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ABSTRACT Impressed Current Cathodic Protection (ICCP) is an established technique for the remediation of steel reinforced concrete structures. There have been examples of residual protection being afforded to structures where [...]

ABSTRACT Many research studies have been conducted during recent years on the topic of geopolymer materials based on the engineering performance of the concrete. What has been missing is the [...]

ABSTRACT Recent studies have shown that when the operation of steel reinforced concrete impressed current cathodic protection systems is halted the steel can remain passive for a period of time. [...]

ABSTRACT This paper examines the variation in bond strength in corroding specimens, before surface cracks are visible. Reinforced concrete specimens containing 16 mm and 12 mm diameter bars at covers [...]

ABSTRACT This paper reports the comparison of engineering properties of alkali activated slag (AAS) and low calcium fly ash geopolymer (FAGP) concretes up to 540 days. The results showed that [...]

ABSTRACT Geopolymer is a sustainable construction material produced by the activation of fly ash using a high concentration alkali to initiate a polymerisation reaction. A key parameter in determining the [...]

ABSTRACT A major challenge in the specification of geopolymer mix designs is the variability in the fly ash used and the impact of that variability on the performance of the [...]

This study presents the development and validation of a mix design determination procedure for geopolymer concrete to achieve the desired compressive strength. The procedure integrates artificial neural network (ANN) model developed based on a comprehensive data base from literature, data clustering, and parameter optimization techniques to enhance accuracy and reliability. Experimental validation is undertaken to demonstrate the mix design determination procedure’s capability to accurately predict mix designs for geopolymer concrete based on the target compressive strength, validating its efficacy for mix proportion determination. The integration of chemical oxide content in fly ash, curing time, curing temperature, and activator properties results in a 15.9% improvement in prediction accuracy for the training dataset and a 68.3% enhancement for the testing dataset, compared to the base ANN model that includes only the weight of fly ash and activator properties. Employing data clustering techniques enables the identification of prior estimates for the mix design parameters related to specific fly ash types and target compressive strength, streamlining the mix design process by analyzing pertinent data subsets. Parameter optimization ensures refined mix proportions, achieving the desired target strength economically while minimizing material waste and cost. The development of a user interface facilitates easy manipulation of mix designs, catering to users of varying expertise levels. Additional options for deeper insights into geopolymer concrete characteristics can be integrated into the mix design determination procedure. To assess the mix design determination procedure's ability to generalize effectively, a variety of fly ash samples with distinct chemical compositions were utilized, differing from those already present in the database. This approach allows for a thorough evaluation of the mix design determination procedure's performance when presented with fly ash compositions it has not encountered before. By doing so, this provides insights into the adaptability of the mix design determination procedure beyond the limitations of the training and testing datasets.

The long-term creep and shrinkage behaviour of two High-Volume Fly Ash (HVFA) concretes incorporating nano silica with 65% and 80% replacement of cement has been investigated. This comprised a detailed analysis of the microstructure, pore structure and chemistry of the two HVFA systems up to a period of 450 days. The compressive strength and modulus of elasticity of HVFA-65 concrete increased from 32 to 73 MPa and 30.3 to 40.5 GPa, respectively between 7 and 450 days. The HVFA-80 concrete achieved compressive strength values of 22 and 71 MPa and elastic modulus values of 28.9 and 37 GPa. After a total loading period of 450 days, HVFA-65 and HVFA-80 concretes displayed creep parameters, which were significantly below the values predicted by AS 3600, ACI 209 and CEB-FIP standard model equations. After a total drying period of 450 days 28-day cured specimens showed significantly reduced shrinkage compared to 7-day cured specimens. On the other hand, HVFA-80 concrete displayed higher shrinkage compared to the HVFA-65 specimens throughout the period. All specimens except for 7-day cured HVFA-80 concrete were within the maximum permissible shrinkage of 800 microns recommended for Australian construction practices. HVFA-65 concrete showed a denser microstructure and a stronger, better packed interfacial transition zone (ITZ) compared to HVFA-80 at all ages. The XRD and FTIR analysis data identified the formation of hydration products including C-S-H and C-A-S-H which contributed towards both the strength gain as well as the creep and shrinkage properties displayed by the HVFA concrete by minimizing the total porosity and pore size.

