International Concrete Abstracts Portal

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.

The Industrial Revolution in the middle of the 18th century determined mankind’s destiny. The mass production of goods increased the population at an accelerated rate, and, consequently, mankind is facing the risk of natural resources and energy depletion. The greatest challenge to mankind in this century is to ensure the sustainability of the “inhabitants” of the Earth. The basis of mankind’s social and economic activities is infrastructure and buildings. As a result, the construction industry has a far greater influence on the sustainability of mankind and the Earth. Unfortunately, the construction industry has little appreciation of these facts. In order to change from the “old” industry to a “new” industry, the concept of “sustainability” should be introduced as a fundamental idea. The fundamental aspects for considering the sustainability of mankind and the Earth are society, economy, and environment. The essence of the construction industry can be appreciated from these views. There exists interconnection among safety, cost, and environmental impact. In the existing “old” construction engineering, this interconnection is not dealt with systematically. This paper outlines the background on the necessity to introduce a “sustainability” philosophy into the construction sector and proposes a basic framework for sustainability design as a “new” design system