Effect of silicate modulus and alkali content on the microstructure and macroscopic properties of alkali-activated recycled powder mortar

Liu, Miao; Yang, Dingyi; Chen, Longxiang; Chen, Guangming; Ma, Zhiming

doi:10.1016/j.conbuildmat.2023.132365

Cited by 30 publications

(2 citation statements)

References 56 publications

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“…Under lower pH conditions, due to the slow dissolution of the regenerated micropowder, the reaction proceeds gradually, and the main hydration products are C-(A)-S-H gel and calcite (Equation ( 7)). As Mg 2+ enters the system through the incorporation of MgO, it accelerates the consumption of CO 3 2− in the system and generates a hydrotalcite phase [14] that can provide strength (Equation ( 8)). The hydration product is the same as N6M0, but the content of available magnesium ions in the system increases, and the contents of hydrotalcite and periclase increase.…”

Section: Hydration Mechanismmentioning

confidence: 99%

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Experimental Study on MgO-Na2CO3 Combined Excitation Recycled Fine-Powder-Slag Cementitious System and Modification

Liu,

Tian,

et al. 2024

Buildings

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The hydration mechanism and strength development of alkaline salt-activated cementitious materials primarily rely on the alkaline activators and mineral admixtures employed. However, the impact of increased Mg2+, Al3+, and Si4+ resulting from the addition of MgO and steel slag (SS) on the hydration mechanism of these systems remains undetermined. This study delves into the hydration mechanism and mechanical properties of a Na2CO3-MgO-activated regenerated micropowder-slag-based cementitious material system. Mechanical properties were assessed by measuring dry shrinkage and compressive strength at various ages, up to 28 days. The reaction mechanism was scrutinized using X-ray diffraction and a thermogravimetric analysis. The main reaction products contributing to the strength development are C-S-H, C-(A)-S-H gel, and hydrotalcite. Other carbonate-containing phases make smaller contributions. The findings reveal that when SS usage is at 10%, it yields higher early strength compared to ordinary samples. Samples incorporating MgO and SS achieved strengths similar to or surpassing those of the control samples. A noteworthy observation is the synergistic excitation effect between sodium carbonate (NC) and MgO, leading to the generation of a significant amount of gelling substances. These substances fill the pores of the structure, resulting in the formation of a dense microstructure. Consequently, the enhanced interaction between NC and MgO contributes to the overall strength development of the cementitious material.

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Section: Hydration Mechanismmentioning

confidence: 99%

“…Construction waste, the source of RFP, contains quartz, calcium hydroxide, calcite, and hydrated calcium silicate gel. However, the hydrated gelling material in RFP has low activity and can only play a filling role [14].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on MgO-Na2CO3 Combined Excitation Recycled Fine-Powder-Slag Cementitious System and Modification

Liu,

Tian,

et al. 2024

Buildings

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Study on the activity, phase, thermal decomposition characteristics, microstructure, and chemical element of hardened cement powder under heating temperature of 100°C~1200°C

Ge,

Song,

Quan

et al. 2024

Structural Concrete

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The properties of thermoactivated hardened cement powder (HCP) are of great significance for the recycling and utilization of concrete waste. This paper focuses on heating activation of HCP under the temperature between 100 and 1200°C. The activity, phase changes and microstructure of thermoactivated HCP were analyzed. The results showed that HCP with heating temperature between 1000 and 1200°C showed high activity. Under the conditions of heating activation at 1200°C, water–binder ratio of 0.38 and curing time of 30 days, the compressive strength of the specimen made of HCP reached 17.56 MPa. When the heating temperature is between 700 and 1200°C, CSH gel is gradually decomposed into C2S and C3S. The chemical reaction products of cement and thermoactivated HCP are similar, both containing CaCO3, Ca(OH)2, AFt, Hydrotalcite, etc. Compared to the diffraction peaks of hydrated cement, the diffraction peaks of thermoactivated HCP are broadened and dispersed. The high Ca/Si and Al/Si ratios in the chemical reaction products of thermoactivated HCP are important reasons for the decrease in its mechanical properties.

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Micro-properties and mechanical behavior of high-ductility engineered geopolymer composites (EGC) with recycled concrete and paste powder as green precursor

Wu,

Liu,

Wang

et al. 2024

Cement and Concrete Composites

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Effect of silicate modulus and alkali content on the microstructure and macroscopic properties of alkali-activated recycled powder mortar

Cited by 30 publications

References 56 publications

Experimental Study on MgO-Na2CO3 Combined Excitation Recycled Fine-Powder-Slag Cementitious System and Modification

Experimental Study on MgO-Na2CO3 Combined Excitation Recycled Fine-Powder-Slag Cementitious System and Modification

Study on the activity, phase, thermal decomposition characteristics, microstructure, and chemical element of hardened cement powder under heating temperature of 100°C~1200°C

Micro-properties and mechanical behavior of high-ductility engineered geopolymer composites (EGC) with recycled concrete and paste powder as green precursor

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