AbstractThe deposition of textile waste into landfill has reached an unsustainable level and raises serious environmental issues across the world. Transforming textile waste into fiber reinforcement in cementitious composites offers a sustainable resolution toward a circular textile economy. This article presents a comprehensive review of environmental concerns, recycling routes for textile waste, together with an in-depth review of the engineering properties of concrete incorporating recycled textiles. In general, the incorporation of these recycled fibers from textile waste enhances strain capacity, crack control, durability, and energy absorption of concrete viadual effects: bridging action (direct mechanism) and refinement of pore distribution (indirect effect). An improvement in compressive strength can be achieved by the utilization of a small dosage of recycled fibers or recycled fiber fabrics in concrete (strength < 40 MPa). Finally, the cost and environmental benefits for eco-efficient building application are also evaluated to draw the attention of researchers toward these potentially recyclable waste materials.

This article reports the results of an investigation into the efficiency of mechanical activation to increase the reactivity in alkali activated mortar synthesized from low-grade clay. Mechanical activation significantly changed the structure of clay, increasing the specific surface area, and decreasing the particle size. The 7-day compressive strength of mortar synthesized from untreated clay was 31.7 MPa, which increased to 35.3 after 4 h milling. A further increase of grinding time to 8 h did not result in any increase in compressive strength which is attributed to a decrease in the workability. However, the extent of reactivity did significantly increase as determined from solid-state MAS NMR, FTIR, and EDS analyses. Solid-state MAS NMR results revealed the increased formation of Q4(2Al) silicon sites, which is correlated with improved reaction. Furthermore, the EDS and FTIR analysis results indicated greater incorporation of aluminium into the matrix structure with increased grinding time.

A comprehensive experimental study has been conducted to investigate the geopolymerisation and compressive strength development of mortar made from brown coal fly ash from two separate locations in the storage ponds of an Australian power plant. The specimens gave similar compressive strengths but had significantly different material and performance characteristics despite being from the same storage location. The Loy Yang‒A (LYA) geopolymer mortar demonstrated an approx. 30% strength increase while Loy Yang‒B (LYB) gave an approx. 18% strength drop over the period from 7 and 90 d, though both geopolymer mortars initially achieved a similar 28-d strength of approx. 23 MPa. The LYA ash had almost double the alumina content compared to LYB and a higher proportion of AlVIcompared to the LYB. The lower alumina content coupled with the low quantity of AlVIin the ash and its lower conversion to AlVIduring geopolymerisation is identified as the primary reason for the reduction in strength observed in the LYB geopolymer. The increase of Q4(3Al) during geopolymerisation and some conversion to Q4(4Al) coordination over time resulted in the increase in the compressive strength observed in the LYA mortar. This strength increase of LYA mortar is further correlated with an increase in Quartz phases coupled with a reduction in the Moganite phase. Formation of sodium carbonate due to atmospheric carbonation of unreacted sodium hydroxide in Loy Yang geopolymer additionally contributed to the strength development of LYA geopolymer.

Steel fiber reinforced concrete (SFRC) is developed traditionally from ordinary concreteadmixed with randomly distributed steel fibers. The matrix of SFRC is always formed by adjustingthe mix proportion used for the ordinary concrete, which plays the role of controlling the properties ofSFRC. In this paper, the mix proportion of self-compacting concrete (SCC) compared with vibrationcompacted concrete (VCC) is statistically analyzed. A predictive formula for water-binder ratio isproposed in relation to the designed compressive strength of SCC and the cement strength affected bymineral admixtures. It is expected to provide reference for the mix proportion design for flowing andhigh-flowing SFRC.

AbstractControlled Permeability Formwork (CPF) has been shown to improve the durability of concrete by reducing the porosity of the cover concrete. However, research to date has focused on laboratory and short-term trials. This paper reports a long-term project in which specimens have been placed on exposure sites at three coastal locations in Australia for 5 years. The specimens include three materials, 100% Portland cement, 30% Pulverised Fly Ash and 65% Ground Granulated Blastfurnace Slag. Specimens were cured using traditional plywood formwork under wet hessian for 1 and 14 days and with CPF for 1, 7 and 14 days. The performance of the concrete was monitored at six monthly intervals by means of visual inspection, Ultrasonic Pulse velocity, resistivity and surface strength using Schmidt Hammer. At the conclusion of the 5 years, chloride ingress and the apparent chloride diffusion coefficient were determined from sample cores. The results showed that the CPF improved surface appearance and surface hardness of the concrete. In addition, chloride ingress was reduced by the application of CPF, with lifetime modelling indicating that service life expectancy could be improved by up to five times when compared to one day curing under hessian.

