Polyurethane Cement Research Articles

Mechanics and Durability of Polyurethane Cement Composite (PUC) Material

In order to investigate the mechanical properties of polyurethane cement (PUC) composite materials, axial tensile test, acid and alkali corrosion resistance test, bond test with concrete, and bond test with steel bars were conducted. The axial tensile results show that the tensile strength of PUC material is 31.11MPa, the stress-strain curve for axial tensile behavior of the material is obtained through fitting. To explore the durability of PUC materials, acid-alkali-salt corrosion resistance test is carried out, the results show that the PUC material has good resistance to acid and alkali corrosion. The failure mode of the bond test between PUC material and concrete is internal cohesion failure of concrete material, indicating good bond performance of PUC material. Axial tensile test of PUC material is carried out at different temperatures (-40℃~60℃). When subjected to temperatures between 40�C and 60�C, the strength of materials does not deteriorate. However, it is noteworthy that the material�s ability to withstand tensile strain significantly increases as temperatures rise to 60�C. The bonding strength between PUC material and steel bar increases with an increase in protective layer thickness, and at a thickness of 70 mm, the maximum bond stress is achieved at 16.38 MPa. On the other hand, the strength of the bond reduces as the anchorage length increases. Smooth round bars demonstrate a significantly lower bond strength compared to deformed bars, as their maximum bond strength is at approximately 47.4% of that of the deformed bars under the same conditions.

Investigating the Flexural Properties of Reinforced Concrete T-Beams Strengthened with High-Strength Steel Wire Mesh and Polyurethane Cement

Investigating the Flexural Properties of Reinforced Concrete T-Beams Strengthened with High-Strength Steel Wire Mesh and Polyurethane Cement

Seismic Performance Analysis of Concrete Columns Reinforced with Prestressed Wire Ropes Embedded in Polyurethane Cement Composites

In order to improve the seismic performance of reinforced concrete (RC) columns, a reinforcement technology using prestressed steel wire ropes embedded in polyurethane cement composite material is proposed. Four concrete columns reinforced with different materials were subjected to a combination of axial compression and horizontally repeated loading tests (one of which was not reinforced, while the remaining three were reinforced with prestressed steel wire rope, polyurethane cement composite material, and prestressed steel wire ropes embedded in polyurethane cement composite material). The experimental results show that the ductility and energy dissipation capacity of reinforced concrete columns after reinforcement are significantly improved. After strengthening with prestressed steel wire ropes embedded in polyurethane cement composite material, the ultimate horizontal displacement and energy dissipation capacity of reinforced concrete columns were significantly improved, which were 69% and 3.2 times higher than those of unreinforced columns, respectively.

Experimental study of polyurethane cement composite–reinforced soft soil in the thawed layer in permafrost regions

Permafrost degradation induces a large number of thawed layers that have high water content, low bearing capacity, and high compressibility, which threaten the stability of infrastructure in permafrost regions. How to reinforce the soft layers of thawed permafrost is very essential for maintaining and repairing such infrastructure. This study investigates the reinforcement effect and mechanism of a polyurethane cement composite (PUC) on the soft soil in the thawed layer (SSTL) of permafrost through mechanical and microscopic tests. The experimental results indicate that the unconfined compressive strength (UCS) of the SSLT initially increases and then decreases with increasing hydrophilic polyurethane (WPU) content, while it increases with higher polymer cement content (PMC). The UCS of the SSLT reinforced with 10% WPU increases by 41.96% and 18.75% in the early and late stages, respectively, compared to a SSLT sample without added WPU at a moisture content of 40%, while the cohesion of the SSLT increases by 7.74%, and the internal friction angle increases by 29.48%. A microscopic analysis reveals that the PUC significantly enhances the microstructure of the SSLT through intricate physical and chemical reactions. PUC-reinforced SSLT provides a new way to address the settlement and deformation that adversely affect subgrade in permafrost regions.

