Experimental scheme of roller compacted concrete modified by fiber rubber powder

　　1. fiber rubber powder modified roller compacted concrete mix ratio

Aggregate: crushed stone: sand = 67%:33% (mass ratio).

Dosage of other materials: 42.5# cement 260kg/m3; Fly ash: 60kg/m3; Domestic modified rubber powder 3.5kg/m3; Modified polypropylene fiber 0.9kg/m3; The water consumption is the water content suitable for roller compacted concrete (refer to 120kg/m3).

Aggregate gradation is shown in the table below:

Mesh size (mm)	19.0	9.5	4.75	2.36	1.18	0.6	0.3	0.15
Pass percentage rate (%)	90~100	50~70	35~47	25~38	18~30	10~23	5~15	3~10

Three groups of 100mm × 100mm × 400mm and 150mm × 150mm × 150mm specimens are formed respectively. The specific dosage of each material is shown in the table below:

Material Type	Cement	fly ash	Gravel	Sand	Rubber powder	fiber	Water
Dosage (kg)	10.62	2.655	57.525	33.1875	0.154875	0.039825	5.31

The amount of gravel with different particle size is as follows:

Particle size (mm)	19.0	9.5	4.75	2.36	1.18	0.6	0.3	0.15	0.075
Mass (kg)	2.9	20	11	5.5	4.3	4.3	3.7	2	3.7

　　Experimental study on flexural strength of roller compacted concrete modified by 2. fiber rubber powder

1. Test purpose:

Determination of fiber powder modified roller compacted concrete flexural (I. e. bending tensile) strength.

2. Test basis:

GBJ81-85 Test Methods for Mechanical Properties of Ordinary Concrete.

3.150mm × 150mm × 600mm (or 550mm) trabecula shall be used as the standard specimen for concrete flexural strength test. The maximum size of aggregate in the concrete used to make the standard test piece shall not be greater than 40mm. If necessary, 100mm × 100mm × 400mm specimen can be used. At this time, the maximum particle size of aggregate in concrete shall not be greater than 30mm.

4. Instruments and equipment: the testing machine used in the flexural test can be a flexural testing machine, a universal testing machine or a pressure testing machine with a flexural test frame. All these machines shall be equipped with means for simultaneously acting two equal loads on the third trimesters of the trabecular span. The accuracy of the testing machine (relative error of the indication) shall be at least ± 2%. The range shall be such that the expected failure load value of the specimen is not less than 20% of the full range and not more than 80% of the full range.

The two supports and two pressure heads of the testing machine in contact with the test piece shall have an arc-shaped top surface with a diameter of about 20-40mm, and shall be at least 10mm longer than the width of the test piece. Three of them (one bearing and two pressure heads) should roll and tilt back and forth as much as possible.

5. The test piece shall be tested in time after it is taken out from the curing site. Before the test, the sample shall be kept in a dry and wet state similar to the original curing site.

6. Concrete flexural strength test shall be carried out according to the following steps:

6.1 Wipe the sample clean, measure the size and check its appearance. The size of the specimen is measured to the nearest 1mm, and the strength is calculated accordingly. The specimen shall not have obvious defects. In the tensile zone of the mid-span 1/3 beam, there shall be no holes with a surface diameter of more than 7mm and a depth of more than 2mm. The flatness of the contact line of the bearing area and bearing area of the specimen shall not exceed 0.05mm per 100mm.

6.2 adjust the position of the support frame and indenter as required, and the dimensional deviation of all the spacing shall not be greater than ± 1mm.

6.3 Place the test piece on the bearing of the testing machine and center it stably. The bearing surface shall be the side of the test piece when it is formed. To start the testing machine, when the pressure head is close to the specimen, adjust the pressure head and the support to make the contact balance. If the pressure head and the support cannot be tilted back and forth, the poor contact points shall be leveled.

