inorganic materials

organic material

composite materials

building structural materials

Wall Materials

Building functional materials

Building materials industry enterprises: They must design and produce in strict accordance with technical standards to ensure product quality and produce qualified products.

Users of building materials: They must select and use materials of qualified quality according to technical standards, and standardize design and construction to ensure project quality, speed up construction progress, and reduce project costs.

Building material suppliers and buyers: Materials must be inspected and accepted in accordance with technical standards to ensure the legitimate rights and interests of both parties.

ρ. —The apparent density of the material, g/cm3 or kg/m3 m —The mass of the material in its natural state, g or kg V. —The volume of material in its natural state, cm3 or m3

Vernier caliper method (regular shape body)

Wax sealing method (irregular shapes)

Concept: The degree to which the volume of a material is filled with solid matter

Formula: D=v/v. ×100%

Concept: refers to the percentage of the volume of internal pores in the material to the total volume of the material

Porosity reflects the structural density of a material

The greater the porosity

The lower the intensity

When in contact with water, the property that the material surface can be wetted by water is called hydrophilicity;

The property that the surface of a material cannot be wetted by water is called hydrophobicity.

The smaller the wetting angle θ, the easier it is to be wetted. The wetting angle is at the interface of material, air and water.

The ability of a material to absorb water when immersed in water is called the water absorbency of the material

The property of a material to absorb moisture in humid air is called hygroscopicity

Water Absorption and Hygroscopic Moisture Content

Material pore characteristics

Porosity

The smaller the permeability coefficient, the better its anti-permeability performance

The greater the open porosity, the greater the water absorption rate

The larger the softening coefficient, the better the water resistance.

After the material absorbs water, the apparent density and thermal conductivity of the material will increase.

×, for concrete materials, the permeability coefficient should be used to characterize its impermeability

Shear resistance

1. The composition, structure and construction of materials.

2. Porosity and pore characteristics. (High void ratio, low strength)

3. The shape and size of the test piece. (Prism <cube)

4. Loading speed. (Fast speed, high strength when destroyed)

5. Temperature and humidity of the experimental environment. (high temperature, low intensity)

6. The state of the force-bearing surface. (Flat surface has high strength)

The flexural strength of the material is related to the stress condition, cross-sectional size and support conditions of the specimen.

For materials of the same quality, the greater the apparent density value, the smaller the porosity (that is, the denser the structure), so the higher the strength.

elasticity

Plasticity: permanent deformation

most materials First undergo elastic deformation, then plastic deformation

brittleness

toughness

Xu Bian

stress relaxation

K soft - softening coefficient. fb——The compressive strength of the material in the water-saturated state. (Mpa) fg——Compressive strength of material in dry state (Mpa)

×, for concrete materials, the permeability coefficient should be used to characterize its impermeability

K--permeability coefficient (cm/h); Q--amount of water seepage (cm3); A--water seepage area (cm2); d--thickness of specimen (cm) H--water pressure difference on both sides of the material (cm) ;t--water seepage time (h)

The smaller k is, the stronger the impermeability is.

In the concrete impermeability test, water seepage appeared on 2 surfaces of 6 specimens in each group. (i.e. no water seepage occurs on the 4 surfaces) expressed as 10 times the maximum water pressure (MPa).

For example, W2, W4, W6, w8, W10, and W12 respectively indicate that the maximum pressure that the specimen can withstand is 0.2MPa, 0.4MPa, 0.6MPa, 0.8MPa, 1.0MPa, 1.2MPa water pressure without penetration.

Material hydrophilicity and hydrophobicity

density of material

Material pore characteristics

main elements

F50, F100, F150, F200, F250, F300 level six

①Denseness of the material: The higher the density (the smaller the porosity), the smaller the frost resistance.

②Porosity characteristics of the material: The more open pores, that is, connected pores, the worse the frost resistance.

③Strength of the material: The higher the strength, the better the frost resistance.

④Water resistance of the material: The better the water resistance, the better the frost resistance.

⑤The amount of water absorption of the material: the greater the water absorption, the worse the frost resistance (water absorption saturation makes the frost resistance worse)

chemical components

mineral composition

Crystal structure

amorphous structure

Colloidal structure

Their microstructure is different

All amorphous materials are isotropic

Crystals have a definite melting point while amorphous crystals do not have a definite melting point

From a microstructure perspective, construction steel has a crystal structure, while fresh cement slurry has a colloidal structure.

