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reducing admixtures having different action mechanisms on mechanical and durability performance of cementitious

《结构与土木工程前沿（英文）》 2021年 第15卷 第5期   页码 1277-1291 doi: 10.1007/s11709-021-1752-2

摘要： In this paper, the effect of usage of the permeability reducing admixture (PRA) having different action mechanisms on hardened state properties of cementitious systems containing mineral additives is examined. For this aim, three commercial PRAs were used during investigation. The effective parameters in the first and third PRAs were air-entraining and high-rate air-entraining, respectively. The second one contained the insoluble calcium carbonate residue and had a small amount of the air-entraining property. Mortar mixes with binary and ternary cementitious systems were prepared by partially replacing cement with fly ash and metakaolin. The hardened state properties of mortar mixtures such as compressive strength, ultrasonic pulse velocity, water absorption, drying shrinkage and freeze–thaw resistance were investigated. The ternary cement-based mixture having both fly ash and metakaolin was selected as the most successful mineral-additive bearing mix in regard to hardened state properties. In this sense, PRA-B, with both insoluble residues and a small amount of air-entraining properties, showed the best performance among the mixtures containing PRA. The combined use of mineral additive and PRA had a more positive effect on the properties of the mixes.

关键词： cementitious system     mineral additive     permeability reducing admixture     mechanical properties     durability performance    

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Strengthening of the concrete face slabs of dams using sprayable strain-hardening fiber-reinforced cementitious

《结构与土木工程前沿（英文）》 2022年 第16卷 第2期   页码 145-160 doi: 10.1007/s11709-022-0806-4

摘要： In this study, sprayable strain-hardening fiber-reinforced cementitious composites (FRCC) were applied to strengthen the concrete slabs in a concrete-face rockfill dam (CFRD) for the first time. Experimental, numerical, and analytical investigations were carried out to understand the flexural properties of FRCC-layered concrete slabs. It was found that the FRCC layer improved the flexural performance of concrete slabs significantly. The cracking and ultimate loads of a concrete slab with an 80 mm FRCC layer were 132% and 69% higher than those of the unstrengthened concrete slab, respectively. At the maximum crack width of 0.2 mm, the deflection of the 80-mm FRCC strengthened concrete slab was 144% higher than that of the unstrengthened concrete slab. In addition, a FE model and a simplified analytical method were developed for the design and analysis of FRCC-layered concrete slabs. Finally, the test result of FRCC leaching solution indicated that the quality of the water surrounding FRCC satisfied the standard for drinking water. The findings of this study indicate that the sprayable strain-hardening FRCC has a good potential for strengthening hydraulic structures such as CFRDs.

关键词： strain-hardening cementitious composites     engineered cementitious composites     sprayable     shotcrete     strengthening     concrete-face rockfill dam     digital image correlation    

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Effect of natural pozzolan content on the properties of engineered cementitious composites as repair

Said CHOUCHA, Amar BENYAHIA, Mohamed GHRICI, Mohamed Said MANSOUR

《结构与土木工程前沿（英文）》 2018年 第12卷 第3期   页码 261-269 doi: 10.1007/s11709-017-0394-x

摘要：

In order to determine the effect of Natural Pozzolan (NP) content on the mechanical properties and durability characteristics on Engineered Cementitious Composites (ECC) as repair material. This study focused on the evaluation of the most factors influencing compatibility between the repair material and the base concrete including mechanicals properties such as, compressive and flexural strengths, elastic modulus, capillary absorption and drying shrinkage. The experimental results showed that natural pozzolan reduces the compressive strength and the flexural strength of ECC at all ages. The elastic modulus of ECC was remarkably lower than that of normal-strength concrete. This lower Young’s modulus is desirable for repair concrete, because it prevents the stresses induced by restrained shrinkage. In addition, the incorporation of high-volume natural pozzolan decreases significantly the coefficient of capillary absorption at long term and increases the drying shrinkage. Generally, based on the results obtained in the present experimental investigation, ECC can be used effectively as an overlay material over existing parent concrete.

