Coarse Aggregate Gradation Research Articles

Research on Steel Fiber Reinforced Concrete Mix Proportion Based on the Theory of the Orthogonal Experiment

According to the needs of the quick mending engineering in concrete pavement, the theory of orthogonal experiment and the major indicators that influence the performance of steel fiber reinforced concrete, the influence of the various factors’ change on physical and mechanical properties of the mixed steel fiber reinforced concrete is studied, with water-cement ratio, accelerator, steel fiber content, coarse aggregate gradation as the essential factor. The research shows that flexural strength of steel fiber reinforced concrete increases with the increase of the steel fiber content and decreases with the increase of the water-cement ratio. In addition, the level of grade aggregate also has an important influence on the flexural strength of steel fiber reinforced concrete. The study figures out the optimum mix proportion of steel fiber reinforced concrete and provide a good reference to engineering application.

Experimental study on dynamic splitting of recycled concrete using SHPB

To study the recycled concrete splitting tensile properties and fracture state with various recycled coarse aggregate replacement percentage (i.e. 0%, 25%, 50%, 75% and 100%), the dynamic splitting test of recycled concrete was carried out using large diameter (75 mm) split Hopkinson pressure bar (SHPB). The results show that the recycled concrete splitting tensile strength increases with the increase of loading rate, and the loading rate also affects the recycled concrete fracture state, which indicates that the recycled concrete has obvious rate sensitivity. The damage state of the recycled concrete is not only the destruction of the interface between coarse aggregate and cement mortar, but also associates with the fracture damage of aggregates. Under the same water cement ratio, when the replacement percentage of coarse aggregates is around 50%–75%, the gradation of natural and recycled coarse aggregate is optimal, and thus the splitting tensile strength is the largest. This study offers theoretical basis for the engineering applications of recycled concrete.

Effect of Using Waste Material as Filler in Bituminous Mix Design

Bituminous concrete or asphaltic concrete is one of the highest and costliest types of flexible pavement layers used in surface course. Being of high cost specifications, the bituminous mixes are properly designed to satisfy the design requirements of the stability and durability. The mixture contains dense grading of coarse aggregate, fine aggregate and mineral filler coated with bitumen binder. The mineral filler passing through 0.075 mm sieve performs some important roles in bituminous mixes. Marshall Stability of bituminous mix increases as the amount of filler increases. The Asphalt Institute recommends the use of 4 to 8% filler in asphalt concrete. The common filler materials like cement, lime stone, granite powder etc. is not easily and economically available in Bangladesh. Waste concrete dust and brick dust are considered to be cheaper and in abundant supply in Bangladesh. In this study an attempt is made to find the effect of types of filler on the behavior of bituminous mixes. According the properties of bituminous mixes containing filler like waste concrete dust and brick dust is studied and compared with the mixes containing filler like fine sand and stone dust mixture generally used. The Marshall method of mix design was used for the comparison. The Marshall stabilities of mix types containing filler fine sand and stone dust mixture, waste concrete dust and brick dust were found 9.8 KN, 11.1 KN and 11.3 KN respectively which satisfy the limiting value of 5.33 KN according to Marshall Design criteria. The study indicates the possibility of using waste concrete dust and brick dust as filler in bituminous mix.

Water flow simulation and analysis in HMA microstructure

Abstract: This paper introduces a new method for reconstructing virtual two-dimensional (2-D) microstructure of hot mix asphalt (HMA). Based on the method, the gradation of coarse aggregates and the film thickness of the asphalt binder can be defined by the user. The HMA microstructure then serves as the input to the computational fluid dynamic (CFD) software (ANSYS-FLUENT) to investigate the water flow pattern through it. It is found that the realistic flow fields can be simulated in the 2-D micro-structure and the flow patterns in some typical air void structures can be identified. These flow patterns can be used to explain the mechanism that could result in moisture damage in HMA pavement. The one-dimensional numerical permeability values are also derived from the flow fields of the 2-D HMA microstructure and compared with the measured values obtained by the Karol-Warner permeameter. Because the interconnected air voids channels in actual HMA samples cannot be fully represented in a 2-D model, some poor agreements need to be improved.

