Maximum Size Of Coarse Aggregate Research Articles

Bamboo‐reinforced self‐compacting concrete beams for sustainable construction in rural areas

The use of bamboo as longitudinal reinforcement, coupled with the application of self‐compacted concrete (SCC) in the construction industry, may be a promising solution to issues involving sustainable development in developing countries. This study seeks to investigate the flexural performance of bamboo‐reinforced SCC beams with adequate transverse reinforcement. The major design parameters were the shear span‐to‐depth ratio, the percentage of longitudinal reinforcement, and the maximum size of coarse aggregate. The load–deflection curves, serviceability and ultimate failure characteristics, cracking behavior, and ductility measures were evaluated and discussed among tested beams. Results indicated that their structural performance at service and ultimate failure would be adequate when a material reduction factor of three is used with BS 8110 design code. However, to achieve maximum ductility, the level of longitudinal reinforcement should be in range of 2.6–3.1%. Furthermore, an increase in the size of coarse aggregate will greatly impact the degree of ductility.

Influence of formwork material on transport properties of self-consolidating concrete near formed surfaces

This study aims at determining the influence of the formwork material on transport properties of concrete cover when using self-consolidating concrete (SCC). Two types of formwork were used. The plywood (PW) formwork material which is relatively rough and absorbent compared to the PVC material that has a very smooth and non-absorbent surface. A total of 17SCC and highly flowable concrete mixtures with wide range of slump flow and T50 values were investigated. The concrete was used to fill 400×500×200mm3 moulds made with either PVC or PW. Sorptivity tests were performed on core samples (100mm in diameter and 50mm in length) taken from the sides and center of the prepared moulds after 28days of moist curing. This paper presents new experimental method using image analysis to quantify the relative surface area of coarse aggregate along different sections near formed surfaces. Sorptivity of concrete near the surface cast against the PW formwork was found to be significantly lower than that of PVC one due to the decrease of local w/c and wall effect. The examination of packing density of coarse aggregate near PVC and PW surfaces showed limited wall effect near the PVC formwork and significant wall effect within a thickness comparable to the maximum size of coarse aggregate near the PW formwork.

EN 206 Conformity Testing for Concrete Strength in Compression

Concrete strength in compression is the common characteristic used in the design of concrete structures. However, in general, there are two different types of concrete specimens specified for the determination of concrete strength in compression. They are the standard 150mm diameter by 300mm length cylinders and the standard 150mm cubes. In the case where the maximum size of coarse aggregate is less than 40mm (1½ in.), 100mm diameter by 200mm length cylinders and 100mm cubes may be adopted. Cylinder specimens with aspect ratio (length/diameter) of 2 are likely to be closer to the uniaxial compressive strength as end friction effects at the platens tend to induced a more complex state of stress compared to that of a cubical specimen with aspect ratio of unity. Hence, the two types of test specimens do not provide the same measured strength for the same concrete. For the purpose of conformity testing, the consistency of test results is of greater interest than the magnitude of the measured strength of the concrete specimens. This paper reviews the issues concerning the two types of specimens, (cylinder or cube) and the size of the specimen in relation to maximum size of coarse aggregate used. Some experimental data for compressive strength at 3 strength classes for which slightly over 100 batches produced over several consecutive calendar months were tested. Three types of specimens, 150mm diameter by 300mm cylinders, 150mm cubes and 100mm cubes were adopted for testing at the age of 28- days. Maximum size aggregate of 20mm and CEM I cement were used for strength classes of C32/40, C50/60 and C65/80 achieved with added silica fume. The findings of these test regimes are summarised with recommendations for conformity testing based on EN 206 and its complementary British Standard BS 8500.

