Effect Of Coarse Aggregate Size Research Articles

Establishing a Balance Between Mechanical and Durability Properties of Pervious Concrete Pavement

The use of pervious concrete pavement (PCP) is significantly increasing due to reduction of road runoff and absorption of traffic noise. However, this type of pavement cannot be used for heavy traffic due to a high amount of voids and consequently low strength. This study focuses on the use of by-products as fine additives such as silica fume (SF) and fly ash (FA) for evaluating their effect on the mechanical and durability properties of PCP as an attempt to establish a balance between permeability and strength properties. The effect of coarse aggregate size, ratio of fine aggregate, specimen's size and curing periods were investigated. The results indicate that PCP provided acceptable permeability of 3.6 mm/s and 28 day compressive strength reaching to 33.0 MPa through the combination of FA and SF.

Influence of maximum aggregate sizes on the performance of RCC

The maximum aggregate size exhibits a substantial influence on many important characteristics of hydraulic concrete. This paper is dedicated to study the effects of coarse aggregate size by a series of experiments on full and triple graded Roller Compacted Concrete (RCC) mixtures, as well as experiments of full grade and wet screening on mechanics, deformation, thermotics and durability. The results show that full graded RCC with a water-binder ratio of 0.45–0.50 is acceptable for water consumption of 70kg/m3, a sand ratio of 30% and a stone combination of 20:30:30:20. The full-graded large samples had compressive strength of 10% higher than that of wet-screened small samples, with however a considerable drop in tensile strength. The large aggregate had a more obvious function of restriction and restraint to the deformation of concrete, while full-graded RCC had better volume stability. The full-graded concrete samples preceded RCC small samples in terms of frost resistance. The impact mechanism of the coarse aggregate’s maximum size mainly lied in the transformation of interface structure, and was also related to the characteristics of RCC. The full-graded RCC could further reduce the consumption of plastic materials, lower the temperature rise of hydration heat, simplify temperature control measures, reduce cracks and improve the characteristics of concrete, which is promising in both technical and economic perspectives.

Effect of Coarse Aggregate size on strength of high performance concrete

The development of new methodologies for manufacturing high performance concrete has led to massive increase in its usage worldwide. The higher strength development in concrete has increased the construction of skyscraper, bridges and special structures. Apart from higher strength and better performance the usage of this concrete also lends technical and economical viability to the entire project. The main criteria of making high strength concrete are to reduce the water content and increase the cement proportions. This however leads to reduced workability which can be overcome by the use of different mineral admixtures like rice husk ash, silica fume and fly ash apart from chemical admixtures. In our study, an attempt has been made to determine the effect of varying size of aggregate on high strength concrete using silica fume with and without fly ash. The concrete was manufactured using usual ingredients like cement, coarse aggregates, fine aggregates, water, and mineral admixture in the form of silica fume and fly ash and super plasticizer. Three sizes of coarse aggregates i.e, 10 mm, 12.5mm and 16mm with two types of fine aggregates with fineness modulus 2.65 and 2.88 were used in concrete. The percentage of silica fume and fly ash that replaced cement by weight was 7.5% and 10% respectively. It was concluded that concrete made from 10 mm coarse aggregate and with fine aggregate of fineness modulus 2.88 with silica fume showed higher compressive strength at 28 day curing.

Mechanism Study of Effect of Coarse Aggregate Size on Permeability of Concrete

The chloride penetration and capillary water absorption of concrete with different water-binder ratios (w/b) and different sizes of coarse aggregate were studied as well as the microstructure of the interfacial transition zone (ITZ). The mechanism of the size effect of coarse aggregate on the permeability of concrete was explored. The results show that the negative effect of porous ITZ in concrete with a lower w/b is more significant, while a larger size of the coarse aggregate can decrease the volume fraction of the ITZ and reduce the content of harmful pores in concrete. Based on this study, the impermeability of concrete with coarse aggregates of 0.19 to 1.00 in. (4.75 to 25.0 mm) is optimal. Conversely, the tortuosity effect of aggregate in concrete with a higher w/b becomes prominent so that aggregate that is too large can shorten the permeation path, increase the porosity and macropore content and the trend of the orientation growth of calcium hydroxide (CH) crystals in the ITZ. Under this condition, aggregate with a size of 0.19 to 0.75 in. (4.75 to 19.0 mm) is preferred.

