Amount Of Coarse Aggregate Research Articles

Laboratory and Environmental Assessment of Asphalt Mixture Modified with a Compound of Reclaimed Asphalt Pavement and Waste Polyethylene

The use of reclaimed asphalt pavement (RAP) in manufacturing asphalt concrete has become indispensable all over the world. This is due to the limited number of areas that are required to stockpile scraped pavement, as well as a lack of natural aggregate, which is necessary in manufacturing asphalt concrete. Thus, this research aims to evaluate the mechanical characteristics and environmental impact of using RAP and waste polyethylene in hot mix asphalt (HMA). RAP was added to hot mix asphalt in proportions of 25%, 50%, 75%, and 100% instead of the same amount of coarse aggregate. Then, the optimum RAP hot mix asphalt was modified by adding polyethylene in proportions of 1%, 2%, 3%, and 4% into the hot mix asphalt. The Marshall mix design was used to define the optimum asphalt content. As a final point in this experimental work, tests on the loss of stability, indirect tensile strength, and wheel loading tracking were performed to assess the performance of asphalt mixes modified with RAP and polyethylene in different conditions. A life cycle assessment (LCA) was applied using the ReCipe 2016 Endpoint method to evaluate the environmental impacts of these mixtures using the SimaPro software, V9.1. The laboratory tests showed that the mixture containing 50% RAP instead of the same amount of coarse aggregate and 2% polyethylene recorded better Marshall characteristics than the control mixture and the mixture with RAP alone. Finally, the modified hot mix asphalt with added RAP and polyethylene not only achieved superior performance in rutting, water damage resistance, and the stiffness modulus of bituminous mixtures, but it has been verified that there is no serious risk to the environment.

Studying the rheological features, mechanical properties and flexural toughness of the WSFRSCC by varying the coarse aggregate volume

The low tensile strength of concrete structures requires studying the effects of fibers on the performance of fresh and hardened concretes where finding the right amount of coarse aggregates is a challenge in the concrete industry. This study has addressed the effects of increasing the volumes of wavy steel fibers (0.15, 0.3 and 0.45%) and coarse aggregates (30, 40, 50 and 60%) on fresh concrete parameters and Self-Compacting Concrete (SCC) strength and fracture characteristics. Results have shown that using wavy steel fibers has negative effects on the properties of the fresh SCC because its efficiency and flowability are reduced, and increasing the coarse aggregate volume has positive effects because the rheological properties are improved. On the other hand, increasing the wavy steel fiber volume will improve the compressive strength in concretes containing 50 and 60% coarse aggregates. Only in 60% coarse-aggregate concretes, increasing the fiber volume from 0.15 to 0.45% will slightly reduce the wavy steel fiber reinforced self-compacting concrete (WSFRSCC) tensile strength. Increasing the coarse aggregate volume (30% – 60%) will improve the elasticity modulus of specimens with fixed percent fiber. Comparison of ASTM C 1609, JSCE SF-4 and JG/T 472-2015 methods revealed that the latter could well provide a thorough understanding of the variations of the flexural toughness of the WSFRSCC due to the demarcation of the pre- and post-peak load areas.

Effects of coarse aggregates on the mechanical properties, durability and microscopic behaviour of mortar rubble

A new type of slope protection structure, mortar rubble arch slope protection, has good low-temperature performance, and it is mostly used in the seasonally frozen area of North China. To determine the effects of aggregate type (basalt, granite, limestone) and amount of coarse aggregate on mortar rubble, mechanical properties were measured and durability experiments were conducted. Compressive strength, bending strength, mechanical damage characteristics of the materials, freeze–thaw loss rates and temperature shrinkage coefficients were recorded. The results were verified by microscopic observations. Using the digital image correlation (DIC) test system, the main form of the bending failure of the mortar rubble was observed to be failure around the aggregate. Acoustic emission parameters were used to accurately reflect the damage characteristics of the mortar rubble during the compression test. The resistance time of basalt before failure was long, and its peak energy was high. The durability test results showed that granite mortar rubble had better frost resistance, a higher freeze–thaw resistance factor, and less temperature shrinkage deformation than the basalt and limestone rubbles, and it is more suitable for slope protection in cold areas. Scanning electron microscopy (SEM) results showed that the matrix entered the pores to form new bonds, which was the main reason for the high strength of the basalt specimens. The basalt mortar rubble interface was severely damaged after freezing and thawing. The optimal amount of added aggregate was approximately 60%-70%, which resulted in good mechanical properties and durability of the mortar rubble. When the flake aggregate content exceeded 70%, the strength and durability of the material decreased.

