aug13 (1).pdf

August 2013 MCI (P) 051/02/2013
The Magazine Of
The Institution Of Engineers, Singapore
www.ies.org.sg
SINGAPORE ENGINEER
SINGAPORE ENGINEER
SINGAPORE ENGINEER
SINGAPORE ENGINEER
COVER STORY:
CIVIL & STRUCTURAL ENGINEERING
Mount Elizabeth Novena Hospital
FEATURES:
Civil & Structural Engineering • ConcreteTechnology • Project Application
THE
SINGAPORE ENGINEER

01
August 2013 THE SINGAPORE ENGINEER
FEATURES
08 CIVIL & STRUCTURAL ENGINEERING: COVER STORY:
The project received recognition for design and engineering safety excellence.
14 CIVIL & STRUCTURAL ENGINEERING:
Campus for Research Excellence andTechnological Enterprise
The multi-award-winning project features design innovations to meet general and
special requirements.
17 CONCRETETECHNOLOGY:
Self-healing material concepts as solution for ageing infrastructure
Besides the material’s inherent capability, crack-bridging can also be achieved through
the use of micro-organisms and nanoparticles.
28 PROJECT APPLICATION:
WR 250 cold recycler and soil stabiliser in factory expansion project
The Wirtgen machine demonstrated its qualities.
38 HEALTH & SAFETY ENGINEERING:
Safety experts call for a ‘radical rethink’
An IOSH conference in Hong Kong highlighted the need to reduce construction-
related accidents.
38 HEALTH & SAFETY ENGINEERING:
Singapore students win awards
Organised by IOSH, the competition seeks to reward creativity in the promotion of
safe practices.
REGULAR SECTIONS
02 IES UPDATE
30 PRODUCTS & SOLUTIONS
40 EVENTS
42 NEWS
CONTENTS
Chief Editor
T Bhaskaran
t_b_n8@yahoo.com
Director, Marketing
Roland Ang
roland@iesnet.org.sg
Marketing & Publications Executive
Jeremy Chia
jeremy@iesnet.org.sg
CEO
Angie Ng
angie@iesnet.org.sg
Publications Manager
DesmondTeo
desmond@iesnet.org.sg
Published by
The Institution of Engineers, Singapore
70 BukitTinggi Road
Singapore 289758
Tel: 6469 5000 Fax: 6467 1108
Cover designed by Irin Kuah
Cover image by Penta-Ocean
Construction Co Ltd.
The Singapore Engineer is published
monthly by The Institution of Engineers,
Singapore (IES). The publication is
distributed free-of-charge to IES members
and affiliates. Views expressed in this
publication do not necessarily reflect those
of the Editor or IES.All rights reserved. No
part of this magazine shall be reproduced,
mechanically or electronically, without the
prior consent of IES. Whilst every care is
taken to ensure accuracy of the content
at press time, IES will not be liable for any
discrepancies. Unsolicited contributions
are welcome but their inclusion in the
magazine is at the discretion of the Editor.
Design & layout by 2EZ Asia Pte Ltd
Printed by Print & Print Pte Ltd.

02 THE SINGAPORE ENGINEER August 2013
Message from the
Chairman, Civil & Structural
Engineering TC
IES COUNCIL MEMBERS
2012/2013
President
Prof Chou Siaw Kiang
Deputy President
Er. Chong Kee Sen
Vice Presidents
Er. Koh BengThong
Dr Kwok Wai Onn, Richard
Mr Neo Kok Beng
Er. Ong Geok Soo
Er. Ong See Ho
Honorary Secretary
Dr Boh Jaw Woei
Honorary Treasurer
Er. Seow Kang Seng
Assistant Honorary Secretary
Mr Kang Choon Seng
Assistant Honorary Treasurer
Er.Tan Shu Min, Emily
Immediate Past President
Er. Ho Siong Hin
Past Presidents
Er. Dr Lee Bee Wah
Er.Tan Seng Chuan
Honorary Council Member
Er. Ong Ser Huan
Council Members
Prof Chau Fook Siong
Er. Dr Chew Soon Hoe
Mr Joseph William Eades
Prof Er Meng Joo
Ms Fam Meiling
Er. Dr Ho Kwong Meng
Dr HoTeckTuak
Er. Edwin Khew
Mr Lee Kwok Weng
Mr Oh Boon Chye, Jason
Mr So Man Fung, David
Er. SeowTiang Keng
Er.Teo Chor Kok
Er.Toh Siaw Hui, Joseph
Er.Wong Fee Min,Alfred
Dr ZhouYi
IES UPDATE
With the tightening of the foreign labour quotas,
companies in the building and construction industry
are compelled to adopt new approaches to continue
functioning effectively and fulfil their contractual
obligations. They will have to increase productivity
with the available manpower.
Among the methods to raise productivity are the increased application of Information
Technology, particularly the adoption of Building Information Modelling (BIM);
increased application of more buildable designs; as well as the use of more high
performance construction equipment such as tower cranes, material and passenger
hoists, concrete pumps, system formwork etc, to perform a variety of tasks. Further,
the use of new materials such as high-strength concrete and high strength structural
steel etc, the adoption of technologies such as. robotics, and increasing the extent
of prefabrication in an automated factory environment, can shorten construction
times and thereby reduce the requirement of man-hours, especially on site, whilst
also improving quality.
However, the specification of new materials brings with it the challenge of having
to evaluate their performance over the lifecycle of structures, particularly in terms
of maintenance requirements and durability, whereas traditional materials have
established track-records.
With the introduction of new machines comes the need to acquire the knowledge
to operate them, as well as an understanding of their maintenance and servicing
requirements.
At the same time, new materials, equipment and technologies may have to be
adapted to suit the local environment and practices.
All this means that there will be a need for engineers and other personnel working
in the building and construction industry to acquire relevant know-how through
training courses, workshops and other means.
Engineers and scientists would also have to engage in research & development and
innovation, to develop appropriate local solutions to meet the requirements of a
fast-changing and increasingly complex industry, as it undertakes its next phase of
development characterised by greater output with less manpower.
Er. Dr Ho Kwong Meng
Chairman, Civil & Structural EngineeringTechnical Committee

IES UPDATE
Several of our IES Committees are looking for new blood to join
their ranks.They are the IES Publications Committee, IES Public
Relations Committee and IES Women in Science, Engineering &
Research (WiSER).
The IES Publications Committee is in charge of overseeing all of
the publications that IES publishes, from the monthly Singapore
Engineer magazine to the IES Engineering Directory and even
the IES Journal. If you wish to make a difference in shaping the
published material produced by IES then you are the person the
Publications Commmitte is looking for.
The Publications Committee has 6 sub-committees that look
after different aspects of publishing:
1) IES Engineering Directory Sub-Com
2)The Singapore Engineer Sub-Com
3) Who’s Who in Engineering Singapore Sub-Com
4) IES Journal Sub-Com
5) Web Publishing Sub-Com
6) General Publications Sub-Com
You shall be assigned to one of these sub-committees upon
your acceptance into the Publications Committee. Please email
publications@iesnet.org.sg for more information.
The IES Public Relations Committee is welcoming volunteers
who wish to contribute to the promotion of IES and the field of
engineering in Singapore through the media.
If you are full of ideas and have a passion for building up the
image of engineers, please email publications@iesnet.org.sg
The IES Women in Science, Engineering & Research (WiSER)
is looking for woman engineers to join their ranks.The WiSER
Committee is dedicated to enhance awareness of equal
opportunities for woman engineers, to represent the interest
of women engineers and to inspire girls to enter the fields of
science, engineering, research and the built environment, as well
as to increase the retention rate of women engineers.
You shall be assigned to the sub-committees upon your
acceptance into WiSER. For those who are interested, please
email to leon@iesnet.org.sg
IES appeals for donations to the Building Fund
The collection for the IES Building Fund presently stands at S$ 2.4 million.This includes the S$ 600,000 from members and
members’ organisations, S$ 110,000 from the fund-raising golf tournament, and a generous donation of S$ 1.3 million from
the estate of the late Er. Charles Rudd.
As the saying goes, ‘Charity begins at home’, and no amount is too small to make a difference. We are currently S$ 2.5
million away from our target of S$ 4.9 million and we very much appreciate any donations that our members can make.
We would also appreciate members passing on the word to encourage fellow members to donate and to approach friends
and associates to seek out corporates who are donors to a good cause.
Please act now and contribute in any way possible to help realise this landmark project. For more information on donations,
please contact siewkeow@iesnet.org.sg
Calling all Volunteers!
The new annexe to the IES Building will cater to the growth in IES membership and activities.

COVER STORY
THE PROJECT
Located at Novena Medical Hub, near Novena MRT Station and
within part of the second reserved zone of the Novena MRT
tunnels of the North South Line, the hospital comprises:
• A 14-storey In-patient block.
• Ten storeys of D &T medical facilities with a two-level basement.
• Eight levels of Medical Consulting Suites above a six-level car
park block.
SITE CONSTRAINTS
The site is partly located within the second reserve zone of the
Novena MRT tunnels along Irrawaddy Road.The undulating site
terrain along Irrawaddy Road varied from Level 103.5 to 118.6.
Substantial earthworks for site formation was necessary before
commencement of piling work and basement construction.
The existing ground levels at the west boundary, where a 1.8
m wide box drain within the 3.4 m wide drainage reserve was
proposed, were 3 m to 6 m below a row of terrace houses.The
AWinner of the BCA Design and Engineering Safety ExcellenceAward,under the Institutional
& Industrial Category, at BCA AWARDS 2013, the project was commended by the
assessment committee for the awards, for adopting highly efficient engineering approaches
to meet architectural and functional requirements, while enhancing productivity, site safety
and quality. By adopting innovative design solutions to overcome site challenges, the project
was completed on time despite tight schedules.
Mount Elizabeth Novena Hospital has an In-patient block, D&T medical facilities and medical consulting suites.
The hospital is located near the Novena MRT station and within part of the
reserved zone of the Novena MRT tunnels.

