Lafarge - Villa Navarra

Rudy Ricciotti,
architect
Villa Navarra
Provence

03
04
08
10
13
17
P.02
Villa Navarra
Rudy Ricciotti,
architect
Romain Ricciotti,
engineer
Mouloud Behloul,
engineer
Ductal ® ,
outstanding material
Rudy Ricciotti,
architect
An architecture of confrontation
between landscape and materials
Design
A material used sparingly to meet the loads
Prefabrication
The art of moulds and pouring
Assembly
A traditional journeyman’s task
Texts: François Lamarre. Photo credits: Philippe Ruault;
Agence Ricciotti (cover, P. 08, P. 09, P. 15); Elise Sévère
(P. 09, bottom). Edited by Lafarge. Design and production:
External communication Lafarge;
VILLA
NAVARRA
DUCTAL ® ,
OUTSTANDING MATERIAL FOR
AN ARCHITECTURE OF EXCEPTION
Developed by Lafarge, Ductal ® ultra high performance fibre reinforced
concrete has innovative properties which pave the way for architectural
designs hitherto unheard of.
Its special composition gives it exceptional compressive strength,
six to eight times greater than normal concrete.
For structural applications, the use of special metal fibres provides
Ductal ® with ductile properties, hence the name: with flexural strength ten
times that of standard concrete, it can undergo substantial working stress
without shearing.
Ductal ® is easy to use, and provides an infinite number of new
possibilities. Its fluidity and the absence of conventional aggregates
in its composition enable it to adapt to the slightest detail in the formwork
and allow for the creation of extremely fine and thin forms that cannot
be obtained with a traditional concrete structure. The resulting surfaces
reproduce, with exceptional precision, the texture of the moulds.
The surface appearance can thus adopt a range of aspects, and when
polished, it can even imitate stone or marble, providing a remarkable
aesthetic finish.
Ductal ® is resistant to corrosion, abrasion, pollution, bad weather or
shocks, making for a life span 2 to 3 times longer than that of
conventional concrete.
Ductal ® is an integral part of a sustainable development approach.
Its mechanical performance, combined with its durability, its aesthetic
qualities and its high compactness help reduce the environmental impact
of construction, throughout the building's life cycle. Ductal ® requires
half as much material and energy and results in CO2 emissions of up
to half those induced by conventional concrete. It features the thermal
mass capacity of concrete which, when optimized, helps reduce energy
expenses when the building is in service.
All these features make Ductal ® a high performance and sustainable
construction material capable of the most impressive of architectural feats.
P.03

Rudy Ricciotti,
architect
- Officer of the Arts
- Chevalier of the Legion of Honour
- Laureate of the National
Architecture Grand Prix 2006
Projects and achievements
- The Footbridge of Peace, Seoul.
- National Choreography Centre,
Aix-en-Provence.
- ITER France headquarters
(International Thermonuclear
Experimental Reactor),
Cadarache.
- National Marine Testing and
Expertise Centre, Toulon.
- University of Paris VII, reuse of
the great mills, Paris.
P.04
VILLA
NAVARRA
Rudy Ricciotti has the gift of transforming all his
building sites into epics. He makes each one of his
projects into a personal struggle, into which he
soon enrols all the other actors involved in the design
and implementation.
Ifthe
building site is par excellence the heroic moment,
the struggle begins at the time of ordering, with the design
work setting the scene and shaping the guiding forces. For the
architect, it is quite literally a question of dominating matter
by shaping it. The smallest architectural project, no matter
what the scale, is thus the pretext for a conceptual joust, which
takes on epic proportions visible in the final work. The
challenge laid down to the laws of physics leaves its mark in
the design and the material and with a little imagination one
can sense the almost physical commitment of the designer.
The Navarra project is no exception to the rule in spite of the
relatively small proportions of the work. The building, half
way between a house and an art gallery, escapes mundane
domesticity through the heroic stance taken towards its
location and its description. The order from the art dealer,
Enrico Navarra, lends itself perfectly, justifying innovation
and asking for a real feat.
“The intention is for the villa to be an art
gallery, which can be visited by internet”, summarises Rudy
Ricciotti, “and it will not be open to the public. It’s an
abstract place, whose function is to constitute an enigma.”
P.05

