Evaluating soundness of concrete containing shrinkage-compensating MgO admixtures

Kabir, Hossein; Hooton, RD

doi:10.1016/j.conbuildmat.2020.119141

Cited by 39 publications

(15 citation statements)

References 22 publications

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“…Generally, several strategies are utilized to control temperature and prevent cracks in practical engineering, including the adoption of pre-cooling aggregate and ice water, a pipe cooling method by circulating cold water through internal pipes during the concrete hardening stage [11], and the usage of a certain dosage of fly ash [12][13][14][15], fibers [16][17][18][19][20][21][22][23], and a magnesia expansion agent (abbreviated as MgO thereafter) [24][25][26][27][28][29][30]. However, the pre-cooling method and pipe cooling method need some additional labor as well as more construction time and cost [11].…”

Section: Introductionmentioning

confidence: 99%

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

Wang

Liu

et al. 2022

Fractal Fract

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Currently, low heat Portland (LHP) cement is widely used in mass concrete structures. The magnesia expansion agent (MgO) can be adopted to reduce the shrinkage of conventional Portland cement-based materials, but very few studies can be found that investigate the influence of MgO on the properties of LHP cement-based materials. In this study, the influences of two types of MgO on the hydration, as well as the shrinkage behavior of LHP cement-based materials, were studied via pore structural and fractal analysis. The results indicate: (1) The addition of reactive MgO (with a reactivity of 50 s and shortened as M50 thereafter) not only extends the induction stage of LHP cement by about 1–2 h, but also slightly increases the hydration heat. In contrast, the addition of weak reactive MgO (with a reactivity of 300 s and shortened as M300 thereafter) could not prolong the induction stage of LHP cement. (2) The addition of 4 wt.%–8 wt.% MgO (by weight of binder) lowers the mechanical property of LHP concrete. Higher dosages of MgO and stronger reactivity lead to a larger reduction in mechanical properties at all of the hydration times studied. M300 favors the strength improvement of LHP concrete at later ages. (3) M50 effectively compensates the shrinkage of LHP concrete at a much earlier time than M300, whereas M300 compensates the long-term shrinkage more effectively than M50. Thus, M300 with an optimal dosage of 8 wt.% is suggested to be applied in mass LHP concrete structures. (4) The addition of M50 obviously refines the pore structures of LHP concrete at 7 days, whereas M300 starts to refine the pore structure at around 60 days. At 360 days, the concretes containing M300 exhibits much finer pore structures than those containing M50. (5) Fractal dimension is closely correlated with the pore structure of LHP concrete. Both pore structure and fractal dimension exhibit weak (or no) correlations with shrinkage of LHP concrete.

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Section: Introductionmentioning

confidence: 99%

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

Wang

Liu

et al. 2022

Fractal Fract

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“…Researchers have found that the addition of a retarder [18] and HCSA [19][20][21] will help cement hydration products to form a good spatial structure and improve the strength of cement, while the addition of PCE has a dispersing effect on cement particles and can improve the workability of cement and reduce unit water consumption [22,23]. In a case where the interaction of various additives to the ultrafine cement and their influences on its strength and expansibility are unknown, the single factor experiment method can be used in preliminary experiments to determine the optimal dosage ranges.…”

Section: Experimental Methodmentioning

confidence: 99%

Fluidity Influencing Factors Analysis and Ratio Optimization of New Sealing Materials Based on Response Surface Method

Guo

Xue

et al. 2021

Geofluids

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The borehole sealing material is one of the key factors affecting the gas drainage effect of a borehole. This paper takes the compressive strength, fluidity, expansion rate, and setting time of the sealing material as the main research indicators and explores the influence of each key influencing factor on the performance of the high-fluid sealing material through the single factor experiment method. Using the Design-Expert 8.0.5 Trial software designed orthogonal experiments and establishing a quadratic model between liquidity and each test factor, which showed the impact of each key factor on the fluidity. Finally, by adjusting the amount of admixtures, the optimal ratio of high-fluidity borehole sealing materials was obtained. The results showed that the key factors had the following order of significance: water – cement reducing agent > water – cement ratio > retarder > expansion agent . With the water-cement ratio and the amount of water reducing agent increase, the fluidity of the material will increase; and with the increase of the retarder and expansion agent, the fluidity will decrease. In actual use, the fluidity is the main factor, but the expansion rate, compressive strength, and setting time are also considered. The optimal percentages were found for the high-fluidity borehole sealing material: a water-cement ratio of 1, along with 0.03% retarder, 0.5% water reducer, and 8% expansion agent. These research results could provide a reference for improving the performance of gas drainage borehole sealing materials and enhancing the effect of gas drainage.

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“…Based on the existing literature, some studies have been performed on the mechanical properties, shrinkage, and hydration process of concrete prepared using expanded cement [21][22][23][24][25][26][27][28]. Péra and Ambroise observed good quality strength development in concrete containing expanded cement [24].…”

Section: Literature Review and Study Motivationmentioning

confidence: 99%

Effects of Shrinkage Reducing Agent and Expanded Cement on UHPC Fluidity, Mechanical Properties, and Shrinkage Performance

Wang¹,

Gong

Chen³

et al. 2021

Advances in Materials Science and Engineering

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The purpose of this study was to evaluate the effects of a shrinkage reducing agent (SRA) and Portland expanded cement (PEC) on the fluidity, mechanical properties, and shrinkage performance of ultrahigh-performance concrete (UHPC). The results indicated that the fluidity of the fresh UHPC mortar initially decreased and then increases along as a function of SRA dosage. When the dosage of SRA was 1%, the UHPC mortar fluidity was at its minimum. For dosages exceeding 1%, the additional water-binder ratio of the mortar increased, which in turn increased the UHPC fluidity. That is, the SRA delayed the cement hydration and increased the setting time, which is not conducive for early strength development of UHPC. As the SRA dosage was increased (i.e., 0%–2%), the autogenous shrinkage of UHPC decreased significantly such that even a small dosage of about 0.5% SRA was able to effectively reduce drying shrinkage. From the study results, it was also observed that PEC accelerated the loss of fluidity in the fresh UHPC and concurrently promoted the early strength development of UHPC. At 75% PEC content, the strength enhancement effects tended to be stable. This means that although the addition of PEC will potentially increase the autogenous shrinkage of UHPC, it has the positive effect of inhibiting drying shrinkage provided that the PEC dosage is controlled within the 25%–50% range. Furthermore, morphological analyses using a scanning electron microscope (SEM) indicated that an increase in the SRA dosage loosens the UHPC microstructure, with the formation of the hydration products remaining incomplete, thus ultimately causing the UHPC strength to decrease. Overall, the study findings indicated that 2% SRA and 25%–50% PEC can effectively reduce the shrinkage of UHPC and are, therefore, recommended as the optimum dosages.

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Evaluating soundness of concrete containing shrinkage-compensating MgO admixtures

Cited by 39 publications

References 22 publications

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

Fluidity Influencing Factors Analysis and Ratio Optimization of New Sealing Materials Based on Response Surface Method

Effects of Shrinkage Reducing Agent and Expanded Cement on UHPC Fluidity, Mechanical Properties, and Shrinkage Performance

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