The unique façade of an office complex in Doha/Qatar is

designed and built with a UHPC. The 3-D shaped panels

have visible surfaces from all sides and span up to nine me-

tres in length. The elements have been designed, produced

and built by Doha Cladding Solution, a local prefab plant.

The Emir of Qatar emphasises the creation of a solid infras-

tructure in which medium-sized enterprises of non-oil related

industries can prosper and grow. Adjacent to the international

airport of Doha, a complex of four office buildings was

planned as a new headquarter for the company Manateq, the

leading developer within Qatar. Laceco architects and engi-

neers from Lebanon won the international design competi-

tion. The design was conceived as a composition of four in-

verted cubes sheltering an internal oasis. The outside of the

iconic building should reflect the brand of Manateq and re-

interpret traditional Qatari architecture using a modern lan-

guage. The headquarters’ parametric façade was inspired by

Manateq’s logo and optimised daylight in the offices. To

achieve a long-lasting, high-quality, and low-maintenance

performance, an ultra-high-performance concrete (UHPC)

was selected.

Requirements

The façade elements were produced within Doha where the

material was adapted to local climatic conditions (corrosion,

dust, etc.). The single panels had a length of about 9 m and a

width of about 3.30 m. All panels are visible from the outside

as well as from the inside (offices), therefore all sides needed

to be out of fair faced concrete. Because of the groove on

both sides of the curved panels, production was done in

vertical GRP-moulds using self-compacting concrete.

The contractor selected for the shading elements was Doha

Cladding Systems (DCS). In 2015 the owner family and the

management of DCS decided to step into the business of

UHPC façade-elements. After an intense market research, the

engineers refused to buy ready dry mixes of concrete as a

black box. With the high-performance binder Nanodur sup-

plied by Dyckerhoff, DCS was able to produce in house a

UHPC mix within short notice and adapt the recipe to varying

requirements such as the moulds, mixer, temperature, change

of raw materials, strength, flowability and ductility. DCS had

to perform a tough prequalification to get the job.

CONCRETE TECHNOLOGY

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UHPC shading elements create an iconic building in Qatar

durcrete GmbH, Limburg, Germany

� Bernhard Sagmeister, durcrete GmbH, Limburg, Germany

2

Manateq Headquarter, overview

© DCS, Mr. Ayman Badr

The client had to be convinced, by testing of specimens and

building a mock-up, that all the requirements of the tender

were fulfilled.

Structural Design

The structural analyses for the UHPC elements, as well as for

the fastening to the steel construction were in the responsi-

bility of the subcontractor. It was performed by a local engi-

neering office in Doha using British standards.

Each panel is connected directly on the steel back frame

using a simple support. The connection is designed to avoid

stress caused by temperature elongation in the concrete ele-

ment as well as strain due to different deformations between

the steel frame and the elements. As maximum permanent

deflection a value of span/35,000 and as maximum wind load

deflection a value of span/15,000 was calculated, which

means nearly no deformation occurs. The elements are cal-

culated with a linear elastic calculation in an uncracked state.

The maximum tensile stresses due to dead weight and wind

are compared with an admissible strength of 5 MPa.

CONCRETE TECHNOLOGY

www.cpi-worldwide.com CPI – Concrete Plant International – 3 | 2020

� Dr.-Ing. habil. Bernhard Sagmeister studied civil engineering.

After working as a structural engineer and site manager, he was

the managing director of several precast plants. In 2010 he

founded the company durcrete, which deals with consulting,

development, analyses and sale of products made from UHPC

with the binder Nanodur. He gives lectures at the Technical

University Kaiserslautern/Germany. sagmeister@durcrete.de

3

Because the Nanodur UHPC has a minimum flexural tensile

strength of the uncracked concrete of 15 to 25 MPa, there is

a safety factor of γ ≥ 3.0. Based on experience of the last ten

years with this material, this was enough to avoid uncertainties

of the load, material, decrease of tensile strength due to tem-

perature and humidity, fatigue and other influences. Fibres

and reinforcement within the UHPC may increase ductility,

tensile and compressive strength. None of these additional

factors were taken into account, the design was done with the

pure flexural strength of the UHPC cement stone. In doing so,

the concrete remains uncracked and the optical characteris-

tics remain perfect. The given wind load on the UHPC-ele-

ments was accounted for in X and Y-direction and dimension-

ing was done with asymmetrical bending.

The connection between the UHPC elements and the steel

support allowed movements up to 5 mm in order to avoid

thermal strain. Because of the tolerance compensation during

the erection no embedded threaded sleeves were employed.

The M12 stainless steel bolts were undercut anchors with a

length of 120 mm. The anchors were drilled and installed at

the site. Intensive testing was required to ensure the ultimate

loads in various directions. The panel thickness of the in-plane

shear connection was only 130 mm.

