دانلود رایگان مقاله خواص حرارتی و مکانیکی ژئوپلیمر کرنش سختی کائوچو

ABSTRACT

The thermal and mechanical properties of sustainable lightweight engineered geopolymer composites (EGCs), exhibiting strain-hardening behavior under uniaxial tension, are reported in this study. Fly ash-based geopolymer was used as complete replacement of cement binder to significantly increase the environmental sustainability of the composite compared to the engineered cementitious composite (ECC). Additionally, three types of lightweight aggregates including expanded perlite, microscopic hollow ceramic spheres and expanded recycled glass were used as complete replacement of micro-silica sand to reduce density and thermal conductivity of the composite. The influences of the type of aggregates on the fresh and hardened properties ofthe composite including matrix workability, density, compressive strength, thermal conductivity and uniaxial tensile performance were experimentally evaluated. The results indicated that the density and compressive strength of all EGCs developed in this study, even the EGC containing normal weight micro-silica sand, were less than 1833 kg/m3 and more than 43.4 MPa, respectively, meeting the density and compressive strength requirements for structural lightweight concrete. Replacing normal weight micro-silica sand with lightweight aggregates reduced the compressive and tensile strengths of the EGCs by a maximum of 24% and 32%, respectively. However, the tensile ductility of the EGCs containing lightweight aggregates was comparable to that of the EGC containing micro-silica sand. In addition, the thermal conductivity of the EGCs containing lightweight aggregates were significantly (38–49%) lower than that of the EGC containing normal weight micro-silica sand, resulting in an end-product that is greener, lighter, and provides better thermal insulation than ECC

4. Conclusions

This study presents the results of experimental determination of the mechanical and thermal properties of sustainable lightweight EGCs exhibiting significant strain hardening behavior under uniaxial tension. The influences of replacing normal weight micro-silica sand with three types of lightweight aggregates on the mechanical and thermal properties of the developed fly ash-based EGCs were experimentally evaluated. The sustainable lightweight fly ash-based EGCs developed in this study exhibited density of 1586–1833 kg/m3 , compressive strength of 43.4–56.8 MPa, thermal conductivity of 1.845–0.934 W/(m K), tensile strength of 3.4–5.0 MPa, and tensile strain capacity of 3.5–3.7%, depending on the type of aggregates. The following specific conclusions are drawn: (1) The compressive strength and tensile performance of the fly ash-based EGC containing normal weight micro-silica sand (EGC-S) are comparable to those oftypical ECC M45. At the same time, EGC-S is a cement-less and sustainable composite with 52% lower CO2 emissions and 17% lower embodied energy compared to those of ECC M45. In addition, EGC-S with an average density of 1828 kg/m3 , unlike ECC M45 (2077 kg/m3 ), can be classified as lightweight concrete.