×All crystal materials are anisotropic

natural rock

masonry stone

decorative stone

physical properties

mechanical properties

Classification by production process

According to roasting temperature

According to color

Divided according to porosity rate

Ordinary fired bricks

Sintered porous bricks and hollow bricks

Autoclaved lime sand brick

fly ash bricks

cinder block

After a series of physical and chemical changes, it can solidify and harden, and the block or powdery materials can be cemented together to form a whole material.

Inorganic cementitious materials

Organic cementitious materials (asphalt, polymers)

Raw material CaCO3

Production process - calcination The lime production process is a limestone calcination process. According to the degree of calcination, it can be divided into underfired lime, normalized lime and overfired lime.

①Lumpy quicklime

Lime paste, hydrated lime powder, quicklime powder

The slaking process of lime: quicklime water = slaked lime

Lime slaking method

Treatment of over-fired lime and under-fired lime

Things to note during the aging process

hardening process

Carbonization hardening proceeds slowly "from the outside to the inside" → After the mortar joints of masonry mortar and plastering mortar harden, there is still uncarbonized Ca(OH)2 component.

Thinking: Why is lime mortar plastering prone to cracking, shelling, and peeling in an environment that has been exposed to moisture for a long time? Under the action of moisture in a humid environment, the uncarbonized and hardened Ca (OH)2 dissolves in water, resulting in a reduction in the strength of the structure → resulting in mortar cracking, shell jumping, peeling and other phenomena.

Lime quality grade

Properties of lime

Application of lime

·Do not mix, store or transport with flammable, explosive and other dangerous liquid items.

·The storage time of quicklime should not be too long, generally no more than one month. Achieve "change as you go".

·Hydrated lime must be aged for more than two weeks before use to prevent the damage caused by burnt lime to the building.

Quicklime should be stored in a dry warehouse to protect it from water and moisture. When the storage time is long, it is best to digest it into lime paste in the ash tank, and cover the surface with a permanent film to isolate the air and prevent carbonization.

The production of gypsum cementitious materials is usually made by calcining, dehydrating and then grinding dihydrate gypsum at a certain temperature and pressure.

·Under different calcination temperatures, the products obtained are different. The specific process is as follows:

·Building gypsum is commonly used in construction projects; high-strength gypsum is used to produce building gypsum products.

Condensation of building gypsum: it is a process of dissolution, reaction, precipitation and crystallization;

Gypsum hardening: It is the formation process of the crystal structure network between the dihydrate gypsum crystals.

(Crystals intersect with each other to form a network structure; as the reaction continues, The crystal structure network gradually becomes denser, causing the gypsum crystals to gradually harden. )

Technical properties of construction gypsum

Application of Gypsum

·The modulus n of water glass: refers to the ratio of the number of molecules of silicon oxide and sodium oxide in sodium silicate (Na, OnSiOz), which is generally between 1.5 and 3.5.

Formulate heat-resistant concrete or serve as a setting accelerator for cement

for foundation grouting

For painting material surfaces

Liquid water glass absorbs carbon dioxide in the air to form an amorphous silicate gel, which gradually dries and hardens. The specific reaction formula is as follows:

In order to accelerate the hardening of water glass, it can be heated or mixed with 13% to 15% of the hardening accelerator sodium fluorosilicate.

Properties of water glass

Application of water glass

Cement concrete, clay bricks, silicate products, stone

·Cement is a powdery material. The slurry formed after adding water and mixing evenly can not only solidify and harden in a dry environment, but also harden better in water, maintain and develop its strength, and form a hard artificial stone.

·It is not only suitable for engineering parts in dry environment, but also suitable for engineering parts in humid environment and water.

Universal cement

Special cement

Characteristic cement

Hydraulic cementitious materials

General portland cement is divided into types and amounts of mixed materials ·Portland cement (P.I, P.IⅡ) Ordinary Portland cement (P.O) ·Slag Portland cement (P.S.A, P.S.B) Pozzolanic Portland cement (P.P) Fly ash Portland cement (P.F) Composite Portland cement (P.C)

Portland cement clinker minerals

2.Gypsum

3. Active mixed materials

·Any artificial or natural mineral material that has no activity or very low activity, and is ground into fine powder and mixed with lime, gypsum or Portland cement with water, can not or rarely generate hydraulic gelling substances. , called inactive mixed materials.

·Commonly used inactive mixed materials include: those whose activity indicators are lower than those required by GB/T203, GB/T18046, GB/T1596, and GB/T2847 standards respectively. Granulated blast furnace slag, granulated blast furnace slag powder, fly ash, pozzolanic mixed materials; limestone and sandstone, of which the aluminum oxide content in the limestone should not exceed 2.5%.

