C30 Concrete Research Articles

Erosion-Resisting Characteristics of Concrete under Freeze-Thaw Action

Erosion-resisting characteristics of C25C35 and C50 concrete are tested in an environment of freezing and thawing cycle. The result shows that the corrosion becomes more and more serious under clear water, the liquor of sodium sulfate, the liquor of sodium sulfate and sodium chloride after 300 freeze-thaw cycles. This kind of phenomenon also happens when the water cement ratio becomes increasingly bigger. The concrete samples which are protected by SPUA (Spray Polyurea Elastomer) are in good condition. The main problem is spalling from surface to interior, which shows different tendency in different salting liquid.

Anti-strike Capability of Steel-fiber Reactive Powder Concrete

Penetration and contact explosion tests on reactive powder concrete (RPC) containing 5 per cent steel-fiber were carried out to investigate the anti-strike capability of steel-fiber reactive powder concrete (SFRPC). The penetration tests consisted of two sample groups corresponding to hit speeds 308 m/s - 582 m/s and 808 m/s - 887 m/s, respectively. The contact explosion tests were carried out in an explosion test pit using TNT with charges in the range 0.5 kg - 3.0 kg. The tests results show that the anti-strike capability of SFRPC targets is much better than ordinary C30 concrete. The penetration depths of the SFRPC targets were less than half those evaluated values of the C30 concrete targets. The areas of the blasting funnels and the explosion cavity radii in the SFRPC plates are also much less than the calculated results in ordinary C30 concrete, being about one quarter of those of the latter. Defence Science Journal, 2013, 63(4), pp.363 -368 , DOI:http://dx.doi.org/10.14429/dsj.63.2407

Experimental Study of the Performance of C60 Pavement Concrete

Abstract: In order to improve the surface standard of the mine heavy vehicle road, on the basis of laboratory studying in C60 concrete, the performance of the C60concrete in pavement construction will be researched, and frost resistance, carbonation resistance and creep performance variation were analyzed. The results showed that mixed with silicon powder and slag powder, under the condition of lower amount of cement，The test of C60 pavement concrete structural compactness，mechanical properties and durability indicators could satisfy the design requirements；As the number of freeze-thaw cycles went up, the rate of strength loss and mass loss of the test pavement concrete increased linearly；The carbonized value increased significantly, in 7 days; growthed significantly slowed in the range of 7 days -28 days; The creep strain value increased linearly during the period of 100 days, changes leveling off after more than 100 days of age, and creep strain values stabilized.

Temperature Control Research on Spiral Case Concrete of Xiluodu Underground Power Plant during Construction

The volume of concrete surrounding the spiral case increases along with the increase of unit capacity of single-unit hydroelectric station. Once the spiral case concrete structure works with crack, its bearing capacity and safety stability will decrease seriously. Owing to the action of contraction stress induced by temperature variation, the spiral case concrete is often subject to cracking. There are a few temperature control researches on spiral case concrete during construction in the past, more severe, there are few researches on the sensitivity analysis of parameters and measures on temperature control. For this reason, based on the finite element analysis software ANSYS, the spiral case concrete of Xiluodu underground power plant is simulated. The temperature field and temperature stress field of different pouring temperature and concrete strength are analyzed and the temperature control measures with normal C30 concrete and 293.15K casting are recommended to prevent cracks accordingly. These measures, adopted by construction units are proved to be effective and also good references for similar projects.

