Journal of Materials and Engineering Structures
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Behaviour of ground cupola furnace slag blended concrete at elevated temperature
Get PDFFires adversely affect the performance of concrete when expose to extreme temperatures. However, it is important to study the effects of elevated temperature on the concrete properties. Concrete often contains other cementitious materials such as ground granulated blast furnace slag (GGBFS) and this has been successfully used to improve its properties. Hence, little or no study has been carried out on the use of ground cupola furnace slag (GCFS) in concreting. Therefore, this paper investigates the behavior of concrete blended with GCFS at elevated temperatures. A total of 300 samples were prepared with four different GCFS contents. The test specimens were cured for 28-d and 56-d and subjected to elevated temperatures ranging from 200oC to 800oC up to 24 h. The slump, residual compressive and tensile strength tests were carried out on fresh and hardened concrete. The results showed that the compressive strength and splitting tensile strengths of concrete generally increased with increasing % GCFS content but decreased as temperature increases. At 28-d and 56-d, the strengths were observed to be maximum at 10% replacement when the temperature is 200oC compared to other mixes. It can be concluded that the strength drastically decreased at temperature above 200oC. An analysis of variance (ANOVA) was also carried out to determine the effect of the elevated temperature and percentage replacement of cement with GCFS on the 28-d and 56-d compressive strength of concrete. The results showed that temperature and % GCFS content had a statistically significant effect on the concrete performance. Based on Tukey’s honestly significant difference (HSD), the effect of GCFS was found to be statistically non-significant for 4% and 6% GCFS content at 28-d; and 2% and 4% GCFS content at 56-d. The effect of temperature was also found to be statistically non-significant for 600oC and 800oC at 28-d; and 27oC and 600oC; 200oC and 400oC at 56-d
Comparison of Compressive Strength and Flexural Capacity between Engineered Cementitious Composites (Bendable Concrete) and Conventional Concrete used in Bangladesh
Get PDFThe Engineered Cementitious Composites (ECC) is made of the same ingredients as in regular concrete. The coarse aggregate is replaced with tiny Polyvinyl Alcohol fibres. This structure offers maximum flexibility and it is expected to cost less. It looks exactly like normal concrete, but under excessive strain, the ECC concrete allows, the specially coated network of fibre in the cement to slide within the cement, thus avoiding the inflexibility that causes brittleness and breakage. As this is a special type of concrete there are no defined codes for it, thus for these reasons, the parameters needed are to be obtained using trial and error method. During the composite preparation, sieve analysis was carried out. Composites were reinforced with Polyvinyl Alcohol (PVA) at the following ratios: 0 % (control), 0.5 %, 1 % and 1.5 %. The cylindrical specimens were subjected to compression and the slab specimens were subjected to flexural test using a Universal Testing Machine, while acquiring data with GOM Correlation Software. Test results reveal that fibre ratio 1% is most acceptable for attaining best compressive strength along with high flexural value. Even though 1% fibre content concrete in the flexural strength test showed 33% less strength of what 1.5% fibre content concrete gained, in the long run, for having the highest compressive strength value (almost 62% more than of 0% fibre content concrete and 15% more than of 1.5% fibre content concrete), 1% fibre content concrete is most suited for constructions
From quality control to decision-making on the management of bridges and structures: What’s next?
