2. Procurement requirements: acceptance criteria and quality assurance requirements.
1, basic information: material name, specification, model, quantity and unit price.
2. Procurement requirements: origin, brand, quality, technical standards and inspection methods.
3. Transaction-related: delivery mode, acceptance mode, packaging standard, transportation mode and delivery date; Settlement related:
Provide qualified documents and materials; Market reputation and reasonable price; Provide qualified materials; The supply progress is stable.
The material clerk checks whether the name, specification, model and quantity of the material are consistent with the feeding list. For cement, steel bars and other substances, material certificates should be provided at the same time.
1, check whether the stow-wood in the yard is firm before unloading, and unload the goods in layers.
2. Cement shall be covered with tarpaulin to prevent rain and moisture;
3, bulk materials should be as close as possible to the material point;
Do a good job in field research and planning. Site natural conditions, design requirements and construction scheme, construction mode and material supply mode, site water and electricity supply conditions, transportation conditions, local material resources, material and schedule relationship, temporary facilities construction and machinery use.
1, establish and improve the on-site material management responsibility system, divide the area, and take responsibility. Regularly inspect and evaluate the contract area and scope of relevant personnel.
2. Grasp the construction production progress, do a good job in material balance, provide material information in time, correctly organize materials to enter the site, and ensure the construction production demand.
3. Carry out acceptance, distribution and return of materials, establish and improve original records and various ledgers, and conduct inventory and accounting every month.
4, the quota acquisition system, understand the team materials, strengthen inspection, regular assessment, and strive to reduce consumption.
1, take stock and adjust the material plan.
2. Organize the demolition of temporary facilities, consider reuse and avoid secondary treatment.
Quantity acceptance: counting, weighing, measuring ruler, measuring method, etc.
Question:
1, the materials on the site are piled up in disorder, and the management is lax, so it is not expected to be fully utilized;
2, measuring equipment is not neat and accurate, resulting in unreasonable materials;
3. The varieties and specifications of materials do not match, resulting in superior materials and inferior use, overqualified materials and inferior materials, and high-grade materials replace low-grade materials;
4, lamp supply management
Measures:
1, take technical measures to save materials. In terms of cement and concrete, optimize the concrete mixture ratio; Reasonable selection of cement grade; Make full use of cement activity and abundance coefficient; Choose good aggregate particle gradation; Strictly control the water cement ratio; Admixtures should be added reasonably and mixed materials, such as fly ash, should be added appropriately. On the reverse side of wood, steel is used instead of wood; Improve the formwork supporting method, adopting the formwork supporting methods such as bottomless formwork, brick tire formwork and moving formwork; Excellent materials are not inferior, and excellent talent is not short; Trade-in, comprehensive utilization, etc. In terms of steel, centralized cutting; Reasonable binding length shall be adopted when welding and binding; Make full use of old materials, short materials and scraps.
The volume of a material in an absolutely dense state refers to the volume excluding material pores. When measuring the density of porous materials, Lee's bottle can be used. Fill the bottom of the bottle with liquid medium until the liquid reaches the bottom zero mark, then pour the substance to be detected, and judge the volume of the poured substance according to the volume of the excluded liquid. The finer the material is ground, the more accurate the measured density value is.
In the natural state, the mass per unit volume is called apparent density.
Refers to powdery, granular or fibrous materials, such as sand, stone, cement, etc.
The ability of materials to resist external damage.
The property that a material deforms under the action of an external force and can be completely restored to its original state when the external force is removed is called elasticity.
This material will deform under the action of external force. If the external force is removed, the deformed shape and size are still maintained, and the property of not producing cracks is called plasticity.
Measures:
1, which provides the resistance of the material itself to external damage, such as improving the compactness of the material, changing the form of pore structure, and reasonably selecting the composition of raw materials.
2. Reduce the damage of environmental conditions to materials, such as special treatment of materials or taking necessary structural measures.
3. Add a protective layer on the surface of the main material, such as covering with thin wood and painting.
In civil engineering materials, all materials that can bond bulk or bulk materials into a whole through a series of physical and chemical actions are collectively called cementitious materials. It can be divided into organic gelation and inorganic gelation. It can also be divided into gas hardness and hydraulic hardness.
Commonly used pneumatic cementing materials. Lime with CaO as the main component was produced by calcining limestone.
Lime is white or light gray block with a density of about 3.2g/cm? Is the apparent density between 800~ 1000kg/m? . Uneven calcination temperature will produce undercooked lime, and too high temperature will produce overheated lime. Will affect the quality of the project.
The raw material contains some magnesium carbonate, which will produce MgO when calcined. When MgO is less than 5%, it is called calcareous lime, otherwise it is called magnesia lime.
When lime is used in the construction site, it is usually dissolved into paste or powdered hydrated lime by adding water. This process is called lime digestion, also known as solidification. The curing volume increased by 65438 0 ~ 2.5 times.
Lime slurry is called lime paste after it is precipitated in the ash storage pit and the upper water is removed. The apparent density of lime plaster is 1300~ 1400kg/m? . There is little quicklime in lime paste, which solidifies slowly. It usually takes more than two weeks to "age". During this period, the surface of lime slurry should be covered with a layer of water, isolated from air and carbonized.
