Case Studies

 

Sau Mau Ping Estate Redevelopment Phase 5

  

 

Notable Features
 
bullet Construction waste reduction program
bullet Use of factory manufactured precast concrete elements
bullet Application of large panel steel formwork
bullet Use of drywall for the internal partitions
bullet Use of precast facade
bullet Use of precast staircase
bullet Use of precast cooking bench
bullet Use of prefabricated door sets
bullet Application of ISO 14001:96
bullet On-site sorting of waste
bullet Site office erected with metal panel
bullet Reuse of surplus steel bars
bullet Reuse of large panel timber
bullet Reuse of pallets for supporting blocks
bullet Reuse of concrete test cubes

Basic Information
 
bullet Location: Sau Mau Ping
bullet Building Type: Residential 
bullet Contract Period: 31 July 1998 – 30 October 2000
bullet Gross Floor Area: 139,974m2
bullet Client: The Hong Kong Housing Authority
bullet Quantity Surveyor: Davis Langdon & Seah (HK) Ltd.
bullet Main Contractor: Hip Hing Construction Co. Ltd.
bullet Contract Sum: HK$ 687 million

Overview
 
The Sau Mau Ping Estate Redevelopment Phase 5 was a residential building project and the following major items were executed under this contract:
 
bullet Three Harmony 1 Blocks with 2397 flats
bullet The Blocks were 40 storey in height
bullet Day nursery on G/F of Block 5
bullet Kindergarten on G/F of Block 6
bullet Associated drainage and external work
 
 

  Waste Management
   
  bullet Waste management plan
   
  For the purpose of identifying opportunities and achieving continual improvement on environmental performance through a systematic approach, Hip Hing Construction Co. Ltd. has documented and maintained an Environmental Management System (EMS) conforming to ISO 14001:96 requirements. The Project Manager would at every 6 months interval review and evaluate compliance with relevant environmental legislation and regulations. Issues related to waste management such as segregation of good and reusable material as well as avoidance of unnecessary wastage resources are also included in the EMS manual.
   
  bullet On-site sorting of waste
   
  On-site sorting of construction waste was partially performed. Distributed Separation was adopted. The waste was separated at the respective floors and then transported through refuse chute to the ground floor at the appointed time. Paper, can but not rubble had been sorted out. Large panel timber and surplus reinforcement were transported to ground floor by tower crane.
   
  bullet Material Control
   
  Construction waste was expected to arise from three major causes, namely careless handling of raw materials, excessive or incorrect mixing of concrete, damaged or defective precast components. For example, defective rate of precasting was less than 0.1% according to experience of the contractor. Timber formwork was also a waste source but the quantity was reduced. The surplus material for dry wall was also controlled. Tiling was considered to be the most waste producing. The wastage was generally 5%, but with dimension co-ordination and sound waste management, the wastage could be cut down to 3%. Sanitary fitments were installed at the later stage to prevent damage by the workers.
   
  bullet Reusable materials
   
 
bullet Site office erected with metal panel – it could be erected within two weeks
bullet Large panel timber
bullet Surplus steel bars were stored for reuse
   
  bullet Pallets for supporting bricks or blocks
   
 
   
  bullet Concrete test cube
   
  It was used as footing for fencing and then transported to other site for reuse.
   
 
   
 

  Contact of Contractor
   
  Hip Hing Construction Co. Ltd.
  29/F, New World Tower, 16-18 Queen's
  Road Central, Hong Kong
  Tel: (852) 2525 9251
  Fax: (852) 2845 9295
   
 

   
Wall System
 
Large panel construction in the form of wall formwork was used for casting the structural shear walls. This saved time in erecting, striking and re-erecting the timber formwork as the steel formwork was handled as one unit. In addition, the timber formwork can be reused for a maximum of eight times as required by The Housing Authority, while the steel formwork can be used for erecting the whole block. However, traditional timber formwork was adopted to cast the floor slabs due to the lack of storage and working space. 
 
 
The concreting cycle for one floor was 6 days. This was the optimum speed as the tower crane had been fully occupied for transportation of materials. This speed was considered to be the same as the speed using traditional method. 
 

Dry Wall
 
‘YTong’ dry wall system was used to form the partitions of the flat. YTong Autoclaved Aerated Concrete (AAC) is manufactured from sand, lime, PFA, cement, water and aluminum powder. It is composed of calcium silicate hydrates and many small pores. The accuracy of YTong size can easily be controlled because the size of the product will not vary after casting. Also, the shrinkage of YTong product is small which is only up to 0.055%. In addition, this product is very light – the density of which ranges from 400-700kg/m. It can be cut into different sizes according to dimension requirement by simple equipment such as hand saw or electric cutter. It has the advantage of easy assembly or dis-assembly to give a flexible layout to the flat without any concreting process which will produce waste. 
 

Precast Facade
 
A casting yard of 100m by 6m was set up on site. Steel formwork maneuvered by a traveling crane was used instead of the conventional plywood forms. The facade formwork was turned face down onto the ground. The steel window frame together with the reinforcement bars were fixed in the formwork. Concrete was poured into the formwork and troweled flat. Simultaneously, concrete cubes were made for strength testing and strength control. After the concrete had set for 7 days, the horizontal steel formwork was erected upright. After a further 14 days, the formwork could be demounted. Spatter dash was applied on the overhang portion where mosaic tiles would be applied and other portions were left smooth for spray painting.
 
 
The finished facade was then moved to another area for storage until a tower crane lifts the facade to erect on the Harmony Block. Although steel formwork is more expensive than timber formwork, the steel formwork is more durable than timber formwork. In addition, a better quality finished facade is achieved by prefabrication on the ground. Therefore, it is cost effective to use precast facade in mass production.
Precast Staircase
 
Another interesting feature is the precast staircase which was constructed in 8 risers. The half landing was casted separately as in-situ part. Due to the smooth surface quality, no applied finishes would be necessary. A metal nosing strip was the only thing that was required to finish the stair. Naturally, construction waste would not arise.
 

 

 

Precast Cooking Bench
 
Cooking benches were also pre-fabricated elements. Bench top was cladded with 1 piece 0.8mm satin finish stainless steel sheet. The bench itself was of lightweight concrete and supported by 60mm concrete support, smooth finish and epoxy painted. The stainless steel sink was cast in lightweight concrete bed, 75mm thick, to afford strength to stand chopping and cutting. Earthing lugs were designed and built for both sink and bench.
 

Prefabricated Door sets
 
Prefabricated door frames and doors were used in this project. These door sets saved the temporary timber support for door frame, thus reducing waste.
 
 

 
 

Low-Waste Buildings Technologies & Practices
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