Split Strength Research Articles

Bond performance between cementitious grout and normal concrete subjected to freeze–thaw damage

Owing to the increasing application of cementitious grout in strengthening projects in cold regions, the freeze–thaw durability of the bond between cementitious grout and concrete has attracted attention. This study investigates the bond performance of a cementitious grout–normal concrete interface after FTCs through splitting tensile and slant shear tests at different angles. The microstructure of the cementitious grout–concrete interface is observed via backscattered electron (BSE) microscopy. The results show that FTCs rapidly reduce the splitting bond strength and slant shear bond strength of the interface. After 240 FTCs, the splitting and slant shear bond strengths decrease by 40.7%–72.4% and 46.1%–57.3%, respectively. An increase in substrate strength significantly enhances the interfacial bond strength, particularly the slant shear bond strength. Freeze–thaw damage to the substrate reduces the interfacial bond strength and frost resistance. The slant shear strength increases significantly with the slant shear angle. The effects of FTCs on the interfacial shear strength parameters are reflected through a rapid decrease in cohesion, whereas the interface internal friction angle remains relatively unaffected. Empirical formulas for calculating the interface bond strength are obtained from experimental data and validated. The BSE images show that cracks begin to appear at the cementitious grout–normal concrete interface as the number of FTCs increases, thereby decreasing the interfacial bond strength.

Evaluation of the lightweight foamed concrete characteristics

The purpose of this paper is to assess the properties of light weight foamed concrete. In this research, two phases are investigated. The first stage explored the characteristics of fresh and hardened foamed concrete using a foaming agent. The following parameters were employed in this study: foaming agent used as a volume of concrete mix by 10, 20, and 40%, fly ash used as a replacement of cement content by 10, 25, and 50%, and polypropylene fiber used with varied volume fractions of 0.5, 0.75, and 1.0%. Slump values are applied to evaluate the fresh properties. To evaluate the hardened concrete, the dry density and compressive strength at 7 and 28 days are computed. Furthermore, the 28-day tensile splitting strength and flexural strength are studied. The effect of a high temperature was evaluated. The second stage investigated the effects of polypropylene fiber on both fresh and hardened concrete. It was observed that foaming agents improve fresh characteristics while decreasing compressive strengths and dry density. Furthermore, utilizing fly ash improves the characteristics of both fresh and hardened foamed concrete. The fiber reduces the fresh characteristics while enhancing the toughened properties. Because of its low density, foamed concrete is being used for structural applications because of this study. Such as those utilized for thermal insulation, acoustic impedance, and fire breaks. Also used to create road foundations for roads built on soft soil.

Research on Water Stability and Crack Resistance of Waste Cellulose Acetate–Reinforced Asphalt Mixtures Based on Response-Surface Methodology

The objective of this study was to explore the engineering application potential of waste cigarette butts and to investigate the effect of waste cellulose acetate (WCA) as reinforcement material on the performance of asphalt mixtures. A performance prediction model was also constructed to explore the optimal mixture preparation scheme. In this study, a scanning electron microscope (SEM) was used to visually characterize the surface morphology of WCA. The elemental composition of the cellulose surface was determined semiquantitatively using an energy dispersive spectrometer (EDS). The experimental design was carried out following the face-centered central composite design (FCCD) of the response-surface methodology (RSM), taking WCA shearing time, WCA content, and asphalt-aggregate ratio as variable factors, and the splitting strength (Rdry), freeze–thaw splitting strength (Rsaturated), and tensile strength ratio (TSR) of the mixtures as response variables. The software Design-Expert was adopted to construct and optimize the model under multiple responses. The road performance was verified by rutting test, low-temperature bending test, and water immersion Marshall test. The results showed that WCA is a kind of organic cellulose with a smooth surface and cloverlike cross section, which can significantly improve the mixture’s crack resistance and water stability. The performance prediction models all achieved a fit of 90% or higher. The best parameters recommended by Design-Expert were WCA content of 0.201%, WCA shearing time of 11.847 min, and asphalt-aggregate ratio of 5.683%, and the WCA-reinforced asphalt mixture Rdry, Rsaturated, and TSR values were 1.38 MPa, 1.24 MPa, and 89.86%, respectively, all of which were within the 95% prediction interval of the model predicted values. In addition, the road performance tests showed that WCA significantly improved the mixture’s flexural strength and water stability, but harmed the high-temperature rutting resistance. WCA has a significant reinforcing effect on asphalt mixture, which has a certain reference value for recycling waste cigarette butts and developing green road materials. In addition, the FCCD model has high accuracy and can effectively guide the road material preparation process.

