What does 4 0 concrete flexural test mean

1) Overview The flexural strength of cement concrete is an important parameter in the design of cement concrete pavement. In the construction of cement concrete pavement, in order to ensure the quality of construction, the flexural strength must also be determined according to the regulations.

The flexural strength of cement concrete is a beam-shaped specimen of 150mm l50mm 550mm, after reaching the specified age under standard curing conditions, under the action of a net span of 450mm and double fulcrum, and the strength value is obtained according to the specified calculation method.

2) Test apparatus.

1. Testing machine: 50 300KN bending testing machine or universal testing machine;

2. Flexural test device: that is, three points.

The flexural strength and flexural elastic modulus of double-point loading and three-point free-supporting concrete.

Test setup, as shown below.

3) Test methods.

1. Check the specimen before the test, if there is a honeycomb (greater than 7mm 2mm) in the middle of the specimen 1 3 length, the specimen should be invalid.

2. Measure the width and height of the specimen in the middle of the specimen to the nearest lmm.

3. Adjust the two movable bearings so that the distance between them and the center of the lower indenter of the testing machine is 225mm, and tighten the two bearings, and put the test piece properly on the bearing 7-movable bearing; 8-machine; 9-movable boat-shaped backing plate, the side of the specimen when forming is facing upward, after geometric centering, slowly add an initial load, about lkn, and then with the loading speed, uniformly and continuously load (use lower speed when low marking); When the specimen is close to failure and begins to deform rapidly, the throttle of the tester should be stopped and adjusted until the specimen is damaged, and the maximum load should be noted.

4 Calculation of test results.

1) When the cross-section occurs between two loading points, the flexural strength FCF (in MPA) is calculated according to Eq. (3-2): where: F—ultimate load (N);

l—distance between supports, l 450mm; b—specimen width (mm); h—height of the specimen (mm).

2) The arithmetic mean of the measured values of the 3 specimens.

as the flexural strength value of the specimens in this group. If the difference between one of the maximum or minimum values and the intermediate value of the three measured values exceeds 15 of the intermediate value, the maximum or minimum value is rounded together, and the intermediate value is taken as the flexural strength of the group of specimens. If the difference between the two measured values and the median value is more than 15 of the median value, the test results of the group of specimens are invalid.

3) If the section is located outside the loading point, the result of the specimen is invalid; If the results of two specimens are invalid, the results of the group will be invalid.

4) When the l00mm l00mm 400mm non-standard specimen is used, the test method of loading at the third point is the same as before, but the obtained flexural strength value should be multiplied by the size conversion factor.

Generally, it refers to the technical index requirements of road concrete, that is, the batch of concrete is made according to the specification of the bending test block (150 * 150 * 550), and then after 28 days of standard curing, a value obtained by using the standard method pressure test is the bending strength, bending strength, and concrete strength grade of the batch of concrete can not be lower than C30.

It should be C40 concrete, the flexural test is only one of the indicators to detect the quality of concrete, is to use the concrete collected on site to make a test block of the specified size, after reaching the standard curing period, with a special pressure equipment to do the destructive test (before doing must have written materials of concrete mixture).

Flexural strength is the tensile bending strength of concrete.

The flexural strength test uses 150mm, 150mm 600mm (or 550mm) trabecular as standard specimens.

Due to the direct influence of the repeated action of vehicle load and environmental factors (such as temperature and humidity), cement concrete pavement requires high flexural strength, durability, wear resistance and slip resistance to concrete slab. Among them, flexural strength is an important control index of concrete pavement, and whether its size meets the design requirements will directly affect the overall quality and service life of the pavement.

Meeting these requirements depends largely on the quality of the raw materials, the composition of the mixture, and the construction control on site. Therefore, in the engineering concrete road requirements, analyze the factors that affect its strength, so as to select qualified materials, scientific design, reasonable construction, to meet the requirements of the indicators of cement concrete pavement.

The failure of cement will directly affect the strength of concrete and the properties of its mixture. This mainly depends on the technical properties of the cement itself, such as calcification rate, shrinkage cracking, abrasion performance, etc., therefore, the cement for pavement requires high flexural strength, shrinkage, wear resistance, good durability and low elastic modulus and other technical properties.

"GB T 50081-2002 Standard for Test Methods for Mechanical Properties of Ordinary Concrete" stipulates:

150 150 600 mm (or 550) prism tryout, or 100 100 400 mm

150*150*550 (or 600) mold trial, if necessary, 100*100*400 (or 515) can be used

Flexural strength specimens shall comply with the following requirements:

1. The prismatic specimen with a side length of 1500mm*150mm*600mm (or 550mm) is a standard specimen;

2. The prismatic specimen with a variable length of 100mm*100mm*400mm is a non-standard specimen size tolerance.

1. The flatness tolerance of the bearing surface of the specimen shall not exceed the side length);

2. The angle of the adjacent surface of the specimen should be 90 degrees, and its tolerance should not exceed the degree.

