Green Cape 28 May · Green Cape -Secondary Materials Discussion Cape Town 28 May 2015. ... • Current empirical test emthodsdo ... -higher flakiness index with increase

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)

RCA and RCM for roads: NETHERLANDS/EUROPE SITUATION

Reference: Araya, 2011

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


Base - Cemented baseSubbase - Cemented subbase



Base - HMA BaseSubbase - Cemented subbase


ALS

O

Challenge 1:

Can’t just copy the research done by other countries

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


3. Permanent Deformation Triaxial Test

σσσσd/σσσσd,f = 40%

Vertical Strain εεεεv

Time or Load Reps (N)



Coarse Grained Stone – Stress Ratios Sand

Critical SR: Delft = 45 to 60%; Maree (SA) = 70% up to 90%

εεεεp = aNb


Not all doom and gloom,

Example of current studies

(a) Shear behaviour

(b) Dynamic behaviour

Step1 Step 2

Step 3: ANOVA

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 2: LOADING AND




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 2: LOADING AND




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 2: LOADING AND




STEP 4: PRACTICAL

APPLICATION OF CDW

Monotonic Modelling and mechanical behaviour



STEP 2: LOADING AND




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 2: LOADING AND




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 2: LOADING AND




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]

Thank you

Any questions?

Green Cape 28 May · Green Cape -Secondary Materials Discussion Cape Town 28 May 2015. ... • Current empirical test emthodsdo ... -higher flakiness index with increase

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