The Effect of Fiber Hybridization on the Permeability and Porosity of Concrete Aerodrome Pavement: A Review

Objectives: Utilization of steel fiber increases concrete strength and ductility however, the cost of steel fiber is high and ultimately leads to an increase in the cost of concrete. Basalt fiber is a new type of fiber with high strength and toughness and can effectively replace the place of steel fibers. In this paper, concrete reinforced with polypropylene fibers and basalt fibers was tested for its mechanical properties and compared with the same predicted through a simulated model created by the Artificial Neural Network. Methods: The percentage of polypropylene fiber was kept at 0.25%, and different amounts of basalt fiber were added as 0%, 0.25%, 0.5%, 0.75%, and 1%. Based on traditional testing methods compressive strength, tensile strength, and flexural strength of normal concrete, Fiber reinforced concrete and Hybrid fiber reinforced concrete have been found. To forecast the concrete qualities, the model was simulated after the datasets were trained using a neural network fitting tool. Findings: In comparison to concrete that had only 0.25% polypropylene fiber, a hybrid fiber-reinforced concrete mix including 0.5% basalt fiber and 0.25% polypropylene fiber demonstrated a 9.69% improvement in compressive strength. In comparison to the concrete made only of polypropylene, the mix containing 0.25% polypropylene fiber and 0.75% basalt fiber showed a 26.12% increase in flexural strength and a 39.25% increase in split tensile strength. The error percentage between predicted and experimental values is below 10%. Novelty: Utilization of basalt fiber in concrete is very rare and this proposed work focused on the hybridization of basalt fiber in the place of steel fibers, which is prone to corrosion and reduces the cost of material effectively. The concrete's flexural and tensile strengths were significantly increased by the addition of basalt fibers. The mechanical characteristics of hybrid fiber-reinforced concrete are well predicted by the simulated ANN model. Keywords: Basalt fiber, Polypropylene fiber, Artificial Neural network, Fiber reinforced concrete, Hybridization

<p>Alkali Silica Reaction (ASR) is a chemical reaction that negatively affects concrete pavements strengths and integrity. ASR impedes concrete pavements' performance due to the formation of cracks and ultimate deformation if not properly controlled. Concrete pavements are gaining more relevance due to their ability to be constructed on soils with low bearing capacity and support high traffic loadings, thus increasing the need for studies on how ASR in the concrete pavements can be mitigated. This study employed compressive and flexural strength tests to determine the strength properties and deformation of concrete pavements due to ASR when partially replaced with CBA at varying percentages. Static structural modelling of the concrete as a multiphase material in which aggregates, cracks and gel formations are considered as embedded inclusions in the cement paste is then carried out. The results are then compared with relevant standards and findings of other researchers. The study's findings reveal that all the concrete cube samples passed the recommended compressive strength for rigid pavement, which range from 35 - 40 N/mm<sup>2</sup> at 28<sup>th</sup> day. The concrete cube samples also passed the target strength of 48.25 N/mm<sup>2</sup> obtained from the mix design. The effect of ASR resulted in lower compressive and flexural strengths observed at 180<sup>th</sup> and 240<sup>th</sup> days with lower CBA addition, while samples containing higher CBA contents had increasing compressive strength. The static structural modelling results reveal that the maximum deformation was obtained for the concrete cubes admixed with 0% CBA with 47.045 mm while the least deformation was obtained at 30% CBA replacement with deformation value of 5.542 mm on application of a 900 KN force. Therefore, the study posits that CBA addition will help reduce Portland Cement Concrete Pavement deformation due to ASR in relation to traffic loadings.</p>

The use of concrete in construction has remained relevant over time. However, advocates for sustainable construction and structural innovation prove that there could be more in concrete. Studies have particularly focused on improving its durability and strength. In line with these, this study aims to evaluate the compressive strength of M25 and M50-grade concrete cylinders reinforced with basalt and PAN fibers. Moreover, it aims to design and test fiber mixtures, assess their sustainability, and develop a structural model to optimize performance. The researchers first determined the properties of polyacrylonitrile and basalt fibers subjected to test and compare theoretical models. Then, the researchers performed a structural performance optimization of fiber-reinforced concrete. Concrete specimens have been cured and tested in compression through the Universal Testing Machine (UTM). Aiding in the gathering and analysis of data, the study adopted descriptive statistics, central tendency measures, student t-tests, and cost-benefit analysis as statistical treatments. Four simulations were run, and variables such as Poisson's ratio and Young's modulus were held constant due to limitations in equipment and literature. The garnered concrete compressive strengths concluded with their reduction, specifically found in specimens with added PAN and basalt fibers. Stress simulations and structural models also validated this reduction. Furthermore, fiber-reinforced concrete was more costly with the addition of required steel rebars, thus increasing the cost of materials. It was also found that these fibers provided no structural benefit, as the statistical analysis showed no significant difference between fiber-reinforced and regular concrete mixtures. In addition, they could not enhance crack resistance and durability. Since material selection and production monitoring are as essential as fiber dispersion and curing conditions, engineers focus on these variables as they affect performance. This meant higher construction costs due to the reduced compressive strength of the concrete. With these, the researchers recommend further studying PAN and basalt fiber to clarify their effect on compressive strength. Furthermore, long-period evaluation must be done on fiber-reinforced concrete's structural durability for environmental conditions.

