Aggregate Binder Ratio Research Articles

Design and evaluation of semi self-compacting cold mix polyurethane mixture for steel bridge deck pavement

To enhance the environmental sustainability and pavement performance of steel bridge deck paving, a novel semi self-compacting cold mix polyurethane mixture (CMPU-10) for steel bridge deck paving was specifically designed and evaluated. Herein, this study presents the first comprehensive documentation of the research process involved in the mix design of CMPU-10. Initially, based on the theory of maximum density curve, a gradation with a Talbot index (n) of 0.40 was identified as the preliminary gradation for designing CMPU-10 by void ratio, compressive strength and slump tests. Subsequently, the aggregate grade-by-grade filling test revealed the critical influence of sieve sizes (0.075 mm, 0.6 mm, and 2.36 mm) on the mixture dense degree. From these findings, an in-depth analysis of the effects of aggregate passage under the key sieve on the degree of mixture density, compressive strengths, and flow properties led to the determination of the gradation range of CMPU-10. The optimum binder-aggregate ratio for the median gradation was determined to be 9.2%. Finally, wheel tracking, semi-circular bending (SCB) and freeze-thaw splitting tests showed that the designed CMPU-10 exhibits superior high-temperature stability performance, low-temperature cracking resistance and moisture susceptibility compared to the TAF epoxy asphalt mixture (EA-10). This paper not only provides a new potential low-carbon material for steel bridge deck paving projects, but also establishes a theoretical foundation for the optimization design and promotion polyurethane mixture.

Research on the ratio of similar materials in water-absorbent mudstone based on fuzzy mathematics.

To determine the suitability and credibility of similar water-absorbent mudstone materials in model experiments, the prototype mudstone parameter similarity index was determined based on the similarity theory. Similar materials use cement and Plaster as binders and quartz sand as aggregate. The sensitivity of similar indicators of similar materials to control factors was analyzed through range statistics. Multiple regression analysis was used to establish the quantitative relationship between each control factor and similar indicators. Finally, the optimal matching scheme was refined through the combination of fuzzy mathematics and analytic hierarchy process. The results show that the physical and mechanical property indicators of similar materials with different proportions have a wide distribution range, and under certain similar conditions, they can meet the requirements of rock model tests with different properties. The aggregate-binder ratio is a direct indicator of material density, elastic modulus, and compressive strength. The main controlling factors, material density, elastic modulus, and compressive strength all increase with the decrease in aggregate-binder ratio. The cement-plaster ratio is the main control factor of material water absorption, and the water absorption gradually decreases with the increase of the cement-plaster ratio. The formula obtained through linear analysis can better represent the changing trend and distribution characteristics of various parameters of similar materials with the aggregate-binder ratio and cement-plaster ratio, and initially optimize the proportioning scheme of similar materials. Use fuzzy mathematics to evaluate the membership degree of each parameter index of similar materials, and the optimal ratio scheme was further determined to improve the credibility of later model experiments.

Optimizing geopolymer mortar for shotcrete applications by focusing on flowability and early-age mechanical characteristics

To facilitate the use of geopolymer materials in shotcrete applications, this study presents the development of a geopolymer mortar and explores its flowability and early-stage mechanical properties. Firstly, 15 groups of geopolymer mortar specimens with 3 liquid-binder ratios (0.70, 0.75 and 0.80) and 5 binder-aggregate ratios (0.225, 0.250, 0.275, 0.300 and 0.325) were developed. Secondly, the P-wave velocity, slump, early-age compressive strength and compressive strength were obtained by ultrasonic pulse velocity test, slump test and uniaxial compressive test. Thirdly, discussion on the effect of liquid-binder ratio and binder-aggregate ratio on P-wave velocity, flowability, compressive strength and early-age compressive strength of geopolymer mortar were carried out. Finally, an optimal mix proportions rang of geopolymer mortar materials that meet the requirements of wet shotcrete technology were proposed. The results show that P-wave velocity, slump, early-age compressive strength and compressive strength increase as the increasing of liquid-binder ratio. The slump, compressive strength and P-wave increase as the increasing of binder-aggregate ratio. Moreover, the optimal binder-aggregate ratios were proposed as 0.244 - 0.321, 0.228 - 0.298, and 0.209 - 0.241 for geopolymer mortar with a liquid-binder ratio of 0.70, 0.75 and 0.80, respectively. Geopolymer mortar in these mix proportions achieves compressive strengths ranging from 28.4 MPa to 41.1 MPa after curing for 1 day and 44.2 MPa to 55.4 MPa after curing for 28 days. The mix proportion of geopolymer mortar proposed in this paper can simultaneously meet the standard requirements for mechanical properties and flowability, demonstrating potential for wet shotcrete applications.