·The main purposes of adding inactive mixed materials are: filling, increasing cement output, adjusting (and certainly improving) cement strength grade, Reduce cement costs and heat of hydration, turn industrial waste into treasure, improve certain properties of cement, etc. (excluding increasing cement density)

·Kiln dust is dust collected from the exhaust gas of cement rotary kiln and should comply with the regulations of JC/T742. The performance of kiln dust is between active mixed materials and inactive mixed materials. The main components are calcium carbonate, dehydrated clay, glassy substances, calcium oxide, and a small amount of clinker minerals, alkali metal sulfates and gypsum. . The technical properties comply with the requirements of JC/T742.

·Admixtures added during cement grinding to aid grinding without damaging the properties of cement. Grinding aids are allowed to be added during cement grinding, and the amount added should not exceed 0.5% of the cement mass and should comply with the regulations of JC/T667.

①Soft water corrosion (dissolution corrosion)

②Acid attack (dissolution attack)

③Salt erosion

④Strong alkali erosion

internal cause

external factors

① According to the environmental characteristics of the project, rationally select cement varieties.

②Improve the density of cement stone.

③ Set a protective layer on the surface of the cement stone structure.

In order to avoid the flash setting phenomenon of general Portland cement, an appropriate amount of gypsum is often added to the cement for adjustment. The principle of its action is to use the hydration of gypsum and the (C3A) component in the mineral composition of cement clinker to form ettringite. , thereby inhibiting the hydration process of cement.

cement stone

Factors affecting cement setting and hardening

Related statements about cement stone corrosion

Cement slurry preparation:

When measuring cement standard consistency water consumption, setting time, and stability, the standard test conditions are: (see GB/T1346-2011)

·Test room: 20℃±2℃, relative humidity not less than 50%. ·Moisture curing box: 20℃±1℃, relative humidity not less than 90%.

Vicat

Standard consistency water consumption: The amount of water required when the cement slurry reaches the specified "standard consistency". → Expressed by "the percentage of mixing water volume and cement mass".

Adjust the amount of water to 500g of cement and add water to prepare the pure slurry) The control standard for the test standard consistency is ·Standard method: The test rod is sunk into the clean slurry and the bottom is 6±1)mm. ·Usage: Test the cone sinking depth (30±1)mm.

·Initial setting time is the time from adding water to when the cement slurry begins to lose its plasticity. ·Final setting time is the time from adding water to the time when the cement slurry completely loses its plasticity.

Initial setting time measurement:

Final setting time determination:

construction

·Stability refers to the uniform change in volume of cement slurry when it hardens. ·Poor stability of cement will affect the quality of the project (causing expansion cracks in cement products and concrete components), and even cause serious engineering accidents. →Cement with poor stability is strictly prohibited from being used in projects.

Reasons for poor cement stability:

Boiling method to test stability Boiling: Heat to boiling within 30 minutes ± 5 minutes, and maintain constant boiling for 180 minutes ± 5 minutes.

Testing methods for cement stability:

Fineness refers to the thickness of cement particles

The thickness of cement particles directly affects its hydration reaction speed, activity and strength.

Testing method for cement fineness

①Sand test piece 40×40x160mm

Maintenance conditions: 20±1℃ before mold removal, relative humidity above 90%. After removing the mold: Constant temperature water tank (20±1℃, no more than 50% of the water can be replaced during curing) The strength grade of general Portland cement is evaluated based on the flexural strength and compressive strength at two ages: 3d and 28d.

Heat of hydration: refers to the heat released during the hydration process of cement

The heat of hydration is related to the relative content of clinker minerals

The impact of hydration heat on engineering

The density and bulk density of cement are two important physical indicators, which are used in the design of concrete and mortar mix ratios and the storage and transportation of cement.

Chemical indicators

Clotting time

Stability

strength

Any item that does not meet the requirements is deemed to be unqualified.

Fast setting and hardening, high strength → suitable for projects with early strength requirements.

Good frost resistance → Suitable for hydraulic concrete and projects with high frost resistance requirements.

Good wear resistance → Suitable for highways, roads and ground engineering.

Good carbonation resistance. Because the calcium hydroxide content is high after hydration, the alkalinity of the cement stone is not easily reduced and has a strong protective effect on the steel bars. →Suitable for environments with high carbon dioxide concentration in the air.

High heat of hydration → not suitable for use in large-volume concrete projects. But it is beneficial to the construction of heat storage method in low temperature season.

Poor heat resistance. Because the calcium hydroxide content is high after hydration. →Not suitable for concrete projects that are subject to high temperatures.