Research studies on composition of porous concrete on the sidewalk

In infrastructure development, technology is needed that is powerful, effective, efficient in implementation time, efficient, and environmentally friendly. Porous concrete has a cavity that can flow water directly into the ground so that it can overcome the problem of water absorption. Porous concrete can be utilized in the pavement with light traffic loads such as the sidewalk. However, because porous concrete only consists of a mixture of cement, water, and coarse aggregate, porous concrete has a low compressive strength. The research is needed on the composition of porous concrete to be used on the sidewalk. Research using the ACI-522R-10 method with a variation of the ratio of cement and coarse aggregate is 1: 3, 1: 4, 1: 5, 1: 6 and cement water factor 0,30. The test results obtained the highest average compressive strength value of 16.027 MPa with an increase of 45.30% compared with no additives, as well as being in the classification of concrete brick of C quality which is suitable for the sidewalk. The results showed that an increase in the average compressive strength value along with a reduction in the amount of coarse aggregate was obtained both under conditions and with the addition of additives.

Optimisation of mixture design and surface texture for low-noise exposed aggregate concrete pavements

ABSTRACT In Korea, the transverse tining method has been applied to the surface texture of concrete pavements as it provides excellent skid resistance that improves road safety. However, transverse tining produces higher noise levels of about 4–5 dB(A) compared to asphalt pavements. Accordingly, exposed aggregate concrete pavement (EACP) is introduced since the low tyre-pavement noise and long-term skid resistance can be obtained. Surface texture of this pavement consists of coarse aggregates that are exposed after the removal of the cement mortar. Tyre-pavement noise in EACP resembles that in asphalt pavement due to the similar surface texture that is characterised by wavelength. This parameter is the distance between aggregate particles; thus, it is significantly related to the size and amount of coarse aggregate in the mixture proportion. In addition, short wavelength tends to produce low tyre-pavement noise and this can be a criterion to minimise the noise level in pavement design. Therefore, this study aims to optimise the mixture proportion of low-noise EACP based on the requirement of surface texture and structural capacity. As a result, concrete mixture with 8-mm size and 27% amount of coarse aggregate provided as short-wavelength as asphalt pavement and adequate structural strength was also achieved.

A load induced thermal strain (LITS) semi-empirical model for plain and steel fiber reinforced concrete subjected to uniaxial compressive load

A Load Induced Thermal Strain (LITS) semi-empirical model for plain and steel fiber reinforced concrete is proposed, assuming concrete as a heterogeneous 2-phase (matrix + aggregates) material. The effects of dehydration creep and the geomechanical properties decay of the coarse aggregates are taken into account separately in the model by independent parameters calibrated on the basis of the main results on plain concrete available in the scientific literature. The role of the coarse aggregates and the cement content are investigated. It was noticed that the amount of coarse aggregates is directly proportional to LITS, with a logarithmic variation. A comparison between the results of the model with experimental tests in literature, considering different types of concretes (conventional, high strength and ultra-high performance), demonstrated the reliability of the proposed model. Moreover, the model was compared with experimental tests in uniaxial compression on Steel Fiber Reinforced Concrete (SFRC) cylinders with 11-years-old, showing a reasonable approximation. The effect of concrete aging to LITS is also investigated. It is demonstrated that concrete aging is responsible for the reduction of LITS. A reduction factor β(t0) was defined on the basis of a set of experimental values ranging between 28 days and 11 years.