COVER STORY
09
rubble and brick retaining walls were generally in a dilapidated
condition.
As indicated in the URA Land Sale conditions, the existing
V-drain was required to be diverted to the drainage reserve as
shown in the site plan and Irrawaddy Road was to be widened
GEOLOGICAL INVESTIGATION
OF SITE
In anticipating undulating rock of the Bukit Timah Formation,
extensive soil investigation was conducted to map out the rock
contours and highly weathered rock with SPT values greater
than 100 for the entire site.
In addition to four bore-logs provided in the URA Land Sale
document, a total of 20 bore holes were made.
The required pile design depths and socket lengths over the
entire site could be predicted more accurately with the rock
contours given.
FORWARD CONTRACT -
DRAINAGE DIVERSION
To minimise the excavation in close proximity to the adjoining
properties, the alignment and invert levels of the box culvert
drain were carefully adjusted higher,taking into consideration the
existing site levels and the dilapidated condition of the existing
retaining wall along the west boundary of the site. In general, a
new box culvert drain was constructed on the existing ground
levels, and excavation next to the high retaining wall at the west
boundary was avoided.
FORWARD CONTRACT -
EARTHWORKS AND PILING
WORKS
To facilitate the piling work, the earthworks and site formation
contract was carried out initially in the forward contract. The
installation of foundation piles and contiguous bored piles
commenced after the successful completion of two of the
instrumented ultimate load tests.
A total of 252 foundation bored piles and 135 contiguous bored
piles were installed. Large diameter bored piles, up to 2.2 m
in diameter with plunge-in steel columns, were designed to
facilitate the top-down method of basement construction, To
socket the foundation piles into fresh rock stratum, so as to
mobilise adequate skin friction and end-bearing, a BG 35 boring
machine was specified in the contract.
The site plan.
Estimated contours showing surface elevation of rock.
A new box culvert drain was constructed on the existing ground levels

COVER STORY
Considering the presence of steep bedrock, as marked on
the rock contours plan, and the design capacities of the large
diameter single bored piles that were required to sustain the
column loads for top-down construction, the following criteria
were set, to determine pile depth and socket length into the
fresh rock stratum:
PILE DESIGN CRITERIA
Qa = (Qs + Qb) / 2.5
Qa = Qs/1.5 + Qb/3
Factor of safety for shaft friction alone ≥ 1.5
PILE DESIGN PARAMETERS
Ultimate Shaft Friction (fs)
2N≤ 150kN/m2
for Layer 1 to 7B (N<100)
150 kN/m2
for Layer 8 & 9A whereTCR< 50%
300 kN/m2
for Layer 9 where RQD <30%
400 - 600 kN/m2
for Layer 9 where RQD ≥30%
Ultimate Base Resistance (fb)
75N≤ 7500 kN/m2
for Layer 8
7500 kN/m2
for Layer 9 whereTCQ <50%
9000 kN/m2
for Layer 9 where RQD<30%
12000 kN/m2
for Layer 9 where RQD≥30%
INSTRUMENTED ULTIMATE LOAD TESTS FOR
PILE DESIGN
To ascertain the soil parameters for pile design, instrumented
ultimate load tests were conducted at two locations.To minimise
stacking height and maximise safety during the tests, steel plates
were used to set up the load tests.
A total of 252 foundation bored piles and 135 contiguous bored piles were installed.
Instrumented ultimate load tests were conducted at two locations.
The condition of the retaining walls of adjoining properties before and after the
box drain was constructed within the 3.4 m wide drainage reserve.
Before After
Before After
Before After

COVER STORY
11
MONITORING INSTRUMENTS
In addition to performing real-time monitoring within MRT
tunnels, eight clusters of monitoring instruments were
installed at extensive ground settlement points at the site,
by the independent specialist builder, to monitor the ground
movements, prior to commencement of earthworks and
piling works.
ASSESSMENT OF STRESS
EFFECTS ON MRT TUNNELS
In compliance with the requirements on protection of the
MRT during construction, the assessment of stress effects due
to excavation and piling work was carried out as required by
the Land Transport Authority (LTA).
The results indicated that the stresses induced were within
the allowable limit of 15 kN/m2,
as specified by LTA. Real-
time monitoring instruments were set in the north and south
bounds of the tunnels. The MRT tunnels were found to be
safe and the track alignments were not affected during piling
and basement construction.
TOP-DOWN BASEMENT
CONSTRUCTION
Design provision for the top-down method for basement
construction was made in the foundation design. Plunge-in
steel columns were provided in the piling design.The sequence
for basement excavation and construction was clearly shown
in the main contract drawings. The top-down construction
method allowed the basement structure to be constructed
simultaneously with the superstructure.The method eliminated
extensive strutting systems and provided better control of
ground movement during basement construction.
Monitoring instruments were installed extensively at ground settlement points
at the site
Stress changes at Point ‘B’ (north bound tunnel) due to surcharges of piling
equipment.
Method of assessment of stress effects on MRT tunnels.
Typical stress analysis model.
The top-down method was adopted for basement construction.

COVER STORY
STRUCTURAL SYSTEM
The primary considerations in the selection of the structural
systems for this healthcare project were the structural stiffness
required for the operation of various types of sensitive medical
equipment, robustness of the building in order to resist
accidental loads, and ease of construction. Special consideration
was given to achieving high buildability scores despite stringent
requirements imposed by the medical planner.
Composite columns and core walls were designed with encased
steel sections to enhance structural robustness, in order to
prevent disproportionate collapse under accidental loads.
UNDERGROUND TANKS
Special underground RC tanks are located under the fire engine
accessway next the boundary.They include:
• Fuel tanks
• Radioactive decaying plant
• Disinfectant dosing plant
• Decontamination holding tank
• Decay tank bunker
• Grease separator tank
• Rainwater collection tank
To mitigate the effect of the excavation work on the
surroundings, these tanks were isolated and kept away from the
existing retaining wall, as far as possible.
TRANSFER STRUCTURE
The columns, staircases and lift cores are essential vertical
members of the building structure in resisting lateral loads.These
key structural elements were extended down to the foundation
except for a column at the corner of the in-patient block, which
had to transfer at the 6th
storey, in order to provide ambulance
access to the A&E Department.
A set of steel transfer trusses was provided between the 5th
and
6th
storeys.The encased steel trusses were specifically designed
to enhance the structural robustness of the in-patient block.
A safe working platform was first erected, at the 5th
storey, by
the steel fabricator, to facilitate installation of the steel transfer
trusses which are 22 m above the ground level.
STRUCTURAL DESIGN APPROACH
CRITICAL INFRASTRUCTURE
The consultant team worked closely with the security consultant
to develop the structural systems that meet the requirements
on building robustness to prevent disproportionate collapse and
thereby enhance building security.
KEY INSTALLATIONS
The hospital planner and consultant team worked closely on the
structural requirements for the performance of vital facilities in
the hospital.
In the project, specific consideration was given to aspects such
as delivery path of medical equipment, structural stiffness for
stringent vibration control, and radiation shielding.
MEDICAL EQUIPMENT LOADS AND
DELIVERY PATH
To faciltate safe delivery and replacement of heavy medical
equipment,as and when required,the designated delivery path was
structurally strengthened for a superimposed load of 10 kN/m2
.
MANAGEMENT OF DESIGN
AND CONSTRUCTION
Mount Elizabeth Novena Hospital was a fast-track project
completed in 23 months.To complete the project with a total
GFA of 73,797 m2
, on time and within budget, the consultant
team was required to carry out thorough project planning,
Erection of staging for transfer structure.
Completion of transfer structure.
The structural system selected is characterised by structural stiffness and
robustness and it contributed to ease of construction.

COVER STORY
13
design coordination and review of construction methodology,
to ensure engineering safety during project implementation.
CONCEPTUAL/PRELIMINARY DESIGN STAGE
• Carrying out thorough soil investigation and geotechnical analysis
• Exploring and developing feasible and safe foundation and
structural options
• Working closely with the consultant team and provide C&S inputs
DESIGN DEVELOPMENT STAGE
• Mobilising a competent design team with relevant design experience
• Reviewing design and engineering safety at each stage of design
development
• Conducting peer review and internal design audit
• Using the latest advanced design software for geotechnical and
structural analysis
TENDER AND CONSTRUCTION STAGE
• Participating in technical evaluations on the proposed
construction methodology
• Reviewing construction methodology with safety in mind
• Reviewing and approving shop drawings on time for construction
• Providing timely response to all RFIs raised by the builder
CONCLUSION
• Site constraints can be overcome through innovative design
approaches.
• Adopting modular designs can contribute to ease of
construction and flexibility in layout changes.
• Avoiding deep basement options and heavy transfer
structures, if possible, optimises the structural design without
compromising the functional requirements.
• Working closely with acoustic and security consultants helps
to achieve efficient engineering solutions.
• An efficient and cost-effective structural system is essential for
timely completion of the structural works.
• In-depth design thoughts and efforts are essential in
overcoming various challenges to achieve safety and excellence
in engineering design.
Project Main Contract:Awarded on 27 May 2010.
Project Completion:TOP obtained on 23 April 2012.
Vibration control.
• Radiotherapy areas
Incorporating radiation shielding requirements including lead
lining shielding for partitions in specific rooms.
• Location of medical equipment and operation theatres
Medical equipment for MRI, CT SCAN etc, as well as operation
theatres, are located in areas with good vibration control.
• Vibration control criteria
Qualified Person
Er. DrTan Guan
C&S Consultant
T.Y.Lin International Pte Ltd
Builder
Penta-Ocean Construction Co Ltd
Developer
Parkway Novena Pte Ltd
Parkway Irrawaddy Pte Ltd
Architectural Consultant
Consultants Incorporated Architects + Planners

Developed by the National Research Foundation,Prime Minister’s
Office, Singapore, the Campus for Research Excellence and
Technological Enterprise (CREATE) comprises a 16-storey tower
block and three bar blocks,that facilitate the work and interactions
of multicultural and multidisciplinary teams of researchers.
CREATE won a BCA Green Mark Platinum Award, under the
New Non-Residential Buildings Category, at BCA AWARDS
2011, as well as a BCA Construction Excellence Award, under
the Institutional Buildings Category, at BCA AWARDS 2013.
DESIGN
Flexible conﬁguration
The campus was designed by Perkins+Will as a ‘warm’ core
and shell, comprising primarily wet and dry labs, and office
and retail spaces. Core and shell research facilities with
multiple tenants presented a unique challenge to the design
team which was entrusted with developing the design criteria
to cover a range of laboratory programmes and provide
sustainable solutions.
To provide a flexible building configuration, areas were zoned
within the facility, according to usage types and ventilation
requirements, such that wet laboratories are located in the
low-rise wings, while the dry ones and offices are in the
high-rise tower.
In reducing their energy loads, the laboratories were installed
with efficient turn down and variable speed fans as well,
thus allowing exhaust volumes to modulate according to
user needs.
Sensitive vibration criteria
To meet the vibration criteria of 4000 micro-inch per second
(mis), as stipulated by the Guideline on Laboratory room
adjacency compatibility, rib slabs, spaced 1.6 m apart, are
used, to provide adequate stiffness to the floor structures.
These rib slabs are, in turn, supported onto primary beams
before transferring loads to the columns. The configuration
of the rib slabs was standardised to span 13 m with a
2 m cantilever.
Campus for Research Excellence and
Technological Enterprise
The award-winning research complex opened its doors at the National University of
Singapore’s new University Town, in November 2012.
CREATE facilitates research and the interaction of multicultural and multidisciplinary teams of researchers.

