Acoustic Impedance Evaluation of the Polymer–Polymer Hybrid Composites as Insulator Building Materials

Acoustic energy dissipates in multi-phase or multi-boundary materials. Hybrid composites are described as multi-phase with many interfaces between their materials. The current research proposes the study of the acoustic behavior of polymeric hybrid composites by estimating the time, velocity, and hybrid composite acoustic impedance. Two groups of hybrid composites were prepared, including unsaturated polyester with PMMA, except one with HDPE and the other with PS. Each group had 28%, 35%, and 40% weight fractions. An ultrasonic test measured the time to determine the velocity and then the acoustic impedance later. The results showed that increasing the weight fraction will increase the density with respect to the density of the reinforcing material. Different ultrasonic times were obtained with increasing weight fractions. As the weight fraction of PS increased, the time increased; unlike the velocity, it decreased but increased with density. In contrast, this behavior was changed if the hybrid had PE. The highest acoustic impedance was at 28% UP/PMMA + PS. In conclusion, UP/PMMA + PS can dissipate ultrasonic waves more than UP/PMMA + PE

Workability and Compressive Strength Properties of (Fly Ash-Metakaolin) based Flowable Geopolymer Mortar

RPC (Reactive Powder Concrete) is a high-strength concrete with outstanding technical qualities. One of the most crucial critical criteria in RPC development is the cement content. Cement production is seen as an environmentally unsustainable process. As a result, it is necessary to substitute cement in RPC manufacturing with an environmentally acceptable binder. Geopolymer seems to be a novel binder that can completely replace cement. The properties of constituents and their percentages in the mix significantly affect the behavior of geopolymer concrete or mortar. This research aims to produce Geopolymer RPC (GRPC) and verify the impact of the ratios of fly ash/pozzolanic materials (FA/P), sand/pozzolanic materials(S/P), finer sand/fine aggregate (S2/S1), and alkaline solution/pozzolanic materials (A/P) on its mechanical and durability properties. The results of the current works demonstrate that increase in alkaline solution to binder ratio increase the compressive strength of the mortars from 62.28 to 70.01 MPa at 62.50% to 100% alkaline/binder ratio, respectively. As well as, vfor the same alkaline/binder ratio the workability subsequently improves from 15 to 17.3mm