Viscoelastic Properties of Fresh Cement Paste to Study the Flow Behavior

Abstract

During concrete pumping, the migration and redistribution of particles occur in a pipe and the lubrication layer that forms between the bulk concrete and the pipe wall is the governing factor determining the flow behavior. In order to identify flow behavior of pumping, in this study, the viscoelastic properties related to the microstructural behavior of a flocculated suspension were examined by using dynamic oscillatory measurements. Cement paste is assumed to be a constituent material of the lubrication layer and ten cases of mixing design are employed by changing the proportions of mineral admixtures. The relationship between the yield stress obtained from the steady shear test and the dynamic modulus resulted from the oscillatory shear measurement was derived and the implications of the correlation are discussed. Moreover, based on the investigation of the viscoelastic properties with oscillatory measurements, the initial behavior of pumped concrete was analyzed systematically.

Additive manufacturing of geopolymer for sustainable built environment

“…However, due to high yield stress, the material was not extrudable through a 25-mm diameter hose pipe. Then referring to an article by Choi et al [24], we adjusted the paste volume to enable a lubrication layer that helped us for smooth flowing of geopolymer inside the hose. Note that, due to stick nature of alkaline reagent the pressure during extrusion was fluctuating between 10-15 bar, i.e 75 part of maximum allowable pressure as mentioned by the pump manufacture.…”

Time gap effect on bond strength of 3D-printed concrete

“…After the LVR is defined by the strain sweep, the effect of time on the material structural rebuild can be further characterized using the oscillatory time sweep test. The LVR is below the critical strain value of 0.2% as measured by the amplitude sweep test (See Figure 8) [23]. To ensure the strain is well within the LVR, 0.1% strain was chosen to be used for measurement.…”

L-Box Form Filling of Thixotropic Cementitious Paste and Mortar

“…Generally, concrete starts to flow as soon as induced shear stress overcomes its yield stress. Yield stress is defined by the particle structural network which is dependent on packing density and relative solid volume fraction, colloidal interparticle forces, and the tendency for agglomeration [22][23][24][25][26][27]. Due to particle interactions, colloidal and non-colloidal cement particles of up to 100 µm tend towards agglomeration.…”