Effect of Coarse Aggregate Sizes and Replacement Levels on the Strength of Palm Kernel Shell (PKS) Concrete

The maximum coarse aggregate size used in concrete can impact on its strength. An investigation of the effect of coarse aggregate size and replacement level of granite with palm kernel shell (PKS) on the compressive and tensile strengths of PKS concrete were investigated. Mix proportion by weight of 1:1½:2 with w/c of 0.50 were used. All samples were tested at 7 and up to 90 days. Results showed that both compressive and splitting tensile strengths increased with increase in aggregate sizes. Both strengths however decreased with increase in replacement levels of granite with PKS. Optimum replacement level of granite with PKS was 25% with compressive and tensile strengths of 22.97 N/mm2 and 1.89 N/mm2 respectively at maximum coarse aggregate size of 20 mm. However, at 50% PKS content, which results in lightweight concrete, compressive strength was 18.13 N/mm2 which is above the minimum value of 17 MPa for lightweight concrete.

Effect of coarse aggregate size and cement paste volume on concrete behavior under high triaxial compression loading

When massive concrete structures (high-rise buildings, tunnels, dams, nuclear power plants, bridges, protection structures, …) are subjected to extreme loadings (aircraft shocks, rock falls, near-field detonations, ballistic impacts, …), the material undergoes triaxial compression loading at a high confinement. In order to reproduce high stress levels with well-controlled loading paths, static triaxial tests are carried out on concrete samples by mean of a very high-capacity triaxial press. It is a well-known fact that the cement paste volume and the coarse aggregate size are two important parameters of concrete formulation. This article focuses on identifying the effect of coarse aggregate size and cement paste volume on concrete behavior under high triaxial compression. This article shows that at low confinement, the concrete strength slightly increases as the coarse aggregate size increases. At high confinement, the coarse aggregate size has a slight influence on concrete deviatoric behavior and a significant influence on concrete strain limit-state. The higher the coarse aggregate size, the lower is the mean stress level corresponding to concrete strain limit-state. Furthermore, this article highlights that at low confinement, the concrete strength significantly increases with an increase in cement paste volume. Increasing confinement tends to reduce cement paste volume effect on concrete strength. At high confinement, contrary to what has been observed in unconfined compression, the cement paste volume has little effects on concrete deviatoric behavior. Otherwise, decreasing cement paste volume increases concrete deformation capacity. At very high confinement levels and at very high deviatoric stress levels, the axial tangent stiffness of concrete increases as the coarse aggregate size or the cement paste volume is reduced.

Evaluation of fracture parameters of concrete from bending test using inverse analysis approach

In this study, an inverse analysis approach is developed to obtain the fracture parameters of concrete, including stress–crack opening relationship, cracking and tensile strength as well as fracture energy, from the results of a three-point bending test. Using this approach, the effects of coarse aggregate size (5–10, 10–16, 16–20 and 20–25 mm) and matrix strength (compressive strength of 40 and 80 MPa, respectively) on the fracture parameters are evaluated. For normal strength concrete, coarse aggregate size and cement matrix strength significantly influence the shape of σ–w curve. For a given total aggregate content, small aggregate size leads to a high tensile strength and a sharp post-peak stress drop. The smaller the coarse aggregate, the steeper is the post-peak σ–w curve. By contrast, in high strength concrete, a similar σ–w relationship is obtained for various aggregate sizes. The post-peak stress drop for high strength concrete is more abrupt than that for normal strength concrete. Also, the smaller the coarse aggregate size, the higher is the flexural strength. For both normal and high strength concrete, fracture energy and characteristic length are found to increase with increase of coarse aggregate size.

