Flexural Tensile Strength Tests Research Articles

Avaliação tecnológica de argamassa de revestimento produzida com vermiculita expandida

The construction industry is associated with a high consumption of non-renewable resources, such as sand, in addition to the energy demand involved in the construction processes and the use of buildings. In the search for new technologies for traditional building materials, cement mortars have been modified by replacing sand with lightweight aggregates, such as expanded vermiculite. The aim of the present study is, therefore, to analyze the flexural tensile strength of rendering mortars produced with a 1:1:6 mix ratio by volume, with 10% and 20% substitution of natural aggregate by expanded vermiculite, comparing them with a reference mixture. The experimental phase consisted of the characterization of aggregates, preparation of mortars, tests in the fresh state, and flexural tensile strength tests. Overall, the replacement of sand with expanded vermiculite increased the flexural tensile strength, enhanced the fresh-state bulk density, and reduced the consistency index. Known for contributing to improvements in thermal and acoustic insulation, reducing structural weight, among other effects, the use of vermiculite in mortars demonstrated potential based on the results, as it did not significantly impair the mechanical behavior of the mixtures.

Properties of Macadam Stabilized with Cement and Asphalt Emulsion

The cracking of cement-stabilized macadam (CSM) reflects to the asphalt layer, which is one of the reasons for the failure of pavement performance and structure. Adding asphalt emulsion to CSM can effectively prevent the formation of cracks. The primary purpose of this article is to reveal the effect of asphalt emulsions on the performance of CSM by adding different contents of asphalt emulsion. For this purpose, tests of unconfined compressive strength (UCS), flexural tensile strength (FTS), elastic modulus, and frost resistance were performed on CSM with gradations of CSM-5 and CSM-10 (the maximum particle sizes of the macadam in the gradation composition are 5 mm and 10 mm), respectively. The test results showed that the UCS of CSM decreased with the increment of asphalt emulsion content. The FTS and elastic modulus of CSM increased with the content of asphalt emulsion. Based on the FTS test results, the frost resistance coefficient Km1, defined according to the CSM splitting strength prior to and subsequent to freeze–thaw, was used to evaluate the frost resistance. The test results showed that the frost resistance of CSM improved with the increase in asphalt emulsion content for the same cement content. In conclusion, adding asphalt emulsion to CSM has positive effects on the FTS, elastic modulus, and frost resistance. Therefore, for the purpose of maintaining the UCS value of CSM, the content of cement should be considered at the same time as the controlling of the content of asphalt emulsion.

A numerical study based on GBM3D-DEM model: Multi-level force chain analysis in dynamic flexural tensile strength test

A numerical study based on GBM3D-DEM model: Multi-level force chain analysis in dynamic flexural tensile strength test

Overall feasibility assessment of polyester polyurethane concrete used as steel bridge deck pavement

Traditional pavement materials used in the orthotropic steel bridge deck suffer from various pavement distresses and thus reduce the service life of the steel bridge. Therefore, this study proposed a novel engineered material named polyester polyurethane concrete (PPUC) for the steel bridge deck pavement. Indoor laboratory experiments and numerical comparison analysis were conducted to comprehensively assess the feasibility of PPUC as the steel bridge deck pavement and ordinary Portland cement (OPC), guss asphalt concrete (GAC), asphalt mastic concrete (SMAC) and epoxy asphalt concrete (EAC) were used as references compared with PPUC. After the specimens of PPUC were prepared by mixing polyester polyurethane binder (PPUB) and aggregate with the binder-aggregate ratio of 15%, the specimens were subjected to compressive test, splitting tensile test, flexural tensile strength test, wheel tracking test, low-temperature cracking test, freeze-thaw splitting test, shear test and pull-out test. The mechanical performance comparison of different pavement structures with different materials was also analyzed using finite element analysis method. Results show that PPUC presents higher mechanical properties (compressive, tensile and flexural strength) compared to OPC, and it has good durability properties compared to SMAC, GAC, and EAC, such as high temperature stability, low temperature cracking resistance and water stability. In addition, PPUC has strong adhesive property with steel deck and does not change significantly with temperature changes. The finite element simulation results show that the maximum tensile strength and maximum compressive strength of PPUC in the single-layer structure are 0.51 MPa and 3.52 MPa respectively, which are much smaller than the experimental values and those of other materials. The maximum tensile strength and maximum shear strength of PPUC in the PPUC + SMAC composite structure are 0.232 MPa and 0.148 MPa respectively, which are also much smaller than the experimental values and those of other structures. The mechanical performance comparison results indicate that PPUC pavement structure can improve the overall stiffness of the steel bridge deck and protect the wear layer. These results support that the PPUC has a promising application for the steel bridge deck pavement.

