Synergistic Effect and Mechanism of Nano-C-S-H Seed and Calcium Sulfoaluminate Cement on the Early Mechanical Properties of Portland Cement

Abstract

The combined utilization of mineral accelerators and nano-seeding materials is a novel method to promote the early strength of cement-based materials. In this paper, the effects of nano-C-S-H seed (NCS) on the early compressive strength of the Portland cement (PC)– calcium sulfoaluminate cement (CSA) binder were investigated. The results showed that NCS and CSA synergistically contributed to the early strength of PC. In detail, a 326.3% increase in the 10 h compressive strength of PC paste was obtained through the addition of NCS (2 wt%) and CSA (5%) in common. This was higher than the sum of the increases observed with the single additions of CSA (157.9%) or NCS (87.6%), with the same above dosage, in PC. Meanwhile, the early strength enhancement effects of NCS and CSA, when used together in PC, lasted longer than the effects of either used alone. Moreover, the synergetic effect mechanism was analyzed by isothermal calorimeter, QXRD, TGA, MIP, and SEM techniques. The calorimetry, XRD, and TGA results demonstrated that the synergistic mechanism was associated with the synergistic promotion effects of CSA and NCS on the hydrates. The fast hydration of CSA produced large amounts of ettringite and also consumed partial free water to promote the performance of the seeding effect of NCS which, simultaneously, further accelerated the precipitation of C-S-H gel and CH. The high alkie environment was also beneficial for the continuous generation of ettringite. In addition, the results of MIP and SEM measurements showed that the micro-filling effect of NCS significantly optimized the pore structure of a PC-CSA blend-hardened paste. Thus, the synergistic strength enhancement effects of CSA and NCS on PC were attributed to the matching of the promotion of hydration generation and the optimization of pore structures in hardening cement paste. The results of this article provide a new approach to achieving the rapid development of the early strength of cementitious materials, with potential applications in precast concrete and low-temperature construction.

Study on the Effect of Three Types of Calcium Sulfate on the Early Hydration and Workability of Self-Compacting Repair Mortar

“…The C 4 A 3 minerals in SAC and the C 3 S minerals in PC have a mutually encouraging impact on the common hydration process when sulfoaluminate cement and silicate cement are combined, hastening the hydration and setting of the combined cement [ 15 ]. Calcite alumina (AFt), aluminum gel, C-S-H gel, and a minor amount of low-sulfur hydrated calcium sulfoaluminate are the major hydration products of this composite system [ 16 , 17 , 18 ]. The early strength of the system is provided by the creation of AFt, while the development of C-S-H gels ensures the later increase in cement strength [ 13 , 19 ].…”

Effect of Water Reducing Agent and Retarder on Properties of Ternesite-Calcium Sulfoaluminate Cement Synthesized at Low Temperatures

“…Moreover, since the cement used industrial wastes as raw materials and was prepared at a low temperature of 1200°C, the resources are reduced. Energy consumption reduces CO 2 emissions and has the potential to replace Portland cement (Chang et al 2019;Li and Chang 2019;Tang et al 2018). However, compared with ordinary Portland cement, this cement has a shorter setting time and lower fluidity (Shen et al 2019).…”

“…However, due to the rapid hydration of C 4 A 3 $, the flow properties of the pastes will be unable to meet the requirements of long-term construction of concrete, when only water reducer is used for sulphoaluminate cement (CSA). Therefore, the combination of water reducing agent and retarder can play a role of both improving the mechanical strength of cement and satisfying the working properties of the pastes (Tang et al 2018;Ke and Zhang 2020). CSA cement commonly includes three types of set retarders: borax, citric acid, and sodium gluconate.…”

“…β-cyclodextrin is the product of partial hydrolysis of starch, and the production process is green. Tang et al (2018) and Hang et al (2022). found that the combination of polycarboxylate superplasticizer and βcyclodextrin, in high belite calcium sulphoaluminate cement, can effectively prolong the setting time of cement paste and improve its fluidity.…”