Static, fatigue and hygroscopic performance of steel-reinforced resins under various temperatures

Resins are essential structural materials predominantly used in load-bearing connections such as adhesively bonded joints and resin-injected bolted connections. In an effort to improve the latter, a new injection material, Steel Reinforced Resin (SRR), has been developed, consisting of spherical steel particles embedded in a resin. SRR's applicability has been explored in injection bolts used in composite steel-to-concrete floor systems and as an injection material in Fibre Reinforced Polymer (FRP) sandwich web-core panels of highway bridges. While the short-term and creep performance of SRR has been researched, its fatigue behaviour remains unexplored. From joint-level cyclic experiments with SRR, it was observed that joint endurance is dominated by SRR's fatigue performance. There is currently no research on the influence of temperature on SRR's mechanical properties and moisture uptake. This paper fills this gap, by investigating the static and fatigue performance of epoxy, unsaturated polyester polyurethane hybrid (UPE + PU), and vinyl ester based SRRs under ambient and elevated temperatures. Water absorption assessments were conducted on the three resins with and without steel particles to evaluate their durability and corrosion resistance. The results show that temperature significantly impacts tensile stiffness, tensile splitting strength, and fatigue life. Epoxy based SRR endured 20 times more tensile splitting stress cycles to failure compared to the UPE + PU resin based SRR at the same stress range. However, after 200 days of water exposure at maximum temperature, the epoxy resin (with and without steel shot) exhibited a weight increase of 4.0% and 0.50% respectively, suggesting that despite its superior fatigue performance, it may not be suitable for SRR applications in high moisture environments. In contrast, UPE + PU resin and its corresponding SRR displayed substantially lower water absorption.

Effect of deicing agents on the performance of airport asphalt pavement

Deicing agents are widely used to remove ice and snow on airport pavement, ensuring air traffic operation and safety. However, excessive spraying may affect the performance of airport pavement. The effects of different chloride deicing agents on the performance of airport asphalt and mixture have been assessed by previous studies. The three deicing agents (NaCl, KHF-1A, and NW056) were selected. Conducting various tests to examine their influence on the performance of asphalt and asphalt mixture. The tests include the DSR test, BBR test, indirect tensile test, bending test of small beam, and freeze-thaw splitting test. The results indicate that the asphalt anti-rutting factor G*/sinδ varies by 25%–45%, the asphalt creep stiffness increases by 15%–50%, and the anti-fatigue factor (G* sinδ) increases by 10%–40% under the effect of the deicing agents. The splitting strength of the mixture decreases by 10%–40%, the bending stiffness modulus increases by 6%–20%, and the freeze-thaw splitting strength ratio does not change significantly under the effect of the deicing agents. NW056 deicing agent has minimal effect on the performance of airport pavement and has optimal performance. The replacement of traditional chloride deicing agents helps to prolong the service life of airport asphalt pavement.

Utilization of Ceramic Waste Material as Cement Substitution in Concrete

Researchers and engineers have been exploring alternative materials to partially substitute for cement in concrete to decrease carbon emissions and promote sustainability. Industrial pozzolanic waste is one such material that has gained attention as a potential substitute for cement. This research paper investigates the use of industrial pozzolanic waste materials, ceramic fine dust from the cyclones installed onto spray dryers in the process of manufacturing ceramic tiles, as a partial replacement for cement in concrete. Chemical analysis showed that ceramic dust could be used as pozzolana as ASTM C 618:2019. The study aims to evaluate the properties of fresh and hardened concrete; compressive strength; tensile splitting; and flexural strength of concrete mixtures. Additionally, specimens were subjected to durability performance: an acidic environment and water absorption tests. The cement was replaced in the concrete mix in proportions of 0, 5, 7, 10, 15, 20, and 30% by weight with a water-to-binder ratio of 0.45 at different curing periods. The results showed an increase in compressive strength of up to 10% replacement over time; fortunately, even with up to 30% replacement, it is still within the characteristic value of 30 MPa. The workability of the concrete decreases with replacement. The flexural tensile strength improved by 8% and the splitting strength by 5% with a replacement of 7% set against the control sample. The water absorption of concrete decreased by up to 10% replacement level, which was 15% less than that of the control mix. Concrete subjected to a 2% sulfuric acid solution (acid attack) revealed a loss in compressive strength when set against those not subjected to acid attacks. Based on the present research, ceramic dust as pozzolanic waste material can be used as a partial substitute for cement in the manufacture of good quality concrete under standard conditions.