Poor corrosion resistance

The early intensity is slightly lower and the later intensity is higher.

The heat of hydration is slightly lower.

It has good impermeability, good frost resistance and strong carbonization resistance.

Corrosion resistance is slightly better.

Good wear resistance; good heat resistance.

The application range of ordinary Portland cement is the same as that of Portland cement.

Common characteristics:

Various features

The Ca(OH)2 content is lower and the structure is denser

The main types of erosion suffered by the cement stone structure of the reinforced concrete used in cross-sea bridges are ().

The main types of erosion suffered by the cement stone structure of the concrete used in the water conveyance tunnel of the reservoir project are ().

Aluminum Portland cement

Slag Portland cement, fly ash Portland cement

In environments with sulfate corrosion, () should be used.

In emergency repair projects, it should be used when preparing concrete.

Portland cement should not be used in the following projects:

The later strength development of fly ash Portland cement is faster than that of ordinary Portland cement. The main reason is that () more and more cementitious substances are generated.

For concrete projects with wear resistance requirements, the cement that should not be used is ().

Road Portland cement, general Portland cement

Do not mix for storage and transportation: avoid misuse.

Do not mix: Different varieties and grades of cement from the same manufacturer cannot be mixed; Cement of the same variety and grade but from different manufacturers must not be mixed.

Usually, the strength of cement stored for three months decreases by 10 to 20%.

Generally, the strength of cement stored for six months decreases by 15 to 30%.

Under normal conditions, the storage period of general Portland cement should not exceed (3) months.

It is composed of cement, sand, gravel and water, which is evenly mixed, densely formed, and hardened to form an artificial stone with a certain strength and durability. Also known as cement concrete, or simply "concrete".

Cement concrete, asphalt concrete, polymer concrete, polymer impregnated concrete, etc.

Fly ash concrete, silica fume concrete, ground slag concrete, fiber concrete, steel fiber concrete, etc.

Structural concrete, thermal insulation concrete, decorative concrete, large volume concrete, hydraulic concrete, marine concrete, road concrete, waterproof concrete, heat-resistant concrete, acid-resistant concrete, radiation-proof concrete, etc.

Ready-mixed concrete, on-site mixed concrete, commercial concrete, pumped concrete, sprayed concrete, roller compacted concrete, etc.

Plain concrete, reinforced concrete, steel mesh concrete, fiber concrete, prestressed concrete, etc.

Concrete partition walls are suitable for light concrete pouring

Plastic concrete (slump 10~90mm) Fluid concrete (slump 100~150mm) High fluidity concrete (slump ≥160mm) Dry hard concrete (slump <10mm)

Ordinary concrete

high strength concrete

ultra high strength concrete

①Raw materials are abundant and cost is low; ②It has good adaptability and the concrete mixture has good plasticity; ③ Bonds well with steel bars and generally does not corrode steel bars; ④High compressive strength and good durability; ⑤Convenient construction.

① Self-heavy weight (apparent density is about 2400kg/m3);

② It is a brittle material with low tensile strength (about 1/10 to 1/20 of the compressive strength) and poor deformation resistance;

③High thermal conductivity; ④Slow hardening;

⑤The production cycle is long and the quality of the construction process is difficult to control.

The main factors that should be considered when choosing cement are the uses of concrete;

Based on the above factors, →appropriately select the type and strength grade of cement.

According to different water sources, concrete mixing water and curing water are divided into: drinking water, surface water, underground water, recycled water, concrete enterprise equipment washing water and sea water, etc.

definition

Classification

Fine aggregate and coarse aggregate 1-6

Among natural sand, pebbles, and gravel, particles with a particle size <75um → mud content.

In machine-made sand, particles with particle size <75um → amount of stone powder and mud.

definition

Detection

If the total surface area and void ratio of sand and stone are small, the amount of cement slurry used to fill the voids and wrap the surface can be reduced (that is, cement can be saved).

Influence

Robustness

Grading

Rapid method test: Add 30ml of methylene blue solution to the suspension in the beaker at one time, stir continuously at 400mlmin for 8min → then use a glass rod to pick up a drop of the suspension, drop it on the filter paper, and observe whether there is an obvious color halo around the precipitate. →If there is obvious color halo, the methylene blue rapid test is judged as "passed". If there is no obvious color halo, the methylene blue rapid test is judged to be "unqualified".

It is in the form of flakes with smooth surface and low bonding force with cement stone, which will reduce the strength and durability of concrete. Testing: Depending on the thickness of the sand, take 10-20g of a dry sample of 0.35-5mm, pick out the mica under a magnifying glass, and measure its content.

