ali07
According to ACI, concrete is acceptable if the value of a core is greater than 0.85(required strength). Your 35MPa
concrete is acceptable if the core breaks at 29.75MPa or greater. In addition , no single core can be below 75% of required strength. See ACI 301 1.6.7.3
I've always used the Swiss Hammer as an indicator of concrete strength. I would only expect the readings to be accurate to within 300-400 psi. There are too many variables, even in the testing procedure itself, for these results to be relied on. In place of cores,I have had good results with...
It wasn't stated in the original post, but I assume (hope) that the concrete achieved this high slump through the use of a high range water reducer (superplasticizer). Typically, when using a HRWR, if your initial slump is higher than you designed for then your final slump will also be higher...
A 7 sack mix (658lbs. of cement) is closer to a 4000 psi mix. A w/c ratio of .45 may be difficult to place. In this application , I would add a high range water reducer
to increase the workability, decrease the shrinkage, and keep your strengths up.
21 Feb 08 16:12
I work for a ready mix concrete producer which does a good deal of business in the decorative concrete area. We use the Davis integral color system (Chameleon). I was asked by a stamping contractor to look at some pool deck concrete he poured this summer. His customer...
I work for a ready mix concrete producer which does a good deal of business in the decorative concrete area. We use the Davis integral color system (Chameleon). I was asked by a stamping contractor to look at some pool deck concrete he poured this summer. His customer notified him early...
After 25+ years working for ready mix concrete producers, I would prefer to see all pumped concrete with a high range
water reducer( super p ). Depending on the length of line you are pumping through, the mix can easily lose 2 - 3 inches of slump. With lightweight concrete, this loss is even...
Perhaps I should have explained the situation better. The concrete in question has already been placed. The project's testing lab made cylinders which did not come up to strength. A second testing lab went in and shot Windsor probes. All these passed with flying colors. The concrete can...
I work for a ready mix concrete producer and have to provide a written warranty for some concrete delivered to a job site. Does anyone have a generic form letter or know where I can download one?
