International Concrete Abstracts Portal

The purpose of this international conference is to present the latest scientific and technical information in the field of supplementary cementitious materials and novel binders for use in concrete. The new aspect of this conference is to highlight advances in the field of alternative and sustainable binders and supplementary cementitious materials, which are receiving increasing attention from the research community. The conference was held in Montréal, Canada from October 2 to 4, 2017. The conference proceedings, containing 50 refereed papers from more than 33 countries, were published as ACI SP-320.

This paper presents results of studies on five different slag chemistry with different CaO/SiO ratios and reactivity with activators such as calcium hydroxide and portland cement. The hydration process is investigated through calorimetric data; the heat of hydration of alkaline activated slag goes through four steps was verified. The total heat generated by alkaline activation process follows logarithmic functions with time and is affected by slag chemistry and fineness. Slag blended with ASTM C150 Type I and Type II cements were studied as well. Concrete with blended slag cement compressive strength shows that Blaine plays as an important role as chemistry, possibly due to particle packing related effect. Also high performance concrete mixes with slag blended Type II cement have 12-14% compressive strength increase compare to concrete with slag blended with Type I cement at 56 days.

There has been a proliferation of research and development activity focused on chemically activated binder technologies and other alternative cements for use in concrete. Some activated binder technologies have been used successfully in construction or in manufacture of building products. However, a major barrier to adoption of such new materials is the lack of appropriate test methods and specifications, often precluding their use in structural applications since they are not covered by building codes. Some existing test methods may be suspect for evaluation of new cementing materials because they often do not relate well to field performance for portland cement concrete. However, engineers have experience, familiarity and a comfort level with using portland cement concrete. In addition to raising specific areas of concern with existing test methods, alternative approaches to adapting existing test methods or development of new tests specific to evaluation of chemically activated binders and alternative cements are discussed.

The cost of repairing and rehabilitating damaged reinforced-concrete structures in Canada and elsewhere continues to rise. Predicting the service life and life-cycle cost of these structures can help identify the most cost-effective solution. Many companies have joined with research partners on projects to develop reliable tools to predict the service life of concrete structures. Given the problem’s complexity, most of these projects are based on different modeling approaches producing widely different values, greatly limiting their application. Therefore, our project consisted in applying a connectionist approach, including artificial neural networks (ANNs) models and a database, to create an intelligent system. In addition, each ANN model better grasps the complex mechanisms of concrete degradation (carbonation, sulfate expansion, chloride-induced corrosion, etc.). The proposed system will yield a powerful solution for predicting the service life of concrete structures and be useful in designing new structures. It will significantly improve codes by contributing more realistic recommendations.

Finely ground glass produced from recycling facilities is an alternative supplementary cementing material that is often considered for eco-friendly concrete mix designs. However, documentation on its behaviour in concrete is limited or somewhat contradictory. Many studies suggest that glass powder can suppress the expansion of concrete due to alkali-silica reaction (ASR), while others suggest that its high alkali content maintains the expansive potential in concrete due to ASR and consequently limits its preventive character. The present work seeks to clarify the overall availability of alkalis in the pore solution of cementitious matrices incorporating glass powder. For this purpose, pore solution extraction had been conducted, on pastes containing 0%, 20% and 40% of Glass Powder and cements of alkali levels of 0.25%, 0.63%, 0.94% and 1.25% Na2Oe. The concentration of alkalis available in the pore solution was analysed after 28 and 91 days. Results showed that the effect of GP on the hydroxyl concentration of the pore solution is limited for cement of high alkali content and important for low alkali cement. Also GP tends to reduce the potassium concentration and increase the sodium concentration of the pore solution.