Mark Cordell
Global Manager, Dams & Hydropower
High quality consulting and development solutions
worldwide
Major Dams ≥60mUnder Construction in 2009
Source: 2009 World Atlas & Industry Guide
Major Dams ≥60mUnder Construction in 2009 - Worldwide- Africa
Source: 2009 World Atlas & Industry Guide
RCC Mix DesignAn Introduction and Case Study
• Introduction
• RCC and Dam Construction Today
• RCC Mix Constituents
• RCC Design Philosophies
• Options Using Various ‘Quality’ Aggregates
A Case Study
RCC Mix Constituents
Roller Compacted Concrete – RCC – is a Concrete
• Dry enough to
support vibratory
roller
• Wet enough to
permit adequate
distribution of
paste
RCC Design Philosophies
“High Paste”
• High cementitious content (typ. 180240kg/m3)
• Relatively large quantities of Pozzolan as
substitute for natural fines
• Workable material
• Low permeability
• “Premium” concrete
RCC Design Philosophies
“Low Paste”
• Low cementitious content (typ. 7090kg/m3)
• Relies on continuous dense grading envelope to
fine fraction for its density
• Lower workability
• Higher permeability
• Need for Upstream Membrane?
Location• Dak Nong
Province,Vietnam
Services• Technical Appraisal• RCC Mix Lab Tests/Trial Embankment• Construction Assistance
Main Features• 108m RCC dam• 180MW Power house• 607GWh/annum
Dong Nai 3 Hydroelectric Project, Vietnam
DONG NAI 3 HEP
Project Status
• Feasibility Studies completed in March 2000
• Design further developed by Power Engineering
Consulting Company No.2 (PECC2) with
assistance from an International Consultant Firm
• SMEC engaged to undertake Independent
Technical Appraisal of Dong Nai 3 and Dong Nai
4 RCC Dam Designs in January 2006
• SMEC’s appointment in accordance with GoV
policy for technical oversight on large RCC Dams
Project Status
Following the Independent Technical Appraisal,
SMEC were engaged to:
•Supervise the RCC Trial Mix Programme,
including the Trial Embankment
•Supervise the establishment of the Aggregate
Quarry
•Provide ongoing Construction Assistance for
Dong Nai 3 and Dong Nai 4 RCC Dams
Principal Objectives of Technical Appraisal
• Review the proposed design concept of the RCC
dams
• Review the proposed RCC dam construction
methodology
• Assess geological conditions of the dam sites
and proposed quarries
• Inspect and comment on concrete laboratory
and hydraulic modelling facilities used for design
development of the Projects
Original Design Concept for RCC Dam
• RCC mix design based on high cementitious
content 170kg/m³
(60kg/m³ cement; 110kg/m³ pozzolan)
• Metasediment aggregate source
• Central Vietnam commercial pozzolan source
relatively high transportation cost
Locally Available Aggregate Options- Metasediment Aggregate Source
Locally Available Aggregate Options- Basalt Aggregate Source
Characteristics of Basalt Quarry - Solid Basalt
Characteristics of Basalt Quarry- Vesicular Basalt
Characteristics of Basalt Quarry- Dirt Seams
Thermal Expansion and Thermal Stress
• Critical property of concrete for dams
• If stiffness (Modulus of Elasticity) and creep
similar, thermal stress and related potential for
cracking essentially proportional to coefficient of
thermal expansion
• This property of RCC dependent of aggregate
properties
Thermal Expansion and Thermal Stress
At Dong Nai 3:
• Metasediment 10.7 x 106/°C
• Basalt 4.6 x 106/°C
The Basalt aggregate offered much more