Investigation of the rebound number and compressive strength of concrete with quarry dust as fine aggregate

This article presents the consideration of relation between compressive strength and rebound number of concrete cooperating with quarry dust as fine aggregate (natural river sand was replaced by quarry dust at the rate of 0%, 25%, 50%, 75% and 100% by weight of fine aggregate). The properties of the tested concrete samples are w/c = 0.6, maximum size of coarse aggregate is 20 mm., cement contents are between 308 and 348 kg/m 3 , slumps range from 0 to 100 mm., the 28-day compressive strength from 14 to 30 MPa. It was found that the rebound number results were affected by quarry dust especially the standard deviator of rebound number. The cube compressive strength at 28 days and the supplementary curve from the instruction manual were discussed. Moreover, the prediction equation is proposed to estimate the compressive strength of concrete cooperating with quarry dust as fine aggregate.

Experimental study of equal biaxial-to-uniaxial compressive strength ratio of concrete at early ages

The ratio of equal biaxial to uniaxial compressive strength of concrete, denoted as β, is an important parameter in the determination of failure criterion for concrete, which has been widely adopted in finite element codes in simulation of fracture and failure of concrete. However, there is no experimental study on β conducted for concretes at early ages. In this study, an experimental study on the uniaxial and equal biaxial compressive strengths of concretes at early ages up to 28days was carried out using an in-house electro-hydraulic servo-controlled triaxial test machine. Concrete specimens with different coarse aggregate sizes (10mm, 20mm, 30mm) and strength grades (C30, C40, C50) were tested at various ages (6h, 12 h, 1d, 3d, 7d, 14d, 28d). The results showed that β decreases with the increase of concrete age. In comparison, there are less significant effects of concrete strength and maximum coarse aggregate size on β. By regression analyses of experimental results, an empirical equation was proposed for β by considering the effects of age on β for concrete at early ages.

A fundamental study on compressive strength, static and dynamic elastic moduli of young concrete

This study investigates the influence of volume content of aggregates, maximum size and type of coarse aggregates, water-to-cement ratio and curing temperature on mechanical properties, i.e. prismatic compressive strength (fc), static modulus of elasticity (Ec) and dynamic modulus of elasticity (Ed) of concrete at early age. A new equation is proposed to correlate prismatic compressive strength and elastic moduli of concrete. Based on the experimental data and the analysis results, the Ec–Ed relationship is also proposed. It is found that the relationship between Ec and Ed is linear, and the coefficients of linear relationship are analyzed by multiple regression analysis, considering aggregate content, maximum size of the coarse aggregate, water-to-cement ratio and curing temperature. It is found that the volume content of aggregates is the most significant factor that influences the Ec–Ed relationship.

전단보강이 없는 순환골재 콘크리트보의 크기효과에 대한 실험적 연구

The authors examined the size effect of reinforced concrete(RC) beams using natural coarse aggregates and recycled coarse aggregates. The specimens were made of concrete with a maximum coarse aggregate size of 20 mm. In this study, depth-to-width ratio, shear span-to-depth ratio, tension steel ratio and RCA replacement ratio were fixed 1.5(i.e., h/b=1.5), 3(i.e., a/d=3), 1.2%(i.e., ) and 30%(i.e., ) respectively. The test variables only include the RC beam size and aggregate type. A total of 10 simple RC beams were tested under four points loading. It has been shown that shear strength decreases as member size increases. This is associated with a phenomenon called size effect. However, the size of the RC beams does not seem to affect the shear strength proportionally. Besides, test results were analyzed and then compared with the findings and various shear design equations. To conclude, the shear equations reflect relatively well with most of experimental data.