15
Use of precast structures
As the timeline of the project was tight, full precast structures
were specified, including the rib slab as a single tee beam,
the primary girdles (beams) and the columns. The tee beams
were placed on the precast girdles, leaving an opening on both
sides of the rib slab for services to pass through.This method
of construction encouraged offsite fabrication, as there were
limited areas for storage, and minimised temporary supports
below the construction floor, thus speeding up the construction
floor cycle. It also provided a solution to run services from the
centrally cooled system or chilled beams.High strength concrete
of up to Grade 80 was specified as the columns were limited to
1 m in width throughout the full building height and the vertical
loads are substantial. Standardisation of the structural elements
was possible, thus making them ideal for precast construction.
Compact structural system for piping and ductwork
The initial design of CREATE specified a 5.5 m floor-to-floor
height in both the tower and bar buildings. Under this scheme,
2.7 m of each floor was reserved for laboratory service. To
enhance performance and optimise the use of programme
space,the structural consultant implemented a structural system
that would accommodate the laboratories’ piping and ductwork.
This enabled the space required for laboratory services to be
reduced down to 2.25 m for most of the floors - resulting in a
reduction of 0.5 metre from every floor of all three bar buildings
and from 15 of the tower’s 17 storeys,and a significant reduction
in total project cost.
Use of BIM
The implementation of Building Information Modelling (BIM),
at concept and scheme stages, ensured that any changes to
the project design, particularly to laboratory planning, were
well-coordinated.
At the scheme stage, BIM was used to rectify any discrepancies
between civil & structural, and mechanical & electrical design
work by simulating the construction sequence.This eliminated
many of the problems that could potentially arise on site.
Synergistic collaboration for a better solution
It was important to include a reasonable degree of acoustic
treatment in the base build design as constraints on space would
mean that there would not be enough space to include all the
noise control treatments necessary within the fit-out package.
In many cases, the most appropriate noise and vibration control
treatments had to be installed ‘at source’ (ie within the plant or
on the roof immediately adjoining the plant).
The canopy, an iconic feature of CREATE, underwent extensive
thermal and wind comfort studies so that it could be naturally
ventilated as much as possible. In accommodating the special
lighting and rainwater collection system which was also housed
by the canopy, the team of structural engineers studied various
options before arriving at an optimum number of columns
that would be required to support the canopy. By doing so, it
was possible to maintain the architectural intent of the feature
as well.
The canopy is an iconic feature that modifies the microclimate to enhance comfort.

Inspection and maintenance of building elements
With the use of a safety line, the canopy is easily accessible from
the roof and therefore maintenance is made easy. To suspend
the first-storey planters, a double-slab system was adopted such
that internal drainage is provided and minimal maintenance is
required.
Special design provisions
The design looked at noise from the external plant which could
affect other areas of the development (ie by being transferred
into the building via the façade). It also looked at the potential
for noise to affect other buildings outside the development and
cause a nuisance.
The design also looked at noise as a relative issue in that the
existing level of noise on the site from traffic,for example,would
influence how much plant noise is audible.The proposed noise
control treatments to the plant would result in acceptable noise
levels at the nearest buildings outside the site, meeting both the
absolute limit in the Singapore guidance and the relative limit
used in other countries.
To foster collaboration and a sense of community, the campus
includes a public garden, and an entire floor of restaurants,
cafeterias, and common spaces. These amenities are housed
within the vicinity of the plaza which connects all four buildings
and serves as an informal interactive space.
CONSTRUCTION
Design management
CREATE sits on a site with a sloping terrain and at the time
of construction, was surrounded by similar activities, and had a
limited construction staging area.
To avoid obstructing construction works on the adjacent
graduate residence and bridge, retaining walls were used with
temporary tie beams and ground anchors on two sides of the
8 m-deep basement.
Secant pile walls were also specified to minimise water seepage
through the basement wall as the water table is high due to
the terrain. Doing so enabled more efficient construction of the
base slab as opposed to the use of other temporary structures
like king posts and struts.
At the basement loading and unloading bays, steel trusses were
proposed, to deal with the long span and heavy loadings that
were needed to avoid columns in the driveway. This enabled
the 1st storey slab to have a high loading to accommodate
the planters and transfer columns from the podium above.
In addition, it provided a clear passageway for fire engine
access. As this section of the basement is connected to the
new bridge at the 1st storey, the construction sequence at
this area was delayed till the bridge was completed. The use
of steel trusses enabled the construction sequence to meet
the programme while the remaining 1st storey was being
constructed independently in reinforced concrete.
Minimising disturbance to the neighbourhood
Given CREATE’s close proximity to the rest of the facilities
within the National University of Singapore and public residences,
sound barriers were erected to minimise noise caused by the
use of heavy machinery during precast and steel construction.
Noise and vibration monitoring systems were installed,
which could be remotely accessed, for better tracking of the
situation on site.
The plaza connects all four buildings and serves as an informal interactive space.
PROJECT CREDITS
Client
National Research Foundation
Prime Minister’s Office, Singapore
Client Representative / Project Manager
Jurong Consultants Pte Ltd
Architects
Perkins + Will
DP Architects Pte Ltd
Structural Consultant
Arup
MEP Consultants
Arup
WSP Ng Pte Ltd
Quantity Surveyor
Faithful+Gould Pte Ltd
Façade Consultant
Meinhardt FaçadeTechnology Pte Ltd
Acoustic andVibration Consultant
Arup
Sustainability Consultant
Arup
Lighting Consultant
Meinhardt Light Studio Pte Ltd
Main Contractor
Obayashi Corporation
All images by Darren Soh.

CONCRETETECHNOLOGY
17
INTRODUCTION
Under the heading ‘Concrete Repairs Its Own Cracks’, the New
York Times1
wrote in September 1992 about the pioneering
work of Prof Dry on self-healing concrete. Hollow fibres filled
with specific chemicals - a healing agent - and distributed
throughout the cement matrix would release the healing agent
into a crack once this crack meets the fibre and breaks it.This
self-healing concrete would improve the strength and durability
of the concrete. In the same article, research was mentioned
on the use of special fibres around steel reinforcing bars.When
the rebars would start to corrode, the nearby fibres should
release anti-corrosive chemicals.The article ends by saying that
the research of Dry would be finished within two years, but that
it was not known yet when the self-repairing concrete would
become commercially available.
Since the start of her pioneering work, Dry has published many
inspiring papers on self-healing concrete2,3,4
. But still, 20 years
later,self-healing concrete is in its development stage.Meanwhile,
the demand for a material that can repair its own cracks has
increased, partly for reasons mentioned by Dry already, ie
improvement of durability,partly also for new reasons.In the past
two decades, the building industry became faced with a number
of serious and unprecedented problems. Problems relating to
scarcity of raw materials and energy,and emission of hazardous
products, are among the most frequently mentioned problems.
The yearly world-wide demand for concrete has reached
0.5m3
to1.0m3
percapita.IntheUK,thebuildingandconstruction
industry is estimated to be responsible for up to 50% of CO2
production5
. The building industry consumes a large amount
of energy,while the production of cement is held responsible for
5% to 8% of the world’s CO2
emission. Given the rapid growth
of the economies of China and India, this figure is expected to
increase rapidly, if the technology to produce cement remains
unchanged.Another issue concerns the huge maintenance costs
for structures built in the past. From 600,000 bridges in the USA,
one out of four needs to be modernised or repaired6
. About
10% of the bridges are considered structurally deficient and
also 10% is considered functionally obsolete.The total amount
of money involved in repair and upgrading is estimated at
US$ 140,000,000,0007
. InThe Netherlands, 50% of about 1,000
inspected bridges, viaducts and tunnels required further detailed
inspection of their load-bearing structure. In that country, one
third of the annual budget for large civil engineering works is
spent on inspection, monitoring, maintenance, upgrading and
repair. In the UK, the costs for repair and maintenance accounts
for almost 45% of UK’s activity in the construction and building
industry8
. Apart from these direct costs for maintenance and
repair of bridges,the indirect costs caused by traffic interruptions
have to be considered.These indirect costs are often 10 times
the direct costs9
. The costs to the US economy of people
spending time in traffic jams are estimated at S$ 63 billion
per year10.
There is no doubt the lack of quality and premature
failure of ageing infrastructure is a trillion dollar issue!
The high financial losses caused by premature failure of concrete
Self-healing material concepts as solution for
ageing infrastructure
by Klaas van Breugel, Delft University of Technology, The Netherlands
The rapidly growing world population and booming economies are two of the major reasons
for an increasing demand for buildings and infrastructure. In order to meet these needs, large
amounts of energy and raw materials are required. In most cases, concrete is the main building
material for these structures. The question today is how these needs can be accomplished
without compromising the ability of future generations to meet their needs (Brundlandt). In
this article, first the urgency of this question is explained from the perspective of the building
industry. Emphasis is put on the consequences of the lack of quality and related failure costs.
This lack of quality results in premature maintenance and repair or even decommissioning
and demolishing of structures. But even good quality structures do suffer from ageing of
the materials from which these structures were built. Given this fact, it is considered a great
challenge to design materials with an inherent potential to heal themselves once any kind of
deterioration or ageing starts.That would extend the service life of concrete structures and,
hence, mitigate the pressure on the need of raw materials and energy for new building. But
how realistic are self-healing concepts? Are they reliable and affordable and is it possible to
estimate the potential savings by using self-healing materials? These are the questions to be
addressed in this contribution.

