Impact Resistance Of Concrete Research Articles

Effects of basalt fibre and rubber particles on the mechanical properties and impact resistance of concrete

The application of waste rubber particles and basalt fibre (BF) in concrete can not only improve the performance of the resulting concrete but also alleviate the environmental pressures related to waste tire disposal. In this study, the impacts of rubber particles and BF on the mechanical and impact performance of concrete are experimentally investigated. Additionally, the macroscopic test phenomenon is explained based on the appearance of the microstructure. The results show that for basalt fibre-reinforced concrete (BFC), when the BF content increases from 0 to 0.4 %, the cube compressive strength and elastic modulus decrease from 71.5 MPa to 62.5 MPa and 44.5 GPa to 41.0 GPa, respectively, while the bending strength increases from 5.9 MPa to 6.6 MPa and then decreases to 6.3 MPa. A BF content of 0.3 % is selected to prepare basalt fibre-reinforced rubber concrete (BFRC). As the rubber particle content of BFRC increases from 0 to 20 %, the cube compressive strength, elastic modulus and bending strength decrease from 64.3 MPa to 51.5 MPa, 41.9 GPa to 33.5 GPa and 6.6 MPa to 5.9 MPa, respectively. However, the reduction rate of the mechanical properties of BFRC is approximately half that of fibre-free rubber concrete at the same rubber content. The shapes of the stressstrain curves of the BFC and normal concrete (NC) are similar, whereas the descending stage of the stressstrain curve of the BFRC is obviously gentler, and the whole BFRC stressstrain curve is much fuller, reflecting typical ductile failure. Both the BF and rubber particles contribute to impact performance improvement, but the effect of the rubber particles is much greater than that of the BF. Compared with that of the NC, the incorporation of 0.3 % BF increases the initial crack impact energy (W1) and final crack impact energy (W2) by 71 % and 79 %, respectively, but when 20 % rubber particles are additionally added, the increase rates of W1 and W2 reach 668 % and 686 %, respectively. The impact life evolutions of BFC and BFRC can be described effectively by a two-parameter Weibull distribution function.

Development in the Study of Mechanical Prop-erties and Damage Constitutive Models of Rub-ber-Reclaimed Concrete

Advances in rubber-reinforced concrete technology and its applications in engineering are cru-cial for the thorough recycling and safe disposal of waste tire rubber and construction debris. Rubber-reinforced concrete (RAC) is a concrete material produced by substituting some fine and coarse aggregates with waste rubber particles and recycled aggregates. The incorporation of waste rubber particles endows RAC with distinctive mechanical properties and a distinct damage constitutive model. The mechanical properties of rubber recycled concrete mainly in-clude compressive strength, tensile strength, flexural strength, and elastic modulus. Compared to traditional concrete, RAC exhibits slightly lower compressive and flexural strengths but sig-nificantly enhanced tensile strength. This is due to the changes in mechanical properties caused by the softness and elastic properties of rubber particles. In addition, the addition of rubber particles can also improve the energy absorption capacity and impact resistance of concrete. On the other hand, in order to describe the damage behavior of rubber recycled con-crete, some constitutive models were studied. Common models include linear elastic model, plastic model, and damage model. The linear elastic model is suitable for describing the be-havior of rubber recycled concrete during the elastic stage; The plastic model is suitable for describing its deformation behavior during the plastic stage; The damage model can better describe the fracture and failure behavior of rubber recycled concrete, including shear damage, tensile damage, and compression damage. Tailored to the unique characteristics of RAC, these models consider the stiffness of rubber particles and the deformation characteristics of the binding materials, enabling accurate predictions of the stress-strain behavior of RAC. In conclusion, rubber-reinforced concrete possesses excellent mechanical and durability proper-ties, which can be accurately described and predicted using appropriate constitutive models. These findings are crucial for advancing the application and development of rubber-reinforced concrete.