Experimental Study on the Road Performance of High Content of Phosphogypsum in the Lime–Fly Ash Mixture

Phosphogypsum (PG), as a by-product of the production of phosphoric acid, faces the problems of large annual output and difficult treatment. There is a large demand for fillers in the process of road paving, which may be an effective method for the utilization of PG resources. In this study, three proportions of phosphogypsum–lime–fly ash (PLF) mixture were designed, first, according to orthogonal tests. The comprehensive performance of the PLF mixture was tested by the compression rebound modulus test, unconfined compressive strength test, flexural tensile strength test, dry shrinkage test, and temperature shrinkage test, respectively. The results show that adding crushed stone to the PLF mixture can effectively improve the compression rebound modulus, unconfined compressive strength, and flexural tensile strength. The high content of PG in the mixture can also improve the dry shrinkage and temperature shrinkage properties of the mixture. According to the road layer requirements, the optimum proportion of the PLF mixture is recommended, which may benefit the road construction and PG resources.

Development and thermo-mechanical behavior of cement-based composite for the runway concrete of F-35B joint strike fighter

The current study aims at increasing the strength and heat resistance of concrete that can be used in airport pavements for vertical take-off and landing of new generation F-35B combat aircraft by improving concrete mixtures. For this purpose, two different mixtures with lightweight (expanded glass aggregate) and traprock (basalt) aggregate were prepared. The mechanical properties and thermal conductivity of the mixtures were determined, 3D maps of cracks that occurred with the flexural tensile strength tests were examined using fractal analysis, and the fracture energy of the samples was obtained. A statistically significant extremely high correlation was found between fractal dimension and flexural tensile strength. No significant compressive strength losses were observed in samples after heat exposure. We determined that the mechanical properties of the basalt aggregate mixture were better than the expanded glass aggregate mixture, however, its thermal conductivity was higher.

Bond Strength and Fracture Toughness of Alkali Activated Self-Compacting Concrete Incorporating Metakaolin or Nanosilica

This study aims to evaluate the effect of nanosilica (NS) and metakaolin (MK) as binder replacement materials on the fresh and hardened characteristics of slag (GGBS)-based alkali-activated self-compacting concretes (A-ASCC). Therefore, nine A-ASCC mixes, with and without metakaolin, were prepared, as well as mixes with and without NS incorporation. In the production of A-ASCC mixes, GGBS was used as a binder material. The fresh properties of A-ASCC were determined using the L-box, V-funnel, T50 value, and slump flow tests, while the hardened properties were examined using compressive strength, bonding strength (pullout test), fracture toughness, and flexural tensile strength tests. A relationship analysis was also conducted on the A-ASCC experimental data. The experimental results showed that NS and MK had a negative effect on the fresh properties of GGBS-based A-ASCC mixtures, whereas metakaolin had a greater influence. The addition of 1% and 2% NS, on the other hand, improved the mechanical performance of the A-ASCC specimens significantly. The use of more than 2% NS had a harmful effect on the mechanical properties of A-ASCC. A 5% replacement ratio of metakaolin improved the mechanical properties of A-ASCC. The use of metakaolin at ratios of more than 5% had a negative effect on the properties of A-ASCC.

