Plain Cement Concrete Research Articles

Strength and Durability of Kenaf Fiber Reinforced Concrete for Marine Structures

Nowadays, Kenaf fiber is sustainably useful in marine structures and has become one of the materials that may be high in demand as it is light, biodegradable and environmental friendly. This study investigates the effect of fiber percentage on compressive strength of fiber reinforced concrete (FRC) and the relationship between compressive strength and time of FRC immersion in seawater. FRC concrete cubes were prepared using four different percentage of fiber (0%, 1.5%, 3.0% and 4.5%). These FRC were immersed in seawater for 7, 14 and 21 days for three consecutive weeks. Based on the experiment, it was found that there was improvement in compressive strength of FRC when compared to plain cement concrete. The results showed that 3.0% of KF to cement matrix concrete determined the highest compressive strength of 205.43 Pa while 0% of KF fiber to cement concrete matrix (control specimen) showed the lowest compressive strength of 158.28 Pa. Also the addition of Kenaf fiber to cement concrete decreased the seawater absorption more than concrete with absolutely 0% of KF fiber to cement concrete (control specimen). In conclusion, the results did show significant improvement and a consistent trend on strength with the addition of FRC. This study also revealed that the percentage of water absorption was on the increase for 0, 7 and 14 days and become constant after day 21. This is due to manufacturing defects that occurred which block the water from entering the material and making the material absorb less water.

A three dimensional constitutive model for plain cement concrete

The validity of some of the assumptions made during systematic development of constitutive relation – homogeneity, isotropy, and non-dissipative response – is examined experimentally by testing plain concrete cylinders in the circumferential displacement controlled uniaxial compression tests. The tested cylinders indicate that the surface strains are not uniform and that the principal direction of the strain varies with the magnitude of the applied load. Hence, these cylinders are either deforming from a stressed state or anisotropic or both. The percentage dissipation computed as the area between the loading and unloading curves normalized using the area under the unloading curve is less than 10 percent up to 90 percent of the peak load. Therefore the mechanical response of concrete can be considered as non-dissipative. Assuming that the magnitude of the residual stresses present in the concrete panels would be small compared to the stresses arising due to the applied load, these residual stresses are ignored. Consequently, using the implicit constitutive theory framework for isotropic and compressible materials undergoing a non-dissipative process from a stress-free reference configuration, a three-dimensional constitutive relation for plain concrete is proposed. The material parameters in the proposed model are estimated from the uniaxial compression test and equal biaxial compression test. These parameters are expressed using initial Young’s modulus, initial Poisson’s ratio, maximum uniaxial compressive stress, the axial and transverse strain corresponding to the maximum uniaxial compressive stress, maximum equal biaxial compressive stress and the equal biaxial strain corresponding to maximum equal biaxial compressive stress. The ability of the proposed model to capture the response of various grade and type of concrete in ten biaxial experiments reported in the literature is examined. It is found that despite the limiting assumptions, the compression-compression, compression-tension and tension-tension stress strain response of the concrete in these ten experiments are adequately captured by the proposed model with mean R2 value of 0.94.

Study on the utilisation of quartzite as replacement for coarse aggregate in concrete

Concrete is most commonly and widely used material in infrastructure development. Coarse aggregate is major ingredient of concrete which constitutes to about 60 to 70% in terms of volume of concrete. The cost of coarse aggregate is increasing day by day due to its limited availability and large demand. In the present work, Quartzite is used as an alternate material for coarse aggregate in the concrete. Experimental studies were performed on plain cement concrete by replacing coarse aggregate with quartzite up to 100%. The mix design and test methods were in accordance with the Bureau of Indian Standards. Seven and 28 day strength tests were performed on concrete cubes. The optimum percentage of quartzite replacement to coarse aggregate is found at 20%. It is observed that compressive strength increased at 20% and 100% replacement was found to be 53.2 N/mm2 and 48.8 N/mm2.

Study on the utilisation of quartzite as replacement for coarse aggregate in concrete

Concrete is most commonly and widely used material in infrastructure development. Coarse aggregate is major ingredient of concrete which constitutes to about 60 to 70% in terms of volume of concrete. The cost of coarse aggregate is increasing day by day due to its limited availability and large demand. In the present work, Quartzite is used as an alternate material for coarse aggregate in the concrete. Experimental studies were performed on plain cement concrete by replacing coarse aggregate with quartzite up to 100%. The mix design and test methods were in accordance with the Bureau of Indian Standards. Seven and 28 day strength tests were performed on concrete cubes. The optimum percentage of quartzite replacement to coarse aggregate is found at 20%. It is observed that compressive strength increased at 20% and 100% replacement was found to be 53.2 N/mm2 and 48.8 N/mm2.

