Method for testing expansion/contraction stress of cement-based material

Abstract

The invention relates to a method for testing expansion / contraction stress of a cement-based material, which adopts a device for testing the expansion / contraction stress of the cement-based material is adopted. The device comprises inner and outer circular rings which are coaxially arranged and have the same height, and a strain testing device and a data acquisition device which are mutually electrically connected, wherein the materials of the inner and the outer circular rings are the same; the strain testing device comprises a plurality of testing strain gauges; the strain gauges are distributed on the external surface of the outer circular ring and the internal surface of the inner circular ring uniformly along a circumferential direction, and each testing strain gauge is electrically connected with the data acquisition device; the cement-based material is poured between the inner and the outer circular rings, and the strain of the inner and the outer circular rings is tested; and the expansion / contraction stress at a position where the internal radius of the cement-based material is r is calculated according to a formula (I). The method has the advantages that a, the test device is simple, and the operation is simple and convenient; b, restraint stress is uniform; and c, the method can test at the initial stage of watering moulding without moving test specimens, and continuous and automatic test.

Description

technical field [0001] The invention relates to a cement-based material expansion / shrinkage stress test method, which can evaluate the expansion effect of an expansion agent used to prepare shrinkage-compensating concrete, and belongs to the technical field of cement-based material testing. Background technique [0002] Shrinkage-compensated concrete refers to the concrete that is mixed with expansive agent or expansive cement to produce moderate expansion and certain self-stress under certain constraints. It is mainly used for structural self-waterproofing, filling expansion second-phase project, continuous pouring reinforced concrete project and mass concrete project for extending the distance between building expansion joints or post-casting strips. The expansion component relies on its own chemical reaction or reacts with other components of the cement to produce a certain limited expansion compensation or partially compensate for the shrinkage of the concrete during the...

AI Technical Summary

Problems solved by technology

[0015] Using this method can easily calculate the shrinkage and expansion stress of cement concrete under restricted conditions, but since the restraint is mainly provided by the steel bars in the middle, the degree of restraint is mainly determined by the size of the middle steel bars, the degree of restraint is not large enough, and the middle and There are stress concentrations at both ends

In addition, this method needs to move the test piece during the test, which is difficult to repeat the positioning, so it is easy to cause measurement errors and affect the calculation results, and because the test piece needs to be moved, the early expansion and contraction stress cannot be measured, and for the initial The determination of the cracking time cannot be accurately determined due to the need for human observation

Images