Brimming with curiosity, the elephants at Zurich Zoo moved into their new domicile this spring after a long, patient wait. Extending over more than 11,000 m2, the Kaeng Krachan elephant park offers the zoo’s giants a species-appropriate habitat six times the size of their previous home.

TECHNICAL EXPERTISE AT ITS MOST SUBLIME FROM FOUNDATIONS TO ROOF

The centerpiece of the Kaeng Krachan elephant park is the 6,000 m2 elephant house, containing a state-of-the-art tract for the elephants to withdraw to, as well as facilities utility services and plant rooms. Boasting superior construction quality and cutting-edge technical installations, these areas ensure the efficient running of the facility and the wellbeing of the elephants.

Flooring and waterproofing in one

Concrete technology, waterproofing and flooring had to satisfy the most stringent requirements. The floors needed to be absolutely watertight, durable, resistant to excrement, food remains and other waste matter, as well as very easy to clean.

All-round protection for the technical installations

Rainwater from the roofs is collected in concrete holding tanks. As an integral part of the static concrete structure, these tanks also have to be absolutely watertight. Fast-curing Sika polyurea technology was selected as the main solution for waterproofing and lining. Sikalastic® technology is the tried and proven answer when it comes to waterproofing and durability. Joints and cast fixtures to attach dividing grills, doors and other structural components were, if necessary, treated with additional sealants such as the Sikadur-Combiflex® system. This ensures all-round protection for the technical installations in the basement plus high-grade lining in one.

The roof as star attraction

The imposing roof spans up to 80 m at its longest and requires no additional columns inside for support. Designers and engineers faced the most exacting of challenges in terms of statics, construction physics and materials. Employing a prototype waterproofing solution, the roofing contractors achieved a master stroke with this free-form roof design. With roof slopes ranging from 0 to 55 degrees, maximum safety precautions were called for, including workers being roped up at all times.

Successfully applied by customers for over 25 years, the Sarnafil® TG roofing membrane system was fully bonded to the Duripanel boards that make up the substructure. The plasticizer-free TPO roofing system was felt-laminated on the underside to completely bridge the joints in the substructure. Flooded with light, the hall has 271 roof lights, each with a different shape. All of the upstands and approximately 1,500 corner sections had to be constructed by hand due to the various angles for which standard profiles were not available.

To meet the high aesthetic requirements and also to create a safe working level, a continuous timber platform was designed to span the roof 50 cm above the Sarnafil® waterproofing membrane. This timber structure is set on 5,615 supports. The base of each support is enclosed in a maintenance-free Sarnafil® T fitting that was specially developed by Sika.

Strictest of concrete specifications for prestressed ring beams

The ring beam is structurally the central link between the actual timber roof shell and the abutment areas and provides support for the roof shell. The huge loads from the timber shell are absorbed circumferentially by the prestressed, free running concrete ring beams and are transferred to the ground at three low points in the facade through specially piled foundations.

Rigorous concrete specifications were stipulated for strength development, self-compaction, low shrinkage and optimum installation within defined minimum time frames. In order to satisfy these requirements and enhance installation, Sika® ViscoCrete® technology was used to achieve optimum concrete flow, compaction and ultimate strengths. The well-proven and reliable reducing agent Sika® Control-60 was used to lower shrinkage and so increase durability.

The concrete technology behind watertight concrete

Some of the areas below ground are built up to 7 meters deep into a slope. To prevent a serious risk of ground water penetration, the entire basement had to be waterproofed. Since the framework is built as a watertight in situ concrete structure, the concrete serves not only as a load-bearing medium, but also as a waterproofing barrier.

The main excavation also required a high degree of slope stability, with sprayed concrete sides and pile walls. Sika supplied the engineer and building contractor with Sika® ViscoCrete® admixtures and Sigunit® sprayed concrete accelerators for optimum performance and rapid completion of the sprayed concrete walls between the piles.

A facade with perspective

The facade was designed to ‘speak’ the same naturalistic architectural language as the roof, while remaining an autonomous element in its own right. The roof deformations in the wide-span high areas between the load-transferring low areas meant that elastic, movement-accommodating, airtight bedding for the glazing was necessary to prevent stress and unwanted constraints on the glass panels. Sika adhesives and sealants were used for structural bonding of the overhead glazing in adapted profiles, as well as for sealing and UV-resistant bonding of the insulated glazing for the edge seals.