关键词： natural pozzolan     engineered cementitious composites     mechanical strengths     elastic modulus     capillary absorption     drying shrinkage    

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Strengthening of reinforced concrete beams using fiber-reinforced cementitious matrix systems fabricated

《结构与土木工程前沿（英文）》   页码 1100-1116 doi: 10.1007/s11709-023-0967-9

摘要： The performance of a new fiber-reinforced cementitious matrix (FRCM) system developed using custom-designed mortar and fabrics is investigated in this study. The behavior of this system is evaluated in terms of both the flexural and shear strengthening of reinforced concrete beams. Eight beams are designed to assess the effectiveness of the FRCM system in terms of flexural strengthening, and four specimens are designed to investigate their shear behavior. The parameters investigated for flexural strengthening are the number of layers, span/depth ratio, and the strengthening method. Unlike previous studies, custom fabrics with similar axial stiffness are used in all strengthening methods in this study. In the shear-strengthened specimens, the effects of the span/depth ratio and strengthening system type (fiber-reinforced polymer (FRP) or FRCM) are investigated. The proposed FRCM system exhibits desirable flexural and shear strengthening for enhancing the load capacity, provides sufficient bonding with the substrate, and prevents premature failure modes. Considering the similar axial stiffness of fabrics used in both FRCM and FRP systems and the higher load capacity of specimens strengthened by the former, cement-based mortar performs better than epoxy.

关键词： fiber-reinforced cementitious matrix     flexural strengthening     shear strengthening     carbon fiber-reinforced polymer     shear span    

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effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious

Souzana P. TASTANI,Maria S. KONSTA-GDOUTOS,Stavroula J. PANTAZOPOULOU,Victor BALOPOULOS

《结构与土木工程前沿（英文）》 2016年 第10卷 第2期   页码 214-223 doi: 10.1007/s11709-016-0332-3

摘要： Stress transfer between reinforcing bars and concrete is engaged through rib translation relative to concrete, and comprises longitudinal bond stresses and radial pressure. The radial pressure is equilibrated by hoop tension undertaken by the concrete cover. Owing to concrete’s poor tensile properties in terms of strength and deformability, the equilibrium is instantly released upon radial cracking of the cover along the anchorage with commensurate abrupt loss of the bond strength. Any improvement of the matrix tensile properties is expected to favorably affect bond in terms of strength, resilience to pullout slip, residual resistance and controlled slippage.The aim of this paper is to investigate the local bond of steel bars developed in adverse tensile stress conditions in the concrete cover. In the tests, the matrix comprises a novel, strain resilient cementitious composite (SRCC) reinforced with polypropylene fibers (PP) with the synergistic action of carbon nano-tubes (CNT). Local bond is developed over a short anchorage length occurring in the constant moment region of a four-point bending short beam. Parameters of investigation were the material structure (comprising a basic control mix, reinforced with CNTs and/or PP fibers) and the age of testing. Accompanying tests used to characterize the cementitious material were also conducted. The test results illustrate that all the benefits gained due to the synergy between PP fibers and CNTs in the matrix, namely the maintenance of the multi-cracking effect with time, the increased strength and deformability as well as the highly increased material toughness, were imparted in the recorded bond response. The local bond response curves thus obtained were marked by a resilient appearance exhibiting sustained strength up to large levels of controlled bar-slip; the elasto-plastic bond response envelope was a result of the confining synergistic effect of CNTs and the PP fibers, and it occurred even without bar yielding.

关键词： carbon nanotubes     strain resilient cementitious composite     polypropylene fibers     tensile bending     bond    

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Quantification of hydration products in cementitious materials incorporating silica nanoparticles

L. P. SINGH,A. GOEL,S. K. BHATTACHARYYA,G. MISHRA

《结构与土木工程前沿（英文）》 2016年 第10卷 第2期   页码 162-167 doi: 10.1007/s11709-015-0315-9

摘要： In the present work, silica nanoparticles (30-70nm) were supplemented into cement paste to study their influence on degree of hydration, porosity and formation of different type of calcium-silicate-hydrate (C-S-H) gel. As the hydration time proceeds, the degree of hydration reach to 76% in nano-modified cement paste whereas plain cement achieve up to 63% at 28 days. An influence of degree of hydration on the porosity was also determined. In plain cement paste, the capillary porosity at 1hr is ~48%, whereas in silica nanoparticles added cement is ~35 % only, it revealed that silica nanoparticles refines the pore structure due to accelerated hydration mechanism leading to denser microstructure. Similarly, increasing gel porosity reveals the formation of more C-S-H gel. Furthermore, C-S-H gel of different Ca/Si ratio in hydrated cement paste was quantified using X-ray diffractometer and thermogravimetry. The results show that in presence of silica nanoparticles, ~24% C-S-H (Ca/Si<1.0) forms, leading to the formation of polymerised and compact C-S-H. In case of plain cement this type of C-S-H was completely absent at 28 days. These studies reveal that the hydration mechanism of the cement can be tuned with the incorporation of silica nanoparticles and thus, producing more durable cementitious materials.