Optimization of mix proportion and strength prediction of magnesium phosphate cement-based composites based on machine learning

In order to optimize the mix ratio design of magnesium phosphate cementitious composites (MPCC) to obtain excellent workability and strength, this study investigated the effects of MgO-phosphate ratio, water-binder ratio, aggregate-binder ratio, the mass ratio of coarse and fine aggregates, mineral admixture content and steel fiber content on the flowability, setting time and cubic compressive strength (CCS) of MPCC using orthogonal design of experiments with a total of 32 sets of mix ratios. The experimental results were also analyzed utilizing range and variance analysis to determine the main influencing parameters and the optimal dosage of each factor, and the optimal MPCC mix ratio was obtained. In addition, the prediction of CCS for MPCC using five machine learning models was first introduced, and the predicted results were interpreted and analyzed regarding the SHAP (Shapley Additive exPlanations) features importance. The results showed that the effect of steel fiber volume content and water-binder ratio on the flowability was significant, and M/P significantly affected the setting time of MPCC. The CCS of MPCC increased with the age of curing, and MPCC exhibited high early strength, with 1-day CCS accounting for 55%～85% of the 28-day CCS. The effect of M/P on the 1-day, 3-day and 28-day CCS was highly significant, with M/P contribution rate as high as 76.3%, 80.3% and 83.6% of the CCS at 1, 3 and 28 days, respectively. Besides, the effect of steel fiber volume content on 28-day CCS was also significant. In summary, the optimal mix ratio of MPCC was A4B1C4D1E4F4G1 (M/P = 3, w/b=0.11, a/b=1.4, c/f=3, FA content =15%, MK content= 15%, steel fiber volume content= 0%). Furthermore, random forest (RF) and particle swarm optimization of back propagation artificial neural network (PSO-BP-ANN) models have a higher prediction accuracy, and the results of SHAP feature significance further confirmed the above test results.

Preparation and Performance Investigation of Epoxy Resin-Based Permeable Concrete Containing Ceramsite.

Permeable concrete is an innovative type of concrete that provides a sustainable solution for stormwater management by allowing water to seep through and be filtered naturally. This study focuses on the preparation and performance investigation of an epoxy resin-based permeable concrete containing ceramsite. In this study, ceramsite, a lightweight aggregate, is used as a substitute for conventional aggregates in the concrete mixture. The epoxy resin is then added to improve the strength and durability of the concrete. A series of tests, including compressive strength, water permeability, and freeze-thaw resistance tests, are conducted to evaluate the performance of the epoxy resin-based permeable concrete. The results show that with an increasing epoxy resin binder-aggregate ratio, the compressive strength of the epoxy resin-based permeable concrete significantly increases while the permeability coefficient decreases. Different types of aggregates have varying effects on the compressive strength and permeability coefficient of epoxy resin-based permeable concrete, with high-strength clay ceramsite providing the highest compressive strength and lightweight ceramsite having the highest permeability coefficient. In addition, the discrete element simulation method effectively and feasibly determines the ultimate load and accurately simulates the compressive strength of the permeable cement-based mixture, consistent with the measured compressive strength. A quadratic polynomial regression analysis yielded an R2 value of around 0.93, showing a strong relationship between durability and freeze-thaw cycles. The findings contribute to the development of sustainable construction materials for stormwater management and offer potential applications in various infrastructure projects.

