Influencia de la ceniza de bagazo de diferentes finuras en la reacción álcali-sílice del mortero

This research aimed to study the effect of finenesses of bagasse ash (BGA) on the alkali-silica reaction of mortar. The BGA sample was ground to have particles retained on a sieve No. 325 of 33±1% and 5±1% by weight. Ground BGA samples were used separately to replace ordinary Portland cement (OPC) at rates of 10, 20, 30 and 40% by weight of binder to cast mortars. The compressive strengths and the alkali-silica reaction (ASR) of mortars were investigated. The results showed that a large particle size of BGA is not suitable for use in lowering ASR because it results in a low compressive strength and high expansion due to ASR. The mortars containing BGA with higher fineness exhibited higher compressive strength and lower expansion due to ASR than the mortars containing BGA with lower fineness. The results also suggested that the ground BGA retained on a sieve No. 325 of less than 5% by weight is suitable to be used as a good pozzolan which provides high compressive strength and reduces the expansion of mortar due to ASR even though it contains high LOI. The obtained results also encourage the utilization of ground BGA effectively which leads to reduce the disposal of bagasse ash.Esta investigación tiene como objetivo estudiar el efecto de la finura de la ceniza de bagazo (BGA) en la reacción álcali-sílice del mortero. La muestra de BGA fue molida para conseguir partículas retenidas en un tamiz No. 325 de 33 ±1% y 5±1% en peso. Las muestras de BGA molidas fueron utilizadas separadamente para reemplazar el cemento Portland en proporciones del 10, 20, 30 y 40% en peso en el mortero. Se estudiaron tanto las resistencias a compresión como la reacción álcali-sílice (RAS) de los morteros. Los resultados indicaron que la utilización de un tamaño mayor de las partículas de BGA no es recomendable para disminuir la RAS ya que conlleva a una disminución de las resistencias a compresión y a una alta expansión debido a la RAS. Los morteros que contenían BGA de una mayor finura exhibían mayor resistencia a compresión y una menor expansión, debido a la RAS, que los morteros que contenían BGA de menor finura. Al mismo tiempo los resultados sugieren que el BGA molido retenido en un tamiz No. 325 de menos de un 5% en peso es apropiado para ser usado como material puzolánico, ya que provee una gran resistencia y reduce la expansión del mortero producido por la RAS a pesar de contener una alta pérdida por calcinación. Los resultados obtenidos también recomiendan la utilización eficiente del BGA molido ya que conlleva una disminución de los desechos de las cenizas de bagazo

Factors affecting compressive strength and expansion due to alkali-silica reaction of fly ash-based alkaline activated mortar

Data availability: Data will be made available on request.Copyright © 2023 The Author(s). The development of environmentally friendly alkaline-activated materials (AAMs) holds promise, as AAMs can be derived from waste materials. This study aims to investigate the factors influencing (i) compressive strength and (ii) expansion due to alkali-silica reaction (ASR) in AAMs. These factors include alkaline concentration, heat curing conditions, fineness of fly ash, and the liquid alkaline-to-binder (L/B) ratio. The findings indicate that the higher concentrations of NaOH solution led to an increase in AAM compressive strength due to the enhanced dissolution and polymerization rates in a more alkaline environment. Heat curing stimulated chemical reactions and structure formation, while the reduced water content resulted in lower porosity and higher compressive strength in the hardened cement. Finer fly ash yielded greater compressive strength than coarser ash, as its smaller spherical particles contributed to denser and firmer structures. The presence of calcium minerals, from both Ordinary Portland Cement (OPC) and high-calcium fly ash, bolstered the strength of hardened products. Moreover, calcium minerals like CaO, Ca(OH)2, and CaSO4 were found to induce ASR expansion by promoting gel formation, leading to later-stage expansion in the hardened cement or concrete. However, finely milled fly ash as a precursor significantly reduced ASR expansion in AAMs, by approximately 40% compared to ordinary Portland cement. This study provides valuable insights for civil engineers for better understanding of AAM behavior and makes contributions to the safety and sustainability of cement and concrete systems.Thailand Science Research and Innovation (TSRI) under Fundamental Fund 2023 (Project: Advanced Construction Towards Thailand 4.0); Department of Civil Engineering, Faculty of Engineering, Chiang Mai University (CMU)

Investigation of hard-burn and soft-burn lime kiln dust as alternative materials for alkali-activated binder cured at ambient temperature

Copyright © 2020 The Author(s). As climate change becomes a severe concern, the development of green technology becomes a goal for many sectors, including the construction material sector. Ordinary Portland cement (OPC), the main constituent of concrete production, is a primary contributor to releasing carbon dioxide (CO2) into the atmosphere. Some alternative cementitious materials have been studied to reduce the massive amount of OPC consumption. Lime kiln dust (LKD), a by-product of quicklime production, is produced in abundance worldwide and mostly disposed of in landfills. The two types of LKD, soft-burn and hard-burn, are high-potential wastes that can be developed as alternative cementitious binders using the alkali-activated binder (AAB) technology. This study investigates the mixture designation and properties of LKD-based AAB when cured at ambient temperature. The results show that an ambient-cured soft-burn LKD-AAB achieved practical workability with an 8 M NaOH solution, 1.50 of sodium silicate-to-sodium hydroxide ratio (SS/SH), and 0.60 of liquid alkaline-to-binder ratio (L/B). A rapid setting behavior and an excellent compressive strength of 10.89 MPa at 28 days were revealed at room temperature curing. The ambient-cured hard-burn LKD-AAB could not provide the appropriate properties. However, the mixture of 20% hard-burn LKD and 80% soft-burn LKD resulted in an LKD-AAB mixture that meets the minimum requirement for low-strength cement applications. The positive outcome of this study may be the solution for of LKD wastes utilization in Thailand that addresses the challenge of developing ambient-cured AAB for in-field applications.Partially supported by Chiang Mai University; the fifth author would like to acknowledge the financial support of the Thailand Research Fund (TRF) under the TRF Distinguished Research Professor Grant No. DPG6180002; financial support and the raw materials for these experiments from Chememan Public Company Limited, Thailand