A uniaxial load frame for in situ neutron studies of stress-induced changes in cementitious materials and related systems.

For in situ neutron scattering experiments on cementitious materials, it is of great interest to have access to a robust device which can induce uniaxial load on a given solid sample. Challenges involve selection of materials making up the apparatus that are both weak neutron scatterers and yet adequately strong to induce loads of up to a few kilonewtons on the sample. Here, the design and experimental commissioning of a novel load frame is provided with the intended use as a neutron scattering sample environment enabling time-dependent stress-induced changes to be probed in an engineering material under compression. The frame is a scaled down version of a creep apparatus, which is typically used in the laboratory to measure deformation due to creep in concrete. Components were optimized to enable 22 MPa of compressive stress to be exerted on a 1 cm diameter cement cylinder. To minimize secondary scattering signals from the load frame, careful selection of the metal components was needed. Furthermore, due to the need to maximize the wide angular detector coverage and signal to noise for neutron total scattering measurements, the frame was designed specifically to minimize the size and required number of support posts while matching sample dimensions to the available neutron beam size.