Study on Proportioning Scheme of Coal System Rocky Similar Material Based on Orthogonal Test.

Similar materials play an important role in model testing. In order to meet the demand for similar materials in modeling tests, such as those on coal mining, coal system rocky similar materials were formulated using yellow sand as a coarse aggregate, heavy calcium carbonate as a fine aggregate, and cement and gypsum as binders. Based on the orthogonal experimental design method, four influencing factors, namely the aggregate-binder ratio, heavy calcium carbonate content, cement-gypsum ratio, and moisture content, were selected. Each factor was designed at five levels. Through weighing, uniaxial compression, Brazilian splitting, and variable-angle plate shear tests on 225 specimens under 25 different ratios, five physico-mechanical property indicators of the material, including density, compressive strength, tensile strength, cohesion, and internal friction angle, were obtained under different ratios. The test results indicate that the similar materials formulated with the above raw materials had a wide range of mechanical properties, which met the simulation needs of different types of coal rocks, such as main coking coal, anthracite, shale, etc., in the similar model test. Range analysis was adopted to analyze the sensitivities to each factor, which showed that the density and internal friction angle of similar materials are mainly controlled by the aggregate-binder ratio; the cement-gypsum ratio mainly controls the compressive strength, tensile strength, and cohesion of the material. Analysis of variance (ANOVA) was adopted to analyze the sensitivities to each factor, which showed that the aggregate-binder ratio had a highly significant effect on the density of the material, the cement-gypsum ratio had a highly significant effect on the compressive and tensile strength of the material, the cement-gypsum ratio had a significant effect on the cohesion and density of the material, and the moisture content had a significant effect on the compressive strength of the material. The remaining factors did not significantly affect the material parameters. The results of this study can provide some reference for the selection of coal system rocky similar materials in subsequent physical modeling tests.

Preparation of polyurethane concrete and its novel application in bridge expansion joint anchorage zone

The frequent damage and repair of bridge expansion joint anchorage zone has caused a great burden to the bridge maintenance work. The objective of this study is to prepare a steel fiber reinforced polyurethane concrete (SFPUC) with balanced multi-properties of workability, compressive strength, and flexural strength for the application in bridge expansion joint anchorage zone. A four-factor, five-level orthogonal experimental design was carried out to investigate the effects of the binder-aggregate ratio ( BA), cement content ( C), fine-coarse aggregate ratio ( FC), and steel fiber dosing ( SF) on the workability, compressive strength, and flexural strength, respectively. The multi-criteria decision-making (MCDM) method was used to transform the multi-response problem in the orthogonal experimental design into a single-response problem. Finally, a real engineering application and a finite element method were used to verify the feasibility of SFPUC for the expansion joint anchorage zone. The results show that the optimum proportion of SFPUC is BA (25%), C (20%), FC (20%), and SF (2.5%). The maximum principal stress in SFPUC anchorage zone is less than that in C50 steel fiber concrete anchorage zone under the same load. SFPUC is a highly promising material for bridge expansion joint anchorage zone repair.

Mechanical properties and microstructure of red mud-coal metakaolin geopolymer concrete based on orthogonal tests

Red mud, an industrial solid waste, can be used as a raw material for geopolymer concrete to reduce its environmental damage and achieve resource utilization. Nonetheless, the performance of red mud-based geopolymer concrete is influenced by various factors, and its overall sustainability remains to be comprehensively evaluated, limiting its widespread application. For this reason, this study systematically investigated the effects of water-binder ratio, aggregate-binder ratio, curing conditions, and Na2O/H2O on the water absorption, mechanical properties, and efflorescence degree of geopolymer concrete using Taguchi's orthogonal method. The optimal mixture for maximization of mechanical properties was determined using Design-Expert software. Subsequently, the microscopic properties of the samples were evaluated. In addition, an AHP-CRITIC-TOPSIS model was used to construct a sustainable assessment framework for geopolymer concrete including environmental, social, and economic indicators. The results indicated that the water-binder ratio is the main influencing factor. Excessive water increases the length of interfacial transition zone, coarsens the pore structure, and hinders the condensation process, leading to a degradation of material properties. In terms of sustainability, both M30 and M40 grade geopolymer concretes obtained significantly higher scores than cement concrete, and therefore it is considered a greener alternative.

