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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. [ABSTRACT FROM AUTHOR]

The 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 via dual 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 AlVI compared to the LYB. The lower alumina content coupled with the low quantity of AlVI in the ash and its lower conversion to AlVI during 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. [ABSTRACT FROM AUTHOR]

Controlled 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. [ABSTRACT FROM AUTHOR]

The deterioration of structures due to reinforcement corrosion is a major problem both in Australia and globally. The corrosion of the reinforcement can lead to rust staining, cracking spalling, and eventually structural failure if no remedial action is taken. In order to assess the condition of a structure a visual inspection is often the first step, with any defects noted. Further visual inspection or installation of monitoring equipment may then be made to identify any subsequent deterioration that occurs. These activities can often be time consuming and expensive, both in the undertaking and in the analysis of the data. This paper reports the use of laser scanning technology to monitor the condition and deterioration of reinforced concrete specimens and relate the level and rate of crack growth with a standard visual inspection. [ABSTRACT FROM AUTHOR]