%mass %volume Composition of concrete Concrete cement water sand gravel air Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Typical Swiss Plateau gravel composition: impure limestone 60-70% Concrete Aggregates Typical Swiss Plateau gravel composition: impure limestone 60-70% quartzite 20-30% gneiss and granitoides 5-15% soft compomponents 1-10%v Important properties of concrete admixtures: shape and surface rugosity cleanliness Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Aggregate properties I Concrete Aggregate properties I Gravel shapes angular subangular subrounded rounded well rounded Relationship between aggregate and concrete properties aggregate concrete cement/admixture properties handling adhesion dirty bad very bad well rounded,smouth good bad angular bad very good angular with neg. angles bad bad Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Aggregate properties II Concrete Aggregate properties II %mass Granulometry size Ideal grain size distribution according to SIA 162 It is important to have enough fines in the admixtures. Cleaned sand is usually to coarse. Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Aggregate properties III Concrete Aggregate properties III Influence of the aggregate granulometry on concrete properties water 174l/m3 198l/m3 w/c 0.58 0.66 air content 0.8% 1.6% compr. strength 34.4N/mm2 26.7N/mm2 Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Aggregate properties IV Concrete Aggregate properties IV Bad aggregates due to bad due to reactivity frost resistance cement components molasse gypsum conglomerates anhydrite marls pyrite schists carbonaceous matter rauwacke organic matter porous limestones clays chlorides Concrete types conc. bad type admixtures 0-5% B30/20 5-10% " , has to be tested 10% B20/10 or B25/15 10-15% ", has to be tested >15% can not be used Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Aggregate properties V Concrete Aggregate properties V Pore volume of packed aggregates Influence of the pore volume on cement dosage pore volume of packed gravel (%) frequency pore volume of packed gravel (%) Cement dosage (kg/m3) w/c Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Concrete Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Properties of fresh concrete Slump tests The larger s or AM the higher the workability Measuring AM in the field Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Admixtures I Concrete Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Additives II Concrete Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Plasticizer and Superplasticizer I Concrete Plasticizer and Superplasticizer I Lignosulfonates (5) are complex polymers composed of molecules such as 1 to 4 Sulfonated melamine (6, 7) and naphtalene formaldehyde polymers Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Plasticizer and Superplasticizer II Concrete Plasticizer and Superplasticizer II Surface charge The surface charge will be compensated by ions and polar molecules in the solution. A layer of adsorbed ions is followed by a diffuse layer with higher electrolyte concentration. The potential within this double layer decreases with increasing distance from the surface. The width of the double layer can be influenced by the concentration and the type of the electrolyte. + + + - - + - + + + - + - + - + - + + + - + - - + - + - Potential (V) + Potential (V) + - + - + - + + + - - + + + - + - - + - - + + - + + - + - - - + + + - + - + - distance distance Double layer model Potential for high and low electrolyte concentration0 Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

+ + Plasticizer and Superplasticizer III Concrete Steric stabilization Polymers adsorbed at the surface of particles stabilize a suspension through different mechanisms: Ionic polymers with the like charge as the surface of the electrolyte will push the interface between Stern- and diffuse layer farther away from the surface, thus increasing double layer repulsion. - Compression or even interpenetration of adsorbed polymer chain can lead to either repulsion or attraction between the two particles. hydrophobic tail hydrophyllic tail + + Reduction of solvation of the polymer may decrase DH and therefore DG causing coagulation. Reduction of the mobility of the polymer chains due to interprenetration will increase DS and decrease DG. To reduce DG, the particle will separate again = steric stabilization . Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Effect of plasticizer on workability Concrete Effect of plasticizer on workability Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Air entraining agents Concrete Effect of air entrainers Optimal air content trapped air max. dia. of aggregate Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Retarders Concrete Effect of retarders Retarders are important if long transport distance are necessary (Gotthard south portal). Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

Effect of admixtures on water consumption and mechanical strength Concrete Effect of admixtures on water consumption and mechanical strength Effect of retarders water savings (vol%) mechanical strength admixtures (wt%) admixtures (wt%) Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008