Materials
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2021
·Vol. 15
·期 1
·271
·
IF 3.623
Woo Sung Yum,Juan Yu,Dongho Jeon,Haemin Song,Sungwon Sim,Do Hoon Kim,Jae Eun Oh
This study examined the mechanical and durability properties of CaO-activated ground-granulated blast-furnace slag (GGBFS) concretes made with three different additives (CaCl2, Ca(HCOO)2, and Ca(NO3)2) and compared their properties to the concrete made with 100% Ordinary Portland Cement (OPC). All concrete mixtures satisfied targeted air content and slump ranges but exhibited significantly different mechanical and durability properties. The CaO-activated GGBFS concretes showed different strength levels, depending on the type of additive. The added CaCl2was the most effective, but Ca(NO3)2was the least effective at increasing mechanical strength in the CaO-activated GGBFS system. The OPC concrete showed the most excellent freezing–thawing resistance in the durability test, but only the CaO-activated GGBFS concrete with CaCl2exhibited relatively similar resistance. In addition, the chemical resistance was significantly dependent on the type of acid solution and the type of binder. The OPC concrete had the best resistance in the HCl solution, while all CaO-activated GGBFS concretes had relatively low resistances. However, in the H2SO4solution, all CaO-activated GGBFS concretes had better resistance than the OPC concrete. All concrete with sulfate ions had ettringite before immersion. However, when they were immersed in HCl solution, ettringite tended to decrease, and gypsum was generated. Meanwhile, the CaO-activated GGBFS concrete with CaCl2did not change the type of reaction product, possibly due to the absence of ettringite and Ca(OH)2. When immersed in an H2SO4solution, ettringite decreased, and gypsum increased in all concrete. In addition, the CaO-activated concrete with CaCl2had a considerable amount of gypsum; it seemed that the dissolved C-S-H and calcite, due to the low pH, likely produced Ca2+ions, and gypsum formed from the reaction between Ca2+and H2SO4.Keywords:CaO-activation;auxiliary activator;GGBFS;chemical resistance;freezing;thawing
研究领域:
土木工程
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CONSTRUCTION AND BUILDING MATERIALS
·
2023
·
IF 7.4
Yanchen Oinam,Suhawn Ju,Myoungsu Shin,Sukhoon Pyo
This study aimed to investigate the influence of natural cellulose fibers (NCFs) on improving the hydration characteristics of cementless ultra-high performance concrete (UHPC) using CaO-activated ground granulated blast furnace slag (GGBFS). The NCFs were added in a saturated condition as an internal-curing agent so as to supply additional water to the UHPC matrix and subsequently increase the reactivity of unhydrated phases. To evaluate the hydration characteristics, saturated NCFs were added at 0 to 1.5 wt% of the GGBFS plus CaO. TGA and FTIR analyses showed that, as the amount of NCFs increased, the formation of hydration products was improved as evidenced by an increase in heat of hydration, indicating that more reactions of unhydrated phases occurred. Similarly, morphologies of the samples revealed the formation of hydration products on and near the surfaces of the NCFs due to the additional water exerted during the process of internal curing. Moreover, the compressive and tensile strengths were not compromised by the incorporation of weak and flexible NCFs, but rather a slight improvement was observed with a certain content of NCFs.
研究领域:
土木工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Developments in the Built Environment
·
2023
·
IF 8.2
Yanchen Oinam,Prabhat Vashishtha,Mandip Dahal,Sukhoon Pyo
This study investigates the potential use of calcined lime mud as an activator in the development of a sustainable, ground granulated blast furnace slag (GGBFS)-based cementless UHPC. The effects of the calcination temperature (550 °C to 850 °C) of lime mud and its weight percentage in the UHPC mixture were evaluated with various tests, such as compressive strength, isothermal calorimeter, and thermogravimetric analysis. Microstructural changes and pore size distribution were also analyzed using XRD, FTIR, and MIP. The results showed that calcined lime mud can be an effective activator in the UHPC mix, and its mechanical properties are influenced by the calcination temperature and weight percentage. The addition of 10% calcined lime mud enhanced the compressive strength of the UHPC up to 150 MPa without negatively affecting its microstructural and hydration characteristics, suggesting that calcined lime mud has the potential to be used as a sustainable alternative to CaO in GGBFS-based cementless UHPC.