Mechanical and durability properties of standard and high strength geopolymer concrete using particle packing theory

Aggregate packing significantly affects the characteristics of fresh and hardened concrete; aggregates having higher packing density (PD) improve these characteristics. There is a lack of research on how the PD affects the properties of geopolymer concrete (GPC). Hence, the present study includes the effect of the PD on the mechanical and durability properties of the standard and high-strength GPC. The study parameters are the binder content, the concentration of NaOH, and the fly ash to ground granulated blast furnace slag (GGBS) ratio. Six aggregate groups (like 12.5–10 mm, 10–4.75 mm, 4.75–2.36 mm, 2.36-1.18 mm, 1.18–0.6, and 0.6–0.15 mm) were investigated for the particle packing experiment, and the blended coarse:fine aggregate ratio of 55:45 which produced the highest packing density of 0.702, were used in the GPC mixes. A total of 120 cubes of size 100 mm, 30 cylinders of size 100 × 200 mm, and 30 prisms of size 100 × 100 × 500 mm were cast for 10 different mixes in the study. Sorptivity and water absorption are the tests performed for the durability studies. The result shows that GPC mixes with Particle packing theory significantly improved the compressive strength, and durability, and showed better workability. The workability of the GPC reduces by increasing the GGBS and concentration of the NaOH solution. As the GGBS proportion and the concentration of the NaOH solution increases, the concrete compressive, split, and flexural strength increases. As the binder content increases, the strength increases at first, then reduces. Increasing the GGBS content, binder content, and molarity of the NaOH accomplishes a reduction of the sorptivity coefficient and water absorption of the GPC.

Comparing Mechanical Characterization of Carbon, Kevlar, and Hybrid-Fiber-Reinforced Concrete under Quasistatic and Dynamic Loadings

Concrete is a brittle material due to its poor tensile strength; consequently, concrete tends to crack or peel under an applied external load. Previous studies have investigated the effect of incorporating fiber into concrete, which can improve its tensile strength. In this study, the static and dynamic mechanical characteristics of three types of fiber-reinforced concrete (FRC) were examined: carbon-fiber-reinforced concrete (CFRC); Kevlar-fiber-reinforced concrete (KFRC); and a combination of both, known as carbon/Kevlar-hybrid-fiber-reinforced concrete (HFRC). This study created concrete specimens by pneumatically dispersing carbon and Kevlar fibers and mixing them with cement to comprise 1% of the weight. The mixture was then combined with aggregates and water to form the concrete specimens. When compared with the benchmark concrete specimens, it was found that the compressive strength of the CFRC, KFRC, and HFRC specimens increased by about 19% to 50%, the bending strength increase by about 8% to 32%, and the splitting strength increased by about 4% to 36%. Specifically, the HFRC made with the 24 mm carbon and Kevlar fibers displayed the most significant mechanical strength in a static state. Furthermore, the HFRC showed superior resistance to impact compared to the benchmark concrete specimens across various impact energies, with the 24 mm carbon and Kevlar fiber HFRC showing the highest resistance. The inclusion of fibers in the split Hopkinson pressure bar (SHPB) test demonstrated a notable increase in the maximum strength, particularly in the case of the 12 mm carbon fiber combined with the 24 mm Kevlar fiber in the HFRC specimen.

