Effects of the molecular architecture of comb-shaped superplasticizers on their performance in cementitious systems

Microstructural changes of globules in calcium–silicate–hydrate gels with and without additives determined by small-angle neutron and X-ray scattering

“…The estimated mass losses due to the presence of adsorbed polymers (considered the baseline due to the degradation of the inorganic phase) are 0.4 ± 0.1% for CÀSÀH/PCE102-6 and CÀSÀH/PCE23-6 and 0.2 ± 0.1% for CÀSÀH/PCE102-2 and CÀSÀH/PCE23-2. These semi-quantitative observations are in agreement with the literature [4][5][6][7][8][9][10], confirming the higher propensity of the PCEX-6 series to be adsorbed on the calcium silicate phase, as a result of the higher amount of charged carboxylic groups present on the backbone.…”

“…These globules pack into a more open fractal structure compared with the higher side chain density sample (PCE102-2) and the pure CÀSÀH sample. This should be related to the fact that a PCE with a lower side chain density has a higher adsorption on the C 3 S starting powder as well as on the final CÀSÀH particles and hence affects more on the microstructure of CÀSÀH [4][5][6][7][8][9][10]. However, surprisingly, the PCE23-Y series (shorter PEO chain length) shows the reverse trend.…”

“…Each of these pieces can be tuned to produce several graft copolymers varying in the molecular weights and chemical structures. The effect of adding PCEs depends on the chosen chemical structure, which can dramatically alter the interaction between PCEs and the cement matrix [4][5][6][7][8][9]. The adsorption of the PCEs on the surface of the cement particles increases if the density or length of the PEO side chains is decreased.…”

“…While the influence of PCEs on the macroscopic observables of cement (rheology, mechanical properties, and hydration dynamics) has been reported in the literature [4][5][6][7][8][9], the change in the CÀSÀH microstructure due to the PCE additives remains mostly unknown. Very recently, we used small-angle neutron scattering (SANS) to study the microstructure of synthesized pure calcium-silicate-hydrate (I) gel (CÀSÀH (I)) [11].…”

Early Age Hydration, Microstructure and Micromechanical Properties of Cement Paste Modified with Polymeric Vesicles

“…These results are as expected to a certain extent, considering the larger surface area of micelles (50 nm), compared to the hereby investigated vesicles (220 nm) and therefore the possibility of more pronounced "nucleation sites effect" in the former, rather than in the latter case. Additionally, some reports on retardation of early hydration of cement paste due to admixed PEO-containing polymers (normally used as superplasticizers for cement-based materials) need to be also considered (Sakai et al 2006;Winnefeld et al 2007) as contributing factors. The retardation effects are reported to be mainly relevant to the hydration of C 3 S (Lothenbach et al 2007;Pourchet et al ;Winnefeld et al 2007) and the proposed mechanisms (Gu et al 1994;Jansen et al 2012;Mollah et al 2000) can be summarized as: (1) polymers adsorption on the surface of cement grains, hindering the diffusion of water and Ca 2+ ions at the cement grain/solution interface; (2) impeded growth of hydrate phases due to the presence of polymers; (3) dispersive ability and effect of the polymers which alter the growth kinetics and morphology of the hydration products.…”