CONCRETETECHNOLOGY
structures and the high emissions of greenhouse gases, high
energy consumption and increasing scarcity of raw materials are
typical sustainability issues. Today the building industry can no
longer ignore these issues.
Mitigation of the ecological footprint can no longer be
considered as something ‘extra’ on top of technological and
industrial achievements, but as an inherent component of them.
Steps towards a sustainable building industry focus on, among
other things11
:
• Minimising resource consumption
• Preference for renewable materials and energy
• Closed cycles of non-renewables
• Optimising the life-span of a structure by using more reliable
and easily repairable materials
• Reduction of maintenance costs by extending the service life
of structures
From the materials science point of view, the focus is on pro-
active management of ageing. A possible way to achieve this is
by using self-healing materials, if they exist! By using self-healing
materials, the life -pan of structures can be extended, resulting in
reduction of the maintenance costs.The use of scarce resources
and energy will be reduced as well, because the moment of new
building can be postponed. Apart from the lower consumption
of resources, a longer life-span of structures also reduces the
need for construction-related transport of materials and people.
Knowing that in industrialised countries 30%-50% of the traffic is
related to building activities,enormous direct and indirect savings
can be realised by extending the service life of infrastructure.
SELF-HEALING POTENTIAL OF CONCRETE
DAMAGE PREVENTION VERSUS DAMAGE CONTROL
The traditional way to make things better is to make them
stronger and stiffer. This philosophy has pushed materials
technology in the direction of high strength and ultra-high-
strength materials. The design philosophy that focuses on
preventing damage by using stronger materials has been
termed Damage Prevention Paradigm. Improving the strength
of a material will certainly increase the load-bearing capacity
and postpone the moment the first damage occurs. However,
it is still an incremental improvement of existing technology
within the Damage Prevention Paradigm. It is different with the
Damage Control Paradigm,where a certain degree of damage is
not only considered acceptable, but is even supposed to initiate
an inherent mechanism of self-repair or self-healing.
The two indicated design paradigms, ie the Damage Prevention
Paradigm and Damage Control Paradigm, are applicable for
the majority of materials, but generally not so, for reinforced
concrete. Concrete is a brittle material with microcracks
throughout the body of material already prior to application of
any load. Moreover, cracks are not considered as damage and
are acceptable as long as a prevailing crack width criterion is not
exceeded. From the materials science point of view, therefore,
a design in reinforced concrete is always a design within the
Damage Control Paradigm. In a traditional concrete design,
however, cracks are not considered as damage. Microcracks are
an inherent feature of ordinary concrete, whereas macrocracks
are a characteristic for a design in reinforced concrete.
The fact that in structural (concrete) design,cracks are acceptable
does not mean that they are desirable. From the safety point
of view, the presence of cracks is no reason to worry. Cracks,
however, and certainly those which form a connected network
of cracks, jeopardise the resistance of the concrete against
ingress of harmful substances into the concrete. The concrete
may then deteriorate fast and the steel reinforcement is no
longer adequately protected against corrosion.
Cracks may also be undesirable from the functional and aesthetic
point of view. So, even though cracks are not problematic from
the safety point for view, they are undesirable from the overall
performance point of view, in particular, from the durability
and functionality point of view. It would be good if cracks, if
considered unavoidable because of the inherent brittleness of
cement-based materials,could be healed by a built-in self-healing
mechanism. Damage control should then not be restricted to
control of the crack width - the common practice in concrete
design - but should also focus on healing of the cracks once
they occur.
The Damage Prevention Paradigm (DPP) and the Damage
Control Paradigm (DCP) are shown schematically in Figure 1. In
the DPP,a longer service life of structures is achieved by increasing
the materials properties, for example, increasing the strength
and reducing the permeability. Deterioration is postponed and
the maintenance-free period extended. However, once cracking
of the concrete starts, the decay rate is relatively high and
manual (expensive) repair is required. In the DCP, the material is
so designed that small cracks, or other damage mechanisms, are
allowed to happen and trigger an autogenous or autonomous
self-healing process. The self-healing process will bring the
material back to its original performance level.
SELF-HEALING CONCRETE
Autogenous self-healing and self-sealing
In most of the traditional concrete mixtures, 20%-30% of the
cement is left unhydrated.The higher the amount of unreacted
cement, coarser is the cement and lower is the water/cement
ratio of the mixture.If cracking of the concrete occurs,unreacted
cement grains may become exposed to moisture penetrating
Figure 1: Damage Prevention Paradigm (DPP: manual repair) (left) and the
Damage Control Paradigm (DCP: self-healing) (right).

CONCRETETECHNOLOGY
19
the crack. In that case, the hydration process may start again and
hydration products may fill up and heal the crack.This inherent
self-healing mechanism, known as autogenous healing, has been
known for long.
This autogenous healing of cracks in fractured concrete was
noticed by the French Academy of Science, in 1836, already in
water retaining structures, culverts and pipes12
. According to
Hearn13
, the self-healing phenomenon was studied by Hyde14
at
the end of the 19th
century already. A more systematic analysis
of healing phenomena was executed by Glanville15
and dates
back to 1926.
Already at that time a distinction was made between self-sealing
and self-healing.
Self-sealing was studied systematically by Hearn12
. Out of seven
possible mechanisms, four were investigated in more detail, viz
a) dissolution, deposition and crystallisation, b) physical clogging,
c) continuing hydration and d) swelling of the cement matrix
(Figure 2). From an evaluation of literature, data and experiments
on 26-years old concrete, Hearn concluded that dissolution
and deposition is the main mechanism of self-sealing in mature
concretes. Continuing hydration was the second important
mechanism, albeit more important for young concrete than
mature concrete. Hearn emphasised that concrete with the
potential of self-sealing has a significantly higher‘immune system’to
respond to the environment than non-self-sealing concretes.This
improvement of the immune system over time was considered of
particular importance in view of the structure’s service life.
Glanville’s first studies on self-healing were followed by studies
of Soroker et al16
and Brandeis17
of cracks in bridges and date
back to 1926 and 1937. In 1996, Jacobsen et al18
observed self-
healing of concrete specimens exposed to freeze-thaw cycles.
Self-healing of leaking cracks was studied extensively by Clear19
and Edvardsen20
. Otsuki et al21
suggested that self-healing of
microcracks could have been the reason for densification of the
concrete cover, thus reducing the rate of migration of chloride
ions into the concrete (Figure 3). Self-healing of microcracks
resulting in a decrease of chloride ingress into concrete has also
been suggested by Fidjestol et al22
and Bakker23
. According to
Van Tittelboom et al24
, the mix composition, ie type of cement,
influences the efficiency of the autogenous self-healing capacity.
Reinhardt et al25
found that self-healing of cracks will benefit
from higher temperatures.
In all the aforementioned studies, self-healing is considered an
inherent feature of cement-based materials. This feature makes
concrete a material with a lot of ‘forgiveness’. Mankind has taken
advantage of this peculiar property of concrete, even though
concrete was never designed deliberately to be a self-healing
material. Neither the self-healing process itself, nor the required
preconditions for making this process to happen are completely
understood today. As a consequence, the self-healing capacity of
cement-based systems is considered a positive feature of concrete
indeed,but too unreliable yet to take into account explicitly in the
design of concrete structures. Only a few exceptions are known
where designers explicitly count on the occurrence of self-healing
of cracks, for example, in the design of watertight cellars or
reservoirs made of reinforced concrete26
. To ensure that these
structures will behave liquid-tight, the crack width should not
exceed a certain value.The acceptable crack width depends on
the pressure differential over the concrete wall or slab, the crack
width and the stability of the crack.Almost no criteria for the type
of concrete itself are given.This in fact demonstrates that the self-
healing capacity of ordinary concretes is considered a byproduct
of the material rather than a feature that could be manipulated by
a sophisticated design of the mixture.
Preconditions for the occurrence of self-healing in ordinary
concretes are, apart from the presence of unhydrated cement
and moisture, a limited crack width27
.The smaller the cracks are,
the higher the probability that the cracks will heal. A cement-
based product that is designed for a small crack width is ECC
(Engineered Cementitious Composites) developed by Li et al28
.
The main purpose for designing ECC was to make a ductile
material that is able to make large excursions in the post-
cracking phase.
The use of small fibres ensures that on cracking, the crack width
remains very small, typically 50 μm. Thus it can accommodate
large imposed deformations and makes it perfectly suitable as
repair material. Because of the small crack width, ECC has a
remarkable self-healing capacity, and can even recover the
original strength after healing.
Autonomous self-healing of concrete
Whereas autogenous self-healing can be considered an inherent
feature of cement-based systems, autonomous self-healing is
defined as a purposely designed self-healing mechanism. In a
recent PhD thesis,VanTittelboom29
gave an extensive literature
survey of autonomous self-healing.
Figure 2: Self healing/sealing mechanisms - a) dissolution, deposition and
crystallisation b) physical clogging c) continuing hydration and d) swelling of the
cement matrix.
Figure 3: Healing of microcracks in concrete cover due to continuing hydration
(schematic, after a suggestion of Otsuki et al21
).

CONCRETETECHNOLOGY
An often-mentioned way to realise autonomous self-healing
is by dispersing capsules containing either a cementitious or
synthetic healing agent. This encapsulation concept has been
proposed by White et al30
in 2001 for self-healing polymers and,
as mentioned in the introduction already, by Dry2,3,4
in the early
1990s, for self-healing concrete. On cracking, the capsules may
rupture, while releasing the healing agent into the crack.This is
the most common concept, but not often used in concrete yet.
In case a cementitious healing agent is used, the presence of
water is a prerequisite for the self-healing process to happen.
The water may penetrate into a crack from external sources.
Alternatively, water-saturated porous lightweight aggregate
particles can be added to the concrete mixture.These particles
may release water when a crack occurs and moisture gradients
stimulate the flow of water.
Van Tittelboom29
also investigated the use of small glass tubes
filled with a self-healing agent. If a crack passes the brittle glass
tube, the probability it breaks is almost 100%. The internal
diameter of the tubes varied from 1.71 to 3.00 mm.A problem
with tubes with this diameter is their vulnerability during the
concrete mixing process. Less vulnerable are healing agents
containing wood fibres or glass fibres with a diameter between
30 μm to 100 μm, as used for self-healing polymer composites31
.
The fact that concrete is a heterogeneous material by definition,
means that adding capsules to the mixture does not significantly
change the nature of the material.As long as the capsules are not
broken, their role is not much different from that of aggregates,
albeit that their strength and stiffness are different. The effect
of adding capsules on the still uncracked concrete depends on
the mechanical properties of the capsules, their size and shape
and their amount.The number of capsules needed to ensure a
sufficiently high probability of a crack passing a capsule depends
on the size and shape of the capsules. In this respect, capsules
with a large aspect ratio, with cylindrical tubes as the extreme,
are more effective than spherical capsules.
The most appropriate agent for healing cracks in a cementitious
matrix is still a matter of debate. A polymeric agent is good
for filling cracks. However, as a non-cementitious material, it
may become detached from the crack surface. With elapse
of time, the polymer may be susceptible to ageing which may
jeopardise the long-term effectiveness of the healing process.
Kishi et al32
investigated self-healing of cracks by cementitious
recrystallisation of an expansive agent. A cementitious healing
agent requires water in order to become effective.In the absence
of water, healing will not occur. How serious this is depends on
the required function of the structure and the loading scenarios
the structure has to cope with.
BIO-BASED SELF-HEALING
MECHANISMS OF BIO-BASED HEALING
One of the preconditions of self-healing of cracks in concrete is
the transport of matter to the crack.In a living organism,transport
of ingredients takes place via a vascular system.In plants and trees,
ingredients are transported via a network of pores. A porous
material like concrete also has a pore system through which
transport processes are possible, but a driving force that makes
transport of healing species happen is not inherently present.
Temperature, moisture, pressure or concentration gradients are
needed to trigger transport of species. But still it is not easy to
transport sufficient matter to the spot, ie crack, where healing
is needed. Promising in this respect is the concept of bacteria-
based healing of cracks33
.The idea is that after cracking, mixed-in
bacteria on fresh concrete crack surfaces are activated in the
presence of water, and then start to multiply and precipitate
minerals, such as calcium carbonate, and close the crack. The
healing mechanism is presented schematically in Figure 4.
BACTERIA IN HIGH PH
Jonkers33
started his study of bio-based healing of cracks with a
search for bacteria which could potentially act as a self-healing
agent in concrete. A precondition for a successful healing
process is that the bacteria survive the high pH in the concrete
of about 12 to 13. It was found that from a microbiological
viewpoint, the application of bacteria in concrete, or concrete as
a habitat for specialised bacteria, is not odd at all. Although the
concrete matrix may seem at first inhospitable for life because
of its high alkalinity, comparable natural systems are known
in which bacteria do thrive, even in a very dry environment.
Inside rocks, even at a depth of more than 1 km within the
earth’s crust, in deserts as well as in ultra-basic environments,
active bacteria are found34,35,36,37,38,39
. The desiccation- and/or
alkali-resistant bacteria typically form spores, ie specialised cells
able to resist high mechanically and chemically induced stresses40
.
These spores have extremely long lifetimes - they are known to
be viable for up to 200 years.
The crack-healing potential of mineral-precipitating bacteria
in degraded limestone42
, ornamental stone43
and concrete
surfaces44,45
has been reported. In these studies, the bacteria
and compounds needed for mineral precipitation were brought
into contact with virgin crack surfaces. Since the healing agent
was added afterwards, this form of healing of cracks cannot
be considered as self-healing. For self-healing concrete, the
bacteria should ideally be embedded in the material from time
zero onwards.
Figure 4: Scenario of crack-healing by concrete-immobilised bacteria. Bacteria on
fresh crack surfaces become activated due to water ingression, start to multiply
and precipitate minerals such as calcite (CaCO3
) which eventually seal the crack
and protect the steel reinforcement from further external chemical attack
(after Jonkers33
).
Spores
Activated bacteria
Calcite formations