Influence of the Type of Strain Measurement Device and of the Speed of Loading and Unloading of the Testing Machine in the Determination of the Static Modulus of Elasticity of the Concrete

This paper presents a comparative analysis of the results obtained for testing the tensile modulus, through a collaborative program of tests on hardened concrete, developed at the School of Civil Engineering, Federal University of Goias, in the Department of Technical Support and Control of Furnas central Electric Company SA and Carlos Campos and Construction Consultancy Limited., to identify and assess the influence of some factors involved in the test results the elastic modulus. This test was performed according to ABNT NBR 8522:2008, loading plan initial tangent modulus characterizing the deformation of concrete subjected to the stresses of 0.5 MPa and 30% of the breaking load. For this, we sought to determine the outcome of the module, the influence of strain gauge (compressometro mechanical, electrical bonding surface extensometer extensometer and electric external fixation) and rate (0.3 and 0.6 MPa/s) bodies on the test piece cylindrical size 150 mm x 300 mm C30 concrete class. We performed 60 trials considering the results with satisfactory performance in the statistical techniques of the program. It was concluded that the strain gauge type of load and speed significantly influenced the results of elastic modulus. Moreover, it is noteworthy that the bodies of the test piece size 150 mm x 300 mm concrete Class C30, tested with loading speed of the testing machine of 0.3 MPa/s presented the results with the highest dispersion. Keyword: Meter, Speed; Module; Concrete; Dispersion.

Usage of Iron Mine Tailing Sand on Concrete

Two iron mine tailing sands and manufactured sands with different fineness modulus are studied and they are mixed into four mixed sands which fineness modulus is 2.6~3.0 by controlling mixing amount of iron mine tailing sand. The influence of mixed sands on workability and strength of C30 and C50 concrete are studied. The result shows that C30 and C50 concrete slump can reach 170mm. Concrete workability is good and strength is qualified too. Fineness modulus is the most important performance index when iron mine tailing sand is used in concrete.

Development of a loading platen containing a cylindrical roller bearing to reduce frictional constraint at the boundary

This paper presents an experimental assessment of the influence of the boundary conditions and geometry of the specimen in unconfined compression tests, employing two concrete types. For such purposes, an experimental program was designed, dividing the samples into cylinders with height h = 20 cm and diameter b = 10 cm, prisms with height h = 20 cm and square 10 cm base and 10 cm sides cubes. Concrete traces resulting in 50 MPa (C50) and 30 MPa (C30) nominal strengths were used. The compression tests were carried out under five different boundary conditions on the loaded planes: Grease, Teflon and Brush plate, as anti-friction means. For reference, standard tests and increasing the lateral restraint employing Glued sheets, in order to maximize the interface friction, were also performed. The strength difference between height/base ratios (h/b) = 2 and (h/b) = 1 prisms varies on average from 15% for C50 and 35% for C30 concretes. No significant difference was found between cylindrical and prismatic specimens with the same h/b ratio. In specimens provided with anti-friction devices, the strength variation for the different geometries and h/b ratios was almost totally eliminated, as well as the post-peak softening of the tests. The reported results prove that the post-peak softening is not a characteristic of the material but a consequence of the interface friction in the tests. Cubic specimens provided with grease to eliminate friction led to the same compressive strength than cylinders or prisms with the same cross-sectional area and therefore offer the unquestionable advantage of allowing the assessment of the influence of the orientation of casting.

Freeze‐Thaw Durability of Air‐Entrained Concrete

One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to “the test method of long-term and durability on ordinary concrete” GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results.

Performance of steel reinforced high strength concrete investigated in the gas gun experiment

The shock properties of C100 concrete are investigated by gas gun planar impact technique. The manganin pressure gauge is used to measure the pressure-time curves of the samples. The physical quantities are all obtained by the Lagrange method. Moreover, it is observed from the measured pressure-time curves that the decay factor is smaller in the steel reinforced high strength concrete. The dynamic response is analyzed.

Experiment for the Mix Proportion Design of Green and Self-Compacting C40 Concrete

The self-compacting concrete is playing more and more important role in the construction industry with the advantages of greater mobility, better stability, and excellent character of filling the gap through capacity. There are different raw materials and construction conditions in each region, so, the research and development of the self-compacting concrete has a special significance according to the specific circumstances of each region. In this study, the parameters of the volume of coarse aggregate, mortar volume, the volume fraction of the sand, the mineral admixtures ash and cementatious coefficient were selected and calculated, and the C40 self-compacting green concrete was successfully configured.

