Five commonly used materials of construction:
Common types of cement: Portland cement, ordinary Portland Cement, Portland slag cement, pozzolana cement and Portland fly ash cement.
Cement grade: The cement grade indicates the compressive strength of hardened cement. Common cement codes are: 325, 425, 525, 625, etc.
Technical characteristics of common cement:
- Setting aging: The setting time of cement is divided into initial setting and final setting. Initial setting is the time when cement is mixed with water until the slurry begins to lose its plasticity. The final setting is the time from the beginning of mixing until the cement loses its plasticity completely and begins to produce strength.
- Volume stability: refers to the cement in the hardening process, the volume change is uniform nature. The uneven volume change of cement after hardening results in poor volume stability and can not be used.
- The hydration reaction of cement is exothermic. As the hydration process proceeds, the continuous release of heat is called hydrothermal. The quantity of heat released and the speed of heat release are mainly related to cement grade, mineral composition and fineness.
- Fineness: refers to the thickness of cement particles. The finer the particles, the higher the early strength. However, the finer the particles, the higher the production cost, and easy to be damp failure.
- Standard consistency water consumption: refers to the cement mortar to reach the standard consistency of water consumption. Standard consistency is to do the soundness of cement and setting time, the national standard of consistency.
Construction of the types of steel: steel is made of steel ingot through hot rolling, it is also called hot rolled steel bar, is the largest amount of construction projects in the varieties of steel.
- According to the shape can be divided into: light round bar, ribbed bar.
- According to steel can be divided into: carbon steel reinforcement and ordinary low alloy steel reinforcement.
- According to the intensity can be divided into: i, ii, iii, iv four levels. Grade I steel is low carbon steel, grade II, III and IV are low alloy steel.
Application of Steel Bars for Construction
- Grade I steel bar is hot rolled round steel bar with low strength and good plasticity and weldability. It is widely used in the common reinforced concrete structure with smaller stress.
- The strength, plasticity and welding properties of grade II and grade III deformed bars are good, and they are the most used steel bars in ordinary reinforced concrete structure. They can also be used as prestressing steel after cold drawing.
Wood species: divided into conifers and broadleaf trees. The conifer tree trunk is long and tall, the texture is straight, the material is soft, the processing is easy, is the main timber in the construction project. Broad-leaved tree material is harder, called hardwood, mainly used for decoration projects.
Properties and uses of building wood:
- Korean pine: soft material, texture straight, not easy to warp, cracking, resin, corrosion resistance, easy processing, mainly used for the production of doors and windows, roof frame, purlin, template and so on.
- Spruce: also known as white pine. Light material, straight texture, fine structure, easy drying, processing, mainly used for making doors and windows, template, floor, etc.
- Masson pine: hard material, texture straight oblique uneven, structure to coarse, not resistant to decay, resin odor is strong, very durable in the water, mainly used for the production of templates, doors and windows, citron, wooden pillars, etc.
- Larch: hard and brittle material, resin, strong corrosion resistance, dry slow, dry easy to crack. Mainly used for purlin, floor, wooden pile and so on.
- Chinese fir: texture straight and uniform, medium or coarse structure, easy to dry, strong durability. Mainly used for the production of roof trusses, purlins, doors and windows, and so on.
- Cypress: dense material, texture straight or oblique, fine structure, dry easy to crack, tough and durable. Mainly used in the production of templates and fine wood decoration.
- Pinus ponderosa: fine skin and thick skin two. Fine skin structure, not easy deformation, easy processing, suitable for higher requirements of decoration; The structure of thick leather is looser, but the material is strong, deformation and shrinkage is small, suitable for the decoration of low requirements.
Classification of timber:
- In order to use timber reasonably, the timber is divided into log, fir original strip, board square, etc.
- Log refers to felled after pruning, and cut into a certain length of wood. Direct use of logs and processing logs.
- The original Chinese fir (Cunninghamia lanceolata) is only pruned and peeled, not processed into wood. The length is more than 5M and the diameter of the tip is over 60mm.
- Plate and square refers to the sheet and square processed by a certain size. Plate refers to the section width of three times thick and more than three times; Square timber means the section width is less than three times the thickness.
Ordinary concrete concept:
It is mainly composed of cement, ordinary gravel, sand and water configuration of concrete. Stone and sand from the skeleton role, called aggregate. Gravel for coarse aggregate, sand for fine aggregate. Cement with water forms a slurry that wraps around the aggregate surface and fills the spaces between the aggregates, As the lubrication material between aggregates, the concrete mixture has the workability suitable for construction, cement hydration and hardening will cement aggregate together to form a solid whole.
Performance of concrete:
- The workability of concrete: refers to whether the concrete is suitable for operation in the construction, whether it has the ability to make the quality of the cast components uniform, forming dense performance.
- Concrete strength: compressive strength is the main strength of concrete index, it is much higher than other concrete strength, engineering is mainly to use its compressive strength, but also the main basis for structural design.
- The durability of concrete: concrete can resist a variety of natural environment erosion and not be damaged ability called durability. In addition to the requirements of concrete with a certain strength to withstand loads, it should also have durability, such as impermeability, frost resistance, wear resistance, weathering resistance.
Clay brick is to clay as the main raw material, after mixing into plasticity, with mechanical extrusion molding. Extruded earth called brick, after air-dried into the kiln, in the high temperature of 900-1000 °C calcined brick.
- Types of clay brick:
Standard brick: standard brick is the most commonly used brick in construction, it is widely used in brick-bearing walls, but also for non-load-bearing infill walls. The size of clay brick is 240mm × 115mm × 53mm. Each brick weighs about 2.5kg when dried and about 3kg after absorbing water.
Hollow brick and porous brick: the specification of hollow brick is 190mm × 190 mm × 90 mm, weight 1100Kg per cubic meter. The size of the porous brick is 240 mm × 115 mm × 90 mm, weighing about 1400 kg per cubic meter.
- The strength of clay brick:
Clay brick is characterized by high compressive strength, can withstand greater external force. The ability to reflect the bearing force of the brick is called strength; And reflect the strength of the magnitude called the strength level. A building choose which strength grade brick, should be determined by the design unit through calculation.
- Clay brick water absorption:
Clay brick has certain water absorption, can absorb a certain amount of water, water absorption can be used to say. Water absorption is generally allowed in the range of 8% -10%.
- Frost resistance of clay brick:
It refers to the ability of brick to resist frost damage. Frost resistance was determined by experiment.
- Appearance quality of clay brick:
The appearance of ordinary clay brick should be flat and square. Appearance without obvious bending, lack of Leng, Angle, cracks and other defects, percussion issued a crisp metal sound, uniform color.