Concrete core tests

The contract required core tests to be conducted on 5 percent of all piles to verify their length and the integrity of the concrete. These tests are both costly and time-consuming, and all core samples extracted from the piles must be kept in a secure place to avoid any tampering.

In fact, many of the core samples in these boxes had already been faked. The site agent
explained that if a core sample contained mud and debris or showed honeycombing, he would simply ask his subordinates(site foreman and assistant engineer)to have the workers extract a replacement core sample from a pile of known good quality. The workers responsible for core extraction agreed that these were indeed the instructions they had received.

The site agent
assembled different cores extracted from piles of the correct quality to replace poor quality cores obtained from the substandard piles. By measuring the total length of the cores, including the counterfeit ones, he falsified core sample records, thus concealing the existence of the substandard piles. The workers who extracted the core samples told investigators, however, that Hui Hon staff put the boxes of extracted core samples in unlocked boxes in the car park outside HD's site office. This arrangement could have provided ample opportunities for changing the core samples.

When more than the stipulated quantity of cores had been extracted from a pile that was up to standard, the number of drill holes in that pile could have aroused suspicion. The site foreman
said that his supervisor (the site agent) asked him to cover any superfluous drill holes with wooden planks to prevent the fraud being discovered by HD staff during inspection.


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