Fracture study of concrete composites with synthetic fibers additive under modes I and III using ENDB specimen

This paper investigates the mode I (i.e. tensile) and mode III (i.e. tearing) fracture behavior of concrete composites containing synthetic forta-ferro (SFF) fibers. By employing a simple and suitable test specimen called edge notched disc bend (ENDB) specimen, the effect of adding different percentages of SFF additive on fracture load, fracture toughness and work of fracture was studied experimentally under both pure mode I and pure mode III. A number of unique and useful experimental results were obtained in this research for crack growth resistance of plain and fiber reinforced composite concretes subjected to pure modes I and III loading conditions. It was observed that the fracture initiation and propagation stages are significantly affected by the SFF content. In comparison with the ordinary and plain cement concrete which is manufactured with no fiber additive, the SFF fiber reinforced concrete composite showed higher fracture toughness and work of fracture values. This demonstrates the improved performance of SFF fiber reinforced concretes against cracking under both tensile and tear loads. However, the fracture behavior of tested ENDB specimens made of concrete composites was dependent on the loading mode type (i.e. I or III) and also the SFF content. According to the experimental results the influence of SFF fibers on enhancing mode III fracture toughness was noticeably greater than the pure mode I case and for both loading modes the highest fracture toughness values (i.e. KIc and KIIIc) were obtained for those concrete composites containing 0.3% SFF. In addition, while the magnitude of KIc was greater than the corresponding value of KIIIc for all tested concrete composites, the fracture energy (or work of fracture) of mode III specimens were significantly higher than the mode I specimens. Indeed, the SFF fiber reinforced concrete composites exhibited excellent post peak failure response such that due to resistance of SFF fibers agains applied loads significant amount of energy was required for overall breakage of tested concretes. This ability can be considered as an advantage of SFF fiber reinforced concrete materials for designing earthquake-resistant structures.

Parametric study of sliding mode fracture in structural plain cement concrete for various sizes of beams

Fracture mechanics a part of solid mechanics deals with the crack initiation and propagation under certain loading conditions, as we know at ultimate load, the maximum shear stress is relatively larger than the shear strength in existence of compressive stress, which eventually results in shear failure. Under this criteria, failure is mode II which we can state that as the sliding mode. In this current research paper, an experimental investigation is carried out to study the behavior of plain cement concrete beams subjected to four point loading. Three different sizes of beams with Doubly Centered Notch (DCN) are used to examine the consequence of stress intensity factor and fracture energy with diversified notch depth ratios with a constant position of the notch from a center of the beam.

Experimental evaluation of bamboo reinforced concrete slab panels

Reinforced concrete structural members are primarily subjected to static gravity loads. The conventional steel reinforcement is used to provide additional tensile strength and energy absorption capacity to concrete members. But conventional M.S. (Mild steel) or HYSD (High Yielding Strength Deformed) bars are heavy in weight, costly, nonrenewable and un-ecofriendly material. Aiming to mitigate this concern a sustainable, renewable, ecofriendly material like bamboo has been used as substitute to steel in the present work. Bamboo-concrete Bond behaviour was first studied through a series of pull-out tests. Bond strength investigation has resulted in a unique bamboo strip profile along with a surface treatment the combination of which exhibited maximum bond strength under uniaxial loading. This new bamboo strip is further used as main reinforcement in concrete slab panels. Feasibility and effectiveness of this unique bamboo profile used as reinforcement was investigated through experimental testing of concrete slab panels. A total 15 concrete slab panels were fabricated and tested as per Eurocode EN-1448-5 (2006). The effect of total replacement of main steel reinforcement by bamboo on the flexural behaviour of slabs in terms of load-deformation characteristics, energy absorption capacity, crack patterns and failure modes have been studied. Test results show that there is improvement in the load carrying and deformation capacity when proposed bamboo strip is used as reinforcement in concrete slab panels as compared to that of PCC (Plain Cement Concrete) and RCC (Reinforced Cement Concrete) slabs. Interestingly the structural behaviour of slabs using newly developed bamboo reinforcement has shown significant improvement in flexural performance and it was marginally better than the RC slabs having M.S. bars as main reinforcement.