Mechanical properties and multi-layer perceptron neural networks of polyacrylonitrile fiber reinforced concrete cured outdoors

The application range of polyacrylonitrile fiber (PANF) in concrete engineering in alpine regions was clarified by performing six sets of mechanical tests of PANF-reinforced concrete (PANFRC) by outdoor curing. The results show that PANF can enhance the performance of concrete mainly in terms of the tensile performance. The splitting strength and flexural strength increased by 15.69% and 8.54% after 150 days, and the dosage used in the alpine region should be controlled between 1.2–1.5 kg/m3. Finally, based on the experimental results, the multi-linear regression prediction model (MLR) and multi-layer perceptron neural networks model (MLP) were used to predict the compressive strength (fcu), splitting strength (fsp), flexural strength (fts), tensile–compression ratio (fsp/fcu), ratio of flexural strength to compressive strength (fts/fcu), and ratio of flexural strength to splitting strength (fts/fsp) of each group of PANFRC specimens. The prediction model was constructed based on the fiber content (W), curing age (D), dynamic elastic modulus (E), and surface rebound hardness (R). The results of the model test show that MLR and MLP are reasonable for predicting the mechanical properties of PANFRC, and the prediction error of the latter is smaller. Moreover, R has a strong dependence on the mechanical evaluation index, the sensitivity coefficient Qik is 0.37, PANF has the least influence, and Qik is only 0.16. This study has reference significance for the application of PANFRC in alpine regions and provides useful ideas for the efficient and intelligent development of the construction industry in alpine regions.

Experimental Study on the Dynamic Fracture Characteristics of Mortar-Rock Interface Zones with Different Interface Inclinations and Shapes.

There has been little research on the impact resistance of mortar-rock slope protection structures. To ensure that the mortar-rock interface has good adhesion properties under the action of impact loading, in this paper, based on fracture mechanics theory, a theoretical impact model was established for mortar-rock binary material. Dynamic fracture tests were carried out on mortar-rock interfaces using the split-Hopkinson pressure bar (SHPB) system. The Brazilian disc (CSTBD) specimen was prepared with one half in granite and the other half in mortar. The specimen used for the dynamic impact test was 48 mm in diameter and 25 mm thick. The effects caused by the change in interface inclination and interface shape on the dynamic fracture mode were discussed. The dynamic model parameters were obtained for different inclination angles and interfaces. The results show that both the interface inclination and interface shape have significant effects on the dynamic mechanical properties of the mortar-rock binary material. The fracture modes of the mortar-rock specimens can be classified into three types. When the interface inclination is 0°, the specimen shows shear damage with an interface fracture; when the interface inclination is in the range of 0-90°, the dynamic splitting strength of the mortar-rock material increases with increasing interface inclination, and the interface undergoes composite fracture; and when the interface inclination is 90°, the dynamic splitting strength of the specimen reaches its peak, and the interface undergoes tensile fracture. The mortar-rock interface damage follows the M-C criterion. The roughness of the interface shape has a large influence on the dynamic splitting strength of the specimens. The rougher the interface shape, the higher the interface cleavage strength and the higher the peak load that causes the material to damage. The results of this study can provide a reference for the design of mortar-rubble structures to meet the demand for impact resistance and have strong engineering application value.

Influence of glass powder silica fume and scrapped ceramic waste on the mechanical properties of concrete

Carbon dioxide emissions from cement manufacture have a substantial environmental effect. The massive energy usage in the cement manufacturing process is also an issue. India is dealing with a major energy problem. Cement prices are rising on a daily basis. Furthermore, the usage of waste for the disposal and recovery of natural concrete components might harm the environment. Using trash not only decreases cement production and hence energy consumption, but it also helps to safeguard the environment. The goal of this study is to investigate the characteristics of concrete utilizing silica fume as a partial substitute for cement and glass powder in lieu of fine aggregate. These waste materials were used to replace some of the cement in the concrete samples, and their compressive, flexural, and split tensile strengths were assessed. According to the results, the addition of glass powder and silica fume improves the mechanical qualities of the concrete, but the addition of discarded ceramic waste has the reverse impact. Furthermore, the combination of glass powder and silica fume outperformed each waste item alone. The trials were carried out using Concrete Mix M40, which had been modified by substituting 40% of the coarse aggregate with waste ceramic aggregate, 20% of the fine aggregate with glass powder, and 10% of the cement with silica fume cement. Following tests of the concrete's compressive, split, and flexural strengths at 7, 28, and 28 days, the appropriate replacement dose was considered. The load-bearing capability of the beams is approximately the same as that of conventional beams throughout the board for the 20% replacement levels applied. The research comes to the conclusion that natural coarse aggregate may be used in place of scrapped ceramic aggregates (SCA) in concrete. Other beam specimens and typical beam specimens (CM) deflected more with load than a beam specimen with 10% SF, 20% GP, and 10% SCA. Modern technology allows for the production of lightweight, high-strength concrete at a low cost. When compared to CA, SCA lowered aggregate weight.