Substances with an apparent density less than 2000kg/m3 (such as coal, lignite, etc.). →It is light in weight, has weak particles, and has low bonding force with cement stone, which reduces the strength and durability of concrete. Detection: Use a zinc chloride solution with an apparent density of 2000kg/m3 for separation.

Its soluble substances will react with cement hydration products and corrode the cement stone.

Can cause corrosion of steel bars in reinforced concrete.

It is the percentage of the mass of sand in concrete to the total mass of sand and stone.

The commonly used fineness modulus (Mx, u or FM) indicates the average thickness of sand particles of different particle sizes when mixed together, but it cannot indicate the quality of the gradation.

The fineness modulus of sand decreases, the finer the sand → the finer the sand, The greater the total surface area and void ratio of the sand, and thus the greater the amount of cement slurry required in the concrete (that is, a waste of cement).

The commonly used grading area (or cumulative sieve residue percentage) represents the combination of sand particles of different particle sizes.

Fineness modulus = average score, particle grading = scores in each subject

Nominal particle size of coarse aggregate

Grading of coarse aggregate

The selection of the maximum particle size of coarse aggregate will directly affect the amount of cement. When the maximum particle size increases, the total surface area of ​​the aggregate decreases, and the amount of cement slurry required to wrap its surface will decrease, saving cement and cost.

The upper limit of the nominal particle size of coarse aggregate is called the maximum particle size of coarse aggregate. P73

Oversized particles and undersized particles

sodium sulfate solution method

Crushing index method

The particle shape and surface characteristics of the aggregate → will affect its bonding with the cement stone and the fluidity of the concrete mixture.

Needle-shaped particles: particles in coarse aggregate whose length is greater than 2.4 times the average particle size of the particle size.

Flaky particles: Particles in coarse aggregate whose thickness is less than 0.4 times the average particle size of the particle size.

Adverse effects:

Apparent density

Bulk density

Loading: Load the sample evenly into 2 layers (each layer is 1/2 of the tube height).

Compressive strength value

·Crushing index value

Because the bonding force between pebbles and cement stones is lower than the bonding force between gravel and cement stones, under the same conditions, for medium and low strength concrete, the strength of pebble concrete is smaller than the strength of crushed concrete.

concept

fluidity

cohesiveness

Water retention

Easy to reach uniform structure

Ensure the quality of concrete after hardening

Evaluation methods and indicatorsP79

Selection of fluidity (slump) indicators

Factors affecting the workability of concrete mixture P79

Measures to improve the workability of concrete mixtures83

When the concrete mixture has good cohesion, no bleeding, and the slump is too small, the available measures are: appropriately increase the amount of cement slurry while keeping the water-cement ratio unchanged.

As the fluidity of ordinary concrete increases, its water retention will become worse.

When there is slurry in the concrete mixture and the concrete cone collapses and loosens in the slump test, the amount of sand should be kept unchanged and the sand rate should be increased appropriately.

The larger the slump, the better the fluidity of the concrete and the easier the construction. However, if the slump is too large, it will be accompanied by concrete slurry and bleeding (i.e., deterioration of cohesion and water retention), which will worsen the compactness and uniformity of the concrete after vibration.

·The setting time of the concrete mixture is related to the setting time of the cement used, but it is not consistent. ·Setting time of concrete mixture: measured by "penetration resistance method".

1. Cube compressive strength and strength grade

2 Axial compressive strength of concrete

3Splitting tensile strength

4 Factors Affecting the Compressive Strength of Concrete

5 Measures to Improve Concrete Strength

Chemical shrinkage (autogenous volumetric deformation)

Dry and wet deformation (physical shrinkage) Concrete shrinkage cracks are caused by physical shrinkage

temperature deformation

Deformation under short-term loading (elastoplastic deformation)

Deformation (creep) under long-term loading

Definition: The ability of concrete to resist the effects of environmental factors and maintain its good performance and appearance integrity, thereby maintaining the safety and normal use of the concrete structure, is called the durability of concrete.

1.Impermeability

2. Frost resistance

The main measures to improve the impermeability and frost resistance of concrete are ()

3. Anti-wear and anti-cavitation properties

4.Corrosion resistance

5. Carbonization of concrete

Alkali-aggregate reaction

Water-cement ratio is too large → concrete strength and durability are reduced, and the mixture has poor water retention

Water-soluble admixtures: should be prepared into a solution of a certain concentration first and then added to the mixer with water.

Water-insoluble admixtures: should be mixed evenly with an appropriate amount of cement or sand, and then added to the mixer.

