Improvement of autogenous shrinkage measurement for cement paste at very early age: Corrugated tube method using non-contact sensors

• Test methods for autogenous shrinkage of cement paste are reviewed.
• Few methods are able to measure the very early autogenous shrinkage of cement paste.
• A non-contact corrugated tube system was designed.
• Results obtained by the designed system show superior accuracy and repeatability.

Test methods for the measurement of autogenous shrinkage of cement paste were reviewed, and it is found that few methods can precisely determine the autogenous shrinkage of cement paste at very early age. Therefore, the corrugated tube method was improved by using non-contact linear variable differential transformer (LVDT) sensor for measuring the autogenous shrinkage of cement paste at very early age. The experimental results show that the transformation ratio of the volume deformation to length change for the designed non-contact system can be as high as 0.97, which gives a significant improvement compared to that for the contact system (0.87). Compared to the contact system, the designed non-contact system also has an improved repeatability: the typical standard deviations reach about 50 μm/m and 10 μm/m before and after setting, respectively.