It is defined as ratio of lateral strain to the longitudinal strain under uniform axial stress.
It can be referred that at stress of about 80% of compressive strength there is a point of inflection on volumetric strain curve whereas after application of axial stress sample as a whole undergoes volume change expressed as volumetric strain. As the stress increases beyond the point of inflection, the rate of volume reduction decreases. If the stress is further increased volume starts increasing and it observed due to development of micro-cracks. Due to this microcracks lateral strain is observed to be more than longitudinal strain. Generally, its value is in range of 0.1-0.3 However it is taken mostly 0.2. This Poisson’s ratio depends upon grade of concrete, with increase in grade of concrete it also decreases i.e. inversely proportional.