A numerical procedure is presented for studying the effects of steel reinforcement and environmental parameters on the early­ aged behavior of continuously reinforced concrete (CRC) pavements. The numerical procedure consists of two stages. The first stage predicts shrinkage strains developed due to moisture loss in the concrete pavement. It uses the semi-discrete method of nonlinear finite element analysis to predict the moisture distribution in CRC pavement as a function of time. This model is verified with published theoretical and experimental results. An existing finite element model (originally developed for the analysis of moisture distribution in subgrade materials) is modified and adapted for moisture distribution analysis in concrete pavements. Both shrinkage and thermal strains are determined in two stages of analysis. Shrinkage strains (predicted in the first stage) and the thermal strains (predicted in second stage) imposed due to variations in ambient temperature are used as input to the stress analysis. The second stage predicts stress distribution taking into account concrete creep in the pavement after initial development of the crack pattern. The CRC pavement is represented in the finite element analysis with two-dimensional plane strain elements. Bond slip is modeled at the interface of concrete and steel. Analysis of the internal restraint is performed to determine subsequent concrete pavement stresses due to environmental effects. A finite element code was developed specifically for the prediction of the resultant stresses in the concrete pavement.

The article outlines the development of concrete road pavements in Poland and the experiences related to the recycling of such pavements constructed in the 1930s. It presents typical damage to concrete pavements and describes a method for the evaluation of such damage with the use of the Road Pavement Condition Diagnostics system developed by the General Directorate for National Roads and Highways in Poland. The article observes that the system lacks criteria for the assessment of the recyclability of concrete road pavements. The results of tests performed for the actual concrete pavements and numerical analyses of stress distributions within pavement joints served to propose such recyclability criteria. These criteria include pavement slab modules and load transfer efficiencies in the joints. The paper also presents in situ methods for recycling concrete road pavements and for the use of the recycled material as base course for concrete or flexible pavements.

This study investigates the static mechanical behavior of a novel eco-friendly high-performance concrete (HPC) reinforced with fibers under different moisture conditions, reflecting the humidity variations commonly encountered in engineering practice. Three saturation levels—natural, dry, and water saturated—were considered. The optimal dosages of basalt and glass fibers were first identified through tests in the natural state, and empirical relationships between fiber volume fraction, compressive strength, and fracture energy were established. Comparative experiments were then conducted at the optimal dosages under varying saturation conditions. Results show that basalt fiber provides superior compressive strength, exceeding that of glass fiber by 0.86% in the dry state and 10.66% in the saturated state. Conversely, glass fiber exhibits a greater enhancement in flexural strength, with improvements of 14.91% and 3.38% over basalt fiber under dry and saturated conditions, respectively. Although preliminary models were proposed to correlate fiber volume fraction with strength in dry and saturated environments, their predictive accuracy proved limited. Overall, the findings highlight the distinct reinforcing effects of basalt and glass fibers on HPC under different moisture conditions, offering guidance for the design and application of fiber-reinforced recycled concrete in humid service environments.

Excellent mechanical properties are a prerequisite for the widespread application of different types of concrete in practical engineering. However, when coal gangue (CG) is used as coarse aggregate (CA) and geopolymer cement is used as auxiliary cementitious material, while reducing the demand for ordinary cement and industrial waste emissions, it has a negative impact on mechanical performance. Therefore, in response to the data gap in the study of mechanical properties of coal gangue coarse aggregate-fly ash geopolymer concrete (CG-FA-GPC), inspired by a large number of research results on fiber-reinforced concrete, this study uses basalt fiber (BF) as a reinforcing material to investigate the enhancing effect of BF on the mechanical properties of CG-FA-GPC. We selected compressive strength, flexural strength, splitting tensile strength, and stress–strain curve as evaluation indicators to compare and analyze the mechanical properties of ordinary concrete, CG-FA-GPC, and basalt fiber-reinforced coal gangue coarse aggregate-fly ash geopolymer concrete (BF-CG-FA-GPC), and to explore the reinforcement effect of BF. The results showed that with the increase in CG substitution rate, the compressive strength, flexural strength, and splitting tensile strength of CG-FA-GPC significantly decreased. A 100% CG substitution reduced the compressive strength, flexural strength, and splitting tensile strength of CG-FA-GPC by 34.5%, 43.4%, and 31.8%, respectively. The stress–strain curve reveals the dual effects of BF on the strength enhancement and deformation modification of CG-FA-GPC. With the increase in BF content, the three mechanical strengths of CG-FA-GPC show a pattern of first increasing and then decreasing, and the optimal BF content is 0.4% (volume fraction). This experiment lays the foundation for promoting research on the mechanical properties and durability of different fiber-reinforced CG-FA-GPC, advancing the feasibility of its large-scale engineering applications.

