Effect and mechanism of composite early-strength agents on sulfoaluminate cement-based UHPC

Zhou, Haijun; Qi, Xuan; Ma, Cong; Fang, Zefeng; Lou, Jianing; Chen, Haoyang; Guo, Xiang

doi:10.1016/j.cscm.2022.e01768

Cited by 9 publications

(3 citation statements)

References 57 publications

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“…For instance, the inclusion of calcium formate in the accelerator may lead to the formation of calcium sulfate precipitates within the AS accelerator, thereby causing instability. 13 The conventional approach to enhancing stability primarily involves the use of organic or inorganic acids to regulate the pH of the accelerator, thereby inhibiting the hydrolysis of Al 3+ . Hofman 14 utilized alkanol amine and either formic acid or acetic acid as stabilizers for accelerator.…”

Section: ■ Introductionmentioning

confidence: 99%

Utilizing the Adsorbability of Pseudoboehmite for Tailoring the Stability of an Aluminum Sulfate Alkali-free Accelerator for Shotcrete

Huang,

Wu,

et al. 2024

Langmuir

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Shotcrete is widely used in tunnels, bridges, culverts, and other large-scale projects. The accelerator is an additive employed to expedite the setting time of shotcrete. Previous research primarily concentrated on enhancing the early strength of accelerators, whereas their long-term stability has been inadequately investigated. In this study, pseudoboehmite (PB) and amorphous aluminum hydroxide (AAH) were incorporated into the accelerator to enhance its stability over a period of 90 days without any signs of crystallization or delamination. Furthermore, the accelerator exhibited an initial setting time of 170 s, a final setting time of 550 s, and a compressive strength of 11.58 MPa after 1 day. The mechanism of effects was studied by isothermal calorimetry, FTIR, XRD, TG-DTG, and SEM analysis. The enhancement in stability is attributed to the distinctive adsorption and thixotropic properties of PB, which facilitate the formation of an electrical double-layer structure in acidic solutions. The expedited setting and hardening are primarily due to the equilibrium between Al 3+ , SO 4 2− , and Ca 2+ ions, which accelerates the hydration process of cement. This research offers a methodology for developing a high-performance, alkali-free liquid accelerator.

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Section: ■ Introductionmentioning

confidence: 99%

Utilizing the Adsorbability of Pseudoboehmite for Tailoring the Stability of an Aluminum Sulfate Alkali-free Accelerator for Shotcrete

Huang,

Wu,

et al. 2024

Langmuir

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“…For example, the freeze-resistant fast-hardening concrete developed by Abdraimov Company has the characteristics of fast hardening and frost resistance [27], which is achieved by using fast-hardening and early strength special cement. Secondly, fast-hardening concrete can also be prepared using early strength agents, including nitrite, chloride, silicate, sulfate, and other inorganic salt early strength agents [28]. Research has shown that composite early strength agents can significantly improve their early strength performance.…”

Section: Introductionmentioning

confidence: 99%

Research into Preparation and Performance of Fast-Hardening RPC Mixed with Straw

et al. 2023

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Based on its characteristics of early strength, good toughness, and excellent mechanical and impact resistance, steel fiber-reinforced fast-hardening reactive powder concrete (RPC) is expected to become an alternative material used in the rapid repair of marine concrete structures. However, the steel fibers have also caused corrosion problems in coastal environments. To make doped fiber fast-hardening RPC more adaptable for use in ocean engineering, this study prepares fast-hardening RPC mixed with straw and studied the effects of straw content and curing age on its slump flow, setting time, and mechanical performance (flexural strength, compressive strength, and flexural toughness). The effects of straw addition on the compactness and hydration products of fast-hardening RPC were studied through macro- (ultrasonic analysis) and micro-scopic analysis (electron microscopy scanning and X-ray diffraction patterns). The straw content mentioned in this paper refers to the percentage of straw in relation to RPC volume. The results showed that straw reduced the fluidity of RPC slurry by 10.5–11.5% compared to concrete without straw, and it accelerated the initial setting of RPC slurry. When the straw content accounted for 1% of RPC volume, the setting rate was the fastest, with a increasing rate being 6–18%. Compared to concrete without straw, the flexural and compressive strength of fast-hardening RPC was enhanced by 3.7–30.5%. When the content was either 3% or 4%, the mechanical properties improved. Moreover, when the straw content accounted for 4% of RPC volume, the flexural toughness was the highest, with the increase rate being 21.4% compared to concrete without straw. Straw reduces the compactness of fast-hardening RPC.

