Construction World January 2021

ROADS & BRIDGES

ROAD FORUMMEETINGHOSTEDONLINE

W ith the promise of a plethora of road construction projects on the cards as part of Governments COVID-19 economic relief stimulus packages the 39 th Road Pavement Forum (RPF) was an eagerly anticipated event and was successfully organised as an online event in September this year. Hosted by surface mining industry association, ASPASA, the event was well attended by approximately 300 attendees via meeting streaming software and featured hard hitting presentations and high levels of interaction. First on the agenda was Louw Kannemeyer of the South African National Roads Authority Limited (Sanral) who provided an update of future project roll outs and the position of the agency at present. With a lack of funding due partially to E-Tolls collection difficulties and compounded by COVID-19 restrictions the Agency is keeping a careful reign on its existing and future projects. As seen there can only be projects for which there is budget. He added that the impact of the ongoing E-Toll debacle had been a reduction in toll, as well as non-toll revenue which was used to service toll infrastructure debt. This shortfall amounted to approximately R17-bn which effectively put a halt on any expansive projects in future. The COVID-19 pandemic also led to losses of about R1,1-bin which was reallocated from Sanral to the COVID-19 relief fund S pray-Lock Concrete Protection’s SCP technology is classified as a colloidal silica, which is one of the best sources of the pozzolanic reaction known to man. “SCP colloidal silica is among the smallest post placement pozzolan that is currently being used in the global construction industry. SCP’s colloidal silica is actually smaller in size than un- densified silica fume, but has a bigger reactive surface area,” says Carl White, Managing Director of SprayLock Africa, the African distributor of Spray-Lock Concrete Protection technology. Colloidal silica reacts with calcium hydroxide in the pore space of concrete to form secondary calcium silicate hydrate (C-S-H). This reduces the size of capillary voids and pores, leading to a denser and more homogenous structure that greatly improves the mechanical properties of concrete. White explains that whereas typically applied silicates comprise Sodium (Na), Potassium (K), or Lithium (Li) that is chemically bonded to silica (Si), colloidal silica consists of a stable dispersion of nano-sized particles of amorphous silica.

by the Department of Treasury. Equally interesting was a presentation by Gerrie van Zyl of the South African Bitumen Association who spoke about the associstion’s new Sabita Manual 40 which will be used to replace or compliment the current TRH3 manual. The manual, which is available from Sabita incorporates new technologies and other important updates for the industry to observe and synchronises carefully with COTO standards. The sections of the manual includes general information, materials, performance, seal type and binder selection, design, construction, quality assurance and the repair of premature failures. Cobus Van der Walt of Sanral covered the latest draft of the eagerly anticipated COTO Standard Specification for Road and Bridge Work for South African Roads Authorities, saying it has been a long project leadng to a complete overhaul of the old COLTO document. Barry Pearce of Learning Matters updated the audience on Laboratory Testers Certification ISO 17024 and the deeming of “competent persons” in the eye of legislators. Prof Wynand Steyn of Faculty of Engineering, Built Environment and Information Technology, discussed the University’s new Engineering 4.0 Faculty which is currently under construction and promises to provide its students with world leading facilities to be used in the construction and study of roads. ▄ also produce K, Na, or Li hydroxides as by-products. Conversely, colloidal silica has been shown to produce long chain C-S-H, which is sufficiently more stable than even the “natural” C-S-H formed during the hydration of the cement. White says that, whereas common topically applied silicates react and harden typically in only the top 1 mm to 3 mm of normal concrete surfaces, SCP’s colloidal silica penetrates more than 38 mm or more, into the construction material. “This deep penetrating ability, which produces a long-lasting and resilient reaction product that fills capillary voids and provides associated benefits to hardened concrete for the life of the concrete, is because of colloidal silica’s small particle size and dispersion package,” he says. SCP’s performance has been demonstrated on many projects for, among others, Eskom, AngloGold Ashanti, Anglo Coal, Anglo American Platinum, DeBeers, Sasol Oil & Gas, Sasol Mining, Pioneer Foods, Richards Bay Minerals, Standard Bank, FWJK, CRC Church, NCP Chlorchem, Tongaat Huelett and a leading roads agency. ▄

ONE OF THE BEST SOURCES OF THE POZZOLANIC REACTIONS KNOWNTOMAN

“These particles comprise a charged nucleus that is surrounded by an extended diffuse ionic atmosphere. The colloidal state of subdivision consists of particles with a size sufficiently small (≤ 1 μm) so as not to be affected by gravitational forces, but large enough (≥ 1 nm) to show marked deviations from the properties of true solutions,” he says. When topically applied silicates are used on concrete, the C-S-H formed after the reaction with calcium hydroxides is a shorter chain morphology. This unstable nature that is inferior to Portland cement’s cement/water-formed C-S-H is because these silicates already have a cation, such as Na and K, that is bound to the silica to form a silicate. They

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