Latest progress of concrete compressive strength tests under Hong Kong-Zhuhai-Macao Bridge Hong Kong projects and Tuen Mun - Chek Lap Kok Link project
Regarding the alleged falsification of concrete cube test reports by a laboratory outsourced by the Civil Engineering and Development Department (CEDD), a spokesperson for the Highways Department (HyD) said today (July 7) that the HyD had completed on June 21 the non-destructive testing, i.e. Rebound Hammer Test (RHT) for examining the concrete compressive strength at the stress-critical locations of the structures (approximately 3,000 locations) under the Hong Kong-Zhuhai-Macao Bridge (HZMB) Hong Kong related projects (i.e. Hong Kong Boundary Crossing Facilities (HKBCF) and Hong Kong Link Road (HKLR)) and the Tuen Mun - Chek Lap Kok Link (TM-CLKL) project. All test results met the standard.
Meanwhile, the HyD has studied the 346 numbers of test results with abnormalities among the concrete cube tests conducted by the concerned laboratory from January 2013 to March 2017 as identified and provided by CEDD in three batches from May 28 to June 21 this year. The concrete structures corresponding to those test results include 179 above-ground or above-sea structural locations, 96 below-ground or below-sea structural locations (including piles) and 71 non-structural locations.
The HyD has started to conduct RHT at the 179 above-ground or above-sea structural locations in accordance with the recommendation made by the appointed professional organisation. As of July 5, the HyD had completed RHT at 158 above-ground or above-sea structural locations (i.e. over 80 per cent). The test results met the standard. To conduct RHT at the remaining 21 above-ground or above-sea structural locations, implementation of temporary traffic arrangement or erection of temporary platforms are required. The HyD is actively arranging with the relevant contractors the necessary temporary traffic arrangement or temporary platforms. In addition, as pointed out in the paper submitted to the special meeting of the Legislative Council Panel on Transport in early June this year and in the response to an oral question raised by members of the Legislative Council, the then Secretary for Transport and Housing stated that in order to further ensure the safety of the structures, the HyD would carry out concrete compressive strength tests on sample concrete cores. The HyD has begun taking sample concrete cores from the 179 above-ground or above-sea structural locations on June 23, and the sample concrete cores will be delivered to the Public Works Central Laboratory (PWCL) operated by the CEDD for testing. Test results will be announced after reviewed by the professional organisation.
Regarding the 96 below-ground or below-sea structural locations (including piles) corresponding to the test results with abnormalities, RHT cannot be conducted. However, pursuant to the relevant requirement under these contracts, the contractors had to take concrete cores from 5 per cent of the piles to assure that the quality of the piles complied with the contract requirement. According to the recommendation by the professional organisation, the HyD would conduct concrete compressive strength tests on these concrete cores retrieved from piles during the construction stage first (a total of 116 numbers of concrete cores had been retrieved from piles during the construction stage and three samples would be taken from each of these concrete cores for concrete compressive strength tests). As of July 5, the HyD had taken 279 samples from 93 numbers of concrete cores retrieved from piles during the construction stage and delivered them to the PWCL for conducting the concrete compressive strength tests, amongst which PWCL had completed testing on 45 samples and all test results met the standard. Depending on the test results, the professional organisation would recommend if further sampling of the concrete cores at the concerned 96 below-ground or below-sea structural locations is required; and if it is required, how the sample core tests should be conducted.
Regarding the 71 non-structural locations corresponding to the test results with abnormalities, some were involved in the construction of temporary works including temporary roads; some were used as trial mix; some were used for concrete repairing and coating, etc. As the concrete of these locations do not affect the safety of the structures under the three projects, the professional organisation does not recommend the HyD to conduct any tests at these locations.
The HyD will complete all tests related to the HZMB Hong Kong related projects, including RHT and compressive strength tests on the sample concrete cores, before the end of October. The professional organization will also complete the relevant professional assessment on the structures and submit a report to the HyD by the end of October. The HyD will ensure that the structures of HZMB Hong Kong related projects have been adequately examined, which includes a comprehensive load test on the entire 9.4 km HKLR viaduct to confirm its compliance with the design and safety requirements, before commissioning.
Ends/Friday, July 7, 2017