the influence of cement paste volume in mortar on the rheological effects of the addition of...
TRANSCRIPT
The influence of cement paste volume
in mortar on the rheological effects
of the addition of superplasticizer
Jacek GołaszewskiSilesian University of Technology
Introduction The effects of SP on rheology of cement
mixtures depend on cement and SP properties, SP content, time of SP addition, and on w/c.
The relations of influence of SP on rheological properties of cement mixtures not always are unequivocal.
Ambiguous effects of SP may be caused by different cement paste content in cement mixtures
Introduction
The main objective of investigation was to explore the influence of SP content on the rheological parameters of different in cement paste volume fresh mortars.
Testing program
Factor m/p
1.89
1.24
2.52
3.77
SP content
1, 1.5, 2, 2.5
0.5, 1, 1,5, 2, 2.5
0.5, 1, 1,5, 2
2, 2.5, 3, 3.5
m/p - factor of uncompacted sand filling by cement paste.
w/c
0.35
Testing program
Factor m/p
2.22 – 2.48
1.46 – 1.64
2.85 – 3.30
4.28 – 4.78
w/c
0.47, 0.50, 0.53, 0.56
m/p - factor of uncompacted sand filling by cement paste.
0.50, 0.53, 0.56
0.44, 0.47, 0.50, 0.53
0.44, 0.47, 0.50, 0.53
Fresh cement mixtures exhibit the Bingham viscoplastic behaviour
- shear stress - shear rate o - yield value
pl - plastic viscosity
Testing method
.
γηττ plo
oτ τ
γ
plη
1
Viskomat PC rheometer T = g + N h
g – parameter corresponding to yield value h – parameter corresponding to plastic viscosityM – shear resistanceN – rotation rate
Start of measurement - speed 120 rev/min held for 3 min. Measurement of T at N = 120-100-80-60-40-30-20 1/min.
Testing method
Influence of m/p and SP content on yield value g
0
20
40
60
80
100
120
0 1 2 3 4SP content, %
g,
N m
m..
...
1.24
1.89
2.52
3.77
after 60 min
0
20
40
60
80
100
120
0 1 2 3 4SP content, %
g,
N m
m..
...
1.24
1.89
2.52
3.77
after 60 min
0
20
40
60
80
100
120
0 1 2 3 4SP content, %
g,
N m
m..
...
1.24
1.89
2.52
3.77
after 10 min
0
20
40
60
80
100
120
0 1 2 3 4SP content, %
g,
N m
m..
...
1.24
1.89
2.52
3.77
after 10 min
Influence of m/p and SP content on plastic viscosity h
0
10
20
30
40
50
60
0 1 2 3 4SP content, %
h,
N m
m s
....
.
1.24
1.89
2.52
3.77
after 10 min
0
10
20
30
40
50
60
0 1 2 3 4SP content, %
h,
N m
m s
....
.
1.24
1.89
2.52
3.77
after 10 min
0
10
20
30
40
50
60
0 1 2 3 4SP content, %
h,
N m
m s
....
.
1.24
1.89
2.52
3.77
after 60 min
0
10
20
30
40
50
60
0 1 2 3 4SP content, %
h,
N m
m s
....
.
1.24
1.89
2.52
3.77
after 60 min
Mathematical relations of influence of SP content on g & h
g = Ag SP Bg
where: SP - superplasticizer content; Ag, Bg, Ah, Bh, Ch - material constants depending mainly of cement paste volume in mortar and sand graining (factor m/p), of properties of cement and SP, and of time.
h = Ah SP2 + Bh SP + Ch
0
20
40
60
80
100
120
0 1 2 3 4SP content, %
g,
N m
m..
...
1.24
1.89
2.52
3.77
0
20
40
60
80
100
120
0 1 2 3 4SP content, %
g,
N m
m..
...
1.24
1.89
2.52
3.77
0
10
20
30
40
50
60
0 1 2 3 4SP content, %
h,
N m
m s
....
.
1.24
1.89
2.52
3.77
after 10
0
10
20
30
40
50
60
0 1 2 3 4SP content, %
h,
N m
m s
....
.
