International Concrete Abstracts Portal

Service life calculations are now treated more in detail in standards and in particular in fib Model Code 2010. The new performance is introduced in addition to probabilistic calculations. In spite of the advances made it is necessary to apply the new approaches with care because any of the existing models have been calibrated in the same concrete more than a couple of decades and then, the predictions may present substantial errors. In addition, the calculation of the propagation period and the limit state of corrosion are aspects not well defined as the MC2010 does not considers any model for the propagation stage. In present paper are analysed some aspects of service life models proposing improvements. A universal statistical distribution of chloride threshold is presented and the consideration of an Initiation Limit State as defined by ISO 13283 is proposed for the depassivation onset. Finally, are illustrated trough examples that the probability of failure for deterioration processes should not be a fixed value but it would depend on the rate of deterioration.

In the present work, a coupled environmental-mechanical damage model for structural analysis of RC elements subjected to aggressive action - originally developed by some of the authors - is presented and further enhanced, introducing some innovative formulations. In particular the effect on structural performance of rebars corrosion, induced both by chloride attack and carbonation, and of freeze-thaw cycles is analyzed. To this aim, the environmental damage parameter is re-formulated and splitted in two contributions in order to better represent the degradation of concrete caused by cracking due to different processes (e.g. development of expansive products during corrosion, pressure induced by internal ice formation). The proposed models are implemented in the finite-element framework OpenSees, developed at Berkeley, University of California and validated by comparison with a number of experimental tests. In the first part of the paper the proposed constitutive models are introduced discussing the most relevant features and characteristics. Then, in the second part of the paper, the validation tests are presented and the obtained results are compared with experimental ones, proving that the model is suitably accurate in reproducing the main aspects observed during experiments: i.e. failure load, ultimate displacement and failure mode.

In relation to reinforced concrete high-rise buildings built in the Fifties and Sixties of the 20th Century, it has acquired importance, in the last few years, the analysis of the capabilities to withstand various kinds of environmental risks, defined according to actual parameters. The provisions prescribed by new structural design codes practiced today, indeed, have substantially changed both design actions and verification procedures as well, if compared to the building criteria in use in the past. This kind of analysis gives evidence to specific design performances which are seen as prevalent nowadays but were not considered in older versions of the codes, as the earthquake loads. In the present work this problem is discussed with reference to the case study offered by the Milan Municipality 25 story r.c. building erected in Milano in the ‘60s. Typically, this kind of buildings were designed for the effect of vertical loads and wind lateral loads only. At present, after being recognized of strategic importance for the society, they have to be verified also for the seismic resistance. Although the seismic hazard is classified as low in the area of Milano, design seismic forces are a little more severe than wind actions for this building, due to the limited ductility resources available in the structural elements, mainly in the shear walls. Consequently, the value which can be assigned to the load reduction factor is extremely low.

Editors: Mario Alberto Chiorino, Luigi Coppola, Claudio Mazzotti, Roberto Realfonzo, Paolo Riva

With the dawn of twenty-first century, the world has entered into an era of sustainable development. The main challenge for concrete industry is to serve the two major needs of human society, the protection of the environment, on one hand, and - on the other hand - meeting the infrastructural requirements of the world growing population as a consequence of increase in both industrialization and urbanization. In the past, concrete industry has satisfied these needs well. Concrete is an environmentally friendly material useful for the construction of vast infrastructures. Skyscrapers, highway bridges, roads, water retaining structures and residential buildings are all testimonials to concrete’s use and versatility. However, for a variety of reasons the situation has changed dramatically in the last years. First of all, the concrete industry is the largest consumer of natural resources. Secondly, portland cement, the binder of modern concrete mixtures, is not as environmentally friendly. The world’s portland cement production, in fact, contributes to the earth’s atmosphere about 7% of the total CO2 emissions, CO2 being one of the primary greenhouse gases responsible for global warming and climate change. As a consequence, concrete industry in the future has to face two antithetically needs. In other words how the concrete industry can feed the growing population needs being – at the same time - sustainable?

ACI Italy Chapter has been playing a significant role in the last years in the broad area of concrete technology in Italy and, in particular, in the field of concrete durability and sustainability. ACI Italy Chapter has become increasingly involved in research and development dealing with durability and sustainability issues such as reduction in CO2 emissions, use of recycled materials and innovative products, design of durable structures and maintenance, repair and refurbishment of concrete infrastructures.

In October 2015, the American Concrete Institute Italy Chapter (ACI IC) and the Department of Civil, Chemical, Environmental, and Material Engineering (DICAM) of the University of Bologna sponsored the First International Workshop on “Durability & Sustainability of Concrete Structures” in Bologna (Italy). The workshop was co-sponsored by the American Concrete Institute and ACI Committee 201. The proceedings of the workshop were published by ACI IC as SP305. The proceedings consist of forty-eight refereed papers concerning reduction in green house gases in cement and concrete industry, recycled materials, innovative binders and geopolymers, Life Cycle Cost Assessment in concrete construction, reuse and functional resilience of reinforced concrete structures, repair and maintenance, testing, inspection and monitoring.

Many thanks are extended to the members of the technical paper review panel. Without their dedicated efforts it would not have been possible to publish the proceedings. The cooperation of the authors in accepting reviewers’ comments and suggestions and in revising the manuscripts accordingly is greatly appreciated.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-305

Calcium-sulphoaluminate cement (CSA) represents an eco-friendly alternative to ordinary portland cement (OPC), thanks to its lower energy consumption, special production process and raw materials. Life-Cycle Analysis (cradle-to-gate) according to ISO 14040 standard series showed a potential for substantial reduction of the environmental impacts, as well as natural resource use. Nowadays, CSA cement is being used more in construction industry thanks to its high early-age compressive strength and shrinkage-compensating behavior. This paper presents concrete mixtures with pure CSA and with OPC-CSA blends both in terms of environmental impact indicators from Environmental Product Declarations, and in terms of mechanical and rheological performance focusing on workability, compressive and flexural strength development, drying shrinkage and dynamic elastic modulus evolution from very early ages.