Effect of Ground Waste Concrete Powder on Cement Properties

The paste/mortar attached to the recycled aggregate decreases the quality of the aggregate and needs to be stripped. The stripped paste/mortar is roughly 20% to 50% in waste concrete, but relevant research is very limited. In this paper, the effects of ground waste concrete (GWC) powder, coming from the attached paste/mortar, on water demand for normal consistency, setting time, fluidity, and compressive strength of cement were analyzed. The results show that the 20% of GWC powder (by the mass of binder) has little effect on the above properties and can prepare C20 concrete; when the sand made by waste red clay brick (WRB) replaces 20% of river sand, the strength of the concrete is increased by 17% compared with that without WRB sand.

Study on Failure Criterion and Yield Criterion of Early-Age C20

The early-age concrete properties are the basis for structure nonlinear analyzed under construction structure period. But at present the study on early-age concrete is lagging behind which there is not suitabel theory. This paper takes early-age C20 concrete as an example to analysis the early-age concrete properties. According to the distribution characteristics of early-age C20 concrete experiment data in the octahedral stress space, using section function expression form, by the method of mathematical derivation and linear fitting, the failure criterion and the elastic yield criterion of early-age C20 concrete materials in the octahedral stress space are established. By comparison between failure criterion and elastic yield criterion of C20 concrete, the subsequent yield criterion could be derived based on the non-uniform isotropic strengthening criterion.

Experimental Study of the Tensile Bond Strength in Concrete Aggregate - Paste Interfacial Transition Zone

Study on the characteristics of tensile bond strength in concrete interfacial transition zone. Calculate the tensile bond strength of interfacial transition zone in concrete by the way of vertical drawing cobblestones of different grain size from C30 concrete by MTS hydraulic loading system .(the grain size include 50,70,90,100mm) results show that:1.when the cobblestones diameter is in a certain range(<90mm in this experiment)or the bonded area is in a certain range(<5251 mm2 in this experiment), The tensile bond strength of concrete interfacial transition zone nothing to do with the cobblestones diameter and the bonding area.2.If the cobblestones diameter or the bonded area is too large, it will affect the bonding effect of the cobblestones and concrete, and cause the depression of tensile bond strength, Therefore , In the actual engineering we should avoid the use of large diameter cobblestones .3. The tensile bond strength of C30concrete interfacial transition zone is approximately 4% - 10% of compressive strength of concrete.

Numerical Simulation Used for High Strength Concrete under Impact Loading

The process of concrete under symmetric impact was experimentally investigated in the case of primary gas gun and was analyzed .The shock properties of C100 concrete is investigated by gas gun planar impact technique. The manganin pressure gauge is used to measure the pressure-time curves of the samples. The parameters of high-pressure equation are obtained by the numerical simulation. Numerical simulation is a necessary complement to the test. The spall phenomenon is observed by the numerical simulation.

Influence of Air Content on the Compressive Strength of Concrete

The influence of air content on compressive strength of C20，C30，C40 and C50 concrete was investigated in this paper. The result shows that this relationship varied with concrete strength grade. For C20~C40 concrete, the air content increases with addition of air entraining agent, while a maximum air content value appears for C50 concrete. The compressive strength of C20 decrease slightly with the air content, on the other hand, that of C40 significantly decreases relatively.

Experimental Study on Quality Control of Moderate-Strength Commercial Concrete

For the quality control of commercial concrete, it is important to choose correct raw- material and mixture ratio. C40 and C50 concrete were prepared in dry and cold climate environment, using local raw materials and a large amount of fly ash. Specific researches were made about different kinds and dosage of superplasticizers on the slump of concrete, slump loss and the intensity of the impact. The results show that naphthalene series superplasticizer JK-2 and 30% of fly ash can ensure that slump of the mixture concrete reach more than 180mm, slump loss is less than 30mm in an hour, strength of hardened paste will not be reduced, and concrete can be prepared with low costs.

