Tools for assessing damage in concrete affected by AAR coming from fine and coarse aggregates
Over the last few years, comprehensive management programs for the diagnosis and prognosis of alkali-aggregate reaction (AAR) in aging concrete structures were developed in North America, based on a series of laboratory test procedures. Although promising, these lab-procedures presented several parameters whose impacts were not completely understood, which significantly reduced their applicability for the appraisal of deteriorated concrete structures in service. In this context, it has been suggested that two lab-tools, the Stiffness Damage Test (SDT) and the Damage Rating Index (DRI) could reliably assess the condition of concrete affected by AAR. This paper presents the condition assessment of 25, 35 and 45 MPa AAR affected concrete specimens incorporating fine and coarse reactive aggregates and presenting different distress degrees (i.e. expansion levels from 0.05 to 0.30%) through the use of an innovative multi-level approach. Results show that both SDT and DRI are suitable for assessing damage in AAR affected concrete through their output parameters. Yet, they present a complementary character, which illustrates the need for a multi-level approach.
Structural Low Cement Content (LCC) Concrete: An Eco-friendly Alternative for Construction Industry
Pressure is mounting in the civil construction industry to adopt more environmentally sustainable methods to reduce CO2 emissions. It is essential that the concrete industry consider its carbon footprint amongst increasing demand and tightening environmental restrictions. One of the most efficient methods used to mediate this impact is to use concrete systems with low cement content, the so-called low cement content (LCC) concrete. This material addresses the issue in an innovative and eco-friendly manner through the use of more efficient mix-design strategies and by-products from other industries. Although sustainable, the use of LCC concrete in structural applications is relatively new, and its performance and long-term behaviour are still relatively unknown. This project aimed to mixproportion concrete mixtures with reduced cement amount through the use of packing theories. Evaluations were performed in the fresh and hardened states of the material, while gaps, recommendations, and further needs were highlighted. Results
Effect of environmental conditions on expansion in concrete due to alkali-silica reaction (ASR)
Abstract The environmental conditions to which a concrete element incorporating alkali–silica reactive aggregates is exposed play a major role in dictating the progression and manifestation of the reaction. This paper reports and analyses the results of research programs investigating the comparative evaluation of the effect of environmental conditions on the development of alkali–silica reaction (ASR) in concrete specimens stored in outdoor exposure at the authors' respective laboratories. This data is compared to samples subjected to laboratory testing (controlled environmental conditions). Concrete mixtures that incorporate reactive aggregates with varying reactivity levels are compared. The focus of this paper is on control concretes e.g. 100% opc + reactive aggregate (coarse or fine).