0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 2 4 6 8 10 12 A d s o rp ti o n (m g p o ly m e r / g c e m e n t) Polymer concentration in IS (g.L-1) PCE1 PCE2 PCE3 Langmuir 0 20 40 60 80 100 120 140 160 180 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 In iti al setti n g ti m e (m in ) Dosage of admixture (wt%) PCE1 PCE2 PCE3 CA 0.2CA+0.2PCE1 0.2CA+0.2PCE2 0 50 100 150 200 250 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 F in al setti n g ti m e (m in ) Dosage of admixture (wt%) PCE1 PCE2 PCE3 CA 0.2CA+0.2PCE1 0.2CA+0.2PCE2 0,1 1 10 100 1000 0 50 100 150 200 250 Y iel d str ess τ0 (Pa) Time (min) SAC 0.2PCE1 0.2PCE2 0.2PCE3 0.2CA 0.2CA+0.2PCE1 0.2CA+0.2PCE2 0% 20% 40% 60% 80% 100% 120% 0 20 40 60 80 100 120 A d so rp ti o n (%) Time (min)
PCE1 in 0.2CA+0.2PCE1 PCE1 in 0.2PCE1 CA in 0.2CA+0.2PCE1 CA in 0.2CA
Hydration and rheology of sulfoaluminate-belite cements (SAC) in
presence of polycarboxylate superplasticizers (PCE) and citric acid
R. Belhadi*, A. Govin & P. Grosseau
Mines Saint-Etienne, Univ Lyon, CNRS UMR 5307 LGF, Centre SPIN, Departement PMMG, F - 42023 Saint-Etienne France
* rachid.belhadi@emse.fr
1. Context
Effect of the chemical structure of PCE on the
hydration and rheology of reactive SAC
Commercial SAC (i.tech ALI CEM) Citric acid (99,5% Honeywell)
3 polycarboxylates ethers (PCE1, PCE2 and PCE3)
Phase composition of SAC (%) C4A3$ C2S C$ 49,3 15,1 23,5 Mw (g/mol) Charge density (mmol/g) P N n PCE1 48300 0,79 45 5 12 PCE2 138600 0,3 114 5 15 PCE3 11900 0,96 17 2,5 115 EN 196-3 Standard
SAC
C4A3$ C2S C$Greener than OPC Poor workability
+
PCE
Dispersing effectiveness Rheological properties+
Citric acid
(CA)
Hydration delay??
Dispersing effectiveness of PCE may be affected by :Total Organic Carbon Ionic Chromatography Mini -Con e V icat Nee dle
Initial Setting Final Setting
CA delays significantly the Initial and Final setting times
PCE + CA Initial & Final setting: PCE+CA > CA > PCE
𝜏0 = 225𝜌𝑔𝑉2 128𝜋2𝑅5(1 + 225 128𝜋 3𝑉𝑅−3)
2. Objectives
3. Materials
4. Methods
6. Conclusions & Perspectives
PCE CA + PCE
Adsorption of CA from 97% to 87% in presence of PCE1
The amount of PCE adsorbed decreases in presence of CA
+
+
SAC
Reactivity of SAC
Competitive adsorption between Citric acid and PCE Adsorption of PCE + CA Adsorption of CA Chemical Analysis Centrifugation Measuring Setting time Measuring Spread flow Calculating Yield Stress
Understand the :
PCE1 + CA ≈ PCE2 + CA % in PCE Initial & Final setting: PCE1 > PCE2 ≈ PCE3
Short setting time of SAC without admixtures Fast hydration of
C4A3$ with C$
Ettringite C6A3$H32
Slight increase in initial fluidity Workability retention over time CA
CA + PCE
Initial fluidity compared to SAC
Workability retention over time
Affinity of PCE with SAC : PCE1 > PCE2 > PCE3 Maximum adsorption : PCE1 > PCE3 > PCE2
the better dispersing efficiency of PCE1
Effect of combination of citric acid with PCE
on hydration and rheology of reactive SAC
The amount of PCE adsorbed increases over time
Competitive adsorption
Initial fluidity compared
to PCE alone
Setting time : PCE1 > PCE2 ≥ PCE3
Dispersing effectiveness : PCE1 > PCE2 > PCE3 Adsorption : PCE1 > PCE2 > PCE3
CA Setting time : CA > PCE
Adsorption : CA > 97% >> PCE
Workability retention
over time
Effect
Adsorption : CA > 87% > PCE & PCE < PCE alone
Initial fluidity compared to PCE alone
Workability retention over time
CA reduces the amount of ettringite at early age
The amount of PCE
consumed by intercalation
Rheological properties
TGA & DRX are required to follow the hydration
Hypothesis
+
Fast setting_
_
p a b N=a+b n5. Results
Fast 𝜏0 Fast workability
𝜏0 Initial fluidity
PCE
Initial 𝜏0 with PCE1 < PCE2 < PCE3
!
Dispersion efficiency of PCE1 > PCE2 > PCE3R : Spread radius 𝜌 : Paste density
V : Mini-cone volume
PCE PCE + CA
Setting-Time
Spread flow / Yield stress
Adsorption
Setting time : PCE + CA > CA > PCE 0% 20% 40% 60% 80% 100% 120% 0 20 40 60 80 100 120 A d so rp ti o n (%) Time (min)
PCE2 in 0.2CA+0.2PCE2 PCE2 in 0.2PCE2 CA in 0.2CA+0.2PCE2 CA in 0.2CA
the lowest dispersing efficiency of PCE3 Explain
