For ming slabs without steel reinforcement

Forming slabs without steel reinforcement

Working closely with contractor DM Bodenstein Projects & Construction, AfriSam supplied a purpose-designed readymix formulation for the construction of 300 mm thick surface beds at an industrial development in Spartan, Kempton Park.

DM Bodenstein Projects & Construction completed Phase 1 of the project in 2019, which comprised access and security structures. The balance of the work in Phase 2, 3 and 4 comprise the construction of three surface beds in the storage yard, as well as the installation of fire hydrant lines plus sleeving for all services and paved walkways.

The challenge was to design and construct the concrete slabs to cater for forklifts carrying up to 98.17 t on their front axle. The solution developed was a modified AfriSam Surfacebed mix with the addition of Oxyfibre, supplied by Chryso Southern Africa.

In consultation with the AfriSam Centre of Product Excellence and the technical team from Chryso Southern Africa, a high dosage rate of 3 kg Oxyfibre per cubic metre of concrete was determined as the optimum application. “The project specification called for a 40 MPa concrete, 125 mm slump, with a 22.4 mm aggregate. The addition of the Oxyfibre, with a strand length of 40 mm, required careful monitoring of the slump at all times,” says Dewet Bodenstein, director, Bodenstein Projects & Construction.

A thorough mix

The high density of fibre in the mix necessitated very thorough mixing of the

Placement of fibrereinforced concrete using an AfriSam pump The project specification called for a 40 MPa concrete, 125 mm slump, with a 22.4 mm aggregate

concrete to ensure that it was evenly dispersed. As AfriSam’s readymix plant in Spartan is less than 2 km from the construction site, the concrete trucks arriving on-site had to stand for another 10 minutes to complete the required mixing time.

“Another major advantage of using fibre instead of steel mesh is that the fibre disperses throughout the concrete matrix, facilitating a multidirectional plastic shrinkage cracking reduction matrix,” Bodenstein explains.

Seven-day cube results achieved 29 MPa and, with the appropriate curing, the required 40 MPA specified strength at 28 days was achieved.