Change in reaction kinetics of a Portland cement caused by a superplasticizer — Calculation of heat flow curves from XRD data

Photocatalytic NOx abatement by calcium aluminate cements modified with TiO2: Improved NO2 conversion

“…As it is well known, the presence of significant amounts of superplasticizer in the fresh mixtures contributed to the delay in the setting time [19]. The iron-lean CAC (white cement) offered the shortest setting times in comparison with the iron-rich CAC (dark cement).…”

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

“…Because the mechanical properties of the LD CSH and HD CSH are intrinsic to cement paste (Constantinides and Ulm 2004;Constantinides et al 2003;Zhu et al 2007), the most plausible reason for the lower modulus value of LD CSH for specimen OPC is related to a more porous microstructure of the cement matrix. As afore-mentioned in the "Introduction" section, the PEO-containing polymers influence the properties of fresh cement paste: they can hinder the coagulation and sedimentation of un-hydrated cement particles by increasing the electrostatic and/or steric repulsive forces (Jansen et al 2012;Mollah et al 2000). This effect would influence the distribution of hydration products in the hardened cement paste.…”

“…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. These effects are not necessarily [Hu et al 2012a] relevant for the present investigation, mainly because of: 1) the type and size of the hereby PEO-b-PS -based vesicles, being in the nano-range; 2) these self-assembled architectures are in a minimal concentration of 0.025 wt.% per cement weight.…”

“…workability, setting time, water requirement and mechanical strength (Aitcin and Neville 2003;Jansen et al 2012;Young 1972), consequently producing high-strength and high-performance concretes (Jansen et al 2012;Li et al 2005;Neville and Aitcin 1998). The influence of admixed polymers on the properties of cement-based materials is reported to be mainly related to their dispersion ability via increasing repulsive forces and hindering the coagulation and sedimentation of the cement particles by introducing electrostatic and/or steric repulsion (Jansen et al 2012;Mollah et al 2000). The reported mechanisms are generally commented with regard to the molecular structure and adsorption characteristics of the investigated polymeric additions (Uchikawa et al 1997).…”

Development of an eco-friendly Ultra-High Performance Concrete (UHPC) with efficient cement and mineral admixtures uses

“…According to the investigation of Jansen [66], complex Ca 2+ ions from pore solution by the superplasticizer can touch the polymer absorbed on the nuclei or the anhydrous grain surfaces, which in turn might lead to prevention of the nuclei growth or to the dissolution of the anhydrous grains. Hence, the early hydration of the cement is significantly retarded and the generation of Ca(OH) 2 is restrained.…”