The ultrasonic pitch-catch experiment was conducted to study the hydration behavior of Portland cement paste with additive of sodium gluconate (SG) by using the tailor-made piezoelectric transducer. The X-ray diffraction (XRD) analysis shows that the intensity of the diffraction peak of Ca(OH) 2 decreases with increasing the SG content, especially when the SG content is larger than 0.1wt.%. The compressive strength of the hardening cement paste when SG content is larger than 0.05wt.% decreases remarkably. The ultrasonic waveforms appear at hydration age of 2 h, and amplitudes of waveform of the cement pastes with SG contents of 0.15wt.% and 0.2wt.% are obviously larger than those with SG content of 0.05wt.% in the early hydration stage. The hydration process of cement paste in 300 h can be classified into three stages based on the head wave amplitude variation, that is, the fluctuation variation period, the rapid increasing period and smooth increasing period. The acoustic propagation time changes greatly with hydration before hydration age of 48 h, indicating that the hydration and hardening process of the cement paste is violent in 48 h. The proposed ultrasonic monitoring method opens a new perspective for hydration behavior study of the cement paste with additive of sodium gluconate.
{"title":"Acoustic behavior of Portland cement paste with additive of sodium gluconate during hydration","authors":"Xu Dongyu, Chen Huaicheng, Hao Longlong, Zhao Hongyi, Guan Xuemao, Hu Yan, Sha Fei","doi":"10.1680/jadcr.23.00122","DOIUrl":"https://doi.org/10.1680/jadcr.23.00122","url":null,"abstract":"The ultrasonic pitch-catch experiment was conducted to study the hydration behavior of Portland cement paste with additive of sodium gluconate (SG) by using the tailor-made piezoelectric transducer. The X-ray diffraction (XRD) analysis shows that the intensity of the diffraction peak of Ca(OH) 2 decreases with increasing the SG content, especially when the SG content is larger than 0.1wt.%. The compressive strength of the hardening cement paste when SG content is larger than 0.05wt.% decreases remarkably. The ultrasonic waveforms appear at hydration age of 2 h, and amplitudes of waveform of the cement pastes with SG contents of 0.15wt.% and 0.2wt.% are obviously larger than those with SG content of 0.05wt.% in the early hydration stage. The hydration process of cement paste in 300 h can be classified into three stages based on the head wave amplitude variation, that is, the fluctuation variation period, the rapid increasing period and smooth increasing period. The acoustic propagation time changes greatly with hydration before hydration age of 48 h, indicating that the hydration and hardening process of the cement paste is violent in 48 h. The proposed ultrasonic monitoring method opens a new perspective for hydration behavior study of the cement paste with additive of sodium gluconate.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135591202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bouchra Bahja, L.H. Omari, A. Tizliouine, A. Elouafi, H. Salhi, Mohammed Chafi
Cement-based biocomposites are a current area of construction research. Plant fibres retard the setting times of cement due to their hydrophilic nature and the thermal properties of raw cement mortar containing plant fibres can be problematic. This aim of this work was to study the effect of fibre treatment to reduce the hydrophilicity of natural fibres while enhancing the thermal properties of the cementitious matrix. The first part of this study focused on structural and morphological aspects. Scanning electron microscopy showed a tiny calcium layer around the sisal fibre treated with sodium hydroxide and paraffin oil on the adhesion surface. Fourier transform infrared spectroscopy revealed a disparity in the peaks of the absorption bands of calcium carbonate and calcium hydroxide. The treatment slowed the alkaline hydrolysis and mineralisation of the fibre cell walls in the interfacial transition zone, thus promoting cement hydration. The second part of this work was a thermophysical study of the composites. The inclusion of sisal fibres led to remarkable decreases in thermal conductivity and heat capacity. The best thermal properties were obtained for the composite with sisal fibre immersed in paraffin oil. Biomortars with treated sisal fibre are thus promising from an insulation point of view.