Study on the Mechanical Properties of Polyurethane-Cement Mortar Containing Nanosilica: RSM and Machine Learning Approach

Polymer-modified cement mortar has been increasingly used as a runway/road pavement repair material due to its improved bending strength, bonding strength, and wear resistance. The flexural strength of polyurethane–cement mortar (PUCM) is critical in achieving a desirable maintenance effect. This study aims to evaluate and optimize the flexural strength of PUCM involving nano silica (NS) using a central composite design/response surface methodology (CCD/RSM) to design and establish statistical models. The PU binder and NS were utilized as input parameters to evaluate the responses, such as compressive and flexural strength. Moreover, machine learning (ML) algorithms including artificial neural networks (ANN) and Gaussian regression process (GPR) were used. The PUCM mixtures were prepared by adding a PU binder at 0%, 10%, 15%, and 25% by weight of cement. At the same time, NS was incorporated into the mortar mixes at 0 to 3% (interval of 1%) by cement weight. The results showed that the simultaneous effect of PU binder at the optimal content and NS improved the performance of PUCM. Adding NS to the mortar mixture mitigated some of the strength lost due to the PU binder, which remarkably reduces the strength properties at a high content. The optimized PUCM can be obtained by partly adding 3.5% PU binder and 2.93% NS particles by the weight of cement. The performance of the machine learning algorithms was tested using performance indicators such as the determination of coefficient (R2), mean absolute error (MAE), mean-square error (MSE), and root-mean-square error (RMSE). The GPR algorithm outperformed the ANN with higher R2 and lower MAE values in the training and testing phases. The GPR can predict flexural strength with 90% accuracy, while ANN can predict it with 75% accuracy.

Static Load Test Analysis of T-Beam Bridge Shear Strengthening by Prestressed Steel Wire Rope Embedded in Polyurethane Cement (PSWR-PUC)

Many bridges suffer from aging and deterioration problems and need to be strengthened. PSWR-PUC is an emerging structural strengthening technology that enhances the load-bearing capacity of concrete bridges by embedding prestressed steel wire ropes into polyurethane cement. This paper focuses on investigating the shear reinforcement effectiveness of PSWR-PUC. Firstly, the composition of PSWR-PUC is introduced. Subsequently, two T-beam bridges in similar service condition are selected, and shear strengthening schemes involving PSWR-PUC and externally bonded steel plates are devised. Lastly, static loading tests are conducted, and the deflection and strain data of the two bridges before and after reinforcement intervention are analyzed. The results indicate that both strengthening methods improve the bridge load-carrying capacity. However, compared to the bridge strengthened with the externally bonded steel plate method, the deflections in the bridge strengthened with PSWR-PUC decreased by 36.8% and 42.1%, the strains decreased by 18% and 23%, and the shear stiffness was improved to a greater extent. These results verified that the PSWR-PUC strengthening method is effective for improving structural capacity and performance. This study will contribute to an in-depth understanding of the performance characteristics and application scope of PSWR-PUC shear strengthening technology, and it provides a scientific basis and guidance for practical engineering applications.

Experimental Study on Mechanical Properties of Polyurethane Cement Composite (PUC) Under Various Temperatures

This paper aims to investigate the mechanical properties of polyurethane cement (different ratios) at different ambient temperatures. The temperature and proportion which affect the constitutive relation of the material were analyzed by axial tensile test. The microstructure and failure mode of polyurethane cement were studied using scanning electron microscope technology. At -40oC ~40oC, the stress-strain curves of polyurethane cement with different proportions were roughly similar. When the temperature was higher than 40oC, with the rise of temperature, the ultimate tensile strength of polyurethane cement specimens would decrease but the ultimate strain would increase. When the temperature was lower than -40oC, with the decline of temperature, the ultimate strain and tensile strength of polyurethane cement specimens would decrease. The ultimate stress of polyurethane cement with different ratios was different. With the rise of the proportion of polyurethane components, the ultimate stress would increase but the elastic modulus would decrease. Macroscopically, the failure modes of polyurethane specimens were different with the change of temperature. Brittle fracture occurred at low temperatures. At high temperatures, the specimen did not fracture, but a large number of �V�shaped cracks appeared at the edge. The higher the temperature, the more obvious this phenomenon was. At the microscopic level, the fibers didn t break at high temperatures, and there were obvious cracks and more stubble on the surface of cracks at room temperature.

