SPECIALIST CONTRACTORS OR SUPPLIERS
RICHARD'S BAY MINERALS SILOS REPAIR
over 2 095 m 2 . The external repairs first entailed removing the spalled and cracked concrete and then cleaning and treating the exposed reinforcing bar with an epoxy coating. SCP 743 was then applied to the opened concrete area to neutralise the concrete and bring it back to an acceptable level. Considering that this was the first time that Rodcol Contracts used SCP technologies, the company received training on the correct application of the technology from Spraylock Africa. Spraylock Africa is the exclusive African distributor for Spraylock Concrete Protection based in Chattanooga, Tennessee in the USA. Inside the structures, Rodcol Contracts repaired the cracked and spalling concrete and a provided a new
50 mm gunite layer. Colloidal silica post-placement pozzolan technology imparts ultra-high durability levels to conventional concrete mixes. Colloidal silica post- placement pozzolan, “colloidal nano silica” or “nano silica” is a cutting-edge nano technology that has been used for more than two decades throughout the world, including in South Africa, to make the oldest commodity-based material more durable and, therefore, longer lasting. These amorphous silicon dioxide particles are less than
C utting-edge colloidal silica post-placement pozzolan technology was deployed in the successful repair of five concrete silos at Rio Tinto’s Richards Bay Minerals (RBM) operation, South Africa’s largest minerals sands producer. SCP 743 was specified as part of the repair design by LNW Consulting Engineers, a leading provider of multidisciplinary engineering and project management services to the heavy industrial engineering and commercial sectors. On the company’s previous projects, SCP 743 enhanced concrete remediation practices. LNW Consulting Engineers also supervised the repairs, which were undertaken by Rodcol Contracts, a reputable concrete repair specialist with a solid track record providing quality services to all industries in the Zululand area, Swaziland, Natal Midlands, Mozambique and the Eastern Cape. The colloidal silica post-placement pozzolan technology was supplied by Spraylock Africa, the African distributor of SCP technology. A total of 4 725 m 2 of concrete was treated with SCP. Considering the sheer size of the silos, it was an extensive undertaking. Ore Silo 4 is 20 m is diameter and 34 m high; Char Silo 1 12 m in diameter and 25 m high; and the Lime and Magnetite Silos 7m in diameter and 17 m high. The most onerous and time-consuming process entailed first erecting scaffolding inside and outside of the structures to provide access to the work areas, the largest of which was Ore Silo 4 where SCP was applied
100 nano metres in size and suspended in water. They are applied to concrete onto horizontal, vertical or overhead slabs after they have been cast. Their extremely small size provides a tremendous amount of reactivity and pozzolanic potential – even greater than that of undensified silica fume. This reaction takes place in the capillary voids and pore space that are created in concrete as bleed water exits the construction material, essentially filling them with more calcium-silicate hydrate (C-S-H). C-S-H is the same reaction product that provides concrete with its strength and durability traits. Even under hydrostatic pressure, the movement of water through concrete is restricted. This waterproofing action considerably reduces water-borne contaminant ingress, including the transport of chlorides. These are the main sources of concrete degradation and structural failure throughout the world.
PROJECT INFORMATION
• Company entering: Spraylock Africa • Client: Rio Tinto • End date: November 2020 • Main Contractor: Rodcol Contracts • Consulting Engineer: LNW Consulting
58 21 st Best Project Awards 2022
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