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