Concretes containing biomass ashes: Mechanical, chemical, and ecotoxic performances (original) (raw)
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Applied Sciences
This study applies a methodology to evaluate the ecotoxicological potential of raw materials and cement-based construction materials. In this study, natural aggregates and Portland cement were replaced with non-conventional recycled concrete aggregates (RA) and fly ash (FA), respectively, in the production of two concrete products alternative to conventional concrete (used as reference). The experimental program involved assessing both the chemical properties (non-metallic and metallic parameters) and ecotoxicity data (battery of tests with the luminescent bacterium Vibrio fischeri, the freshwater crustacean Daphnia magna, and the yeast Saccharomyces cerevisiae) of eluates obtained from leaching tests of RA, FA, and the three concrete mixes. Even though the results indicated that RA and FA have the ability to release some chemicals into the water and induce its alkalinisation, the respective eluate samples presented no or low levels of potential ecotoxicity. However, eluates from co...
Environmental life cycle assessment of concrete containing biomass fly ash
2016
Concrete production sector is challenged by attempts to minimize the consumption of raw materials and energy and to reduce environmental impact. The use of end-of-life products as cement replacement can allow the production of concrete with the same durability, similar quality properties and with improved environmental performance. This work studies the environmental benefits of incorporating different percentages of two types of fly ashes that can be used in concrete as cement replacement, according to the Portuguese context. The results showed that both ashes provide a benefit for the concrete production because it is possible to produce concrete with low Portland cement content and with a better environmental performance while achieving satisfactory mechanical resistance. As already demonstrated for coal fly ash, the use of biomass fly ash seems to be a promising alternative for the replacement of Portland cement.
Waste Management, 2011
Two combustion tests were performed in a fluidized bed combustor of a thermo-electric power plant: (1) combustion of coal; (2) co-combustion of coal (68.7% w/w), sewage sludge (9.2% w/w) and meat and bone meal (MBM) (22.1% w/w). Three samples of ashes (bottom, circulating and fly ashes) were collected in each combustion test. The ashes were submitted to the following assays: (a) evaluation of the leaching behaviour; (b) stabilization/ solidification of fly ashes and evaluation of the leaching behaviour of the stabilized/solidified (s/s) materials; (c) production of concrete from bottom and circulating ashes. The eluates of all materials were submitted to chemical and ecotoxicological characterizations. The crude ashes have shown similar chemical and ecotoxicological properties. The s/s materials have presented compressive strengths between 25 and 40 MPa, low emission levels of metals through leaching and were classified as non-hazardous materials. The formulations of concrete have presented compressive strengths between 12 and 24 MPa. According to the Dutch Building Materials Decree, some concrete formulations can be used in both scenarios of limited moistening and without insulation, and with permanent moistening and with insulation.
Biomass fly ash in concrete: Mixture proportioning and mechanical properties
Fuel, 2008
ASTM C 618 prohibits use of biomass fly ashes in concrete. This document compares the properties of biomass fly ashes from cofired (herbaceous with coal), pure wood combustion and blended (pure wood fly ash blended with coal fly ash) to those of coal fly ash in concrete. The results illustrate that with 25% replacement (wt%) of cement by fly ash, the compressive strength (one day to one year) and the flexure strength (at 56th day curing) of cofired and blended biomass fly ash concrete is statistically equal to that of two coal fly ash concrete in this investigation (at 95% confidence interval). This implies that biomass fly ash with co-firing concentration within the concentration interest to commercial coal-biomass co-firing operations at power plants and blended biomass fly ash within a certain blending ratio should be considered in concrete.
Applicability of Fly Ash from Fluidized Bed Combustion of Peat, Wood, or Wastes to Concrete
Waste and Biomass Valorization
Five different fly ashes originating from fluidized bed combustion of peat, wood and different type of wastes was studied by their chemical and physical characteristic to find out how they fulfill the requirements for concrete set by European EN 450-1 standard. Fly ash originating mostly from peat combustion is the only fly ash fulfilling all requirements for concrete without any treatments. For other studied fly ashes some chemical and physical characteristics are exceeded: most probably free CaO, sulfate, chloride, and fineness. Also the sum of main components (SiO2, Al2O3, Fe2O3) failed for other ashes than the one originating from mostly peat combustion. However, it should be kept in mind that requirements set by European standard is more restrictive than similar in America and some mechanical treatments are possible way to increase their utilization potential.
Long-Term Behavior of Concrete Containing Wood Biomass Fly Ash
Applied Sciences
Wood biomass is widely used in the European Union as a fuel for the production of heat and electrical energy, generating a considerable amount of ash. The disposal of ash, especially its finest fraction, requires proper engineering solutions, since these particles contain heavy metals and caneasily pollute soil, groundwater, or air. In this work, wood fly ash with a high amount of pozzolanic oxides and one with a high CaO content were used in concrete as a 15% and 30% cement replacement. Incorporation of wood ash in concrete reduced the 28-day compressive strength of concrete by up to 37%, which was attributed to the low stiffness of the wood ash particles, while the 2-year compressive strength indicated very low pozzolanic reactivity. The capillary absorption of concrete increased with the increase in the ash content, but almost no influence on the gas permeability was observed. Wood fly ash with high CaO content reduced the drying shrinkage of concrete by up to 65% after 1 year. I...
Fly Ash as a Concrete Ingredient-A Review Introduction
2016
This paper is written to access the use of fly ash, a waste product by thermal power plant, as an ingredient of concrete used for various engineering purposes such as production of pozzolana Portland cement, geopolymer concrete, lightweight concrete, precast concrete industry, manufacture of precast Poly Vinyl Chloride (PVC) pipes and paver blocks, Self compacting concrete (SCC) and mass concrete etc. The area is of much importance in Indian context as about 145 million tones of fly ash is being produced in India annually from electricity generation plants and this figure is increasing with the growth of demand for energy. The disposal of high volume of fly ash is posing a threat to the environment and requires immediate attention. In present scenario the cement industry alone is responsible for 7% of all the CO2 being produced in the world. Using fly ash as an ingredient in concrete, the problem of safe disposal of fly ash can be addressed considerably. Moreover the use of fly ash ...