scholarly journals Structural Performance And Self-Healing Behaviour Of Engineered Cementitious Composites Subjected To Fatigue Loading

2021 ◽  
Author(s):  
Shirin Ahmad

This research investigates the effect of fatigue loading on the flexural performance and self-healing behaviour of beams and link slabs made of Engineered Cementitious Composites (ECC). The influences of fly ash content, types/size of sand, MgO agent, fatigue stress level/cycle and age are analyzed based on strength/deflection capacity recovery and residual strength/deflection/energy absorbing capacity. The deflection evolution rate and energy absorption capacity were much higher in ECC link slabs compared to their SCC counterparts. Higher energy absorption and deflection evolution rate were observed in mortar sand based ECC specimens during fatigue loading. ECC link slabs with mortar sand having 55% fly ash content have shown the best self-healing and fatigue performance attaining high residual strength, deflection and energy absorbing capacity of up to 98.3%, 95.4% and 97.1% of control specimens, respectively besides retaining multi-cracking characteristics. This research demonstrates viability of using ECC link slab for construction of joint-free bridges.

2021 ◽  
Author(s):  
Shirin Ahmad

This research investigates the effect of fatigue loading on the flexural performance and self-healing behaviour of beams and link slabs made of Engineered Cementitious Composites (ECC). The influences of fly ash content, types/size of sand, MgO agent, fatigue stress level/cycle and age are analyzed based on strength/deflection capacity recovery and residual strength/deflection/energy absorbing capacity. The deflection evolution rate and energy absorption capacity were much higher in ECC link slabs compared to their SCC counterparts. Higher energy absorption and deflection evolution rate were observed in mortar sand based ECC specimens during fatigue loading. ECC link slabs with mortar sand having 55% fly ash content have shown the best self-healing and fatigue performance attaining high residual strength, deflection and energy absorbing capacity of up to 98.3%, 95.4% and 97.1% of control specimens, respectively besides retaining multi-cracking characteristics. This research demonstrates viability of using ECC link slab for construction of joint-free bridges.


2021 ◽  
Author(s):  
Mohamed A. A. Sherir

This thesis investigates the influence of microsilica sand and local crushed sand, and different supplementary cementing materials on the mechanical properties of engineered cementitious composites (ECCs). ECC is a special type of high performance fiber reinforced cementitious composite with high ductility which exhibits strain-hardening and multiple-cracking behaviours in tension. The use of local aggregates in ECC production can lower its cost to mitigate the obstacles of wider commercial use. The experimental results showed that multiple-cracking behaviour was developed under fatigue loading for fly ash ECC (FA-ECC) mixtures, and the number of cracks was lower at both lower fatigue stress level and higher fatigue number of cycles. FA-ECC mixtures with silica sand exhibited higher deflection evolution under fatigue loading than FA-ECC mixtures with crushed sand. Based on the experimental results on link slab specimens, both FA-ECC mixtures with silica and crushed sands exhibited almost the same creep behaviour.


Author(s):  
Hassan Noorvand ◽  
Gabriel Arce ◽  
Marwa Hassan ◽  
Tyson Rupnow ◽  
Louay N. Mohammad

Engineered cementitious composites (ECCs) are a type of micromechanically-designed cementitious composite reinforced with a moderate volume fraction of short fiber, typically 2% by volume. ECCs form steady-state multiple cracking that considerably improves the tensile strength and ductility of traditional concrete. In this study, the properties of matrix and the interface of ECCs were tailored through the use of crumb rubber, different types of sand, and different replacement levels of cement with fly ash. The study examined the effect of sand replacement with crumb rubber (20% by volume), two types of river sands (coarse and fine), increasing the content of class F fly ash (up to 75% cement replacement), and low fiber content (1.75%) on the mechanical properties of ECCs. Compressive strength, uniaxial tensile, and third-point bending tests were performed to characterize the properties of ECC mixes. Experimental results demonstrated that increasing fly ash content and using crumb rubber favored ductility of the composites. However, higher fly ash contents and a low water-to-binder (W/B) ratio produced lower strengths as these limited the pozzolanic reaction of fly ash making it act partially as a filler. While incorporation of crumb rubber showed adverse effects on the tensile strength of ECC materials (up to 26% decrease), the tensile ductility of ECC materials improved significantly (up to 434% improvement). Moreover, the implementation of different types of sand produced minor effects on the mechanical properties of ECCs. Overall, a tradeoff between the strength and ductility of the composites was detected, which highlights the implications of matrix/interface tailoring in the overall performance of ECC.