Performance of Alkali-Activated Self-Compacting Concrete with Incorporation of Nanosilica and Metakaolin

This study aims to analyze the influence of nano-silica (NS) and metakaolin (MK) as binder replacement materials on the fresh and hardened performance of alkali-activated self-compacting concretes (A-ASCC). Therefore, nine A-ASCC mixes with and without metakaolin were prepared, as well as mixes with and without NS inclusion. Slump flow, v-funnel, L-box, and T50 value tests were used to investigate the fresh properties of A-ASCC. While the hardened performance was examined using compressive strength, bonding strength (pullout test), fracture toughness and flexural tensile strength tests. A relationship analysis was also conducted on the A-ASCC experimental data. The experimental results showed that the addition of NS and MK had a negative influence on the fresh characteristics of fly ash-based A-ASCC mixtures, while the addition of metakaolin had a higher effect. The addition of 1% and 2% NS, on the other hand, significantly enhanced the mechanical performance of the A-ASCC specimens. The use of more than 2% of NS had a negative influence on the mechanical properties of A-ASCC. The mechanical properties of A-ASCC were improved significantly by metakaolin replacement ratios. The A-ASCC bond strength showed the highest improvement. Furthermore, using NS and/or MK significantly increased the A-ASCC setting time and may be used to produce A-ASCC at ambient environment.

Study on Pavement Performance of Cement Stabilized Recycled Brick Aggregate Base with Basalt Fiber

The solution to environmental problems caused by the generation of construction brick waste is its use as a substitute for natural gravel aggregate in highway base material. The preparation of basalt fiber cement stabilized recycled brick aggregate base material is by adding basalt fiber to cement stabilized recycled waste brick mixture. With the help of nonlateral compressive strength test, indirect tensile (splitting) strength test, and flexural tensile strength test, the influence of basalt fiber with different dosages on the compressive strength, crack resistance, and durability of cement stabilized recycled waste brick mixture was analyzed. The effects of basalt fiber on water loss rate, dry shrinkage strain, and frost resistance of cement stabilized recycled waste brick mixture were analyzed by dry shrinkage test and freeze-thaw test. The bonding morphology of fiber and cement slurry was studied by scanning electron microscopy. The results show that when the waste brick aggregate content is 30% and basalt fiber content is 1‰, the 28-day compressive strength of cement stabilized waste brick mixture is 19% higher than that of the specimen without fiber; indirect tensile strength increased by 36.6%; flexural strength increased by 37.0%; water loss rate decreased by 15.5%; the coherent shrinkage strain decreased by 30.3%; and BDR value (compressive strength loss percentage) increased by 12.3%. Basalt fiber and cement slurry have good bonding force and friction force, which act as tensile reinforcement in the mixture. Fiber bundle and fiber filament compose a fiber network to enwrap the mixture, so that the fiber network and mixture are embedded with each other, thereby improving the mechanical properties and durability of cement stabilized recycled waste brick mixture.

Effectiveness of Concrete Reinforcement with Recycled Tyre Steel Fibres.

The role of searching for industrial waste management solutions in construction is key for environmental protection. Research in recent years has focused on solutions aimed at reducing the carbon footprint. This paper presents the results of tests conducted on concrete reinforced with treated recycled tyre steel fibres (RTSFs) compared to the same amount of manufactured steel fibres (MSFs). The effectiveness of concrete reinforcement with RTSFs was analysed using the fracture mechanics parameters of cementitious composites. Rheological tests, residual flexural tensile strength tests, work of fracture measurements, toughness indices, examinations of the fibre distribution in the concrete, and SEM observations of the concrete fractures with fibres were performed. Determining the work of fracture and toughness indices was an innovative aspect of this paper. As the amount of RTSFs increased, a decrease in the consistency was observed, although the distribution of fibres in the concrete was uniform, as proven by the results of computer tomography tests. Concrete reinforced with RTSFs that is purified and refined during the recycling process might have better properties than concrete reinforced with the same amount of MSFs. The application of RTSFs in construction has environmental and economic benefits in addition to the strengthening of cementitious composites.