✓ 已验证
产品关联
DOI
高影响因子
Journal of Building Engineering
·
2025
·
IF 7.4
Min-Chang Kang,Taekgeun Oh,Goeun Jun,Doo-Yeol Yoo,Sukhoon Pyo
This study investigated the effects of calcium formate as an accelerator in newly developed CaO-activated strain-hardening cementless composites (SH-CASC). Six doses of calcium formate, ranging from 0 to 5 % by weight of ground granular blast furnace slag (GGBFS) and calcium oxide, were tested. Thermogravimetric analysis, mercury intrusion porosimetry, hydration heat tests, compressive tests, single fiber pullout tests, direct tensile tests, and life cycle assessment (LCA) analyses of the SH-CASC were performed. The experiment results indicated that the incorporation of calcium formate enhanced the compressive strength of SH-CASC. Furthermore, calcium formate improved the bond strength between the matrix and fiber, resulting in higher tensile strength, strain capacity, and strain energy density. SH-CASC also showed a lower environmental footprint, with reduced carbon dioxide emissions and health hazards than cement- and cementless-based strain-hardening composites. Thus, SH-CASC presents a sustainable and promising composite material in the field of construction with good mechanical properties and environmental effects.
✓ 已验证
产品关联
DOI
高影响因子
Journal of Building Engineering
·
2023
·
IF 6.4
Mandip Dahal,Yanchen Oinam,Prabhat Vashistha,Jae-Eun Oh,Sukhoon Pyo
This study proposes an innovative approach to develop cementless ultra-high performance concrete (UHPC) by activating ground granulated blast furnace slag (GGBFS) without an alkaline-activating solution. To develop cementless UHPC, calcium oxide (CaO) (5% by weight) was used to activate GGBFS, and calcium formate (CF) was used as an accelerator at concentrations ranging from 0 to 6 wt%. The results showed that CF significantly improved the mechanical properties until 5 wt% and all the samples, including CF, exhibited a compressive strength of over 150 MPa. Uniaxial tensile tests revealed strain-hardening behavior, similar to typical cement-based UHPC. The addition of CF led to an increase in hydration products and pore size refinement, resulting in improved mechanical properties. The life cycle assessment results indicated that the developed UHPC mixture had nearly 70% lower CO 2 emission than cement-based UHPC. The experimental results highlight the potential of this method for sustainable UHPC development.
研究领域:
土木工程
·
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
CONSTRUCTION AND BUILDING MATERIALS
·
2020
·
IF 4.419
Woo Sung Yum,Jung-Il Suh,Do Hoon Kim,Jae Eun Oh
Recently, the combined use of calcium oxide (CaO) and calcium formate (Ca(HCOO) 2 ) has been proposed as an alternative activator for ground granulated blast furnace slag (GGBFS) (referred to as CaO-Ca(HCOO) 2 -activated GGBFS system). However, this clinker-free binder system produces calcium aluminate hydrate (C 2 AH 8 ), generally leading to the degradation of cementitious binder systems by its conversion to other phases. Thus, in this study, attempts to remove C 2 AH 8 from this system without losing the strength are suggested by the use of two additives (i.e., calcium sulfate (CaSO 4 ) and calcium nitrate (Ca(NO 3 ) 2 ), respectively). Results revealed that the above-mentioned additives completely remove C 2 AH 8 in the initial curing stage via its conversion to ettringite or NO 3 - and NO 2 -AFm, respectively. In addition, the additives reduced the extent of the total shrinkage and the standard deviation of strength results of triplicate samples. However, CaSO 4 exerted a beneficial effect on the strength, while Ca(NO 3 ) 2 exerted a marginal or detrimental effect on the strength. Therefore, this study suggested a new mixture form of an activator, comprising CaO , Ca(HCOO) 2 , and CaSO 4 , to activate GGBFS for maintaining strength without the conversion issue of C 2 AH 8 .
研究领域:
建筑材料学
·
材料科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）