Engineering Students’ Week Conference , March 2013 Department of Civil & Structural Engineering, University of Benin The Interaction Between Concrete and its Environment: An overview Wilson Okaka MSc(Eng) Structural Engineering ABSTRACT Engineers have been called upon to consider the role of concrete in global environmental preservation and wherever concrete or its utilization is a possible cause of environmental burden, they should formulate measures to mitigate it. The release of harmful quantities of CO 2 , noise pollution, fuel consumption which are associated with cement production, ecological disruption from quarries, and waste from demolition debris all work together to deplete the integrity of our environment. The environment on the other hand has significant impact on concrete’s fresh and hardened properties as well as its durability. The long term performance of concrete is influenced by the quality of its design and the aggressiveness of the environment to which it is placed. There is therefore a continuous two-way interaction between concrete and the environment which needs to be investigated further with the aim of quantifying the impacts and the respective rates of impacts. There is ongoing research to develop a type concrete that will be able to withstand all environmental effects and at the same time safe to the environment. This paper aims to identify the factors and processes in concrete manufacturing and usage that negatively affect the environment as well as measures to reduce this impact. Three levels of environment which concrete interacts with are identified: global, immediate, and amenity environments. It also includes the impact of the environment on concrete structures which is a key issue in the durability of concrete. It was concluded that a common scale for measuring this two-way impact between concrete and the environment is necessary for decision making. 1 INTRODUCTION Concrete is a versatile composite building material, such that when wet can be formed into many varied shapes and sizes ranging from simple rectangular column to a slender curved dome or shell. It is the second most consumed substance in the world after water [3]. We live, work, study or play in concrete structures as well as drive on concrete roads and bridges. Water dams, Electric power station houses are built from concrete. In the last century, difficult global environmental issues have been related to the manufacture and usage of concrete. This was exemplified during the United Nations Conference on Environmental Development (UNCED) Global Summit held at Rio Janeiro in June 1992 [9]. Global warming, one of such environmental problems, is being treated as a serious problem because of the increasing discharge of carbon dioxide into the atmosphere. Furthermore, in Japan, the “Action Plan for Prevention Global Warming” was adopted at the cabinet meeting in October 1990, and the target of “stabilizing carbon dioxide emission per person to 1990-levels after year 2000’’ was set [9]. The key issues of the global environmental impact of concrete includes the effectiveness of use of concrete material (recycling of demolished concrete waste), control of the excessive volume of Carbon dioxide (CO 2 ) released during manufacture of cement which is the main binding agent in concrete, energy saving construction methods, development of environmental friendly concrete and rational maintenance system. The environment on the other hand has significant impact on concrete’s fresh and hardened properties as well as its durability. The long term performance of concrete is influenced by the quality of its design and the aggressiveness of the environment to which it is placed. The deterioration mechanism can be physical deterioration as a result of freeze-thaw action, thermal cracking, and abrasion, chemical deterioration as a result of alkali-silica reaction, or sulphate attack and electro- chemical deterioration resulting in the corrosion of steel reinforcement or chloride contamination of the surrounding concrete.