① The effect of the co-mixing method is poor and the slump loss is large.

②Standing water mixing method

③Post-doping method

"Concrete slump loss" - the phenomenon that the workability of a concrete mixture decreases as the concrete is parked for longer.

concept

Mechanism of action

Technical and economic effects

(1)Definition

During the concrete mixing process, admixtures can be introduced that can introduce a large number of evenly distributed, stable and closed tiny bubbles and can be retained in the hardened concrete - called "air-entraining agents".

(2) Effect

Comparison of applicability of air-entraining agent and water-reducing agent

Pumping agents refer to admixtures that can improve the pumping performance of concrete mixtures.

Requirements for pumping concrete: large slump, good cohesion, low bleeding rate, etc.

Components: The special pumping agent is composed of fluidization component, air entrainment component, retardant component, and other components (such as early strength component, antifreeze component, etc.).

Admixtures that accelerate the early strength development of concrete—early strength additives

The commonly used early strength agents in my country are mainly sodium sulfate admixtures. When using them, you should pay attention to the following issues:

1. Suitable for concrete construction in environments where the daily minimum temperature is not lower than -5℃; 2. It must be mixed with dry powder and the mixing time should be appropriately extended. When mixing, it should be mixed into cement and should not be added to wet sand and gravel. When there are agglomerates and coarse particles in the powder, it must be crushed and passed through a 30-mesh sieve. can be used.

Admixture that can quickly set and harden concrete

Purpose: Leak plugging and emergency rescue projects; Preparation of shotcrete

Retarder is an admixture that can delay the setting time of concrete.

Retarder is mainly used for large-volume concrete and concrete construction in hot climates, as well as concrete projects that require long-term parking or long-distance transportation.

·Expansion agents are mainly suitable for preparing shrinkage-compensating concrete (mortar) and self-stressing concrete (mortar) to reduce dry shrinkage cracks in concrete (mortar) and improve crack resistance and permeability.

·At present, the applicable temperature range of domestic concrete antifreeze is -20℃~0℃.

Contraindications for use:

·The mineral powder whose mass is greater than 5% of the cement mass when mixing concrete (mortar) is called concrete admixture.

·Incorporating admixtures into concrete has significant technical, economic and environmental benefits. It can often save cement, improve concrete properties, and adjust concrete strength levels.

Equivalent substitution method

Additive method

excess substitution method

When reinforced concrete is mixed with fly ash, it is often also mixed with rust inhibitors; Fly ash concrete under low temperature conditions is suitable to be mixed with early strength agent or antifreeze agent at the same time.

The mixing technology of mixing admixtures and admixtures into concrete at the same time is called "double mixing technology".

①Improve the pore structure of concrete and improve durability.

③Improve the strength of concrete.

Suitable for preparation: high flow concrete, pumped concrete and underwater pouring concrete, etc. (In order to maintain the fluidity of concrete, it must be used in conjunction with a high-efficiency water reducing agent to achieve good results)

Can be used in: foundation grouting projects to improve groutability.

Because silica fume has extremely fine particles and high activity, it can significantly increase the strength of concrete. Therefore, silica fume can often be mixed into high-strength concrete.

After incorporating silica fume, the pore structure of cement stone can be significantly improved (macro pores are reduced and micro pores are increased), so the durability of concrete can be improved.

Applies to:

The incorporation of silica fume can reduce the rebound amount of shotcrete, thereby increasing the thickness of the shotcrete and shortening the construction period.

Can be used for: shotcrete projects.

① Silica fume concrete is prone to plastic cracking and early shrinkage, so early maintenance must be strengthened during the construction process.

② Silica fume requires a large amount of water. In order to maintain the fluidity of concrete after mixing, it must be used in conjunction with a high-efficiency water-reducing agent.

Under normal construction conditions, concrete strength fluctuations conform to the normal distribution.

standard value

average value

Dispersion coefficient

The standard deviation of concrete strength σ or the dispersion coefficient Cv is an important parameter that determines the strength distribution characteristics. In construction quality control, σ or Cv can be used as an index to evaluate the uniformity of concrete.

(For ordinary concrete projects, P=95% is required, and the probability t=-1.645 at this time).

1. Application of statistical method ①: When the production conditions of continuously produced concrete remain consistent over a long period of time, and the strength variability of concrete of the same variety and strength grade remains stable: Requirement: The sample size in the previous inspection period should not be less than 45 groups.

2. Application of statistical method ②: other situations When the sample size is no less than 10 groups, its strength should simultaneously meet the following requirements:

Application of non-statistical methods: When the sample size used for evaluation is less than 10 groups, non-statistical methods should be used to evaluate concrete strength.