1.24
1.89
2.52
3.77
after 10
Influence of m/p and w/con g & h
0
20
40
60
80
100
120
0,41 0,47 0,53 0,59w/c
g,
N m
m..
...
1.53 - 1.68
2.22 - 2.48
2.85 - 3.30
4.28 - 4.78
after 10 min
0
20
40
60
80
100
120
0,41 0,47 0,53 0,59w/c
g,
N m
m..
...
1.53 - 1.68
2.22 - 2.48
2.85 - 3.30
4.28 - 4.78
after 10 min
0
10
20
30
40
50
60
0,41 0,47 0,53 0,59w/c
h,
N m
m s
....
.
1.46 - 1.68
2.22 - 2.48
2.85 - 3.304.28 - 4.78
after 10 min
0
10
20
30
40
50
60
0,41 0,47 0,53 0,59w/c
h,
N m
m s
....
.
1.46 - 1.68
2.22 - 2.48
2.85 - 3.304.28 - 4.78
after 10 min
Influence of m/p and w/con g & h
0
10
20
30
40
50
60
0,41 0,47 0,53 0,59w/c
h,
N m
m s
....
.
1.46 - 1.68
2.22 - 2.48
2.85 - 3.304.28 - 4.78
after 60 min
0
10
20
30
40
50
60
0,41 0,47 0,53 0,59w/c
h,
N m
m s
....
.
1.46 - 1.68
2.22 - 2.48
2.85 - 3.304.28 - 4.78
after 60 min
0
20
40
60
80
100
120
0,41 0,47 0,53 0,59w/c
g,
N m
m..
...
1.46 - 1.68
2.22 - 2.48
2.85 - 3.30
4.28 - 4.78
after 60 min
0
20
40
60
80
100
120
0,41 0,47 0,53 0,59w/c
g,
N m
m..
...
1.46 - 1.68
2.22 - 2.48
2.85 - 3.30
4.28 - 4.78
after 60 min
0
20
40
60
80
100
120
0 1 2 3 4SP content, %
g,
N m
m..
...
1.24
1.89
2.52
3.77
after 10 min
0
20
40
60
80
100
120
0 1 2 3 4SP content, %
g,
N m
m..
...
1.24
1.89
2.52
3.77
after 10 min
0
10
20
30
40
50
60
0 1 2 3 4SP content, %
h,
N m
m s
....
.
1.24
1.89
2.52
3.77
after 10 min
0
10
20
30
40
50
60
0 1 2 3 4SP content, %
h,
N m
m s
....
.
1.24
1.89
2.52
3.77
after 10 min
Effect of SP content
0
20
40
60
80
100
120
0,41 0,47 0,53 0,59w/c
g,
N m
m..
...
1.53 - 1.68
2.22 - 2.48
2.85 - 3.30
4.28 - 4.78
after 10 min
0
20
40
60
80
100
120
0,41 0,47 0,53 0,59w/c
g,
N m
m..
...
1.53 - 1.68
2.22 - 2.48
2.85 - 3.30
4.28 - 4.78
after 10 min
0
10
20
30
40
50
60
0,41 0,47 0,53 0,59w/c
h,
N m
m s
....
.
1.46 - 1.68
2.22 - 2.48
2.85 - 3.304.28 - 4.78
after 10 min
0
10
20
30
40
50
60
0,41 0,47 0,53 0,59w/c
h,
N m
m s
....
.
1.46 - 1.68
2.22 - 2.48
2.85 - 3.304.28 - 4.78
after 10 min
Effect of w/c
Influence of m/p , w/c and SPon g & h – comparison of results
Conclusions
Effects of superplasticizer addition on rheology of fresh mortar and concrete should be considered in respect to cement paste volume.
It is difficult to unequivocally predict effects of superplasticizer on rheology of mortar or fresh concrete and its changes with time basing on tests made on cement paste.
Conclusions
The influence of increasing superplasticizer content and increasing w/c on yield value of mortars is similar.
In the same time such influence on plastic viscosity may be distinctly different.
It is difficult to set out such composition of mortars without and with superplasticizer that for similar yield value will be characterised by the same plastic viscosity.