CONCRETETECHNOLOGY
21
The bacteria to be used as the self-healing agent in concrete
should be fit for the job, ie they should be able to perform
long-term effective crack sealing, preferrably during the total
life-time of a structure. The principal mechanism of bacterial
crack healing is that the bacteria themselves act largely as a
catalyst, and transform a precursor compound to a suitable
filler material.The newly produced compounds, such as calcium
carbonate-based mineral precipitates, should then act as a type
of bio-cement that seals or heals newly formed cracks.Thus for
effective self-healing, both bacteria and a bio-cement precursor
compound should be integrated in the material matrix.
The presence of the matrix-embedded bacteria and precursor
compounds should not negatively affect other desired concrete
properties.Bacteria that can resist concrete matrix incorporation
exist in nature, and these appear related to a specialised group
of alkali-resistant spore-forming bacteria. An interesting feature
of these bacteria is that they are able to form spores, which are
specialised spherical thick-walled cells somewhat homologous
to plant seeds.These spores, with a diameter about 1 μm, are
shown in Figure 5. They are viable but dormant cells and can
withstand mechanical and chemical stresses and remain in a
dry state for periods of over 50 years. Jonkers et al47
found
that when bacterial spores were directly added to the concrete
mixture, their life-time was limited to one or two months.The
decrease in lifetime of the bacterial spores from several decades
when in dry state to only a few months when embedded in the
concrete matrix was attributed to continuing cement hydration
resulting in matrix pore-diameter widths typically much smaller
than the 1 μm sized bacterial spores.
Another concern is whether direct addition of organic bio-
mineral precursor compounds to the concrete mixture will
result in unwanted loss of other concrete properties. Various
organic bio-cement precursor compounds,such as yeast extract,
peptone and calcium acetate, were indeed found to result in a
dramatic decrease of compressive strength. However, promising
results were obtained with calcium lactate. Adding this
compound resulted in a 10% increase in compressive strength
compared to control specimens47
.
ENCAPSULATION OF BACTERIA
With the aim to increase the life-time and associated functionality
of bacteria in the concrete, the effect of bacterial spores and
simultaneously needed organic bio-mineral precursor compound
(calcium lactate), should be understood. Jonkers46
tested the
immobilisation of these components in porous expanded clay
particles (Figure 6). It was found that protection of the bacterial
spores by immobilisation inside porous expanded clay particles
before addition to the concrete mixture indeed substantially
prolonged their life-time. After six months incorporation in
concrete, no loss of viability of the spores was observed,
suggesting that their long-term viability, as observed in the dried
state when not embedded in concrete, is maintained.
EVIDENCE OF BACTERIAL SELF-HEALING
Materials used and experimental set-up
In order to test the bacterial healing of cracks in concrete, test
specimens were prepared in which part of the dense aggregate
was replaced by similarly sized expanded clay particles loaded
with the biochemical self-healing agent (bacterial spores
plus calcium lactate). The amount of lightweight aggregate
represented 50% of the total aggregate volume.
Control specimens had a similar aggregate composition,
but these expanded clay particles were not loaded with the
bio-chemical agent.
The self-healing capacity of pre-cracked concrete disks (10 cm
diameter, 1,5 cm thickness), sawn from 56 days water cured
concrete cylinders, was tested by measuring the evolution
of water transport through the disks and by taking light
microscopic images before and after the permeability test. For
determination of the permeability, the pre-cracked concrete
disks were glued in an aluminium ring and mounted in a custom
Figure 5: ESEM photomicrograph of alkali-resistant spore forming bacterium
(Bacillus strain B2-E2-1).Visible are active vegetative bacteria (rods) and spores
(spheres), showing that spore diameter sizes are in the order of 1 micrometre
(Jonkers46
).
Figure 6: Self-healing admixture composed of expanded clay particles (left) loaded
with bacterial spores and organic bio-mineral precursor compound (calcium
lactate).When embedded in the concrete matrix (right) the ‘loaded’ expanded
clay particles represent reservoirs containing the two-component healing agent
consisting of bacterial spores and a suitable bio-mineral precursor46
.
Light weight
aggregates
with bacterial spores
Light weight
aggregates
with bio-mineral
precursor
Figure 7: Pre-cracking of concrete slab and subsequent permeability testing47
.

CONCRETETECHNOLOGY
made permeability setup.Crack formation in concrete specimen
disks was achieved by a deformation controlled splitting test
(Figure 7, left).The generated crack width was 0.15 mm running
completely through the specimen. After cracking, both sets
(six of each) of control and bacterial concrete specimens were
submerged for two weeks in tap water at room temperature.
Subsequently, permeability of all cracked specimens was
quantified by recording tap water percolation over time during
a 24-hour period (Figure 7, right).
Experimental results - Discussion
Comparison between bacterial and control specimens revealed
a significant difference in permeability. While cracks of all six
bacterial specimens were completely sealed, resulting in no
measurable permeability (percolation of 0 ml water / h), only
two out of six control specimens appeared perfectly healed.
The four other control specimens featured permeability (water
percolation) values between 0 and 2 ml / h.
Microscopic examination of cracks at the water-exposed side of
the slab revealed that in both control and bacterial specimens,
precipitation of calcium carbonate-based mineral precipitates
occurred. However, in the control specimens, precipitation
largely occurred near the crack rim, leaving major parts of the
crack unhealed,whereas efficient and complete healing of cracks
occurred in the bacterial specimens with mineral precipitation
predominantly within the crack (Figure 8).
The most obvious reason for massive white precipitation of
calcium carbonate near the crack rim of the control specimen
(Figure 8A) is that concentration of both reactants, calcium
hydroxide and carbon dioxide are relatively high due to the
opposing diffusion gradients of the respective reactants47.
Calcium hydroxide diffuses away from the crack interior towards
the overlying bulk water, while carbon dioxide diffuses from the
bulk water towards the crack interior where it is scavenged by
high concentrations of calcium hydroxide.
The process of chemical calcium carbonate formation
from dissolved calcium hydroxide occurs according to the
well-known reaction:
CO2
+ Ca(OH)2
→ CaCO3
+H2
O (1)
In the bacteria-modified specimen, two additional reactions
are supposed to explain the efficiency of the healing process.
The self-healing process in bacterial concrete is much more
efficient due to the active metabolic conversion of calcium
lactate (Ca(C3
H5
O2
)2
) by the bacteria present. Schematically the
reaction is:
Lactate + O2
→ acetate + CaCO3
+ CO2
(2)
In formula form:
Ca(C3
H5
O2
)2
+ 7O2
→ CaCO3
+ 5CO2
+ 5H2
O (3)
Equation (2) shows that in this reaction, carbon dioxide is
formed. This is another source of CO2
. It can react with the
calcium hydroxide according to equation (1) resulting in
additional carbonate-based precipitation.
The overall conclusion of the studies by Jonkers46,47
is that the
proposedtwocomponent,bio-chemicalhealingagent,composed
of bacterial spores and a suitable organic bio-cement precursor
compound, is a promising bio-based and thus sustainable
alternative to strictly chemical or cement-based healing agents.
Before practical application becomes feasible, however, further
optimisation of the proposed system is needed.
SMART NANOPARTICLES FOR MITIGATING
RISK OF CORROSION
In 2012, the 4th
international conference on Nanotechnology in
Construction was held in Crete, Greece. Obviously the building
sector has a great interest in this topic. Since healing processes,
by definition, start at the smallest conceivable scale, it may be
presumed that nanotechnology can play a significant role in the
design of self-healing concrete. Meanwhile, promising results
have been reported about the use of admixed nano-particles
for modifying the microstructure and hence the mechanical
properties and permeability of cement-based materials48,49,50
.
Densification of the microstructure reduces the permeability
and the ingress of hazardous substances into the concrete,
thus increasing the concrete’s durability. Koleva et al51,52,55
and
Hu et al53,54
observed significant microstructural changes after
adding micelles to plain mortar. The micelles that were used
were prepared from polyethylene oxide di-block polystyrene
(PEO-b-PS) (Figure 9). Even with a low concentration of
micelles, 0.025 % by weight of dry cement, in a mortar with
a cement-to-sand ratio of 1:3, and water-to-cement ratio of
0.5, the porosity of both the bulk matrix and a steel-matrix
interfacial transition zone (ITZ) decreased significantly53
. The
coefficient of water permeability was three orders of magnitude
lower for the micelles-containing specimen compared to the
micelles-free mortar56,57
.
Figure 8: Light microscopic images of pre-cracked control (A) and bacterial (B)
concrete specimen before (left) and after (right) healing, following two weeks of
submersion in water. Efficient crack healing occurred in all six bacterial and two
out of six control specimens47
.
bacteria

