International Concrete Abstracts Portal

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

The research aims at studying an innovative construction system (called S.E.Con. System1 - Sustainable Ecological Construction System) to realize sustainable buildings, having both acoustic and thermal high performance, in which the seismic-resistant structural elements are small reinforced concrete walls widely spread on the perimeter of the building and where all vertical structural and secondary elements (infill panels) are constructed using shotcrete. The results of experimental tests on a single story sample building and on structural walls, aimed to assess the structural, acoustic, and thermal insulation performances of the devised system, demonstrate that the system appears suitable for high seismicity areas, and that thermal and acoustic criteria set for passive constructions are met. Finally, an evaluation of the carbon footprint (CFP) has also been carried out, demonstrating a reduction of about 30% in the CFP of the construction system with respect to traditional construction systems.

The demand for the development of a more efficient and durable transportation infrastructure is among the top priorities of highway authorities worldwide. In the United States, the economic impact of steel corrosion for concrete highway bridges is estimated to exceed 15 percent of total annual costs. Degradation affecting steel reinforced concrete (RC) bridge superstructures exposed to harsh environmental conditions is not limited to decks, but includes railings and barriers and can significantly compromise their crashworthiness. Glass fiber reinforced polymer (GFRP) is highly suitable for reinforcing concrete structures subjected to corrosive environments and a number of projects have demonstrated its viability as an alternative reinforcement for bridge decks. Until recently, most traffic barriers using GFRP bars were vertical-faced systems. However, the impact time duration of vertical-faced barriers is shorter causing higher peak forces to be transferred to vehicle occupants. Nowadays, GFRP manufacturers can produce standard bar bends which can be used for the reinforcement of safety-shaped concrete railings and barriers. The implementation of GFRP bar bends requires some changes in the current design philosophy for railings and barriers. Whereas the overall goal of the research program is to make the technology of concrete bridge reinforcement with composites available to bridge owners and professionals, this paper provides the principles for the design of safety-shaped GFRP-reinforced concrete railings/barriers.

Diffusion and migration are the two major transport ways of chloride ions in concrete. The single-species models were usually used to predict the chloride diffusion and migration behavior. However, the diffusion and migration processes of chloride ions in concrete are more complicated than expected. The single-species models have obvious limitations in predicting the diffusion and migration processes. In this paper, two multi ionic models are introduced to predict the chloride diffusion and migration processes, respectively. In the diffusion model, the ionic actions and multi-phase reactions are both considered in order to simulate the realistic situations. In the migration model, the ionic actions are also considered while the multi-phase reactions are ignored due to the strong electrical field force applied in the migration test. Besides, a pore structure hypothesis is assumed by a simple deduction to distinguish the migration process from the diffusion process. By considering the factors mentioned above, the governing equations of diffusion and migration models are deduced respectively. In order to verify the multi ionic models, two numerical examples and the verification tests are also conducted. The results show that the multi-ionic models are feasible to predict the chloride diffusion and migration in concrete.