What precautions are needed for plastic rockery?
Nowadays, rock-filled rockery is needed in many places. As a new type of rockery-landscape, it can better create the environment and atmosphere, make up for the shortcomings of traditional rockery, and meet the urgent needs of modern garden landscape development. Do you understand the production needs? Let's introduce it to everyone.
I. Temperature control and shrinkage of concrete
In order to suppress and control the occurrence of harmful cracks, it is necessary to comprehensively consider the aspects of controlling the hydration temperature rise of the concrete, delaying the temperature decrease rate, reducing the concrete shrinkage, increasing the ultimate tensile strength of the concrete, improving the constraint conditions and design structure, etc. .
Second, reduce the heat and deformation of cement hydration
1. Concrete with low or medium hydration heat is used to prepare concrete, such as slag portland cement, pozzolanic portland cement, fly ash cement, composite cement, etc.
2. Make full use of the late strength of concrete to reduce the amount of cement in each cubic meter of concrete. According to the test, for every 10 kg of cement, the hydration heat will increase the temperature of the concrete by 1 degree Celsius.
3． Use coarse aggregate, try to choose coarse and fine aggregate with large particle size and good gradation; control the sand and mud content; add the fly ash and other admixtures or the corresponding water reducing agent and retarder to improve Workability, reduce water-cement ratio, in order to achieve the purpose of reducing the amount of cement and reducing the heat of hydration.
4． The cooling water pipe is embedded in the foundation, and circulating cooling water is introduced to reduce the hydration heat temperature of the concrete.
5. In thick and thick concrete with little or no reinforcement, adding large stones with a total amount not exceeding 20% to reduce the amount of concrete to achieve the purpose of saving cement and reducing hydration heat.
6. When mixing concrete, an appropriate amount of micro-expansion agent or expansion cement can also be added to make the concrete compensate for shrinkage and reduce the temperature stress of the concrete.
7. Improve reinforcement. In order to ensure that there are temperature ribs above and below each pouring layer, the designer can suggest that the distribution ribs be adjusted appropriately. The temperature bars should be finely distributed. Generally, φ8 steel bars are used, and the two-way reinforcement is used, and the spacing is 15 cm. This can enhance the ability to resist temperature stress. The binding of the upper layer of steel bars should be carried out after the lower layer of concrete has been poured.
8. Set the post-seam. When the plane size of the large-volume concrete is too large, a post-cast joint can be appropriately set to reduce external stress and temperature stress; at the same time, it is also beneficial to heat dissipation and lower the internal temperature of the concrete.
Third, reduce the concrete temperature difference
1. Choose a more suitable temperature for pouring large volume concrete, and try to avoid pouring the concrete in hot weather. In summer, low temperature or ice water can be used to stir the concrete. The aggregate can be sprayed with cold water mist or air pre-cooling, or the aggregate can be covered or a shading device can be installed to avoid direct sunlight. If the transportation facilities have the conditions, they should also be equipped with sun protection facilities. In order to reduce the mold temperature of the concrete mixture.
2. Add the corresponding retarder type water reducing agent, such as calcium lignosulfonate.
3． When concrete is put into the mold, measures are taken to improve and strengthen the ventilation in the mold to accelerate the heat dissipation in the mold.
Fourth, strengthen the temperature control during construction
1. After the concrete is poured, do a good job of thermal insulation and moisture conservation of the concrete, slowly reduce the temperature, give full play to the creep characteristics, reduce the temperature stress, pay attention to avoid exposure in the summer, pay attention to moisture retention, and take measures to keep the temperature in the winter to avoid sharp temperature gradients. .
2. Take long-term curing, stipulate a reasonable mold removal time, delay the cooling time and speed, and give full play to the "stress relaxation effect" of concrete.
3． Strengthen temperature measurement and temperature monitoring and management, implement information-based control, and control temperature changes in concrete at any time. The internal and external temperature difference is controlled within 25 degrees Celsius, the base temperature difference and the base temperature difference are controlled within 20 degrees Celsius, and timely adjust insulation and conservation measures In order to prevent the temperature gradient and humidity of the concrete from being too large, the occurrence of harmful cracks can be effectively controlled.
4． Reasonably arrange the construction procedures, control the concrete to rise evenly during the pouring process, and avoid the excessive height difference of the concrete mixture. Backfill the soil in time after the structure is completed to avoid long-term exposure of the sides.
V. Improve constraints and reduce temperature stress
1. Adopt layered or block pouring of large volume concrete, reasonably set horizontal or vertical construction joints, or set post-construction pouring belts at appropriate locations to relax the restraint, reduce the heat storage length of each pouring length, and prevent the accumulation of hydration heat To reduce temperature stress.
2. A sliding layer is set between a large volume concrete foundation and a rock foundation, or between a foundation and a thick concrete cushion layer, such as using flat pouring asphalt rubber for paving sand, or brushing hot asphalt or coiled material. A buffer layer is provided on the vertical plane and the keyway, such as laying 30 to 50 mm thick asphalt wood wool board or polystyrene foam plastic to eliminate the embedding effect and release restraint stress.
Six, increase the ultimate tensile strength of concrete
1. Select a good graded coarse aggregate, strictly control its mud content, strengthen the vibration of the concrete, improve the compactness and tensile strength of the concrete, reduce the shrinkage deformation and ensure the construction quality.
2. Adopting the secondary feeding method and the secondary vibrating method, the surface water is removed in time after pouring, the early curing is strengthened, and the tensile strength and elastic modulus of the concrete at the early or corresponding age are improved.
3． The necessary temperature reinforcements are set in the large-volume concrete foundation. Increasing diagonal structural reinforcements are used to increase the concentration of stresses and prevent cracks at sudden changes in sections and corners, corners of bottoms, roofs and walls, corners of holes, and periphery.
The above is the contents of the precautions for the plastic rockery , which I hope to help you. If you want to know other aspects, you can come to consult us, we will have professionals to answer your questions.