Construction World December 2020

Construction has preserved and protected the outer heritage walls of the existing structure, which date back about 100 years.

COVER STORY

The old-world charm of Cape Town’s De Waterkant area is being captured in a new mixed-use development at the Old Cape Quarter, with main contractor GVK-Siya Zama Construction working closely with AfriSam on finding concrete solutions. CONCRETE RESULTS AT OLD CAPE QUARTER

K LFNLQJ RII LQ 0D\ DQG VFKHGXOHG IRU FRPSOHWLRQ LQ PLG WKH SURMHFW LV DGGLQJ IRXU ͥRRUV RI OX[XU\ DSDUWPHQWV RQWR WKH H[LVWLQJ UHWDLO OHYHO DQG RͦFH OHYHO ZLWK WKUHH EDVHPHQWV 7KH upmarket units include one-bedroom and two-bedroom apartments, DV ZHOO DV WKUHH EHGURRP SHQWKRXVHV Construction has preserved and protected the outer heritage walls of the existing structure, which date back about a hundred \HDUV %HLQJ LQVLGH D UHVLGHQWLDO DUHD DOVR SODFHG UHVWULFWLRQV RQ working hours, while narrow roads around the building made for GLͦFXOW ORJLVWLFV ̰ LQFOXGLQJ WKH UHDG\PL[ GHOLYHULHV 6WUDWHJLHV WR underpin the new structures was a key focus of the early phases, requiring some innovative thinking from the contractors and close FROODERUDWLRQ ZLWK UHDG\PL[ VXSSOLHU $IUL6DP “Due to variable ground conditions, there were a number of piles that had to be executed through the existing bases,” says Garth 5REE FRQWUDFWV GLUHFWRU DW *9. 6L\D =DPD 7KLV PHDQW PP GLDPHWHU FRUH KROHV ZHUH GULOOHG WKURXJK WKH ROG H[LVWLQJ EDVHV 7KLV HQVXUHG WROHUDQFH DQG VSDFH IRU WKH IRXU PP GLDPHWHU piles which would allow the transfer of loads onto the piles from the temporary steel structures and the construction of the new EDVH DERYH WKH SLOHV $ QXPEHU RI QHZ FROXPQV DQG EDVHV KDG WR constructed after the demolition of the old columns and bases and within the temporary steel structure; this was to the new design UHTXLUHPHQWV E\ 6XWKHUODQG (QJLQHHUV “The challenge was the lack of space in the basement for the XVH RI QRUPDO &ODVV IRUPZRUN̹ VD\V 5REE ̸7KH WRS RI EDVHV KDG WR DOLJQ ZLWK WKH WRS RI VXUIDFH EHGV &ODVV IRUPZRUN 6RPH H[LVWLQJ FROXPQV UHTXLUHG YDULRXV W\SHV RI VWUHQJWKHQLQJ :H KDG to construct biscuit columns, whereby we added reinforcing and formwork around the existing column and core-drilled at an angle through existing PT slabs from above the biscuit column – adding JURXW WR HQODUJH DQG VWUHQJWKHQ WKH H[LVWLQJ FROXPQ VL]HV ̹ This complicated the column strengthening process, consuming valuable hours and limiting the amount of concrete that could be poured at a time – hence the need for close collaboration

ZLWK $IUL6DP ,Q SDUWLFXODU WKH 03D FRQFUHWH UHTXLUHG IRU WKLV application could not be poured fast enough before hydration set in “After much discussion with AfriSam, we found a way forward – WR UHFHLYH DQG SRXU MXVW RQH FXELF PHWUH RI UHDG\PL[ DW D WLPH̹ KH VD\V 5HDG\PL[ WUXFNV XVXDOO\ FDUU\ WR P , but this volume could QRW EH SRXUHG DW D IDVW UDWH DV D UHVXOW RI WKH PP JURXWLQJ KROHV DERYH WKH FROXPQV This was because the conditions demanded that concrete be SRXUHG E\ ZKHHOEDUURZ WKURXJK PP FRUH KROHV IURP WKH VODE DERYH LQWR WKH ELVFXLW FROXPQV 7KH FKDOOHQJH ZDV WKDW HDFK column took up to an hour to pour, with admixtures accelerating the KDUGHQLQJ UDWH RI WKLV KLJKO\ ͥXLG FRQFUHWH There was no other option but for concrete to be delivered in smaller volumes, with the trucks standing by patiently for up to an KRXU ZKLOH WKH FXELF PHWUH ZDV SRXUHG $IUL6DP WHUULWRU\ PDQDJHU 0HODQLH 5RVV VD\V WKLV PHDQW D KLJK OHYHO RI ͥH[LELOLW\ DV SRXUV FRXOG RQO\ VWDUW LQ WKH DIWHUQRRQ DQG RIWHQ H[WHQGHG EH\RQG WKH GHDGOLQH DJUHHG EHWZHHQ WKH FRQWUDFWRU DQG WKH DXWKRULWLHV ([WHQGHG SHUPLVVLRQV ZHUH REWDLQHG DQG WKH AfriSam-contracted drivers agreed to put in the extra time until pours ZHUH FRPSOHWHG “It was great to be able to sit down with AfriSam around the table to discuss challenges as they arose, and to come up with solutions WKDW ZRUNHG̹ VD\V 5REE ̸&RPSURPLVHV ZHUH UHTXLUHG DQG ZH DOO FRQWULEXWHG ZKDW ZH FRXOG WR NHHS WKH SURMHFW RQ WUDFN ̹ Augmenting some existing foundations, the geotechnical work ͤQDOO\ LQFOXGHG D FRPELQDWLRQ RI QHZ DQG VWUHQJWKHQHG IRXQGDWLRQV DQG FROXPQV DGGLQJ VLJQLͤFDQWO\ WR WKH QXPEHU RI GRZHOV DQG YROXPH RI HSR[\ FRQVXPHG The added strengthening work also pushed the readymix concrete YROXPH GHPDQGHG E\ WKH SURMHFW IURP P WR P 0RVW ZDV VXSSOLHG IURP $IUL6DP̵V :RRGVWRFN SODQW DERXW NP IURP VLWH The special column mix – a high slump mix with superplasticiser – FDPH IURP $IUL6DP̵V 3HQLQVXOD 4XDUU\ SODQW DW 'XUEDQYLOOH “The gaps in the column reinforcing also required that a smaller

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