When assessing the strength of concrete using non-statistical methods, its strength should simultaneously meet the following requirements:

It refers to the proportional relationship between each group of materials in concrete.

Method ①: Expressed by the actual amount of each component material in 1m3 of concrete.

Method ②: Expressed by the ratio of the dosage of each component material.

Meet the workability requirements for concrete construction

Meet the strength level requirements of structural design

Meet the durability requirements of concrete in the environment where the project is located

The mix ratio is economical and reasonable to save concrete costs.

Cement varieties

power level

Cement dosage

Mortar for stone masonry

Mortar for brickwork

Mortar for plastering and jointing

When high-strength grade cement is used to prepare low-strength grade mortar → due to the small amount of cement, the mortar is prone to delamination, segregation and bleeding.

In order to improve the workability of mortar, save the amount of cementitious materials, and reduce the cost of mortar, certain admixtures can be added when preparing mortar. (Such as: ground quicklime, lime paste, gypsum, fly ash, clay paste, electrogypsum, etc.).

In the preparation of masonry mortar, the standard consistency of lime paste during trial preparation should be (120±5)mm.

In order to improve the workability of fresh mortar and the various properties of hardened mortar or to give the mortar some special properties, an appropriate amount of admixtures (such as water-reducing agent, air-entraining agent, micro-foaming agent, waterproofing agent) can be added to the mortar. wait).

In concrete repair and reinforcement, adding certain polymers (such as epoxy resin, polyester resin, etc.) into the mortar can significantly improve the adhesion, toughness, impact resistance and durability of the mortar.

Water for mixing mortar: The requirements for water for mixing concrete are the same.

Mortar with better workability should have a greater degree of sinking and less degree of delamination.

Compared with ordinary concrete, the constituent materials of cement mortar lack coarse aggregate. Therefore, the evaluation of cohesion is not involved in the evaluation of the workability of mortar.

fluidity

Water retention

In order to improve the workability of masonry mortar and save the amount of cement, () is often added.

Before laying an ordinary brick wall, the bricks should generally be watered and moistened, and the purpose is ().

Mortar Strength and Strength Grades

Adhesion Bonding strength

example

Compared with concrete, the strength of masonry mortar should be mainly considered (bonding strength) in addition to compressive strength.

Deformation performance and durability

Cement mortar: apparent density should not be less than 1900 kg/m3.

Cement mixed mortar: apparent density should not be less than 1800 kg/m3.

mix design

Mix ratio selection

A pressure processing method in which the metal blank passes through the gap between a pair of rotating rolling rollers (in various shapes) and is compressed by the rolling rollers to reduce the cross-section and increase the length of the material.

It is the most commonly used production method for producing steel and is mainly used to produce profiles, plates, and pipes. Divided into cold rolling and hot rolling.

A pressure processing method that uses the reciprocating impact of a forging hammer or the pressure of a press to change the blank into the required shape and size.

It is often used to produce materials with larger cross-sections such as large materials.

It is a processing method that draws the rolled metal blank (shaped, tube, product, etc.) through the die hole into a reduced cross-section and increased length.

It is mostly used for cold processing.

It is a processing method in which metal is placed in a closed extrusion cylinder and pressure is applied on one end to extrude the metal from a prescribed die hole to obtain finished products of different shapes and sizes.

It is mostly used in the production of non-ferrous metal materials.

Carbon steel

alloy steel

structural steel

tool steel

Special performance steel

Classification by smelting method

According to the degree of deoxidation

Ordinary steel

High quality steel

Advanced quality steel

Non-metal protective layer

metal protective layer

Tensile properties

Plasticity

Impact toughness

Fatigue resistance

hardness

Cold bending performance

Weldability: refers to whether the steel is suitable for common welding methods and processes. The weldability of steel is affected by its chemical composition and content.

High carbon content, high sulfur content, high phosphorus content, etc. will reduce weldability. Carbon steel with a carbon content of less than 0.25% has good weldability.

1. Cold working and strengthening treatment

2. Timeliness

Carbon is the most important element that determines the properties of steel

When the carbon content in steel is below 0.8%, as the carbon content increases, the strength and hardness of the steel increase, while the plasticity and toughness decrease;

However, when the carbon content is above 1.0%, the strength of the steel decreases as the carbon content increases.

As the carbon content increases, the welding performance of steel becomes worse, the cold brittleness and aging sensitivity increase, and the atmospheric corrosion resistance decreases.