Effect of coarse aggregate content on shear friction of concrete

Shear friction behaviour of normal- and high-strength concretes made with different amounts of coarse aggregate was investigated in this study. A total of 48 push-off specimens were made and tested. Twenty-four of the specimens were made with normal-strength concrete; the rest were made with high-strength concrete. The test variables included the concrete strength, coarse aggregate content and amount of shear reinforcement. The results show that an increase in coarse aggregate content would increase the splitting strength of concrete cylinder, ultimate shear friction strength and shear ductility of the push-off specimens for normal-strength concrete. However, there should be an upper bound of 950 kg/m3 to ensure better ultimate shear friction strength and ductility for high-strength concretes. The same amount of coarse aggregate could be the lower bound for normal-strength concretes to achieve the code-specified splitting strength. The ACI code shear friction strength calculations are conservative. The λ modification factor for normal-weight concrete as specified in the code may be raised up to 1·3, which was the lower bound found in this study.

SELF-COMPACTING CONCRETE WITH THE USE OF PLANT WASTE

Introduction . The development of efficient self-compacting concrete is an urgent task for building materials science. A successful implementation of the task can be the use of ash of rice husk as an alternative material in the production of concrete. The aim of the research is to study the influence of the organo-mineral nanomodifier on the properties of self-compacting concrete. Materials and methods . The organomineral nanomodifier is developed using Portland cement, rice husk ash and quartz flour, which are milled together to a specific surface of 500-900 m2 /kg. Superplasticizer “Hidetal” is used to reduce the water-cement ratio. The properties of the mixture are tested for rheological characteristics. The bulk density of the samples is measured by the Archimedes method. An investigation of the concrete microstructure is carried out by electron microscopy. The compressive strength of the samples is obtained at the age of 7 and 28 days. Results . The most effective fineness of grinding of nanomodifier is 550 m2 /kg. The maximum increase in strength and the best rheological characteristics in comparison with pure thin-grained Portland cement are achieved by the introduction of a nanomodifier in an amount of 10.5%. However, the variation in the modulus of the samples’ elasticity does not reveal the dependence on the amount of nanomodifier. The modulus of elasticity of self-compacting concrete primarily depends on the amount of coarse aggregate. Therefore, the pozzolanic reaction helps to increase the compressive strength of concrete by improving the interfacial bond between the cement paste and the aggregate. Discussion and conclusions . Plant waste has the potential to be used as a replacement for Portland cement in self-compacting concrete that retains the mechanical and operational characteristics of the concrete mix and ready-mixed concrete. The surface area of the ash is increased by mechanochemical activation. The inclusion of ash led to a reduction in the workability of concrete, but with the help of an additional superplasticizer, these properties for all samples are aligned. An increase in the nanomodifier content leads to a decrease in the early physical and mechanical properties, while the final strength of self-compacting concrete containing a nanomodifier is comparable to conventional samples.

Mechanical and durability behaviour of self-compacting concretes for application in the manufacture of hazardous waste containers

In self-compacting concrete (SCC), the amount of coarse aggregates, use of fillers, and type of additives play important roles in its self-compaction, including mechanical and durability properties. The use of SCC is widespread in the precast concrete industry and it can also be employed in the manufacture of containers for the storage of hazardous waste. In addition to the requirements for self-compaction, strict mechanical and durability requirements must be considered. In this work, a study on the effect of variation in the amounts of coarse and fine aggregates, and fillers on the properties of the fresh state (self-compactability) and hardened state (microstructural, mechanical, and durability behaviours) of different dosages is carried out. The factors that have more significant influences on the density of the mixes are the presence of fillers and water-cement ratio. This is because mixes with fillers and low water-cement ratios have higher densities, which agree with the lower porosity and finer porous structure observed in mixes that incorporate fillers. Mixes incorporating siliceous fillers presented better performances in the absorption of water by immersion and capillarity than mixes without them. Measuring the depth of penetration of water under pressure in various mixes makes it possible to identify those that have high compactness and impermeability. Mixes with fillers and higher microstructural densities have lower water penetration depths. After exposure to aggressive environments, none of the mixes, with and without fillers, showed signs of wearing out or deterioration. The presence of fillers in SCCs had a more significant influence on its shrinkage than the amount of coarse aggregates. Thus, it is possible to obtain high performance SCC in relation to its mechanical and durability properties by reducing the coarse aggregate content and incorporating siliceous fillers in the dosage. Moreover, for applications where high mechanical requirements are not necessary, it is possible to produce an SCC with high performance against the attack of aggressive agents such Cl− and SO3 without using siliceous fillers.

