Accelerators for normal concrete: A critical review on hydration, microstructure and properties of cement-based materials

Wang, Yifei; Lei, Lei; Liu, Jianhui; Ma, Yihan; Liu, Yi; Xiao, Zhiqiang; Shi, Caijun

doi:10.1016/j.cemconcomp.2022.104762

Cited by 51 publications

(14 citation statements)

References 64 publications

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“…Moreover, a selection of accelerators specially used in shotcrete have also been revised and their effects on hydration, microstructure and properties were analysed [ 11 ]. Very recently, admixtures to be used in normal concrete have been classified in chloride-based accelerators and in non-chloride accelerators, putting emphasis in their effects for durability [ 12 ]. The accelerators for cast and sprayed concretes were also revised highlighting the influence of the dosage on the aluminate and silicate hydration reactions [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in C-S-H Nucleation Seeding for Improving Cement Performances

et al. 2023

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Reducing cement CO2 footprint is a societal need. This is being achieved mainly by replacing an increasing amount of Portland clinker by supplementary cementitious materials. However, this comes at a price: lower mechanical strengths at early ages due to slow pozzolanic reaction(s). This is being addressed by using accelerator admixtures. In this context, calcium silicate hydrate nucleation seeding seems to have a promising future, as it can accelerate cement and pozzolanic reactions at early ages, optimising their microstructures, without compromising late strength and durability performances. In fact, these features could even be improved. Moreover, other uses are low temperature concreting, precasting, shotconcrete, etc. Here, we focus on reviewing recent reports on calcium silicate hydrate seeding using commercially available admixtures. Current knowledge on the consequences of nucleation seeding on hydration reactions and on early and late mechanical strengths is discussed. It is noted that other features, in addition to the classic alite hydration acceleration, are covered here including the enhanced ettringite precipitation and the very efficient porosity refinement, which take place in the seeded binders. Finally, because the seeded binders seem to be denser, durability properties could also be enhanced although this remains to be properly established.

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Section: Introductionmentioning

confidence: 99%

Recent Advances in C-S-H Nucleation Seeding for Improving Cement Performances

et al. 2023

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“…38 On the other hand, the chlorides in the pore solution promote the formation of flocculated hydrophilic calcium silicate hydrate, facilitating faster diffusion of ions, which also accelerates cement hydration. 64 The ash 2 remains finer than cement after treatment (D v 50 = 6.36 μm) and releases no chloride in the synthetic pore solution (Figure 4a) but delays cement hydration due to increased Zn release in the synthetic pore solution (Figure S8a). The untreated ash 3 also releases chloride in the synthetic pore solution; however, it delays cement hydration slightly (Figure S8b).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Reducing Pb and Cl Mobility in Waste-to-Energy Fly Ashes via Chlorellestadite Formation

Kumar,

Baral,

Roesler

et al. 2024

ACS EST Eng.

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Sustainably sourced development minerals are vital to meeting the demand for low-carbon construction materials. A potential waste material that can be a low-carbon construction material for cementitious systems is waste-to-energy fly ash (WTE ash), a byproduct of waste incineration. WTE ash contains chloride-bearing species and heavy metals, which can promote steel reinforcement corrosion and present long-term leaching risks.Here, we present a new multistep ash treatment protocol involving dissolution and heating to transform the nonreadily removable chlorides in WTE ash to chlorellestadite [Ca 10 (SiO 4 ) 3 (SO 4 ) 3 Cl 2 ]. Our results suggest that this transformation significantly reduces chloride release from WTE ash in an alkaline cement-like environment by over 2 orders of magnitude, from 1500 mg/L to less than 10 mg/L. This transformation also significantly reduces Pb mobility after treatment (from >5 mg/L to <0.5 mg/L), likely caused by the crystallo-chemical incorporation of Pb in chlorellestadite. In contrast to the existing ash treatment methods, the proposed ash treatment protocol minimizes heavy metals volatilization while simultaneously reducing Pb mobility and chloride release through chlorellestadite formation. These findings overcome limitations preventing the commercial use of WTE ash and thus opening up pathways toward a circular economy.

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“…In the realm of cement, accelerators have often been characterized as combinations of amines and ammonium compounds. 49,50 And the stearic acid emulsion obtained by using ammonia water as a pH regulator also promotes coagulation. This causes the modified mortar's ultimate setting time to be accelerated.…”

Section: The Application Of Stearic Acid Emulsions In Mortarmentioning

confidence: 99%

A ultra‐low viscosity stearic acid emulsion prepared by lauric acid as waterproof agent for cement mortar

Huang,

Wu,

Wang

et al. 2023

J of Applied Polymer Sci

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Safe building structures cannot be achieved without reliable waterproofing engineering. To address the susceptibility of concrete materials to water leakage, a low‐viscosity stearic acid emulsion has been developed as a waterproofing agent for mortar. By introducing lauric acid, the formation of stearic acid crystals in water could be effectively prevented, resulting in a stearic acid emulsion with a viscosity of only 24 mPa·s. It is found that the best overall performance was achieved when the ratio (R) of lauric acid to stearic acid was 2/3. This emulsion has the least effect on mortar fluidity and setting time. The as‐prepared modified mortar possessed the highest compressive strength (127% of the blank) and the lowest water absorption at 48 h (37% of the blank). X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), energy‐dispersive x‐ray spectroscopy (EDS), scanning electron microscopy (SEM), dynamic light scattering (DLS) particle size analysis, and water contact angle measurements were used to investigate the mechanism of stearic acid emulsion's modification. It is determined that the stearic acid emulsions successfully modified the internal and external hydrophobicity of the mortar by chemical action with calcium hydroxide.

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Accelerators for normal concrete: A critical review on hydration, microstructure and properties of cement-based materials

Cited by 51 publications

References 64 publications

Recent Advances in C-S-H Nucleation Seeding for Improving Cement Performances

Recent Advances in C-S-H Nucleation Seeding for Improving Cement Performances

Reducing Pb and Cl Mobility in Waste-to-Energy Fly Ashes via Chlorellestadite Formation

A ultra‐low viscosity stearic acid emulsion prepared by lauric acid as waterproof agent for cement mortar

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