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Many structures such as buildings, power plants, stacks, sea walls, bunkers, and tanks are built with reinforced concrete; and durability is a major concern. Corrosion of reinforcement is the most important process of deterioration. Reinforcement corrosion is prevented by maintaining appropriate quality of concrete mix, casting, and curing and by providing the requisite clear cover to reinforcement according to the postulated exposure. The provisions of several international codes were reviewed from these aspects. Many codes can be interpreted in favor of providing different clear covers on different faces of members in a reinforced concrete structure. The authors' interpretation of the Australian and New Zealand codes revealed that these specifically allow the above. However, this practice might lead to severe durability-related concerns, particularly due to corrosion of reinforcement. Case studies conducted with postulated data from a few international codes revealed that internal corrosion cracks might occur earlier than external cracks in certain cases. Internal cracks can be hidden from view and consequently lead to higher damage to the structure prior to detection. For the simultaneous occurrence of corrosion cracks on the internal and external faces of a member, the internal surface chloride concentration would have to be between 18% and 73.2% of the external, with a median of 38%. These could hardly occur in practice—except for treated air facilities. If construction periods are long, this durability issue would be applicable even for treated air facilities. Higher differences in clear cover between internal and external faces, and higher external chloride exposure – both call for larger reduction of chloride exposure from external to internal. Unless the members are designed for corrosion as specified in some (Japanese) codes, the authors advocate the conservative option of using the same cover for all faces of concrete members to achieve a lower life cycle cost of the facility. Practical Applications: Design codes across the world can be interpreted in favor of different clear covers (to reinforcement) on different faces of concrete members according to exposure conditions. Only the Australian and New Zealand codes specifically mention different clear covers for internal and external faces, by the authors' interpretation. This article examines the durability of concrete members with different clear covers on internal and external faces, with case studies generated from a few international codes. The results indicate that in such cases, corrosion cracks might occur on internal surfaces much earlier than the external surfaces. For cracks to occur simultaneously on both surfaces, the internal surface chloride concentration must be as low as 18% of the external, which is difficult to ensure in practice. Early internal cracks could be hidden from view on account of equipment or false ceiling/panels—thereby causing more damage before detection. They would be difficult to detect, to evaluate, and to carry out structural repairs. Therefore, it could be expensive to maintain and could adversely affect the service life of the structure. This study would sensitize the clients, regulators, and engineers to these concerns. The authors suggest that the conservative approach of the same clear cover may be adopted on all faces, according to the worst exposure on any face, to ensure the durability of the concrete structures. [ABSTRACT FROM AUTHOR]

Past earthquakes such as the Christchurch and Kaikoura events have highlighted the difficulties in residual capacity assessment and repair of plastic hinge damage in conventional reinforced concrete bridges. Also, with growing population densities in urban centres around the world, there is substantial interest in increasing earthquake resilience and minimising the disruption caused by new bridge construction. Two areas of research that address these aspects are low damage design and accelerated bridge construction. The aims of low damage design are to significantly reduce seismically induced damage to structural members, minimise residual drifts and limit damage to specifically designed components. At the University of Canterbury, New Zealand, within the bridge engineering space over the past decade or so, particular focus has been placed on these areas of research and their combination. This paper presents an overview of the extensive experimental work undertaken at the University of Canterbury on these topics for bridges. [ABSTRACT FROM AUTHOR]

• The durability and mechanical properties of self-compacting mortars were assessed. • The mechanical properties enhanced by increasing the content of NZ and NS. • NS and NZ has a positive influence on the microstructural properties of mortars. In this paper, durability and mechanical properties of self-compacting mortars containing various percentage of natural zeolite and nano-silica were assessed experimentally using compressive and flexural strength, water absorption, electrical resistivity and rapid chloride permeability tests. The results showed that the mechanical properties of self-compacting mortars would be increased by increasing the replacement levels of natural zeolite and nano-silica. Addition of natural zeolite and nano-silica increased the electrical resistivity of self-compacting mortars and consequently decreased the permeability of the self-compacting mortars. The chloride ion penetration into self-compacting mortars were decreased by increasing natural zeolite and nano-silica contents. It was also observed that the presence of the pozzolan and nano material has a positive influence on the microstructural properties and hydration process of self-compacting mortars. Additionally, the artificial neural network modeling could efficiently predict the durability mechanical properties of self-compacting mortars. [ABSTRACT FROM AUTHOR]

In recent years, binary and ternary use of supplementary cementitious materials (SCMs) has received special attention by researchers throughout the world. This can combine the benefits of each SCM and minimize its adverse effects on the properties of concrete. The main purpose of this study was to investigate the performance of high-strength concrete (HSC) produced by the combined use of 0%, 5%, 10% and 15% natural zeolite (NZ) and different nano-particles including 2%-4% nano-SiO2 and 0.5%- 1.5% nano-CaCO3 in aggressive environment. In this respect, different samples of HSC were made and besides slump and compressive strength; they are tested for chloride ion penetration depth and chemical resistance. The chemical resistance of HSCs were measured by evaluation the variations in the mass and crushing load of concretes after 28, 56 and 84 days of exposure to 5% sulfuric acid solution (H2SO4). Results showed that all HSC samples had a 28-day compressive strength greater than 81.36 MPa which passed the minimum strength value (= 60 MPa) considered in this study for HSC. Also, compared to using only NZ, by substituting the optimum level of nano-particles and NZ as SCM in HSC, lower depth of chloride ion penetration can be obtained. The results also revealed that the highest percentages of mass loss and crushing load loss were obtained for plain HSC which could decrease by the ternary incorporation of Portland cement, nano-particles and NZ. [ABSTRACT FROM AUTHOR]

The durability of epoxy-modified open-graded porous asphalt (EMOGPA) was measured against mixes using unmodified 80–100 penetration grade base binder as well as modified binder with 4% Sytrene-butadiene-styrene (SBS) polymer. Multiple tests were conducted to verify the durability of EMOGPA aged up to 194 days at 85 °C using an OGPA mix design (20% air void) typical of that used in New Zealand. Generally the indirect tensile moduli of the mixes improved as the concentration of epoxy bitumen increased. The fatigue life of EMOGPA was significantly better than those without epoxy modification. A modified abrasion test was developed and used to support claims that epoxy bitumen is less prone to oxidative ageing and thus can extend the life of standard porous asphalt. Even with substantial dilution of the binder with standard bitumen (as a potential means of reducing cost), the diluted EMOGPA mix was more durable than the 4% SBS binder mix both in terms of Cantabro loss and fatigue life but the SBS mix did perform better than the 80–100 control mix. [ABSTRACT FROM AUTHOR]

The weathering of commercial coatings on pine sapwood in Germany and New Zealand was studied. The New Zealand site had a climatic index 50% more challenging. Significant differences in performance relating to coating, species, site, and exposure are presented. The coating and site had the most significant effects, while species had the least. A solvent-borne stain and a hybrid paint qualified for stable end-use situations in both countries. An acrylic paint performed better in Germany while an alkyd gave the poorest performance of the four coatings tested. More effective fungicidal coating properties are required in New Zealand to suppress mold growth. Areas of deficiency for internationalizing the European weathering standard EN 927 are discussed. [ABSTRACT FROM AUTHOR]