Effect of brick dust and lime powder on the performance of plain cement concrete

This paper illustrates the partial replacement of cement by brick dust and lime powder. The environmental condition is getting worse around the globe. One of the major causes of environment is waste generated from factories and working sites. The waste goes into dumping which not only occupy land but also cause ill effects to living. This unruly can be solved up to some degree by using these wastes in concrete as a cement replacement. An effort is made in this research to use lime powder and brick dust in plain concrete as cement replacement. The lime powder and brick dust was first used separately in concrete and then used a combination of brick dust and lime powder. Lime powder and brick dust was used separately in concrete up to 20% replacement with 5% interval. Than 5% brick dust was used with 15% lime powder, 10% brick dust with 10% lime powder, 15% brick dust with 5% lime powder. Using 20% brick dust separately in concrete gives good workability but less compressive strength compared to control sample. Replacing cement by 20% lime powder enhanced 3% compressive strength and split tensile strength compared to control mix. Whereas replacing cement with 15% lime powder and 5% brick dust gives optimum compressive strength and tensile strength compared to control mix. The results shows that lime powder increase the compressive strength and tensile strength compared to concrete made with brick dust. Using 20% lime and brick dust can save cost of cement in range of 7.2%- 12.5% which ultimately save the cost of a project.

Influences of limestone powder on the resistance of concretes to the chloride ion penetration and sulfate attack

Influences of limestone powder on the resistance of concretes to the chloride ion penetration and sulfate attack with a constant water/binder ratio and a constant 28-day compressive strength were studied. The sensitivity of the properties of concrete to the initial moist curing time was also explored. The results indicate that, under a constant water/binder ratio condition, the resistance to sulfate attack of concrete deteriorates with the increasing of limestone powder content, and the resistance to chloride ion penetration decreases when the replacement ratio of limestone powder is 24%. As the initial moist curing time declines, the reducing magnitude of the properties of concrete containing limestone powder is larger than that of plain cement concrete. Nevertheless, lowering the water/binder ratio of concrete containing limestone powder can significantly reduce the sensitivity of the properties of the concrete to the initial moist curing time. No matter how long the initial moist curing time is, replacing cement with 8% limestone powder can improve the resistance of concrete to sulfate attack. Concrete with up to 24% limestone powder addition can still obtain a resistance to chloride ion penetration and sulfate attack similar to plain cement concrete on the premise of a constant 28-day compressive strength. Moreover, it was found that both the crystallization of sodium sulfate and the formation of ettringite collectively result in the deterioration of concrete subjected to the sulfate solution.

Behavior of Self Healing Concrete Over Plain Cement Concrete

Behavior of Self Healing Concrete Over Plain Cement Concrete

Strength behavior of plain cement concrete subjected to true triaxial compression

True triaxial compression test was conducted on 100 mm × 100 mm × 100 mm cubical sample of plain cement concrete using the true triaxial testing machine. A total of 30 tests were conducted on two concrete mixes having characteristic strengths of 24.39 MPa and 34.67 MPa. The minor and intermediate principal stresses were varied from 2.5 MPa to 10 MPa and 2.5 MPa to 30 MPa respectively. The samples were loaded until failure under the stress rate of 1 MPa/min. The failure mode and direction of fracture planes were observed carefully. It was observed that the ratio of intermediate and minor principal stress had an incremental effect on the strength of the concrete. The results obtained from our experimental study as well as the true triaxial compression test data published in literature has been used to conduct a quantitative evaluation of three commonly used failure criteria presented for the concrete. The three failure criteria considered are Drucker-Prager (DP) criterion, Bresler-Pester (BP) criterion, and Hsieh-Ting-Chen (HTC) criterion. It was observed that for the normal strength concrete, the HTC criterion predicts the strength with least error while for the high strength concrete, the DP criterion gives better predictions. Overall the DP and BP criteria underestimate the strength while the HTC criterion overestimates.

