Compressive Strength, Hydration and Pore Structure of Alkali-Activated Slag Mortars Integrating with Recycled Concrete Powder as Binders

Wang, Hao; Wang, Liang; Shen, Wenfeng; Cao, Ke; Sun, Lei; Wang, Pengju; Cui, Liwen

doi:10.1007/s12205-021-0406-1

Cited by 26 publications

(11 citation statements)

References 57 publications

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“…Figure 3 displays the heat release of blended pastes with different amounts of CRCF. There was an initial reaction during the period of 0–0.5 h, involving the chemical reaction between Na 2 CO 3 and CRCF and the initial dissolution and wetting of the binders [ 2 ]. Ultimately, due to extended stirring, the heat release was not captured in the initial period.…”

Section: Resultsmentioning

confidence: 99%

“…Ordinary Portland cement (OPC) is the most extensively applied cementitious material for concrete production. The high CO 2 emission and consumption of raw materials, however, are created by OPC production, which results in serious environmental problems such as rising sea levels and global warming [ 1 , 2 ]. To relieve the increasing pressure in OPC production and thus reduce CO 2 emissions, the alkali-activated slag (AAS) binders produced by the reaction between alkaline activators and granulated blast furnace slag (GBFS) have been rapidly developed in the last few decades.…”

Section: Introductionmentioning

confidence: 99%

“…However, the workability, strength, and durability of concrete containing RCF would significantly decrease due to the high porosity and low reactivity of RCF [ 22 , 23 , 24 ]. Therefore, only a minimal amount of RCF can be utilized, and the rest is disposed of by landfilling and dumping, failing to take full advantage of waste resources and causing environmental and groundwater pollution [ 2 , 19 ]. It is noteworthy that the major components of RCF, including C-S-H gels, calcite (CaCO 3 ), quartz (SiO 2 ), Ca(OH) 2 [ 20 , 25 ], and the high content of CaO, can be obtained in the RCF after thermal treatment (800 °C) due to the decomposition of C-S-H, CaCO 3 , and Ca(OH) 2 .…”

Section: Introductionmentioning

confidence: 99%

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Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

Wang

et al. 2022

Materials

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Sodium carbonate (Na2CO3), an environmentally friendly activator, has been shown to have vast potential for the development of sustainable alkali-activated slag mortars. However, Na2CO3-activated slag mortars exhibit a delayed reaction process and limited early-age strength development, restricting their wider application. In this work, the recycled concrete fines were calcined at a temperature of 800 °C for 1 h and then used as an auxiliary activator to improve the reaction kinetics of Na2CO3-activated slag mortars. The impact of the calcined recycled concrete fines (CRCF) dosage and Na2CO3 concentration on the compressive strength, hydration kinetics, and phase assemblage of mortars was evaluated. The results show that CRCF can react directly with Na2CO3 in the early stages, swiftly removing the CO32− in aqueous solution and providing an alkaline environment suitable for the dissolution of slag. This promotes the development of C-(A)-S-H, hydrotalcite, hemicarbonate, and monocarbonate. The hydration process and strength-giving phase of mortars can be improved further, as an increase in Na2CO3 concentration increases the initial alkaline content. Additionally, the most remarkable compressive strength value of 39.2 MPa was observed at 28 days in the mortar with 6% sodium oxide equivalent (Na2O-E) of Na2CO3 and 15% CRCF because of the synergistic effect of CRCF and Na2CO3.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

Wang

et al. 2022

Materials

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“…Farhan and Nanayakkara [13,14] found that when the compressive strength of concrete prepared by combining an alkali-activated slag and a rebiotic after activator treatment was comparable, where the tensile strength was higher than that of plain concrete, but the internal structure and homogeneity were poorer. Wang [15] used recycled concrete powder to replace blast furnace slag in the preparation of an alkali-activated slag mortar. The results showed that the addition of the recycled concrete powder increased the compressive strength of the mortar, but it showed a negative effect on the 28-day strength.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Polyaluminium Chloride (Pac) Slag on the Properties of Recycled Concrete

Xu¹

2022

Ceramics - Silikaty

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In this paper, recycled concrete aggregates and PAC slag were used to prepare concrete. X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyse the micro-properties of the PAC and the concrete. Furthermore, the effects of the activators on the water absorption, compressive strength and frost resistance of the concrete were studied. The results showed that the effects of the activators on the water absorption were not obvious, but they could improve the activity of the PAC slag, thus, the hydration products in the mortar significantly increased and the micro-structure of the mortar became denser. Furthermore, the compressive strength of the concrete at 28 days increased by 26.5 % when the activator was mixed with 3% water glass and 3 % sodium sulfate. Moreover, the activators could improve the frost resistance of the concrete. However, when the activators were added in the concrete together, negative effects were found on the frost resistance of the concrete, with a mass loss of 20 %.

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“…Consuming of natural resources often leads to a large amount of construction and demolition wastes. In some countries, more than two billion tons of waste concrete were generated [19][20][21]. The random disposal of concrete wastes will cause a heavy burden on the environment.…”

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confidence: 99%

Recycling of Concrete Demolition Waste Powder as a Sustainable Material in Portland Cement Pastes Modified with Nano-silica

Darweesh

2022

JSMPM

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In recent years, researchers dedicated themselves to explore the possibility of introducingconcrete waste powder (CWP) into Portland cement as a sustainable material for Portland cement to reduce as possible the environmental pollution with this concrete demolition wastes. To optimize the effect of CWP on cement-based materials, this paper usesnano-silica (NS) to improve the hydration and mechanical properties of cement-based materials with CWP. Results indicated that after adding NS into CWP cement pastes, the setting time of cement pastes was significantly reduced, while the early rate of hydration and hydration heat increased. Besides, the mechanical strengths of the cement pastes increased as CWP replaced at the expense of the cement only up till 15 weights %, and then decreased. The addition of nanosilica (NS) can compensate the mechanical strength loss caused by CWP as supplementary cementing materials. The higher ratios of CWP than 15 weight % increased the pore volume or porosity. In contrast, NS in CWP blended cement significantly decreased the porosity, and increased the proportion of harmless pores. Hence, NS reduced the porosity, which in turn improved and enhanced the bulk density and mechanical properties. The optimum amount of NS is 2.5 weight % which resulted in the best results. The heat of hydration of the different cement batches in the two groups adversely affected with the incorporation of CWP, but little improved with NS. The obtained results were confirmed by the ultrasonic pulse velocity (USPV) test, where the cement batch PP15 (Group I) and PS2.5 (Group II) achieved the highest conformance.

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Compressive Strength, Hydration and Pore Structure of Alkali-Activated Slag Mortars Integrating with Recycled Concrete Powder as Binders

Cited by 26 publications

References 57 publications

Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

The Effects of Polyaluminium Chloride (Pac) Slag on the Properties of Recycled Concrete

Recycling of Concrete Demolition Waste Powder as a Sustainable Material in Portland Cement Pastes Modified with Nano-silica

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