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 study presents experimental and 3D correlation results of the microstructural hygrothermal behavior of hemp concrete. The experimental procedure was performed using non-destructive method’s X-ray tomography and digital microscopy. Hemp concrete specimens were scanned and examined at different relative humidity levels through a specifically developed processing protocol. The material response to temperature in the range of 25°C to 110°C where also analyzed via the 3D topology post-processing. After that, 3D correlation is performed on the reconstructed volumes, with fined resolution of 17μm/voxel, in order to quantify the various displacements due to the hygric load. The imaging data and the 3D correlation results allowed having access to the displacement field caused by the relative humidity and temperature solicitations on real structure of hemp concrete. These results provide reliable data on the microstructural evolution when studying aging or the material durability.

Slabs are subjected to many important drying effects due to their large exchange surface area, particularly plastic and drying shrinkage. The use of suitable mineral additions with shrinkage reducing properties is necessary to improve cement-based materials behavior. The aim of the experimental work carried out is to investigate the influence of natural hydraulic lime (NHL) and aerial lime (AL) on the properties of cement mortars at fresh and hardened state. A reference mortar was designed with a water-to-cement ratio of 0.6. At a constant paste volume, cement was replaced with increasing mass proportions of 12.5%, 25% and 50% of NHL. The approach used shows that the substitution of cement by either type of lime reduces plastic and drying shrinkage, but negatively affected rheological behavior and compressive strength. The findings of this paper highlight the benefits of lime/cement substitution on the volume changes in cement mixtures at early age and long-term.

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.