Construction World December 2022

SPECIALIST CONTRACTORS OR SUPPLIERS

RICHARD'S BAY MINERALS SILOS REPAIR

over 2 095 m 2 . The external repai rs fi rst entai led removing the spal led and cracked concrete and then cleaning and treat ing the exposed reinforcing bar wi th an epoxy coat ing. SCP 743 was then appl ied to the opened concrete area to neutral i se the concrete and bring i t back to an acceptable level . Cons idering that thi s was the fi rst t ime that Rodcol Contracts used SCP technologies , the company received training on the correct appl icat ion of the technology f rom Spraylock Af rica. Spraylock Af rica i s the exclus ive Af rican di stributor for Spraylock Concrete Protect ion based in Chattanooga, Tennessee in the USA. Ins ide the structures , Rodcol Contracts repai red the cracked and spal l ing concrete and a provided a new

50 mm guni te layer. Col loidal s i l ica post-placement pozzolan technology imparts ul tra-high durabi l i ty levels to convent ional concrete mixes . Col loidal s i l ica post placement pozzolan, “col loidal nano s i l ica” or “nano s i l ica” i s a cutt ing-edge nano technology that has been used for more than two decades throughout the world, including in South Af rica, to make the oldest commodi ty-based material more durable and, therefore, longer last ing. These amorphous s i l icon dioxide part icles are less than

C utt ing-edge col loidal s i l ica post-placement pozzolan technology was deployed in the successful repai r of five concrete s i los at Rio Tinto’s Richards Bay Minerals (RBM) operat ion, South Af rica’s largest minerals sands producer. SCP 743 was speci fied as part of the repai r des ign by LNW Consul t ing Engineers , a leading provider of mul t idi scipl inar y engineering and project management ser vices to the heavy industrial engineering and commercial sectors . On the company’s previous projects , SCP 743 enhanced concrete remediat ion pract ices . LNW Consul t ing Engineers also super vi sed the repai rs , which were undertaken by Rodcol Contracts , a reputable concrete repai r special i st wi th a sol id track record providing qual i ty ser vices to al l industries in the Zululand area, Swaz i land, Natal Midlands , Mozambique and the Eastern Cape. The col loidal s i l ica post-placement pozzolan technology was suppl ied by Spraylock Af rica, the Af rican di stributor of SCP technology. A total of 4 725 m 2 of concrete was treated wi th SCP. Cons idering the sheer s i ze of the s i los , i t was an extens ive undertaking. Ore Si lo 4 i s 20 m i s diameter and 34 m high; Char Si lo 1 12 m in diameter and 25 m high; and the Lime and Magnet i te Si los 7m in diameter and 17 m high. The most onerous and t ime-consuming process entai led fi rst erect ing scaf folding ins ide and outs ide of the structures to provide access to the work areas , the largest of which was Ore Si lo 4 where SCP was appl ied

100 nano metres in s i ze and suspended in water. They are appl ied to concrete onto hori zontal , vert ical or overhead slabs af ter they have been cast . Thei r extremely smal l s i ze provides a tremendous amount of react ivi ty and pozzolanic potent ial – even greater than that of undens i fied s i l ica fume. Thi s react ion takes place in the capi l lar y voids and pore space that are created in concrete as bleed water exi ts the construct ion material , essent ial ly fi l l ing them wi th more calcium-s i l icate hydrate (C-S-H) . C-S-H i s the same react ion product that provides concrete wi th i ts strength and durabi l i ty trai ts . Even under hydrostat ic pressure, the movement of water through concrete i s restricted. Thi s waterproofing act ion cons iderably reduces water-borne contaminant ingress , including the transport of chlorides . These are the main sources of concrete degradat ion and structural fai lure throughout the world. 

PROJECT INFORMATION

• Company entering: Spraylock Africa • Client: Rio Tinto • End date: November 2020 • Main Contractor: Rodcol Contracts • Consulting Engineer: LNW Consulting

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