جستجوی مقالات مرتبط با کلیدواژه "roller compacted concrete pavement" در نشریات گروه "عمران"

Every year, a significant amount of waste brick is removed from the construction cycle and is accumulated in the landfill. The recycling of these wastes can significantly reduce the problem of waste storage and environmental pollution and help preserve the resources of natural aggregates. In the current research, crushed brick aggregate (CBA) has been used as a substitute for sand (0, 10, 20, 30 and 40%) in 5 roller compacted concrete pavement (RCCP) mixing plans. Mechanical properties including tests of compressive strength, tensile strength, and fracture behavior in the first mode of loading using a three-point bending test on 60 semi-circular bending (SCB) specimens with initial cracks of 20 and 25 mm in length and the loading rate of 1 and 5 mm/min was studied. The results indicate that the compressive and tensile strength values of RCCP samples decrease with the increase in the amount of CBA. At a constant loading rate, the fracture toughness (KI) decreases with increasing crack length, and, with increasing loading rate, KI increases in constant crack length.

In this study, mechanical properties of roller compacted concrete pavement (RCCP) containing metakaolin (MK) with or without polypropylene fibers (PP) are experimentally and analytically investigated. For this purpose, sixteen different mixes were designed and tested in the lab. The effect of using polypropylene fibers in 0, 0.05, 0.1 and 0.2 percent of cement volume with metakaolin powder in 0, 7.5, 15 and 22.5 percent of cement weight was investigated. Compressive strength, tensile strength and water absorption were evaluated. The results showed that the highest compressive strength occurs in the combination of 0.1% of PP and 15% of MK that increases the compressive strength of 7 and 28 days respectively, by 51% and 25% compared to the reference sample. The tensile strength using the above combination increased 42%, which is the highest increase in the tensile strength. With using of 0.1% of PP and 22.5% of MK, maximum decrease in water absorption was observed by 11% compared to the reference sample. In this research, analytical formulas predicted properties of the RCCP and estimated optimal combination of the PP and MK.

Using Roller Compacted Concrete Pavement (RCCP) is expanding all around the world and it shows the importance of accurate experimental assessment of this kind of concrete. Limited researches investigated the effect of diameter and content of steel fiber in RCCP. In this research, in order to investigate the influence of volume fraction and diameter of hooked-end steel fiber on Vebe time, compressive strength, splitting tensile strength, flexural strength, and toughness of RCCP, ten mixtures were used. One control mixture and nine fibrous mixtures contain volume fraction of 0.25-0.75 and diameter of 0.38-0.7 mm fiber were constructed. Results showed that increment of fiber volume fraction and decrease of fiber diameter led to increase of mechanical properties and Vebe time of RCCP. Due to experiments, the factor of volume fraction was more determinative than diameter. By adding hooked-end steel fiber, load-deflection curve and toughness demonstrate sensible improvement. Mixture with volume fraction of 0.75 and diameter of 0.38 mm recorded the most appropriate mechanical strength and toughness, and the results of splitting tensile and flexural strength indicated increment more than about 100%.

Roller compacted concrete pavement (RCCP) is a zero-slump and stiff-dry mixture which is usually placed with an asphalt paver and compacted by conventional vibratory roller compactors to achieve the required density. RCCP consistently has a slightly lower cement content than conventional concretes of similar strength. Nowadays, RCCP is used for any type of industrial or heavy-duty pavement and has advantages including cost saving as a result of the construction method and the increased placement speed of the pavement. Therefore, the use of RCCP pavement has become more and more popular in recent years. There are numerous studies on the mechanical properties of fibre reinforced focused on cement paste and normal concrete. However, our understanding of what exactly happens when hybrid fibres used to reinforce RCCP mixes with respect to fracture toughness is quite limited. Accordingly, in this study, three point bending test was carried out on mono and hybrid fibre-reinforced RCCP based on modified two-parameter model to determine the value of Mode I plane-strain fracture toughness of fibre-reinforced RCCP by considering possibility of crack deflection during its propagation through modified two-parameter fracture model. Finally, it can be observed that, for great amount of fracture angle, the application of Two-parameter fracture model instead of modified Two-parameter fracture model cause to an overestimation of the fracture toughness values.