Experimental Study on the Impact Resistance of Polymer-Modified Steel Fiber-Reinforced Recycled Aggregate Concrete

Recycled aggregate concrete (RAC), composed of aggregates sourced from construction solid waste, has garnered significant attention owing to its notable environmental friendliness. In this study, waterborne epoxy resin (WER) and steel fibers (SFs) were introduced into the RAC to enhance its performance. Orthogonal tests were meticulously designed, with the substitution rate of recycled aggregate (RA), SF dosage and WER dosage as variable factors, to comprehensively analyze the splitting tensile strength and impact resistance of concrete. The impact resistance of concrete was investigated via the drop weight test method. Furthermore, scanning electron microscopy (SEM) was employed to scrutinize the microstructure of concrete, investigating the modification mechanism of WER. The results indicated that the addition of SFs exerted the most pronounced influence on the properties of RAC. As the addition of SFs increased from 0 to 1.0%, there were significant enhancements in the splitting tensile strength and impact energy of the specimens. WER exhibited notable improvements, primarily on the splitting tensile strength, while demonstrating an adverse effect on the impact resistance. Utilizing the Weibull distribution theory, the results of the impact tests were fitted and analyzed to predict the impact life of different mixtures. The predicted results showed high correlations with the measured values.

An experimental and numerical study on the hybrid effect of basalt fiber and polypropylene fiber on the impact toughness of fiber reinforced concrete

As the civil aviation industry advances, higher requirements are put forward for the performance of airport cement pavement. The frequent takeoffs and landing of aircraft will cause continuous and large impact load on airport pavement, and combined with long-term natural factors, there will be various structural diseases. These diseases not only affect the service life of pavement, navigation safety. To enhance the impact resistance and durability of concrete, the incorporation of fiber has proven an effective approach, and basalt fibers (BF) and polypropylene fibers (PF) are selected as reinforcement materials in this study. Firstly, the effects of single BF and hybrid BF and PF on the mechanical properties of concrete were explored through compressive and flexural tests considering fiber volume contents (0.1%, 0.15, 0.2%) and lengths (6 mm, 9 mm, 12 mm). Then, the drop hammer impact test method, recommended by ACI committee 544, was refined to evaluate the impact resistance toughness of concrete. Finally, the numerical simulation of the impact test was established to explain the concrete impact damage mechanism. The results show that under less than 0.15% volume content, the single BF can effectively enhance the compressive strength, flexural strength, and impact resistance of concrete. Compared with the single BF, the combination of 12 mm BF and 6 mm PF yields favorable results, encompassing improved mechanical properties and impact resistance, thus exhibiting a positive hybrid effect. The increase in PF length (9 mm) leads to a reduction in compressive strength but an improvement in flexural strength and impact resistance. The simulation of the impact test is constructed and the accuracy is confirmed by comparing the impact times and failure patterns of the specimens. The tensile damage of plain concrete is much greater than the compressive damage, and the cracks will spread rapidly from the upper surface to the lower surface. Compared with plain concrete, the crack width of hybrid fiber reinforced concrete is larger, but the damage degree is more uniform. Fiber can absorb a large amount of impact energy, reduce the emergence of micro-cracks, and improve the impact toughness and toughness coefficient of concrete.