Experimental Study on the Bending Resistance of Hollow Slab Beams Strengthened with Prestressed Steel Strand Polyurethane Cement Composite

In order to explore the toughening performance and failure mechanism of hollow slab beams strengthened with prestressed steel strand polyurethane cement composite, three test beams (L1–L3) were strengthened and one test beam (L0) was used as a comparison. The influence of different tensile stresses of steel strand and fiber additions on the flexural bearing capacity of the hollow slab beams, was studied. The cracking characteristics, load deflection relationship, ductility and strain of each test beam were compared and analyzed. The test results showed that the toughened material was well bonded to the hollow slab beam and the steel strand, which effectively inhibited the development of cracks in the test beams. The flexural bearing capacity of the strengthened test beams was significantly improved. The use of prestressed steel strand polyurethane cement composite material effectively improved the flexural bearing capacity of the test beams, and this reinforcement process can be further extended to engineering applications.

INFLUENCE ANALYSIS OF NATURAL VIBRATION CHARACTERISTICS OF STEEL BOX GIRDER WITH SINGLE CABLE FACE AND LARGE CANTILEVER

In recent years, there have been cases of strengthening bridge structures with polyurethane cement mortar. To further explore the properties of polyurethane materials, the effects of emery, lime, quartz sand and cement on the mechanical properties of polyurethane powder composites are studied by three-point flexural test. In the flexural test, the polyurethane cement composite formed a control group by changing the content of polyester polyol. The flexural strength and ductility are improved to a certain extent due to the addition of polyester polyol.The average flexural strength of other polyurethane powder composites such as polyurethane emery test block is 45.1 MPa and the corresponding strain is 6203 με, the average flexural strength of polyurethane lime test block is 33.4 MPa and the corresponding strain is 6470 με, the average flexural strength of polyurethane quartz sand test block is 49.23 MPa and the corresponding strain is 7521 με. The results show that the flexural strength of polyurethane emery material and polyurethane quartz sand material is higher than that of polyurethane cement, which can be used to replace cement to a certain extent to reduce the cost of polyurethane composite material.

Research on Flexural Bearing Capacity of Reinforced Hollow Slab Beams Based on Polyurethane Composite Material Positive and Negative Pouring Method

In order to explore the construction technology of prestressed steel strand–polyurethane cement composites for strengthening hollow slab beams, two reinforced test beams (L1, L2) and one unreinforced test beam (L0) were subjected to flexural static load tests. The deflection, ductility, stiffness, strain, and bearing capacity of each test beam were used to summarize the influence of different reinforcement techniques on the flexural performance of hollow slab beams. Research shows the prestressed steel strand–polyurethane composite material was well-bonded to the hollow slab beam, which effectively inhibits the development of concrete cracks and delays the damage process of hollow slab beams, that the reinforcement effect of the test beam L1 under the reverse pouring process was remarkable, and the bending performance of the test beam L2 under the forward pouring process of the simulated real bridge was good, which was much better than that of the unreinforced beam L0. The use of tensile prestressed steel strands and forward casting of polyurethane–cement composite materials effectively improved the flexural bearing capacity of the test beams, and this reinforcement process can be further extended to engineering applications.

Experimental Study on Flexural Properties of Polyurethane–Cement Composites under Temperature Load

Polyurethane cement composite is a new organic–inorganic composite material with high strength, corrosion resistance, and fast curing. It is a complement and alternative to traditional cement materials. The flexural properties of polyurethane cement composites are the basic mechanical index of the material. In order to study the flexural properties under different temperature loads, a molecular model was established, the chemical reaction process of polyurethane cement and the temperature response mechanism was analyzed, and the preparation process of polyurethane cement was proposed. Then, bending tests were carried out in strain-controlled mode to obtain the specimens’ bending strength and stiffness modulus under different temperature loads. The test results showed that the tensile strength of polyurethane cement decreased first, then increased, and finally decreased with the increase in temperature, while the bending stiffness modulus decreased with the increase in temperature. Combined with the theoretical derivation, the damage mode of the samples under different temperature loads was analyzed, and the “L-type” damage strain curve was obtained. The results showed that the proposed theory could effectively explain the mechanism of action and flexural properties of polyurethane cement composites under temperature loading, which is a significant improvement to the application of polyurethane cement composites in practical engineering.