Strength Properties of Polymer Reactive Powder Concrete with Waste Materials

Reactive powder concrete, or RPC, outperforms conventional or even high-performance concrete in terms of ultra-high strength and better durability. Several buildings were destroyed in Iraq, and recycling the garbage from these buildings can significantly help reduce waste and environmental pollution as well as serve as a source of aggregate for use in new construction. Reusing garbage and using sustainable building materials are now crucial environmental challenges, so this study aimed to replace the natural fine aggregate, NFA, used in preparations of polymer reactive powder concreter, "PRPC" with recycled aggregates, or RA, from crushed old concrete, COC, in order to make PRPC production more environmentally and sustainably friendly. In this study, RPC is modified by adding styrene butadiene rubber (SBR), a polymer, to the original mixture at a ratio of 13% by weight of cement. This study sought to determine the effect of using COC as recycled fine aggregate (RFA) on the compressive, splitting, and flexural strengths of PRPC. The main objective of this investigation is to study the effect of oil (water, new oil, and waste engine oil) on the compressive and tensile strengths of PRPC with COC and to compare the behavior with that of a control mix (PRPC with NFA). The mixtures were prepared using six different percentages of RFA, replacing 0, 20, 40, 60, 80, and 100% NfA. After 28 days, the six mixes were divided into three groups. The first was still being cured in water, W; the second in waste engine oil, WEO; and the third in kerosene oil, KO. The results showed that using COC as RFA in PRPC was viable, and according to this investigation, the mix with 40% COC replacement with NFA provides the highest values of compressive strength, tensile strength, and flexural strength before and after exposure to liquids (water, new oil, and waste engine oil). Doi: 10.28991/CEJ-2023-09-08-09 Full Text: PDF

Improving the dynamic splitting properties of engineered cementitious composites using hybrid synthetic polymer and recycled steel fibres

To improve the dynamic mechanical behaviour and make full use of recycled waste tyres, this study investigates the feasibleness of partial replacement of polyvinyl alcohol (PVA) fibres with recycled tyre steel (RTS) fibres in engineered cementitious composites (ECC). A series of laboratory tests were carried out to evaluate the workability, elastic modulus and uniaxial tensile behaviour, as well as the quasi-static and dynamic splitting tensile behaviour of ECC containing PVA and RTS fibres. The experimental results indicate that the replacement of 0.25% PVA fibres with RTS fibres results in a 0.85 MPa drop in tensile strength, while a nearly one-tenth increase in first-crack strength appears as the stronger RTS fibre-to-matrix bonding is effective in controlling the initiation of the first crack. Under dynamic loading, the mono PVA fibre reinforced ECC gradually loses the specimen integrity due to the rupture of PVA fibres at higher strain rates, while the bridging effect of RTS fibres contributes to maintaining the specimen integrity even at the highest measured strain rates of 7.3–7.5 s−1. Moreover, the replacement of 0.5% RTS fibres can lead to up to 15.54% and 27.38% increase in dynamic splitting strength and dissipation energy, respectively, relative to that with 2.0% PVA fibres. In addition, the evolution of dynamic increase factor with strain rate is modelled by theoretical equations considering the content and length-to-diameter ratio of fibres, the predictions of which match well with the experimental results.

Characterization of fiber reinforced self-compacting concrete by fly ash and cement

Self-compaction concrete is huge flow capable kind of concrete that flows through the appearance lacking of any shaking. Self-compacting concrete is a non-separating concrete those can be located by its own mass. It has fresh properties approximately passing capacity, flowing ability, filling ability and segregate resistance which can be estimated by conducting workability tests like L-Box, V-Funnel, U-Box, J-Ring and Slump cone flow. The characteristics of self-compacting concrete replacing by fly ash to improved the fresh state stability, rheological properties and compressive strength and steel fibers generating a highest compression and splitting tensile strengths in self-compaction concrete. The effects of fly ash as 5%, 10%, 15%, 20%, 25%, 30% weight of cement and of steel fibers as 0.5%, 1.0%, 1.5, 2% with taking of the highest (optimum) value of fly ash to get maximum strength. The strength characteristics like compression, split, tensile and flexural strengths. And longevity (durability) properties like sorpitivity, rapid chloride permeability test (RCPT) of self-compacting concrete.

