%mass

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

2. 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

3. Concrete Aggregate properties I Gravel shapes subrounded rounded well rounded angular subangular 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

4. 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

5. 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

6. Concrete Aggregate properties IV 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 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 Institut de Minéralogie et Pétrographie Université de Fribourg Technische Mineralogie ETHZ IMP 2008

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

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

9. Concrete 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

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

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

12. 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

13. 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

14. Concrete Plasticizer and Superplasticizer III 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

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

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

17. Concrete Retarders 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

18. 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