Effects of incorporating large quantities of copper tailings with various particle sizes on the strength and pore structure of cement-based materials

Although it is estimated that approximately 300 million tons of copper tailing is produced in China annually, only about 8.2% of this byproduct is reused. Therefore, to promote natural material sustainability, and value-added utilization of copper tailings in China, tailings from Hubei (HT) and Jiangxi (JT) were explored as replacement materials for the fine natural aggregate. The water/cement ratio was fixed at 0.50, and various proportions of fine aggregate were replaced (0%, 30%, 50%, 70%, and 100%). The size distribution of the tailings particles was as follows: HT (1.18 to 0.15 mm) and JT (0.60 to 0.15 mm). This study was made to match the size distribution of the tailings with that of the fine aggregate it replaced. The mechanical properties and pore structure were assessed using the methylene blue test, flexural tensile strength test, compressive strength test, absorption test, fluidity test, mercury intrusion porosimetry (MIP) test, and scanning electron microscopy (SEM). The control group (without tailings) presented the highest flexural strength but the lowest compressive strength. The experiment group achieved the highest flexural and compressive strength under 50% HT content or 70% JT content. Overall, MIP results show that inclusions in tailings tend to reduce “harmless pores” (pores < 20 nm). SEM observations at 7 days revealed that unreacted tailings particles filled the macropores between fine aggregate and paste. Observations at 28 days revealed fewer unreacted tailings particles. The finer tailings particles reacted with calcium hydroxide in cement to form hydrated calcium silicate gel and fill pores, thereby enhancing the strength of cement mortar.

Thin concrete overlays wit carbon reinforcement on deteriorated concrete pavements

In many countries, concrete pavements are normally built as Jointed Plain Concrete Pavements. Due to a lack of alternatives, repairing deteriorated concrete pavements usually requires the replacement of the complete pavement structure and maintaining the joints, which is labour- and resource-intensive. To increase the durability of repairs and to save resources concrete overlays with carbon reinforcement are developed. By the application of non-corrosive carbon-textile reinforcement cracks might be distributed so fine, that such an overlay can be executed jointless, unlike in previous repair methods. For a durable repair the bond behaviour between the retained concrete and the overlay as well as between the overlay-concrete and the textile reinforcement have to be considered. In this paper, the basic principles and feasibility of such a repair method are examined. On the one hand, the decisive influencing variables and parameters such as bond behaviour and cracking behaviour within the overlay are pointed out and discussed. On the other hand, the performed special lab tests will be presented. These tests include cyclic loadings on large-scale beams with integrated overlays of such types, evaluating the bond behaviour and the durability after a few millions of load cycles. Furthermore, the crack formation in the overlay is determined by means of tensile and flexural tensile strength tests.

Use of recycled aggregates from civil construction in self-compacting mortar

abstract: The utilization of wastes from demolition in civil construction in self compacting concrete (SCM) has the potential to reduce both the environmental impact and financial cost. In this context, this article aims to verify the behavior of the incorporation of recycled aggregates of civil construction in the mix designs of self-compacting mortar (SCM) in replacing cement, presenting as an interesting alternative to natural raw materials. This study used the EMMA® software to optimize the choice of percentages of fine recycled aggregates when replacing cement. The proportions chosen were 0%, 5%, 15%, and 25%, through the analysis of the granular packing curve of the respective mix designs. The proportion of 0% has in its composition cement, metakaolin, sand, superplasticizer (SP) and water. The parameters obtained, through tests in the fresh state of the mini-slump and mini-funnel V, certified the samples as SCM. The compressive strength and flexural tensile strength tests in the hardened state demonstrated a reduction in mechanical properties of the material with cement replacement. It is concluded that the waste used brick and ceramic can be added in replacement to the cement in SCM without significant loss of properties in the fresh and hardened state.