The Influence of Fiber on the Mechanical Properties of Controllable Low-Strength Materials.

Numerous studies have been conducted on fiber-reinforced concrete; however, comparative investigations specifically focusing on the utilization of fibers in CLSM remain limited. In this study, we conducted a systematic investigation into the mechanical properties of controlled low-strength material (CLSM) by manipulating the length and doping amount of fibers as control variables. The 7-day compressive strength (7d-UCS), 28-day compressive strength (28d-UCS), and 28-day splitting strength of CLSM were employed as indicators to evaluate the material's performance. Based on our comprehensive analysis, the following conclusions were drawn: (1) A positive correlation was observed between fiber length and material strength within the range of 0-6 mm, while conversely, a negative correlation was evident. Similarly, when the fiber doping was within the range of 0-0.3%, a positive correlation was identified between material strength and fiber doping. However, the strength of CLSM decreased when fiber doping exceeded 0.3%. (2) SEM and PCAS analyses provided further confirmation that the incorporation of fibers effectively reduced the porosity of the material by filling internal pores and interacting with hydration products, thereby forming a mesh structure. Overall, this study offers valuable insights into the manipulation of fiber length and doping amount to optimize the mechanical properties of CLSM. The findings have important implications for the practical application of CLSM, particularly in terms of enhancing its strength through fiber incorporation.

Engineering properties and air void characteristics of cold recycled mixtures with different compaction methods

Cold recycled mixtures (CRM) offer advantages in terms of resource conservation and reduced CO2 emissions. This paper utilizes the vertical vibration testing method (VVTM), Marshall compaction (MC), Superpave Gyratory Compactor (SGC), and field core samples to analyze the effects of different compaction methods on the engineering properties of CRM. The study begins by discussing the volumetric and mechanical parameters of CRM with different compaction methods, followed by an analysis of fatigue performance. Additionally, CT scanning technology is used to study the effect of different compaction methods on the void characteristics of CRM. The results demonstrate that VVTM specimens offer better mechanical properties compared to MC and SGC specimens. Furthermore, the RT (splitting tensile strength), MS (dry-wet tensile strength ratio), and TSR (freeze-thaw splitting strength ratio) of VVTM specimens exhibit the highest correlation with field core samples, reaching 97%, 97%, and 95%, respectively. The VVTM specimens also exhibit the biggest fatigue, which is similar to that of the field core sample. The Weibull distribution model is utilized to predict the fatigue life of CRM with different compaction methods, with the fatigue equation indicating that VVTM specimens have better fatigue performance. In addition, the number of voids, diameter of voids, and fractal dimension of VVTM specimens along the longitudinal direction are closer to those of field cores. The fractal dimension of CRM specimens with different compaction methods is between 1.2 and 1.4, indicating that the complex shape of voids may alter stress concentration and impact the performance of CRM.

A new experimental method to measure and calculate the tensile strength of concrete

Introduction: A new method is introduced to test the tensile strength of concrete: the cylinder transverse splitting test. Compared with the cylinder splitting (or Brazilian) test, the cylinder transverse splitting test involves different load positions and offers the advantages of doubling the data volume with the same number of specimens and improving the detection accuracy.Methods: Finite element analysis software was used to simulate the concrete cylinder transverse splitting test and the stress distribution on the failure surface was determined.Results and Discussion: The results show that the fracture of a cylinder is mainly determined by tensile stress. The splitting strength of normal concrete and crumb rubber concrete, a new environmentally friendly concrete material that has gathered considerable attention in recent years, was obtained by cylinder transverse and cube splitting tests. The cylinder transverse splitting test data show a stable correlation with the cube splitting test data and well characterize the concrete strength. The relationship between the cylinder nominal transverse splitting strength (f2) and cube splitting strength (f1) was established on the basis of linear analysis of the test data: f1 = 0.51f2. The calculated cube splitting strength is in good agreement with the test values.

