02-20-2014, 11:26 AM
This is a perfect time to bring up this issue.
The aggregates used in Hawaii present an issue with regard to concrete. Most aggregates and fines in Hawaii are derived from Basalt rock and are of a crushed source. This presents a particular oddity not typically found elsewhere across the mainland. The very nature of Basalt makes it's porosity and density variable. It therefor may have a tendency to absorb some of the hydration put into the mix and it may even absorb that hydration more greatly over an extended period while submerged in the mix. The other factor being the crushed aspect of this aggregate, this alone changes slumping factors compared to that of a say a smooth oblong round granite stone. Thus the inherent workability of the aggregates and fines used on the island have a less working friendly characteristic, right off the bat. Unfortunately this results in a tendency to over hydrate a mix here in Hawaii and especially when the mix is not properly vibrated prior to working the mix. This is why I frown on additional hydration here. Instead I would advocate the proper use of a vibrator is of utmost importance and depending on the application there may be a need to specify additives that will assist in the finishing process.
The aggregates used in Hawaii present an issue with regard to concrete. Most aggregates and fines in Hawaii are derived from Basalt rock and are of a crushed source. This presents a particular oddity not typically found elsewhere across the mainland. The very nature of Basalt makes it's porosity and density variable. It therefor may have a tendency to absorb some of the hydration put into the mix and it may even absorb that hydration more greatly over an extended period while submerged in the mix. The other factor being the crushed aspect of this aggregate, this alone changes slumping factors compared to that of a say a smooth oblong round granite stone. Thus the inherent workability of the aggregates and fines used on the island have a less working friendly characteristic, right off the bat. Unfortunately this results in a tendency to over hydrate a mix here in Hawaii and especially when the mix is not properly vibrated prior to working the mix. This is why I frown on additional hydration here. Instead I would advocate the proper use of a vibrator is of utmost importance and depending on the application there may be a need to specify additives that will assist in the finishing process.