Effect of interfacial transition zone on the Young's modulus of carbon nanofiber reinforced cement concrete

Identifying the properties of the region where the cement paste meets the aggregate surface (interfacial transition zone, ITZ) is critical to understanding the strength and fracture behavior of carbon nanofiber (CNF) reinforced cement concrete. In this study, the finite element method is employed to investigate the effect of the ITZ on the Young's modulus of cement concrete made with CNF. The numerical models for cement concrete with and without CNF are constructed based on the digital image processing technique. To consider the interface effect, the concept of “effective aggregate” is put forward, namely, the Young's modulus and Poisson's ratio for each aggregate particle are replaced by an effective Young's modulus and effective Poisson's ratio, in which the effect of thickness and the Young's modulus of ITZ is taken into account in an averaged manner. Then, the quantitative nanomechanical mapping (based on atomic force microscopy) technique is adopted to measure the Young's modulus and thickness of ITZ with and without CNFs, which are further used as the input parameters in the numerical model. The numerical simulation results are verified by experimental testing, which indicates that the ITZ effect should be considered when implementing the numerical simulation. In addition, this analysis shows that compared with the plain cement concrete, CNFs can greatly enhance the mechanical properties of ITZ, which will in turn improve the Young's modulus of cement concrete significantly. Finally, the effect of thickness and Young's modulus of ITZ on the Young's modulus of CNF reinforced cement concrete is also discussed.

Influence of ultrafine TiO2 and silica fume on performance of unreinforced and fiber reinforced concrete

This paper investigates the performance of plain cement concrete (PCC) and fiber reinforced concrete (FRC) with silica fume (SF) and ultra-fine TiO2 (UFTiO2) as mineral admixtures. The size of UFTiO2 was analyzed using Zeta size analyzer. Concrete with a characteristic compressive strength of 50 MPa was chosen. Cement was partially replaced with SF in three different percentages namely 4.5, 9.5 and 14.5 and constant UFTiO2 percentage of 0.5 to have a total replacement level of 5%, 10%and 15%. Steel fibres were added in 0.5% by volume of concrete. Specimens were for various parameters like resistance against compression, water absorption and sorption. In addition, tests on Split tension, flexure and impact were done to study the characteristics of the concrete with fibre. The results were compared with conventional concrete. Concrete with 9.5% SF, 0.5% UFTiO2 was found to be an optimum mix among all the combinations tested in both plain cement and fibre reinforced concrete.

On low-velocity impact response of SIFCON slabs under drop hammer impact loading

The response of thin slabs of Slurry-Infiltrated Fibrous Concrete (SIFCON) with and without reinforcement under low velocity impacts is explored via drop-hammer impact experiments. For comparison purpose, plain cement concrete (PCC) and reinforced cement concrete (RCC) slabs were also cast and tested. To produce SIFCON slabs made with binary cementitious materials, the pre-determined concrete mixtures were designed with 15% of silica fume, 30% of blast furnace as a partial substitute of cement along with a constant 10% of hooked end steel fibres by volume fraction. The replication of a low-velocity impact on slab was achieved by dropping a steel ball (weighing 4.5 kg), with fall height of 457 mm, via the utilization of a self-fabricated drop-hammer impact test device. The parameters like first crack and ultimate failure energy absorption capacity, ultimate crack resistance, crack resistance ratio, ductility indices, and failure pattern were examined. The test results reported that the incorporation of binary blends of silica fume and slag in SIFCON matrix shows better performance in terms of strength and durability characteristics.

Characteristics and reactivity of ferronickel slag powder

In this study, the hydration properties of a blended cement containing 30% ferronickel slag powder are investigated. The activities of electric arc furnace ferronickel slag (EFS) powder and blast furnace ferronickel slag (BFS) powder are both very low under non-alkaline conditions. Due to its higher CaO and Al2O3 contents and lower MgO content, the BFS powder exhibits higher pozzolanic activity than the EFS powder. The reaction of ferronickel slag in the cement decreases the Ca/Si ratio of the calcium silicate hydrate (C-S-H) gel and increases the degree of polymerization of the silicate chains. EFS powder tends to coarsen the pore structure of the hardened paste and decreases the compressive strength of concrete at any age; on the other hand, concrete containing the BFS powder exhibits a late-age microstructure and strength close to or even superior to that of plain cement concrete. Ferronickel slag powder improves the resistance of concrete to chloride ion penetration and the effect of BFS powder is more substantial.

