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.

Important properties of the novel hybrid cement, H-Cement, are due to the use of fly ash, metallurgical slag, alkaline waste water from red mud deposits and ordinary portland clinker. H-Cement saves around 80 % of CO2 emissions compared to ordinary portland cement (OPC) production and enables effective recovery and safe disposal of industrial wastes. H-Cement is suitable for the preparation of ready-mixed concretes of strength classes between C8/10 (1160/1450 psi) and C30/37 (4350/5370 psi) and as a shrinkage reducing and alkali-silica reaction (ASR)-mitigation agent. This cement provides a slight expansion-reducing effect in permanent water curing at 20 °C (68 °F) and an evident shrinkage-reducing effect in permanent dry curing at 20 °C (68 °F) / 60 % R. H. and 40 °C (104 °F) / 15 % R. H. -air relative to OPC. The ASR is suppressed at 20 °C (68 °F) and 40 °C (104 °F) / 100 % R. H. -air cure.

Concretes made with blended portland cement containing high volumes of fly ash provide an alternative to conventional portland cement concrete for reducing CO2 emissions. This study evaluates mechanical and chemical activation of four fly ashes by assessing their effects on hydration and compressive strength. Results show the importance of the amorphous content in terms of compressive strength. The composition of fly ash is changed by a sieving process where certain particle sizes are retained; the amorphous silica and loss on ignition (LOI) contents varied depending on the fineness, hence affecting the performance of the fly ash in concrete. Reduction in particle size and LOI do not always lead to improvement in compressive strength. The effect of sodium sulfate, as activator, was significant at early ages for two of the fly ashes studied; the amount of portlandite consumption is reflected in the compressive strength evolution observed. However, sodium sulfate does not have the same effect on fly ashes with high amount of Fe2O3, where portlandite consumption is much lower.

The natural, e.g. autogenous, healing capacity of cementitious materials in concrete is a promising path to overcome the ecological problems and durability preoccupations inherent to civil engineering. But, recovery of mechanical from autogenous healing are due to ongoing hydration reactions highly dependent on the binder. In this study, the healing potential of different mixtures incorporating supplementary cementitious materials is discussed both from a mechanical and a permeability point of view. Mortars with a 25% cement mass substitution ratio by metakaolin or blast furnace slag were compared to reference ones. Healing performances were quantified after cracking at early age using three-point-bending tests. Recovery in mechanical properties were calculated from reloading curves while permeability recovery was estimated using a novel air permeability device. It appears that the blast furnace slag mixture exhibits very good performance compared to the reference and the one including metakaolin is relatively close to the reference.

A detailed investigation on the properties of concrete made with fly ash (FA) blended cement were carried out by characterizing such concrete in terms of physical and chemical composition at early-age. In addition, the effects of inland exposure condition on the durability performance of the concrete were also monitored via the carbonation depth. Concrete cubes were made using various concrete mixtures of water-binder ratios (w/b) = 0.40, 0.50, 0.60, 0.75 and binder contents = 300, 350, 400, 450 kg/m3. Concrete cube of 100 mm size were cast and cured in water for 3, 7, or 28 days, then characterized at early-ages. Companion concrete samples were exposed indoors or outdoors to undergo carbonation under natural environment. The concrete cube samples were characterized at 6, 12, 18 and 24 months of exposure in terms of carbonation depths. The results of the concrete early-age properties and medium-term durability characterisation were analyzed. The results show that, increased knowledge of concrete materials and concrete early-age properties as well as its exposure conditions were vital in durability considerations for reinforced concrete structures.