Enhanced damping properties of cement paste containing polyurethane and its improvement mechanism

Incorporating polyurethane (PU) in cement paste improved its energy dissipation and damping properties. The damping improvement mechanism of polyurethane cement paste (PUC) was the focus of this research. In the paper, the effects of PU (0%, 5%, 10%, 20%, 30%, and 40%) and w/c (0.35, 0.45, and 0.55) on the static mechanical and damping properties of PUC were investigated. Simultaneously, combining XRD, SEM, and MIP, the microscopic mechanism was also analyzed. The results showed that both the static mechanical strength and storage modulus of PUC were lower than that of the reference group, and the early compressive strength was greatly affected by PU. Meanwhile, the damping capacities of PUC was obviously superior to that of cement paste. Better damping performance was obtained with increasing PU content, while the change of w/c had relatively little effect on PUC. Damping properties of PUC were sensitive to temperature change, and less sensitive to frequency change. Microstructural analysis of PUC showed that no new hydration products were produced due to the addition of PU, but cement hydration was hindered. In addition, the porosity of PUC was significantly increased. All this led to a decrease in mechanical properties. Based on test results, the damping improvement mechanism of PUC was mainly related to the hysteresis effect of PU, porous structure and microstructures in the matrix.

Flexural strengthening of reinforced concrete T-beams using a composite of prestressed steel wire ropes embedded in polyurethane cement (PSWR-PUC): Theoretical analysis

A composite of prestressed steel wire ropes embedded in polyurethane cement (PSWR-PUC) is a new and efficient strengthening method. This paper mainly studies theoretical analysis of reinforced concrete (RC) T-beams strengthened with PSWR-PUC. First, the mechanical properties of the polyurethane cement (PUC) such as ultimate flexural strength and ultimate compressive strength were studied experimentally. Second, the calculation methods of cracking load and maximum bearing capacity were proposed. Third, degree of prestress, ratio of reinforcement and thickness of PUC responsible for the short-term cross-sectional stiffness were analyzed. Finally, calculation equations for predicting average crack spacing and maximum crack width were suggested. The results from using the proposed methods agree well with the experimental ones. Theoretical analysis and proposed calculation equations are feasible.

Repair of a single pier of a continuous-curved-beam bridge with polyurethane cement

Continuous-curved-beam (CCB) bridges are often used in earthquake-prone areas, but their design characteristics make it difficult to predict structural damage during an earthquake. A large-scale model of a CCB overpass that was damaged during the 2008 Wenchuan earthquake was created and tested on a shaking table. After one pier suffered seismic damage, it was reinforced using polyurethane cement (PUC) and retested. The results showed that the PUC repair improved the structural performance of the bridge. The use of PUC is thus a new and valid method for the quick repair of earthquake-damaged bridge piers.

Study on Toughening and Temperature Sensitivity of Polyurethane Cement (PUC).

Polyurethane cement (PUC) is now commonly used in the reinforcement of old bridges, which exhibit various issues such as poor toughness, temperature-sensitive mechanical properties, and brittle failure. These problems can lead to the failure of the reinforcement effect of the PUC on old bridges in certain operating environments, leading to the collapse of such reinforced bridges. In order to alleviate these shortcomings, in this study, the toughness of PUC is improved by adding polyvinyl alcohol (PVA) fiber, carbon fiber, and steel fiber. In addition, we study the change law of the flexural strength of PUC between −40 °C and +40 °C. The control parameters evaluated are fiber type, fiber volume ratio, and temperature. A series of flexural tests and scanning electron microscope (SEM) test results show that the flexural strength first increases and then decreases with the increase in the volume-doping ratio of the three fibers. The optimum volume-mixing ratios of polyvinyl alcohol (PVA) fiber, carbon fiber, and steel fiber are 0.3%, 0.04% and 1%, respectively. Excessive addition of fiber will affect the operability and will adversely affect the mechanical properties. The flexural strength of both fiber-reinforced and control samples decreases with increasing temperature. Using the flexural test results, a two-factor (fiber content, temperature) BP neural network flexural strength prediction model is established. It is verified that the model is effective and accurate, and the experimental value and the predicted value are in good agreement.

Self-Monitoring of Reinforced Concrete Beam Bending with Carbon Nanofiber Polyurethane Composite

To examine the intelligent sensing properties of polyurethane cement mixed with carbon nanofiber and used as beam reinforcement material, 7 reinforced concrete T-beams were made and reinforced with carbon nanofiber polyurethane cement material (CPUC). Four-point bending tests were conducted. Reinforcing concrete beams with CPUC material might increase the yield load and ultimate load of beams significantly. The overall stiffness of the reinforced beam was enhanced. CPUC played a significant inhibitory role in the formation and development of beam cracks. A sudden change in the rate of CPUC resistance can be used to monitor the yield of a steel bar, and then, a safety warning for the components can be launched. By establishing a model of the relationship between the resistance change rate and the external load, the bearing capacity of the beam is evaluated in real time, and the dual effects of reinforcement and health monitoring of the beam are realized simultaneously.