Concrete in practical applications has to inevitably suffer various impact loads. Recent research indicates that the hybrid fiber reinforced concrete (FRC) has better dynamic mechanical properties compared to the mono FRC under impact loading. Based on macro-experimentation and micro-observation, the impact behavior of the hybrid basalt-macro synthetic polypropylene FRC (BSFRC) was investigated by using ∅74 mm SHPB, SEM, and EDS. The effects of fiber hybridization, strain rate, and w/c ratio were analyzed simultaneously. The results show that the dynamic mechanical properties of BSFRC are strain-rate sensitive. Both basalt and macro synthetic polypropylene fibers (BF, SF) have a strengthening and toughening effect on concrete. Their hybridization has a similar enhancement effect but the impact toughness of concrete is further improved and the best hybrid ratio is 0.05%(BF)–0.25%(SF). BSFRC with higher w/c ratio has a higher strain rate effect while the fiber hybridization effect is weakened. Besides, the proposed constitutive model can well describe the impact behavior of BSFRC. The hydration of cement in the interface transition zones is lower with more Calcium Silicate Hydrate and less than that in the common mortar. However, the addition of BF and SF contributes to the hydration of cement and improves the performance of concrete eventually.

Mechanical and durability performance of 100% recycled aggregate concrete pavers made by compression casting

Effect of elevated temperature of hybrid fibres on the mechanical performance of cement mortar

The purpose of the work is the development of fiber-reinforced concrete compositions for rigid pavements with properties of high strength, frost resistance and wear resistance due to the use of polycarboxylate type superplasticizer and dispersed reinforcement. The experiments were conducted according to an optimal 3-factor 15-point plan. The following composition factors were varied: the amount of Portland cement CEM I 42.5 R (from 290 to 350 kg/m3); the amount of basalt fiber BAUCON®-bazalt (from 0.9 to 1.5 kg/m3); the amount of polycarboxylate superplasticizer STACHEMENT 2570/5/G (from 0.6 to 1 % by weight of cement). The workability of all developed mixtures was S1, which corresponded to a cone slump 2...3 cm. Research results shows when increasing the amount of cement and the amount of superplasticizer to 0.9 – 1.0 %, the W/C of the mixtures decreases. The amount of basalt fiber practically does not affect the W/C of the mixture. Due to increase in the amount of Portland cement, the strength of fiber-reinforced concrete is increases, as expected. With an increase in the amount of basalt fiber to 1.3 – 1.4 kg/m3, the tensile strength in bending of concrete increases by 12 – 21 %, while the compressive strength changes insignificantly. Fiber concrete with a superplasticizer content of about 0.9 % has the highest compressive and tensile strength in bending. Moreover, due to increase in the amount of Portland cement from 290 to 350 kg/m3, the frost resistance of concrete increases to about 100 cycles. Due to the increase in strength of that composition, the wear resistance of concrete was increased. With an increase in the amount of basalt fiber from 0.9 to 1.3 – 1.4 kg/m3, the wear resistance of concrete increases by 11 – 16 %, and frost resistance increases to approximately 50 cycles. The change in the amount of superplasticizer has little effect on the wear resistance of concrete. However, with an increase in the amount of additive STACHEMENT 2570/5/G from 0.6 to 0.9 % by weight of cement, the frost resistance of fiber-reinforced concrete increases to about 50 cycles. Fiber concretes with a rational amount of dispersed reinforcement (1.3 – 1.4 kg/m3) and superplasticizer (0.9 %), depending on the amount of cement, have compressive strength from 43 to 60 MPa; tensile strength in bending from 4.9 to 6.4 MPa; wear resistance from 0.31 to 0.37 g/cm2 and frost resistance from F200 to F300. This ensures the high durability of the developed fiber-reinforced concrete for rigid pavements.