Use of Recycled Tyre Rubber in Non-structural Concrete

To manage tyre waste and conserve natural aggregate resource, this research investigates the use of waste tyre rubber as partial replacement of fine aggregates in non-structural concrete. The research used Taguchi method to study the influence of mix proportion, water-to-cement ratio and tyre rubber replacement percentage on concrete. Nine mixes were prepared with mix proportion of 1:2:4, 1:5:4 and 1:2.5:3; water-to-cement ratio of 0.25, 0.35 and 0.40 and rubber to fine aggregate replacement of 20%, 30% and 40%. Compressive strength and water absorption tests were carried out on 100 mm cubes. Compressive strength was directly proportional to the amount of coarse aggregate in the mix. Water-to-cement ratio increased the strength within the range used in the study. Strength was found to be more sensitive to the overall rubber content than the replacement ratio. Seven out of the nine mixes satisfied the minimum strength requirement for concrete blocks set by ASTM. Water absorption and density for all mixes satisfied the limits applicable for concrete blocks. The study indicates that mix proportions with fine to coarse aggregate ratio of less than 1.0 and w/c ratio around 0.40 can be used with tyre rubber replacements of up to 30 % to satisfy requirements for non-structural concrete.

Influence of Mix Proportions on Water Absorption of RCA Concretes

The subject of the work is to develop probabilistic models defining the water absorption of concretes made ​​with the use of recycled aggregate (RCA). For the study 16 series of concrete mixtures were made with a 50 mass% share of recycled aggregate in the whole amount of coarse aggregate. The analysis of test results aimed at formulating a relationship between water absorption value and selected parameters of the composition of concretes. The objective was to find a model giving the best fit between calculated values and test results. Formulated models were then used in probabilistic modeling absorption using a Monte Carlo simulation. The results indicate a good agreement of the mean values of water absorption and possibility of good fitting of the standard deviation if an additional summand is introduced into the model.

Use of ultrasonic pulse velocity to estimate strength of concrete at various ages

This study used the ultrasonic pulse velocity (UPV) technique to evaluate the in-place strength of concrete at various ages. Both UPV and strength of concrete increase with age, and the relationship between UPV and compressive strength has been investigated for decades. Previous research results have indicated that the density of concrete is linked positively to UPV and compressive strength. It has also been found that the amount of coarse aggregate and the moisture content of concrete have a significant influence on pulse velocity, but little effect on strength. In this work, a study was carried out to develop a general relationship between UPV and compressive strength of concrete in consideration of multiple variables such as age, coarse aggregate content and moisture content. The suitability of the established relationship for estimating the strength of concrete at various ages was also evaluated. The results obtained from the verification programme carried out on a concrete plate specimen show that the effect of moisture content on UPV must be taken into account for a better estimate of concrete strength with the UPV technique.

