Stress wave propagation velocity at early ages

摘要

The possible errors within the testing program correspond to normal conditions during the construction or PIT performance and they were reduced to acceptable ranges. The wave velocity is directly proportional to the concrete's mix age during the first 7 days of curing process. According to R2 obtained the regression analysis performed characterizes accurately the stress wave velocity at early ages; for ages older than 7 days the stress wave velocity reduces its dependancy of age and becomes a property related to the compressive strength of the concrete or mortar. The correlation equations obtained between age and stress wave velocity for every concrete or mortar tested fits well reflection R2 values close to unity. In general the result obtained with the mortar reflects a more consistent behavior; in the opposite the concrete reflects results slightly more scatter. The researcher attributes this behavior to the fact that in the case of mortar probes the ratio between aggregates particule size/cross sectional side is much lower than for the concrete. i.e in concrete the ratio varies from 0.10 to 0.19 and for mortars it rages around 0.05 or lower obtaining a much more uniform media for the stress wave to travel. The results obtained with the 24.13 Mpa(3500 psi) reflects a reduction of the stress wave velocity at 28 days of age. The researcher concludes that external effects could have influence such behavior. There is a clear tendency for mortar to get higher stress wave velocity than concretes.