Construction World October 2021

multi-dose water-reducing plasticiser. “This admixture allows a wide range of dosages to be applied, without any excessive retardation at the higher dosages,” he says. “The multi-dose characteristic of CHRYSO® ZA 1559 also gives concrete extended workability characteristics.” Flannigan notes that it improves the cohesion and lowers the viscosity of a concrete mix. This results in an improved homogeneity and compaction, allowing for superior off-shutter finishes. With less need to add extra water, CHRYSO® ZA 1559 reduces the permeability of concrete, thereby improving is durability. “The product may be used in mixes extended with limestone or commonly used supplementary cementing materials (SCMs) like ground granulated blast furnace slag (GGBS), fly ash and silica fume,” he says. “At the same time, it does not undermine the early age strength of concrete. In fact, in certain cases, it may be used to improve it.” CHRYSO® ZA 1559 has applications in readymix concrete and mechanically mixed site concrete, as well as conventionally placed, pumped and highly reinforced concrete. It conforms to the requirements of SANS 50934-2 (EN 934-2) standards, which are approximate equivalents of ASTM C494 Type A. Water evaporation was successfully controlled with CHRYSO® Profilm 19 evaporation reducer, while shrinkage of the reservoir floor was reduced using CHRYSO® Serenis shrinkage reducing agent. A minimum of 180 litres of water per m3 had to be used and fly ash was added as the heat of hydration had to be controlled due to the mass pour. The end strength did not exceed 45 MPa. 

Evaporation was controlled using CHRYSO Profilm 19 evaporation reducer at the Khutsong reservoir project.

37 CONSTRUCTION WORLD OCTOBER 2021