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 this paper, the carbonation resistance of various concrete mixtures incorporating supplementary cementitious materials exposed to atmospheric CO₂ concentration in Austin, Texas, USA, was investigated. The paper provides a detailed description on the creation of an outdoor exposure site to place and monitor concrete specimens under ambient air exposure conditions. Two exposure conditions were investigated, including specimens that were placed outdoors unsheltered and in sheltered environments protected from direct rainfall. The depth of carbonation was measured after 730 days of exposures. Additionally, relative humidity (RH), temperature, and environmental CO₂ concentrations in the air were also monitored at the site to provide a general indication of the conditions at the exposure site. Various factors were investigated including water-cementitious materials ratio, type and dosage of supplementary material, and cement type. The depth of carbonation of mixtures without supplementary material was moderate. The addition of supplementary material significantly increased the carbonation depth, especially when replacement levels exceeded 30% of cement by mass. The results were exacerbated for those concrete specimens that were placed outdoors but sheltered from direct rainfall.

Architectural works by major architects from the twentieth century have often been subject to restoration campaigns intended to redeem them from decay (sometimes from neglect) in order to present them as “monuments” of the twentieth century. In particular, in architecture in which exposed reinforced concrete plays a key role in architectural, figurative, symbolic and cultural terms, the theme of repairing/replacing the concrete cover is a fundamental issue in the restoration project. Analyzing the methods, materials and techniques of intervention used in several campaigns of restoration of buildings built before World War II (the church of Notre-Dame du Raincy by Gustave and Auguste Perret in France and Rudolf Steiner’s Goetheanum at Dornach near Basel in Switzerland) or after the War (Figini and Pollini’s housing built in Milan and the Olivetti Factory in Crema by Zanuso) provides an opportunity to identify best practices, and also critical factors and weaknesses of the different approaches used in the restoration of these buildings from the 1980s to the present.

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.

The existing assets need maintenance actions (assessment, repairs and prevention) and related construction works share is increasing in Europe; ISO International Organization for Standardization through its competent Technical Committees has then recently carried out an important activity on reliability, durability and maintenance of concrete structures publishing basic, fundamental Standards concerning these subjects. CEN is planning the revision of the Eurocodes with the same objectives. Italy shows risky contexts, synthetically analyzed, which strongly suggest to improve planning, design, construction and maintenance practices for new and existing concrete structures. Designing for durability and maintenance planning are strictly correlated. This paper, focusing on the above subjects, analyzes specific issues: design guidelines, briefing, maintenance procedure and design validation.