Research and application of statistical law of VCA formed from the packing of basalt coarse aggregates

The void in coarse aggregate (VCA) has an important influence on the void in mineral aggregate (VMA) of hot mix asphalt (HMA) and naturally affects the grading design. In order to find a universal law of the VCA changing with the grading of coarse aggregates to provide a theoretical support for grading design of HMA, some basalt coarse aggregates with diffident sizes were used and sixteen experimental schemes were arranged by Uniform Experiment Design Method (UEDM). The VCA values of each experimental scheme were obtained through tamping test and vibrating compaction experiments. Based on the smaller VCA values obtained by vibrating compaction experiments four effective regression model were established and the best one was selected; then the scope of application of the best regression model was discussed and the formation law and forming mechanism of VCA were analyzed. The analysis results show that, for the coarse aggregate, compared with other shapes of grading curves, the forward S-shaped grading curves have larger VCA values, and the farther it is from the theoretical maximum density line (TMDL), the greater the VCA value is; while the reverse S-shaped grading curves have the smallest VCA values even compared with the TMDL of coarse aggregates.

Mechanical Characteristic of Pervious Concrete Considering the Gradation and Size of Coarse Aggregates

Pervious concrete is a kind of sustainable pavement with high permeability which is becoming more common as a storm water management. The purpose of this study was to investigate the effects of coarse aggregate on physical and mechanical properties of the pervious concrete such as density, strength, porosity and permeability at 7, 28, 56 days. This experimental investigation conducted by comparing nine different mixtures. Taguchi design of experiments used to optimize the performance of these characteristics. To test the influence of aggregate systematically, water to cement ratio (w/c), paste content and coarse aggregate size were kept constant at 3 levels. 9.5, 12.5 and 19.0 mm were used for maximum aggregate sizes. The relationship between strength and porosity for pervious concrete are found to be dependent on coarse aggregate size. The test results demonstrated when the maximum size of the coarse aggregate increased, the strength decreases and the permeability and porosity grows up. An increased aggregate amount resulted in a significant decrease in compressive strength due to the subsequent decrease in paste amount. Age and coarse aggregate size had effect on the pervious concrete characteristic. To meet the specification requirements in the mix design of pervious concrete, considering both compressive strength and permeability is necessary. Finally, a parametric study is conducted to investigate the influence of design factors on the properties of porous concrete. The general equations for pervious concrete are related to compressive strength and void ratio for different aggregate sizes.

Study of Highway Coarse Aggregate Gradation on Airport Pavement Concrete Design

This paper chose 5~31.5 mm coarse aggregate (commonly used in highway) to supersede 5~20 mm, 20~40 mm double-graded coarse aggregate (commonly used in airport pavement), studying the influence of 5~31.5 mm coarse aggregate on the airport pavement concrete. The results show that the flexural strength and loss rate of relative dynamic elastic modulus of airport pavement concrete prepared with 5~31.5 mm coarse aggregate meet the airport pavement design requirement, the optimum mix amount is the water-cement ratio of 0.40 and the unit cement consumption of 330 kg/m3, and for frost resistance durability after 200 freeze-thaw cycles, the relative dynamic elastic modulus is still above 90%.

Experimental Studies on Basic Performance and Application of Self-Compacting Concrete Using Waste Brick Recycled Coarse Aggregate

With rapid economic development in China, the frequency of that new buildings replace old buildings increases gradually in rural areas, which inevitably results in the emergence of a large amount of waste clay brick. The processing of construction waste takes up a lot of land resources and worsen the existing rural environmental pollution situation. using waste clay brick to prepare recycled coarse aggregate concrete not only can effectively eliminate construction waste and reduce the consumption of original coarse aggregate and thus the cost of buildings, but also solves a series of environmental problems—it conforms to the concept of "green building" and stands in line with the strategic objectives of sustainable development. This paper researched on the influence of recycled coarse aggregate gradation and water cement ratio to the strength of recycled concrete at first, then experimentally verified the application feasibility of recycled coarse aggregate self-compacting concrete.

