South Korean builders must come up with 4.5 trillion won (US$4.2 billion) in the first half of this year to cover maturing corporate bonds that can put pressure on the companies already struggling from a sluggish construction market, an industry report said Tuesday. According to the tally by the Construction Association of Korea (CAK), the total due in the first six months of this year is larger than the 4.1 trillion won in bonds that matured in the second half of 2013.