Recipe The specifications required a UHPC with a strength of more

than 150 MPa and a flexural tensile strength of the uncracked

concrete (strength of concrete paste, limit of elasticity, mod-

ulus of rupture) of minimum 12 MPa. The Young´s modulus

has to exceed 55,000 MPa. Deviations, bowing and warpage

due to production and shrinkage was restricted.

DCS selected Nanodur Compound 5941 as a UHPC-binder-

premix of Portland and slag cements, additives and quartz

flour. Instead of silica-fume or metakaoline, very fine cement

particles as well as synthetic oxides are used to fill the gaps

between the cement particles and to influence the hardening

process. This resulted in very smooth, flowable and self-com-

pacting UHPC mixtures, which did not need a thermal treat-

ment. The binder and admixtures were imported from Ger-

many, aggregates from India, and the steel fibres from China.

The basic recipe was designed and tested by the central lab-

oratory of Dyckerhoff Gmbh / Germany, the supplier of the

binder. After a short period, DCS was able to adopt the recipe

to its different needs.

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Manateq Headquarter, building edge

© D

CS

, Mr.

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© DCS, Mr. Ayman Badr

Manateq Headquarter, building site at night

Production All fine particles of the recipe are pre-mixed in a high inten-

sive cement mixer within the cement plant. Thus, a simple

pan-mixer in the prefab plant was sufficient and no special

equipment was necessary. The mixing time depends on the

PCE used and is normally between 8 to 10 minutes per batch.

At temperature of more than 30 °C, most PCEs lose their ef-

fectiveness, so the material needed be stored inside, away

from sunlight. High intensive shear mixers do not shorten the

required mixing time or improve the result, but very often

cause problems because they entrain too much air and en-

ergy, which heats up the mix. The Nanodur binder was deliv-

ered in big bags and dosage of all ingredients was done by

CONCRETE TECHNOLOGY

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Nanodur Compound 5941 1,320 kg/m³

Special aggregates size 3 to 5 mm 312 kg/m³

Special aggregates size 1 to 3 mm 864 kg/m³

Quartz sand from India 0 to 2 mm 160 kg/m³

Superplasticizer Type PCE 26 kg/m³

Shrinkage reducer 16 kg/m³

Steel fibres 70 kg/m³

Water 160

Compressive strength on cubes

10x10x10cm³, age 56 days,

stored under water

> 180 MPa

Flexural strength on prism,

age 56 days stored under waterup to 25 MPa

Table 1: UHPC recipe and test results

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Manateq Headquarter, testing of fasteners

hand. Concrete was delivered in buckets or with a wheelbar-

row. The surface quality of the elements and the deaeration

of the concrete improves with the flowpath of the self com-

pacting concrete.

The challenge in production is not the recipe or the mixer, the

crucial task is the construction of the mould. The mixture with

a lot of fine particles gives an exact mirrored picture of the

mould. Every imperfection will be visible in the element. Air

bubbles rise to the top and solidify at corners or platforms

within the mould. Shrinkage of the concrete over the entire

length leads to deviations of measurements, which may fall

outside the given tolerances. All inner formworks and cores

were restrained due to shrinkage pressure of the concrete.

Thus, the cores are constructed in a soft flexible manner in

order to facilitate the demoulding and avoid cracking. How-

ever, the formwork could not be too flexible given the strict

tolerances requirements.

DCS used glass fibre reinforced plastic GFRP for the construc-

tion of the mould. This material is lightweight, and allowed for

the moulding and demoulding procedure to be done by

hand without the use of a crane.

Binder

The binder Nanodur Compound is a mixture of a special ce-

ment preblended with fine sand, where defined particle size

ensures an optimized grading curve. Concrete with this

binder has a superb tensile strength and the steel fibres bond

well in the cement matrix. Typically, the material is used for

self-compacting concretes produced in prefab plants. Nan-

odur Concrete is mainly used in technical applications where

an uncracked state of the concrete is required. The German

consultant and engineering office ‘durcrete’ also offers an

‘UHPC-Additive’. This product is designed for the construction

industry e.g. ready-mix concrete, where high compression

strength of reinforced elements is required as well as GFRC-

industry where a high density of the material is requested.

�

CONCRETE TECHNOLOGY

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durcrete GmbH

Am Huttig 4

65549 Limburg, Germany

T +49 6431 5840376

sagmeister@durcrete.de

www.durcrete.com

DCS Doha Cladding Solution

Member of Al Mohannadi Group

New Industrial Area P.O. Box 220, Doha, Qatar

www.dcs-qatar.com

FURTHER INFORMATION

Manateq Headquarter, dosage of mixing material Manateq Headquarter, pouring of panel©

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