Mix Proportion Design and Mechanical Properties of Recycled PET Concrete

Abstract The mix proportion and mechanical properties of polyethylene terephthalate (PET) concrete were studied by orthogonal test. PET concrete was produced by mixing melted PET with aggregate and mineral admixtures. The effects of several factors on the properties of PET concrete were investigated. These factors included: (1) coarse aggregate type, (2) mineral materials, (3) PET and mineral/aggregate (PETAM/AG) ratio, (4) sand ratio, (5) PET/mineral (PET/MA) ratio, and (6) maximum particle size of coarse aggregate. The results showed that the most important factor was PETAM/AG, followed by sand ratio and PET/MA. Samples with 10 mm coarse aggregate had the highest compressive strength of 36 MPa. The compressive strength decreased 8.6 and 37 % as the coarse aggregate maximum particle sizes changed from 10 to 4.75 and 13 mm, respectively. There was no significant difference in flexural strength when the sand ratio changed from 35 to 68 %. The strength of PET concrete with basalt was higher than that of concrete with limestone. The concrete containing fly ash and 5 % talc had the highest strength followed by concrete with fly ash, Portland cement (PC), fly ash with 5 % asphalt, without any mineral. The best mix proportion of PET concrete was PETAM/AG of 1:3, sand ratio of 35 % and PET/fly ash of 2:1.

A comprehensive investigation into the effect of aging and coarse aggregate size and volume on mechanical properties of self-compacting concrete

The popularity of self-compacting concrete (SCC), as an innovative construction materials in concrete industry, has increased all over the world in recent decades. SCC offers a safer construction process and durable concrete structure due to its typical fresh concrete behavior which is achieved by SCC’s significantly different mixture composition. This modification of mix composition may have significant effect on the hardened mechanical properties of SCC as compared to normal vibrated concrete (NVC). Therefore, it is necessary to know whether the use of all rules and relations that have been formulated for NVC in current design codes based on years of experience are also valid for SCC. Furthermore, this study represents an extensive evaluation and comparison between mechanical properties of SCC using current international codes and prediction equations proposed by other researchers. Thus, in this experimental study, major mechanical properties of SCC are investigated for twelve SCC mixes with wide spectrum of different variables i.e. maximum coarse aggregate size, coarse aggregate volume and aging. In the present study, an extensive body of data reported by many researchers for SCC and NVC has been used to validate the obtained results.

Evaluation of the effect of maximum aggregate size on fracture behavior of self compacting concrete

This paper presents and discusses the effect of maximum size of coarse aggregate on fracture characteristics and brittleness of self-compacting concrete (SCC). Based on an experimental program, a series of three point bending tests were carried out on 86 notched beams, as recommended by RILEM. For all mixes, the parameters were analyzed by the work-of-fracture method (WFM) and by the size effect method (SEM) and consequently a correlation between these methods was obtained which is used to calibrate cracking numerical models. Test results showed that with increase of size of coarse aggregate, (a): fracture energies of GF in WFM and Gf in SEM increase which may be explained by the change in fractal dimensions, (b); based on size effect plot, behavior SCC specimens approaches strength criterion, (c): SCC ductility, measured by means of characteristic length (Lch) in WFM and fracture process zone length (Cf) in SEM, increases. In addition, the correlation between GF and Gf values showed that the ratio GF/Gf is approximately equal to 2.94.

High-rate tensile behavior of steel fiber-reinforced concrete for nuclear power plants

The direct tensile behavior of fiber-reinforced concrete (FRC) at high strain rates were investigated for their potential to enhance the resistance of the containment building of nuclear power plants (NPPs) against aircraft impact. Two types of deformed steel, hooked (H) and twisted (T) fibers were employed. To improve the tensile resistance of FRCs even at higher rates by adding more fibers, the mixture of concrete was modified by either increasing the sand-to-coarse aggregate ratio or decreasing the maximum size of coarse aggregate. All FRC specimens produced two to six times greater tensile strength and one to five times higher toughness at high strain rates (4–53s−1) than those at a static rate (0.000167s−1). T-fiber generally produced higher tensile strength and toughness than H-fiber at both static and high rates. Although both fibers showed favorable rate sensitivity, T-fiber produced much greater enhancement, at higher strain rates, in tensile strength and slightly lower enhancement in toughness than H-fiber. As the maximum size of coarse aggregate decreased from 19 to 5mm, the tensile strength and toughness of FRCs with T-fibers noticeably increased at both static and high strain rates.

