Ascent Facilities Engineering Pte Ltd

3rd ACF International Conference on SUSTAINABLE CONCRETE TECHNOLOGY AND STRUCTURES IN LOCAL CLIMATE AND ENVIRONMENT CONDITIONS

2008, Ho Chi Minh City, Vietnam

A durability investigation of a 30 year old barge pier structure located in a tropical marine environment was carried out. The principal problems reported were spalling and cracking of concrete on the reinforced concrete under-deck and pitting corrosion on the steel piles. The occurrence of spalling on the under-deck was found to be fairly widespread and principally due to ingress of chlorides from the sea water, with the strong likelihood of a compromise in structural integrity if no remedial action was taken. Further, high potential differences were measured on the under-deck in areas where no spalling had occurred, indicating the likelihood of ongoing corrosion and its possible future culmination in the form of more delamination and spalling of concrete. The pitting corrosion of the steel piles was found to result in a reduction in the cross sectional area, thereby affecting the load carrying capacity of the piles and consequently the stability of the entire structure. Using the measured profile of the chloride concentration levels, a service life prediction of the time to initiation of corrosion and cracking was carried out in order to provide a predictive indication of the stage to which the deterioration of concrete had reached. Different rehabilitation options including conventional patch repairs and cathodic protection were then considered. Tradeoffs between costs and frequency of repairs were examined for the different remedial options through a life cycle cost analysis to determine the most cost effective option.

10th International Conference on INSPECTION, APPRAISAL, REPAIRS & MAINTENANCE OF STRUCTURES

2006, Hong Kong, CI-Premier Pte Ltd

A condition assessment of the façade of a commercial building was carried out through a desktop review and detailed investigation. The principal problem reported was delamination of the mosaic tile and render layers from the precast concrete cladding panels forming the façade. The detailed investigation programme involved i) field testing consisting of delamination survey, in-situ bond strength tests and extraction of core samples, ii) chemical analysis to determine mix composition, iii) petrographic examination of tile/render/concrete layers and iv) infra-red thermal imaging survey.
About 15% of the façade area was found to be delaminated indicating the build-up of stresses induced due to differential expansion/contraction within the underlying layers of the façade. Low bond strength and areas of thermal anomalies were reported at some locations. Many occurrences of the delaminated areas were adjacent to the expansion joints between the precast concrete panels reflecting the inability of the tile and render finishes at the joint to accommodate movement.
To alleviate the above concerns, the application of a protective system was proposed after repairs to the delaminated areas and the expansion joints. This system involves i) anchoring of the façade to strengthen the composite layers and ii) fixing of a mesh and binder to act as a holding layer for the existing tiles. Finite element modeling and analysis of the proposed system was carried out to evaluate its effectiveness. Analysis was carried out under different loading regimes comprised of gravity and wind loads. The resistance offered by the repair system was found to be adequate enough to resist the maximum pull-out and shear forces anticipated on the façade in the event of future delamination.

Department of Building, School of Design and Environment, NUS

Public Lecture No. 3, 2002

Singapore Concrete Institute

Course on Assessment and Repair of Concrete Structures

CIDB / SCI / TAS Tiling & Waterproofing – Beyond Year 2000. What lies Ahead?

BAUCON ASIA, 1997

Management for Excellence Programmes

Sealing and Resealing of Buildings, July 1997

Taywood Engineering Limited (TEL), were engaged by the owners of the OCBC Centre to evaluate the condition of the sealant between granite panels forming the external facade of the OCBC Centre. Approximately 66,000 m of sealant were used as jointing material in the 51 storey building completed in the late seventies. This paper highlights the investigation procedure, survey findings, the recommendations proposed and finally the execution of the resealing process.

UNDP / RCA / IAEA Training Workshop on Non-Destructive Examination of Non-Metallic Materials

Singapore, August 1996

Tile Association of Singapore

Failure of Tiled Facades