Templating effect of alginate and related biopolymers as hydration accelerators for calcium alumina cement - A mechanistic study

Engbert, Alexander; Plank, Johann

doi:10.1016/j.matdes.2020.109054

Cited by 8 publications

(9 citation statements)

References 26 publications

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“…Our results fully confirm these previous findings and directed us to further investigate the working mechanism of these fine fillers, specifically taking into account the model proposed for the accelerating effect of alginate 12 . According to this, the negative charge along the alginate polymer chain attracts Ca 2+ ions which are then bound and chelated by the biopolymer in a molecular cavity holding carboxylate groups.…”

Section: Mechanistic Studysupporting

confidence: 87%

“…Therefore, we conclude that mortar calorimetry presents a more reliable method to monitor actual hardening and strength development of CAC mortar then calorimetry in cement paste. In addition, we observed here that the accelerating effect of alginate which is based on providing a heterogeneous crystallization surface for C‐A‐H phases by attracting Ca 2+ and [Al(OH) 4 ] − ions and enriching them along the biopolymer's chain, 12 is still visible albeit less pronounced as compared to the effect recorded in CAC paste 10 . This hints to a specific impact which presumably is owed to the sand particles.…”

Section: Resultsmentioning

confidence: 71%

“…In previous works, we have investigated the accelerating effect of alginate and similarly structured biopolymers on CAC 10,11 . As working mechanism for these unusual accelerators, we proposed a heterogeneous surface crystallization process facilitated by alternating layers of Ca 2+ und [Al(OH) 4 ] − ions deposited along the molecular chain of the biopolymers 12 . Furthermore, in this study a discrepancy between heat flow calorimetry using paste and strength data collected from mortar was observed.…”

Section: Introductionmentioning

confidence: 73%

“…This was further proven by SEM imaging of alginate which was imbibed into CAC pore solution. There, a much enhanced growth of C‐A‐H clusters on the surface of the biopolymer became visible 12 …”

Section: Mechanistic Studymentioning

confidence: 99%

“…The set behavior of cements such as ordinary Portland cement (OPC) or calcium aluminate cement (CAC) in the presence of various admixtures like superplasticizers, 1‐3 latex polymers, 4,5 retarders, 6,7 or accelerators including nano C‐S‐H 8,9 or biopolymers, for example, alginate 10‐12 has been investigated extensively. Most often, heat flow calorimetry in cement paste and mortar strength tests are applied to study the impact of admixtures on the hydration reaction of the binder.…”

Section: Introductionmentioning

confidence: 99%

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Impact of sand and filler materials on the hydration behavior of calcium aluminate cement

Engbert

Plank

2020

J. Am. Ceram. Soc.

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In earlier work, we have observed discrepancies relating to the early hydration of calcium aluminate cement (CAC) when comparing data from heat flow calorimetry of CAC paste with results from mortar strength tests using the crushing method. Here, we investigated on this phenomenon and found that the sand which is used as a filler exerts a major influence on CAC hydration resulting in acceleration. Furthermore, in particular fine filler materials such as, for example, microsilica, fine limestone powder, and especially α-and γ-Al 2 O 3 also produced a strong hydration accelerating effect which is dependent on their specific surface area. The mechanism underlying the acceleration is that under alkaline conditions their negative surface charge attracts calcium ions as was confirmed via inductively coupled plasma atomic emission measurements. Such a layer generates favourable conditions for the nucleation of CAC hydration products (C-A-H phases). The resulting crystalline hydrates which form on the surface of the filler particles submerged in CAC cement pore solution were visualized via SEM imaging. This way, specifically selected fillers can significantly accelerate CAC hydration and save precious lithium salts which are commonly used to boost the early strength of CAC.

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Section: Mechanistic Studysupporting

confidence: 87%

Section: Resultsmentioning

confidence: 71%