Hidden away in the hinterland of the Var coastline, the
building achieves its objective by nestling into the
slope so as to blend into the natural vegetation of the Provencal
landscape. The desire for discretion meets here with concern
for the environment by limiting the impact of development on
the site. The principle of modesty dictates the positioning and
the form of the construction, which has a quiet profile.
The platform, cleared beforehand for the construction, leaves
the rock bare and the plot of land stripped, to be planted
tomorrow with cork oaks and cypresses. As for all the private
homes previously conceived by Rudy Ricciotti, the relationship
with the landscape is direct and frontal, accompanied by a
certain discretion, which banishes disruptive elements. The
building, positioned along the contours, is by its volumes
similar to a dry stone wall. Its firm horizontality often follows
the horizon out at sea and at other times the green and undu -
lating tide of the fronds of vegetation. Ricciotti’s houses stand
guard; sometimes they even take on a camouflaged aspect. As
for Villa Navarra, it resembles a watchman lying on the slope
of the maquis.
The confrontational attitude is accompanied by no nonsense
forms: in this case, a simple rectangle of forty metres long by
just ten wide, encompassing a volume built on one level and
doubled by a basin in the foreground that extends out into the
landscape. “The radical treatment of the house’s geometry,”
which is the architect’s signature, is masterfully interpreted in
the technical approach to the building’s construction. The Villa
Navarra practically boils down to its roof: an immense visor
stretching forty metres between the trees, a distinctive sign of
the watchman hiding deep in the woods. This cantilevered
surface of 7.80 metres opens up the house to the wild Var
landscape. Only a thin line of façade gives away its hidden
presence: an added line, blackened by coal.
P.06
FRONTAL ATTITUDE
A simple rectangle defines a volume,
established over a single level,
and doubled by a basin that extends
out into the landscape.
VILLA
NAVARRA
"The "Villa Navarra" can be summed up by
its roof structure: an immense visor stretching 40 m between
the trees, a distinctive sign of the watcher
in the shadows."
P.07

P.08
An architecture of
confrontation
between landscape
and materials
VILLA
NAVARRA
If discretion is the order of the day and the planned use virtual
via internet, the construction itself is not at all virtual! The work
is very real; it is even highly concrete and reeks of effort and
applied physicality, as the architect is wont to say in imaginative
terms.
Under his leadership, the project took on an innovative dimension,
which made the undertaking exciting: an exploration of
materials, namely ultra-high performance fibered concrete
Ductal® developed by Lafarge. By concentrating on the roof,
the project gave itself a structural challenge, going beyond the
dimensions of the plan to take on the status of a work of art.
Applying civil engineering to this scale of project is the first
achievement of the architect; the second lies in the way he
ROMAIN RICCIOTTI
Structural engineer.
MOULOUD BEHLOUL
Concrete engineer at Lafarge .
executed it. The art dealer was clearly inviting the architect to
indulge in a veritable creative act. This is how a work of art will
tomorrow house other works of art, going beyond a question
of format by the nature of the questions posed and the intensity
of the thinking. The creative spirit which took over the
construction makes architecture the reflection of the arts and
broadens the builder’s scope, both in and calling the tune.
The project, as executed, is thus almost a prototype and its
execution a case study. Mouloud Behloul, the engineer in charge
of the Ductal® development at Lafarge, points out that “the roof
was the opportunity for all of us to think about a structure
working mainly through flexing, due to the cantilever which
typifies it and with no pre-stressing, the engineer’s normal
approach, in order to thoroughly test the qualities of the
material.” An approach even more unheard of and singular than
that of the footbridge in Seoul, the architect’s first project
undertaken with Ductal®, of which the single 130 metre arch
naturally only works by pressure and makes use of pre-stressing
to reinforce its voussoirs and optimise performance. At
Villa Navarra, the 7.80 metre cantilever makes the roof one of
a kind and its execution in Ductal© is a world first.
P.09

