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The population growth and harsh weather conditions in Saudi Arabia increase the demand for electricity due to the overwhelming usage of air-conditioning system for cooling during the excessively hot weather summer conditions. Therefore, the demand to produce efficient insulation materials for building construction has recently increased for energy and environment conservation, particularly with the recent increase in the electricity tariffs. In this paper, finite element analysis using ABAQUS software was used to determine the optimum geometry of holes for concrete bricks that would increase the thermal resistance of the wall, thereby reducing the consumption of electrical power. The analysis was carried out for 23 models with different configurations of holes for masonry concrete bricks. Regular and staggered cavities arrangements were analyzed. The conduction, convection and thermal radiation phenomena were considered for solid and hollow masonry bricks. The results demonstrated that 51% hollow ratio could reduce the average inner surface temperature $$(T_\mathrm{i})$$ of the concrete brick by $$7.18\,{^{\circ }}\hbox {C}$$ . For bricks with the same hollow ratio, it was observed that there is an effect of the shape of holes in reducing the thermal flow through the bricks, while the number of holes has a marginal effect on the average inner surface temperature $$(T_\mathrm{i})$$ . Further, the staggered arrangement for circular holes has considerable effect in reducing $$T_\mathrm{i}$$ for bricks with four cavities, while the rectangular cavities have negative impact on $$T_\mathrm{i}$$ . Moreover, for the models with circular and rectangular eight cavities, the staggered arrangement has an advantage in reducing $$(T_\mathrm{i})$$ . [ABSTRACT FROM AUTHOR]

This research reports the formulation and characterization of polymer/date pits composites. Polymers used in this study were high-density polyethylene (HDPE) and polystyrene (PS), while date pits used were locally called khlaas (K) and sekari (S), wastes of two types of date palm fruit grown in Saudi Arabia. Tensile strength (TS) and Izod impact strength (IIS) tests were conducted to assess the mechanical properties of the prepared composites. Thermal properties of the composites were measured and discussed in view of glass transition and melting temperatures, Tg and Tm, respectively, as well as the heat of fusion, which reflects the degree of crystallinity of the polymer/date pits composites. Generally, mechanical properties, i.e., TS and IIS, were reduced upon date pits incorporation in the composites. Results showed that IIS of HDPE/date pits composites drastically suffered from the addition of as low as 5 wt% of date pits. Addition of date pits regardless of the type, either S or K, tended to reduce Tg of the PS100/date pits composites and the heat of fusion of the HDPE/date pits composites at relatively higher date pits content, >10 wt%. The reduction in both degree of crystallinty represented by heat of fusion of the HDPE and mechanical properties of all composite systems used in this study at the high loading presence of date pits may be related to the anticipated coarse morphology of the composites evolved during the mixing of polymers, with date pits in the absence of an appropriate coupling agent system. [ABSTRACT FROM AUTHOR]

This study was planned to explore the locally available natural sources of gum hydrocolloids as a natural modifier of different starch properties. Corn (CS), sweet potato (SPS), and Turkish bean (TBS) starches were mixed with locally extracted native or acetylated cactus (CG) and acacia (AG) gums at 2 and 5% replacement levels. The binary mixtures (starch-gums) were prepared in water, freeze dried, ground to powder, and stored airtight. A rapid viscoanalyzer (RVA), differential scanning calorimeter (DSC), texture analyzer, and dynamic rheometer were used to explore their pasting, thermal, textural, and rheological properties. The presence of acetylated AG or CG increased the final viscosity (FV) in all three starches when compared to starch pastes containing native gums. Plain SPS dispersion had a higher pasting temperature (PT) than CS and TBS. The addition of AG or CG increased the PT of CS, SPS, and TBS. The thermograms revealed the overall enthalpy change of the starch and gum blends: TBS > SPS > CS. The peak temperature ( T p ) of starches increased with increasing gum concentration from 2 to 5% for both AG and CG native and modified gums. When compared to the control gels, the addition of 2% CG, either native or modified, reduced the syneresis of starch gels. However, further addition (5% CG) increased the gels' syneresis. Furthermore, the syneresis for the first cycle on the fourth day was higher than the second cycle on the eighth day for all starches. The addition of native and acetylated CG reduced the hardness of starch gels at all concentrations tested. All of the starch dispersions had higher G' than G″ values, indicating that they were more elastic and less viscous with or without the gums. The apparent viscosity of all starch gels decreased as shear was increased, with profiles indicating time-dependent thixotropic behavior. All of the starch gels, with or without gums, showed a non-Newtonian shear thinning trend in the shear stress vs. shear rate graphs. The addition of acetylated CG gum to CS resulted in a higher activation energy ( Ea ) than the native counterparts and the control. More specifically, starch gels with a higher gum concentration (5%) provided greater Ea than their native counterparts.