This review briefly summarizes introductory understandings of concrete rheology and applications in which rheology plays an important role. A mixture of cement and water is the rheological material classified as dispersed systems involving chemical reactions, and it has been considered the most challenging research subject in the field of rheology. This review introduces the most crucial chemical admixture for fresh concrete controlling rheological properties (so-called superplasticizer) after summarizing the fundamental knowledge of concrete rheology. In addition, recent research trends on 3D printing using concrete, riddled with rheological challenges, are introduced.

Viscoelastic effects of the matrix polymer on molecular dynamics of dielectric probes were examined using the generalized Langevin equation, which was derived to include the retardation effect of viscous force. By solving the equation, we successfully obtained the universal relationship between the complex relaxation modulus and the dielectric spectrum of the probe. When the viscoelastic properties of the matrix are assumed to be viscous, the obtained dielectric relaxation spectrum is described with the Debye function. On the other hand, if they are supposed to be a power-law type relaxation spectrum, the dielectric relaxation spectrum is found to be the Cole-Cole function. The proposed method was applied to a previous study on a low-mass probe in a polystyrene matrix. The estimated effective modulus of the polystyrene was found to be close to a power-law-type relaxation. The present study provides a new microrheological method to estimate the viscoelastic properties in nanometer size.

In the framework of the tube model, the survival fraction of dilated tube, φʹ(t), is essential since the relaxation of the entire system is described according to this quantity. However, a method to define it in multi-chain simulations has yet to be considered. In this study, primitive chain network simulations were performed, and a few structural quantities were discussed as possible candidates for use as φʹ(t). Before analysis, the simulation was evaluated against literature data for linear polyisoprene melts, and quantitative agreement was obtained for viscoelastic and dielectric relaxations. Afterward, the end-to-end relaxation function was compared to survival probability of the slip link φ_s(t) and the ratio of monomers between the most distant surviving slip link pair to the total number of monomers n_s(t)/n_t. The result implies that n_s(t)/n_t is comparable to φʹ(t). Comparison to atomistic molecular dynamics (MD) simulations for polyethylene showed similar results, implying that φʹ(t) can be obtained even in MD simulations if the surviving entanglement points can be specified.

The flow of a floc-forming fluid in a T-junction channel was numerically analyzed using a non-Newtonian viscous model based on the population balance equation (PBE) of the floc size. The finite element method was applied to solve the velocity and pressure fields, and the PBE of the floc size distribution was computed to obtain the effective volume fraction of flocs. The Krieger-Dougherty model was used to evaluate the viscosity of suspension of flocs using the effective volume fraction. The numerical simulation captured the characteristic aggregation-breakage behavior of flocs in the flow. In the region where flows from two entrances merge, the effective volume fraction decreases because the breakage of flocs progresses. In the downstream channel, re-aggregation of flocs occurs near the channel centerline, and the effective volume fraction increases. This aggregation-breakage behavior of flocs was confirmed by the analysis of the floc size distribution.

Anisotropy of the internal damage caused by imposed deformation, which is called stress-softening or Mullins effect, was investigated for a carbon-black (CB) filled styrene butadiene rubber (SBR/CB) by a sequence of two tensile measurements. A wide-width pristine sheet specimen satisfying pure shear (planar) stretching geometry was first subjected to a single loading-unloading cycle with a maximum stretch (λ_m). The rectangular subsamples were cut out from the unloaded and relaxed sheet specimen such that the long axis had an angle of θ = 0° or 90° relative to the pre-stretching axis. Subsequently, uniaxial stretching of the subsamples was conducted, and the internal damage (D₀ or D₉₀) at each angle was evaluated as a function of λ_m from the difference in the uniaxial stress-strain data between the subsamples and the pristine samples. Almost no anisotropy (f = D₀/D₉₀ ≈ 1) was observed for the internal damage in the moderate λ_m regime of λ_m < 3. This is in contrast to a large damage anisotropy (f ≈ 3) in the corresponding λ_m regime previously reported for a silica filled SBR with silane coupling agent (SBR/Silica). The f values for SBR/CB in the high λ_m regime of λ_m > 3 increased with λ_m and became comparable to those in SBR/Silica. The significantly large difference in the internal damage anisotropy between SBR/CB and SBR/Silica reflects the differences in the types of destructed molecular bonding for the filler networks and filler/rubber interfaces between the two elastomers.