Abstract: Method and apparatus for measuring in situ the strain and stress of concrete, and having an initial stress resulting from existing stress in the concrete and stress caused from varying externally applied forces on the concrete, by placing a strain gauge on an outer face of the concrete and reading the output to determine an original baseline reading, then cutting spaced slots above and below the gauge to define a segment of the concrete, placing flat jacks into the slots, pressurizing the flat jacks to restore the initial strain to the original baseline reading in the gauge to determine the initial stress in the segment, as alternatives, then leaving the flat jacks pressurized with constant pressure in the slots to measure variations in the strain in the segment over a period of time caused by creep in the concrete, or determining the modulus of elasticity of the concrete by incrementally varying the pressure on the segments while measuring corresponding strain, or adding an adjacent strain gauge to measure t