The effects of the addition of different nanosilica dosages (0.5%, 1%, and 1.5% with respect to cement) on compressive strength and durability properties of concrete with water/binder ratios 0.65, 0.55, and 0.5 were investigated. Water sorptivity, apparent chloride diffusion coefficient, electrical resistivity, and carbonation coefficient of concrete were measured. The results showed that compressive strength significantly improved in case of water/binder = 0.65, while for water/binder = 0.5 no change was found. Increasing nanosilica content, the water sorptivity decreased only for water/binder = 0.55. The addition of 0.5% nanosilica decreased the apparent chloride diffusion coefficient for water/binder = 0.65 and 0.55; however, higher nanosilica dosages did not decrease it with respect to reference value. The resistivity was elevated by 0.5% nanosilica for all water/binder ratios and by 1.5% nanosilica only for water/binder = 0.5. The carbonation coefficient was not notably affected by increasing nanosilica dosages and even adverse effect was observed for water/binder = 0.65. Further information of microstructure was also provided through characterization techniques such as X-ray diffraction, thermal gravimetric analysis, mercury intrusion porosimetry, and scanning electron microscopy. The effectiveness of a certain nanosilica dosage addition into lower strength mixes was more noticeable, while, for the higher strength mix, the effectiveness was less.

This review presents "a state of the art" report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1-the present paper-focuses on the use of binders alternative to

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The paper represents the "state of the art" on sustainability in construction materials. In Part 1 of the paper, issues related to production, microstructures, chemical nature, engineering properties, and durability of mixtures based on binders alternative to Portland cement were presented. This second part of the paper concerns the use of traditional and innovative Portland-free lime-based mortars in the conservation of cultural heritage, and the recycling and management of wastes to reduce consumption of natural resources in the production of construction materials. The latter is one of the main concerns in terms of sustainability since nowadays more than 75% of wastes are disposed of in landfills.

In Europe, stainless steel rebars have been used since the mid-80s, whilst in North America, their use has been progressively growing only since the mid-90s. Due to their higher resistance to corrosion in comparison to ordinary black steel bars, they have been employed in a wide number of applications worldwide to achieve the durability performance of reinforced concrete structures, especially in extremely corrosive marine environments or when long service lives are required. In this paper, a state of the art on the corrosion resistance of stainless steel bars is reported. In particular, the contribution of Professor Luca Bertolini in this research field is considered. Initially, different testing methods are presented to point out their advantages and limitations and then the results on corrosion behaviour of different grades of stainless steel bars (i.e. austenitic, ferritic and duplex), obtained especially with tests in concrete, are analysed. Afterwards, some of the recent applications of stainless steel bars are illustrated.

14Supplementary cementitious materials (SCMs), such as fly ash, pozzolan or blastfurnace slag, are 15 widely used to produce blended portland cements, since they lead to a significant reduction in CO2 16 emission in the production phase compared to portland cement. A practical and generally accepted 17 approach to evaluate the contribution of SCMs to the strength of the hardened concrete is through 18 the concept of the SCMs efficiency factor (i.e. k-value concept), which expresses the fraction of 19 portland cement that can be replaced by a SCM at unchanged strength. In the literature some studies 20 have also been focused on the use of the k-value approach also for the resistance against 21 carbonation and chloride penetration of blended portland systems. However, limitations of 22 applicability of SCMs efficiency factor to durability properties are not clear. In this paper the k-23 value of different SCMs, such as ground limestone, fly ash, natural pozzolan and ground granulated 24 blastfurnace slag, was investigated to detect firstly if it can be applied to carbonation-and chloride-25 related properties and, secondly, if strength can be considered as a proxy-criterion for durability 26 2 properties. Results showed k-values lower than 1 for all the SCMs with respect to compressive 1 strength and that these values were valid also for resistance to penetration of carbonation. As far as 2 the resistance to chloride penetration is concerned, k-values derived from strength tests were not 3 applicable and specific k-values should be evaluated; values higher than 1 were calculated for fly 4 ash and ground granulated blastfurnace slag, whilst values lower than 1 were obtained for ground 5 limestone and natural pozzolan. 6 7 Highlight 8 Efficiency factor k is often used as a practical approach for determination of the role of SCMs on 9 concrete strength. 10The applicability of k-values to durability-related properties is questionable. 11Strength -derived k-values showed to be appropriate as a proxy-criterion only for carbonation 12 resistance. 13Specific k-values are needed for chloride-resistance performance. 14 These k-values were around 1.5 for fly ash and slag and lower than 1 for ground limestone and 15 pozzolan. 16 17

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