Serina Ng;Harald Justnes;
<正>Four different cements made from gypsum mixed with clinkers possessing varying amount of clinker phases were employed to investigate the influence of lignosulfonate on the early age rheological and hydration properties of cement pastes.Two test methods were employed,namely the parallel plate rheomeler and isothermal calorimetry.Here, lignosulfonate is shown to impact the early age hydration of cement pastes largely depending on the clinker(C_3A,C_3S and C_4AF) compositions respectively,whereby the main influencing clinker phase is C_3A.It is found that a threshold amount of～4.6% C_3A present in cement is needed to sufficiently impair the performance of lignosulfonate at normal working dosages(0.4%bwoc).When high amounts of C_3A is present in the cement(～10%),flash set of the cement paste can be observed even at a lower dosage of 0.2%bwoc of lignosulfonate.In the presence of low C_3A content,addition of lignosulfonate retards the hydration of C_3S,but the retardation effect decreases when the C_3S is doped with Al. Originality Lignosulfonate is a widely used plasticizer in the concrete industries over the last 80 years.Much research has been conducted with this material and many theories ranging from their reaction mechanisms to their performance on site and influence on mechanical properties of concrete has been conducted.In this investigation,we tackle the issue of this plasticizer from a rheological point of view,while comparing it to heat of hydration data.The goal is to confirm the findings quantitatively,and derive the potential importance of clinker phases in the influence of lignosulfonate on the early age hydration and rheology of cement paste.
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