{"title":"Effect of Sisal fiber's treatment on hydration and thermophysical properties of cement biocomposite","authors":"Bouchra Bahja, L.H. Omari, A. Tizliouine, A. Elouafi, H. Salhi, Mohammed Chafi","doi":"10.1680/jadcr.21.00167","DOIUrl":"https://doi.org/10.1680/jadcr.21.00167","url":null,"abstract":"Cement-based biocomposites are a current area of construction research. Plant fibres retard the setting times of cement due to their hydrophilic nature and the thermal properties of raw cement mortar containing plant fibres can be problematic. This aim of this work was to study the effect of fibre treatment to reduce the hydrophilicity of natural fibres while enhancing the thermal properties of the cementitious matrix. The first part of this study focused on structural and morphological aspects. Scanning electron microscopy showed a tiny calcium layer around the sisal fibre treated with sodium hydroxide and paraffin oil on the adhesion surface. Fourier transform infrared spectroscopy revealed a disparity in the peaks of the absorption bands of calcium carbonate and calcium hydroxide. The treatment slowed the alkaline hydrolysis and mineralisation of the fibre cell walls in the interfacial transition zone, thus promoting cement hydration. The second part of this work was a thermophysical study of the composites. The inclusion of sisal fibres led to remarkable decreases in thermal conductivity and heat capacity. The best thermal properties were obtained for the composite with sisal fibre immersed in paraffin oil. Biomortars with treated sisal fibre are thus promising from an insulation point of view.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135548630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Grid nanoindentation and quantitative X-ray diffraction are employed to provide quantitative information on phase constituents of nanoscale pozzolan-containing ultra-high-performance concrete (UHPC). Three UHPC samples containing nanoscale pozzolan and cured with and without microwave energy are investigated. The volume fraction of each phase constituent is independently evaluated using both techniques: nanoindentation (NI) and quantitative X-ray diffraction (QXRD). For the NI, the volumes have been evaluated by taking into account the thresholds characterising the phase constituents. The NI could assess phase mixtures or composites rather than single phases. The microwave-cured samples (CMW and CPMW) contain in total more hydration products that the sample that was not cured with microwave energy (C000). In all three samples, a nanocomposite (C–S–H/CHnm) consisting of high-density (HD) calcium silicate hydrate (C–S–H) and nanoscale portlandite (CH) is included, and its amount is more than double for the pressure-compacted and microwave-cured sample (CPMW). The heat curing by microwave energy together with the very low amount of water and restriction of the available space for hydration products, favour the formation of the nanocomposite (C–S–H/CHnm) in the CPMW sample.
{"title":"Phase volumes of ultra high performance concrete containing nanoscale pozzolan","authors":"A. Korpa, N. Dhamo, A. Andoni, C. Pritzel","doi":"10.1680/jadcr.21.00069","DOIUrl":"https://doi.org/10.1680/jadcr.21.00069","url":null,"abstract":"Grid nanoindentation and quantitative X-ray diffraction are employed to provide quantitative information on phase constituents of nanoscale pozzolan-containing ultra-high-performance concrete (UHPC). Three UHPC samples containing nanoscale pozzolan and cured with and without microwave energy are investigated. The volume fraction of each phase constituent is independently evaluated using both techniques: nanoindentation (NI) and quantitative X-ray diffraction (QXRD). For the NI, the volumes have been evaluated by taking into account the thresholds characterising the phase constituents. The NI could assess phase mixtures or composites rather than single phases. The microwave-cured samples (CMW and CPMW) contain in total more hydration products that the sample that was not cured with microwave energy (C000). In all three samples, a nanocomposite (C–S–H/CHnm) consisting of high-density (HD) calcium silicate hydrate (C–S–H) and nanoscale portlandite (CH) is included, and its amount is more than double for the pressure-compacted and microwave-cured sample (CPMW). The heat curing by microwave energy together with the very low amount of water and restriction of the available space for hydration products, favour the formation of the nanocomposite (C–S–H/CHnm) in the CPMW sample.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134951516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effects of curing temperature (20°C, 40°C and 60°C) and the addition of limestone powder (LP) (6% and 12%) on the capillary water absorption (CWA) of high-volume fly ash (HVFA) cement mortar were investigated. X-ray diffraction analysis and tests for chemically bound water content (CBWC), compressive strength and porosity were also conducted. It was found that, for a fly ash (FA) content exceeding 30%, the CWA increased significantly. When the FA content was 50%, the curing temperature was raised to 40°C or the LP content was 12%, the CBWC increased greatly. Increasing the curing temperature or adding LP increased the compressive strength and decreased the porosity of the HVFA cement mortar. Prediction of the water penetration depth in the HVFA cement mortar was consistent with the CWA results. The results of this work indicate that an increase in curing temperature or the addition of LP could be an efficient way of improving the CWA performance of HVFA cement mortar.