关键词： degree of hydration     porosity     calcium-silicate-hydrate (C-S-H)     silica nanoparticles    

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Pore structure of cementitious material enhanced by graphitic nanomaterial: a critical review

S.A. GHAHARI, E. GHAFARI, L. ASSI

《结构与土木工程前沿（英文）》 2018年 第12卷 第1期   页码 137-147 doi: 10.1007/s11709-017-0431-9

摘要： Carbon nano tubes (CNT) has been introduced as an efficient nanomaterial in order to improve the mechanical and durability properties of concrete. The effect of CNT on the microstructures of cementitious materials has been widely reported. This paper combines a critical review on the effect of CNT on the pore and microstructure of cement composite with a discussion on the porosity measurement of pastes containing CNT using mercury intrusion porosimetry techniques (MIP). It was found that, surface treatment by H SO and HNO solution forms carboxyl acid groups on CNTs’ surfaces that lead to the improvement of reinforcement. In this scope, this review paper involves analyzing the effect of CNT on the microstructure and the pore structure of cementitious materials. The existing methods of measuring the porosity of cementitious material are reviewed, in particular, the contact angle measurement is discussed in detail in which the most effective parameters and possible errors of calculation is presented.

关键词： carbon nano tubes     microstructure     porosity     mercury intrusion porosimetry     cement composite    

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nano/microparticles for enhanced mechanical properties and electromagnetic interference shielding of cementitious

Rao Arsalan KHUSHNOOD,Sajjad AHMAD,Luciana RESTUCCIA,Consuelo SPOTO,Pravin JAGDALE,Jean-Marc TULLIANI,Giuseppe Andrea FERRO

《结构与土木工程前沿（英文）》 2016年 第10卷 第2期   页码 209-213 doi: 10.1007/s11709-016-0330-5

摘要： In the present work, carbon nano/microparticles obtained by controlled pyrolysis of peanut (PS) and hazelnut (HS) shells are presented. These materials were characterized by Raman spectroscopy and field emission-scanning electron microscopy (FE-SEM). When added to cement paste, up to 1 wt%, these materials led to an increase of the cement matrix flexural strength and of toughness. Moreover, with respect to plain cement, the total increase in electromagnetic radiation shielding effect when adding 0.5 wt% of PS or HS in cement composites is much higher in comparison to the ones reported in the literature for CNTs used in the same content.

关键词： carbon nano/microparticles     green cement     toughness mechanism     electromagnetic shielding effect    

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side chain length of polycarboxylate-ether-based high-range water-reducing admixture on properties of cementitious

Süleyman ÖZEN, Muhammet Gökhan ALTUN, Ali MARDANI-AGHABAGLOU, Kambiz RAMYAR

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1573-1582 doi: 10.1007/s11709-020-0680-x

摘要： Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures, most previous reports on the cement-admixture compatibility did not provide sufficient information on the structure of the admixture. Hence, the evaluation and generalization of the reports on the cement-admixture compatibility are challenging. In this study, three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content, anionic/nonionic molar ratio, and main chain length and different side chain lengths were produced. The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated. In addition, an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type, admixture/cement ratio, and elapsing time to the Marsh funnel flow time, mini-slump, slump flow, and compressive strength. The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems. However, the admixture having the shortest side chain was better with regard to flow retention. The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures. Regarding the behaviors of the admixtures in the cementitious systems, an optimal admixture side chain molecular weight is proposed.

