Tensile Strength Of Cement Mortar Research Articles

Influence of nano-coated micro steel fibers on mechanical and self-healing properties of 3D printable concrete using graphene oxide and polyvinyl alcohol

High ductility cementitious composite is one of the proposed new generations of concrete for use in 3D concrete printing with a large dosage of microfibers. This large volume of fibers negatively affects printed layers’ fresh properties and durability. It also increases the porosity of concrete and is not cost-effective. Accordingly, through an experimental program, this article introduces a novel coating technique to reduce the required quantity of fibers for 3D concrete printing. Polyvinyl alcohol (PVA) is used in the present study to help in coating graphene oxide (GO) nanomaterials on the surface of micro steel fibers. Compressive, direct tensile, and bending tests are considered for the mechanical properties. The self-healing property of the proposed mixture is also checked by applying pre-loading on direct tension and bending samples and followingly putting for the healing period. The results show that the nano-coating method improves the compressive and direct tensile strength of cement mortar so that this technique can be used to reduce the volume percentage of steel fibers to achieve the same mechanical characteristics. Also, promising findings were obtained for the self-healing properties of cementitious composites containing nano-coated fibers.

STUDY THE EFFECT OF ADDITION GLENIUM 51AND SILICA FUME ON THE MECHANICAL AND PHYSICAL PROPERTIES OF ORDINARY PORTLAND CEMENT

This research includes a study of the effect of adding Glenium 51 polymer and silica fume on the mechanical and physical properties, which included compressive, flexural and tensile strength of cement mortar and comparing the results with reference cement mortar. Glenium 51 and silica fume were added in different weight ratios as a percentage of the cement weight, and the results showed increase in compressive strength, flexural and tensile strength. All experiments were conducted with different temperatures of 7C°, 20C°, 55C° respectively to demonstrates the effect of different temperatures on cement strength and the polymers behaviour and the results showed that the compressive, flexural and tensile strength of the cement mortar reached its maximum value at the temperature of 20 C° for the moulds and there is increase in the compressive, flexural and tensile strength after adding the additives in all temperature. The values of the compressive and tensile strength used the standard specimens at the age of (2& 28 ) days.

X-Ray Computed Tomography Analysis of Magnetically Oriented Short Steel Fibers and their Effect on Uniaxial Tensile Strength of Cement Mortar

AbstractThe main objective of this study is to quantitatively determine the magnetic field capability of a Helmholtz coil in orienting steel fibers and show the correlation between the fiber orient...

Effect of graphene oxide and nano silica on mechanical and durability properties of cement mortar

Nowadays, nano-technology has already influenced many fields, including civil engineering also. Cementitious composites contain various nanomaterials that have considered as novel materials with improved microstructure, mechanical and durability properties. Recently graphene oxide and nano silica have appeared as the most promising nano-materials for civil engineering applications. However, graphene oxide and nano silica addition in the cement mortar improves the compressive strength, split tensile strength and flexural strength. Ultra-high resolution field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis are used to see the fracture surface of samples containing 0.07% GO and 4.5% of NS to the weight of cement indicated that GO and NS flakes were well dispersed in the cement mortar matrix and no aggregates were observed. The compressive, bending, and split tensile strength of cement mortar, which contains 0.07% GO and 4.5% of NS by weight of cement after 28 days of curing, is raised by 22.25%, 38.77%, and 10.25%, respectively, as compared to regular cement mortar. These durability studies, such as acid resistance and salt resistance, the weight loss was found in acid, and salt immersion addition of GO&NS shows good resistance in the cement matrix. In addition, SEM analysis has shown the growth of calcium silicate hydrates (C-S-H Gel) in GO and NS cement mortar has compared with normal cement mortar.

Performance evaluation of polyurethane-nano silica modified cement mortar

Cement mortar is known to be effective in taking compression than tension. The tensile strength of cement mortar is a cause of concern when it comes to unreinforced applications. The present study aims at performance evaluation of Polyurethane (PU) and Nano silica blended cement mortar. Various proportion of polyurethane (0.5%, 1%, 2%) modified with nano silica (5%, 10% by weight of PU) is blended to the mix during specimen preparation. The water-cement ratio is maintained at 0.35 and the superplasticizer dosage maintained at 0.2% weight of cement. The performance study such as compressive strength, split tensile strength, resistance to thermal exposure, abrasion resistance was done. The relative assessment was also done with cement mortars incorporating silica fume (5% by weight of cement). Compared to cement and silica fume incorporated mortar, the mixes modified with PU-nano silica shows enhancement in split tensile strength. PU-nano silica composite also shows improvement in durability properties. XRD characterization was also performed on the composite mortar to identify the compounds present.

