The mechanical properties and durability of cement‐based materials reinforced by nano‐SiO2 (NS) particles are strongly dependent on the dispersion characteristics of the latter. This study presents an innovative eco‐friendly method, which improves the distribution of NS particles through their surface modification using polycarboxylate ether‐based (PCE) superplasticizer containing silane coupling agent under microwave irradiation. The above method ensures the formation of a core‐shell‐shell structure, wherein the PCE shell exhibits enhanced electrostatic and steric hindrance repulsion properties. Moreover, after the surface modification, an improved compatibility between NS and PCE and a higher dispersion stability of NS in the saturated calcium hydroxide solution are attained, which is proved by the respective grafting ratios and encapsulation parameters of the surface‐modified NS particles. The proposed method application guarantees an enhanced fluidity of a fresh cement paste, which makes it lucrative for the production of critical components from nano‐reinforced cement‐based materials.

The potential application of surface modified nano‐SiO2 (NS) particles with poly (dimethyl diallyl ammonium chloride) (PDDA) has been reported in other fields, but not in civil construction. This paper aims to assess the influence of surface modified NS with PDDA on the early‐age hydration of cement paste, where cement is replaced by 0.3%, 1% and 3% of NS particle. PDDA can be introduced onto the surface of NS via long‐distance charge pairs. Calorimetric measurements of cement pastes with 0.35 w/b (water/binder) ratio show that NS particles accelerate the cement hydration, while PDDA retards it. Moreover, the cement hydration is controlled by PDDA at lower dosage of NS/PDDA particle, which delays the exothermic peaks of cement hydration, while the cement hydration is controlled by NS particle aggregates at higher dosage of NS/PDDA particle. Based on the results above, the mechanism of the adsorption of NS/PDDA particle on cement particle surfaces is proposed.

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We synthesized various polymers with different functional groups of ─COO − , ─SO 3 − , and ≡N + ─ to study the impact of the environmental temperature (25, 50, and 80 C) on the dispersing capability by measuring the fluidity of fresh cement paste, total organic carbon, ζ potential, and isothermal calorimetry. The results show that no adsorption was observed for the cement pastes containing acrylic acid, 2-acrylamido-2-methyl propane sulfonic acid, and [3-(methacryloylamino)propyl] trimethyl ammonium chloride, probably because of the trace amount of adsorption, whereas the fluidity of the pastes was indeed improved by the addition of these chemicals. Generally, for the polymers containing various functional groups, the adsorption capability was in the order ─COO − > ─SO 3 − > ≡N + ─. The dispersing capability for the carboxylate superplasticizer was robust to the change in the temperature, whereas it was dramatically weakened by the increase in temperature for sulfonate superplasticizer, although the adsorption amount increased along with the temperature rise.

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force.