TY - JOUR
T1 - Effects of organic additives on calcium hydroxide crystallisation during lime slaking
AU - Pesce, Cecilia
AU - Pesce, Giovanni
AU - Molinari, Marco
AU - Richardson, Alan
N1 - Funding information: We acknowledge Tarmac Buxton Lime for providing the quicklime. This research was carried out within a doctoral studentship provided by Northumbria University.
PY - 2021/1/1
Y1 - 2021/1/1
N2 - Organic compounds, often used in cement systems as admixtures, may affect the crystallisation and carbonation kinetics of Ca(OH)
2, an important phase of hydrated cement. Here, we investigated changes in Ca(OH)
2 morphology in the presence of 3 organic compounds, commonly encountered in cement and lime-based materials: sucrose, pectin and calcium lignosulfonate. The additives were introduced either before or after lime slaking to determine the influence of temperature. Ca(OH)
2 crystals and supernatant solutions were characterised at time of slaking and after 6 months of ageing using scanning electron microscopy, X-ray diffraction and optical emission spectroscopy. Our results indicate that the morphology of Ca(OH)
2 crystals is modified by the characteristics of the organic molecules which promote formation of Ca(OH)
2 with habits that can result in faster carbonation, an effect that is detrimental to cement used in reinforced concrete. These effects are enhanced when the additives are introduced before slaking, likely as a result of thermal degradation.
AB - Organic compounds, often used in cement systems as admixtures, may affect the crystallisation and carbonation kinetics of Ca(OH)
2, an important phase of hydrated cement. Here, we investigated changes in Ca(OH)
2 morphology in the presence of 3 organic compounds, commonly encountered in cement and lime-based materials: sucrose, pectin and calcium lignosulfonate. The additives were introduced either before or after lime slaking to determine the influence of temperature. Ca(OH)
2 crystals and supernatant solutions were characterised at time of slaking and after 6 months of ageing using scanning electron microscopy, X-ray diffraction and optical emission spectroscopy. Our results indicate that the morphology of Ca(OH)
2 crystals is modified by the characteristics of the organic molecules which promote formation of Ca(OH)
2 with habits that can result in faster carbonation, an effect that is detrimental to cement used in reinforced concrete. These effects are enhanced when the additives are introduced before slaking, likely as a result of thermal degradation.
KW - Ca(OH)
KW - Ca(OH) crystal growth
KW - Ca(OH) crystal morphology
KW - Calcium lignosulfonate additive
KW - Pectin additive
KW - Sucrose additive
UR - http://www.scopus.com/inward/record.url?scp=85092741837&partnerID=8YFLogxK
U2 - 10.1016/j.cemconres.2020.106254
DO - 10.1016/j.cemconres.2020.106254
M3 - Article
VL - 139
SP - 1
EP - 13
JO - Cement and Concrete Research
JF - Cement and Concrete Research
SN - 0008-8846
M1 - 106254
ER -