisions in Australian Standard 3600 - Concrete Structures (2009) [1] which outlines the analysis, design and detailing of such slabs. The aim of this research program was to examine the behaviour – in terms of ultimate strength and ductility parameters - of simply supported one way reinforced concrete slabs with differing reinforcement types with relatively consistent tensile steel reinforcing ratios of the order of 0.4%. Eight slabs were constructed with a range of reinforcing including (i) class L mesh only, (ii) class N reinforcing bar only, (iii) combination of L class mesh and N class bar or (iv) reinforcing consisting of two layers of class L mesh. The classification of the reinforcing is in accordance to Australian and New Zealand Standard 4671 – Steel Reinforcing Materials (2001) [2]. The behaviour of slabs reinforced with L class mesh and steel fibre reinforced concrete was also investigated. This paper presents the test data for 8 test slabs. Four of the slabs were duplicate tests; Control 1 and Control 2 had the same reinforcing arrangement consisting of mesh SL 102; and CS2 and N10 slabs both had 4 N10-220 in both directions ofslab. The testing of duplicate tests enabled an assessment of the variability of test data and sensitivity of the ductility parameter W1/W0

Bond Behaviour of Reinforced Fly Ash-Based Geopolymer Concrete Beams

In view of sustainable development in the construction industry, investigation has been carried out on fly ash-based geopolymer concrete, which is an environmentally friendly material that uses geopolymer paste as binder instead of Portland cement. Previous studies on the engineering properties and structural behaviour of geopolymer concrete have shown promising potential of this material. This paper describes the bond behaviour between geopolymer concrete and reinforcing bars in tensile splices in beams. Twelve full-scale beam specimens with lap-spliced reinforcing bars were cast and tested in the laboratory to study the bond performance of geopolymer concrete. The effects of concrete compressive strength, bar diameter and splice length of the bars on bond strength of lap splices in geopolymer concrete were evaluated. Test results, including general behaviour of beams, failure modes and cracking patterns were gathered and analysed. Current analytical models and codes provision to predict bond strength for Ordinary Portland Cement (OPC) concrete were used to analyse the bond strength of test specimens. Good correlation between test and analytical results were found. This study also demonstrates the excellent potential of geopolymer concrete for use as a construction material

Effective Teaching Practices for Aboriginal and Torres Strait Islander Students: A Review of the Literature

This paper presents a review of the literature pertaining to the teacher actions that influence Aboriginal and/or Torres Strait Islander student learning outcomes. This review investigates two foci: the identification of teacher actions influencing learning outcomes for Aboriginal and/or Torres Strait Islander students and the methodological approach to how the influence of teacher behaviours on student learning has been determined. The literature review identifies that published literature in the effective teaching area is predominantly in the ‘good ideas’ category; that is assertions are made by authors with no research-based evidence for supporting such claims, especially through quantitative research which seeks to test the influence of specific facets of quality teaching, especially those facets identified by Aboriginal and/or Torres Strait Islander students as the qualities of effective teachers. Where there is evidence supporting best practices, the evidence is primarily qualitative in nature. The review affirms the need for empirical evidence to “tease out facets of quality teaching that are salient to Aboriginal students; elucidate their perspectives of teacher quality; and test the influence of specific facets of quality teaching on academic outcomes and the consequences of the findings for developing interventions for Aboriginal and Torres Strait Islander students.” Craven, Bodkin-Andrews and Yeung\u27s (2007, p4

Interprofessional clinical placement involving speech pathology and counselling psychology: Two students\u27 experiences

This paper examines the interprofessional learning of a speech pathology and counselling psychology student in an interprofessional placement within an institution of the Department of Corrective Services in Perth, Western Australia. The institution is a pre-release centre that promotes rehabilitation and community reintegration in which up to six women are able to have their children, aged 0–4 years of age, live with them. The students provided a program to the mothers to facilitate development of a healthy mother–child relationship and the children’s communication development. This paper utilised qualitative descriptive analysis to explore two examples of student learning and found perceived growth in the students’ clinical skills, their understanding of the other profession and the concept of interprofessional collaboration. While students experience growth in a range of placements, the journey described in this paper is unusual in both the nature of the student collaboration and the placement itself. The research highlights the importance of joint clinical placements in the development of interprofessional collaborative relationships

Synchronous Deglacial Overturning and Water Mass Source Changes

Understanding changes in ocean circulation during the last deglaciation is crucial to unraveling the dynamics of glacial-interglacial and millennial climate shifts. We used neodymium isotope measurements on postdepositional iron-manganese oxide coatings precipitated on planktonic foraminifera to reconstruct changes in the bottom water source of the deep western North Atlantic at the Bermuda Rise. Comparison of our deep water source record with overturning strength proxies shows that both the deep water mass source and the overturning rate shifted rapidly and synchronously during the last deglacial transition. In contrast, any freshwater perturbation caused by Heinrich event 1 could have only affected shallow overturning. These findings show how changes in upper-ocean overturning associated with millennial-scale events differ from those associated with whole-ocean deglacial climate events