Influence of Plantain Pseudostem Fibres and Lime on the Properties of Cement Mortar

This study investigated the properties of cement mortar with lime reinforced with plantain pseudostem fibres. Experimental specimens with 0, 0.25, 0.5, 0.75, and 1% fibre contents by weight of sand and 10% lime content by weight of cement were prepared and tested on 7, 14, 21, and 28 days of curing for density, tensile strength, compressive strength, SEM, and EDS. The 0.25% plantain pseudostem fibre reinforced mortar achieved 23.4% compressive strength improvement over unreinforced mortar specimens. There was between 6.89 and 13.80% increase in tensile strength of the plantain pseudostem fibre reinforced mortar over the unreinforced mortar specimens. A positive linear correlation was found between the compressive strength and tensile strength of cement mortar reinforced with plantain pseudostem fibres and lime with coefficient of determinant (R2) values between 0.909 and 0.869. It was also observed that the plantain pseudostem fibre reinforced mortar specimen had some microcracks and voids from the SEM analysis. Furthermore, EDS analysis showed the presence of calcium silicate hydrate with a Ca/Si ratio of between 1.02 and 2.49, and Al/Si ratio of between 0.76 and 0.81 as the main oxide. It therefore concluded that the incorporation of plantain pseudostem fibre and lime positively influenced the properties of the cement mortar with the 0.25% fibre content being recommended for construction application.

Tensile behavior of fiber reinforced cement mortar using wastes of electrical connections wires and galvanized binding wires

This study aims to improve the tensile strength of cement mortar using recycled short copper fibers (CE) from wastes of electrical connection wires and long steel fibers from galvanized binding wires (GB). Therefore, a series of direct tensile tests were performed to investigate the tensile behavior of mono and hybrid fiber reinforced cement mortar in addition to compressive and flexural strengths properties. Different hybrid ratios (CE: GB = 0: 100, 100: 0, 50: 50, 30: 70, and 70: 30) % and fiber volume contents (0.5, 0.75, 1, 1.5 and 2)% were studied to investigate their effects on the tensile behavior. The test results revealed the following: (i) the (GB) fibers improve the flexural strength in all volume fraction ratio when compared with (CE) fibers and the optimum ratio was 1%. While for mixtures with hybrid fibers, the (30%CE to 70%GB) combination gives the highest percentage increase in flexural strength at 1.5% volume content when compared with all other mixtures; (ii) for both types (GB) and (CE) fibers, the direct tensile strength increases with the increase in volume fraction ratio till 1.5%. While, for hybrid fibers, the direct tensile strength increases with the increase in fibers ratio for all volume contents and for all combinations; (iii) the largest increase in direct tensile strength is observed at 1.5% volume content of (GB) fibers and give the highest values in comparison with (CE) fibers and hybrid fibers in all mixes; (iv) the brittleness ratio ranges between (4%-8%), (5%-10%) and (4.5%-9.5%) for (CE), (GB) and hybrid fibers cement mortar, respectively. And the direct tensile strength is nearly about 55% of flexural tensile strength as average for all fibrous cement mortar.

Generating water/binder ratio -to- strength curves for cement mortar used in Masnory walls

In this paper, influence water/binder ratio on the hardened state properties of cement mortar was investigated after 28 days curing period as assigned by ACI Standard. From the results, empirical equations have been generated evaluating the strength of cement mortar mixes with various water/binder (w/b) ratios. It was deduced that Abram’s law is valid most of cement mortars established. The cement mortar consists of ordinary Portland cement with 15% partially replacement by silica fume, fine aggregate (sand) with varying portions of 1:3, 1:4, 1:5, 1:6 and different water binder ratios ranged from 0.4 to 0.8. From results, a relationship between split tensile strength and compressive strength of cement mortar has been reached. Furthermore, it was observed, from the results; that a reduction in compressive and tensile strength of cement mortar, while, increasing the water-to-binder ratio higher than 0.5 in case of cement: sand of 1:3. While, this effect was deduced at water-to binder ratio of 0.7 when using cement: sand of 1:4, 1:5, and 1:6. It is concluded that the optimized water-to-binder ratio required for achieving workable cement mortar was mainly based on cement: sand portions. Moreover, empirical equations were generated to predict the relevant compressive and tensile strength to the w/b ratio and cement: sand ratio for practical. The predicted values revealed a good agreement with the experimental results observed.

