According to the density of the material, it can be calculated that the total volume of slurry is 35.97L, so the volume ratio of slurry added is 35.97/500 × 100%=7%, that is, when the volume ratio of added grout and compacted roller compacted concrete is 7%, the deformed concrete produced meets the technical requirements.
As the abnormal concrete is vibrated with a vibrating rod during construction, the slump of the abnormal concrete during grouting must meet the requirements of vibration.
02 Relevant requirements for deformed concrete Rolling layer thickness of roller compacted concrete is generally 30cm.
The theoretical mix of G3C2090W8 roller compacted concrete is shown in Table 3.1.1.
(2) Raw materials.
(1) In the construction of the project, two methods have been designed to carry out tests: ① surface mortar spreading method; ② Ditch secondary grouting method.
As the test is carried out indoors, 0.5m3 roller compacted concrete can be mixed.
The construction method of trench grouting: the layered paving thickness of roller compacted concrete is generally 30cm; Dig a groove about 25cm deep and 30cm wide on the paved RCC surface; Evenly spread the prepared mortar into the trench in a certain amount, and then backfill 15 cm thick roller compacted concrete; Then evenly spread mortar according to a certain amount; After the grout is soaked, start to vibrate the concrete until it is dense.
According to the mix proportion calculation, the mass of grout in concrete is 0.5 × (80+110+81)=135.5kg。 When the amount of grout added is 61kg, the slump of the deformed concrete is 3cm, and the vibration construction can be carried out.
(2) The volume method is used to control the amount of slurry added in this project.
03 Mix proportion and construction technology of abnormal concrete The RCC dam of the lower reservoir of a power station (hereinafter referred to as a power station) is taken as an example to analyze the case of the amount of grout and the grouting technology of abnormal concrete.
At this time, the mass ratio of the grout added (the ratio of the mass of the grout added to the mass of the slurry in the roller compacted concrete) is 45%.
The so-called “abnormal” refers to the construction method of making the dry and hard roller compacted concrete into the extremely low flow abnormal concrete that can be vibrated through the technological measures of adding grout.
According to different construction processes, the working width of deformed concrete is generally 0.3m-0.5m: the width is too small to ensure the construction quality of grouting and vibration; Excessive width increases the construction amount of abnormal concrete, affects the construction speed of roller compacted concrete, thus increasing the amount of cementitious materials, and is not conducive to dam temperature control.
In the laboratory, G3C2090W8 roller compacted concrete shall be mixed according to the mix proportion, and cement fly ash paste shall be prepared according to the same water binder ratio, but air entraining agent shall not be added.
The amount of grout added to the deformed concrete shall be determined through tests.
The amount of grout is determined through indoor simulation of on-site construction conditions.
3.1.2 Determine the amount of grout.
Table 3.1.1 Theoretical mix ratio of roller compacted concrete kg/m3 Note: the dosage of water reducing agent is 0.5%, and the dosage of air entraining agent is 0.02%.
It can be calculated that 40% is added to 0.5m3 RCC × 45%=18kg cement, 55 × 45%=24.75kg fly ash, 40.5 × 45%=18.22kg slurry made of water and additives, and meet the technical requirements.
As an important part of dam concrete, abnormal concrete must meet the technical requirements of the dam for concrete.
In the construction of roller compacted concrete dam, abnormal concrete is widely used in the joints between bedrock surface and roller compacted concrete that cannot be directly rolled by vibrating roller, the edge of formwork, around the gallery, reinforcement in the dam and other parts.
First spread a certain amount of grout, then spread a certain amount of RCC mixture, and test the impact of vibration time and different grout dosage on concrete slump.
The cement is P.O42.5 cement, and the fly ash is Grade I high-quality fly ash.
By comparison, the latter is even, fast, simple and easy to construct.
After the construction is completed, the formwork shall be removed for visual inspection, and the inspection results shall be recorded: the concrete facade shall be flat without pitted surface, cracks and other defects..
3.1.3 The selection of different grouting construction processes will have a greater impact on the construction speed and quality of abnormal concrete, so the selection of economic and rapid construction processes is the key to the construction of abnormal concrete.
The roller compacted concrete G3C2090W8 (three graded concrete grade: C20, design age: 90 days, impermeability requirement: W8) is used below the dead water level on the upstream upstream of a power station, so the performance of deformed concrete should also be G3C2090W8.
The specific method is: measure the volume V of a barrel of slurry and the sectional area A of the groove, and then calculate the slurry adding distance L=V/(A) according to the volume ratio (7%) of the slurry amount × 7%), since the slurry is added twice, the depth of the groove shall be paid attention to when calculating the sectional area A of the groove.
According to the field practice, the vibration time after adding grout shall be controlled at 3min/m.
01 The basic concept of abnormal concrete is often heard in hydraulic engineering projects, so what is “abnormal concrete”? Abnormal concrete refers to the concrete that has been mixed with a certain proportion of mortar in the paved RCC mixture and then vibrated and compacted.
The glue used for grout shall be the same as that used for dam concrete, and all raw materials shall pass the inspection.
3.1 Grout dosage 3.1.1 Grout preparation (1) Design index.
It is stipulated in the Specification for Construction of Hydraulic Roller Compacted Concrete (DL/T5112-2021) that “the mortar used for distorted concrete is made of cement, fly ash and admixtures, and its water binder ratio should not be greater than that of the same type of roller compacted concrete”.