关键词： water-reducing admixture     side chain length     cement paste     fluidity     compressive strength    

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大掺量矿物掺合料高性能混凝土在京沪高铁四标段中的应用

高治双,赵年全,赵常煜,胡明文,苟云龙

《中国工程科学》 2009年 第11卷 第1期   页码 26-31

摘要：

以京沪高速铁路为工程背景，试验研究了矿物掺合料（粉煤灰、粉煤灰-矿粉）对混凝土工作性能、力学性能和耐久性能的影响以及大掺量矿物掺合料高性能混凝土的配制技术。结合实际工程，介绍了大掺量矿物掺合料高性能混凝土原材料选择、配合比设计、施工工艺等方面的控制技术。

关键词： 矿物掺合料     大掺量矿物掺合料高性能混凝土     配制与施工     质量控制    

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Performance of soft-hard-soft (SHS) cement based composite subjected to blast loading with consideration of interface properties

Jun WU,Xuemei LIU

《结构与土木工程前沿（英文）》 2015年 第9卷 第3期   页码 323-340 doi: 10.1007/s11709-015-0301-2

摘要： This paper presents a combined experimental and numerical study on the damage and performance of a soft-hard-soft (SHS) multi-layer cement based composite subjected to blast loading which can be used for protective structures and infrastructures to resist extreme loadings, and the composite consists of three layers of construction materials including asphalt concrete (AC) on the top, high strength concrete (HSC) in the middle, and engineered cementitious composites (ECC) at the bottom. To better characterize the material properties under dynamic loading, interface properties of the composite were investigated through direct shear test and also used to validate the interface model. Strain rate effects of the asphalt concrete were also studied and both compressive and tensile dynamic increase factor (DIF) curves were improved based on split Hopkinson pressure bar (SHPB) test. A full-scale field blast test investigated the blast behavior of the composite materials. The numerical model was established by taking into account the strain rate effect of all concrete materials. Furthermore, the interface properties were also considered into the model. The numerical simulation using nonlinear finite element software LS-DYNA agrees closely with the experimental data. Both the numerical and field blast test indicated that the SHS composite exhibited high resistance against blast loading.

关键词： high strength concrete (SHS)     engineered cementitious composite     interface     blast test     strain rate effect    

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An investigation into the properties of ternary and binary cement pastes containing glass powder

Marcelo Frota BAZHUNI, Mahsa KAMALI, Ali GHAHREMANINEZHAD

《结构与土木工程前沿（英文）》 2019年 第13卷 第3期   页码 741-750 doi: 10.1007/s11709-018-0511-5

摘要： The properties of binary and ternary cement pastes containing glass powder (GP) were examined. Hydration at early age was evaluated using semi-adiabatic calorimetry and at late ages using non-evaporable water content and thermogravimetric analysis. The transport characteristic was assessed by measuring electrical resistivity. The binary paste with slag showed the highest hydration activity compared to the binary pastes with GP and fly ash (FA). The results indicated that the pozzolanic behavior of the binary paste with GP was less than that of the binary pastes with slag or FA at late ages. An increase in the electrical resistivity and compressive strength of the binary paste with GP compared to other modified pastes at late ages was observed. It was shown that GP tends to increase the drying shrinkage of the pastes. Ternary pastes containing GP did not exhibit synergistic enhancements compared to the respective binary pastes.

关键词： cement paste     glass powder     pozzolanic reaction     supplementary cementitious material    

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Computational studies on the seismic response of the State Route 99 bridge in Seattle with SMA/ECC plastic hinges

Jiping GE, M. Saiid SAIIDI, Sebastian VARELA

《结构与土木工程前沿（英文）》 2019年 第13卷 第1期   页码 149-164 doi: 10.1007/s11709-018-0482-6

摘要： This paper reports a computational study on the seismic response of a three-span highway bridge system incorporating conventional and novel substructure details for improved seismic performance. The bridge has three continuous spans supported by two single-column piers and integral abutments founded on drilled shafts. It will be the first full-scale highway bridge to use superelastic shape memory alloy bars (SMA) and engineered cementitious composite (ECC) to mitigate column plastic hinge damage and minimize residual displacements after a strong earthquake. A three-dimensional computational model capturing the nonlinear constitutive response of the novel materials and the effects of dynamic soil-structure interaction was developed to assess the seismic response of the bridge in finite-element software OpenSees. Two versions of the same bridge were analyzed and compared, one with conventional cast-in-place reinforced concrete columns, and the other with top plastic hinges incorporating Nickel-Titanium (NiTi) SMA reinforcing bars and ECC. The novel SMA/ECC plastic hinges were found to substantially reduce damage and post-earthquake residual displacements in the bridge substructure, but led to larger maximum drifts relative to the bridge with conventional reinforced concrete plastic hinges. The analysis results suggested that the novel plastic hinges could lead to improved post-earthquake serviceability of bridges after intense earthquakes.

