Influence of Addition Time of Superplasticizer on Rheological Properties of Self-Consolidating Cement Paste Azadeh Asghari Cookeville 2014, July 9-11 5th Advances in cement-based Materials
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Influence of Addition Time of Superplasticizer on Rheological Properties
of Self-Consolidating Cement Paste
Azadeh Asghari
Cookeville 2014, July 9-11
5th Advances in cement-based Materials
Goals of Research Project
l Robustness is the ability of SCC to maintain fresh properties due to small changes in the content of ingredients of the mixture.
l Main problem of practical application of SCC is robustness. l The project aims to understand the influence of the mixing
procedures and Addition sequence on the robustness of SCC-mixtures.
l The robustness mainly be investigated by means of rheology, specific parameters investigated are: -Mixing energy, by varying mixing time and mixing speed. -Addition time of the superplasticizer
Outline
l Goals of Research Project
l Rheometer l Concrete Rheology l Mix Designs l Mixing Procedure l Plastic Viscosity l Conclusions
Rheometer
l The Anton Paar MCR 302 Rheometer l With Coaxial Cylinder l Control Temperature at 23 degree
Pre-sheared to eliminate thixotropy
Concrete Rheology
l Rheology is defined as the science of deformation matter. l Concrete rheology measurements are typically expressed in terms
of the Bingham model, which is a function of: – Yield stress: the minimum stress to initiate or maintain flow (related to
slump) – Plastic viscosity: the resistance to flow once yield stress is exceeded
(related to stickiness)
The Bingham Model
Slope= plastic viscosity
Mix Designs
l Powder Mix Design (Reference) 1.5 liter:
l VMA Mix Design (Reference) 1.5 liter:
Cement type I/II (g)
Lime Stone Filler (g)
Water (g)
SP1
(g)
W/C W/P
1210.8 1210.8 665.9 5.2 0.55 0.275
Cement type I/II
(g)
Silica Fume
(g)
Fly Ash C (g)
Water (g)
SP2 (g)
VMA (g)
W/C W/P
1443.3 50.4 499.3 759.4 9.690 1.250 0.53 0.38
Mix Designs
l VMA Mix without VMA l VMA Mix with different type of SP l VMA Mix without FA & SF (replaced by volume
of cement) l VMA Mix with Limestone filler without FA & SF
(Replaced by volume of Limestone filler)
Mixing Procedure of Addition time of SP
During first 1 minutes
After 2minutes
30sec
100% of SP
50% of SP
0% of SP 100% of SP
50% of SP
0% of SP
With Water After Water
Outline
l Goals of Research Project l Concrete Rheology l Rheometer Procedure l Mix Designs l Mixing Procedure l Plastic Viscosity For Powder-type and VMA-type at Different Addition time of SP Presence of VMA Type of SP Presence of Silica Fume & Fly Ash Presence of Limestone Filler l Conclusions
Plastic Viscosity Viscosity at different addition time of SP
Mix design 1
VMA Mix
Powder Mix Change of water
equivalent 10 l /m3
Plastic Viscosity Presence of VMA
∆=0.084 ∆=0.074
Plastic Viscosity Type of SP
∆=0.076 ∆=0.074
Plastic Viscosity Presence of Silica Fume & Fly Ash
∆=0.084
∆=0.085
Plastic Viscosity Presence of Lime stone Filler
∆=0.074 ∆=0.045
Plastic Viscosity Viscosity at different addition time of SP
Mix design 1
VMA Mix
Powder Mix Change of water
equivalent 10 l /m3
Conclusions
l Robustness is a significant problem slowing down the application of SCC. The variations in rheological properties of SCC-cement pastes were investigated by changing the addition time of SP.
l For the VMA-type mix design studied, the rheological parameters are more sensitive to the addition time of SP, relative to a variation in water, while for the Powder-type mix design the opposite is observed.
l Tests indicated that the limestone filler has a more significant role, compared to the presence of VMA, the type of SP and the use of silica fume and fly ash.