The hardening of lime is caused by crystallization and carbonization.
The hardening of lime can only be carried out in air. The 28d compressive strength of lime mortar is usually only 0.2~0.5MPa.
Lime milk and lime mortar are made by mixing slaked lime powder or slaked lime paste with appropriate amount of water, which is called lime milk. It is a cheap and easily available paint, which is mainly used to paint interior walls and ceilings to increase the beauty and brightness of the room. It is also used for the exterior wall of China farm. Lime plaster and sand are mixed with water, which can be divided into masonry mortar and plastering mortar according to their uses.
Gypsum is a kind of pneumatic cementitious material with calcium sulfate as the main component.
The setting and hardening speed of building gypsum is fast, with initial setting 10min and final setting less than 30min. Usually the apparent density of gypsum after hardening is 800 1000kg/m? The compressive strength is 3 5MPa. There are a lot of micropores in gypsum hardened body, which has good heat insulation and sound absorption performance.
Commonly used in indoor partition board and ceiling board. Gypsum is slightly acidic, can not be reinforced, and its own strength is low, so it can not be used as a load-bearing structural material.
Water soluble silicate. It can be divided into liquid water glass and solid water glass.
It is often used to reinforce soil and improve the bearing capacity of foundation. Brush the surface of the material to improve the weather resistance of the building. Prepare waterproofing agent for plugging. Preparing sodium silicate slag mortar to repair cracks in brick walls. Prepare mortar and concrete for special purposes.
All hydraulic cementing materials made of portland cement clinker, 0~5% limestone or granulated blast furnace slag and appropriate amount of gypsum are called portland cement. Type I Portland cement without admixture, and type II Portland cement with limestone or granulated slag admixture not exceeding 5% by weight of cement, code-named P.I and P.II. Portland cement is commonly known as Portland cement abroad.
The raw materials are mainly calcium and clay. Calcareous raw materials include limestone, chalk and calcareous tuff. Mainly for Cao. 1T clinker needs 1. 1. 1.3t limestone; Clay raw materials include all kinds of clay, loess and so on. Silica, alumina and iron oxide are mainly provided, and 1T clinker needs 0. 30.4 t. ..
According to the preparation method of raw materials, it can be divided into wet method and dry method, the former is more uniform and the latter is more energy-saving. The latter is a common method.
Kilns can be divided into rotary kiln and vertical kiln. The former is used in large and medium-sized cement plants, while the latter is used in local cement industry. The former has high yield and good quality. The latter has simple equipment and less investment.
The main factors affecting the setting and hardening of cement include mineral composition, gypsum, cement fineness, ambient temperature, humidity and time.
A certain amount of mixed materials and appropriate amount of gypsum are mixed into portland cement clinker, and the hydraulic cementing materials made by grinding are all portland cement mixed with mixed materials.
All hydraulic cementing materials made of portland cement clinker, 6%~ 15% admixture and appropriate amount of gypsum are called ordinary portland cement, which is called ordinary cement for short and code-named P O.
Granulated blast furnace slag is called slag cement, code named P.S. Blast furnace slag with 20%~70% content.
Doped volcanic rocks, code name p.p. Add 20%~50% volcanic rocks.
Adding fly ash, code name p.f. adding 20%~40% fly ash.
The ratio of cement mixed with mixed materials to ordinary cement has the following characteristics:
1, setting and hardening speed is slow.
2. The release rate of hydration heat is slow, with less heat release.
3, sensitive to temperature
4. Strong erosion resistance
5. Poor frost resistance and carbonation resistance.
Mixing two or more kinds of mixed materials is called composite portland cement, which is called composite cement for short, and its code name is P.C. The doping quality is 15%~50%.
Portland cement for road is a cement with calcium silicate as the main component and a lot of calcium and iron aluminate added.
Medium and low heat cement, limit tricalcium aluminate and tricalcium silicate, reduce hydration heat release rate and heat release. be used for
Hydraulic structures such as ports, docks and dams. It has a large concrete volume and controls heat release and cracks.
Made of white silicate clinker, it is white portland cement, referred to as white cement.
Fast-hardening sulfate cement is mainly used for emergency repair and winter construction.
Classification by bulk density: density >; 2600kg/m？ Heavy concrete, density 1900 2500kg/m? Ordinary concrete, the density is between 500 1900kg/m? Is it lightweight concrete with a density of 300~ 1200kg/m? This is porous concrete.
According to the composition materials: fiber concrete, polymer concrete, silicate concrete, lightweight aggregate concrete, AE concrete (including aerated concrete).
According to the use characteristics, it can be divided into impervious concrete, waterproof concrete, concrete poured in winter, concrete poured in summer, mass concrete, expansive concrete, radiation-proof concrete, heat-resistant and fire-resistant concrete and acid-resistant and alkali-resistant concrete.
According to the production and construction methods: ready-mixed concrete, pressure grouting concrete, prestressed concrete, precast concrete, aerated concrete, hot mixed concrete, pumping concrete, shotcrete, paving concrete and roller compacted concrete.
