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Heading: Basalt/ Greywacke mechanical properties and their use in Bridge Segmental Superstructures in NZ

Driven from the policy: " to try to learn every day". Would like to open Forum/ Peer thoughts exchange on the following subject:

Basalt vs. Greywacke aggregate used in structural concrete in Bridge Segmental Superstructure- Post Tension Structure.

The average density for Basalt and Greywacke aggregates are 2800kg/m3 and 2700kg/m3 respectively. Difference in density is a trivial 3.7%

The questions to be addressed:

How critical is the aggregate density on the total self weight mass/dead load in regard to the structural analyses ?

Does the annual actual/realistic fluctuation in aggregate densities from the quarry exceed the average 100 kg difference in density?

Is the 3.7% mass difference in dead load critical in structural analysis, knowing that in many cases say we use load factors as 1.2G + 1.5Q ?

Does the structural dimensions tolerance provisions nullify the average aggregate/concrete density difference of less than 100kg per m3 concrete weight?

How critical is the different shrinkage values of the aggregates/concrete using Basalt or Greywacke on the quantities of design steel reinforcement/ post tension tendons, the degree of economy , etc?

I think it would be very interesting to explore the technical reasons/advantages why Basalt aggregate was used for Waiwera Viaduct ?

Open for discussion.

Regards right from the Globe bottom, Slave'Tomov

Slave Tomov
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