Durability of recycled concrete drs. ing. Joseph Miquel prof.dr.ir. Lucie Vandewalle ing. Luc Boeme prof. dr. ir. Tom Van Gerven ir. Caroline Ladang

Recycon RecyCon Mission: Sustainable building - Recycling of Construction and Demolition Waste in Construction Mission: Sustainable building - Durable materials - Energy efficiency - Reuse of materials after “End of life” Approach: Industrial Engineering - focus: economic value, solutions for existing problems and industrial opportunities - less: fundamental research Technologiecluster Bouw Technologiecampus Oostende Zeedijk 101 8400 Oostende luc.boehme@bwk.kuleuven.be tel. +32 50 40 59 45

Introduction Demolition Crushing plant Recycled aggregates Concrete plant Concrete In 2012, more than 11 Mt of rubble were processed as recycled aggregates. Currently, most recycled aggregates are used in low-grade applications such as road foundations and lean concretes. However, research has shown that recycled debris can replace coarse natural aggregates in several concrete high-end applications "ValReCon20: Valorisation of recycled concrete aggregates in concrete C20/25 and C25/30", Oostende: Boehme Luc, 2012. ISBN 9789090265759.

Current state of the art in Flanders

High-end applications Foundation Sub foundation … Road construction Structural concrete …. Precast concrete Architectural concrete SCC HPC Materials for cement ?

Abstract Phd The goal of this investigation is to determine the durability of recycled concrete, more in particular the resistance to acid, chloride penetration and frost/thaw attack. These durability issues present in many cases a determining factor for the use recycled concrete in industrial and civil building applications. The main reason why this concrete reacts differently compared to standard concrete is the presence of a more open pore structure due to the presence of old attached mortar on the surface of recycled aggregates. The study includes modelling of the water absorption, modelling the durability, relating this to the density of RCA and of recycled concrete, W/C- ratio and water content.

General introduction and outline Research strategy Recycled Concrete Aggregates Amount attached mortar Water Absorption Density Influence aggregate size Water Management Concrete Water absorption submersion Water absorption capillarity Resistance Aggressive Environment Frost/thaw Chlorides Acids

Recycled Concrete Aggregates

Composition of concrete Fresh Concrete Hardened Concrete mass v% [kg/m³] [%] air 6 12 +6% cement 300 10 cement stone 19 water hydration 90 9 => workability 60 sand 750 30 gravel 975 39 ±30% of the amount of cement is used to form cement stone Additional water evaporates and is replaced by air Air + cement stone + sand = mortar (±60%)

Influence aggregate size Coarse aggregates Coarse recycled aggregates Dmin ≥ 4mm Dmax <20mm Wabs <10% Fine recycled aggregates Dmin 0mm Dmax ≤4mm Wabs >10% Increased risk of contaminations All-in aggregates Fine aggregates

Problems with attached mortar One important difference between CRCA and natural aggregates is water absorption. The high water absorption of CRCA is linked to the presence of old mortar (de Juan and Gutierrez, 2009). Dry recycled aggregates behave like sponges in fresh concrete, thus impacting on the water/cement ratio (w/c) ratio. This ratio represents the water mass to cement mass ratio in a concrete mix, and is used as an indicator of durability and strength development. Boehme, L., Joseph, M., Anseele, T., Verstraete, S., "Assessment of water reducing admixture in concrete with recycled aggregates", in Central Europe towards Sustainable Building 2013 (26 - 28 June 2013, Prague), 2013, art. nr. CESB13_1128, pp. 317-320. Joseph, M., Sierens, Z., Boehme, L., Vandewalle, L., "Water absorption variability of recycled concrete aggregates", Magazine of Concrete Research, vol. 67, no. 11, 2015, pp. 592-597.

Influence of the old mortar The amount of mortar has an exponential influence on the water absorption and particle density of recycled concrete aggregates. (1) A. Akbarnezhad, K. Ong, M. Zhang, C. Tam en T. Foo, „Microwave-assisted benefication of recycled concrete aggregates,” Construction and Building Materials, vol. 25, pp. 3469-3479, 2011.

Smart Crusher WA24 5,2 -> 2,4

Simulation Industrial processes in laboratory

Lab scale simulation of industrial mortar removal processes

Water absorption model for coarse recycled concrete aggregates Abstract accepted by the CESB16 Scientific Committee

Relationship water absorption density – literature & experiments

Water absorption model for coarse recycled concrete aggregates WA(t) = MR5min + (MR1sec - MR5min) * e-kt – Wf k = f(d;Fl;ρrd) MR1sec = f(d;Fl;ρrd) MR5min = f(d;Fl;ρrd) Wf = f(d)

Water Management Concrete

Water Absorption model for (recycled) concrete

Water Absorption model for (recycled) concrete

Evaporation with changing Temperature

Resistance Aggressive Environment

Resistance to chloride penetration

Resistance to (weak) acids Joseph, M., Boehme, L., Cornelly, C., Anseeuw, I., Declercq, W., Vandewalle, L., "Recycled concrete in weak acidic environments", in Advances in Science and Technology, 2016.

Resistance to frost/thaw attack

Resistance to frost/thaw attack

Thanks for your attention For this presentation and all owned publications: https://www.researchgate.net/profile/Miquel_Joseph