DUCTAL ®
The material was used 100%
for the roof structure, making the most
of all its properties.
P.10
DESIGN
A material used
sparingly to meet
the loads
VILLA
NAVARRA
Composed of 17 juxtaposed panels, the roof of the
Villa Navarra makes full use of Ductal®’s qualities. The
material is used 100%, as if left to its own devices, with
no other assistance than traditional reinforcing placed at the
upper part of the ribs. Even then the reinforcing is mechanically
redundant, used in the end as a safety measure, just as the
safety net protects the performing acrobat.
The roof, of optimal design and structure, makes use of a design
that faithfully follows the load lines with great economy of
means. “The material is placed exactly where needed in order
to be able to express itself,” enthuses Mouloud Behloul.
The architect’s son, the engineer Romain Ricciotti arrived at the
form through painstaking drafting, dictated by all manner of
constraints, starting with the most pressing: getting all the
materials to the building site in the middle of the countryside.
The road network is, therefore, the first factor behind the dimensions
of the roof, composed of modular, pre-fabricated parts.
The final module is a panel measuring 9.25 m x 2.35 m, whose
design is suitable for the spreading of the load in the planned
structure, which is made up of a plate of a constant thickness
edged by two lateral progressive inertia ribs, higher at the
supports and becoming gradually thinner, meeting the thickness
of the plate at the far ends. The ends have a clever open
design to save weight and to allow the light to enter this part
opened up as a porch. “The design produces an optimal
mechanic, which is not without similarities to steel forms, comprising
a web, wings or a purlin,” comments Romain Ricciotti, “and
this form is not the result of any particular design feature.”
A specialist in mathematical modelling, the young civil works
engineer almost goes on the defensive about having held the
pencil. “Structures behave as conceived and calculated,” points
out Mouloud Behloul, who accepts the pre-defining of the shape,
namely a plate edged by lateral ribs, “in as much as a structure
never imposes itself and is always a matter of choice,” so says
the engineer!
The decisive factors behind the size of the roof panel are, therefore,
its own weight, the allowable overload due to weather,
wind resistance and heat expansion, which it is likely to suffer
in a region subject to high amplitudes linked to sunshine and
high winds. These amplitudes are all the greater, as the surface
of the un-insulated roof is left bare, benefiting from the finished
look and the waterproof qualities of the Ductal® panels.
PRE-CASTED MODULES
The extremity of the modules
is open to add weight and make use the
light in this part with an open top.
“The aim to
reduce the impact
of the villa
on the site led
to the use of an
ultra-thin roof
made of Ductal®
which comes
to a thickness of
3 cm at its tip.”
P.11

THE LINE OF EFFORT
The module is formed by a panel
whose design matches the distribution
of effort in the structure.
THE DESIGN
The design produces optimal
mechanics, which recalls the design
of steel profiles.
P.12
“Ductal®, as a
new material,
challenges
all the usual
methods of
calculation.”
VILLA
NAVARRA
Heat expansion is by far the most difficult to predict. The
highest expansion recorded due to variations in temperature
can be as much as 5 mm and, when the calculations give a
theoretically doubled value, as much as one centimetre. Ductal®,
as a new material, challenges all the usual methods of calculation.
The delicate lines made possible by the material mean that
the engineer must ask himself all manner of questions never
heard of with buildings in traditional concrete, particularly
questions about expansion and twisting. “The calculations
themselves are ordinary” says Mouloud Behloul, “but it’s the
approach that is not, above all for concrete.” The thickness of
the slab to resolve the problem of twisting has been measured
at 35 mm, “a sheet of paper in terms of concrete!
Originally designed for post-stressing, the panels would not
have been very different, apart from necessarily being firmly
anchored, as dictated by post-stressing. Entirely made of UHPFC
Ductal® and reliant on this one type of material (except for the
fixed reinforcing which was eventually placed in the ribs), the
panels lie in a more traditional fashion on two longitudinal
beams, placed 1.50 metre apart, forming a technical gallery.
Supporting braces, made up of a rod inserted in a socket
injected with resin and bolted at the surface with a wing nut
holding in place a load spreading plate, are placed along the
back beam. For the second beam, simple neoprene cushions
form the support.
PREFABRICATION
The art of
moulds
and pouring
This choice, apart from the experimentation with
materials that it affords, corresponds to a conscious
choice of building method. Rudy Ricciotti is enthusiastic
about the combination of a high tech product, as represented
by Ductal® and industrial prefabrication, with traditional
fitting without the constraints of the sophisticated processes
necessitated by pre-stressing. If the formulation of Ductal®
belongs to the world of the very latest highly sophisticated
technology, its use is gradually becoming less dependent on
laboratory culture, becoming known for real operational performance
on the bulding site. Traditional fitting gives this innovative
product, the result of ten years of research, a shared and
mass appeal, which finally allows one to foresee mass usage in
the short term. This “schizophrenic” relationship between
production and fitting fuels the architect’s hope of seeing this
family of concretes quickly becoming a material used by masons.
The first stage in the process, prefabrication, still relies
on the experimental culture necessitated by the material.
The theory is already tainted by empiricism, having benefited
from the expertise of the precaster, namely the Bonna Sabla
company, located near Montpellier, France. The production of
the mould and the method of pouring are determining factors
for the production of these parts with elaborate and complex
shapes, which also have a finished surface. The technological
requirements are satisfied by the metal moulds which are
produced by an aeronautics industry supplier. “In this way, two
different industrial worlds, which normally are not aware of
each other, are brought together in the manufacturing process,”
notes the architect.
TECHNOLOGICAL REQUIREMENTS
The manufacture of the metallic
moulds was performed by a supplier
from the aeronautical industry.
P.13

