POWERFUL CONCRETE SUPERPLASTICIZERS FOR ALKALI-ACTIVATED BINDERS 2 - PowerPoint PPT Presentation

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

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

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

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

INTRODUCTION WORKABILITY MECHANISM steric repulsion electrostatic adsorption 5

INTRODUCTION WORKABILITY STRUCTURE-PROPERTY RELATIONSHIP 6

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

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

POLYMER SYNTHESIS random PCE F ree R adical P olymerization [ FRP ] 9

POLYMER SYNTHESIS well-defined PCE random PCE F ree R adical P olymerization [ FRP ]  not accessible with existing FRP technology 10

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

POLYMER SYNTHESIS F ree R adical C ontolled R adical P olymerization P olymerization [ FRP ] [ CRP ] Controlled Radical Polymerization Types  NMP: Nitroxide-mediated polymerization  ATRP: Atom transfer radical polymerization  RAFT: Reversible addition-fragmentation chain transfer polymerization 12

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

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

POLYMER SYNTHESIS  Design polymer architecture according the different needs 15

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

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

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

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

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

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

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

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

PCE IN ALKALI ACTIVATED BINDERS FRESH MORTAR PROPERTIES random-PCE block-PCE 20 20 ru (sc): 40 40 ru (ag): 2 2 C/E:  Same composition but different structure 24

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

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

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

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