favourable thermal properties – low thermal
stresses
Unit Weight, Density and Air Voids
• Initial concern with vesicular nature was effect
the basalt aggregate would have on RCC density
• When crushed to less than 13mm, specific
gravity of the two aggregates essentially same
(≈2.72)
• Coarser aggregates had a lower specific gravity
for 2550mm particles (2.64 vs 2.76)
Unit Weight, Density and Air Voids
• However, the coarse aggregates only
represented 20% of total aggregate – impact on
the overall density not significant
• The vesicular basalt exhibited greater
absorption, but the mix proportions were based
on saturated aggregates, so essentially no effect
Gradation
• Initial gradation of aggregates adjusted to be
consistent with efficient RCC mixes (greater
strength per kg of cementitious material)
• Better mixability
• Less segregation for mixes of same cementitious
content
• Less void space in compacted aggregates
• Less need for cement and pozzolan to fill void
space
0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
1 0 0
0 .0 1 0 .1 0 1 .0 0 1 0 .0 0 1 0 0 .0 0
S ize (m m )
% P
assi
ng
In it ia l M e ts S a nd s ton e La b M ix G r ad a t io n
S M E C M ix e d B as a lt La b M ix G r ad a tio n
S M E C B as a lt A t In ita l La b M ix G r ad a tio n
Comprehensive Mix Design Studies
• Many mixes assessed varying cement and
pozzolan contents, including mixes with no
pozzolan
• Control mixes – ‘initial’ gradation
• Most mixes used improved gradation
• Base mixes used ‘mixed basalt’ – 70% solid
basalt; 25% vesicular basalt; 5% dirty material
• 100% crushed vesicular basalt mix made for
comparison
Compressive Strength Development [MPa]
0
5
10
15
20
25
30
35
40
1 10 100 1000
Co
mp
res
siv
e S
tre
ng
th (M
Pa
)
Age (Days)
170-65-4.2 (7) 1x (SMEC Gradation - Metasediment) VB1=11 Sec170-65-4.2 (4) 1x (Initial Gradation-Metasediment) VB1= 23 Sec170-65-4.2 (8) 1x (SMEC Mixed Basalt) VB1=15 Sec
Cementitious Content (kg/m3)-% Pozzolan-% Moisture Content (% Fines) Admix Dose
Accelerated Cure
Accelerated Cure
Basalt vs Metasediment – No Pozzolan
0
5
10
15
20
25
30
35
40
1 10 100 1000
Co
mp
res
siv
e S
tre
ng
th (M
Pa
)
Age (Days)
90-0-4.2 (8) 1x : VB1=15 Sec, Mixed Basalt
90-0-4.2 (7) 1x : VB1=15 Sec, Metasediment
Cementitious Content (kg/m3)-% Pozzolan-% Moisture Content (% Fines) Admix Dose
SMEC Gradation
Effectiveness of Pozzolan vs Aggregate Fines
0
5
10
15
20
25
30
35
40
1 10 100 1000
Co
mp
ress
ive
Str
eng
th (M
Pa)
Age (Days)
60-0-4.2 (8) 1x : VB1=12 Sec
120-0-4.2 (8) 1x : VB1=18 Sec
120-50-4.2 (8) 1x : VB1=13 Sec
170-65-4.2 (8) 1x: VB1=15 Sec
Cementitious Content (kg/m3)-% Pozzolan-% Moisture Content (% Fines) Admix Dose
60 kg Cement + 60 kg Cement
60 kg Cement + 60 kg Pozz
60 kg Cement + 00 kg Pozz
60 kg Cement + 110 kg Pozz
SMEC Mixed BasaltSIKA TM 25 Admix
Accelerated Cure
Effect of Dirty Material on Strength
0
5
10
15
20
25
30
35
40
1 10 100 1000
Co
mp
ress
ive
Str
eng
th (M
Pa)
Age (Days)
90-0-4.2 (8) 1x : VB1=15 Sec, 5% Dirty Basalt90-0-4.2 (8) 1x : VB1=15 Sec, No Dirty Basalt
Cementitious Content (kg/m3)-% Pozzolan-% Moisture Content (% Fines) Admix Dose
RCC Trial Embankment
RCC Trial Embankment
Mix 110 + 60 (Basalt)
Mix 75 + 00 (Basalt)Mix 90 + 00 (Basalt)
Dong Nai 3 RCC Dam - Nearing Completion
Thank You
Mark CordellGlobal Manager, Dams & [email protected]
High quality consulting and development
solutions worldwide www.smec.com