PERFORMANCE BEHAVIOUR OF CONCRETE AND
MASONRY IN PAVEMENTS
C Rudman
Green Cape -Secondary Materials DiscussionCape Town28 May 2015
Background• Sustainability(environment & energy) has intensified the requirement for
waste recycling and reuse in a number of countries
• In South Africa, more than 4,725,542 tonnes of CDW were generated in
2011 but only 16% were recycled (Department of Environmental Affairs,
2012)
COMPARING THE SOUTH AFRICAN SITUATION
Surface -
Asphalt Layer
(20 - 50 mm)
Base -
Unbound high quality
crushed aggregate
(100 - 300mm)
Subbase -
Cemented mixture
(100 - 300mm)
Subgrade -
Soil fill and unbound
Mixture (Natural and
selected)
Surface - Asphalt Layer
Base - Unbound high quality crushed aggregate
Subbase - Natural Gravel
Subgrade - Soil fill and unbound mixture
Surface - Asphalt Layer
Base - Cemented baseSubbase - Cemented subbase
Subgrade - Soil fill and unbound mixture
Surface - Asphalt Layer
Base - HMA BaseSubbase - Cemented subbase
Subgrade - Soil fill and unbound mixture
ALS
O
How can we apply the
demolition waste in this
pavement?
We need:
-A level of ingenuity
-Adequate evaluation
-Develop an understanding
Ahhhh That is very
broad!!!!???
• Current empirical test emthods do
not allow for the extinguising
between good and bad materials
Reference: SAPEM,2013
Challenge 2:
Can’t just use the current specifications as set out in the pavement standards, as the tests are based on granular material experiences
1. Shear properties
0
200
400
600
800
1000
1200
1400
1600
1800
0 0.1 0.2 0.3 0.4 0.5 0.6
Strain
Stres
s (k
Pa)
σσσσ3,H
σσσσ1
Triaxial
σσσσ1,H
σσσσ1,L
σσσσ2,H
σσσσ3,H
σσσσ3,L
Vertical
Ver
tica
l
Reference: Jenkins, 2015
0200400
600800
100012001400
160018002000
0 0.1 0.2 0.3 0.4
Log Bulk Stress θθθθ = σσσσ1111 + σ + σ + σ + σ2222 + σ + σ + σ + σ3333
Res
ilien
t M
odulu
s (M
pa)
Resilient Modulus for Coarse Granular Materials
k2
1
k1
σσσσ1
σσσσ2
σσσσ3
Mr = k1θθθθk2
Reference: Jenkins, 2015
3. Permanent Deformation Triaxial Test
σσσσd/σσσσd,f = 40%
Vertical Strain εεεεv
Time or Load Reps (N)
σσσσd/σσσσd,f = 50%
σσσσd/σσσσd,f = 60%
Coarse Grained Stone – Stress Ratios Sand
Critical SR: Delft = 45 to 60%; Maree (SA) = 70% up to 90%
εεεεp = aNb
Reference: Jenkins, 2015
STEP 1: PROCESSING AND
AGGREGATE CHARACTERISTICS
STEP 2: LOADING AND
MIXING CHARACTERISTICS
STEP 3: DETERMINING MOST
INFLUENTIAL VARIABLES
STEP 4: PRACTICAL
APPLICATION OF CDW
1.Crushed
3.Reconstituted
2.Fractionized
<13.2-6.7mm
< 6.7- 4.75 mm
<4.75 – 0.425mm
< 0.075mm
Always
concrete rubble
Type 1:
70% Concrete/30% Masonry
Type 2:
30% Concrete/70% Masonry
70C : 30MComposition and
mixture
Compaction Moisture
Degree of
Compaction
30C : 70M
70% OMC 80% OMC 70% OMC 80% OMC
100% 102% 100% 102% 100% 102% 100% 102%
STEP 1: PROCESSING AND
AGGREGATE CHARACTERISTICS
STEP 2: LOADING AND
MIXING CHARACTERISTICS
STEP 3: DETERMINING MOST
INFLUENTIAL VARIABLES
STEP 4: PRACTICAL
APPLICATION OF CDW
Following processing methods used, it
was found that:
-pre-separation of rubbles before
crushing is very important for
controlling the quality of recycled
aggregates
- jaw crusher could produce cubical
aggregates
-secondary crushing reduces flaky
aggregates and increases fines in the
material
