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Experimental Analysis and Numerical Modelling of Concrete Recycling Flash-Calcined Dredging Sediments

Boek - Dissertatie

As the world's largest manufactured product by mass, cement is responsible for 10% of the global anthropogenic CO2 emissions. The share of the cement industry in the total greenhouse gas emissions is only expected to increase due to the population growth and increasing industrialisation and urbanisation in developing countries. The most promising and well-established way to reduce the environmental impact of the cement industry is using supplementary cementitious materials (SCMs) as partial cement replacement in concrete. Considering the limits of the availability and production of the conventional SCMs, such as fly ash (FA) and blast furnace slag, new sources of high-quality SCMs are highly required to further reduce the CO2 emissions and contribute to achieving the United Nations sustainable development goals.This thesis investigates the beneficial reuse of dredging sediments from the port of Antwerp as a potential new SCM for the production of sustainable concrete, and is part of the on-going BIND-AMOR project. The dredging material is first processed into filter cakes in a state-of-the-art mechanical dewatering facility. After flash-calcination, the filter cakes become pozzolanic reactive, indicating the potential for its use in concrete. The main objective of this thesis is to assess the effect of calcined filter cakes (CFC) as an SCM on early-age properties of concrete, in order to understand its early-age deformation potential and predict its time-dependent deformations at long term. The influence of CFC blended cement on the hydration process, early-age concrete properties, mechanical properties, shrinkage and creep behaviour of concrete is experimentally investigated. The temperature development, mechanical properties development, shrinkage and creep development are modelled and a cracking prediction tool is developed in order to assess the cracking risk of CFC concrete.CFC enhances the hydration of ordinary Portland cement by the filler effect at early ages and by the formation of additional hydration products at later ages. The high specific surface area of CFC increases the water demand of concrete and requires the use of a superplasticizer, slightly delaying the setting. CFC blended cement reduces the early-age concrete strength, but increases the concrete strength at later ages due to the pozzolanic activity of CFC. A strength class of C45/55 is reached. Furthermore, autogenous and drying shrinkage are reduced due to the development of an autogenous swelling peak, the dilution effect and the altered porosity and pore size distribution. Also, CFC blended cement reduces basic creep of concrete. Finally, the thermal-shrinkage induced cracking risk of concrete is reduced by using CFC blended cement, as a result of the combined effect of the total strains, tensile strength and elastic modulus of concrete on the cracking risk.The results of this thesis clearly support the use of CFC as a new SCM for the production of sustainable cement and concrete in Flanders. Provided that rheology properties, durability properties, structural behaviour and bond behaviour are further investigated and relevant requirements are fulfilled, application of CFC blended cement for ready-mix concrete is envisaged.
Jaar van publicatie:2020
Toegankelijkheid:Open