Carbon nanofibers and PVA fiber hybrid concrete: Abrasion and impact resistance

This study investigated the effects of carbon nanofibers (CNFs) and PVA fibers on the mechanical properties, impact resistance, abrasion resistance, and microstructure of ultrafine fly ash (UFA) high-performance concrete when used alone and in blends. CNFs and PVA fibers were incorporated at 0.1 %, 0.2 %, and 0.3 %, respectively. The results of the study revealed that CNFs and PVA fibers significantly enhanced the mechanical strength and cracking toughness of concrete, whether added individually or in blends. The enhancement of cracking toughness was more prominent in the mixed systems with higher fiber additions. Notably, the combined use of CNFs and PVA fibers can also significantly enhance the impact resistance and abrasion resistance of concrete. When the fiber addition is appropriate, the impact energy consumption is significantly increased. The optimal incorporation ratio was 0.1 % by volume of PVA fibers and 0.3 wt% by mass of CNFs. at this ratio, the impact resistance of concrete was improved by 128.24 % and the abrasion resistance was improved by 18.17 % compared to the control group. Further scanning electron microscopy (SEM) and mercury-in-pressure (MIP) tests revealed that the mixing of CNFs and PVA fibers effectively enhanced the densification of the concrete matrix, increased the amount of its hydration products, and strengthened the bonding of the fibers to the matrix.

The combined effect of steel fiber and MgO on the deformation and mechanical properties of high-strength concrete

Shrinkage cracking of concrete is one of the main problems affecting the durability of high-strength concrete. One of the main measures to solve this problem is to use expansion agents to compensate for the shrinkage of concrete. But on the other hand, excess expansion, while compensating for shrinkage, is likely to have a detrimental effect on mechanical properties of concrete. Especially for bridge decks and airport pavement with high requirements for impact resistance, toughness, and crack resistance, the use of expansion agents alone cannot meet the performance requirements. In this study, the mechanical properties and autogenous shrinkage of concrete were studied when MgO expansion agent (MEA) and steel fiber were used simultaneously. The results showed that the expansion produced by MEA increased the porosity while compensating for the shrinkage of concrete. Compared with plain concrete, the porosity increased by 4.4% when MEA was incorporated alone. After MEA and steel fiber were used simultaneously, the steel fiber constrained the expansion of MEA through the adhesive friction between fiber and matrix, which made the interface transition zone (ITZ) between cement paste and fiber densified. In this way, the shrinkage of concrete was avoided without reducing the mechanical properties. Especially when 8% MEA and 1% steel fiber were used simultaneously, the compressive strength and splitting tensile strength of concrete were increased by 20.6% and 65.0% respectively, and the porosity was decreased by 20.9%. The expansion of concrete at 410d when used simultaneously was 371 × 10−6, which was 20.7% lower than that of MEA alone, avoiding the possible adverse effects of excessive expansion of MEA. The research results have guiding significance for improving the crack resistance and impact resistance of concrete.

Influence of Nano Composites on the Impact Resistance of Concrete at Elevated Temperatures

The addition of nanomaterials to concrete efficiently fills the pores of the concrete, thereby improving its hardening characteristics. However, no research is available in the literature that investigated the influence of nano-cement (NC), nano-silica-fume (NS), nano-fly-ash (NF), and nano-metakaolin (NM), which are used as partial replacements for cement, on the impact strength (IS) of concrete at elevated temperatures. This issue is addressed herein. Nanomaterials were used in this study to replace 10%, 20%, and 30% of the cement in four different grades of concrete, starting from M20 to M50, at different temperatures. This nano-blended matrix was exposed to various temperatures ranging from 250 °C to 1000 °C, with an increment of 250 °C. In total, the results of 384 new tests were reported. In addition, morphological changes undergone by the concrete specimens were observed through a scanning electron microscope (SEM). The study revealed that the type of binder, proportion of binder, heating intensity, duration, and cooling type directly influenced the impact strength of concrete when subjected to elevated temperature. In comparison to NC, NF, NS, and NM, the mix with NC possessed superior performance when it was heated at 1000 °C. Prior to being subjected to elevated temperatures, the MK blended concrete mix performed well; however, when subjected to elevated temperatures, the MK blended concrete also experienced severe damage.