-higher flakiness index with increase
in masonry content but less than
specified in SAPEM(2013)
STEP 1: PROCESSING AND
AGGREGATE CHARACTERISTICS
STEP 2: LOADING AND
MIXING CHARACTERISTICS
STEP 3: DETERMINING MOST
INFLUENTIAL VARIABLES
STEP 4: PRACTICAL
APPLICATION OF CDW
•Higher resistance of RCM to crushing in dry conditions than in wet,
thus the ratio below the required limit in SAPEM(2013)
•Moisture softens the attached mortar and the porous masonry during
wet 10% fines crushing test
STEP 1: PROCESSING AND
AGGREGATE CHARACTERISTICS
STEP 2: LOADING AND
MIXING CHARACTERISTICS
STEP 3: DETERMINING MOST
INFLUENTIAL VARIABLES
STEP 4: PRACTICAL
APPLICATION OF CDW
Monotonic Modelling and mechanical behaviour
STEP 1: PROCESSING AND
AGGREGATE CHARACTERISTICS
STEP 2: LOADING AND
MIXING CHARACTERISTICS
STEP 3: DETERMINING MOST
INFLUENTIAL VARIABLES
STEP 4: PRACTICAL
APPLICATION OF CDW
Cohesion between
170kPa -300kPa
Maximum Cohesion
130kPa
Vs
Also lower friction AnglesReference: SAPEM (2013)
PERMANENT DEFORMATION VS NATURAL MATERIALS
CRUSHED CONCRETE
G2 LIMESTONE
Re
fere
nce
: va
n D
er
Be
rg,
20
13
Challenge 3:
Need to consider the factors governing the behaviour of the materials
Seperation, seperation, seperation
STEP 1: PROCESSING AND
AGGREGATE CHARACTERISTICS
STEP 2: LOADING AND
MIXING CHARACTERISTICS
STEP 3: DETERMINING MOST
INFLUENTIAL VARIABLES
STEP 4: PRACTICAL
APPLICATION OF CDW
Mixture and compaction moisture are predominant factors on Mr :
Ln(Mr)= 9.84 + 0.27Ln(M) – 1.12 Ln(CM)
ANOVA analysis
STEP 1: PROCESSING AND
AGGREGATE CHARACTERISTICS
STEP 2: LOADING AND
MIXING CHARACTERISTICS
STEP 3: DETERMINING MOST
INFLUENTIAL VARIABLES
STEP 4: PRACTICAL
APPLICATION OF CDW
Mixture and compaction moisture are predominant factors on Mr :
Example of seperation requirements (Reference: van Niekerk,2000)
ANOVA analysis
Conclusions
• Separation and secondary crushing for quality of recycled materials
• The failure behaviour is significantly affected by composition and degree of
compaction but less influence with compaction moisture
• The composition and compaction moisture have a relative distinctive effect
on the resilient response than the degree of compaction
• The shear strength of CDW is within range, even better to some base
natural granular materials
• CDW is a viable alternative material type to consider in the construction of
pavement layers that carry low to moderate levels of traffic
Objectives• study into use of RCA as coarse aggregate in new concrete for structural applications
– to reduce amount of C&D waste & decrease extraction of natural aggregates
– to increase database of research of RCA in South Africa
• main concern: uncertainty regarding source of material
• main obstacle: lack of South African standards / specifications / guidelines
• use of RCA well developed & legislated in Japan, China, Australia, Europe, USA & Russia
• Current SA standard: SANS 1083:2008 – aggregates from natural sources (under revision to align
with EU, not clear if RCA to be included)
• specific issues investigated at SU:
– What percentage replacement of RCA in concrete?
– What aggregate properties and limits should be defined?
Recycled Concrete Aggregate (RCA)
Wibke de Villiers - [email protected]