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• The rheological properties of LHC pastes with MEA and SRA were studied. • The variations of dynamic yield stress and plastic viscosity were estimated by response surface methodology. • The roles of MEA and SRA on the static yield stress development of LHC pastes were investigated. The combined use of low heat Portland cement (LHC), MgO-based expansive agent (MEA) and shrinkage reducing admixture (SRA) is beneficial to reduce the cracking risk of concrete. In this study, the effects of MEA and SRA on the rheological behaviour of LHC paste were investigated using dynamic and static shearing tests. The response surface methodology was used to estimate the effects of MEA, SRA, and superplasticizer on dynamic rheological parameters, while the zeta potential, calorimetric, and solid phases tests were conducted to explore the mechanisms of time-dependent rheological behaviour. Results indicate that MEA contributes to higher dynamic yield stress and plastic viscosity, while the effect of SRA is dependent on its dosage. MEA promotes the static yield stress development for accelerating the hydration of blends and the formation of Mg(OH) 2. SRA retards the hydration of LHC and blended paste and reduces the number of main hydration products. However, the static yield stress is further increased by SRA, showing a consistent changing trend with the surface area of hydrated particles. [ABSTRACT FROM AUTHOR]

In this paper, the rheological behavior of blended cements consisting of calcium sulphoaluminate clinker (CSA), ordinary Portland clinker (OPC) and anhydrite (C S ¯) were investigated. The shear stress-shear rate curves of OPC-CSA-C S ¯ blends with different OPC/CSA/C S ¯ ratios were analyzed. Several rheological models were used to fit the rheological curves of cement pastes. The evolution of static yield stress was also monitored to evaluate the structural build-up rate of the blends. Besides, zeta potential measurement, calorimetric test, XRD and TGA analysis were carried out to reveal the physico-chemical kinetics of the rheological evolution of fresh blends. It was found that not only CSH gel but crystals of AFt and gypsum formed at the early age make contributions to the rheological parameters, i.e. plastic viscosity, yield stress and structural build-up. [ABSTRACT FROM AUTHOR]

[Display omitted] • The role of CGS on the workability of cement paste with and without PCE was investigated. • The decrease of interparticle force leads to the improvement of fluidity when added CGS. • The aggregation of PCE in pore solution leads to its efficiency decrease in the cement pastes blended with CGS. Coal gasification slag (CGS) is the main by-product of coal gasification technology, and the utilization of CGS as mineral admixture is environmentally sound. In this paper, the effect and mechanisms of CGS on the workability (i.e., fluidity and rheological behaviors) of ordinary Portland cement (OPC) paste with and without polycarboxylate superplasticizer (PCE) were studied. The zeta potential and surface free energies of OPC and CGS were tested to calculate the electrostatic force and Van der Waals force variations due to the addition of CGS particles. The results revealed that CGS mainly decreases the van der Waals attraction force between binder particles, enhancing the fluidity and reducing cement pastes' yield stress and plastic viscosity. When blended with PCE, the dissolution of CGS mainly increased the ionic concentrations of Si(OH) x (4-x), which promoted the aggregation of PCE and decreased its adsorption, thus decreasing the fluidity and increasing the rheological parameters. [ABSTRACT FROM AUTHOR]

The workability of cement asphalt (CA) mortar plays a key role in the construction quality and durability of the parking layers in the slab track structure of high speed railways of China. Whereas, the workability of CA mortar is mainly controlled by the rheology of CA paste. In the present paper, the rheological curves of CA paste were measured at 25 °C using a rotating coaxial cylinder viscometer. The Bingham, modified Bingham, Herschel–Bulkley and Casson rheological models were used to fit the data of shear stress–shear rate. The mechanism of the rheological behavior of CA paste was analyzed. The results show that the Hereshel–Bulkley model, which is usually applied for cement pastes, is also the most suitable model for CA paste. The yield stress, consistency index and non-Newton index of CA paste are influenced by the Zeta potential of particles and strengthen of flocculated structure. [ABSTRACT FROM AUTHOR]