It has been spent big amouts of budget for design,build and maintenance of roads in all over the world.Many of the failures occurring in pavements are as results of different vehicle loads,environmental changes and poor maintenance strategies.One of the important issues that creates cracks in concrete pavement and reduces pavement loading capacity is thermal stresses caused by temperature gradients and combined streeses due to temperature gradient and traffic loads.Factors such as solar radiation,temperature changes and etc. cause thermal stresses in pavements. These stresses , alone or in combination with traffic loading, can lead to cracks in the surfaces of the pavement, which can gradually lead to the removal and destruction of concrete pavement. Therefore, research on effective parameters of this issue seems necessary. Until the advent of the finite element method, these categories of researches were carried out experimentally, which, due to their hardiness, over time, gave their place to numerical methods. In this paper, the Abqus software is used to model three-dimensional roller compacted concrete pavement and to investigate the response of this pavement under the combination of traffic and thermal loading.

One of the new types of concrete that helps to solve problems such as cracking, grooving in concrete, and is known as one of the most popular concretes in the civil engineering community, is roller concrete (RCC) which is made in construction. Types of road pavements and structural uses can be used. In recent years Due to the high cost of pavement construction and environmental considerations, various waste and recycled materials have been used in concrete mixes and roller concrete. In this research, a relatively comprehensive review of the composition of waste and recycled materials on the mechanical properties of roller concrete is presented. The mechanical properties of roller concrete by replacing coarse and fine-grained materials in concrete with recycled materials including rubber chips and steel slag have been investigated in a leading study. In the researches, compressive strength, indirect tensile and three-point bending tests have been performed on 7 and 28 day samples.3-point bending test is used to obtain flexural strength and toughness and energy absorption.

Concrete pavement bears dynamic loads and is exposed to destructive environmental effects. Abrasion resistance is one of the items that will be very effective in increasing the durability of concrete pavement. The abrasion resistance of concrete is more effective and drier under the influence of compressive strength, concrete surface curing technique, type of setting, curing, aggregate properties and test conditions. Today the factors affecting the wear and durability of concrete procedures, is of particular importance, so this study evaluates the strategies affecting the performance of compressive strength and Abrasion and durability of pavement concrete. A total of thirty cylindrical samples were created, with approximately half of them being used for Dorry wear evaluations. The type and of minerals type and constituents of stone materials has a direct effect on the abrasion resistance of roller concrete, so that increasing the abrasion resistance of stone materials increases the abrasion resistance of concrete. Of all the aggregates used in this research, aggregate No. 3 prepared from Choghart mine, tectonic block 1, has the highest wear resistance and compressive strength, which is very suitable for use in places where roller concrete pavement is exposed to wear and stress. The results of friction resistance are suitable for all samples and aggregates No. 4 and 3 showed the highest friction resistance on wet surfaces. The findings also show that Dorry wear test results with a dependence coefficient of 80% in roller concrete pavement is dependent on the wear of aggregates.

The purpose of this study is to investigate strategies to improve the skid resistance of roller-compacted concrete. Since the main weakness of roller-compacted concrete is the lack of pavement macrotexture, in this study, three types of macro textures, 1- Seeding (in three aggregate sizes), stamping (in two sizes), and grooving (one-way and two-way) were considered. In this research, eight mixing designs were selected to make roller-compacted concrete samples. The skid resistance of treated samples for 28 days before and after abrasion was evaluated by a British pendulum test. The results showed that concrete surface abrasion reduces the skid resistance of concrete samples by about 10%. The results also showed that changing different mixing designs did not have a significant effect on skid resistance. While the skid resistance is completely dependent on the type of macrotexture so that the grooved macrotexture shows the highest and the seeding shows the lowest skid resistance before and after abrasion.

In recent years, the use of Roller–Compacted Concrete Pavement (RCCP) has developed in road pavement due to its great advantages. Adding fibers to RCC can improve some properties of the concrete, including flexural strength, fatigue resistance, crack growth rate, and shear transfer along cracks and joints. Many experiments have shown the advantages of using fiber-reinforced concrete in RCC, but more information is needed about their behavior in cold regions, and especially the exposure to Freeze-Thaw cycling. Investigation and comparing the effect of polymer fibers on the strength and durability of Roller-Compacted Concrete under Freeze-Thaw cycling are the main goal of the present article. Therefore, specimens with weight percentage of fiber equal to 1, 2.5, and 4% (by weight of cement) and fibers of to 5, 20 and 40 mm lengths are made. Durability test against a Freeze-Thaw cycling and compressive strength are measured on samples after 7, 28 and 90 days. Analysis of the results shows that the additive fiber increases the compressive strength of the RCC, but decreases its durability against the melting and freezing cycles. Therefore, the use of fibers on RCC in cold regions should be done due accuracy and attention.

