Geopolymers, from industrial wastes such as blast furnace slag, red mud, and coal ash, among others, have emerged as technically viable, economically competitive, and environmentally attractive supplements and even alternatives to ordinary Portland cement (OPC). Furthermore, while the most impact shall be achieved with large-scale use in the general building and structural sector, as replacement or supplement to OPC, the properties of these geopolymers may be optimized for special niche applications. One of these applications is for light weight, low thermal conductivity, heat resistant, and moderate strength cement binder for low rise residential buildings. In this study, compressive strength, heat resistance, volumetric weight, mass loss, water absorption and thermal conductivity of geopolymers formed from mixtures of coal bottom ash and rice hull ash (CBA-RHA) and coal fly ash and rice hull ash (CFA-RHA) with sodium silicate solution (modulus 2.5) as activator were evaluated. Using mixture design and the JMP statistical software, the CBA-RHA combination at a mass ratio of 46% CBA, 32% RHA with 22% WGS gave properties at maximum desirability of 17.6 MPa compressive strength, 1640 kg/m3 volumetric weight, 273 kg/m3 water absorption, 28 MPa compressive strength after high temperature exposure (1000oC for 2 hours) with 4.4% mass loss, and 0.578 W/m-K thermal conductivity. On a performance basis, even as the geopolymers are formed as paste, these properties fall within the standards for lightweight OPC based-concrete with strength requirements for residential buildings. The low thermal conductivity and higher strength after high temperature exposure vis-à-vis OPC are additional advantages for consideration.

The aim of this work is investigation of effect of CaCO 3 filler on the degradation of high density polyethylene (HDPE) films containing stearate salts as prooxidant additives. The films with thickness of 30 µm were prepared by adding 0.3 wt % prooxidant additives mixture (manganese (II) stearate/ferric stearate/cobalt (II) stearate with ratio of 18:4:1) and CaCO 3 filler from 5 to 20 wt % to HDPE resins by using twin screw extruder. The films were subjected to accelerated weathering treatment according to ASTM G154 standard (340 nm UV lamp, 8 hours UV, 4 hours condensation at 50 o C) for maximum duration of 96 hours. The mechanical properties, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and scanning electron microscope (SEM) were used to assess the changes of films during accelerated weathering. The results showed that the degradation rate of HDPE films with CaCO 3 filler is slower than that of HDPE without CaCO 3 filler, but the higher the CaCO 3 content is, the faster degradation rate HDPE is. After 96 hours of accelerated weathering treatment, the elongation at break of the HDPE film with 5 % CaCO 3 almost unchanged while this value of the HDPE films with 10 and 20 % CaCO 3 decreased significantly (96 % and 100 %, respectively). FTIR spectra of HDPE films with 10 and 20 % CaCO 3 showed carbonyl group's peak as the result of oxidation. FTIR spectra also indicated that CaCO 3 filler did not affect to the mechanism of polyethylene degradation.