Split Tensile Strength of Cement Mortar Incorporating Micro and Nano Silica at Early Ages

Split Tensile Strength of Cement Mortar Incorporating Micro and Nano Silica at Early Ages

Effect of some biotic factors on microbially-induced calcite precipitation in cement mortar.

Sporosarcina pasteurii, a common soil bacterium has been tested for microbial treatment of cement mortar. The present study also seeks to investigate the effects of growth medium, bacterial concentration and different buffers concerning the preparation of bacterial suspensions on the compressive strength of cement mortar. Two growth media, six different suspensions and two bacterial concentrations were used in the study. The influence of growth medium on calcification efficiency of S. pasteurii was insignificant. Significant improvement in the compressive as well as the tensile strength of cement mortar was observed. Microbial mineral precipitation visualized by Scanning Electron Microscopy (SEM) shows fibrous material that increased the strength of cement mortar. Formation of thin strands of fillers observed through SEM micrographs improves the pore structure, impermeability and thus the compressive as well as the tensile strengths of the cement mortar. The type of substrate and its molarity have a significant influence on the strength of cement mortar.

Role of water/cement ratio on strength development of cement mortar

The effect of water/cement (w/c) ratio on the mechanical properties such as compressive strength and split tensile strength of cement mortar cylinders and cubes was investigated experimentally for 28 days curing period as per IS standard. Based upon the experimental results, empirical equations have been developed to predict the strength of cement mortar mixes with various w/c ratios. It is observed that Abrams’ law is applicable for the cement mortar also. The cement mortar contains varying proportions of portland pozzolana cement (PPC) and river sand such as 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 with different w/c ratios. An empirical equation has been developed between split tensile strength and compressive strength of cement mortar. Results show that compressive strength and split tensile strength of cement mortar decreased with an increase in the w/c ratio. It is observed that minimum w/c ratio required to make the cement mortar workable is 0.5.

Experimental Study on Dynamic Tensile Strength of Cement Mortar Using Split Hopkinson Pressure Bar Technique

The dynamic characterization of cement-based materials under high strain rates is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. Abram’s law, which was originally formulated for cement-based materials under static loading, is not directly applicable to the dynamic loading condition. In this paper, a modified relationship has been proposed to evaluate the tensile strength of cement mortar. An extensive experiment was carried out to determine the effect of strain rate and water-to-cement (w/c) ratio on tensile strength of cement mortar. The dynamic characterization of tensile strength has been carried out by the split Hopkinson pressure bar at high strain rates. The results of the tests show a significant strain rate–sensitive behavior, exhibiting dynamic tensile strength of cement mortar increases with an increase in strain rate. The influence of w/c ratio on dynamic increase factor is minor.

Influence of porosity on compressive and tensile strength of cement mortar

The compressive, flexural and splitting tensile strength of cement mortar has been measured and interpreted in terms of its porosity. The authors first reviewed the existing porosity–strength relationships (Ryshkewithch, Schiller, Balshin and Hasselman model) and assessed the suitability of existing relationships. The Zheng model for porous materials has been used to evaluate the porosity–strength relationship of cement mortar. Over the porosity ranges examined, the extended Zheng model is good representation of the experimental data on the strength of cement mortar. Based on the generality of the assumptions used in the derivation of the extended Zheng model, this model for cement mortar can be applied for other cement-based materials. The experimental data also show that the ratio between compressive strength and indirect tensile (splitting tensile and flexural) strength of cement mortar is not constant, but is porosity dependent. The ratio decreases with increase porosity values of cement mortar.

