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.

Ordinary portland cement (OPC) substitution by high contents of ground granulated blast furnace slags (GGBS) reduces the early hydration kinetics, causing a slower development of mechanical properties. Chloride are well known for their accelerating effect on OPC but are mostly used for specific applications, such as non-reinforced concrete, due to their detrimental effects regarding steel bars corrosion. However, GGBS-based concretes are known for their ability to resist chloride ingress due to their capacity to fix more chlorides in hydrates, hence reducing the free chloride available for corrosion. This paper aims to present a link between strength development and in-situ formation of aluminate based hydrates at early age in the presence of chloride salts. Isothermal calorimetry is coupled with XRD investigations to gather insights on the accelerating mechanisms and on the potential impact of GGBS on durability. SEM-EDS observations were conducted to determine the spatial distribution of products formation and anhydrous grains dissolution in the presence of chlorides. The resistance to corrosion of chlorides/GGBS blends is then studied by electrochemical tests.

As is known, more sustainable concrete has become the desired aim of many transportation departments. To produce more sustainable concrete, the emphasis has been placed on replacing cement with more sustainable materials and taken into account, materials cost and CO2 footprint. High volume fly ash with hydrated lime mixtures have been proposed as one potential approach for achieving durable and sustainable concrete. In this first phase study, performance ranking analysis approach is presented to optimize the performance of high volume fly ash mortars. A total of 15 mortar mixtures were prepared at different replacement levels (up to 75 percent). Hydrated lime was incorporated with ASTM Class C fly ash to increase hydration reaction at different dosage levels (between 0-15 percentages). Fresh properties and semi Adiabatic temperature tests were conducted for each mixture. Compressive strength, drying shrinkage, bulk electric conductivity, and electric resistivity (surface) were measured and monitored until the age of 90 days. Cost efficiency was also evaluated. Based on performance ranking approach, five different binder compositions were selected to conduct the second phase of this study.

In this paper, it is shown that Class F fly ash can be effectively used in high volumes as a supplementary cementitious material. High Volume Fly Ash (HVFA) use is of interest in promoting the development and application of green materials. In South Africa, there is little or no literature on high volume incorporation of locally available fly ash in concrete. In this investigation, six different concrete mixtures with water/cementitious ratios of 0.3 and 0.45, were used. The mixtures consisted of 0, 30, 50 and 70% fly ash. Tests carried out were workability, compressive strength and heat of hydration. Large 300 mm cubes were used to study hydration heat development in fresh concrete. As expected, concrete strength decreased as fly ash content increased owing to the slower rate of strength development in fly ash mixtures. It was found that heat of hydration generated in HVFA mixtures gave lower peak temperatures compared to mixtures without fly ash, producing reductions of 27% to 43.5% in peak temperatures for mixtures containing 50% and 70% fly ash respectively. Temperature simulation using ConcreteWorks gave predictions correctly depicting the measured temperature profiles but with slight under-estimation of peak temperatures.

Cement production is an energy-intensive process, responsible for a significant amount of the world’s carbon dioxide emissions. Over the last years, geopolymers have been often promoted as an ecologically friendly alternative with low CO2 footprint. The presented work proposes curing of geopolymers at ambient temperature for application as construction materials. Different aluminosilicates like fly ash, metakaolin, slag and combinations thereof are evaluated as binders. Furthermore, the influence of alkali silicate activator (water glass), with respect to type and molar ratio, on the resulting geopolymer properties is investigated. This paper discusses characteristics of ambient temperature cured geopolymers, such as workability, mechanical, and physical properties. The achieved mechanical properties represent medium performance as well as high performance.