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While the incineration of biomass residues is gaining traction as a globally available source of renewable energy, the resulting ash is often landfilled, resulting in the disposal of what could otherwise be used in value-added products. This research focuses on the beneficial use of predominantly rice husk and sugarcane bagasse-based mixed biomass ashes, obtained from two paper mills in northern India. A cementitious binder was formulated from biomass ash, clay, and hydrated lime (70:20:10 by mass, respectively) using 2M NaOH solution at a liquid-to-solid mass ratio of 0.40. Compressive strength of the biomass ash binder increased linearly with compaction pressure, indicating the role of packing density. Between the two mixed biomass ashes used in this study, the one with higher amorphous content resulted in a binder with higher strength and denser reaction product. Multi-faceted characterization of the biomass ash binder indicated the presence of aluminum-substituted calcium silicate hydrate, mainly derived from the pozzolanic reaction. [ABSTRACT FROM AUTHOR]

Calcium sulfoaluminate ( CSA) cements have lower carbon footprint than that of portland cement, which makes them a suitable alternative as a sustainable cementitious binder. Early-age expansion of CSA cements can be exploited to induce compressive stress in restrained concrete which can later counteract tensile stress developed during drying shrinkage, thus enhancing the resistance against shrinkage cracking. However, a proper understanding of the expansion behavior is critical to eliminate any risk related to expansion-induced cracking. This study examines the expansion and hydration characteristics of various ordinary portland cement ( OPC)- CSA blends. Early-age expansion of paste samples was monitored. The increase in CSA cement content increased the extent of expansion. Samples having the highest CSA content (30% by mass) exhibited excessive expansion which led to their cracking. Quantitative X-ray diffraction, pore solution extraction, porosity, tensile strength, and dynamic modulus tests were performed to monitor the physico-chemical changes in OPC- CSA blends. It was shown that the ettringite supersaturation in the investigated systems gave rise to the crystallization stress, responsible for the expansion. Thermodynamic models enabled a reasonable prediction of tensile failure, particularly in the blends with the higher CSA content. [ABSTRACT FROM AUTHOR]

Fresh and hardened properties of a suite of cementitious binders with cement kiln dust (CKD) as the main binding component (70% by weight) are evaluated in this study. Two CKDs with different chemical and physical properties were used in formulating CKD-fly ash (FA) and CKD-slag mixtures without portland cement. The setting time, workability, and strength development of these pastes were evaluated first and the best-performing binders were then used as a component in making concrete. The strength and durability of such concrete is also evaluated. The CKD (I)-slag combination outperformed all other mixtures with respect to the strength and durability performance under various curing conditions. The elevated temperature curing was found to be essential for the property development of the CKD-FA binder. The performance of CKD containing mortar mixtures with respect to the delayed ettringite formation (DEF) and the alkali-silica reaction (ASR) was also good. The CKD that exhibited better performance contained 5% free lime, 3% Na2Oeq alkali, and 10.6% SO3 with an average particle size of 4 mm (0.00016 in.). [ABSTRACT FROM AUTHOR]