Air Void Characterisation in Porous Asphalt Using X-Ray Computed Tomography

This study presents the characterisation of the air voids distribution for porous asphalt mixtures compacted using gyratory compactor. The distribution of voids content and voids shape within the porous asphalt were characterised for different nominal maximum aggregate size (NMAS) and specimen height. This is to evaluate the effect of different aggregate size composition and lift thickness on the air voids characteristics of the compacted porous asphalt. Two types of gradations were adopted i.e. Grading A (with NMAS=10 mm) and Grading B (with NMAS=14 mm) and they were fabricated for two different heights (50 and 100 mm). The internal structure was captured using X-ray Computed Tomography and image analysis techniques were used to process and analyse the images. It was found that mixture with coarse aggregate gradation produced larger void size with an elongated shape, which indicates voids connectivity within the mixture compared to fine gradation with more circular and smaller void size.For lift thickness, itacts differentlyfor different aggregate gradations. The specimen produced greater voids connectivity when the fine and coarse gradations were compacted at 100 mm and 50 mm respectively. These show that NMAS and lift thickness influence the mobility of the aggregate particles during compaction which affect the voids formation and determine the effectiveness of the compaction.

Rubberized asphalt mixture design using a theoretical model

A theoretical model was introduced for designing the rubberized asphalt mixtures and validated by mixture tests in this paper. This model is comprised of three parts: fine aggregate gradation design, coarse aggregate gradation design and mixture volumetric design. The rubberized asphalt mixture with a nominal maximum aggregate size of 13mm (AR-13) was designed with this model. The orthogonal experimental design method was then employed to study the effect of design parameters (air voids (VV), voids in mineral aggregate (VMA) and Fuller-curve’s exponent n) on the rutting performance of the mixture. The orthogonal experimental results indicate that the VV and VMA are the two key parameters which affect the rutting performance of the rubberized asphalt mixtures. The design parameter optimal combination and performance requirements of AR-13 were finally recommended based on the experimental results and previous experiences in China and America.

Research on Roller Compacted Concrete Graduation with Vibration Liquefaction

In the rolling process, reasonable way of grading and rolling can improve the compactness and anti-permeability of roller compacted concrete (RCC), as well can make its strength meet the design requirements. Vibration liquefaction is the key step for RCC in the rolling process. Therefore, this paper first puts forward the more suitable method, Modified Vebe Vibration Liquefaction Test, to account for the characteristics of vibration liquefaction in RCC, and then, studies the coarse aggregate gradation scope using aggregate gradually filling theory. Though Modified Vebe Vibration Liquefaction Test, the research show that the aggregate VCA and the characteristics of vibration liquefaction of RCC have a good correlation. Finally, by studying the sand ratio and fineness modulus of sand how to affect the performance of liquefied RCC, the optimum value range of sand ratio and fineness modulus of sand was determined.

Sandless concrete with fly ash as supplementary cementing material

As a step towards an environmental friendly and sustainable construction, the properties of concrete made without natural sand (termed sandless concrete herein) and with cement partially replaced with fly ash were investigated. First, the appropriate mixture proportion to ensure the desired properties in sandless concrete for structural applications was established. The effects of coarse aggregate grading, aggregate–cement (A/C) ratio, and water–cement (w/c) ratio on compressive strength were investigated. It was shown that compressive strengths of 30–50 MPa could be readily achieved with w/c ratios less than 0.5 and A/C ratios less than 3. Next, the effect of cement replacement by Class-F fly ash by up to 50% on the fresh and hardened properties of sandless concrete was investigated. The incorporation of fly ash improved workability and resulted in higher long-term strength, reduced drying shrinkage, and higher resistance to chloride ingress.

The Effect of Coarse Aggregate Gradation Degradation on the Mechanical Behavior of Asphalt Mixture

The objective of this study is to investigate and evaluate the effect of coarse aggregates (aggregate size bigger than 2.36 mm) on the compressive strength and creep behavior of asphalt mixture. The variable that is mainly considered in the study is the gradation degradation of coarse aggregates. A kind of standard aggregate gradation and three kinds of degraded aggregate gradation mixture specimens are used. Uniaxial compression and static creep tests were realized at different loading conditions and temperatures. The test results on asphalt mixture showed that the compressive strength and creep behavior of asphalt mixture are significant affected by the different coarse aggregate gradations.

Research on Properties of Recycled Coarse Aggregate

The performance of recycled coarse aggregate has significant effects on recycled concrete. The performance of recycled coarse aggregate were tested according to Recycled coarse aggregate for concrete (GB/T 25177-2010). The Result showed that the recycled coarse aggregate grading in accordance with regulation requirements, and compared with the natural coarse aggregate: high powder content and water absorption, low needle and plate particle content, low apparent density, compression capability as low as soundness. And the property of recycled coarse aggregate after cleaning has the performance of guaranteeing the quality by using. Through the test results and consult the national regulation, the recycled coarse aggregate in Xinjiang can be preliminary division to the categories of I and II.