Concrete consists of four basic components: cement, water, aggregate and voids.
The particle size range of fine aggregate is 0.15 5 mm, such as natural sand and stone chips; The particle size range of coarse aggregate is 5 150mm, such as pebbles and broken pebbles. Sandstone accounts for 65%~70% of the total volume of concrete.
Factors affecting concrete leakage:
1, water cement ratio. The larger the water-cement ratio is, the larger the seepage channel may be formed. When the water-cement ratio is greater than 0.6, the impermeability drops sharply.
2, the largest particle of aggregate. The bigger the crack, the more serious the water seepage.
3. Cement varieties. The pores of hardened cement paste are different with different fineness, and the larger the fineness, the smaller the pores.
4. Maintenance conditions. In the case of dryness or low humidity, concrete loses more water in the early stage, which is easy to form shrinkage cracks and reduce impermeability.
5. Additives. Water reducing agent, reduce water cement ratio and improve compactness. Air entraining agent can cut off the pore channels and improve the impermeability.
6. Additives. Adding high-quality fly ash can improve the compactness.
Impermeability. P4, P6, P8, P 10, P 12, which can resist the water pressure of 0.4, 0.6, 0.8, 1.0, 1.2MPa, and is impervious to water.
Frost resistance grade. Nine grades, such as F 10, F 15 and F300, show that it can withstand 10, 15 and 300 repeated freeze-thaw cycles.
The main wear forms of road concrete are fatigue wear and abrasive wear.
Development stages of high strength concrete;
1, in the first stage, the water-cement ratio was reduced by strong stirring and vibration pressurization to obtain high strength.
2. In the second stage, high strength concrete is prepared with superplasticizer.
3. In the third stage, high strength concrete is prepared by adding chemical admixture and mineral superfine powder admixture, which is the so-called double mixing technology.
Technical approaches of high strength concrete;
1, reduce the water cement ratio
2. Choose high strength cement.
3, adopt high-activity superfine mineral admixture.
4. The mineral composition and particle size of high-quality coarse aggregate have great influence on the strength of concrete.
The tension-compression ratio of high-strength concrete is lower than that of ordinary concrete. The higher the strength, the smaller the tension-compression ratio and the greater the brittleness, which is the fatal disadvantage of high-strength concrete.
Lightweight concrete has low apparent density, low thermal conductivity and good thermal insulation, sound insulation and seismic performance. Mainly used in building construction and various lightweight precast concrete components.
It is divided into lightweight aggregate concrete and porous concrete.
Lightweight aggregate concrete refers to lightweight aggregate, cement and water, and its dry apparent density is not more than 1950kg/m? . Fly ash ceramsite concrete, clay ceramsite concrete, pumice concrete, expanded perlite concrete, etc.
Porous concrete refers to lightweight concrete filled with a large number of tiny bubbles and without aggregate, with a porosity of 85% and an apparent density of 300~ 1200kg/m? . Mainly used as thermal insulation materials, but also as structural materials.
According to different pore-forming methods, porous concrete can be divided into aerated concrete and foamed concrete.
Aerated concrete is made of calcium-containing materials (cement, lime) and silicon-containing materials (quartz sand, fly ash, slag, etc.). ) and air entraining agent are ground, mixed, stirred, poured, cut and autoclaved for curing.
According to the function is divided into four categories:
1, an additive to improve the rheological properties of concrete mixture. Include various water reducing agents, air entraining agents and pumping agents.
2. Additives for adjusting the setting time and hardening performance of concrete. Comprise a retarder, an early strength agent and an accelerator.
3. Admixtures to improve the durability of concrete. Include air entraining agent, waterproof agent, rust inhibitor, shrinkage reducing agent, etc.
4. Admixtures to improve other properties of concrete. Include air entraining agent, expansion agent, antifreeze, colorant, waterproof agent and pumping agent.
Water reducing agent refers to an additive that can reduce and improve the consistency of concrete.
The function of water reducer: increase fluidity, improve concrete strength, save cement and improve concrete durability.
Admixtures that accelerate the early strength development of concrete and have no obvious influence on the later strength.
Mortar that can bond bricks, test blocks and blocks into masonry is called masonry mortar. It plays the role of bonding, buffering and transferring stress.
Cement, admixture, sand, admixture, water
1, workability of fresh mortar, including fluidity and water retention.
Also known as plastering mortar. Divided into ordinary, decorative, waterproof and other special. It is divided into cement, mixture, lime and cement fine stones.
Composition materials: cementing materials (such as cement), sand and reinforcing materials (such as hemp knives, paper tendons and glass fibers).
Composition of decorative mortar: cement, synthetic resin, sand and pebbles.
It can be divided into sintered bricks and non-sintered bricks, hollow bricks and solid bricks.
Clay, shale, coal gangue and fly ash are the main raw materials. It is made by preparation, molding, drying and roasting.
The standard size is 240mm 1 15mm 53mm. Generally, 240mm 1 15mm is called bedding face, 240mm 53mm is called strip face, and 1 15mm*53mm is called top face.
Autoclaved lime-sand brick takes lime and sand as main raw materials.
Fly ash block, small concrete block, autoclaved aerated concrete block.