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

This work is part of a project aiming at investigating a new design approach for sustainable and durable concrete structures, which is based on the use of corrosion-resistant reinforcements in order to allow the use of chloride-contaminated raw materials (especially seawater and recycled concrete aggregate (RCA)). Changes in plain concrete properties, as well as the effects on embedded reinforcement (i.e., black steel and glass fiber reinforced polymer (GFRP)) have been studied. Three types of concrete mixes were produced: the first, a standard one, used as the benchmark; the second where freshwater was substituted with seawater; and, the third where chloride-contaminated RCA and seawater were used. For each mix, features of fresh concrete and mechanical properties of hardened concrete were studied. Further information was obtained by microstructural and chemical analyses. Additionally, durability was studied in terms of concrete and reinforcement resistance to aggressive environments. Results show that concrete is not negatively affected by the introduction of seawater in the mix while RCA plays a more important role in concrete properties. As already well established, the use of corrosive reinforcement, such as black steel, is discouraged in chloride-contaminated concrete because of the high corrosion rates due to pitting phenomena.

Concrete durability-related properties are known to be negatively affected due to expansion and cracking that result from factors such as freezing and thawing actions, alkali-aggregate reactions, sulfate attack, corrosion of the reinforcement, shrinkage, and other similar factors. Durability, and, therefore, sustainability of properly designed and constructed concrete structures depends primarily upon the quality of the materials of construction and other simple, but critical, steps. Concrete construction can last 100 years or more if five simple "steps" are followed: (1) materials selection; (2) structure design; (3) construction; (4) quality management; and, (5) timely evaluation, maintenance, and repairs. This is a holistic approach. Most mistakes are made in not satisfactorily following Steps 4 and 5. Conventional mixture proportioning technique used for production of high-strength concrete does not guarantee long-term durability of concrete. Concrete mixtures must be proportioned to attain desired workability, high-dimensional stability, high-strength, and high-durability related properties; i.e., high-quality concrete (HQC). However, mixture proportioning requirements for HQC must be varied according to the type and expected use of the concrete construction. HQC mixtures must have high-quality constituent materials: durable aggregates, low heat of hydration cement, mineral additives, and chemical admixtures. Furthermore, the mixing water must be minimized (i.e. a low water to cementitious materials ration, W/Cm). A strict quality control is also needed in various aspects of the production of HQC. Research activities conducted at the UWM Center for By-Products Utilization (UWM-CBU), CANMET, and elsewhere, have demonstrated that HQC mixtures can be proportioned to obtain strength in excess of 100 MPa (14,000 psi) and service life of 100 plus years.

With the adoption of a policy encouraging the use of recycled aggregates in concrete production, the EU is pursuing the twofold objective of reducing both the demand of natural resources and the environmental impact of the construction industry, that is characterized, as it is well-known, by a significant demand for both energy and raw materials. Therefore, recycling is the main action that can be implemented for turning waste into eco-friendly materials and constituents of newly produced concrete. Particularly, waste concrete can be processed and reused as coarse aggregate, leading to particular kinds of “green concretes” often referred to as Recycled Aggregates Concretes (RACs), in which ordinary coarse aggregates are partially or totally replaced by Recycled Concrete Aggregates (RCAs), while at the same time reducing the so-called Construction and Demolition Waste. However, no well-established theoretical models are capable nowadays of predicting the relevant properties of RACs depending on the actual mixture composition. This paper summarizes the key aspects of a novel physically-based conceptual approach aimed at “designing” RAC mixtures. The formulations proposed in this study are based upon the results achieved from several experimental and numerical investigations carried out for various types of RCAs.

The need to develop greener concrete is increasing day-by-day with the desire to develop sustainable infrastructures, resource conservation, and contribution to the reduction in the causes of global climate change by reducing carbon footprint of concrete and concrete-making materials, through environmentally-friendly techniques of concrete manufacturing by using recyclable materials, for example post-consumer products. This paper describes the possible roles of post-consumer products namely: used tires, plastics, and glass in the manufacture of greener concrete. Extensive research findings from the studies carried out at University of Wisconsin-Milwaukee Center for By-Products Utilization (UWM-CBU) and elsewhere describing the technology for beneficial use of recycled materials obtained from post-consumer materials in the manufacturing of greener concrete has been presented in this paper. The goal is to not waste such materials because waste is wasted if you waste it; otherwise, it is a resource for a society to be beneficially recycled.