Influence of fiber grid on interlayer bond property of airport double-layer pavement

In order to study the interlayer bond property of airport double-layer pavement, the cement concrete cube splitting tensile test and double-layer beam test were conducted. The bond mechanism of fiber grid and airport double-layer pavement was analyzed. The deflection and strain of upper and lower beams of double-layer beam were measured. The splitting tensile strength of new and old cement concrete cubes, the strain ratio, deflection difference and coupling coefficient of the double-layer beam were taken as criteria for the interlayer bond property of airport double-layer pavement. The result demonstrates that the splitting tensile strength is maximal when the basalt fiber grid with dimension of 5 mm was adopted, the old cement concrete and fiber grid surface treatment have great influence on splitting tensile strength, but the maximum grain size of coarse aggregate have few influence on it. The friction between double-layer beam reduces the strains of the bottom of the lower and upper beams by 44.44–98.46%. The fiber grid and old cement concrete surface treatment not only increase the coupling coefficient with the range of 4.60–15.73% but also decrease the deflection difference, the number of which ranges from 0.004 mm to 0.016 mm, thus improve the integral force performance and deformation ability of double-layer beams.

Compressive strength model for concrete

A predictive compressive strength model accounting for the type of cement, cement degree of hydration, aggregates type and gradation, mixtures proportion and air content was developed. This paper presents the formulation, implementation, calibration and validation of the proposed strength model for normal concrete. The theoretical formulation postulates that particles' interaction is governed by excess paste theory from which an average paste thickness model is developed to account for concrete mixture proportions and aggregate gradation. In addition, the model accounts for the cement compressive strength and aggregate to cement paste bond strength. An experimental programme, developed to evaluate the model, accounts for the following variables: water to cement ratio, water content, bulk volume and maximum size of coarse aggregate, and air content. The proposed model is found to accurately predict the strength of concrete mixtures at 3, 7, 28 and 191 days. The measured 3-day and 28-day strength range from 8·5 to 32·7 MPa and from 13·6 to 43·8 MPa, respectively. The corresponding standard error and correlation coefficient for the 3-day predictions are 2·1 MPa and 0·95, and 1·8 MPa and 0·96 for the 28-day predictions.

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.

Experimental Research on the Influence of Grain Size of Coarse Aggregate on Pebble Concrete Compressive Strength

To discuss the influence of coarse aggregate size, water cement ratio and ages on the concrete compressive strength，the compressive strength tests were carried out by 54 cubic specimens of pebbles concrete in dimensions of 150mm, 18 cubic specimens with dimensions of 200mm and 72 specimens with size of 150mm×150mm×300mm. The results show that the maximum size of coarse aggregate rises with the decrease of the concrete compressive strength; Concrete compressive strength of coarse aggregate size affects more apparently as the ratio of water-cement decrease; with the increasing of age, concrete compressive strength of the aggregate size effect has no significant changes.

Prediction of compressive strength of concrete using neural networks

This research deals with the prediction of compressive strength of normal and high strength concrete using neural networks. The compressive strength was modeled as a function of eight variables: quantities of cement, fine aggregate, coarse aggregate, micro-silica, water and super-plasticizer, maximum size of coarse aggregate, fineness modulus of fine aggregate. Two networks, one using raw variables and another using grouped dimensionless variables were constructed, trained and tested using available experimental data, covering a large range of concrete compressive strengths. The neural network models were compared with regression models. The neural networks based model gave high prediction accuracy and the results demonstrated that the use of neural networks in assessing compressive strength of concrete is both practical and beneficial. The performance of model using the grouped dimensionless variables is better than the prediction using raw variables.