CONCRETETECHNOLOGY
23
The observed improvement of the microstructure at the
steel-matrix ITZ is expected to reduce the risk of rebar corrosion,
by far the most frequent cause of premature deterioration
of reinforced concrete. A next step to even further mitigate
the risk of rebar corrosion could be the use of smart nano
particles, which have the potential to react to changes in the
chemical environment by a sort of self-healing mechanism.
Koleva and her co-workers58,59
investigated the effect, adding
PEO113
-b-PS780
vesicles,which are particles similar to micelles but
carrying an ‘active’ compound, on the rate of corrosion of steel
bars placed in a simulated pore solution.The active compound
was CaO. The hypothesis is that in the event of an aggressive
external influence, ie carbon dioxide penetrating the material
thus carbonating the matrix, or Cl- penetration followed by
localised corrosion on the steel surface, the ‘charged’ vesicles
will participate in a self-healing mechanism by releasing the core
material. The released core material, ie CaO, will restore the
alkalinity in the bulk matrix and repair the passive layer on the
steel surface. How the vesicles react on a drop of the pH is
visualised in Figure 10, where ESEM pictures are presented of
the hybrid nano particles at a pH 11.8, 9.0 and 3.0, respectively.
As can be observed from Figure 10, the morphology of the
particles changes with decreasing pH, from 11.8 to 3. These
changes go along with a decrease of the Ca content in the ‘core’
and an increase in the ‘shell’ around the core.At the same time,
the polymers vanish (dissolve), whereas the calcium containing
compounds are only detected in the bulk.
Koleva et al58
found that, in line with what was expected, the
surface of a steel rebar placed in a pore solution with and
without loaded vesicles exhibited a significant difference, even
for a very low concentration of ‘charged’ particles (4.9 10-4
g/l).
When NaCl was added to the solution, as corrosion accelerator,
the steel in vesicles-containing pore solution exhibited again
superior performance compared to the vesicle-free solution.
ESEM-observation of the product layers on the steel surface
after seven days of conditioning revealed a more homogeneous
and compact protective layer on the steel surface of the
specimens conditioned in the vesicle-containing solution.When
treated in cement extract only, a much higher heterogeneity of
the surface layer was observed, which will make the steel more
susceptible to corrosion.
ECONOMIC CONSIDERATIONS
The production of self-healing materials will most often exceed
the costs of traditional materials. What justifies the extra initial
costs of self healing materials is the reduction of the costs for
inspection, maintenance and repair and a longer service life.
Schematically, this is shown in Figures 11 and 12. In Figure 11a,b,
the performance and costs for a low quality (curve A) and a
high quality (curve B) structure are compared, both designed
according to the Damage Prevention Paradigm (DPP). Figure
12a,b shows similar curves for a system designed according to
the Damage Control Paradigm (DCP). Although schematic, a
comparison of the costs of a system designed according to the
DPP and the DCP illustrate that, depending on the required
life-time of the structure, higher initial costs will finally pay off60
.
If the indirect costs of repair work - not considered in Figure
11b and 12b - would have been taken into account as well,
higher initial costs are almost always justified. Similar conclusions
were drawn by Wolfseher61
from an evaluation of repair costs
versus initial costs for high quality concrete structures. In Figure
12a, the performance of an ideal self-healing material has been
proposed. In reality, the self-healing and self-repairing potential
of a material will be limited. This means that it is not realistic
to expect that the use of self-healing materials will make
inspections, monitoring, maintenance and repair completely
superfluous. However, the building sector can already benefit
from incremental improvements of the self-healing capacity
of a material. If the maintenance-free period can be extended
and the moment of repair can be postponed, high savings are
conceivable already. In this respect, it is important to realise the
huge scale at which concrete is being used. Because of this scale
Figure 9: Formation of frozen core-shell micelles from PEO113
-b-PS780
di-block
copolymer in aqueous media (Koleva et al55
).
Figure 10: ESEM micrographs (left) of hybrid aggregates as received at
pH 11.9 (a), at pH 9 (b) and at pH 3 (c). EDX analysis for C and Ca in the
indicated locations (right)58
.

CONCRETETECHNOLOGY
effect, minor improvements of the materials performance can
already result in huge savings of repair and maintenance costs.
Moreover, situations are conceivable where degradation of a
structure should be avoided at all costs because of extremely
high consequences in case of failure (for example, leakage of
radioactive waste).In those cases,the use of a robust self-healing
material could be the only solution. If the use of a self-healing
material is the only realistic solution, the extra costs of the
material will be no limiting factor at all.
CHALLENGES AND PROSPECTS
FROM ‘STATIC SOLIDS’ TO ‘DYNAMIC SYSTEMS’
Designing self-healing materials requires another way of thinking.
The occurrence of some form of damage is not prevented at all
cost (the traditional Damage Prevention Paradigm), but is used
to initiate, on purpose, a mechanism or process of healing. As
indicated earlier in this article, concrete is already an inherently
self-healing material because of the presence of unhydrated
cement grains. In the presence of water, transported via cracks
to these unhydrated grains, hydration occurs and the hydration
products may heal the cracks. This so-called autogenous self-
healing capacity of concrete, although present in most concretes
mixtures,cannot prevent concrete infrastructure from ageing and
degradation beyond acceptable limits. If healing is accomplished
by incorporating additional healing agents, the resulting healing
process is called autonomous self-healing.
After a brief overview of possible self-healing concepts, this
article has focused first on autonomous healing of microcracks
with appropriate bacteria. It was explained how bacterial activity
is triggered by the occurrence of microcracks and the presence
of oxygen. In the presented example, bacteria and food were
encapsulated in lightweight aggregate particles. Precipitation of
calcium carbonate in microcracks restores or even improves the
density/tightness of the concrete, thus increasing the resistance
against ingress of aggressive substances, like chloride ions.
Another autonomous self-healing concept discussed in more
detail in this article concerned the use of smart nanoparticles,
ie CaO-charged vesicles, for increasing the resistance against
corrosion of steel rebars.The self-healing process was triggered
by a decrease of the pH of the pore water, at which point the
vesicles started to dissolve while releasing CaO to the bulk.The
pH in the pore solution increases, while at the same time the
passive layer on the steel surface remained intact.
These examples illustrate the need for another way of thinking
about materials performance and materials design. Self-healing
materials are no ‘static solids’, but ‘dynamic systems’, able to
respond to external loads with a damage-healing process.
AUTOGENOUS SELF-HEALING AND SUSTAINABILITY
The inherent self-healing capacity of concrete is supposed to
increase with higher cement content of the mixture. From that
point of view, high strength concrete with high cement content
is potentially more prone to self-healing then concrete with low
cement content. From the sustainability point of view, however,
mixtures are desired with cement content as low as possible61
.
Using low cement content is positive in view of reduction of
the cement-related CO2
emission, but it reduces the concrete’s
autogenous self-healing capacity. If mixtures with low cement
content are required for sustainability reasons, self-healing
should, therefore, be realised preferrably through autonomous
self-healing.
Figure 11: Performance (a) and costs (b) with elapse of time for low quality (A)
and high quality (B) structures. Direct costs of repair included. Interest and inflation
are not considered60
.
Figure 12: Performance (a) and cost (b) of a structure made with self-healing
material (concrete) with elapse of time. Interest and inflation are not considered60
.
A
B
performance
Required performance
time
Fig. 11a
2nd
repair
1st
repair
cost
A
B
Fig. 11b
time
performance
cost
Fig. 12a
Fig. 12b
Required performance

CONCRETETECHNOLOGY
25
SELF-HEALING MATERIALS IN VIEW OF
ENVIRONMENTAL STEWARDSHIP
According to Long63
,the infrastructure in industrialised countries
accounts for at least 50% of the national wealth. From that he
inferred that the performance and quality of the infrastructure
are of fundamental importance to urban sustainability and
the well-being of the environment. Extending the service life
of infrastructure will certainly contribute to mitigation of the
ecological footprint. Engineers should be aware of this when
designing infrastructural works and when making choices for
concrete mixtures. The development and use of self-healing
materials are most challenging options to accomplish the need
for durable infrastructure.
In view of the large impact of the building industry on the
environment,promoting self-healing materials can be considered
as a matter of environmental stewardship. Since concrete is,
volume-wise, the most often used building material, enormous
savings are achievable, even if we make small improvements in
the quality and durability of our infrastructure. On top of that, it
is worthwhile to know that investing in self-healing materials, in
view of reduction of maintenance costs, finally pays off60,61
.
ACKNOWLEDGEMENTS
The author would like to thank his colleagues Dr E Schlangen,
DrV Wiktor, Dr D A Koleva, Dr J Hu, Dr H M Jonkers and Dr O
Copuroglu,who are all active in research on self-healing materials
and kindly provided valuable input.The financial support of the
Delft Centre for Materials of the TU Delft and the Ministry of
Economic Affairs of The Netherlands, under the ‘IOP-program
Self-healing materials’, is gratefully acknowledged.
REFERENCES
[1] New York Times: ‘Concrete Repairs Its Own Cracks’,
SCIENCE WATCH (1992).
[2] CM Dry: ‘Procedures developed for self repair of polymer
matrix composite materials in composite structures (3)’, Elsevier,
London, 263-269 (1996).
[3] CM Dry: ‘Matrix cracking, repair and filling using active and
passive modes for smart timed releases of internal chemicals’,
Smart Materials & Structures (3), 118-123 (1994).
[4] CM Dry:‘Development of a self-repairing durable concrete’,
Natural Process Design, Icn. Minnesota 507-452-9113.
[5] DEFRA: ‘Joint UK-Sweden Initiative on Sustainable
Construction’ www.Constructing excellence.org.uk/uksweden/
defra.jsp?level=0 (2005).
[6] S Liles and S Liles: ‘Our crumbling infrastructure: How the
aging of America’s infrastructure is a homeland security concern’,
7 p, www.selil.com/?p=260-61k (2008).
[7] Frontier India Strategic and Defence - News, Analysis,
Opinion: ‘$140 billion price tag to repair and modernize
America’s bridges’, 3 p, www.frontierindia.net/140-billion-price-
tag-to-repairand-modernize-americas-bridges - 32k (2008).
[8] J Woudhuysen, I Abley:‘Why is Construction so Backward?’,
Wiley-Acad 321 (2004).
[9] M Yunovich, NG Thompson: ‘Corrosion of highway bridges:
Economic impact and control Methodologies’, Concrete
International,Vol 25 (1) 52-57 (2003).
[10] S Flynn: ‘5 Disasters coming soon if we don’t rebuild US
infrastructure’, Popular Mechanics, www.popularmechanics.com/
science/worst_case_scenarios/ 4227310.html (2007).
[11] K Mulder: ‘Sustainable Developments for Engineers’, Delft
University Press, 288 p, (2006).
[12] N Hearn, CT Morley: ‘Self-sealing property of concrete
- Experimental evidence’, Materials and Structures, Vol 30,
404-411 (1997).
[13] N Hearn: ‘Self-healing, autogenous healing and continued
hydration: What is the difference?’, Materials and Structures,
Vol 31, 563-567 (1998).
[14] GW Hyde, WJ Smith: ‘Results of experiments made to
determine the permeability of cements and cement mortars’,
Journal of the Franklin Institute Philadelphia, 199-207 (1889).
[15] WH Glanville: ‘The permeability of Portland cement
concrete’, Building Research,Technical Paper 3, 1-61 (1931).
[16] VJ Soroker, AJ Denson: ‘Autogenous healing of concrete’,
Zement 25 (30) (1926).
[17] F Brandeis: ‘Autogenous healing of concrete’, Beton und
Eisen 36 (12) (1937).
[18] S Jacobsen, EJ Sellevold: ‘Self-healing of high strength
concrete after deterioration by freeze/thaw’, Cement and
Concrete Research,Vol 26, No 1, 55-62 (1996).
[19] CA Clear: ‘The effects of autogenous healing upon the
leakage of water through cracks in Concrete’, Cement &
Concrete Association,Tech Rep 559, 31 p (1985).
[20] C Edvardsen: ‘Water permeability and autogenous healing
of cracks in concrete’, ACI Materials Journal,Vol 96, No 4, 448-
454 (1999).
[21] N Otsuki, S Miyazato, NB Diola, H Suzuki: ‘Influences of
bending crack and water-cement ratio on chloride-induced
corrosion of main reinforcing bars and stirrups’, ACI Materials
Journal,Vol 97, No 4, pp 454-464 (2000).
[22] P Fidjestol, N Nilsen: ACI Special Publication 65,
205-221 (1980).
[23] RFM Bakker, Report RILEM TC 60-CSC, Chapman & Hall,
22-54 (1988).
[24] K van Tittelboom, N de Belie: ‘Autogenous healing of
cracks in cementitious materials with varying mix compositions’,
Proc 2nd
Int Conf on Self-Healing Materials, Chicago (2009).
[25] HW Reinhardt, M. Jooss: ‘Permeability and self-healing of
cracked concrete as a function of temperature and crack width’,