Residual impact resistance behavior of concrete containing carbon nanotubes after exposure to high temperatures

Multi-walled carbon nanotubes (MWCNTs) have not only high strength and toughness, but also good thermal stability and thermal conductivity. By investigating the failure patterns and fractal index (i.e., impact crushing fractal dimension Df) of MWCNTs reinforced concrete (MC), this paper explored the effect of MWCNTs on impact resistance of concrete after exposure to high temperature. Results showed that after exposure to high temperature, Df increased with the increase of strain rate and temperature. However, compared with plain concrete (PC), MC had relatively few fragments, low Df value, enormous energy consumption, and high residual dynamic compressive strength. The variation of Df essentially depends on the development of cracks and compactness of concrete. It is precisely because the strengthening and thermal conductivity of MWCNTs on the matrix, which effectively alleviated the thermal cracking and impact crushing, thus improving the thermal resistance and impact resistance of concrete. Moreover, the pore fractal dimension (Dp) of concrete after exposure to high temperatures were also investigated and compared with Df. The results noted that the change trend of Dp and Df of MC and PC were completely opposite. The Dp of MC was larger than that of PC, but its Df was smaller than that of PC.

Test and Detection of Antifreezing and Anticorrosion Performance of Carbon Nanofiber Bridge Concrete.

In order to solve the problems of carbon nanotubes, steel fibers, and carbon nanotubes + steel fibers on the compressive strength and impact resistance of concrete, the author proposes a test method for the frost resistance and corrosion resistance of carbon nanofiber bridge concrete. Using carbon nanotubes and steel fibers as reinforcing materials, the effects of carbon nanotubes and steel fibers on the compressive strength and impact resistance of concrete were studied. Experimental results show that incorporating carbon nanotubes and steel fibers can improve the compressive strength of concrete. Compared with the single-doped carbon nanotubes, the single-doped steel fiber has a greater effect on the improvement of the impact resistance of the concrete. The toughness and ductility of carbon nanotubes and steel fiber reinforced concrete are improved again compared with that of single steel fiber reinforced concrete. The effect of adding 1% steel fiber +0.30% carbon nanotubes is the most significant in enhancing the performance of concrete. Conclusion. The synergistic effect of carbon nanotubes and steel fibers is more conducive in complementing each other's advantages and improving the performance of concrete.

Coupled Effect of Polypropylene Fibers and Slag on the Impact Resistance and Mechanical Properties of Concrete.

The disposal of steel slag leads to the occupation of large land areas, along with many environmental consequences, due to the release of poisonous substances into the water and soil. The use of steel slag in concrete as a sand-replacement material can assist in reducing its impacts on the environment and can be an alternative source of fine aggregates. This is the very first paper that seeks to experimentally investigate the cumulative effect of steel slag and polypropylene fibers, particularly on the impact resistance of concrete. Various concrete mixes were devised by substituting natural sand with steel slag at volumetric replacement ratios of 0%, 10%, 20%, 30%, and 40%, with and without fibers. Polypropylene fibers of 12 mm length were introduced into the steel slag concrete at 0%, 0.5%, and 1.0% by weight of cement as a reinforcing material. Performance evaluation of each mix through extensive experimental testing indicated that the use of steel slag as partial substitution of natural sand, up to a certain optimum replacement level of 30%, considerably improved the compressive strength, flexural strength, and tensile strength of the concrete by 20.4%, 23.8%, and 17.0%, respectively. Furthermore, the addition of polypropylene fibers to the steel slag concrete played a beneficial role in the improvement of strength characteristics, particularly the flexural strength and final drop weight impact energy, which had a maximum rise of 48.1% and 164%, correspondingly. Moreover, integral structure and analytical analyses have also been performed in this study to validate the experimental findings. The results obtained encourage the use of fiber-reinforced steel slag concrete (FRSLC) as a potential impact-resistant material considering the environmental advantages, with the suggested substitution, of an addition ratio of 30% and 1.0% for steel slag and polypropylene fibers, respectively.

