Concrete
Concreteis a kind of composite material. It is compod of aggregates bonded together with some kind of bonding material. In general, cement is ud as the bonding material and sand & crushed stones are ud as the aggregates. They shall be prepared according to a certain proportion and mixed with water (additives and admixtures could be contained in the water) to produce cement concrete, also named as ordinary concrete. Concrete is widely ud for civil engineering works and in Chine, conc rete can also be pronounced as “Tong” for short. Ordinary concrete are primarily compod of water, cement, sand (fine aggregates) and crushed stones (coar aggregates). Water and cement together constitutes fluid cement paste to bond fine and coar aggregates together and fill in the gaps between the aggregates, so as to increa concrete density. Sand and crushed stones constitutes framework of concrete, in order to protect cement paste from drying and shrinking. Graded aggregates shall be placed in a proper way to have a formation as den as possible and to save cement paste as much as possible. Concrete are sorted into various types according to different sorting methods.
(1) Sorted by apparent density
nd的过去式1) Heavyweight concrete. It is usually compod of barites, iron ore and similar heavy material. Its apparent density is 2600kg/m3.
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2) Ordinary concrete. It is mixed with certain proportion of sand, crushed stones and cement. Its apparent density is between 1950 kg/m3 and 2500 kg/m3. Ordinary concrete is the most widely ud type in civil engineering works.
this is怎么读3) Lightweight concrete. This type of concrete includes lightweight aggregate concrete, porous concrete and big-hole concrete, with apparent density of 1950kg/m3.
grandparents(2) Sorted by different types of bonding material
Concrete can also be sorted by and named after different types of bonding material, such as cement concrete, plaster concrete, sodium silicate concrete, silicate concrete, asphalt concrete, polymer concrete, and so on. Besides, concrete can also be named after the added modified material, for example, cement concrete, if added with steel fiber, shall be called steel fiber reinforced concrete; while if added with large amount of fly ash, shall be called fly ash concrete.jaya
(3) Sorted by various functions and features
在线背单词Concrete can be sorted by various functions, features and placement locations, including structural concrete, road concrete, hydraulic concrete, heat-resistant concrete, acid resistant concrete, radiatio
n shielding concrete, shrinkage compensating concrete, water tight concrete, pumped concrete, lf-consolidating concrete, fiber reinforced concrete, polymer concrete, high-strength concrete, high-performance concrete and so on.
1.2 Workflow and Workmanship for Concrete Works
Workflow for concrete works is: concrete mixing, concrete transportation, concrete placing, vibratory compaction of placed concrete and concrete surface leveling, and concrete curing.
1.2.1 Concrete mixingsat考试培训>stainless steel
山东2014高考分数线Before concrete mixing, inner wall of concrete mixer shall be fully lubricated. Water cement ratio and slump shall be controlled through strict measurement. Crushed stones shall be loaded into the concrete mixer first, and then cement, sand and water will follow step by step.
1.2.2 Concrete transportation, pumping and spreading
Concrete cart, motor-driven dumping truck, and concrete mixing truck are mainly ud for
horizontal transportation of concrete. Headframe, concrete hoister and construction elevator are mai
nly ud for vertical transportation. Automobile pump (mobile pump), and fixed pump are ud to pump up concrete. In order to increa production efficiency, pipe of concrete pump shall be connected with concrete spreader (spreading boom), and concrete pump and concrete spreader will work together to place concrete as required.
1.2.3 Concrete placing, vibratory compaction of placed concrete and concrete surface leveling
1、普通混凝土
a. ordinary concrete
1) The height between bucket from where concrete starts to fall and the location which the concrete touch after falling shall be no more than 2 meters. If the height exceeds 2 meters, corresponding measures must be taken, such as tumbling barrel, chute or similar tools.
2）Concrete shall be placed layer by layer and ction by ction. Height of each layer shall be decided according to concrete supply capacity, quantity of concrete placed for each time, initial tting time, structural features, and gaps between adjacent steel bars. In general, the height shall be 1.25 times the length of the vibrator’s rod which can be put into the concrete.
中学英语作文
3）Inrt-type concrete vibrator shall be put into concrete fast and pulled out more slowly. The inrtion points shall be arranged in an even and orderly manner. Vibrating shall be carried out point by point. The distance between adjacent points shall be no more than 1.5 times of vibrating radius (Generally, the distance is between 30cm and 40cm). When vibration for the upper layer is carried out, the vibrating rod shall be inrted into the adjacent lower layer for 5-10 cm, in order to make the two adjacent layers fully mixed and bonded as one. During vibration, vibrating rod cannot touch any steel bar or formwork. Moving distance of surface vibrator (also known as plate vibrator) shall ensure that after moving, the plate shall cover the edge of just vibrated concrete.
4) Concrete placement shall be carried out continuously. In ca there is inevitably a stop, it shall be as short as possible. Before initial tting of the lower layer concrete is finished, placement of adjacent upper layer concrete shall be done. Maximum duration for such a stop shall be decided according to type of cement, temperature and conditions for concrete tting. If such a stop exceeds 2 hours, concrete placement of upper layer shall be carried out with reference to the method of treating construction joints. If duration for concrete tting is less than two hours, the duration needed for initial tting shall be adopted.
5）During concrete placement, formwork, steel bars, prerved holes, imbedded parts and dowel ba
rs shall be watched cloly and frequently to ensure there is no deformation, plugging or movement. If there is any defect, remedies shall be done before initial tting of concrete is finished.