Analysis of Mechanical Properties and Pore Structure of Mortar Prepared from Municipal Solid Waste Incineration Slag

Abstract The disposal of a large amount of bottom ash generated from the incineration of municipal solid waste has become the focus of research in solid waste and environmentalism. Using municipal solid waste incineration bottom ash (MSWI BA) to prepare mortar can not only solve the problem of insufficient natural river sand resources, but also play a role in treating a large amount of MSWI BA to alleviate urban pressures. In this study, macroscopic properties of mortar were systematically investigated by rheological, mechanical, and drying shrinkage tests, and the influence of MSWI BA on the internal pore structure and interfacial transition zone of mortar has been analyzed by mercury intrusion porosimetry (MIP), scanning electron microscope (SEM) and back scattered electron imaging (BSE). The results show that the rheological model of fresh mortar mixed with MSWI BA as fine aggregate is more consistent with the modified Bingham model, and its plastic viscosity decreases and then increases with the increase of MSWI BA, while the yield stress shows an increasing trend. The compressive strength and splitting tensile strength of mortar decrease with the increase of MSWI BA; the smaller the water-cement ratio and aggregate-binder ratio, the greater the strength loss. The incorporation of MSWI BA improves the flexural strength and compression-flexure ratio of M5/M10 mortar, and the splitting tensile strength of M5 mortar at 28 days is increased by 30 % with 20 % MSWI BA. Additionally, the incorporation of MSWI BA reduces the drying shrinkage properties of mortar and improves the volume stability. At the same time, it increases the number of pores above 50 nm inside the mortar and the content of ettringite at the interface.

Influence of Calcined Clay Pozzolan and Aggregate Size on the Mechanical and Durability Properties of Pervious Concrete

Pervious concrete has been reported as a viable solution to reduce stormwater run-off, the heat-island effect, road noise, and pavement flooding. Previous researchers have focused on analysing the structural properties and functionality of pervious concrete. However, relatively few studies have been conducted into the addition of supplementary cementitious materials (SCMs), such as calcined clay, in pervious concrete and its effect on long-term durability. This paper has studied the effect of calcined clay pozzolan as a partial substitute for Portland cement in pervious concrete, together with the influence of coarse aggregate size. A water–binder ratio of 0.4 and aggregate–binder ratio of 4.0, as well as a superplasticiser content of 0.95%, were maintained for all mixes. Two sizes of coarse aggregates were used for this study: 9.5 mm and 20 mm. CEM-I cement was partly substituted with calcined clay in dosages of 0 to 30% in replacement intervals of 5%. The mechanical tests conducted included the split tensile test, compressive strength test, and flexural strength test. Durability measurements such as the rapid chloride permeability test (RCPT), thermal conductivity and sulphate resistance tests were also carried out. The mechanical properties of the pervious concrete followed a similar trend. The results showed that at 20% replacement with calcined clay, the compressive strength increased by 12.7% and 16% for 9.5 mm and 20 mm aggregates, respectively. The flexural strength improved by 13.5% and 11.5%, whereas the splitting tensile strength increased by 35.4% and 35.7%, respectively, as compared to the reference concrete. Beyond 20% replacement, the tested strengths declined. The optimum calcined clay replacement was found to be 20% by weight. Generally, pervious concrete prepared with 9.5 mm obtained improved mechanical and durability properties, as compared to those of 20 mm aggregates.