关键词： seismic design     analytical simulation     near-fault earthquakes     shape memory alloy     engineered cementitious composite     self-centering    

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Experimental study on flexural behavior of ECC/RC composite beams with U-shaped ECC permanent formwork

Zhi QIAO, Zuanfeng PAN, Weichen XUE, Shaoping MENG

《结构与土木工程前沿（英文）》 2019年 第13卷 第5期   页码 1271-1287 doi: 10.1007/s11709-019-0556-0

摘要： To enhance the durability of a reinforced concrete structure, engineered cementitious composite (ECC), which exhibits high tensile ductility and good crack control ability, is considered a promising alternative to conventional concrete. However, broad application of ECC is hindered by its high cost. This paper presents a new means to address this issue by introducing a composite beam with a U-shaped ECC permanent formwork and infill concrete. The flexural performance of the ECC/RC composite beam has been investigated experimentally with eight specimens. According to the test results, the failure of a composite beam with a U-shaped ECC formwork is initiated by the crushing of compressive concrete rather than debonding, even if the surface between the ECC and the concrete is smooth as-finished. Under the same reinforcement configurations, ECC/RC composite beams exhibit increases in flexural performance in terms of ductility, load-carrying capacity, and damage tolerance compared with the counterpart ordinary RC beam. Furthermore, a theoretical model based on the strip method is proposed to predict the moment-curvature responses of ECC/RC composite beams, and a simplified method based on the equivalent rectangular stress distribution approach has also evolved. The theoretical results are found to be in good agreement with the test data.

关键词： engineered cementitious composite (ECC)     durability     ECC/RC composite beam     permanent formwork     flexural performance     theoretical method    

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System reliability and system resilience

《工程管理前沿（英文）》 2021年 第8卷 第4期   页码 615-619 doi: 10.1007/s42524-021-0176-y

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标题 作者 时间 类型 操作

reducing admixtures having different action mechanisms on mechanical and durability performance of cementitious

期刊论文

Strengthening of the concrete face slabs of dams using sprayable strain-hardening fiber-reinforced cementitious

期刊论文

Effect of natural pozzolan content on the properties of engineered cementitious composites as repair

Said CHOUCHA, Amar BENYAHIA, Mohamed GHRICI, Mohamed Said MANSOUR

期刊论文

Strengthening of reinforced concrete beams using fiber-reinforced cementitious matrix systems fabricated

期刊论文

effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious

Souzana P. TASTANI,Maria S. KONSTA-GDOUTOS,Stavroula J. PANTAZOPOULOU,Victor BALOPOULOS

期刊论文

Quantification of hydration products in cementitious materials incorporating silica nanoparticles

L. P. SINGH,A. GOEL,S. K. BHATTACHARYYA,G. MISHRA

期刊论文

Pore structure of cementitious material enhanced by graphitic nanomaterial: a critical review

S.A. GHAHARI, E. GHAFARI, L. ASSI

期刊论文

nano/microparticles for enhanced mechanical properties and electromagnetic interference shielding of cementitious

Rao Arsalan KHUSHNOOD,Sajjad AHMAD,Luciana RESTUCCIA,Consuelo SPOTO,Pravin JAGDALE,Jean-Marc TULLIANI,Giuseppe Andrea FERRO

期刊论文

side chain length of polycarboxylate-ether-based high-range water-reducing admixture on properties of cementitious

Süleyman ÖZEN, Muhammet Gökhan ALTUN, Ali MARDANI-AGHABAGLOU, Kambiz RAMYAR

期刊论文

大掺量矿物掺合料高性能混凝土在京沪高铁四标段中的应用

高治双,赵年全,赵常煜,胡明文,苟云龙

期刊论文

Performance of soft-hard-soft (SHS) cement based composite subjected to blast loading with consideration of interface properties

Jun WU,Xuemei LIU

期刊论文

An investigation into the properties of ternary and binary cement pastes containing glass powder

Marcelo Frota BAZHUNI, Mahsa KAMALI, Ali GHAHREMANINEZHAD

期刊论文

Computational studies on the seismic response of the State Route 99 bridge in Seattle with SMA/ECC plastic hinges

Jiping GE, M. Saiid SAIIDI, Sebastian VARELA

期刊论文

Experimental study on flexural behavior of ECC/RC composite beams with U-shaped ECC permanent formwork

Zhi QIAO, Zuanfeng PAN, Weichen XUE, Shaoping MENG

期刊论文

System reliability and system resilience

期刊论文