Study on Toughening Cement-Based Composites with CaCO<sub>3</sub> Whisker and Fiber

Low tensile strength and high brittleness are the inherent defects of cement-based composites. So improving the toughness effectively is an urgent need for developing high-performance cement materials. The aim of this study is to study the toughening effect by mixing CaCO3 whiskers and polypropylene fibers in cement mortar. The results showed that CaCO3 whiskers could increase the split tensile strength of cement mortar of 28d age by 26.2% at maximum with the whisker content of 10wt.%; when CaCO3 whiskers content was 10wt.% and polypropylene fibers content was 0.20vol.%, the split tensile strength of cement mortar was increased by 21.1% at 28d age; when the fiber length was 19mm, the composite toughening effect of whiskers and fibers was more effective. The toughening mechanisms of CaCO3 whiskers and polypropylene fibers in cement mortar were also discussed.

A three-layer built-in analytical modeling of concrete

It has been accepted in recent years that concrete can be treated as a three-phase composite, consisting of a cement mortar continuous phase, a coarse aggregate dispersed phase, and interface transition zone (ITZ)– an interphase between cement mortar and coarse aggregates. A large number of experiments have been conducted to investigate the effect of every phase on the mechanical properties of concrete; however, the analytical modeling studies have not been conducted as extensively as experimental studies have. In this paper, a three-layer built-in model was developed by assuming coarse aggregates as spheres and embedding a spherical coarse aggregate coated with an ITZ-like interphase and cement mortar layer with uniform thickness into equivalent concrete media. The preliminary calculation results show that, for the three-phase concrete, each phase has several effective factors for the improvement of the mechanical properties of concrete. For overall evaluations, the effective factors are: 1) reducing the elastic modulus of cement mortar and ITZ-like interphase and increasing the elastic modulus of coarse aggregates, 2) decreasing the coefficient of thermal expansion of each phase, 3) enhancing the tensile strength of cement mortar and reinforcing the deformability of ITZ-like interphase, 4) reducing the volume fraction of cement mortar and increasing the concentration of ITZ-like interphase and coarse aggregates phase, 5) decreasing the maximum grain size of coarse aggregates, and 6) adopting open-graded coarse aggregates.

Influence of drying and water supplying after drying on tensile strength of cement mortar

This paper is concerned with the change in tensile strength of cement mortar sibjected to rapid drying and water supply after drying. Flexural strength was investigated for several cement paste specimens cured in water for a certain period, with some specimens dried for 1 day and cured again in water after drying. As a result, it is known that the flexural strength of the specimen allowed to dry becomes about 1 3 of that of a sound specimen, but it is almost recovered after about 3 h water curing after drying. The reason why the strength changes is usually connected with a restrained stress due to drying shrinkage and a stress relaxation due to expansion caused by water absorption. However, when the restrained stress at the surface overtakes the tensile strength, and a considerable number of minute cracks occur, as was observed, the above explanation cannot be accepted, because the tensile stress is almost perfectly relaxed by the occurrence of the cracks. In this paper, the reason for the strength recovery as a result of water absorption is reconsidered by means of stress analysis and microscopic examination of the cracks.

低温におけるセメントモルタルの力学的性質

With the rapid progress of the chemical industry and the result of coming energy crisis, there is a tendency to increase in usage of a wide range of energy resources and in the quantities. Most typical liquid fuels are liquefied natural gas (LNG). As a result, many diversified hazards associated with LNG are recognized. LNG will be stored in tanks made of, concrete or in underground spaces. But there are many unknown points about behavior of concrete and rocks at low temperatures. Here, the authors studied mechanical characteristics of cement mortar in range of temperature from room temperature to-180°C.Main results obtained are as follows:1) The tensile strength of cement mortar becomes maximum at the temperature of about-150°C and is 2.4 times as large as that at the room temperature.(See Fig. 3)2) The maximum compressive strength is obtained at abovementioned temperature and is 2.2 times as large as that at the room temperature.3) The maximum Young' modulus and Poisson' ratio are obtained at the temperature of about-150°C, and are1.4 and 1.5 times larger than those observed at the room temperature respectively.4) When samples are saturated with water, their maximum tensile and compressive strength are 4.5 times as large as values obtained at the room temperatures. And their Young's moduli become much larger.