“The direction of the metallic fibres
used in Ductal® requires a methodical
and skilled approach.”
P.14
VILLA
NAVARRA
THE EXPERTISE OF THE PRE-CASTER
The pouring method is vital in obtaining
the elaborate and complex forms.
Neither is it by chance that the next steps have something in
common with aeronautics, notably through the run-off of
liquids. The direction of the metallic fibres that make up Ductal®
is not the least mysterious of the phenomena observed when
manipulating the material, requiring a methodical and skilled
approach. The mechanical performance being dependent on the
direction of the fibres, it is essential to determine the pouring
process which will align the needles in the direction of the flow
of liquid. The extremely fine texture of these concretes, of which
the largest particles reach only 0.5 mm, facilitates this hydraulic
behaviour, which conditions the mechanical direction of the
needles carried by the flow.
“Proportionate to the other constituent parts which make
up UHPFC’s, including silica fume, these fibres play the
same role as reinforcements in traditional concretes,” notes
Mouloud Behloul to explain the extraordinary resistance obtained
by these clever formulations of which certain components are
kept secret. For the production of the Villa Navarra panels, the
moulds were set up back to front, pouring was carried out longitudinally
for the profiled ribs on the edges and transversally for
the plate, as witnessed by the oblong gaps retained at the ends.
The checks carried out on the first prototypes showed the well
founded basis for this method, with the fibres always correctly
aligned. “This is choreography for materials,” notes Rudy
Ricciotti, who is in wonderment over the “huge gap that exists
between the minuscule scale of the fibres and the 7.80 metre
cantilever that the calculations allow for.”
The turning out of the mould carried out next happens after
steaming at 90 °C for a more rapid curing of the concrete. It gives
a smooth and shiny surface, of which the burnishing is accentuated
by the darker tones caused by the fines used in the formulation
of the concrete.
P.15

P.16
VILLA
NAVARRA
ASSEMBLY
A traditional
journeyman’s
task
With the on site assembly of the panels, the epic
story of the roof runs into the traditional world
of construction, its ups and downs and its constraints.
The architect is in his element, caught between his fascination
for the latest technology in materials and his ancestral attraction
for the building site and the men who work there.
The magic of this roof with its pronounced cantilever was not
immediately obvious. Apart from the opinions sought after
beforehand from experts in the field, in particular Jacques
Resplendino, the Setra engineer who compiled the standard for
UHPFCs, the assembly was subject to a methodological
approach also involving the stone mason Ortunio. The installation
of these panels weighing approximately 3 tonnes each
and brought by lorry to the plot, was at times epic, “similar to
the passage of the ship over the hill in the film Fitzcaraldo by
Werner Herzog,” comments the architect with hindsight. “Mutual
trust was created from one end to the other of the chain, making
the operation a story of fellowship,” he likes to say.
Lifted by a field crane, the panels were positioned on the two
supporting beams, then pushed against the preceding one by
being slid sideways and finally propped. They are joined by
mortise and tenon at the bulge in the ribs by the positioning of
a socket subsequently injected with resin. The fixture to the back
beam is achieved by the previously mentioned sunken braces,
LESS IS MORE
The precast and the work site are forgotten;
the roof structure dominates the landscape
and is reflected in the water.
P.17

working in traction, whereas support is provided entirely by the
interior beam, equipped with neoprene.
In order to avoid any tapping in the façade between these juxtaposed
panels, similar to giant tiles placed edge to edge, a system
of transversal axes in the form of a steel rod anchored in the
lifting points at the ends of the panels and sealed by a resin,
reinforces them. A silicon joint, placed later, guarantees waterproofing
of the upper part of the ribs, which are thus joined and
reinforced.
The old fashioned part of the procedure and the fixing by simple
metal bolts contrast with the sophisticated technology which
preceded the development of this new type of plastic material
and the manufacturing of the panels in elaborate shapes.
It is in the ability to express these two worlds, of industry
and of tradition, that the greatest sources of innovation
for Ductal® reside, as for those builders who choose to allow
this strange material to “talk”.
The major work finished and the landscape growing back around
it, there are no signs of this epic undertaking. The epic moments
of the prefabrication and the building site are forgotten, leaving
the roof to reign over the landscape and to reflect in the waters
of the pond, henceforth frozen in harmony, still and as if at peace.
P.18
VILLA
NAVARRA
A VIRTUAL TOUR
The structure is quite real;
a strong materiality which exudes
the effort and physics applied,
as the architect puts it.
"Mutual trust
was created
from one end
to the other of
the chain, making
the operation
a story
of fellowship."
P.19

Lafarge
61, rue des Belles Feuilles - BP 40
75782 Paris Cedex 16 - France
Phone: +33 1 44 34 11 11
External Communications
Phone: +33 1 44 34 58 30
Fax: + 33 1 44 34 12 00
www.lafarge.com