At present, China’s building construction materials in the continuous improvement and innovation, in the process of the development of the construction industry has also appeared many new building materials, in many new building materials, ceramic concrete is a very important one, its cast-in-place structure in high-rise buildings has been more widely used, in the use of this building material, must pay attention to the control of the construction process, only then In the use of this building material, we must pay attention to the control of the construction process, only then can we better ensure the effect of construction.
1 Project overview
A high-rise building with a total height of 282m is a double-tower gateway building, which will be a multi-functional building integrating senior shopping mall, office building, star hotel, supermarket and entertainment club, and is a landmark building in Suzhou. The project has 2 zones in the north and south, the podium has 8 floors and is about 60m high, the roof is steel structure, 120mm thick vitrified concrete is poured on the steel roof, about 5400m2. according to the design requirements, the strength grade is LC25, the dry density is not more than 1700kg/m3, it is structural concrete.
2 Concrete raw materials
The vitrified concrete used in the construction of the project is a load-bearing concrete with a relatively high design strength grade and a relatively small dry density, in which case it will be able to meet the specific requirements of the project construction. The vertical pumping height of concrete is 60m, and the horizontal pumping distance is 150m. The concrete mix must have very good pumpability and water retention.
At present, the more common varieties of ceramic granules on the market is usually clay ceramic granules and shale ceramic granules, clay ceramic granules own density is not very large, in the concrete mix is easy to appear floating phenomenon, so in the pumpability is not very good, at the same time in its own cylinder pressure strength in 2MPa up and down, so in the process of construction can only use the strength level of 15MPa or less concrete. Shale ceramic granule concrete wood mishap is greater than the density of clay ceramic granule, in the concrete mix, the possibility of its uplift is not very large, in the design of a reasonable ratio can be a good guarantee of its pumping performance. In addition, the compressive strength of shale granule cylinder is higher than that of clay granule, which can reach about 5MPa, so we can configure the concrete with strength level above 20MPa in the process of construction, so we use shale granule in raw materials.
And after a brief analysis of the raw materials in the region, the choice of natural sand in the fine aggregate, in addition to adding the right amount of mineral powder and fly ash, so that it can be very effective to improve and perfect the performance of the concrete itself, but also significantly reduce the strength of the concrete itself, in addition to adding the right amount of water-reducing agent, which has a very positive effect on the control of the water consumption of a single concrete. This has a very positive effect on the water consumption control of concrete, and can significantly reduce the water-cement ratio.
3 Project application
3.1 Production control measures
First of all, when the ceramic pellets come in, the quality of ceramic pellets must be strictly checked, the main items checked are bulk density, water absorption rate and particle gradation, etc. The ceramic pellets that do not meet the construction requirements cannot be applied in the construction. Ceramic pellets transportation and stacking time, must ensure that the particles are evenly mixed, take effective measures to control the problem of segregation, but also to prevent debris mixed into the ceramic pellets.
Secondly, after the ceramic pellets into the field, it must be drenched and soaked in the way of pre-wet treatment, usually we have to be three days before the construction of the goods, after the goods should be placed in the designated location stacked, the pile around the set up a spray tap, the spacing should be controlled in 1m up and down, the spraying time must be maintained in more than 1 day, so you can also better ensure that the ceramic pellets can reach a water absorption Saturated state, in the temperature of less than 5 ℃, it can not be pre-wet treatment, but also can not carry out pumping construction.
Again, in the process of ceramic concrete production, concrete mixes and different constituent materials should be measured in accordance with the quality of the way it is produced, in the process of production, must stop sprinkling treatment 4 hours in advance to completely drain the water on the surface of the ceramic pellets. Before the production of materials, must be accurate determination of the wet stack density on the ceramic pellets, ceramic concrete using a forced mixer to complete the mixing work, mixing time should be done according to the specific circumstances of the project to extend the processing, the mixing time must be more than 45s.
Finally, during the production, the material slump must be strictly controlled, because the loss of slump is more obvious due to the water absorption of pottery pellets, the time of transportation and the time of unloading, in the process of construction and building, we should set the factory slump between 190-200mm, and the slump before pumping and unloading should be controlled between 160mm-180mm.
3.2 Construction situation
3.2.1 Pump pipe arrangement
According to the arrangement of the construction site, only fixed pump connected to the pump pipe could be used for construction, and 1 pump was used for each pour. The fixed pump was arranged above the top slab of the subway in the middle of the south and north podiums. The pump pipe can be connected from the reserved hole of the floor to the floor to be poured, and the path of taking over the pipe will be laid according to the “backward” method during the pouring. When laying the horizontal pump pipe on the ground floor, a concrete pier will be set every 3m or so for fixing. In the whole construction, the horizontal pumping pipe is about 150m and the vertical pumping pipe is about 60m. The construction is carried out by Zoomlion ZLJ5121THB truck-mounted pump, which has a maximum theoretical pumping outlet pressure of 22MPa and can meet the construction requirements of 200m pumping ordinary concrete. In the pumping process of this project, the outlet pumping pressure of vitrified concrete is generally 15~17MPa, which is 30%~40% larger than the pumping pressure of ordinary concrete.
3.2.2 Pouring process
In this concrete pouring, the south skirt roof was completed from south to north in one time, and the north skirt roof was completed from north to south in one time. In order to ensure the stability of the structure, the north-south pump pipe was set at the highest point of the roof of the podium, and the pouring order was 2m on the left, 2m on the right, 4m on the left, 4m on the right, and so on, with the north-south pump pipe as the center.
3.2.3 Levelness control of sloping roof
After installing the beam reinforcement of the slope roof as required, set the steel guide on the plate reinforcement, the guide adopts Φ10mm secondary steel, the upper surface of the guide reinforcement is the concrete surface, the guide is welded firmly with the plate reinforcement, the steel head shall not be higher than the guide surface, the support spacing is 500~800mm and each guide shall not be less than 3 support points. In the process of concrete pouring on the roof, 2m scrapers are used on the rails to level the concrete poured on the slab surface and control the elevation of the concrete surface.
3.2.4 Pouring and forming
The free height of pottery concrete mix pouring dumping should not exceed 1.5m. When the dumping height is greater than 1.5m, auxiliary tools such as string barrel, inclined chute or chute should be added.
The thickness of this project is 120mm, and the concrete is pounded with a flat vibrator. Vibrating time is determined according to the actual mix consistency and vibrating parts, controlled at 10-30s, and the specific continuation time is based on the principle of mix vibration and avoiding the floating of pottery particles. After pouring and forming, use tools such as clapper, scraper, roller or vibrating trowel to press the ceramic particles floating in the surface layer into the concrete in time. For the place where the ceramic particles float larger area, use the surface vibrator to re-vibrate, make the mortar back on, and then do the plastering.
3.2.5 Concrete maintenance
Pottery granule concrete should be covered or sprayed with water in time after casting and forming maintenance. When using natural maintenance, wet maintenance time should not be less than 7d. When using plastic film to cover maintenance, all surfaces must be covered tightly to keep the film inside the condensation water.
In the high-rise building construction and construction, we in the choice of ceramic concrete among the ceramic particles, can choose shale ceramic particles, in its reasonable configuration, scientific choice of production process, on the one hand, it can reflect the very good pumpability, on the other hand, can also reflect the very good strength and density. Escape from the concrete density is relatively light, it can very effectively control the weight of the structure, but also has very good heat insulation, sound insulation and fireproof performance, so in the future of building construction has a good prospect for development.