Multiscale study of the road performance of cement and fly ash stabilized aeolian sand gravel base

To alleviate the scarcity of road construction materials in desert areas, the feasibility of 100% replacement of fine aggregates by aeolian sand for semirigid base pavement was studied. First, complete the design of the proportion of cement, fly ash, aeolian sand and gravel was completed by orthogonal testing. Second, based on mechanical property tests, compressive strength and splitting strength of each mix proportion were investigated at the maintenance ages of 7 d and 28 d. The resistance to sulfate erosion and water stability of each mix proportion were investigated at different ages with durability tests. Moreover, the strength development and deterioration mechanism of aeolian sand mixtures were analysed by SEM and EDS test systems. The results show that the increasein aeolian sand content significantly degrades the strength of the road performance of cement and fly ash stabilized aeolian sand gravel base; the 7 d unconfined compressive strength was 2.8 MPa, and splitting strength was 0.61 MPa when the aeolian sand content was 66%. The erosion products and hydration products of the binding material during the dry and wet cycles of the specimens under different ages filled the voids between the aggregates which improved the structural density, increasing the water stability coefficient and sulfate erosion resistance coefficient more than 95%. The complete replacement of fine aggregate by aeolian sand for semi-rigid type bases meets the design requirements of highway roadbases, which shows that the replacement of fine aggregate by 100% aeolian sand for a semirigid base was feasible.

Mechanical damage characteristics of CR/PPA composite modified asphalt pavement under multi-factor coupling effect in the seasonally frozen region

Asphalt pavements are inevitably affected by coupled effects of dry-wet/freeze-thaw cycles, UV radiation, temperature, and loading during service, resulting in degradation of their road performance and reduced service life. Therefore, this study used crumb rubber (CR) and polyphosphoric acid (PPA) as modifiers to prepare CR/PPA composite modified asphalt mixtures for testing. To investigate the mechanical properties of the composite modified asphalt mixtures under the action of multi-factor coupling. Meanwhile, the performance analysis of matrix asphalt and SBS modified asphalt mixtures were carried out as a comparison. Density and water penetration tests, splitting tests, beam bending tests, and four-point bending fatigue tests reveal the evolution of asphalt mixture road performance. Finally, regression fitting was performed on the test data to establish the mechanical damage model of each type of asphalt mixture. The results show that with the increase of wet-dry/freeze-thaw cycles and the increase of UV radiation time, the void ratio and water permeability coefficient increase and the splitting strength, bending and tensile strain, and fatigue life decrease for all types of asphalt mixtures. When the number of wet-dry/freeze-thaw cycles reached 8, the mechanical properties of the asphalt mixture decreased significantly, while the changes leveled off after the number of cycles reached 15. When the UV radiation time is less than 4 months, the mechanical properties of the asphalt mixture decay more slowly. However, with a further increase in radiation time, the mechanical properties decay rapidly. The water-saturated specimens have a more significant effect on the mechanical damage of each type of asphalt mixture. Compared with the other two mixtures, the composite modified asphalt mixtures have superior mechanical properties and fatigue life. The mixture performance damage model based on the least squares Levenberg-Marquardt method (L-M method) was able to simulate the experimental data well, with a minimum correlation coefficient R2 of 0.9285. In summary, the road performance of all types of asphalt mixtures under the coupling of multiple factors has deteriorated, while the composite modified asphalt mixtures have better anti-damage characteristics, with good prospects for promotion.

Effects on jute fiber and ferrochrome slag as coarse aggregate on mechanical properties of reinforced concrete

The present research work aims to produce by adding jute fiber (JF) with ferrochrome slag (FSA) as coarse aggregate. The experimental results of all the properties of jute fiber with ferrochrome slag (FSA) based concrete are compared to controlled concrete and efficient, technically acceptable and environmentally compatible construction material. From compressive strength, flexural strength and split tensile test results, it is observed that ferrochrome slag -based concrete samples' incorporation of jute fiber shows better performance than that of controlled concrete. Further, non -destructive tests and co-relation between compressive strength with split tensile strength and flexural strength are performed. This study focuses on the reuse of waste ferrochrome slag as a partial replacement for coarse aggregate in the production of cement concrete with improved mechanical properties and non-destructive tests. Ferrochrome slag was replaced by coarse aggregate with various percentages ranging from 0%, 50% and 100% by adding 0.10%, 0.20% and 0.30% JF (by weight). The workability test was performed to evaluate the concrete behaviour in a fresh state. The result shows that adding the percentages of jute fiber up to 0.10% shows 4.83%, 3.2% and 3.4% more compressive, split and flexural strength than the control concrete.