Study on Fly Ash based Self-Compacting Concrete with Aggregate Replacements

In this article, attempt has been made to improve the performance of self compacting concrete using recycled coarse aggregate with adding of fly ash and glass fiber. Self compacting concrete has significant environmental advantages in compaction to the vibrated concrete. Absence of noise and vibrations during installing provides healthier working environment. In general, there is a scarcity of coarse aggregate throughout the world. Consumption of large amount of coarse aggregate affects the environment. For the purpose of reducing the consumption of coarse aggregate, a need for an alternative coarse aggregate arises. Recycled coarse aggregates are obtained from the demolition of buildings, culverts and also by-products from the industries. Hence, partial replacement of coarse aggregate by recycled aggregate is researched in this article, in view of consuming the ecological balance. SCC can also be used in situation where it is difficult or impossible to use mechanical compaction for fresh concrete, such as underwater concreting, cast in-situ pile foundations, machine bases and columns or wall with congested reinforcement. The self compacting concrete must meet the filling ability and passing ability with uniform composition throughout the process of transport and placing. Hence, Self compacting concrete demands large amount of powder (cementitious and pozzolanic materials) content and fines for its cohesiveness and ability to flow without bleeding and segregation. In this investigation, part of the cementitious material is replaced with pozzolanic material fly ash, and the properties of self compacting concrete in fresh and hardened states were studied. The increase of the percentage of the fly ash influences the bleeding and segregation in SCC. Hence, the addition of glass fibres can improve ductility, post crack resistance, energy absorption capacity and bleeding resistance. Taking these advantages into account a study was done. The various properties of the materials to be used in the experimental programme were determined. The specification of glass fibers and the advantages of using them along with concrete were studied. A detailed review of literature on glass fiber reinforced concrete was also done. The fresh and hardened properties of Self Compacting Concrete (SCC) using recycled coarse aggregate, fly ash with glass fibers were evaluated. The SCC mixtures are prepared with 40% of fly ash, 40% of recycled coarse aggregate and adding of 0.03% glass fiber. The strength test namely, Compressive Strength Test, Split Tensile Strength Test and Flexural Strength Test are carried out in this investigation. To test the characteristics of self compacting concrete, Slump cone test, J-ring test, L-box test were conducted to test the characteristic of self compacting concrete.

Concept of Film Thickness Applied to a New Approach for Polymer Concrete Mix Design for Airport Pavement Repair

Because of its superior ability to bond to substrate materials and its good resistance to freezing and thawing cycles, polymer concrete has been widely used for repairing airfield pavements. However, polymer concretes used in repairing airport pavements in South Korea have not lasted as long as originally predicted; this premature failure may be attributable to the incompatibility of the coefficient of thermal expansion (CTE) between the polymer concrete and the substrate concrete material. To lower the CTE of the polymer concrete, the amount of polymer must be decreased and the amount of coarse aggregates increased. To determine the optimum amounts of polymer and coarse aggregates, a new concept of film thickness is proposed. In this research, the laboratory evaluation was performed on the mixtures of polymer concrete to measure compressive strength and CTE. On the basis of these test results, it was discovered that a larger amount of coarse aggregates lowered the CTE value and increased the film thickness; these changes resulted in a higher compressive strength than that of a typical polymer concrete with fine aggregates. As expected, the CTE of the polymer concrete decreased as the amount of polymer decreased. On the basis of limited laboratory test results, a film thickness of 33.5 Μm is recommended to satisfy the minimum requirement of compressive strength (21 MPa) for repair material in South Korea. This minimum film thickness can be achieved with a mix of 8.2% polymer and 91.8% sand. However, if coarse aggregates are substituted for 40% of the sand, the same film thickness can be maintained if the amount of polymer is reduced to 6.35%.

Low-Temperature Cracking Analysis of Asphalt Pavement

Establish the mechanical model of asphalt pavement low-temperature cracking, analysis the factors leading to cracking. The factors such as shrinkage coefficient of asphalt pavementtemperature stresspavement structure combination forms and temperature contribution affect the asphalt pavement on cracking behavior. Study the effect of aggregate gradation type on asphalt mixture temperature shrinkage coefficient, analyze shows that in case of the same skeleton type, the smaller the average particle size of aggregate is, the larger low-temperature shrinkage deformation of mixture is; increasing the amount of coarse aggregate can form the dense structure of skeletonreduce the shrinkage coefficient at low temperature and improve the low-temperature crack resistance ability of asphalt mixture.