2021 ◽  
Author(s):  
Mohamed A. A. Sherir

This thesis investigates the influence of microsilica sand and local crushed sand, and different supplementary cementing materials on the mechanical properties of engineered cementitious composites (ECCs). ECC is a special type of high performance fiber reinforced cementitious composite with high ductility which exhibits strain-hardening and multiple-cracking behaviours in tension. The use of local aggregates in ECC production can lower its cost to mitigate the obstacles of wider commercial use. The experimental results showed that multiple-cracking behaviour was developed under fatigue loading for fly ash ECC (FA-ECC) mixtures, and the number of cracks was lower at both lower fatigue stress level and higher fatigue number of cycles. FA-ECC mixtures with silica sand exhibited higher deflection evolution under fatigue loading than FA-ECC mixtures with crushed sand. Based on the experimental results on link slab specimens, both FA-ECC mixtures with silica and crushed sands exhibited almost the same creep behaviour.


2021 ◽  
Author(s):  
Mohamed A. A. Sherir ◽  
Khandaker M. A. Hossain ◽  
Mohamed Lachemi

This paper presents the influence of silica sand, local crushed sand and different supplementary cementing materials (SCMs) to Portland cement (C) ratio (SCM/C) on the flexural fatigue performance of engineered cementitious composites (ECCs). ECC is a micromechanically-based designed high-performance polymer fiber reinforced concrete with high ductility which exhibits strain-hardening and micro-cracking behavior in tension and flexure. The relative high cost remains an obstacle for wider commercial use of ECC. The replacement of cement by SCMs, and the use of local sand aggregates can lower cost and enhance greenness of the ECC. The main variables of this study were: type and size of aggregates (local crushed or standard silica sand), type of SCMs (fly ash “FA” or slag), SCM/cement ratio of 1.2 or 2.2, three fatigue stress levels and number of fatigue cycles up to 1 million. The study showed that ECC mixtures produced with crushed sand (with high volume of fly ash and slag) exhibited strain hardening behavior (under static loading) with deformation capacities comparable with those made with silica sand. Class F-fly ash combined with crushed sand was the best choice (compared to class CI fly ash and slag) in order to enhance the ECC ductility with slag–ECC mixtures producing lowest deflection capacity. FA–ECC mixtures with silica sand developed more damage under fatigue loading due to higher deflection evolution than FA–ECC mixtures with crushed sand.


2021 ◽  
Author(s):  
Mohamed A. A. Sherir ◽  
Khandaker M. A. Hossain ◽  
Mohamed Lachemi

This paper presents the influence of silica sand, local crushed sand and different supplementary cementing materials (SCMs) to Portland cement (C) ratio (SCM/C) on the flexural fatigue performance of engineered cementitious composites (ECCs). ECC is a micromechanically-based designed high-performance polymer fiber reinforced concrete with high ductility which exhibits strain-hardening and micro-cracking behavior in tension and flexure. The relative high cost remains an obstacle for wider commercial use of ECC. The replacement of cement by SCMs, and the use of local sand aggregates can lower cost and enhance greenness of the ECC. The main variables of this study were: type and size of aggregates (local crushed or standard silica sand), type of SCMs (fly ash “FA” or slag), SCM/cement ratio of 1.2 or 2.2, three fatigue stress levels and number of fatigue cycles up to 1 million. The study showed that ECC mixtures produced with crushed sand (with high volume of fly ash and slag) exhibited strain hardening behavior (under static loading) with deformation capacities comparable with those made with silica sand. Class F-fly ash combined with crushed sand was the best choice (compared to class CI fly ash and slag) in order to enhance the ECC ductility with slag–ECC mixtures producing lowest deflection capacity. FA–ECC mixtures with silica sand developed more damage under fatigue loading due to higher deflection evolution than FA–ECC mixtures with crushed sand.


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