Get PDFThe process of managing a stock of existing bridges and structures is extremely complex and challenging. At the same time, it is considered as one of the most relevant and important fields for civil engineers, involving academics, researchers, consultants, contractors, and owners. Indeed, in the recent years, several national and international RD funded projects raised this topic, and many international associations, such as EuroStruct, IABSE fib, started commissions and task groups on this field. This work consists on an overview of the most recent matters on this field, covering the whole cycle, from the quality control, addressing extreme events, to the decision making process. Also, it will be given a focus on the recent developments on the assessment and forecasting the performance of bridge and other structures. Finally, an overview will be made for different types of structures, specifically those related to transport infrastructures
Limitations of cyclic pile load tests by kentledge system in soft clay soil
Get PDFThe paper describes the inadequacies of cycled head-down load tests on two barrettes and one bored pile installed in soft clay soil region in Binh Thanh district, and district 7, Ho Chi Minh City, Vietnam, respectively. The soil profile of these sites consisted of layers of organic soft clay and silt from 22.5 m to 28.6 m depth on compact silty sand or semi-stiff to stiff clays to about 60 m depth and followed by dense to very dense sand. The cross-section area of two barrettes located on the Tan Cang complex area was 2,800 mm by 800 mm, which were constructed using the bucket drill technique with bentonite slurry into 65 m depth. The bored pile of the Lakeside project in district 7 having a pile diameter was 1200 mm and 80 m depth. All instrumented piles were attached from ten to eleven strain gages levels along the pile shaft to record the deformation data during the load tests. The strain data analysis shows that the shaft frictions of pile portions located in the soft clay soil regions were increased dramatically, and the base resistances were smaller expected by the setting-up of Kentledge and the cyclic loading tests
Numerical analysis of pipe jacking in deep soft soil based on the construction of urban underground sewage pipeline
Get PDFPipe jacking construction in complex soil layers and soil conditions remains to be a tough issue, because various factors are supposed to be considered and the jacking parameters needs optimization. The purpose of this paper is to analyze the impact of pipe jacking on surface settlement, soil deformation and pipe-soil interaction in a numerical model of pipe jacking through deep soft soil, which is a simulated construction of urban underground sewage pipeline. The results show that the pipe jacking construction adopted in the deep soft soil layer has little effect on the surrounding soil layers. And the maximum ground settlement is only about 8 mm. The impact of pipe jacking construction in deep soft soil layer on ground settlement is about 6 times the diameter of the jacking pipe along the pipe axis. Finally, the input force needs to be selected according to the condition of the soil layer to ensure the safety of the pipe jacking construction
Examination of influential factors on shear strength of externally bonded FRP reinforcement in RC beams
Get PDFThe fiber-reinforced polymer (FRP) retrofitting technique has been increasingly created to enhance the capacity of the existing concrete members. In this study, the shear contribution of the external FRP strengthening system in the reinforced concrete (RC) beams is estimated by the semi-empirical models available in the open literatures and guidelines. Number of beams monitored in the previous studies are first considered to assess the reliability of the models. Afterwards, the investigation of influential factors such as the beam configurations, the strengthening characteristics and the material properties are implemented. With high accuracy and low coefficient of variation, the model proposed in a previous study of the authors gains the mostly considerable estimation for the shear resisting strength of FRP strengthening system compared to the accessible data base from the experiments. In addition, the critical properties of the materials associating with the retrofitting systems for the strengthened beams are investigated to obtain the acquired shear performance
The rheological properties of modified self-compacting cementitious paste
Get PDFThe development of self-compacting concrete (SCC) marks a huge step towards improved efficiency and working conditions on construction sites and in the precast industry. SCC flows easily into more complex shapes and through reinforcement bars, reduces the manpower required for the placement; no vibration is required to ensure correct compaction of concrete. This concrete contains a high volume of binder, which is controlled by their rheological behaviour. The paste consists of binders (Portland cement with or without supplementary cementitious materials), water, chemical admixtures and fillers. In this study, two series of tests were performed on self-compacting cement pastes made with marble waste additions as mineral addition. The first series of this investigation was to determine the flow time of paste using Marsh cone, the second series was to determine the rheological parameters of the same paste namely yield stress and plastic viscosity using rheometer. The results of this investigation allowed us to study the evolution of the yield stress, viscosity and the flow time Marsh cone paste as a function of the composition of the paste.Self-compacting concrete (SCC) development marks an important step towards efficiency and conditions working in construction sites and in the precast industry. SCC easily flows into more complex shapes and through reinforcing bars, reduces the labor required for placement; no vibration is required to ensure proper concrete compaction. This concrete contains a high binder volume, which is controlled by their rheological behavior. The paste binders consists Portland cement (with or without additional cementations’ materials), water, chemical additives and fillers. In this study, two tests series were carried out on self-compacting cement pastes made with marble waste additions as addition minerals. The first series of this survey was to determine the flow dough time of using a Marsh cone, the second series was to determine the same dough rheological parameters, namely the elastic limit and the plastic viscosity at using a rheometer. The results of this survey allowed us to study of the elastic limit evolution, the viscosity and the marsh flow time cone paste as a paste composition function
