Your comments are solicited regarding a 12' x 3' x 3' mass concrete element placed within forms in an over-sized excavation 16' x 6' x 6' which filled with groundwater (placement in wetlands near sea level) after placement and then the groundwater froze with overnight temp of 26 degree F. The...
Two recent instances where 3.25 x 3.25 x 6.5-inch grout specimens achieved lower compressive strength at 28-days than at 7-days. Both sets were cast from 3,000-psi CMU block fill provided by a ready-mix plant at the same project. Both sets were cast in those cardboard set-of-4 molds. Both sets...
I know there are many reasons why concrete compressive strength test specimens come up below the specified strength. Generally speaking, has anyone experienced or can anyone give me a basic explanation for low strength when the cylinders actually seem to crumble? Upon close examination, the top...
The situation is inside a 10-year old addition to a municipal building in central PA. A large conference room slab-on-grade consisting of nine 20'x20' "quadrants" separated by 2 construction joints and 2 saw-cut joints. No expansion material was observed anywhere within the placement area and...
I am in the process of revising our report format for compressive strength testing of masonry grout specimens to bring it in compliance with the requirements of ASTM C 1019. Unfortunately, I cannot find any documentation of how to describe the failure of grout specimens, as required in...
ACI and specs prohibit placing concrete on frozen subgrade, subbase, or footing surfaces, and concrete should not be placed around embedments which have temps below freezing. That said, what will be the actual effect (damage, risk, etc...) if concrete for an above-ground wall is placed inside...
As a construction services inspection and testing firm, we routinely cast sets of four 6 x 12-inch specimens (2 tested @ 7 and 2 @ 28) and sets of five 4 x 8-inch specimens (1 @ 7, 3 @ 28, 1 to hold). Recently a client questioned why they should pay us to test the 28-day specimens when the...
To finish a combination asphalt and concrete road network, the contractor wants to use a construction process which slipforms the curbing first, then places the 10-inch thick reinforced concrete turnpads at intersections, followed by the asphalt paving between the concrete turnpads. Question is...
At a project that has been on-going for over a year, the testing agency recently reported a reduction in 28-day strength of a 5,000-psi mix. This project uses multiple strength concrete from the same supplier ranging from 3,000-psi to 7,000-psi, but only the 5,000-psi mix has demonstrated this...