Influence of Coarse Aggregate Size on Softening Curve of Concrete

The program by Fortran to determine softening curve of concrete by inverse analysis was developed based on the wedge splitting test and Fictitious Crack Model (FCM). The four-linear softening curves were obtained by the inverse analysis program for the wedge splitting (WS) specimens which size are all 200mm×300mm×300mm with different coarse aggregate size. The approach of refining element mesh was presented for the inverse analysis calculation. It is shown that the three control parameters of softening curve, which are the tensile strength ft, maximum crack width wc and fracture energy GF, increase with increase of the maximum coarse aggregate size dmax.

고온을 받은 초고강도 콘크리트의 역학적 특성에 관한 골재의 영향

콘크리트 구조물은 화재에 노출시 고온에 의해 내부 구조가 변화하며 보유하고 있는 강도와 변형 성능이 저하되어 최종적으로 수명이 단축하게 된다. 그 성능 저하 수준은 도달된 온도, 고온에 노출된 시간, 콘크리트의 배합, 골재의 특성 및 콘크리트 자체의 특성 등에 의해 결정된다. 이 연구는 물시멘트비, 잔골재율 및 굵은 골재의 최대 크기 등의 변수에 대한 초고강도 콘크리트의 열적 거동을 평가하기 위해 실시되었다. 상온 및 500℃의 온도에 대하여 초음파 속도, 동탄성 계수, 정탄성 계수 및 압축강도 시험은 ?100 × 200 mm 원주형 콘크리트 시험체를 사용하여 실시되었다. 결과로서 500℃의 온도에서 가열된 초고강도 콘크리트의 잔존 역학적 특성은 물결합재비, 잔골재율 및 굵은 골재 최대 치수의 변화에 영향을 받는 것으로 나타났다.

Alternative Method for Concrete Structures Compressive Strength Estimation with Small-Scale Destruction

To estimate a compressive strength from existing concrete structures by core drilling are usually gathered with a diameter specimen of 100 mm or three times of maximum coarse aggregate size and examined by uniaxial compressive strength (UCS). It is relatively difficult to gather a large sized core, and a pit place will be limited by main members. To get an alternative solution with smaller specimen, point load test (PLT) has been selected which is a simple test and widely accepted in rock materials research, but relatively new in concrete. The reliability of PLT is evaluated by extracting a lot of core drilled specimen from ready mixed concrete blocks with maximum coarse aggregate size, Gmax of 20 mm in representative of architectural structures and 40 mm in representative of civil structures on the range of concrete grade from 16 to 50. Compressive strengths were classified into general categories, conversion factors were determined, and scattering characteristics were also investigated. The relationship between point load index (IS) and compressive strength of concrete core specimen (f'cc) can be written as linear approximation as f'cc = k.IS - C.

The Effect of Coarse Aggregate on Fresh and Hardened Properties of Self-Compacting Concrete (SCC)

Self Compacting Concrete (SCC) is new type of concrete that posse's property of high flow ability, passing ability and stability. To achieve SCC, many factors must be investigated. Coarse aggregate is one of these factors that have a significant influence on SCC. This paper presents the coarse aggregate properties such as maximum size, texture and type of coarse aggregate that have a direct effect on achieving SCC. Three types of coarse aggregate are used, namely crush gravel, uncrushed gravel and crush limestone. To determine the workability, different test methods are adopted such as slump flow, V-funnel, L-box and U-box test. It was found that by increasing the maximum size of coarse aggregate, flowability and passing ability reduced. In addition it was observed that when uncrushed gravel was used in the concrete mixture, flow ability, passing ability and segregation resistance increased as compared to concrete with crushed gravel. Furthermore, the inclusion of 10% HRM as a partial replacement by weight of cement leads to reduce flow ability and increase viscosity. The compressive and flexural strengths and modulus of elasticity was measured. It was noticed that concrete mixes prepared with crushed limestone showed higher strengths and modulus of elasticity than concrete mixes prepared with crushed and uncrushed gravel. In addition, lower maximum size of coarse aggregate leads to higher strengths compared to higher maximum size of coarse aggregate in SCC mixes.