Value-Added Use of Non-wood Biomass Combustion Ash towards Production of Sustainable, Economical and High-Performance Geopolymer Concrete

摘要

Hydraulic cement formulations were developed with non-wood biomass ash as a primary raw material. These hydraulic cements meet the ASTM C1157 requirements for use as 'General Use' cements. Values of wheat straw, corn stalk, rice husk, and cotton gin combustion ashes as raw materials for production of hydraulic cements were demonstrated. These non-wood biomass ashes were thoroughly characterized in order to assess the contributions they can made towards an alkali aluminosilicate cement chemistry. Wheat straw, corn stalk and cotton gin ashes were found to provide notable quantities of silicon, potassium and calcium for processing of hydraulic cements. Rice husk ash has a distinct chemistry, and offers primarily reactive silica for use in production of hydraulic cements. Two abundant industrial byproducts, granulated blast furnace slag and coal fly ash, were used to supplement the chemistry of non-wood biomass ash as raw materials for production of an alkali aluminosilicate cement. Other raw materials, used in relatively small concentrations, included sources of alkalis, and additives for achieving improved dimensional stability and deicer salt scaling resistance. These raw materials were transformed into hydraulic cements using a sustainable and economical mechanochemical process. This process involves simple ball-milling of the blend of raw materials at room temperature. The raw materials formulations were refined and optimized in order to produce hydraulic cements that meet standard requirements, and also produce concrete materials that match or surpass the fresh mix rheology, and the hardened material physical, mechanical, chemical stability, barrier, durability, fire resistance and safety attributes of Portland cement concrete. Room-temperature curing of concrete was emphasized in order to maximize the market potential of non-wood biomass ash-based hydraulic cements.;The scalability of the mechanochemical approach to processing of hydraulic cements was verified. For this purpose, a preliminary theoretical basis was devised for scale-up of the process, and the mechanochemical approach to processing of an example non-wood biomass ash-based hydraulic cement was implemented at pilot scale. The resulting hydraulic cement was found to provide qualities approaching those of the cement processed at laboratory scale. The hydraulic cement processed at pilot scale was used for industrial-scale production of concrete, and field construction of a pavement in mid-Michigan with non-wood biomass ash-based hydraulic cement concrete. Conventional concrete mixing, transportation and construction practices were found to be applicable to non-wood biomass ash-based hydraulic cement concrete. The concrete pavement has performed satisfactorily over several months that included exposure to the winder weather in mid-Michigan.;Competitive analyses were performed in order to assess the economic and sustainability merits of non-wood biomass ash-based hydraulic cements versus Portland cement. The results indicated that non-wood biomass ash-based hydraulic cements have carbon footprints that are significantly below that of Portland cement. Their energy contents are also notably below that of Portland cement. An initial economic assessment pointed at the economical viability of the mechanochemically processed non-wood biomass ash-based hydraulic cements. The balance of performance, cost, sustainability and safety provided by non-wood biomass ash-based hydraulic cement make them viable additions to the slate of sustainable and high-performance hydraulic cements based on alkali aluminosilicate chemistry that are under development for enhancing the longevity, sustainability and life-cycle economics of vast concrete-based infrastructure systems.