The test of 6.4 specimens shall be continuously and evenly loaded, and the loading speed shall be: 0.02-0.05Mpa(0.2-0.5kg/cm2) per second when the concrete strength grade is lower than C30 (equivalent to the original No. 300); When the strength grade is higher than or equal to C30 (equivalent to the original No. 300), 0.05-0.08Mpa(0.5-0.8kg/cm2) per second is taken. When the test piece is close to failure, stop adjusting the throttle until the test piece fails, and record the failure load and failure position.

7. Calculation of test results:

When the 7.1 specimen is destroyed, if the fracture surface is between two concentrated loads, the flexural strength shall be calculated according to the following formula:

where: ff-flexural strength of concrete, Mpa;

P-failure load, N;

l -- distance between supports, I .e. span, mm;

B -- Section width of sample, mm;

H-section height of test piece, mm.

The arithmetic mean of the measured values of the three specimens is used as the flexural strength value of the group of specimens. If the difference between the maximum or minimum value of the three measured values and the intermediate value exceeds 15% of the intermediate value, the maximum and minimum values shall be cut off together, and the intermediate value shall be taken as the flexural strength value of the group of specimens. If the difference between the two measured values and the median value exceeds 15% of the median value, the test results of this group of specimens are invalid.

If one of the three 7.2 specimens has its fracture surface outside the two concentrated loads (subject to the tensile area), the test results of the specimen shall be discarded, and the flexural strength of concrete shall be calculated according to the test results of the other two specimens. If the fracture surfaces of two specimens are beyond the two concentrated loads, this group of tests is invalid.

When the 7.3 adopts 100mm × 100mm × 400mm non-standard specimen, the flexural strength value obtained shall be multiplied by the size conversion factor for 0.85.

8. Make test records in time according to the measured data.

Table 1 Results of flexural strength test

Age	3d	7d	28d
Bend strength (Mpa)

　　Compression test of roller compacted concrete modified by 3. fiber powder

1. Test purpose:

The compressive strength of RCC modified by fiber rubber powder was determined.

2. Test basis:

GBJ81-85 Test Methods for Mechanical Properties of Ordinary Concrete.

3.150mm × 150mm × 150mm standard specimen shall be used for concrete compressive strength test. The maximum size of aggregate in the concrete used to make the standard test piece shall not be greater than 40mm. If necessary, 100mm × 100mm × 100mm specimen can be used. At this time, the maximum particle size of aggregate in concrete shall not be greater than 30mm.

4. Instruments and equipment: the testing machine used for compression test can be pressure testing machine and universal testing machine. The accuracy of the testing machine (relative error of the indication) shall be at least ± 1%. The range shall be such that the expected failure load value of the specimen is not less than 20% of the full range and not more than 80% of the full range. The upper and lower pressure plates of the testing machine and the test pieces can be padded with steel backing plates. The size of the backing plates shall be larger than the bearing surface of the test pieces, and their flatness shall not exceed 0.02mm per 100mm;

5. The test piece shall be tested in time after it is taken out from the curing site. Before the test, the sample shall be kept in a dry and wet state similar to the original curing site.

6. Concrete compressive strength test should be carried out according to the following steps:

The 6.1 specimen shall be tested in time after being taken out from the curing site. Before the test, the surface of the sample shall be wiped clean, the size shall be measured, and its appearance shall be checked, and the bearing area of the sample shall be calculated. When the difference between the measured size and the nominal size does not exceed lmm, the calculation can be based on the nominal size;

6.2 Place the test piece on the lower pressing plate or the lower backing plate of the testing machine, the bearing surface of the test piece shall be perpendicular to the top surface during molding, and the center of the test piece shall be aligned with the center of the lower pressing plate or the lower backing plate of the testing machine. Start the testing machine, and when the upper pressing plate is close to the test piece or the upper backing plate, adjust the ball seat to make the contact surface evenly compressed. At 0.3-0.5MPa (the concrete strength loading speed specified in GB/T50081 is: 0.5-0.8MPa when ≥ C30;