{"title":"Improving capillary water absorption of high-volume fly ash mortar by curing temperature and limestone addition","authors":"Yunfei Di, Haitao Zhao, Xiaoxiong Li, Yun Chen, Zhenqing Shi, Xiaolei Man","doi":"10.1680/jadcr.23.00025","DOIUrl":"https://doi.org/10.1680/jadcr.23.00025","url":null,"abstract":"The effects of curing temperature (20°C, 40°C and 60°C) and the addition of limestone powder (LP) (6% and 12%) on the capillary water absorption (CWA) of high-volume fly ash (HVFA) cement mortar were investigated. X-ray diffraction analysis and tests for chemically bound water content (CBWC), compressive strength and porosity were also conducted. It was found that, for a fly ash (FA) content exceeding 30%, the CWA increased significantly. When the FA content was 50%, the curing temperature was raised to 40°C or the LP content was 12%, the CBWC increased greatly. Increasing the curing temperature or adding LP increased the compressive strength and decreased the porosity of the HVFA cement mortar. Prediction of the water penetration depth in the HVFA cement mortar was consistent with the CWA results. The results of this work indicate that an increase in curing temperature or the addition of LP could be an efficient way of improving the CWA performance of HVFA cement mortar.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135656933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Usha Sharma, Reetam Chaudhury, Lok Pratap Singh, Chi-Sun Poon
Concrete technologists use different types of additives such as fly ash, slag, natural pozzolans and nanomaterials toenhance concrete performance and durability. However, a detailed explanation of the early-age hydration process and microstructural modification of concrete in the presence of nanomaterials remains to be presented and extensive research is required for strategic modification of cementitious systems. This study focused on the precise monitoring of early-age hydration with the incorporation of nanoalumina (nAl) in tricalcium silicate (C3S) and Portland cement paste and mortar. The dosage of nAl was varied from 1 to 5% (by weight) in C3S and from 0.1 to 1.0% in Portland cement, with a water/cement ratio of 0.4. The hydration studies showed that the nAl increased the cross-linkage in calcium silicate hydrate gel through substitution of aluminium by silicon, which was responsible for the enhancement of the modulus of elasticity (by 40%) with 1.0% nAl) after 7 days of hydration. In summary, the incorporation of nAl modified the concrete microstructure in the initial days of hydration, leading to higher concrete performance and longer service lives of concrete structures.
{"title":"Early hydration studies of cementitious materials incorporating nanoalumina","authors":"Usha Sharma, Reetam Chaudhury, Lok Pratap Singh, Chi-Sun Poon","doi":"10.1680/jadcr.22.00190","DOIUrl":"https://doi.org/10.1680/jadcr.22.00190","url":null,"abstract":"Concrete technologists use different types of additives such as fly ash, slag, natural pozzolans and nanomaterials toenhance concrete performance and durability. However, a detailed explanation of the early-age hydration process and microstructural modification of concrete in the presence of nanomaterials remains to be presented and extensive research is required for strategic modification of cementitious systems. This study focused on the precise monitoring of early-age hydration with the incorporation of nanoalumina (nAl) in tricalcium silicate (C<sub>3</sub>S) and Portland cement paste and mortar. The dosage of nAl was varied from 1 to 5% (by weight) in C<sub>3</sub>S and from 0.1 to 1.0% in Portland cement, with a water/cement ratio of 0.4. The hydration studies showed that the nAl increased the cross-linkage in calcium silicate hydrate gel through substitution of aluminium by silicon, which was responsible for the enhancement of the modulus of elasticity (by 40%) with 1.0% nAl) after 7 days of hydration. In summary, the incorporation of nAl modified the concrete microstructure in the initial days of hydration, leading to higher concrete performance and longer service lives of concrete structures.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138509761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The chemical debonding energy, initial interfacial frictional bond strength and slip-hardening coefficient between polyvinyl alcohol (PVA) fibres and an engineered cementitious composite (ECC) matrix were obtained by means of single PVA fibre pull-out tests. The effect of three moisture states (fully saturated, semi-saturated and fully dry) on the bonding properties between the PVA fibre and ECC matrix at three target temperatures (25°C, 0°C and −20°C) was investigated. It was found that, at 25°C, the bonding properties decreased with an increase in moisture content. At 0°C and −20°C, the bonding properties increased with an increase in moisture content. At −20°C in the fully saturated state, the bonding load was too large to cause fibre rupture. The bonding properties were found to increase with decreasing temperature in the fully saturated and semi-saturated states and decrease with decreasing temperature in the fully dry state. This study of the effect of low temperature and moisture state on the bonding properties between PVA fibres and ECCs provides theoretical support for how to ensure good ductility when ECCs are in service at low temperature.
{"title":"Effect of low temperature and moisture on bond properties of PVA fibres and engineered cementitious composite matrix","authors":"Shuling Gao, Qing Wang","doi":"10.1680/jadcr.22.00003","DOIUrl":"https://doi.org/10.1680/jadcr.22.00003","url":null,"abstract":"The chemical debonding energy, initial interfacial frictional bond strength and slip-hardening coefficient between polyvinyl alcohol (PVA) fibres and an engineered cementitious composite (ECC) matrix were obtained by means of single PVA fibre pull-out tests. The effect of three moisture states (fully saturated, semi-saturated and fully dry) on the bonding properties between the PVA fibre and ECC matrix at three target temperatures (25°C, 0°C and −20°C) was investigated. It was found that, at 25°C, the bonding properties decreased with an increase in moisture content. At 0°C and −20°C, the bonding properties increased with an increase in moisture content. At −20°C in the fully saturated state, the bonding load was too large to cause fibre rupture. The bonding properties were found to increase with decreasing temperature in the fully saturated and semi-saturated states and decrease with decreasing temperature in the fully dry state. This study of the effect of low temperature and moisture state on the bonding properties between PVA fibres and ECCs provides theoretical support for how to ensure good ductility when ECCs are in service at low temperature.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136297047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：