Fresh and hardened state performance of self-compacting slag based alkali activated concrete using nanosilica and steel fiber

This study investigates the fresh and hardened state performance of slag-based self-compacting alkali-activated concretes (SCAAC) reinforced with steel fibers (SF) and nano-silica (NS), cured at an ambient temperature. Two different hooked-end SF with two fiber volumes and NS were used to examine the combined effect of the SF volume ratio, SF aspect ratio, and NS on the fresh and hardened state performance of SCAAC. In extension, the influence of specimen thickness to steel fiber length (d/FL) ratio on the failure modes of the bending specimens was evaluated. The fresh state properties were evaluated via T50 value, slump flow, V-funnel, and L-Box tests, while the hardened state properties were studied through compressive strength, splitting tensile strength, modulus of elasticity, and flexural tensile strength tests. The relationship analyses were carried out among fresh and hardened state properties, and scanning electron microscopy (SEM) was also conducted to examine the microstructure. The results indicated that fresh state performance was favorably affected by NS inclusion but adversely influenced by SF content and aspect ratio. The hardened state performances enhanced with a higher amount of SF volume and an aspect ratio. Also, the NS improved the splitting tensile and flexural strength but decreased the compressive strength and elasticity modulus of the specimens. The d/FL ratio was found a significant parameter on failure modes, and the specimens having a d/FL ratio of 3.33 showed flexural cracks. In contrast, the specimens having a d/FL ratio of 1.25 exhibited inclined flexural-shear cracks, especially for 1% SF.

Influence of Fiber Addition on the Properties of High-Performance Concrete.

High performance fiber-reinforced concrete (HPFRC) has been frequently investigated in recent years. Plenty of studies have focused on different materials and types of fibers in combination with the concrete matrix. Experimental tests show that fiber dosage improves the energy absorption capacity of concrete and enhances the robustness of concrete elements. Fiber reinforced concrete has also been illustrated to be a material for developing infrastructure sustainability in RC elements like façade plates, columns, beams, or walls. Due to increasing costs of the produced fiber reinforced concrete and to ensure the serviceability limit state of construction elements, there is a demand to analyze the necessary fiber dosage in the concrete composition. It is expected that the surface and length of used fiber in combination with their dosage influence the structure of fresh and hardened concrete. This work presents an investigation of the mechanical parameters of HPFRC with different polymer fiber dosage. Tests were carried out on a mixture with polypropylene and polyvinyl alcohol fiber with dosages of 15, 25, and 35 kg/m3 as well as with control concrete without fiber. Differences were observed in the compressive strength and in the modulus of elasticity as well as in the flexural and splitting tensile strength. The flexural tensile strength test was conducted on two different element shapes: square panel and beam samples. These mechanical properties could lead to recommendations for designers of façade elements made of HPFRC.

Study of the use of kaolin waste as a partial substitute for fine aggregate in the production of concrete for pavers

The study of the use of kaolin waste has scientific and socio-environmental value by providing an appropriate destination, reducing the demand and consequent problems arising from its extraction, considering that the construction industry is a consumer of a significant amount of raw material. Thus, the study aims to replace the fine aggregate by kaolin waste in the proportions of 10%, 20% and 30%, verifying its feasibility for interlocking sidewalk pieces. The kaolin waste was used with and without fine material, and physical characterization tests of the materials were performed, and then the concrete pieces were subjected to tests of resistance to simple compression, water absorption and resistance to abrasion, as prescribed by ABNT NBR 9781:2013, and flexural tensile strength test, according to ABNT NBR 12142:2010. According to the results and analyzing the compressive strength at 28 days, the mixtures with replacement of 10% of fine aggregate by kaolin waste reached strengths greater than 35 MPa, an acceptable normative parameter, both for the waste with fines and without fines, making its use feasible.