Compressive-Tensile Mechanics and Energy Consumptions of a Cementitious Composite with High Utilization of Steel Slag

In response to the National Development and Reform Commission's “Guiding Opinions on Comprehensive Utilization of Large Solid Wastes during the Fourteenth Five Year Plan”, further expand the use of steel slag as concrete admixture in construction projects and other fields, and gradually improve the comprehensive utilization ratio, a cementitious composite with high utilization of steel slag (CHS) was developed, which is with the cement replaced by high-content super-fine steel slag powder (SSP) (replacement ratio υ ≥ 30%) as the cementitious materials, steel slag sand (SS) as the only aggregate and environmentally basalt fiber (BF) for toughening. It improves the utilization percentage of steel slag (SSP and SS) and reduces the consumption of natural resources such as cement and natural sand. Use BF to achieve better strength and toughness. In order to better understand the performance of CHS and make it better used in the engineering field. Study the influence of each component on the strength and energy consumption of compression and splitting tension, and strive to find the optimal proportion and lay the theoretical foundation for its application. Through the tests, the effects of high replacement ratio υ (30%–50%), low binder-aggregate ratio γ (0.31–0.44), and BF content ρv (0%–2%) on the aspects of peak strength, force-deformation curve and energy consumption were analyzed. The results show that the standard curing fck and ft,s can reach 40 MPa and 5 MPa respectively. With the increase of υ, the maximum axial compressive strength fck and splitting tensile strength ft,s decreased insignificantly. The γ has an important influence on fck and ft,s. When it increases from 0.31 to 0.44, fck increases linearly by 63.1% to 40.4 MPa, while ft,s increases by 52.8% to 5.18 MPa. As ρv increases, fck and ft,s show a trend of first increasing and then decreasing. ρv exerts a significant impact on the descending segments of stress-strain response curves of the compression which expressed as bilinear and trilinear models with different ρv after normalization. The energy consumptions of peak, total, and residual (Epeak, Edisp, Eres) show a slight downward trend with the increase of υ, a significantly upward trend with the increase of γ. With the increase of γv, and Edisp increase first and then tend to be flat, while Eres always increases and the percentages of Eres/Edisp in the compressive test increase from 22.6% to 38.5%, reflecting the improvement of the compressive toughness of BF.

Similar ratio experiment and characteristic analysis of quasi-sandstone

The stability control of surrounding rock in deep roadway is becoming more and more difficult, and grouting reinforcement support has become the mainstream of roadway control. In order to obtain the ratio of quasi-sandstone material corresponding to the grouting body, this paper uses river sand as aggregate, cement and gypsum as cementing agent, retarder and defoamer as additives, and carries out orthogonal proportioning tests with three influencing factors: water-binder ratio (ratio of water to mass of cementing agent), gypsum-cement ratio (ratio of gypsum to mass of cement) and binder-aggregate ratio (ratio of cementing agent to aggregate mass), and compares and analyzes the sensitivity of each factor on the density, compressive strength, tensile strength, elastic modulus, Poisson’s ratio, longitudinal wave velocity, elasticity index and brittleness index of quasi-sandstone material. The results show that 1) the Water-binder ratio has the greatest effect on the sensitivity of material compressive strength, tensile strength, elastic modulus, Poisson’s ratio and longitudinal wave velocity; the gypsum-cement ratio has the greatest effect on the sensitivity of material deformation index and brittleness index; the binder-aggregate ratio has the greatest effect on the sensitivity of material density. 2) Reducing the Water-binder ratio can improve the density, compressive strength and tensile strength of the material; reducing the paste ratio can improve the modulus of elasticity, Poisson’s ratio and longitudinal wave speed of the material; as the gypsum-cement ratio increases, the deformation index first decreases and then increases and then decreases; as the binder-aggregate ratio increases, the brittleness index first increases and then decreases and then increases. 3) The empirical equations between physical and mechanical properties of sandstone-like materials and Water-binder ratio, gypsum-cement ratio and binder-aggregate ratio were established based on multiple linear regression analysis, and more reasonable material ratios were quickly obtained by physical and mechanical parameters of materials. The results of the study provide theoretical references for similar material simulation tests for quasi-sandstone grouting.