The Effect of Coarse Aggregate Size on the Stress-strain Curves of Concrete under Uniaxial Compression

In Hong Kong, concrete made with a maximum aggregate size of 10 mm and 20 mm is very popular, while little research has been conducted to investigate the effects of the maximum coarse aggregate size on the stress-strain curves of concrete under uniaxial compression. In the present study, a series of compressive tests were conducted on prismatic specimens made of normal strength concrete and high strength concrete (30 MPa - 90 MPa) with maximum aggregate sizes of 10 mm and 20 mm. Friction-reducing materials were used on the ends of the specimens to alleviate the effect of boundary constraints. The effect of the maximum aggregate size on the mechanical parameters such as the compressive strength, elastic modulus, strain at the peak stress, and the stress and strain at the inflection point were studied. Furthermore, a stress-strain model suitable for local concrete made with a maximum aggregate size of 10 mm and 20 mm was proposed.

Effect of coarse aggregate size on strength and workability of concrete

The properties of concrete were studied when the proportions of 37.5 and 19.5 mm stone in the coarse aggregate were varied. With the cement content of 160 kg/m3 and the ratio of water/cement (w/c) greater than 0.9, the compressive strength is maximum at 25 percent by weight (w/o) of 37.5 mm stone. Conversely, for the cement content of 350 kg/m3 and w/c ratios of less than 0.50, maximum compressive strength is substantively reduced. For both 160 kg/m3 and 350 kg/m3 cement contents, workability improves slightly as the proportion of the 37.5 mm stone is increased. For 100 mm fixed slumps and cement content of less than 160 kg/m3, there was little change in compressive strength as the proportion of 37.5 mm stone increased. However, when cement content was increased from 190 to 350 kg/m3, maximum compressive strength was observed, which shifted downward from 50 w/o to 25 w/o of 37.5 mm stone. In general, to maintain a 100 mm slump, water demand decreased as the proportion of 37.5 mm stone in the coarse aggregate fraction increased.Key words: concrete, compressive strength, workability, slump, aggregate, size, cement.

Effect of coarse aggregate size and matrix quality on ITZ and failure behavior of concrete under uniaxial compression

Effects of coarse aggregate size and water/cement ( w / c ) ratio of the matrix on the formation of interfacial transition zone (ITZ) and subsequently on the failure process of concrete under uniaxial compression were studied. For this purpose, a series of experiments were designed and carried out on mortars with two different w / c ratios containing single spherical steel aggregates of different sizes. The ITZ properties and the failure process of concrete were investigated through tensile strength tests both before and after compressive preloading, stress–axial strain, stress–volumetric strain and stress–lateral strain measurements. It was observed that ITZ becomes critical for larger aggregates and lower w / c ratio mortar matrices. The negative effect of smooth surface texture of the aggregate and the large difference between aggregate and matrix moduli of elasticity on the properties of ITZ is of paramount importance for low w / c ratio composites. The effect of reduced bond properties of ITZ relative to its matrix was reflected in the lower critical stress levels for the low w / c ratio composites with larger aggregates.

Effect of coarse aggregate size on interfacial cracking under uniaxial compression

The effects of aggregate type and size are important parameters in the formation of interfacial transition zone (ITZ) structure and subsequently in the failure process of concrete. The influence of surface, rigidity and size of aggregates and water/cement (w/c) ratio of the matrix on bond strength at the ITZ and the interrelationship between the bond and the matrix in the failure process of concrete under uniaxial compression were studied. For this purpose a series of experiments were designed and carried out on mortars (with two different w/c ratios) containing single spherical steel aggregates. The ITZ properties and the failure process of concrete were investigated by means of tensile and compressive strength, and stress–volumetric strain measurements. It was observed that the effect of aggregate properties (high modulus of elasticity, smooth surface texture and size) on the weakness of ITZ and the failure process of concrete are of paramount importance for low w/c ratio composites. The effect of reduced bond properties was reflected in lowered critical stress levels for the low w/c ratio composites with larger aggregates.