RESUMEN
As a transmission medium and heating energy, microwave is widely favored due to its high efficiency, strong selectivity, and easy control. Here, the effects of different heating methods (conventional thermal induction (CI) and microwave induction (MI)) on the polymerization rate of polycarboxylate superplasticizer (PCE) were investigated. Compared with CI, MI significantly boosted the polymerization rate (by approximately 51 times) and markedly decreased the activation energy (Ea), from 46.83 kJ mol-1 to 35.07 kJ mol-1. The polar of the monomers and initiators in the PCE synthesis contributes to varying permittivities and loss factors under the microwave field, which are influenced by their concentration and reaction temperature. The insights gained from the microwave thermal effects and the micro-kinetics of the PCE polymerization system are able to propose theoretical underpinnings for the industrial-scale application of microwave induction polymerization, potentially steering the synthesis of polymer materials towards a more efficient and cleaner process.
RESUMEN
Multiphase flows involving granular materials are complex and prone to pattern formation caused by competing mechanical and hydrodynamic interactions. Here we study the interplay between granular bulldozing and the stabilising effect of viscous pressure gradients in the invading fluid. Injection of aqueous solutions into layers of dry, hydrophobic grains represent a viscously stable scenario where we observe a transition from growth of a single frictional finger to simultaneous growth of multiple fingers as viscous forces are increased. The pattern is made more compact by the internal viscous pressure gradient, ultimately resulting in a fully stabilised front of frictional fingers advancing as a radial spoke pattern.
RESUMEN
This study investigates the effects of five different super-plasticizers (SPs): melamine sulfonate (M), naphthalene-based (N), lignosulfonate (L), polyether-type (P-I), and polyester-type polycarboxylate super-plasticizers (P-II), on fly ash through fluidity, viscoelasticity, inter-microstructure, and mechanism of action (adsorption and zeta) experiments. Additionally, the stability of SPs on AAs was investigated in the ATR-FTIR experiment. The results show that most SPs were effective admixtures under high Ms (2.25) of waterglass (WG) alkali activators (AAs), while P-I SPs performed better under low Ms (1.0) of WG AAs in FA-AAM fly ash pastes. Meanwhile, the higher adsorption and zeta values of samples with P-I SPs were useful for the increase of mesh size of inter-particles and consequently promoted the rheology of FA-AAMs fresh pastes. The more stable structure (ether bond) and the formation of small functional groups (carboxylic acid groups) of P-I SPs in the AAs environment may be the main reasons for this.
RESUMEN
Concrete in which EPS (expanded polystyrene) particles partially or completely replace concrete aggregates is called EPS concrete. Compared to traditional concrete, EPS concrete has a controllable low density and good thermal-insulation performance, which make it promising for prospective applications. At present, research on EPS concrete mostly focuses on increasing its strength and EPS surface modifications. Few researchers have studied the influence of cementitious material strength and EPS-concrete density on the strength of EPS concrete. In this research, cement was used as the main material, and fly ash, silica fumes, and blast furnace slag were selected as admixtures. By changing the mixing proportions of the admixtures, the basic properties, such as the paste strength, change. Based on the mix proportions of the above different raw materials, EPS concrete with different density levels was prepared to explore the influence of the density of EPS concrete and the strength of cementitious materials on the strength of EPS concrete. The influence of the slurry strength on EPS-concrete strength was weaker than that of the density of EPS concrete. When the strength range of the cementitious materials is 35.7~70.5 MPa, the compressive strength range of 1000 kg/m3, 1200 kg/m3, and 1400 kg/m3 EPS concrete is 8.8~17.6 MPa, 11.4~18.0 MPa, and 15.7~26.6 MPa, respectively. Based on the experiments, the fitting equation to determine the EPS-concrete strength-EPS-concrete density-cementitious material strength is z = 69.00087 + 0.0244x - 0.1746y - 0.00189x2 + 0.0000504706y2 + 0.00028401xy. Additionally, a strength-increasing design method for EPS concrete with different densities prepared by conventional Portland cement is clarified. This study can guide the preparation of EPS concrete.