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

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

Hydraulic Performance of Pervious Concrete Based on Small Size Aggregates

The paper aims to study the impact of clogging on pervious concrete mixes and explore a simple method to calculate permeability and clogging using the falling head method in a fabricated unit. The materials used are cementitious materials and aggregates, along with superplasticizers. The cementitious materials used are OPC Grade 53 cement and micro Ground Granulated Blast Furnace Slag (μGGBS). Two separate narrow aggregate gradations are used: 2.36–4.75 mm and 4.75–6.30 mm. The water-binder ratio is taken as 0.25, and the aggregate-binder ratio is taken as 3.33. The compressive strength, permeability, and clogging potential of pervious concrete are calculated. The average permeability for 2.36–4.75 mm and 4.75–6.3 mm is 4.78 mm/s and 8.16 m/s, respectively. The clogging materials used are clay and sand with a concentration of 5 g/l. The introduction of clay slurry reduces the permeability by 69.8% and 74.9%, respectively, and with sand, it decreases by 74.7% and 71.7%, respectively, in its first cycle. The permeability response for such small aggregates is different from the standard coarse aggregates. The paper compares the study’s compressive strength, porosity, and permeability with the existing literature. It concludes that the maximum clogging occurs when the clogging material is introduced to the specimen for the first time. The degradation of permeability depends on the clogging particle’s particulate size and the concrete matrix’s pore size. The smaller aggregates in pervious concrete are not recommended in areas of high siltation.

Evaluating Durability Properties of Composite Fibre Reinforced Concrete by Using Mineral Admixtures

This study is aimed at investigating durability properties of fibre reinforced concrete. The sorptivity test to assess rate of absorption, and the rapid chloride penetration test was performed to assess the permeability of concrete. The weight loss and strength loss measured after 28 and 56 days immersion in 5% concentrated HCL, H2SO4 solution to check aggressive ions of concrete, such as chlorides and sulphates. Normal concrete is used for the above assessment. The addition of nano silica by fractions such 0%, 1.5%, 3.0%, and 4.5% by weight of cement. For each of above combination 1% steel and 0.25% polypropylenes fibres respectively by volume of binders were added. A constant aggregate binder ratio and water binder ratio were maintained throughout this investigation process. At the end of above testing, the aim is to find out optimum percentage combination of ultra fine fly ash and nanosilica to achieve better durability of concrete.

Preparation and Strength Formation Mechanism of Calcined Oyster Shell, Red Mud, Slag, and Iron Tailing Composite Cemented Paste Backfill.

The use of bulk solid-waste iron tailing (IOT), red mud (RM), and oyster shells to prepare cemented paste backfill (CPB) can effectively solve the ecological problems caused by industrial solid waste storage and improve the utilization rate of such materials. In this study, a new type of CPB was prepared by partially replacing slag with RM, with calcined oyster shell (COS) as the alkaline activator and IOT as aggregate. The central composite design (CCD) method was used to design experiments to predict the effects of the COS dosage, RM substitution rate, solid mass, and aggregate–binder ratio using 28-dUCS, slump, and the cost of CPB. In this way, a regression model was established. The quantum genetic algorithm (QGA) was used to optimize the regression model, and X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) microscopic tests are performed on CPB samples of different ages with the optimal mix ratio. The results showed that COS is a highly active alkaline substance that provides an alkaline environment for polymerization reactions. In the alkaline medium, the hematite and goethite in RM and quartz in IOT gradually dissolved and participated in the process of polymerization. The main polymerization products of the CPB samples are calcium–silicate–hydrogel (C–S–H), calcium–aluminosilicate–hydrogel (C–A–S–H), and aluminosilicate crystals such as quartz, albite, and foshagite. These products are intertwined and filled in the internal pores of the CPB, enabling the pore contents to decrease and the interiors of the CPB samples to gradually connect into a whole. In this way, the compressive strength is increased.

