PCE WITH WELL-DEFINED STRUCTURES AS POWERFUL CONCRETE SUPERPLASTICIZERS FOR ALKALI-ACTIVATED BINDERS

Transcription

1 PCE WITH WELL-DEFINED STRUCTURES AS POWERFUL CONCRETE SUPERPLASTICIZERS FOR ALKALI-ACTIVATED BINDERS 2 ND INTERNATIONAL CONFERENCE ON POLYCARBOXYLATE SUPERPLASTICIZERS 28. SEPTEMBER 2017 SIKA TECHNOLOGY AG JÜRG WEIDMANN

2 TABLE OF CONTENT 1 INTRODUCTION 2 POLYMER SYNTHESIS 3 PCE IN ALKALI ACTIVATED BINDERS 4 SUMMARY 2

3 INTRODUCTION STRUCTURE side-chain backbone anchor group random distribution of anchor group and side chains 3

4 INTRODUCTION STRUCTURE side-chain MECHANISM steric repulsion backbone anchor group random distribution of anchor group and side chains adsorption 4

5 INTRODUCTION WORKABILITY MECHANISM steric repulsion electrostatic adsorption 5

6 INTRODUCTION WORKABILITY STRUCTURE-PROPERTY RELATIONSHIP 6

7 INTRODUCTION EXISTING PCE WELL-DEFINED PCE Comb polymer Random distribution Defined by ratio between side chain and anchor groups Brush structure AB-block-structure Separated functionalities Defined by lengths of the blocks High local anionic charge density 7

8 INTRODUCTION very strong adsorptive capability unique mortar and concrete performance WELL-DEFINED PCE random PCE well-defined PCE Brush structure AB-block-structure Separated functionalities Defined by lengths of the blocks High local anionic charge density 8

9 POLYMER SYNTHESIS random PCE Free Radical Polymerization [FRP] 9

10 POLYMER SYNTHESIS random PCE well-defined PCE Free Radical Polymerization [FRP] not accessible with existing FRP technology 10

11 POLYMER SYNTHESIS FRP: Initiation Propagation Termination «fast» reaction final polymers are built immediately new chains start continuously 11

12 POLYMER SYNTHESIS Free Radical Polymerization [FRP] Contolled Radical Polymerization [CRP] Controlled Radical Polymerization Types NMP: Nitroxide-mediated polymerization ATRP: Atom transfer radical polymerization RAFT: Reversible addition-fragmentation chain transfer polymerization 12

13 POLYMER SYNTHESIS CRP: Initiation Propagation Termination «slow» reaction final polymers are built over time all chains start at the beginning P max (1) 1. [FRP]: with terminating reaction 2. [CRP]: without terminating reaction P (2) DP = M 0 R 0 conversion 0 conversion 1 13

14 POLYMER SYNTHESIS CRP: Initiation Propagation Termination «slow» reaction final polymers are built over time all chains start at the beginning (1) P max P max P (2) P conversion 0 1 conversion 1 14

15 POLYMER SYNTHESIS Design polymer architecture according the different needs 15

16 PCE IN ALKALI ACTIVATED BINDERS DEFINITION SCMs are materials that, when used in conjunction with OPC, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity or both. Fly Ash (Class C) Metakaolin Silica fume Fly ash (Class F) Slag Calcined shale 16

17 PCE IN ALKALI ACTIVATED BINDERS SUSTAINABILITY Reduces carbon dioxide production Reduces energy consumption Helps recycling some industrial byproducts APPLICATION BENEFITS Generally reduces material costs Improves strength of the hardened concrete Improves durability of the hardened concrete Reduce heat of hydration 17

18 PCE IN ALKALI ACTIVATED BINDERS DRAWBACKS Slag leads to a decreased early strength development [2]: M. Nili, M. Tadayon, «The Relationships between Setting Time and Early Age Strength of Concrete containing Silica fume, Fla ash and Slag» 18

19 PCE IN ALKALI ACTIVATED BINDERS mix-design (mortar) STRENGTH DEVELOPMENT cement Cem I 42.5N slag aggregates 0 8mm 525g 225g 3140g w/c 0.44 PCE dosage realtive to binder NaOH realative to slag 0.8% 1.25% NaOH activation leads to increased early strength 19

20 PCE IN ALKALI ACTIVATED BINDERS FRESH MORTAR PROPERTIES STRENGTH DEVELOPMENT random-pce are not compatible with alkaline activation NaOH activation leads to increased early strength 20

21 PCE IN ALKALI ACTIVATED BINDERS R-PCE-1 R-PCE-2 random-pce are not compatible with alkaline activation Depended on the structure the incompability is more significant 21

22 PCE IN ALKALI ACTIVATED BINDERS STRENGTH DEVELOPMENT NaOH activation leads to increased early strength 22

23 PCE IN ALKALI ACTIVATED BINDERS FRESH MORTAR PROPERTIES STRENGTH DEVELOPMENT block-pce are compatible with alkaline activation NaOH activation leads to increased early strength 23

24 PCE IN ALKALI ACTIVATED BINDERS FRESH MORTAR PROPERTIES random-pce block-pce ru (sc): ru (ag): C/E: Same composition but different structure 24

25 PCE IN ALKALI ACTIVATED BINDERS non-activated system alkaline-activated system PCE adsorption in presence of cement released calcium Random-PCE: insufficient adsorption in the presence of sodium Block-PCE: structures are able to adsorb even on unattractive particle surface 25

26 SUMMARY Structure Block PCE can only be synthesized by a controlled free radical polymerization (CRP). Block Polymers enable a very strong adsorptive behavior compared to random PCE polymers. The structures of these polymers can easily designed according the needs 26

27 SUMMARY Structure Block PCE can only be synthesized by a controlled free radical polymerization (CRP). Block Polymers enable a very strong adsorptive behavior compared to random PCE polymers. The structures of these polymers can easily designed according the needs Application Well-defined polymers are compatible with alkali-activated binders in contrast to existing random-structured PCE. Early strength development can be enhanced by adding alkaline without loosing fresh concrete properties when well-defined polymers are used. 27

28 THANK YOU FOR YOUR ATTENTION