CONCRETETECHNOLOGY
Cement and Concrete Research,Vol 33, 981-985 (2003).
[26] G Lohmeyer,Wiesse Wannen - Einfach und Sicher, Beton-
Verlag, Düsseldorf, p 255 (1994).
[27] D Homma, H Mihashi, T Nishiwaki: ‘Self-healing capacity
of fibre reinforced cementitious composites’, J of Advanced
ConcreteTechnology,Vol. 7, (2) 217-228 (2009).
[28] VC Li, EHYang: ‘Self healing in concrete materials’, in
Self Healing Materials, Ed S van der Zwaag, Springer,
61-193 (2007).
[29] K Van Tittelboom: ‘Self-healing concrete through
incorporation of encapsulated bacteria or polymer-based
healing agents’, PhD-Thesis, Gent 344 (2012).
[30] SR White, NR Sottos, PH Geubelle, JS Moore, MR Kessler,
SR Sriram, EN Brown, S Viswanathan: ‘Autonomic healing of
polymer composites’, Nature, 409:794-797 (2001).
[31] IP Bond, RS Trask, HR Williams, GJ Williams: ‘Self healing
fibre-reinforced polymer composites: An overview’, in Self
Healing Materials - An alternative approach to 20 Centuries of
materials science, Ed S van der Zwaag, Springer, 115-138 (2007).
[32] T Kishi,T Ahn, A Hosoda, S Suzuki, H Takaoka: ‘Self-healing
behaviour by cementitious recrystallisation of cracked concrete
incorporating expansive agent’, Proc 1st
Int Conf on Self-Healing
Materials, Noordwijk,The Netherlands (2007).
[33] HM Jonkers: ‘Self Healing Concrete: A Biological
Approach’, in Self Healing Materials, Ed S van der Zwaag,
Springer, 195-204 (2007).
[34] BB Jorgensen,S D’Hondt:‘A starving majority deep beneath
the seafloor’, Science 314:932-934 (2006).
[35] P Fajardo-Cavazos, W Nicholson: ‘Bacillus endospores
isolated from granite: Close molecular relationships to
globally distributed Bacillus spp from endolithic and extreme
environments’, Applied Environmental Microbiology 72:2856-
2863 (2006).
[36] RI Dorn, TM Oberlander: ‘Microbial origin of Desert
Varnish’, Science 213:1245-1247 (1981).
[37] JR DelaTorre, BM Goebel, EI Friedmann, NR Pace:‘Microbial
diversity of cryptoendolithic communities from the McMurdo
Dry Valleys, Antarctica’, Applied Environmental Microbiology
69:3858-3867 (2003).
[38] K Pedersen, E Nilsson, J Arlinger, L Hallbeck, A O’Neill:
‘Distribution, diversity and activity of microorganisms in the
hyper-alkaline spring waters of Maqarin in Jordan’,Extremophiles
8:151-164 (2004).
[39] NH Sleep, A Meibom, T Fridriksson, RG Coleman,
DK Bird:‘H-2-rich fluids from serpentinization: Geochemical and
biotic implications’, PNAS 101:12818-12823 (2004).
[40] JL Sagripanti, A Bonifacino: ‘Comparative sporicidal effects
of liquid chemical agents, Applied Environmental Microbiology
62:545-551 (1991).
[41] HG Schlegel: General Microbiology, 7th
edition, Cambridge
University Press (1993).
[42] J Dick ,W deWindt,B de Graef,H Saveyn,PVan der Meeren,
N de Belie,WVerstraete:‘Bio-deposition of a calcium carbonate
layer on degraded limestone by Bacillus Species’, Biodegradation
17:357-367 (2006).
[43]CRodriguez-Navarro,MRodriguez-Gallego,KBenChekroun,
MT Gonzalez-Munoz: ‘Conservation of ornamental stone by
Myxococcus xanthus-induced carbonate biomineralization’,
Applied Environmental Microbiology, 69:2182-2193 (2003).
[44] SS Bang, JK Galinat, V Ramakrishnan: ‘Calcite precipitation
induced by polyurethaneimmobilized Bacillus pasteurii’, Enzyme
and MicrobialTechnology 28:404-409 (2001).
[45] SK Ramachandran,V Ramakrishnan, SS Bang: ‘Remediation
of concrete using microorganisms’, ACI Materials Journal
98:3-9 (2001).
[46] HM Jonkers:‘Bacteria-based self-healing concrete’, HERON
Vol 56 (2011) No 1/2.
[47] HM Jonkers, A Thijssen, G Muyzer, O Copuroglu, E
Schlangen: ‘Application of bacteria as self-healing agent for the
development of sustainable concrete’, Ecological Engineering
36(2): 230-235 (2010).
[48] L Hui,H Xiao,JYuan,J Ou:‘Microstructure of cement mortar
with nano-particles’, Composites B 35, 185 (2004).
[49] S Collopardi, A Borsoi, JJ Ogoumah Olagot, R Troli, M
Collepardi,AQ Cursio:‘Influence of nano-sized mineral additions
on performance of SCC’,in Proc of the 6th
International congress
on global construction, ultimate concrete opportunities,
Dundee, UK, 5–7 July 2005.
[50] MH Zhang, H Li: ‘Chloride permeability of concrete
containing nano-particles for pavement’, Structural Health
Monitoring and Intelligent Infrastructure, Vols 1 and 2,
Proceedings and Monographs in Engineering, Water and Earth
Sciences 1469-1474 (2006).
[51] DA Koleva, G Ye, J Zhou, P Petrov, K van Breugel:‘Material
properties of mortar specimens at early stage of hydration in
the presence of polymeric nano-aggregates’, Int Conference on
Microstructure related Durability of Cementitious Composites,
Nanjing, China, 13-15 October, RILEM Publications SARL
161-168 (2008).
[52] DA Koleva, K van Breugel, G Ye, J Zhou, G Chamululu, E
Koenders: ‘Porosity and Permeability of Mortar Specimens
Incorporating PEO113
–b–PS218
Micelles’, Special issue of ACI
Materials Journal, SP267, 101-110 (2009).
[53] J Hu, DA Koleva, K van Breugel:‘Effect of Admixed Micelles
on the Microstructure Alterations of Reinforced Mortar

CONCRETETECHNOLOGY
27
Subjected to Chloride Induced Corrosion’,Procedia Engineering
14, 344-352 (2011).
[54] J Hu, DA Koleva, K van Breugel, JMC Mol, JHW de Wit:
‘The Influence of Admixed Micelles on Corrosion Performance
of Reinforced Mortar’, the European Corrosion Congress
(ERUOCORR), Moscow, Russia (2010).
[55] DA Koleva, K van Breugel: ‘Tailor-made Nano Materials
for Corrosion Control and Improved Matrix Characteristics in
Cement-based Systems’, Proc 4th
Int Symp on Nanotechnology
in Construction, Crete, Greece (2012).
[56] DA Koleva, J Hu, K van Breugel, V Milkova, P Petrov: ‘The
influence of tailored nano/micro polymeric aggregates on
material properties of cement-based systems’, J of Intern Sci
Publications: Materials, Methods & Technologies, volume 5, part 1,
pp 63-73, ISSN 1313-2539, http://www.science-journals.eu
(2011).
[57] J Hu, DA Koleva, K van Breugel:‘Microstructure analysis and
global performance of mortar with tailored nano aggregates’,
2nd
International Symposium on Service Life Design for
Infrastructure (SLD2010), 4-6, October, Delft,The Netherlands.
RILEM Publications SARL 2010, PRO 70 (2) 791-797 (2010).
[58] DA Koleva, Jie Hu, JHW de Wit, N Boshkov,Ts Radeva,V
Milkova, K van Breugel: ‘Electrochemical Performance of Low-
carbon Steel in Alkaline Model Solutions Containing Hybrid
Aggregates’, ECSTransactions, 28 (24) 115-111 (2010).
[59] J Hu, DA Koleva, K van Breugel: ‘The Influence of
PEO113
-b-PS780
Vesicles on the Corrosion Performance of
Carbon Steel in Simulated Pore Solution’, ECS Transactions, 41,
(16) 1-9 (2012).
[60] K van Breugel: ‘Is there a market for self-healing cement-
based materials?’, Proc 1st
Int Conf on Self-Healing Materials,
Noordwijk,The Netherlands, 10 p (2007).
[61] RWolfseher:‘Economical aspects of repair and maintenance’,
in P Schweshinger et al (eds) Proc 5th
IntWorkshop on Materials
Properties and Design: Durable reinforced concrete structures,
AEDIFICATIO Publishers, 33-48 (1998).
[62] C Bedard, D Sordyl: ‘Concrete summit on sustainable
development’, Concrete International,Vol 29 (7) 54-58 (2007).
[63] AE Long:‘Sustainable bridges through innovative advances’,
Institution of Civil Engineers, presented at Joint ICE and TRF
Fellows Lecture 23 (2007) www.transportresearchfoundation.
co.uk/PDF/lectures/Adrian%20Long%20paper.pdf
(This article is based on a Keynote Paper authored by Klaas van
Breugel and presented at the 37th
Conference on OUR WORLD IN
CONCRETE & STRUCTURES, organised by CIPREMIER PTE LTD.
The event,which addressed the theme ‘TheArt,Science and Practice
of Concrete’, was held from 29 to 31 August 2012 in Singapore).
The 38th
Conference on OURWORLD IN CONCRETE
& STRUCTURES will be held in Singapore, from 22-23
August 2013. It will address the theme ‘The Concrete
Infrastructure Strategies’. More information may be
obtained from the organiser, CI-PREMIER PTE LTD
(email: ci-p@cipremier.com).
BASF launches new brand for the
construction industry
BASF recently started to roll out its Master Builders
Solutions brand in Asia Pacific, as part of a phased launch
process. The global brand is a sign of the company’s
commitment to the construction industry and represents
a wide range of construction chemical solutions previously
sold under a variety of speciality brands.
The portfolio of products and services marketed under
the Master Builders Solutions brand embraces chemical
solutions for new construction, maintenance, repair and
renovation of buildings and infrastructure - concrete
admixtures, cement additives, chemical solutions for mining
and tunnelling, waterproofing, concrete protection and
repair products, grouts and high-performance flooring
products.
Master Builders Solutions embodies BASF’s ability to
collaborate across technologies and functions on a global
scale, creating solutions geared to meet the individual
construction chemical challenges of its customers.
This global brand draws on a number of successful speciality
brands such as Master Builders, Glenium and Ucrete, and is
based on a more than a century-old tradition of innovations
for the construction industry.
BASF builds on that legacy with expertise, commitment
and a customer-centred approach. In this manner, the
Master Builders Solutions launch supports BASF’s strategy
to intensify its focus on customer industries.
The know-how and experience of a global team of BASF
experts for the construction industry form the core of
Master Builders Solutions.To respond to specific individual
challenges of its customers, the company combines the
right components of its portfolio accordingly.
More than 800 customers and partners attended the
launch celebrations at locations including Singapore, India,
China, Japan, Malaysia and Indonesia. Approximately 150
customers attended the Singapore event introducing
Master Builders Solutions.
BASF’s Construction Chemicals division offers advanced
chemicals for new construction, maintenance, repair and
renovation of structures. The company’s comprehensive
portfolio encompasses concrete admixtures, cement
additives, chemical solutions for underground construction,
waterproofing systems, sealants, concrete repair &
protection systems, performance grouts, performance
flooring systems, tile fixing systems, expansion control
systems and wood protection solutions.