Despite the many benefits of using basalt fibre in plane concrete, there has only been a limited number of research found in the literature concerning basalt fibre reinforced concrete pavements. Hence, the aim of this research study was to evaluate the effect of basalt fibres in improving the mechanical properties of plain concrete pavements. In this regard, flexural, split tensile, compressive and durability tests were conducted to examine the role of these fibres. The experiments were conducted at two fibre lengths (12 and 24 mm), three fibre dosages (4, 8 and 12 kg/m3), two aggregate gradations and two mix designs. Test results showed that using the basalt fibre in Portland cement specimens increases the compressive strength between 4.3% and 9.4%. However, the effect of this fibre on the mechanical properties of Portland cement concrete completely depends on the length and weight of the fibre and aggregate gradation. Overall, basalt fibre can lead to adverse effects or in the best condition a small improvement in split tensile and compression strength. The greatest effect of this fibre is increasing the concrete flexural strength up to 20%. Also, these fibres do not play an effective role in decreasing the effect of chlorine ion (or chloride) on cement concrete.

Experimental study on the mechanical properties and microstructure of chopped basalt fibre reinforced concrete

After high-temperature exposure, synthetic fibers with low melt temperature tend to exert negative influence on mechanical performance of engineered cementitious composite (ECC) and its elements. Basalt and PVA fiber reinforced hybrid-fiber ECC (basalt/PVA HF-ECC) is a promising way to address such drawback, due to the low cost, sustainability and high-temperature stability of basalt fiber. However, relevant researches only focus on fiber replacement and are still on primary stage, meanwhile their results show further performance improvements are required. In present study, basalt/PVA HF-ECC with superimposed basalt fiber content is proposed. Mechanical and micro-level related tests were conducted to investigate the effect of superimposed basalt fiber content after high-temperature exposure. Compressive test results showed basalt fiber could increase compressive strength at elevated temperatures. The optimal basalt fiber volume fraction was 0.8%, whereby compressive strength was higher than that of control PVA-ECC by 62.05%, 55.45% and 37.24% at 400 °C, 600 °C, and 800 °C. Tensile test results exhibited that stress-strain curves of basalt/PVA HF-ECC showed brittle behavior when PVA fiber melted at elevated temperatures, and first cracking strength also showed continuous increase as basalt fiber content increased. The optimal basalt fiber volume fraction was 1.2%, whereby first cracking strength was higher than that of control PVA-ECC by 48.43%, 42.38%, 36.30% and 50.41% at 23 °C, 400 °C, 600 °C, and 800 °C. Mercury intrusion porosimetry (MIP) tests showed basalt fiber reduced average pore diameter at elevated temperatures, while hardly exerted influence on porosity. At 600 °C and 800 °C, 0.8% and 1.2% content of basalt fiber decreased average pore diameter of control PVA-ECC by 13%–37%, and deduced peak heights of pore size distribution curves. SEM observation discussed and proved the basalt fiber contribution to strength improvement after high-temperature exposure. Rupture space related analysis was also used to discuss the tensile strain capacity deterioration at elevated temperatures. The present study investigates high-temperature mechanical performances and micro-level properties of basalt/PVA HF-ECC with superimposed basalt fiber content, thus promotes development of heat-resistant ECC with much reliable performances.

Hybrid fibre-reinforced concrete combines different types of fibres or fibres of varying lengths to maximize their individual advantages, which can potentially lead to a synergistic enhancement in overall performance. The main aim of this study is to explore the feasibility of integrating a hybrid fibre system to enhance the efficiency and properties of basalt fibre-reinforced concrete. Specifically, the research focuses on evaluating the mechanical characteristics of basalt hybrid fibre-reinforced concrete across two concrete grades: normal strength M30 and high strength M60. Basalt fibres of 12 mm and 30 mm lengths are used to hybridize the concrete, with a total fibre volume fraction of 1.5%. By incorporating both short and long basalt fibres into the concrete matrix, this study aims to assess how these variations impact essential properties such as workability, compressive strength, flexural strength, and Modulus of Elasticity (MOE). The hybrid mix, comprising 25% of 12 mm fibres and 75% of 30 mm fibres at a volume content of 1.5%, demonstrates enhanced mechanical properties across all concrete grades. The addition of basalt fibres, particularly those with higher proportions of longer fibres, results in a decrease in workability. Notably, hybridizing fibres have no discernible effect on compressive strength or MOE in both concrete grades. From the results it was observed that the flexural strength of the optimal hybrid mixes is significantly higher, surpassing conventional concrete by 39% and 54.35% for M30 and M60 grades of concrete, respectively.