FLEXURAL SIMULATION ANALYSIS OF RC T-GIRDERS STRENGTHED WITH POLYURETHANE CEMENT-PRESTRESSED STEEL WIRE ROPES

To verify the effectiveness of polyurethane cement-prestressed steel wire ropes for flexural reinforcement of reinforced concrete T-girders, this paper conducts flexural test research on 12 pieces of T-girder specimens. Through the ABAQUS finite element program to build a model for numerical simulation, the results show polyurethane cement prestressed steel wire rope reinforcement can significantly increase the yield load and ultimate load of reinforced girders. Taking a girder in the test (20mm reinforcement thickness of polyurethane cement) as an example, yield load and ultimate load increased by 61.5% and 102.3% compared to unreinforced girder. The finite element model calculation results of T-girder bending reinforcement are in good agreement with the bending reinforcement test, and the error is only about 2%. For different strength concrete, the yield load increases slightly with the increase of concrete strength. For T-girders with different reinforcement ratios, the bearing capacity of strengthened girders changes significantly with the increase of longitudinal reinforcement ratio. The yield load of girders with reinforcement ratio of 1.82% and 1.35% is 29.84% and 65.85% higher than that of girders with reinforcement ratio of 0.91%. The yield deflection is 13.18% and 3.99% higher than that of girders with reinforcement ratio of 0.91%. It can be concluded that the bending reinforcement method of polyurethane cement prestressed steel wire ropes can effectively strengthen the main girder and ensure the structural safety.

EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF POLYURETHANE POWDER COMPOSITES

In this paper, the effects of emery, lime, quartz sand and cement on the mechanical properties of polyurethane powder composites were studied by three-point flexural test, and the stress-strain curve was drawn. In the flexural test, the polyurethane cement composite formed a control group by changing the content of polyester polyol. When polyester polyol: isocyanate: cement =1:1:2, the average flexural strength of polyurethane cement was 37.1 MPa, and the strain was 10854 με.When polyester polyol: isocyanate: cement =1.15:1:2, the average flexural strength is 38.9 MPa and the strain is 23520 με.When polyester polyol: isocyanate: cement =1.3:1:2, the average flexural strength is 42.5 MPa and the strain is 32942 με. The flexural strength and ductility are improved to a certain extent due to the addition of polyester polyol.The average flexural strength of other polyurethane powder composites such as polyurethane emery test block is 45.1 MPa and the strain is 6203 με, the average flexural strength of polyurethane lime test block is 33.4 MPa and the strain is 6470 με, the average flexural strength of polyurethane quartz sand test block is 49.23 MPa and the strain is 7521 με. The results show that the flexural strength of polyurethane emery material and polyurethane quartz sand material is higher than that of polyurethane cement, which can be used to replace cement to a certain extent to reduce the cost of polyurethane composite material.

Study on the mechanical behaviors and failure mechanism of polyurethane cement composites under uniaxial compression and tension

Study on the mechanical behaviors and failure mechanism of polyurethane cement composites under uniaxial compression and tension

Effect of binder-aggregate ratio on the mechanical and functional properties of porous polyurethane cement mixture

ABSTRACT Polyurethane mixtures are regarded as novel polymer pavement materials that can overcome the shortcomings of poor mechanical properties and loose particles of open-graded friction course (OGFC). Owing to its high strength after curing, polyurethane binder improves the mechanical connection at the aggregate-aggregate contact point, which effectively enhances the service performance of permeable pavement. However, the relationship between the binder content and the mechanical and functional properties of polyurethane mixture has not clearly understood yet. The objective of this study is to investigate the influence of the binder-aggregate ratio on the mechanical and functional properties using laboratory tests. Firstly, the effect of binder content on the mechanical properties of the mixture is examined by Marshall stability test, uniaxial compression test, and bending beam test. Secondly, the functional properties of the mixtures are characterised by Cantabro test, permeability test, computed tomography, and particle clogging test. Finally, the durability of the mixtures is characterised by hydrolysis resistance test and ultraviolet radiation degradation test. The results reveal that the content of binder has a significant impact on the mechanical and functional properties of the mixture. It is necessary to maintain a balance between the mechanical and functional properties.