Roller Compacted Concrete is defined as a concrete with zero slump. It will support a roller while being compacted in its unhardened state. RCC is used in two general areas of engineered constructions: dams and pavements. In this study, RCC will be discussed only in the context of its use in pavements. In this regard, Some material savings may be possible due to the lower cement content normally needed in RCC pavement mixtures to achieve strengths equivalent to those of conventional concretes. The other advantages of using RCC include cost savings as a result of the construction method and the increased placement speed of the pavement.Unreinforced concrete has a low tensile strength and a low strain capacity at fracture. It was reported in many studies that NS significantly improved the mechanical properties and durability of cement-based materials. In this study we carried out a comprehensive investigation of the results caused by the addition of steel fibers and nano silica particles in mechanical properties of RCCP. Therefore, with varying amounts of steel fibers (0.00%, 0.33%, 0.67% and 1.00% by the volume of concrete) and nano silica particles (0.0%, 0.5%, 1.0% and 1.5% by the weight of cement), RCCP was prepared and consistency and mechanical properties (compression strength, tension strength, flexural strength, and thoughness) were investigated. The results indicated that the addition of steel fibers and nano silica leads to positive mechanical properties of RCCP.

Abstract Nowadays, roller compacted concrete pavement, (RCCP), is becoming popular due to lower cost of construction, repair, and maintenance compared with those for normal concrete. However, due to the roughness of the RCCP surface, its use in highway roads is limited. In the present paper, the effects of two different compound layers on mechanical and frost resistance of RCCP were investigated. Slag and silica fume were used as a partial replacement for cement in the predetermined mixtures. Two compound layers of the hot mix asphalt (HMA) and air-entrained concrete (AEC) were used. The mixtures were suffered under freeze-thaw cycles in the present of de-icing salt. The compressive strength and the connection resistance between the compound layers and RCCP after freeze-thaw cycles were evaluated via slant shear and splitting tensile tests. The results indicated that the addition of slag reduced both compressive strength and salt scaling resistance. On the contrary, silica fume improved compressive strength and particularly salt scaling resistance of the specimens. The results also showed that the connection resistance of the specimens was reduced, due to freeze-thaw cycles in the presence of the de-icing agent, about 12% and 10% for HMA and AEC layers, respectively.

This study examined the possibility of using PET aggregates as a partial substitute for natural fine-grained aggregates in Roller Compacted Concrete Pavement (RCCP) mixtures. To enhance the performance of RCCP, the mixtures were also modified by using pozzolanic Metakaolin (MK) as a partial substitute for cement and adding steel fibers obtained from the recycling of worn vehicle tires. The response surface methodology (RSM), which is capable of predicting the variations of a response value in the variations range of independent variables, was used to cover all possible mix compositions. Using this method, 20 mix designs were prepared, which allowed for significant time and cost saving in experiments without sacrificing thoroughness. The behavior and characteristics of RCCP specimens in terms of water absorption, ultrasonic pulse velocity and compressive strength at the age of 7 and 28 days were investigated. The obtained responses were used to develop statistical models, which were then utilized in the optimization of mix design with the help of analysis of variance. The results showed that the use of PET aggregates increased water absorption and decreased the compressive and flexural strength of the RCCP specimens. Partial replacement of cement with MK generally improved the performance of the specimens. The effect of shredded recycled steel fibers (SRSF) was generally dependent on other components of the mixture. The optimal mix design obtained from the statistical models involves replacing 29vol% of fine aggregate with PET, replacing 20wt% of cement with MK powder, and adding 2wt% SRSF to the mixture. The proposed mix design contributes to clean recycling of PET and conservation of natural resources and reduces the cost and carbon footprint of RCCP construction with considering the standard requirements for pavement structures.

Roller-compacted concrete (RCCP) is a zero-slump and stiff-dry mixture which is usually placed with an asphalt paver and compacted by conventional vibratory roller compactors to achieve the required density. Typically, the RCCP is constructed without joint. It needs neither forms nor surface finishing, nor does it contain bar reinforcing and dowels. Consequently, considering a proper mix design, load transfer can be achieved through aggregate interlock. Nevertheless, RCCP can be reinforced with fibers in order to improve the durability, flexural strength, load transfer capacity, and so on. Accordingly, this research was conducted to study the effects of fibers on the mechanical properties of RCCP and present a prediction fatigue model based on third-point beam fatigue test. Based on three-point bending test results on notched beam, fiber, cement, and water linearly affect the flexural strength. However, fiber tended to influence the fracture energy more significantly than flexural strength. It was found that stress ratio, fiber content and fracture energy was the significant term to predict fatigue life, respectively.