This paper reports on experimental work that has been undertaken to investigate the flexural strength performance of fly ash-based geopolymer (FG) concrete. The FG concrete was prepared using low calcium class F fly ash with high silicate content. The flexural strength properties of FG were assessed using modulus of rupture test up to the age of 360 days. Compressive strength and Ultrasonic Pulse Velocity (UPV) tests were also performed to corroborate the flexural strength test results. The results showed that the FG concrete demonstrates a comparable compressive strength and velocity to OPC concrete. Hewever, the flexural strength of FG concrete exhibited a better performance compared to that OPC concrete. The measured flexural strength of FG concrete also exhibited a higher value compared to the predicted one using ACI 318M-08 standard. The relationship between flexural strength with compressive strength demonstrated a similarity behavior to that OPC concrete. Thus, it can be concluded that the use of the ACI standard can be applied conservatively to determine the flexural strength of fly ash-based geopolymer concrete.

This study investigates the influence of the chemical and physical properties of two abundantly available waste by-products in Sri Lanka, fly ash and rice husk ash (RHA) as precursor materials for the synthesis of alkali-activated binders. The suitability of the two types of fly ash and the replacement of fly ash by RHA (10% and 20% by weight of the binder content) were assessed. The study reports the development of compressive strength together with an in-depth analysis of the reaction mechanism of the blended RHA alkali-activated binders. The 100% fly ash mortar achieved the optimum compressive strength of 38.9 MPa at 28 days. Replacement of the fly ash with 10% and 20% RHA reduced the compressive strength by approximately 14% and 43%, respectively. The higher specific surface area of RHA and relatively higher unburnt carbon content in RHA were identified as the major factors influencing the low compressive strength obtained. Furthermore, the addition of RHA increases the reactive silica in the gel matrix and leads to an increase in the Si/Al ratio (3.70–3.89), which has a negative effect on the compressive strength. The difference in solubility rate of precursor fly ash and RHA negatively affect the formation of the gel matrix which is hypothesized as a further reason for the lower compressive strength observed in the RHA mixes.

Port infrastructure is vulnerable to the corrosive marine environment leading to deterioration, loss of functionality, delays in shipping, major maintenance, remediation and, in the worst cases, loss of structural integrity and consequent replacement of the asset. Despite this, asset managers are unable to adequately plan for the prevention and minimisation of maintenance due to a lack of reliable predictive tools, that simulate the deterioration and a lack of a lifecycle model incorporating protection/maintenance options. This paper reports on a project to develop such a tool to facilitate the probabilistic modelling of the deterioration of reinforced concrete elements from construction through onset of corrosion to subsequent cracking and spalling. The Australian government funded project is in collaboration with several port authorities. The study has narrowed the key factors that have the most impact on the estimation of corrosion initiation and damage propagation allowing better definition of what data should be collected, how much and levels of accuracy required to ensure that predictive outputs obtained are as ‘robust’ as possible.

A research project continuing at RMIT University is exploring the resilience of port structures in a changing climate. Research completed to date comprises of identifying types of port infrastructure vulnerable to climate change, establishing materials and exposure conditions, developing deterioration models based on current knowledge to simulate the effect of climate change on key port infrastructure and modeling the selected elements of infrastructure to derive outcomes which will aid in decision making in port infrastructure management. A considerable effort has been concentrated on identifying input climate data most appropriate for the models developed. The modeling approach is presented in this paper for quantitative projections of damage probability on port infrastructure taking into account the variability of material type, design considerations and environmental exposures with a changing climate. This paper provides a summary of the research undertaken in the development of material deterioration models and their responses to a changing climate load. Using climate information drawn from historical weather records and future climate projections, existing deterioration models were refined to include climate data into modeling runs in order to analyse changes to deterioration rates of different materials when impacted by a change in climate variables. Outputs from this modeling process will assist port authorities in making informed decisions on maintenance and capital budget planning allowing for impacts of climate change.

As a part of the collaborative studies between China, Australia and the UK, examing sulfate attack on concrete, this paper reports the experimental results obtained from the Chinese laboratory. Specimens were immersed in sodium and magnesium sulfate solutions with concentrations of 500mg/L, 5000mg/L and 50000mg/L. Investigations were conducted over approximately a one year period. Susceptibility to sulfate attack was assessed in terms of changes in the mass and length of specimens, the compressive strength of the concrete, as well as the diffusion depth of sulfate-ions into the concrete at fixed intervals. Several differences were observed between these results and those reported in studies from the UK laboratory.