Property analysis and mixture design of high ductility cementitious composites with totally recycled fine aggregate based on target strength and strain capacity

The natural fine aggregate was completely substituted by the crushed waste concrete particles with original particle grade in preparing high ductility cementitious composite to promote the waste recycling, reduce the environmental pollution, realize the cleaner production and achieve the better properties in this study. The compressive and uniaxial tensile tests were conducted to analyze the effects of water-binder ratio, fiber volume fraction, recycled fine aggregate-binder ratio and fly ash content on the mechanical properties of high ductility cementitious composites with totally recycled fine aggregate (R-HDCC). The test results showed that the compressive strength of R-HDCC decreased significantly with the increasing of water-binder ratio. The peak tensile stress of R-HDCC was improved remarkably as fiber volume fraction increased and water-binder ratio decreased. The ultimate tensile strain of R-HDCC increased significantly with the increasing of water-binder ratio, fiber volume fraction and fly ash content, whereas reduced with the increasing of recycled fine aggregate-binder ratio. The relationships between the compressive strength, the peak tensile stress, ultimate tensile strain of R-HDCC and corresponding key parameters were set up according to the statistical analysis of test results. Then a mixture design method of R-HDCC based on the target strength and strain capacity was further developed. The detailed procedure of using the proposed mixture design method was illustrated with examples, and the reliability of the method was verified by the experimental results in this study and relevant literatures.

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.

Combined effect of metakaolin and hybrid fibers on the strength properties of high performance concrete

This study aims to investigate the combined effects of Metakaolin (MK) and Hybrid fibers on High-Performance Concrete's (HPC) mechanical properties. A constant proportion of 0.25% for polypropylene fibers (PF) and varying proportions of 0%, 0.5%, 0.75% and 1.0% for steel fibers (SF) making a total fiber volume fractions of 0%, 0.75%, 1.0% and 1.25% were used to develop hybrid fiber-reinforced high-performance concrete (HFRHPC). Four replacement levels for hybrid fibers by volume of the binders and four partial replacement levels for Metakaolin (0%, 10%, 20% & 30%) by weight of cement have been considered for three different water binder ratios (0.275, 0.325 & 0.375). An aggregate binder ratio of 1.75 was kept constant. The test results reveal a maximum increase of 31.83%, 37.05%, and 36.53% in compressive strength for curing periods of 7, 28, and 56 days, respectively. The split tensile strength, flexural strength, and impact strength test results show an increase of 42%, 74.41%, and 68.32% for a curing period of 28 days, respectively. Additionally, linear regression analysis was performed, and plots of compressive strength v/s tensile strength and compressive strength v/s flexural strength have been obtained to develop a relationship between compressive strength, tensile strength, and flexural strength. With the incorporation of metakaolin and hybrid fibers into the concrete matrix, very high mechanical properties could be achieved. The results indicate that a combination of 1.25% hybrid fibers and 10% Metakaolin gains all the water-binder ratios' highest strength.

Strength and Durability Studies on Hybrid Fiber Reinforced High-Performance Concrete for Silica Fume Based Mineral Admixture

This study aims to investigate the strength and durability studies on Hybrid fibers reinforced High-Performance Concrete for Silica fume (SF) based mineral admixture. A constant proportion of 0.25% for polypropylene fibers (PF) and varying proportions of 0%, 0.5%, 0.75% and 1.0% for crimped steel fibers (CF) making a total fiber volume fractions of 0%, 0.75%, 1.0% and 1.25% were used to develop hybrid fiber-reinforced high-performance concrete (HFRHPC). Four replacement levels for hybrid fibers by volume of the binders and four partial replacement levels for Silica fume (0%, 10%, 20% & 30%) by weight of cement have been considered for three different water binder ratios (0.275, 0.325 & 0.375). An aggregate binder ratio of 1.75 was kept constant. The test results reveal a maximum increase of 35.18%, 40.35%, and 71.54% in compressive strength, split tensile strength, and flexural strength, respectively, for a curing period of 28 days. Acid attack tests have been conducted to measure the durability of HFRHPC. Cubes of 100x100x00mm have been cast, cured, and then kept immersed in 5% concentrated solutions of Hydrochloric acid (HCL), Magnesium sulphate (MgSO4), and Sulphuric acid ( H2SO4) for 30,60 and 90 days and then tested to record the residual compressive strength of HFRHPC produced with the Silica fume mineral admixtures. The results have been analyzed, and valid conclusions have been drawn. The results indicate that a combination of 1.25% hybrid fibers and 10% Silica fume mineral admixture gains all the water-binder ratios’ highest strength.