PROJECT APPLICATION
Machines from Wirtgen and Hamm (a member of the Wirtgen
Group) were used in the factory expansion project for Hamm
AG in Germany.
The plan was to prepare a 150,000 m2
large area, and move
around 350,000 m3
of earth in the process in only three
months. Hamm had appointed the Max Bögl Group as the
general contractor.The focus of the activity was on the brand
new Wirtgen cold recycler and soil stabiliser, WR 250, and the
Hamm H 13i earthmoving compactor with plate compactor
attachment. The innovations were convincing with respect to
performance, handling and reliability.
Wirtgen WR 250 masters heavy soil effortlessly
The first challenge was that the existing gradient had to be
smoothened out and an even surface created on the grounds
behind the previous factory. The Wirtgen WR 250 was used
while excavators removed masses of earth in the upper half, to
depths of up to 12 m, and placed around 50% of the material
onto the lower lying area.TheWR 250 is the highest performance
machine of the newWR generation and is specially designed for
the stabilising of heavy and boggy areas. Cement was scattered
in advance as a binding agent before the soil stabiliser came
into action.Thanks to its high engine performance and optimal
traction, the WR 250 was subsequently able to work its way
effortlessly through the heavy soil, which it homogeneously
mixed at a depth of exactly 40 cm.
Despite the high level of material throughput, totalling
725,000 m² of soil,the wear of the milling drum and of the drum
housing was extremely minor, which can be traced back to the
innovative drum design with the feature, among others, of the
open corner rings.
Thanks to the possibility to control the cutting rotational speed
from the cab, it was no problem for the machine operator to
react to the dramatically changing soil conditions and to flexibly
adjust the corresponding cutting drum rotational speed to the,
in some cases, stubborn, loamy and then sometimes loose soil.
In combination with the cutting drum design tailored to the
high performance of the WR 250, an exceptional mixing quality
with a forward speed, that is quite high for the soil conditions,
of 16 m per minute, was achieved.
WR 250 cold recycler and soil stabiliser in
factory expansion project
With an engine output of 571 KW / 777 HP, theWR 250 is the highest performance device of the new generation ofWirtgen cold recyclers and soil stabilisers. It
functions effortlessly at a width of 2,400 mm and at a depth of up to 560 mm through heavy and boggy soil.
Drum housing and rotor are optimally harmonised with one another.TheWR 250
thus creates high quality mixtures in a short time.The result is high daily economic
performances with hard soil.

PROJECT APPLICATION
29
High performance and operating comfort
Using the sensitive multifunction joystick on the right armrest,
the machine operator was able to simply and comfortably
control all important base functions. Automated processes,
such as automatic lowering and raising of the milling and mixing
rotor, the ergonomically designed workplace and the innovative
reverse assistant also provided enormous relief.
Max Bogl spoke enthusiastically about the performance of theWR
250, particularly highlighting the panoramic view of the machine
and construction site, the intuitive operation and the mixing result,
as well as the high daily performances of up to 15,000 m2
.
Hamm rollers reliably compress soil
Behind the soil stabiliser, the H 20i P with padfoot drum first
compressed the prepared soil. This was followed by two
compactors (H 18i and H 20i) with smooth drums. The final
sealing of the new level was carried out with the rubber-
wheeled roller GRW 280 in the new version with ‘i’ technology,
before it was covered with a 20 cm thick frost protection layer.
This was compressed with the new H 13i compactor with the
plate compactor attachment.
Signiﬁcant contributions by Wirtgen Group machines
Besides creating the area for machines and buildings, Hamm
also enlarged the testing grounds to 30,000 m2
. A SUPER
1900-2 from Vögele (also a member of the Wirtgen Group)
finally ensured the installation of several asphalt areas.
Thanks to the service offered by the Wirtgen Group machines,
the team from Max Bögl was able to complete the construction
work on schedule, in only five months. The Wirtgen WR 250
and the Hamm H 13i successfully proved their reliability in soil
stabilisation and compaction. Both devices were among the 29
innovations presented by the Wirtgen Group at bauma 2013.
Enquiry No: 08/001
In the context of the factory expansion, Hamm removed, reapplied, stabilised and compressed soil in an area of 150,000 m² in only three months.A new testing ground
with a steep hill of up to 70% gradient was also created, on which the rollers will be able to test and present their climbing ability in future.
The newWR generation convinces with even more performance, a high degree
of economic efficiency and simple handling.The mobile, glassed-in, large-capacity
cab, camera system and 90° rotating driver’s seat also ensure the best visibility
conditions with respect to the machine and construction site.
The newWR 250 mixed the previously scattered cement into the ground in layers
at a depth of 40 cm. Coming from behind, the Hamm rollers of the H series with
the HCQ Navigator ensured homogeneous compaction of all 21 layers.

PRODUCTS & SOLUTIONS
As a leading manufacturer of road construction machinery,
Wirtgen GmbH is renowned for its pioneering technologies
and innovations. With the Wirtgen AutoPilot Field Rover,
the company has now launched a technical development that
for the first time enables fully automatic, stringline-free concrete
paving. This system will enable road construction companies
to complete jobs much more easily, quickly and, above all,
economically.
The jury of the bauma Innovation Award 2013 also deemed
the AutoPilot Field Rover a pioneering development, and
awarded it the bauma Innovation Award 2013 in the ‘Machinery
Component’ category.
When monolithic profiles such as concrete safety barriers or
curbs are paved today, digital terrain models are created and
so-called stringlines are secured in the ground along the profile.
During paving, these are used by the machine for orientation
purposes - a very time-consuming method.
Fully automatic paving with the AutoPilot
Paving is much quicker with the Wirtgen AutoPilot. The 3D
control system comprises a computer that is integrated in
the machine and an intuitive control panel.Two GPS receivers
mounted on the machine communicate with a GPS reference
station on the job site.A digital terrain model is not required, as
surveying and programming is carried out on the spot.
Conventional stringline-free 3D-systems currently available on the
market can only be operated by personnel trained in surveying,
while the AutoPilot Field Rover is designed for simple operation by
the machine operator, rendering special training unnecessary.
Eliminating the use of stringlines
If a hydrant is positioned incorrectly or a gully is located 10
cm away from its marked site, with the traditional stringline
method, the user modifies the line on the job site.This is also
no problem for the Field Rover. The Field Rover comprises
a GNSS receiver and a data collector in which the software
developed by Wirtgen is installed. As during normal survey
work, the section to be paved is staked out with a plumb rod
and individual measuring points defined. The highlight of the
Field Rover is that the software calculates the optimum course
on the basis of the measured points, creating a virtual stringline,
so to speak.The data is saved on a USB stick that is then simply
connected to the machine. It is not necessary for the operator
to enter any additional data by hand.TheWirtgen slipform paver
then automatically moves to the starting point calculated during
the survey, and from there moves along the defined course.
If the concrete profile is to be paved up to existing roadway
edges, the user can calculate the optimum virtual stringline
within minutes. For the first time, it is now possible to eliminate
the conventional stringline in practical applications.
Road construction companies stand to benefit in many ways.
For example, the Field Rover lowers paving costs considerably
in comparison to conventional methods. As it bases its
calculations on the actual job site measurements and does not
rely on construction drawings, it achieves a higher degree of
paving accuracy and quality. In addition, the slipform paver can
automatically negotiate obstacles. Apart from enhancing safety
on the job site, this feature also brings further cost reductions,
as machine damage that frequently occurs when the machine
drives over obstacles is effectively eliminated.
With the AutoPilot Field Rover, Wirtgen is introducing 3D
technology for everyone.The price of the system is significantly
lower than that of existing 3D systems, as the Wirtgen system
is optimally integrated in the machine and optimised for the
respective application.This tool is also easy to use, so that there
is no need to consult a survey technician.
Enquiry No: 08/002
The Wirtgen AutoPilot Field Rover offers
beneﬁts in road construction
The AutoPilot Field Rover heralds in a new age.The satellite-supported navigation
system controls the steering and cross slope of the slipform paver automatically,
with no need for the laborious creation of a digital terrain model.
The AutoPilot Field Rover was awarded the bauma Innovation Award 2013 in the
‘Machinery Component’ category.

31

PRODUCTS & SOLUTIONS
The PURTOP range, from Mapei, is a series of continuous,
solvent-free, two-component, polyurea-based membranes,
suitable for application on various types of substrates in both
new and existing structures.
PURTOP membranes are said to have the following
characteristics:
• The ability to adapt to any shape of substrate.
• The ability to bond to various types of substrates, thanks to a
complete range of primers for all types of materials.
• Immediate waterproofing and setting, so as to permit foot traffic.
• Good tensile and tear strength.
• High static and dynamic crack-bridging capacity, even at low
temperatures.
• Considerable elongation capacity.
• Good resistance to alkalis, dilute acids and detergents.
• No requirement for reinforcement.
• No tendency to generate overloads on load-bearing structures
• Colour retention, thanks to the special finishes available, that
offer protection against UV rays.
• CE (EN 1504-2) certification.
The PURTOP range includes the PURTOP 400 M, PURTOP
600, PURTOP 1000 and PURTOP HA.
PURTOP 400 M is used for waterproofing large flat roofs and
bridge decks.
PURTOP membranes for waterprooﬁng
applications
The PURTOP range can be used to waterproof a variety of substrates including
flat roofs.

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