International Concrete Abstracts Portal

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

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.

The main objective this study was to investigate the effect of waste steel fibers on the mechanical properties of concrete. The steel fibers obtained from waste tires were used, and physical and mechanical properties of these fibers were determined as a first step of the study. Fibers having different aspect ratios were used in concretes at various amounts. A concrete without any fibers was also cast. Compressive, flexural and splitting tensile strengths of the concretes were obtained. Fracture energies were also obtained using a closed-loop testing machine. Results showed that post-cracking strength and toughness of the concretes containing waste steel fibers were significantly increased. Flexural and splitting strength of the concretes were also improved. The experimental results showed that the waste steel fibers recovered from waste tires could be used for the production of steel fiber reinforced concretes. Utilization of waste steel fibers can help to protect environment by reducing the need for steel fiber production. Thus, the reuse of waste fibers in concrete contributes to a more sustainable fiber reinforced concrete production. Since the costs of the waste steel fibers are substantially lower than the commercial steel fibers, more economical steel fiber reinforced concretes can also be obtained.

Concrete is the most versatile construction material. However, the image of concrete looks often one of something non-friendly from an environmental point of view. Further developments, “green chemistry” and new techniques, should continue to be introduced into the cement and concrete industry. This will provide distinct alternatives to OPC dominating inside cement market. Simultaneously new scientific and technological breakthroughs are required. One of such additional strategies is based on advanced concrete technology concepts, which enables the reduction of the quantity of cement used in concrete, by combining fillers and various admixtures. Another strategy is based on a new design of the structural component, to evaluate the use of different materials and to achieve an overall reduction of the environmental impacts. This strategy highlights Life Cycle Analysis and Design, Performance Standards for Durability, Environmentally Driven Design and the role of the reinforcement, because the conventional steel reinforcement contributes to environmental footprint as much as the cement in the concrete. Composite materials, including polymer composite reinforcement, non-metallic fibers and the external reinforcement for repair and strengthening, would be widely used in modern construction. Additional benefits of synergy between these different solutions might be realized leading to reduction of more than 50% of environmental load.

Estimation of energy and material input-output during the production and other lifecycle stages is the most basic and repeated procedure to evaluate the environmental impact. Therefore, it is important to develop an accurate, convincing and field-verified model for estimating the material and energy input-output at each lifecycle stages and at each plant or site. With this background, we have been developing energy-use estimation model at concrete production stage. In this paper, we firstly present the unique characteristics of concrete production process in Japan based on our previously proposed model. With this model, we statistically estimate three factors through the field questionnaire survey on ready-mixed concrete plants. The estimation has shown the following characteristics in electric consumption; 1) major manufacturing machineries such as mixer, belt conveyer and blowers are less electric consuming than facilities in constant operation (ex. air compressor), 2) around half of the constant electric consuming facilities can be stopped (at least in some conditions) when concrete shipping is not in queue, which may imply possible options for the reduction of electric energy-use.