Thermal management of mass concrete can adversely impact a project’s cost and schedule, both during planning and in execution. Nomograms are presented as aids to quickly identifying and making tradeoffs among promising thermal management options. First, the temperature of fresh concrete and a worst-case adiabatic temperature estimate is provided by a nomogram based on simple physical models. A subsequent nomogram accounts for the impact of size, shape, and environment and is based on a surrogate model generated from many three-dimensional (3-D) finite element simulations without postcooling. Finally, nomograms for postcooling are given, similarly founded on finite element-derived surrogate models, for two classes of cooling pipe layouts. The use of these nomograms, with an awareness of their estimated error, is discussed for the initial development of mass concrete thermal management plans.

To improve the added application value of an industrial waste stone powder (SP), the optimizing mechanism of SP for the structure and composition of hydrothermal synthetic hardened cement stone was investigated in this paper. Cement was partially replaced by SP, silica fume (SF), or ground-granulated blast-furnace slag (GGBS), and then the microstructure with different SP content was tested through X-ray diffraction, thermogravimetric analysis (TG-DTG), mercury intrusion porosimetry (MIP), and scanning electronic microscopy. The findings indicate that the incorporation of SP in autoclaved products significantly enhanced compressive and flexural strengths. As the proportion of SP in cement was increased, a corresponding increase in the content of tobermorite within autoclaved cement mortar was observed. This increase in tobermorite concentration results in an initial rise followed by a subsequent decline in both compressive and flexural strengths. The maximum compressive and flexural strengths were achieved at an SP content of 15%. In addition, the mechanical strength was further improved by adding SP+GGBS or SP+SF. The strengthening mechanism of SP reveals that the change in the ratio of calcium and silicon ions (C/S) caused by SP in the sample was conducive to the formation of tobermorite and strength increase. Meanwhile, an increase in the quantity and a decrease in the crystal size of tobermorite were observed with an increase in the content of stone powder, resulting in a more compact microstructure of the sample. Moreover, the mechanical strength of cement composites doping SP+GGBS or SP+SF was further improved through superposition effects of SP and GGBS or SF with high activity. Currently, it is mainly applied to pipe pile products, and the strengthening effect of SP increases its use value. Meanwhile, the study of SP strengthening mechanism has laid a theoretical foundation for its application in high-strength autoclave and improved the relevant theory.

The prediction of concrete pumpability is of particular interest to properly design pumping circuits and select suitable pumps for successful processing of concrete. A critical review of empirical, analytical, and numerical models is carried out to predict concrete pumpability as a function of pipeline geometry, rheological properties of the bulk concrete, and the characteristics of the lubrication layer. The main mechanisms leading to the formation of the lubrication layer, including the wall effect, Reynolds dilatancy, and shear-induced particle migration (SIPM), are discussed. The main phenomenological models governing SIPM are formulated in terms of spatial variations of particles’ interaction frequency and viscosity. In addition to the single-phase methodology, new computational approaches on SIPM in pipe flow of solid-liquid suspensions are discussed. The coupled computational fluid dynamics-discrete element method (CFD-DEM) and smoothed-particle hydrodynamics (SPH) methods are recommended as the most precise and realistic approaches to simulate concrete pipe flow compared to the DEM and single-phase modelings.

The lubrication layer plays a governing role in predicting the pumpability of fresh concrete. The effects of aggregate content on the rheological properties and formation of the lubrication layer were determined from the measurements of the sliding pipe rheometer, tribometer, and mortar rheology. The performance indexes of fresh concrete, including its rheological properties and workability, were investigated in parallel to fully characterize the impact of aggregate content on the pumpability of concrete. The results show that there is an optimal sand-to-total aggregate ratio (sand ratio) that yields the best rheological properties of the lubrication layer and pumpability of concrete. They also improve with the increase in paste-aggregate (PA) ratio. The shearing degree of bulk concrete is affected by the aggregate content, which leads to different formation processes of the lubrication layer. The rheological properties and workability of concrete are improved with a moderate sand ratio and an increased PA ratio due to the change in thickness of the paste layer on the surface of aggregate particles. The thixotropy of concrete is affected by the aggregate content. Moreover, the formation of the lubrication layer and its rheological property evolution depend on the measurement systems.

An analytical model was established to predict the pumping pressure of flowable concrete as a function of flow rate, pipe diameter, and rheological properties of the concrete and the lubricating layer (LL). The flow behaviors of the different flow zones across the pipe section during pumping were analytically defined for Bingham materials. The prediction model was validated using a pumping circuit involving 14 high-strength flowable concrete mixtures with slump flow values of 500 to 765 mm. The rheological properties of the concrete and the yield stress, viscosity, and thickness of the LL (the latter determined through reverse regression analysis) were considered as input parameters in the prediction model involving 113 data points in the comparison. The analysis revealed that the thickness of the LL can vary between 2 and 5 mm, and that the predicted pressure loss agrees well with experimental measurements within the range of the tested mixtures.