Alkali-Activated Natural Pozzolan Concrete as New Construction Material

In the near future, geopolymers or alkali-activated cementitious materials will be used as new high-performance construction materials of low environmental impact with a reasonable cost. This material is a good candidate to partially replace ordinary portland cement (OPC) in concrete as a major construction material that plays an outstanding role in the construction industry of different structures. Geopolymer materials are inorganic polymers based on alumina and silica units; they are synthesized from a wide range of dehydroxylated alumina-silicate powders condensed with alkaline silicate in a highly alkaline environment. Geopolymeric materials can be produced from a wide range of alumina-silica, including natural products--such as natural pozzolan and metakaolin--or coproducts--such as fly ash (coal and lignite), oil fuel ash, blast furnace or steel slag, and silica fume--and provide a route toward sustainable development. Using lesser amounts of calcium-based raw materials, lower manufacturing temperature, and lower amounts of fuel result in reduced carbon emissions for geopolymer cement manufacture up to 22 to 72% in comparison with portland cement. A study has been done by the authors to investigate the intrinsic nature of different types of Iranian natural pozzolans to determine the activators and methods that could be used to produce a geopolymer concrete based on alkali-activated natural pozzolan (AANP) and optimize mixture design. The mechanical behavior and durability of these types of geopolymer concrete were investigated and compared with normal OPC concrete mixtures cast by the authors and also reported in the literature. This paper summarizes the main conclusions of the research regarding pozzolanic activity, activator properties, engineering and durability properties, applications and evaluation of carbon footprint, and cost for AANP concrete.

Design and Flux-Weakening Control of an Interior Permanent Magnet Synchronous Motor for Electric Vehicles

Permanent magnet synchronous motors (PMSMs) provide a competitive technology for EV traction drives owing to their high power density and high efficiency. In this paper, three types of interior PMSMs with different PM arrangements are modeled by the finite element method (FEM). For a given amount of permanent magnet materials, the V-shape interior PMSM is found better than the U-shape and the conventional rotor topologies for EV traction drives. Then the V-shape interior PMSM is further analyzed with the effects of stator slot opening and the permanent magnet pole chamfering on cogging torque and output torque performance. A vector-controlled flux-weakening method is developed and simulated in Matlab to expand the motor speed range for EV drive system. The results show good dynamic and steady-state performance with a capability of expanding speed up to four times of the rated. A prototype of the V-shape interior PMSM is also manufactured and tested to validate the numerical models built by the FEM.