Reuse of concrete waste, especially in large quantity, can save not only material but also cost for its disposal. This paper presents experiment results on the use of fine and coarse aggregates from concrete waste in ...Reuse of concrete waste, especially in large quantity, can save not only material but also cost for its disposal. This paper presents experiment results on the use of fine and coarse aggregates from concrete waste in geopolymer mortars and concretes. Geopolymeric cement is an inorganic compounds of aluminosilicates synthesized from precursors with high content of silica and alumina activated by alkali silicate solutions. Geopolymer in this experiment was synthesized from fly ash as the precursor and sodium silicate solution as the activator. Hardening of geopolymers was performed by heating the casted paste in an oven at -60~Cfor 3 to 36 hours. Compressive strength of geopolymer pastes and mortars using either fresh or waste fine aggregates were in the range of 19-26 MPa. Hardening time of 3 hours at 60~C followed by leaving the test pieces at room temperature for 7 day before testing results in similar strength to that of mortars cured for 36 hours at 60~C followed by leaving the samples at room temperature for 3 days. It suggests that optimum strength can be achieved by combination of heating time and rest period before testing, i.e the specimens age. Applying mix design with a target strength of 40 MPa, conventional Portland cement concretes using fresh aggregates reached 70% of its target strength at day-7. Compressive strength of geopolymer concretes with waste aggregates was -25 MPa at day-3 while geopolymer concretes with fresh aggregates achieved -39 MPa at day-3. It can be concluded that geopolymer concretes can achieve the target strength in only 3 days. However, the expected reinforcing effect of coarse aggregates in concrete was ineffective if waste coarse aggregates were used as the strength of the concretes did not increase significantly from that of the mortars. On the other hand, waste fine aggregates can be reused for making geopolymer mortars having the same strength as the geopolymer mortars using fresh aggregates.展开更多
Conventional waste management practices focusing principally on waste collection, treatment and disposal or even minimisation often prove insufficient to address resource management challenges in a sustainable manner....Conventional waste management practices focusing principally on waste collection, treatment and disposal or even minimisation often prove insufficient to address resource management challenges in a sustainable manner. Taking into account the relationship between water provision, energy security and resource efficiency, a systems approach that delivers a strong information basis and provides opportunities for resource use optimisation at various levels of application provides opportunities for synergies that could deliver real benefits when cross-sectoral solutions are applied. By-products from sewage treatment in combination with organic solid waste such as food waste can provide a valuable source of energy if managed properly and utilised effectively. This way, waste can be seen as a raw material than can be turned into a resource rather than simply be discarded. As such, AD （anaerobic digestion）, the co-digestion of food waste with sewage sludge, could become a strategic and cross-sectoral solution, if carefully applied, with the potential to convey beneficial synergies for the water and the waste industries. However, barriers to the development of such systems are diverse and often interlinked. Institutional frameworks, decision making constraints, and regulatory boundaries might still appear to require an answer for three different problems, but this can be overcome if presented as just three different parts of the same answer. Such synergies could deliver economic benefits from the additional renewable energy generated and its associated incentives, and savings on costs for the infrastructure required for the exclusive digestion of food waste.展开更多
文摘Reuse of concrete waste, especially in large quantity, can save not only material but also cost for its disposal. This paper presents experiment results on the use of fine and coarse aggregates from concrete waste in geopolymer mortars and concretes. Geopolymeric cement is an inorganic compounds of aluminosilicates synthesized from precursors with high content of silica and alumina activated by alkali silicate solutions. Geopolymer in this experiment was synthesized from fly ash as the precursor and sodium silicate solution as the activator. Hardening of geopolymers was performed by heating the casted paste in an oven at -60~Cfor 3 to 36 hours. Compressive strength of geopolymer pastes and mortars using either fresh or waste fine aggregates were in the range of 19-26 MPa. Hardening time of 3 hours at 60~C followed by leaving the test pieces at room temperature for 7 day before testing results in similar strength to that of mortars cured for 36 hours at 60~C followed by leaving the samples at room temperature for 3 days. It suggests that optimum strength can be achieved by combination of heating time and rest period before testing, i.e the specimens age. Applying mix design with a target strength of 40 MPa, conventional Portland cement concretes using fresh aggregates reached 70% of its target strength at day-7. Compressive strength of geopolymer concretes with waste aggregates was -25 MPa at day-3 while geopolymer concretes with fresh aggregates achieved -39 MPa at day-3. It can be concluded that geopolymer concretes can achieve the target strength in only 3 days. However, the expected reinforcing effect of coarse aggregates in concrete was ineffective if waste coarse aggregates were used as the strength of the concretes did not increase significantly from that of the mortars. On the other hand, waste fine aggregates can be reused for making geopolymer mortars having the same strength as the geopolymer mortars using fresh aggregates.
文摘Conventional waste management practices focusing principally on waste collection, treatment and disposal or even minimisation often prove insufficient to address resource management challenges in a sustainable manner. Taking into account the relationship between water provision, energy security and resource efficiency, a systems approach that delivers a strong information basis and provides opportunities for resource use optimisation at various levels of application provides opportunities for synergies that could deliver real benefits when cross-sectoral solutions are applied. By-products from sewage treatment in combination with organic solid waste such as food waste can provide a valuable source of energy if managed properly and utilised effectively. This way, waste can be seen as a raw material than can be turned into a resource rather than simply be discarded. As such, AD （anaerobic digestion）, the co-digestion of food waste with sewage sludge, could become a strategic and cross-sectoral solution, if carefully applied, with the potential to convey beneficial synergies for the water and the waste industries. However, barriers to the development of such systems are diverse and often interlinked. Institutional frameworks, decision making constraints, and regulatory boundaries might still appear to require an answer for three different problems, but this can be overcome if presented as just three different parts of the same answer. Such synergies could deliver economic benefits from the additional renewable energy generated and its associated incentives, and savings on costs for the infrastructure required for the exclusive digestion of food waste.