Effect of Surface Applied Inhibitor on Corrosion Rate of Steel Bar in High Strength Concrete with Various Admixed Chlorides

Effect of surface applied inhibitor on the durability of high strength reinforced concrete with various chloride content has been investigated in this paper. The C60 concrete specimens contaminated with 0.5%,1.0%,1.5% NaCl by mass of the cementitious materials were prepared and experienced in months exposure tests after painting with 400 g/m2 inhibitor. The electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) of the steel rebar in specimens was tested. The results indicate that after surface painting the inhibitor for 28d the bars in concrete specimens with 0.5% NaCl and bar with 25mm cover in specimen with 1% NaCl show the average corrosion rate lower than that of control one (No.0, no painted inhibitor). While the corrosion current of rebar (38mm cover) for No.2 specimen with 1% NaCl and bars for No.3 specimen with 1.5% NaCl are still higher than that of the control one (No.0). The results indicate that the surface painted inhibitor on C60 concrete are effective to inhibit the corrosion of bar concrete at low or middle chloride conditions and not enough to repair the bars in high chloride contaminated concrete. The lower organic nitrogen content in 40-50mm depth also indicates that the inhibitor is harder to penetrate into deeper parts of high strength concrete compared with low or middle grade concrete.

Thermal Fatigue Performance of Steel Fiber Reinforced Polymer High Strength Concrete

To discover the fatigue behavior and durability of the new type fiber concrete named “steel fiber reinforced polymer high strength concrete (SFPHC)”, considering climatic conditions in Guangdong Province, using research method of theoretical analysis combined with experimental study, thermal fatigue behavior of SFPHC used in bridge superstructure in three different temperatures (20°C，50°C，80°C) is discussed and compared with concrete C60 which has similar static mechanical properties at room temperature. The results show that the thermal fatigue performance of SFPHC can be described effectively with the proposed computing formula, and the fatigue performance has been greatly enhanced compared with the C60 concrete.

The Study on Chloride Corrosion of Concrete Containing Admixture Mineral

Chloride ions were harmful to the performance of the concrete.Admixture mineral had been replaced part of cement in high performance concrete to improve the durability and chloride resistance of the concrete.In this paper,the compressive strength of the concrete with admixture mineral and without admixture mineral had been measured cured after 28 days. The results had been shown that the compressive strength of the concrete without admixture mineral is lower than the one with admixture mineral after 28ds’and 56ds’ immersing in 5%NaCl solution. The quantities of electricity through the concretes with 30% admixture mineral were lower than the benchmark concretes. The current of C30 and C40 concretes with admixture mineral was lower than the benchmark concretes.The concrete with admixture mineral had been eroded lower than the one without admixture mineral.

Behaviour of inclined, tapered and STS square CFST stub columns subjected to axial load

This paper describes the finite element method using ABAQUS to model the axial compressive behaviour of inclined, tapered and straight–tapered–straight (STS) concrete filled steel tubular stub (CFST) columns with square hollow sections. The accuracy of the numerical model was verified by comparing the numerical predictions with experimental study of the 200×200×3.75 RHS filled with C60 concrete with inclined angle of 0–9° and tapered angle of 0–4°. The results show that the compressive behaviours, load vs. strain relationship and failure mode predicted by the numerical simulations were agreeable with experimental results. After the validation, a parametric study was performed with 3 typical steel hollow sections (200×200×3.75 RHS, 300×300×6.3 RHS and 400×400×8.0 RHS) and extended the inclined angle and tapered angle to 0–15° and 0–12° respectively. The parametric study highlights some of the behaviour observed in test and extends the application range. In addition, reduction factor for calculating the axial capacity of this form of CFST columns are proposed.