Coarse Aggregate Gradation Design Index and Method of Asphalt Mixture

The gradation of asphalt mixture is a main factor on the asphalt pavement performance, and coarse aggregate skeleton is an effect of distribution in the primary factor. The article analyses the interaction among the particle sizes of coarse aggregate by VCA and CBR double controlling index of aggregate gradually filling test, and identifies the key sizes of coarse aggregate by uniform design and grey system theory, and recommends particles size range content of coarse aggregate. The results show that coarse aggregate skeleton gradation of asphalt mixture by filling test has a good correlation with VCA and CBR.

Research on Coarse Aggregate Gradation of SMA Mixture Influence with Material Properties

SMA is made by a large number of coarse aggregate skeleton formed, so the coarse aggregate gradation on pavement performance of SMA effect. Since 80 time, SMA mixture in many European countries has been widely used. In recent years, our country road workers on SMA mixture also conducted very fruitful research, and started engineering application. In this paper, SMA mixture in practical application, through the coarse aggregate ratio changes as well as the volume and density of tests on high temperature stability influence made some experimental study.

Research on the Strength of High-Strength Steel Slag Concrete with Skeleton Coarse Aggregate Gradation

Generally the high density in high-strength concrete results in high strength, and so people often mix superplasticizer and particulate to increase the density of concrete, but ignoring the effect of coarse aggregate gradation on concrete strength. Referring to several Gradation Theories, this paper selects the coarse aggregate gradation with skeleton, uses uniform design method to test the compressive strength of high-strength concrete, and analyses the test results. It can be known from the test results of 7d and 28d concrete specimen that the concrete strength decreases linearly with water-cement ratio and sand ratio; The 7d’s concrete strength has higher variability due to low water-cement ratio with superplasticizer; The coarse aggregate skeleton is interfered by the increase of steel slag and sand rate, and the concrete strength decreases with limited cement paste. Furthermore, the steel slag with less than 30% addition has little effect on concrete strength and it can increase the cement’s possibility of contacting to water, and reduce the amount of cement without lowering the concrete strength. The influential degree on the compressive strength of concrete is followed by ascending sequence of steel slag content, sand ratio and water-cement.

Application of Fractal Theory on the Cement Stabilized Recycled Course Aggregate Base Material

This paper studied different size-distribution of recycled coarse aggregates by fractal theory. Cement Stabilized Recycled Aggregate Mixture were prepared by different fractal rate aggregate gradations and the unconfined compressive strength at 7 d and 28 d of the materials were tested. The results showed that the unconfined compressive strength at 7 d and 28 d of the materials with recycled coarse aggregate were higher than the one with natural aggregate when coarse aggregate gradations were same. The higher source rock strength of recycled coarse aggregate was, the larger base material strength was. Generally, the increase of fractal dimension is conducive to the growth of strength. The base materials performances of the same fractal dimension were different when the max particle size was different. So the fractal dimension of recycled coarse aggregate must be determined by maximum particle size.

Influence of Aggregate Gradation of Coarse Aggregates on Concrete Strength

Concrete is widely used in engineering construction, and studying how to improve the strength of concrete is particularly important. The coarse aggregate is one of the elements in concrete, its property affects the strength of concrete prominently. The effect of coarse aggregate size distribution on the development process of concrete strength was studied, while keeping the constant content of coarse aggregate and altering the size distribution of coarse aggregate and the water to cement ratio. The experimental results show that when the maximum aggregate size is 10mm, 20mm and 30mm respectively, the compressive strength of concrete will be increased, and the flexural strength of concrete will be reduced.

Experimental Analysis of Failure Modes and Pavement Strength Control Parameters to Existing Cement Concrete Pavement

Cement concrete pavement as a common form of the road has been widely used because of its high strength, stiffness, and good durability characteristics. In order to explore failure modes and the strength control factors of the cement concrete pavement in the region, site investigation and the orthogonal test method in laboratory are used. Test combination design for the main control factors of the cement concrete strength was executed based on orthogonal test method. Strength of concrete specimen was determined by using indoor pressure test machine. The results show that the chiefly control parameter of affecting concrete strength is water cement ratio and the following are sand ratio and the coarse aggregate grading.