Engineering of composite materials made of epoxy resins modified with recycled fine aggregate

Abstract The paper presents studies performed on polymer-cementitious composite made of epoxy resin coating modified with aggregate and cementitious substrate. Epoxy resin is a perfect material that can be used to protect cementitious materials. According to its manufacturer, it can be mixed with fine aggregate. Coarse aggregate made of building demolition wastes is mostly utilized in concrete mixtures or road structures. Fine aggregate is not widely used. Therefore, the novelty of this research was the utilization of recycled fine aggregate (RFA) in epoxy resin coatings. Natural fine aggregate (NFA) was also used as an extender in the coating. The natural aggregate in the coating was partially replaced with recycled aggregate in amounts of 0, 20, 40, 60, 80, and 100% of its weight. Sixteen specimens of polymer-cementitious composites were prepared for the flexural tensile strength test, and thirty-two specimens for the compressive strength test. The macroscale tests were performed after 35 days of curing (28 days – cementitious substrate, and 7 days – epoxy resin). The results show that the epoxy resin coating does not affect the flexural tensile and compressive strength of the analyzed composites. Moreover, the type of aggregate used in the coating does not have a significant impact on the measured properties of polymer-cementitious composites. Economic analysis was performed in order to estimate the cost of the natural and RFAs used in epoxy resin coatings. The calculations show that a higher amount of RFA should be used to increase savings.

Modeling of Fiber-Reinforced Concrete and Finite Element Method

The article deals with approaches to the modeling of fiber-reinforced concrete with the finite element method and nonlinear analysis. The article aims to determine the input parameters and the mechanical properties for the selected modeling approaches. The chosen fiber-reinforced concrete has the dosage of 75 kg/m3 and two series, which differ, in the type of fiber. For determining the basic mechanical properties, destructive methods have been used. Their purpose has been to determine the compressive strength and the tensile strength. The three-point flexural tensile strength test has included the evaluation of load-displacement diagrams, which have been utilized during numerical modeling. Numerical modeling is based on a 3D computational model in the finite element method and on the fracture-plastic material model. The conclusion includes differences during modeling depending on the type of fiber used.

Fatigue damage analysis of cement stabilized sub-base during construction period

When cement stabilized gravel materials are used as pavement base and sub-base, irreversible fatigue damage often occurs due to insufficient maintenance days during the construction period and overload of vehicle load. In order to obtain the fatigue damage caused by the construction load on the cement stabilized gravel sub-base, the flexural tensile strength test and the fatigue test are carried out based on Miner theory and ABAQUS software. Under 9 kinds of vehicle load, we analyze both the relationship between the maximum tensile stress of the sub-base layer and the substrate thickness when the substrate thickness is 16, 20, 24, 28, and 32 cm and the relationship between the maximum tensile stress of the sub-base layer and the modulus of the sub-base when the modulus of the subbase is 400, 800, 1 200, 1 600, and 2 000 MPa, respectively. The research results show that with the increase of the thickness of the sub-base layer, the tensile stress of the sub-base decreases gradually, and the maximum reduction rate is 8.8%. With the growth of the sub-base modulus, the bottom tensile stress of the sub-base layer increases gradually, but the growth rate continues to decrease. Relying on the actual engineering project, the fatigue prediction equation of the cement stabilized gravel sub-base can be obtained by using Miner theory to calculate the fatigue damage degree of the subbase caused by different construction loads under different working conditions, which provides guidance for the design and construction of the pavement.

Study of the Potential of Adhesion to the Substrate of Masonry and Tensile in the Flexion in Mortars of Coating with Gray of the Sewage Sludge

This work evaluates mortars using sewage sludge calcined at temperatures of 600°C and 700°C as a hydraulic binder replacing the cement. The percentages incorporated by mass to replace the Portland cement were 10%, 20% and 30%, using the 1:3:0,60 (cement: sand: factor a/c) trace. Sludge ash was characterized and tensile strength at flexion as well as tensile strength (pullout test) were evaluated. As a way of performing a comparison with conventional mortars, the same tests were carried out using reference mortar. The results of the flexural tensile strength tests indicated that results were higher than the reference traces of the mortars with the calcined sludge at a temperature of 700°C, a factor related to the increase of the calcination temperature and the incorporated percentage. With respect to the tests on the determination of tensile strength, it was observed that the specimens submitted to the test suffered rupture in the mortar, and that the calcination temperature of the sewage sludge was not influenced. The results obtained with the mortars using sewage sludge ash with partial replacement of the cement are shown within the normative standards and approximate to the results obtained with the tests executed with the reference mortar.