Experimental Study on the Mechanics and Impact Resistance of Multiphase Lightweight Aggregate Concrete

Multiphase lightweight aggregate concrete (MLAC) is a green composite building material prepared by replacing part of the crushed stone in concrete with other coarse aggregates to save construction ore resources. For the best MLAC performance in this paper, four kinds of coarse aggregate—coal gangue ceramsite, fly ash ceramsite, pumice and coral—were used in different dosages (10%, 20%, 30% and 40%) of the total coarse aggregate replacement. Mechanical property and impact resistance tests on each MLAC group showed that, when coal gangue ceramsite was 20%, the mechanical properties and impact resistance of concrete were the best. The compressive, flexural and splitting tensile strength and impact energy dissipation increased by 29.25, 19.93, 13.89 and 8.2%, respectively, compared with benchmark concrete. The impact loss evolution equation established by the two-parameter Weibull distribution model effectively describes the damage evolution process of MLAC under dynamic loading. The results of a comprehensive performance evaluation of four multiphase light aggregate concretes are coal gangue ceramsite concrete (CGC) > fly ash ceramsite concrete (FAC) > coral aggregate concrete (CC) > pumice aggregate concrete (PC).

Experimental study of bulletproof concrete

This paper focuses on the study of composite concrete specimen’s resistance under an impact of AK-47 bullet with an estimated projectile’s speed of 715 m/s, and energy of 2019 J. Two sets of samples (a total of nine samples) are fabricated and tested from mortar with 1 cm steel fibers or 1 cm carbon fibers respectively. Tensile and compression tests are applied for the first set of samples, to investigate the effect of steel and carbon fibers on the strength of the specimens. Two ratios (1% and 2%) of fibers per mortar mass are also experienced before assessing the bullet resistance. For the second set of samples, three different composite sandwich configurations are tested with a rear impact test. An Armox-® 500 T plate is applied in front of mortar panels for two configurations. Results show that the addition of carbon and steel fibers to concrete panels enhances the impact resistance of concrete by keeping the panels coherent and preventing them from breaking into fragments, reducing crater diameters and detached mass. The three proposed configurations of sandwiches panels stopped the full perforation of the bullet.

Impact Resistance of Concrete with Recycled Steel Fibers and Crumb Rubber.(Dept.C)

Concrete with waste steel fibers and crumb rubber (WSFCR) was primarily created using components that are extracted from the scrap tires recycling process. Crumb rubber particles of size (1- 4) mm and relative density 1.0 gm/cm3 were included as a partial replacement (10% by volume) of natural sand. Recycled or waste steel fibers were used in four percentages from the total mass of the concrete (0.5%, 1.0%, 1.5%, and 2.0%). The efficiency of WSFCR has primarily been studied to evaluate its performance against impact loads, compared to the performance of traditional concrete (CR 0), rubber concrete (CR 10%), and rubber concrete reinforced with industrial steel fibers (ISFCR). Also, the influence of recycled steel fibers on the different strengths of the rubberized concrete was presented. A total number of eleven slabs (1000×1000×100 mm) were subjected to 10.738 Kg cylindrical steel weight falling from a 1.5 m distance concerning the number of blows at the first crack formation and complete failure. Both WSFCR and ISFCR showed outstanding performance under impact loads compared to CR0 and CR 10% control mixtures. Although ISFCR resulted in a higher impact energy resistance than WSFCR, which showed convergent results and a similar crack pattern; therefore, it is a strong candidate as a low-cost alternative to industrial steel fibers.

Study on Mechanical Properties of Concrete with Different Steel Fiber Content

To discuss the mechanical properties of concrete with different steel fiber content. Two grades of concrete were prepared, and the effects of different content and length of steel fiber on slump, pore structure, compressive strength, splitting strength, flexural toughness and impact resistance of concrete were studied. the fluidity of steel fiber reinforced concrete decreases with the increase of steel fiber content, and the concrete with long steel fiber decreases more than that with short steel fiber With the increase of steel fiber content, the compressive strength, splitting strength, bending toughness and impact resistance of steel fiber reinforced concrete are improved to varying degrees. The splitting tensile strength increases fastest when the volume content of steel fiber is 1.0%~1.5%, and the flexural strength increases fastest when the volume content of steel fiber is 1.0%~2.5%. When the fiber is stressed, it gives full play to its strong tensile capacity and shares the tensile force for concrete materials. According to the comprehensive economy, the optimum steel fiber content is 2% ~ 3%, which provides the basis for subsequent experimental research and construction production.