Effect of placement temperature and curing method on plastic shrinkage of plain and pozzolanic cement concretes under hot weather

This paper reports the results of a study conducted to investigate the effect of concrete placement temperature and curing method on the plastic shrinkage of plain and pozzolanic cement concretes. The concrete specimens were cast at a temperature of 25, 32, 38 or 45°C and exposed to the ambient summer conditions. The specimens were cured by applying a water-based curing compound or covering with a plastic sheet. The performance of ordinary Portland (Type I) cement, fly ash (FA), very fine fly ash (VFFA), silica fume (SF), blast furnace slag (BFS) and natural pozzolan (NP) was evaluated by measuring the plastic shrinkage strain. The results indicated that the curing compound was effective in decreasing the shrinkage strain in all concretes. It was also noted that the critical temperature at which the maximum shrinkage strain occurred was 25°C and as the concrete temperature was approaching the ambient temperature, the shrinkage strain decreased. The 28-day compressive and split tensile strength and pulse velocity were also determined to study the effect of placement temperature on these properties. These data indicated that the critical placement temperature was both 25 and 45°C while the optimum temperature for all cementitious materials was either 32 or 38°C.

Long-term properties of concrete containing limestone powder

Plain cement concrete (employed as reference) and three concretes containing limestone powder (replacement ratios of 10, 20, and 30%) were designed. The compressive strengths of the four concretes were close to each other by adjusting the water to binder ratios. The long-term (as long as 5 years) properties of hardened paste and concrete were determined under the condition of equal 28-day compressive strength of concrete. The results show that limestone powder can react with cement but its reaction degree is very low even at 5 years. The addition of limestone powder tends to increase the long-term connected porosity of concrete and the pore structure of hardened paste. The strength and resistance to chloride penetration of the concrete containing limestone powder increase much less than those of plain cement concrete at late ages. When the replacement ratio of limestone powder exceeds 10%, the resistance to carbonation of concrete decreases significantly, but the drying shrinkage of concrete is reduced.

Influence of the initial moist curing time on the sulfate attack resistance of concretes with different binders

The influence of the initial moist curing time on the resistance to the sulfate attack of concretes with different binders and at different water/binder ratios was studied by determining the compressive strength and the chloride ion permeability of the concrete before sulfate attack, the compressive strength after sulfate attack, and the microstructure of the corroded concrete matrix. The results illustrate that both the crystallized sodium sulfate and ettringite formed due to invaded sulfate are the principal expansion sources of the concrete subjected to the sulfate attack environment. Both the additions of fly ash and ground granulated blast furnace slag (GGBS) tend to significantly reduce the permeability and enhance the sulfate attack resistance of concrete on the premise of sufficient moist curing. The enhancing effect of GGBS is greater than that of fly ash on the sulfate attack resistance of concrete with each initial moist curing regime. In the case of insufficient moist curing for 3 or 7days, the compressive strength loss rate of concrete containing fly ash is close to that of the plain cement concrete, indicating that the addition of fly ash makes little contribution to the enhancement of the sulfate attack resistance of concrete. Though the enhancing effect of GGBS on the sulfate attack resistance of concrete decreases with the decrease of moist curing time, the compressive strength loss rate of the concrete containing GGBS is about half of that of the plain cement concrete. The sulfate attack resistance of concrete is less sensitive to the moist curing time at lower water/binder ratio.

Comparative study of accelerated carbonation of plain cement and fly-ash concrete

Accelerated carbonation of plain cement concrete and concrete with fly-ash replacing cement partially, is discussed in the present paper. Mechanical properties such as compressive strength, flexural strength, modulus of elasticity, durability aspects such as depth of carbonation and porosity of carbonated concrete are studied. To study the influence of water binder ratio on the above-mentioned properties, water-binder ratios of 0.35, 0.50 and 0.65 are used. It is observed that the mechanical properties of carbonated concrete have increased with the duration of carbon dioxide exposure. So did the depth of carbonation, whereas the volume of permeable voids has reduced leading to the decrease in porosity. An expression to predict the depth of carbonation of fly-ash concrete has also been developed.

Influence of Curing Time on the Drying Shrinkage of Concretes with Different Binders and Water-to-Binder Ratios

Plain cement concrete, ground granulated blast furnace slag (GGBS) concrete, and fly ash concrete were designed. Three wet curing periods were employed, which were 2, 5, and 8 days. The drying shrinkage values of the concretes were measured within 1 year after wet curing. The results show that the increasing rate of the drying shrinkage of concrete containing a mineral admixture at late age is higher than that of plain cement concrete regardless of the wet curing time. With the reduction of wet curing time, the increment of total drying shrinkage of concrete decreases with the decrease of the W/B ratio. The negative effects on the drying shrinkage of fly ash concrete due to the reduction of the wet curing time are much more obvious than those of GGBS concrete and plain cement concrete. Superfine ground granulated blast furnace slag (SGGBS) can reduce the drying shrinkage of GGBS concrete and fly ash concrete when the wet curing time is insufficient.