3. The tolerance of the length, diameter and height of each side of the specimen shall not exceed 1mm

The general site of the trial mold 150 * 150 or 100 * 100 concrete test mold is not less than 9 groups, the same conditions, 600 degrees of days, standard maintenance needs at least 6 groups, there are three groups of spare, if there is impermeable concrete requirements at least 6 groups. There are at least 6 groups of mortar mold testing, which are also used for the same conditions and the standard cultivation of repentant ants.

Concrete mold trial according to different physical property requirements, with different specifications and size requirements most commonly used is concrete cube compressive strength test mold, this mold test to length, width and height = 150 150 150 (mm) as the standard, if the coarse aggregate particle size in the concrete is less than, can also use the length and width height = 100 100 100 (mm) of the mold test. The above 3 specimens are 1 group.

In order to measure the axial compressive strength of the concrete prism, the length, width and height = 150 150 300 (mm) can be used. Take 3 specimens as 1 group.

In order to determine the splitting tensile strength of concrete, to compare the tensile properties of concrete, when the maximum particle size of coarse aggregate is not greater than 40mm, the standard mold test of 150 150 150 (mm) can be adopted, when the maximum particle size of coarse aggregate is not greater than 20mm, the test mold of length, width and height = 100 100 100 (mm) can be adopted. Take 3 specimens as 1 group.

Standard bending size of cement: 40mmx40mmx160mm; Standard bending sizes for concrete: 150 mm x 150 mm x 600 mm or 150 mm x 150 mm x 550 mm.

The selection of cement varieties and labels should generally use cement with high strength, small shrinkage, good wear resistance and durability. The choice of variety and marking must be based on the grade of the road, the construction worker's rollover, the paving time, the method and the economy. In general, for overweight and heavy-duty traffic, it is recommended that the cement label is not lower than the number, and the others are not lower than the number.

Effect of raw material quality on flexural strength of cement concrete pavement: The quality of cement will directly affect the strength of concrete and the properties of its mixture. This mainly depends on the technical properties of the cement itself, such as calcification rate, shrinkage cracking, wear resistance, etc.

Therefore, cement for pavement requires high flexural strength, good shrinkage, good wear resistance, good durability, and low elastic mold pre-talk. The influence of cement dosage on concrete strength is too small, and it is difficult to meet the requirements of concrete strength, durability and wear resistance; If the dosage is too large, it can meet the strength requirements, but the hydration in the concrete disturbs the residual heat and shrinkage is large, and it is easy to crack due to shrinkage. Therefore, the amount of cement should meet the minimum cement consumption requirements, but the maximum amount of cement should also be controlled.

Cement flexural standard size: 40mmx40mmx160mm; Concrete flexural standard size: 150mmx150mmx600mm or 150mmx150mmx550mm.

Selection of cement varieties and labels. Generally, cement with high strength, small dry shrinkage, good wear resistance and durability should be used. The selection of its varieties and labels must be selected according to factors such as highway grade, construction period, paving time, method and economy.

It is usually recommended that the cement marking: extra-heavy, heavy traffic is not less than others.

Effect of raw material quality on flexural strength of cement concrete pavement:

1.The failure of cement will directly affect the strength of concrete and the properties of its mixture. This mainly depends on the technical properties of the cement itself, such as calcification rate, shrinkage cracking, abrasion performance, etc., therefore, the cement for pavement requires high flexural strength, shrinkage, wear resistance, good durability and low elastic modulus and other technical properties.

2.Effect of cement dosage on concrete strength. The dosage is too small to meet the requirements of concrete strength, durability and wear resistance; If the dosage is too large, although it can meet the strength requirements, the hydration heat in the concrete is large, and the shrinkage is also large, and it is easy to crack due to shrinkage.

Therefore, the amount of cement should meet the minimum cement consumption requirements, but the maximum cement consumption should also be controlled.

Kiss! Hello, happy to answer your <>

What are the standard test specifications of the bending resistance of concrete as follows: Concrete bending test mold size technical parameters: size size:

150*150*550mm size: 150*150*600mm ordinary concrete, generally refers to cement as the main cementitious material, water, sand, stone, if necessary, mixed with chemical admixtures and mineral admixtures, according to the appropriate proportion, after uniform stirring, dense molding and curing hardening of artificial stone. Concrete is mainly divided into two phases and states:

The plastic state before setting and hardening, i.e. fresh concrete or concrete mixture; The hard state after hardening, that is, hardening into concrete or concrete. The concrete strength grade is divided by the standard value of the compressive strength of the imaginary cube, and the current strength grade of ordinary concrete in China is divided into 14 grades: C7.

Wheelna, C20, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75 and C80 hope mine can help you <>

Do you have any other questions?