Experimental Study on Impact Resistance of Concrete Containing Steel Fibers

This study is an experimental study aims to examine the effect of utilization of straight, and low cost steel fibers on the impact resistance of concrete. The impact resistance of steel fiber reinforced concrete (SFRC) was assessed using drop weight test as per ACI committee 544. The steel fibers were randomly dispersed in concrete during mixing. Five mixes made with steel fibers dosages of 0% (control mix), 0.5%, 1%, 1.25% and 1.5% by volume of concrete were examined in the study. The results show that mixes containing steel fibers show better impact resistance than plain concrete (control Mix). The results also indicate that increasing the dosage of fiber increases the impact resistance of concrete but up to a certain content of fibers. The maximum increase was recorded at steel fiber dosage of 1.25% by volume of concrete. Also the patterns of failure of the concrete specimens show that fibers are very effective in increasing the concrete toughness which enhance the ductility of concrete and delays the crack initiation.

HYDROPHOBIZATION OF BASALT FIBER AND ITS INFLUENCE ON THE MECHANICAL CHARACTERISTICS OF SAND CONCRETE

Abstract. The materials of the proposed article are devoted to the study of mechanical properties of sand concrete with the addition of hydrophobized basalt fiber and polycarboxylate superplasticizer Relaxol-Super PC. Adding hydrophobic properties to the basalt fiber causes a decrease of water consumption of fine-grained concrete mixture, which leads to improved mechanical properties of concrete. The aim of the work was to increase the mechanical characteristics of sand concrete by introducing hydrophobized basalt fiber into its composition. The objective of the research is to study the effect of hydrophobized basalt fiber on the mechanical characteristics of sand concrete. The polycarboxylate superplasticizer Relaxol-Super PC (Budindustriya, Zaporozhye) was used to increase the mobility of the concrete mixture. Basalt fiber Bauson-basalt 12 mm long and 18 ± 2μm in diameter was used as a fibrous filler. Sand concrete mixture was prepared in a laboratory forced-action mixer. Dosing of Portland cement, quartz sand and basalt fiber was carried out by weight, water and water-reducing additive ‒ by volume, taking into account the density of the additive. The fiber was introduced into a dry cement-sand mixture. After mixing for 120 ... 150 seconds, water with a dosed amount of additive was introduced into the mixture. The hardening of samples concrete took place under normal conditions in a chamber with a temperature of 20 ± 20C and a relative humidity of at least 95%. The compressive strength of concrete was determined by testing the halves of the samples – beams 4×4×16 cm in size at 28 days of age. The abrasion of the investigated concrete was determined by testing cube specimens with an edge of 7.07 cm on an LKI-3 device in accordance with the procedure set forth in DSTU B.V.2.7-212: 2009 “Building materials. Concrete. Methods for determining abrasion “. The impact resistance of concrete was determined from the results of testing cubic specimens with an edge of 7.07 cm on a vertical dynamic laboratory test machine. Especially effective is manifested positive role hydrophobization basalt fiber in combination with the water-reducing additive Relaxol-Super PC. The introduction of hydrophobic fiber (2 kg/m3) and Relaxol – Super PC (1.2% by weight of cement) into the sand concrete mix provides an increase in the strength of sand concrete by 45 ... 48%, impact resistance by 45 ... 50%. The abrasion of concrete is reduced by 36 ... 48% compared to the control.