The effect of displacement speed of rigid retaining walls on failure of analogical material by active earth pressure
Get PDFLe présent article s’intéresse au domaine de modélisation physique du phénomène de poussée des terres et de la cinétique de rupture rencontrée dans les milieux granulaires. Mieux comprendre le phénomène de poussée et les mécanismes de rupture derrière les ouvrages de soutènement contribuera à mieux les concevoir et permettra de rendre les sinistres moins dommageables. L’exploitation d’un modèle réduit rempli avec un matériau bidimensionnel de Schneebeli léger a permis la réalisation des essais de poussée en déplaçant la paroi mobile du dispositif vers l’extérieur du massif. L’évolution des bandes de cisaillement a mis en avant les localisations des déformations. Les résultats ont montré que la vitesse de déplacement du mur influe sur le mécanisme de rupture et qu’elle est proportionnelle à la perturbation du milieu granulaire. En perspective, il serait judicieux d’explorer la rupture sur sol réel conforté par des matériaux recyclés.Cet article s’intéresse au domaine de modélisation physique du phénomène de poussée des terres et de la cinétique de rupture rencontrée dans les milieux granulaires. Mieux comprendre le phénomène de poussée et les mécanismes de rupture derrière les ouvrages de soutènement contribuera à mieux les concevoir et permettra de rendre les sinistres moins dommageables. L’exploitation d’un modèle réduit rempli avec un matériau bidimensionnel de Schneebeli léger a permis la réalisation des essais de poussée en déplaçant la paroi mobile du dispositif vers l’extérieur du massif. L’évolution des bandes de cisaillement a mis en avant les localisations des déformations. Les résultats ont montré que la vitesse de déplacement du mur influe sur le mécanisme de rupture et qu’elle est proportionnelle à la perturbation du milieu granulaire. En perspective, il serait judicieux d’explorer la rupture sur sol réel conforté par des matériaux recyclés.This paper illustrated the physical modeling of the phenomenon of Active Earth Pressure and kinetics of rupture in the granular soils. Better, understand the phenomenon of Active Earth Pressure and mechanisms of failure behind the retaining walls will contribute to better conceiving them and will make claims less damaging. The exploitation of a small-scale model filled with Schneebeli material;light two-dimensional material simulating granular non-cohesive soil, allowed tests realization of Active Earth Pressure by moving the mobile wall of the device towards the outside of two-dimensional material. The evolution of the shear bands has highlighted the locations of the deformations. The results showed that the wall's speed of movement influences the failure mechanism and is proportional to the disturbance of the granular soil. In perspective, it would be judicious to explore the failure on real soil reinforced by recycled materials.
Investigation on cyclic behaviour of FRC beams incorporating copper slag as sustainable waste
Get PDFScarcity of the natural sand and large availability of industrial wastes give the way to utilise the industrial by-product in concrete production. This paper showcases the performance of concrete composite containing copper slag and polypropylene fibre under cyclic loading. Fibrillated polypropylene fibre of 0% (P0), 0.2% (P1), 0.4% (P2) 0.6% (P3) volume fractions and 40% copper slag (C40) are used together. The experimental work was conducted on the reinforced concrete beams of size 100mm x 200mm x 900mm. The criteria considered for discussion are yield power, yield deflection, ultimate strength, ultimate deflection, ductility factors and energy dissipation. It is observed that when subjected to monotonic loading and cyclic loading respectively, the overall load carrying power of C40P2 beam is 5 per cent and 2.71 per cent higher than the reference section. The specimen C40P2 has a ductility factor 25.05 per cent higher than the control beam. Energy absorption capacity of C40P2 is 72.79% more than the normal concrete. It is therefore concluded that, under cyclic loading, the output of 40% copper slag with 0.4% of polypropylene fibres find superior than control concrete
Enhancement of moment resistance of steel beams with initial imperfections and residual stresses by using stiffeners and GFRP plates
Get PDFThe present study proposes three strengthening solutions for wide flange steel beams having residual stresses and initial imperfections. In Solution 1, a midspan web stiffener is applied to such beams, aiming at reducing local web buckling. In Solution 2, two GFRP plates are bonded to the beam flanges in order to reduce local flange buckling. Solution 3 is a combination of the Solutions 1 and 2. Moment resistances of the strengthening systems are numerically evaluated and compared against those of the corresponding bare beam. Key observations obtained include (i) All Solutions 1, 2 and 3 are effective in increasing the moment resistance of the beam structure, (ii) When initial imperfection and residual stresses are excluded, the failure mode of the bare beams is mostly governed by local flange buckling. The moment resistances of the steel beam in Solution 1 are approximately equal to a fully plastic section moment. Meanwhile, the moment resistances of Solutions 2 and 3 are based on GFRP rupture failure mode. The strengthening solutions by using GFRP plates are the most effective while the addition of a web stiffener only plays a minor role, (iii) When initial imperfection and residual stresses are included, the failure mode of the steel beams is governed by local web buckling. The web stiffener in Solutions 1 and 3 plays an important role to increase the beam moment resistances. And (iv) For long spans, the moment resistances of Solutions 2 and 3 are significantly higher than those of Solution 1