Synergistic effects of silica nanoparticles/polycarboxylate superplasticizer modified graphene oxide on mechanical behavior and hydration process of cement composites

Abstract

In this paper, the graphene oxide (GO) modified by polycarboxylate superplasticizer (PC) (PC@GO) was decorated by silica nanoparticles (SiO 2 NPs) to form a hybrid structure of SiO 2 NPs/PC@GO. The asprepared SiO 2 NPs/PC@GO hybrid was incorporated in cement matrix for further reinforcement. The results show that SiO 2 NPs are uniformly distributed on the surface of GO nanosheets. The addition of SiO 2 NPs/PC@GO hybrid (1.5% SiO 2 and 0.02% GO by weight of cement) can increase the compressive strength by factors of 38.31%, 44.47% and 38.89% at 3, 7, 28 days, respectively, which are much higher than those of cement composites reinforced by a single-promoter (either PC@GO or SiO 2 NPs).Moreover, our results demonstrate that SiO 2 NPs/PC@GO hybrid can accelerate the cement hydration, improve the degree of pozzolanic reaction and refine the microstructure of hydration products. The excellent reinforcement is attributed to the synergistic effects of SiO 2 NPs/PC@GO hybrid including better dispersion property, higher degree of pozzolanic reaction and cross-linking structure of [SiO 2 -GO-CSH]. This work provides a very effective way to reinforce cement composites by SiO 2 NPs/PC@GO hybrid.

Understanding the behaviour of graphene oxide in Portland cement paste

“…It has often been stated that PCE copolymer prevents GO from aggregation both in Ca(OH) 2 electrolytes as well as in PC pastes [23,24,39,40]. This section investigates the validity of this claim for pastes with water-to-solid ratios of 0.4.…”

“…17b-d. This also implies that the strength improvements reported in previous studies [23,24,39,40] resulted from the presence of GO aggregates rather than well-dispersed GO, as these studies only used 1% and 2% of PCE to mix GO with PC pastes.…”

“…Another issue relates to the methods proposed to prevent GO aggregation in PC paste pore solution [23,24,39,40]. Evidence exists that polycarboxylate ether (PCE) copolymer prevents GO from aggregation in Ca(OH) 2 and NaOH electrolytes (molarities and PCE/GO ratios were unfortunately not specified) [23,24].…”

A cement paste–tail sealant interface modified with a silane coupling agent for enhancing waterproofing performance in a concrete lining system

“…Cement can complete more than 55% hydration process aer 7 day curing as Wang et al reported, compared with about 60% hydration degree aer curing 28 days at same condition. [38][39][40] Additionally, 7 day curing is enough for silane coupling agent to react with cement based on previous research studies. 41,42 Aer curing, extra amount of the modied tail sealant at the bottom of cement paste was cleaned up, while the composite specimen was cut in half lengthwise to examine whether there was any interfacial transition zone formed.…”

Novel engineered high performance sugar beetroot 2D nanoplatelet-cementitious composites

“…The strong interfacial covalent bonding between C-S-H and the functionalized BNP sheets enhances the stress transfer thus improving the overall mechanical properties of the cementitious composites at BNP concentrations of 0.20-wt% and 0.40-wt%. As shown in Figs 22 and 23, the maximum percentage increase in the flexural strength of the BNPcementitious composite at 0.20-wt% is compared with that of several cementitious composites containing MWCNT and GO obtained from[30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. As shown in these figures, overall, the BNP outperforms MWCNTs and GO.…”