Analyses on impact behaviour and reinforcement mechanism of basalt fiber and textile reinforced cement-based composite materials

The research work is conducted to investigate the influence on the dynamic mechanical properties of concrete with different volume content of basalt fibers and the different layers number of basalt fabrics, as well as the hybrid effect between fibers and fabrics. The relationships among the impact force, impact time, displacement of the specimens and their failure patterns were analyzed. The results showed that the basalt fabric could significantly improve the brittleness and the impact resistance of concrete. Moreover, the impact force and energy absorption of the specimens increased continuously with the increase of impact energy. The fabrics could play the vital roles in transmitting stress, absorbing energy and bearing load. Basalt fiber could enhance the impact resistance of concrete but it was not obvious. Finally, the different reinforcement mechanisms of basalt fiber and basalt fabric under impact load were proposed.

Impact resistance of plain and rubberized concrete containing steel and polypropylene hybrid fiber

Hybridization of polypropylene–steel fiber leads to improvements of both the mechanical properties and impact resistance of concrete. This paper provides the results of an experimental impact test, which has been conducted using a low-velocity drop hammer (with an impact velocity of 2.8 m/s) on fiber-reinforced concrete (FRC) and fiber-reinforced rubberized concrete (FRRuC) prisms. Prism specimens, measuring 100 × 100 × 500 mm (depth × width × length), were prepared. The variables were different ratios of micro steel (MS) fiber (0%, 0.75, 0.825, 0.9 %, 1.0 %) and polypropylene (PP) fiber (0%, 0.1 %, 0.175, 0.25 %, 1%) with/without crumb rubber (CR) with a partial replacement of fine aggregate at a ratio of 20 % by volume. FRC with CR produced higher first and final impact energy compared with prisms without CR. By contrast, the density, as well as the compressive and tensile strengths decreased, whereas the voids and water absorption of concrete increased due to the CR replacement. The specimen, which was reinforced with 0.9 % MS + 0.1 % PP hybrid FRRuC, produced high final impact energy of approximately 887.2 J, which was 10 times higher than that of plain concrete ; the impact ductility index was 4.15, which was twice the value of plain concrete. Furthermore, the most significant improvement in mechanical properties was found for specimens with 0.9 % MS + 0.1 % PP hybrid fiber.

Effect of the fibre type on concrete impact resistance

Fibre Reinforced Concrete performance is evaluated in terms of bending residual stresses. Although fibre concrete is suitable for structures exposed to impacts and other extreme loads, there is not much information about the relationship between the static residual capacity and the impact strength. Concretes incorporating steel, glass and polymer macrofibres were evaluated by means of a repeated drop-weight impact test. The cracking resistance and the post-cracking behaviour were compared. While the first crack mainly depends on the matrix strength, there is a direct relationship between static residual stresses and the impact resistance, but it varies with the type of fibre.

Effect of Cold Temperatures on Performance of Concrete under Impact Loading

This study investigated the effect of cold temperatures on impact resistance and mechanical properties of a number of self-consolidating and vibrated concretes. Different mixture compositions were developed and tested under compression, four-point bending, and drop-weight impact loading. All tests were conducted at four different temperatures: +20°C, 0°C, −10°C, and −20°C. The studied variables were supplementary cementing materials (SCMs) [including fly ash (FA), slag (SL), silica fume (SF), and metakaolin (MK)]; the nominal maximum coarse aggregate size (10 and 20 mm), coarse-to-fine (C/F) aggregate ratio (0.7 and 2), and binder content (250 and 500 kg/m3). In addition, 35-mm steel fibers were introduced in one self-consolidating concrete (SCC) mixture for comparison. The experimental results indicated that the compressive strength, flexural strength, and impact resistance of all developed mixtures were generally improved as the temperature decreased. These improvements were more pronounced in mixtures with a relatively low binder content of 250 kg/m3 and mixtures with a higher C/F aggregate ratio. On the other hand, the lowest improvements were observed in higher strength mixtures and mixtures with more reactive SCMs such as SF or MK. Colder temperatures also boosted the role of fibers in improving the flexural strength and impact resistance of concrete.