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“…Some researchers have added composite early strength agents to cement-based materials and achieved some remarkable results. Haijun Zhou et al [16] investigated the effects of calcium formate, aluminum sulfate, lithium carbonate, and triethanolamine on the performance of sulfoaluminate cementbased ultra-high-performance concrete (UHPC), and the results showed that the four types of early strength agents shortened the setting time of UHPC and significantly increased its early strength; the 3d compressive strength reached 88.7 MPa. Yu Xin et al [17] used in situ XRD and isothermal calorimetry to study the effect of the inorganic salt early strength agents sodium thiocyanate, sodium sulfate, and sodium thiosulfate on the early hydration of cement, and found that the addition of three kinds of inorganic salt early strength agent within the appropriate dosing range can promote the hydration reaction of the clinker minerals C 3 S, C 3 A, and C 4 AF to varying degrees to accelerate the rate of the exothermic rate of hydration of the cement and, thus, increase the degree of early hydration of the cement.…”

Section: Introductionmentioning

confidence: 99%

Study on Early Hydration Mechanism of Double-Liquid Grouting Material Modified by Composite Early Strength Agent

Chen,

Wang,

Jiao

et al. 2023

Materials

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To achieve an adjustable setting time and significantly improved early strength of a new type of sulphoaluminate cement-based double-liquid grouting material (SACDL), the effects of calcium formate, sodium sulfate, lithium carbonate, and a composite early strength agent on the setting hardening and early hydration behavior of SACDL paste were studied by means of setting time, fluidity, compressive strength, and viscosity tests. The results showed that the adsorption and osmosis of calcium formate, the complex decomposition of sodium sulfate, the precipitation polarization of lithium carbonate and the synergistic action of the composite early strength agent could accelerate the early hydration rate of SACDL, shorten the coagulation time, and improve the early strength of SACDL. The composite effect of 0.8% calcium formate and 0.5% sodium sulfate is the most significant in promoting coagulation and early strength; the initial setting time and final setting time of the slurry were shortened to 5 min and 10 min, respectively; and the 3 h compressive strength was capable of reaching 16.7 MPa, 31% higher than that of the blank group. In addition, X-ray diffraction and SEM morphology observation were used to study the composition of the hydration products and the evolution of the microstructure, which revealed the early hydration mechanism of SACDL under the synergistic effect of the composite early strength agent: (1) The solubility of tricalcium aluminate (C3A) and dihydrate gypsum (CaSO4·2H2O) increased under the low content composite early strength agent condition, which increased the ettringite (AFt) formation rate. HCOO− was able to penetrate the hydration layers of tricalcium silicate (C3S) and dicalcium silicate (C2S), accelerating the dissolution of C3S and C2S and promoting the early hydration of SACDL. (2) Under the condition of a high dosage of the composite early strength agent, the further increase in Ca2+ concentration promoted the crystallization nodules and precipitation of CH and accelerated the formation of calcium silicate hydrate (C-S-H) gel. C-S-H was filled between a large number of rod-like AFt crystals, thus making the structure more dense.

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Effect and mechanism of composite early-strength agents on sulfoaluminate cement-based UHPC

Cited by 9 publications

References 57 publications

Utilizing the Adsorbability of Pseudoboehmite for Tailoring the Stability of an Aluminum Sulfate Alkali-free Accelerator for Shotcrete

Utilizing the Adsorbability of Pseudoboehmite for Tailoring the Stability of an Aluminum Sulfate Alkali-free Accelerator for Shotcrete

Research into Preparation and Performance of Fast-Hardening RPC Mixed with Straw

Study on Early Hydration Mechanism of Double-Liquid Grouting Material Modified by Composite Early Strength Agent

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