{"title":"含两步热化学活化生物炭的胶凝复合材料中的碳固存","authors":"Sahana C. M, Souradeep Gupta","doi":"10.1016/j.cemconcomp.2025.106255","DOIUrl":null,"url":null,"abstract":"<div><div>Biochar (BC) activation can induce structural changes, which may enhance CO<sub>2</sub> sequestration and the engineering performance of biochar-based cementitious materials. In this research, the effect of biochar engineered under two conditions – (i) thermal treatment (TTBC) at 550 °C, 650 °C, and 750 °C respectively, and (ii) KOH- activation (KBC) at the mentioned temperatures and BC: KOH of 1:2, 1:3, and 1:4, on the hydration kinetics, CO<sub>2</sub> sequestration, structural changes, strength and shrinkage of biochar-cement composites is examined. KBC has a high macro-pore (>50 nm pores) volume and contains oxygenated groups, while TTBC is primarily aromatic and micro-porous (<2 nm pores). High surface area (190–237 m<sup>2</sup>/g), structural disorder, and the presence of oxygen-rich functional groups in KBC activated at 750 °C accelerate the hydration kinetics and enhance the total hydration of cement pastes by 30–51 % compared to pastes with TTBC and KBC prepared at 550 °C and 650 °C. KOH activation promotes carbon burn-off and increases meso- and macro-porosity of biochar, thus creating additional diffusion channels for CO<sub>2</sub>. This enhances the CO<sub>2</sub>-sequestration of biochar-cement by 17–45 % compared to TTBC. CO<sub>2</sub> sequestration in biochar-cement increases with a change in BC: KOH from 1:2 to 1:4, reducing the small and medium capillary pore volume by 40–71 %. This enhances the 1-day strength by 16–37 % and longer-term strength (after 1 year) by 22–45 %. Further, enlarged portlandite crystals are formed due to residual potassium (from KOH activation), which mitigates the total shrinkage by 15–38 %, enhancing the stability of activated biochar-based cementitious materials.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"164 ","pages":"Article 106255"},"PeriodicalIF":13.1000,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Carbon sequestration in cementitious composites containing two-step thermochemically activated biochar\",\"authors\":\"Sahana C. M, Souradeep Gupta\",\"doi\":\"10.1016/j.cemconcomp.2025.106255\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Biochar (BC) activation can induce structural changes, which may enhance CO<sub>2</sub> sequestration and the engineering performance of biochar-based cementitious materials. In this research, the effect of biochar engineered under two conditions – (i) thermal treatment (TTBC) at 550 °C, 650 °C, and 750 °C respectively, and (ii) KOH- activation (KBC) at the mentioned temperatures and BC: KOH of 1:2, 1:3, and 1:4, on the hydration kinetics, CO<sub>2</sub> sequestration, structural changes, strength and shrinkage of biochar-cement composites is examined. KBC has a high macro-pore (>50 nm pores) volume and contains oxygenated groups, while TTBC is primarily aromatic and micro-porous (<2 nm pores). High surface area (190–237 m<sup>2</sup>/g), structural disorder, and the presence of oxygen-rich functional groups in KBC activated at 750 °C accelerate the hydration kinetics and enhance the total hydration of cement pastes by 30–51 % compared to pastes with TTBC and KBC prepared at 550 °C and 650 °C. KOH activation promotes carbon burn-off and increases meso- and macro-porosity of biochar, thus creating additional diffusion channels for CO<sub>2</sub>. This enhances the CO<sub>2</sub>-sequestration of biochar-cement by 17–45 % compared to TTBC. CO<sub>2</sub> sequestration in biochar-cement increases with a change in BC: KOH from 1:2 to 1:4, reducing the small and medium capillary pore volume by 40–71 %. This enhances the 1-day strength by 16–37 % and longer-term strength (after 1 year) by 22–45 %. Further, enlarged portlandite crystals are formed due to residual potassium (from KOH activation), which mitigates the total shrinkage by 15–38 %, enhancing the stability of activated biochar-based cementitious materials.</div></div>\",\"PeriodicalId\":9865,\"journal\":{\"name\":\"Cement & concrete composites\",\"volume\":\"164 \",\"pages\":\"Article 106255\"},\"PeriodicalIF\":13.1000,\"publicationDate\":\"2025-07-28\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Cement & concrete composites\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0958946525003373\",\"RegionNum\":1,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"CONSTRUCTION & BUILDING TECHNOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Cement & concrete composites","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0958946525003373","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CONSTRUCTION & BUILDING TECHNOLOGY","Score":null,"Total":0}
Carbon sequestration in cementitious composites containing two-step thermochemically activated biochar
Biochar (BC) activation can induce structural changes, which may enhance CO2 sequestration and the engineering performance of biochar-based cementitious materials. In this research, the effect of biochar engineered under two conditions – (i) thermal treatment (TTBC) at 550 °C, 650 °C, and 750 °C respectively, and (ii) KOH- activation (KBC) at the mentioned temperatures and BC: KOH of 1:2, 1:3, and 1:4, on the hydration kinetics, CO2 sequestration, structural changes, strength and shrinkage of biochar-cement composites is examined. KBC has a high macro-pore (>50 nm pores) volume and contains oxygenated groups, while TTBC is primarily aromatic and micro-porous (<2 nm pores). High surface area (190–237 m2/g), structural disorder, and the presence of oxygen-rich functional groups in KBC activated at 750 °C accelerate the hydration kinetics and enhance the total hydration of cement pastes by 30–51 % compared to pastes with TTBC and KBC prepared at 550 °C and 650 °C. KOH activation promotes carbon burn-off and increases meso- and macro-porosity of biochar, thus creating additional diffusion channels for CO2. This enhances the CO2-sequestration of biochar-cement by 17–45 % compared to TTBC. CO2 sequestration in biochar-cement increases with a change in BC: KOH from 1:2 to 1:4, reducing the small and medium capillary pore volume by 40–71 %. This enhances the 1-day strength by 16–37 % and longer-term strength (after 1 year) by 22–45 %. Further, enlarged portlandite crystals are formed due to residual potassium (from KOH activation), which mitigates the total shrinkage by 15–38 %, enhancing the stability of activated biochar-based cementitious materials.
期刊介绍:
Cement & concrete composites focuses on advancements in cement-concrete composite technology and the production, use, and performance of cement-based construction materials. It covers a wide range of materials, including fiber-reinforced composites, polymer composites, ferrocement, and those incorporating special aggregates or waste materials. Major themes include microstructure, material properties, testing, durability, mechanics, modeling, design, fabrication, and practical applications. The journal welcomes papers on structural behavior, field studies, repair and maintenance, serviceability, and sustainability. It aims to enhance understanding, provide a platform for unconventional materials, promote low-cost energy-saving materials, and bridge the gap between materials science, engineering, and construction. Special issues on emerging topics are also published to encourage collaboration between materials scientists, engineers, designers, and fabricators.