Case Study 1: Versatile Powercrete Plus chosen for Metolong Dam
Arising from discussions in Lesotho with the consultants and contractor for the Metolong Dam project, Quality Department Southern Africa (QDSA) was requested to conduct laboratory evaluations of the RCC (Roller Compacted Concrete) mix and the CVC (Conventional Vibrated Concrete) mix.
Based on Lafarge’s recommendation, Powercrete Plus premium technical cement and DuraPozz®siliceous fly ash from Ash Resources’ Lethabo plant were used as binder material for both mixes.
The RCC mix, with a total binder content of approximately 190 kg/m3 containing a total of 65% fly ash, was tested up to the age of 90 days.
The CEM II Powercrete Plus achieved similar results to those obtained during a trial mix programme by the consultants using a type CEM I product. This pleasantly surprised both the consultants and the contractor, who did not have any previous experience with blending a fly ash containing cement even further with fly ash. A significant factor in favour of Powercrete Plus was that it is a Low Heat Cement. It also has a Low Sodium (0,25%) equivalent in the cement clinker, which dramatically reduces the potential for ASR (Alkali-silica Reaction).
QDSA is continuing to provide technical support during the Dam’s construction. Its laboratory is equipped to undertake Heat of Hydration testing in accordance with EN 196-9, and Lafarge’s cement team has undertaken to supply the consultants with Heat of Hydration results on a regular basis.
CASE STUDY 2: PILING AND BRIDGE DECK – N14 (Brits interchange)
Powercrete Plus was the preferred cement for the N14 bridge contract.Contractor Paramount Construction awarded the concrete supply contract to Lafarge, who used Powercrete Plus CEM II/A-M (V-L) 42,5N with 25% fly ash for the conventional concrete, including the piling.
Concrete for the bridge deck was pumped concrete with a total of 37% fly ash. The concrete mix was placed in a continuous pour of +/- 800m3.