Experimental Study on Mechanics Performance of Complex High Titanium Heavy Slag Concrete

In view of the present situation that the preparation of complex high titanium heavy slag concrete (hereinafter referred to as CHTHSC) by using all coarse aggregate, fine aggregate and ground admixture made of high titanium heavy slag, is in need of experiments and studies in detail, this paper, based on the verification and analysis of structural stability of complex high titanium heavy slag and through tests of preparing CHTHSC from C10 to C55, compares CHTHSC with ordinary concrete and high titanium heavy slag concrete (hereinafter referred to as HTHSC) from three aspects of mixture amount of coarse aggregate, fine aggregate and composite powder. Results show that the compression resistance, axial compression resistance and cleavage strength of CHTHSC are higher than those of the other two kinds of concrete. For CHTHSC, it is appropriate to have composite powder take the place of 15%-20% of cement content.

Shear Behavior of Self-Consolidating Concrete Beams

This study investigates the shear behavior of beams made with different types of self-consolidating concrete (SCC). The first type of SCC (SCC1) contained a greater amount of coarse aggregate, than the second type (SCC2). A total of 24 beam specimens were tested: 8 were SCC1 beams, 8 were SCC2 beams and 8 were normal concrete (NC) beams. The parameters included the concrete strength, shear span-depth ratio (a/d), shear reinforcement strength, and spacing of shear reinforcement. Results showed that the overall performance of SCC1 beams is better than or as good as NC beams, but SCC2 beams have inferior structural performance than NC beams in many aspects. Both types of SCC beams have smaller crack widths than NC beams. SCC1 beams had higher diagonal cracking strengths and ultimate strengths than NC beams. The shear ductility of SCC1 beams is comparable with that of NC beams. SCC2 beams had less strength than NC beams. The diagonal cracking and ultimate strengths predicted by ACI 318-08 are conservative for this study. The ACI limit on design yield strength of shear reinforcement may be increased for SCC1 beams based on crack width criterion. These findings indicate that the amount of coarse aggregate can have a significant effect on the shear behavior of SCC in terms of stiffness, strength and ductility. An amount of coarse aggregate greater than 900kg/cu m (56.1 lb/cu ft) is suggested.

Characterization of the coefficient of thermal expansion and its effect on the performance of Portland cement concrete pavements

The coefficient of thermal expansion (CTE) of concrete is considered to be an important design parameter to predict Portland cement concrete (PCC) pavement performance in mechanistic-empirical pavement design guide (MEPDG). This study measured CTE values of concrete specimens having various coarse aggregates, and investigated the relationship between the CTE and critical design parameters. It was found that aggregate types, the amount of coarse aggregate, and relative humidity (RH) had a statistically significant impact on the CTE. Expansion CTE had a higher variation compared to contraction CTE, and the maximum value of expansion CTE at 63% RH was 8% higher than the value at 100% RH. Sensitivity analysis showed that inaccurate estimation of concrete CTE can cause serious error in predicting the performance of PCC pavements. A prediction equation of concrete CTE was introduced by modifying Hansen’s model and the predicted CTE value had a good agreement with the measured CTE.

The fragmentation of cementitious composites in a jaw breaker

The paper reports about the fragmentation of cementitious composites in a laboratory jaw breaker. Two types of cement paste and six different concrete materials were investigated. Specific fragmentation energy and size distributions of the generated fragments were estimated. A microscopic inspection of the debris was also performed. Specific energy has values between 5 and 10 J/g. It is highest for a concrete with high porosity and lowest for a mortar. It is also found that the specific fragmentation energy depends on the amount of coarse aggregates in the material. Based on these findings, the specific fragmentation energy is linked to a brittleness parameter of the concrete materials derived from non-linear fracture mechanics. A detailed SEM-study showed features of non-linear fracture, namely crack branching, aggregate bridging, and pore–crack interaction. It was further found that a Rosin–Rammler–Sperling distribution best describes the size distribution of the generated fragments, except the mortar. An approximate estimation of the strain rate during the fragmentation was performed, and a value of ε ̇ =1.41×10 3 s −1 was calculated for concrete.

1053 詰め方によるコンクリート中の粗骨材量の変動(材料・施工)

1053 詰め方によるコンクリート中の粗骨材量の変動(材料・施工)