The Roller Compacted Concrete Pavement (RCCP) is dense (nearly zero slump), strong, durable and applicable for high volume concreting. Thus, in this paper compressive strength tests based on ASTM C39, water permeability tests under compression according to BS EN 12390-8 standard, total water absorption test according to ASTM C642 standard and 5% sodium-solphate test according to NDIRP (National Design and Implimentation for Road Pavements publication) 354 have been conducted. For these experiments, 24 different mix design resulted a toatl number of 504 specimens based on different DMS Ratio (disposed from Bandar-Abbas, Shahid Rajaee port). In some of these mixes polymer fibers of RCCP together with tall furnace slags of Esfahan Iron Manufacture have been used. The different perecentage of 15%, 25%, 35%, 50% and 100% of the exploited DMS with 3 different pastes of special pozzolanic portland cement, the type 2 portland cement, and the type 5 portland cement were the main target.Results of the compressive strength of the samples with the replacement of 15% of DMS show the best; this mix also shows the lowest total water absorption . Also, solphate tests were conducted in 2 cycles of 6 months old specimens as well as the one year old ones showing equal results to the original concrete units.

The development and use of roller concrete is growing in Iran. Considering the low cost of manufacturing and long life of this pavement, it is necessary to have a durable and resistant to load. Resistance characteristics and stone materials type are amongst the most effective factors in compacted concrete pavement's resistance to load. Stone materials are the most important factor in abrasive strength as they constitute more than 85% of roller compacted concrete pavement. Therefore, the current research was conducted with the aim to investigate the effect of stone material on this pavement strength. In order to investigate the material, one control stone material and four different stones obtained from debris of Choghart mine and other mines were used. The material of the aggregate used in this research includes lime stone, dolomite, calcite amphibolites, and quartz albeit. At first, in order to determine the quality of aggregate in the stone mechanical tests, including compressive strength and tensile strength, tests were done on stone materials, and then roller compacted concrete specimens were made using soil density method with grading presented code 731 and the maximum nominal size of 19 mm in order to determine the optimal moisture content. After that, the concrete specimens with optimal moisture were made in the cylinder form using density method. Compressive strength and tensile strength tests were done on hardened concrete specimens. Using quarts aggregate in this research caused compressive strength to improve by 20%. On the other hand, results showed that concrete tensile strength does not depend on aggregate material.

Every year, a large volume of waste materials are produced in the world, however a very small part of it take place in recycling and reusing. Recycled Asphalt Pavement (RAP) is a waste material which may have undesirable influence on its environment. Considering these materials reported characteristics, there have been introduced different strategies to reuse RAP’s. One of these applications recently noticed by the researchers is using RAP’s in cement mixtures such as concrete.As RAP is mainly gathered from roadsides and highways, so it is desirable to use them in common mixtures for roads pavement construction. Hence, Roller Compacted Concrete -a concrete mixture with unique features such as ease of application and low costs - was selected as basic mixture. In this research, after introducing two mixing ratios with two designing strengths, replacing a part of aggregates with RAPs was carried out in three states: 1-with fine and coarse aggregates, 2-with just fine aggregates, and 3-with just coarse aggregates, with ratios of 0, 10, 20, 40, and 80 %. Then, in the next step regression models with acceptable correlation coefficients were presented for prediction of compressive strength as well as allowable percentages of RAP aggregate to use in theconcrete. Valid using other types of RAPs was another work conducted in this research.

The large volumes of coal usage, and the low efficiency of the coal washing plants in Iran; induced a high percentage of refused coal in the production process, deposited as waste. Destructive environmental impacts stem from waste discharges into the natural environment, if it could be possible to replace this residue as a partial replacement of cement in order to produce concrete, damaging effects of this residue would be reduced. In this research, after pulverizing and conveying the grain size of regulation range of Coal Waste (CW) (of Mazandaran Central Alborz Washing Plant); this waste was replaced with 5, 10, 20 and 30 wt.% of cement in Roller Compacted Concrete Pavement (RCCP) mixture. Mechanical properties (compressive and tensile strength) of RCCP mixtures containing blended cement (composition of cement and Coal Waste Powder (CWP)) at the curing periods of 7, 28 and 90 days were investigated. Results show that 5% CWP replacement, will improve the strength properties of concrete mixtures up to 90 days, but declined compressive and tensile strengths was observed for RCCP mixture with CWP replacement content of 10% and 20% at different ages. Also, by increasing the percentage of CWP replacement, Ve-be time of mixture was declined.