Cold brittleness - refers to the phenomenon that the impact value of metal materials is significantly reduced at low temperatures.

Thermal brittleness - refers to the phenomenon that the impact value of certain steel materials at room temperature drops significantly after staying in the temperature range of 400 to 500°C for a long time.

Silicon is a beneficial element in steel. When its content is controlled to <1.0%, the strength of steel can be improved without significant impact on plasticity and toughness.

Manganese, as a beneficial element in steel, is the main alloying element in low-alloy structural steel in my country.

Manganese has strong deoxidation and desulfurization capabilities, which can eliminate or reduce the thermal brittleness caused by oxygen and sulfur, greatly improve the hot processing performance of steel, and at the same time increase the strength and hardness of steel.

Sulfur is a harmful element in steel.

The presence of sulfur will increase the thermal brittleness of steel, reduce various mechanical properties of steel, and also reduce the weldability, impact toughness, fatigue resistance and corrosion resistance of steel.

Phosphorus is a harmful element in steel.

As the phosphorus content increases, the strength, yield-to-strength ratio, and hardness of steel increase, while the plasticity and toughness decrease significantly. Significantly increases the cold brittleness of steel.

Phosphorus also significantly reduces the weldability of steel.

But phosphorus can improve the wear resistance and corrosion resistance of steel.

Oxygen is a harmful element in steel.

As the oxygen content increases, the strength of steel increases, but the plasticity, especially toughness, decreases significantly, and the weldability becomes worse.

The presence of oxygen can cause thermal brittleness of steel.

As the nitrogen content increases, the strength of the steel can be increased, the plasticity, especially the toughness, is significantly reduced, the weldability becomes worse, and the cold brittleness intensifies.

Titanium can significantly increase strength, improve toughness and weldability, but slightly reduce plasticity.

Adding it to steel can weaken the adverse effects of carbon and nitrogen and effectively increase the strength, but it will also increase the tendency of welding to be brittle and hard.

Steel structure refers to a structure made of steel plates, steel sections, steel pipes, steel ropes, steel beams and other steel materials, connected by welding, riveting, bolts, etc.

cold rolled

hot rolled

1. The brand indicates the composition

Trademark

P178 Application

definition

Classification

Brand indication:

1. Brand indication

2. Trademark

3.Application

Divided according to "average carbon content per 10,000"

Divided according to "yield strength"

Divided according to "tensile strength"

① Ordinary carbon structural steel: It consists of four parts: "letter representing yield point, yield point value, quality grade symbol, deoxidation method symbol".

② High-quality carbon structural steel: Expressed in ten thousandths of the C content (high-quality carbon structural steel with higher manganese content should have the Mn element marked; boiling steel, semi-killed steel and high-quality carbon structural steel for special purposes should have It is specially marked at the end of the steel number; adding "A" after the grade means high-grade high-quality steel, and adding "E" means special-grade high-quality steel)

③Hot-rolled steel bars: represented by HRB and the specified minimum yield strength (Note: Class I steel bars are plain round steel bars, represented by HPB).

④Cold rolled steel bars: represented by CRB and minimum tensile strength.

① Cold-rolled steel bars are all ribbed steel bars (i.e. rebar). ② Among hot-rolled steel bars, HPB300 steel bars are plain round steel bars; The No. 4 steel bar (i.e. HRB400), No. 5 steel bar (i.e. HRB500), No. 6 steel bar (i.e. HRB600) is ribbed steel bar (i.e. rebar).

Steel bars are generally delivered in straight bars, and steel bars with a diameter less than (12mm) can also be delivered in wire rods.

Hot rolled plain round steel bar Hot rolled plain bars

Hot rolled ribbed steel bars (Hot rolled Ribbed Bars)

Hot-rolled disc bars are steel bars with transverse ribs evenly distributed along the length direction on their surface after cold rolling.

Brands and applications:

Nominal diameter:

It is a steel bar made of hot-rolled ribbed steel bars that have been quenched and tempered. Smaller diameter (available in three specifications: 6, 8.2, and 10mm).

Steel wire for prestressed concrete: It is a high-strength steel wire made of high-quality carbon steel or other steel types with corresponding properties, and is made by cold processing and aging treatment.

Steel strand for prestressed concrete: It is made of 2, 3 or 7 high-strength steel wires with a diameter of 2.5~5.0mm. After twisting, it undergoes a certain heat treatment to remove the internal stress.

Petroleum asphalt is a colloidal structure.

Dispersed phase (colloidal particles): asphaltenes adsorbing part of the resin; Dispersion medium: oil with dissolved resin.

According to the different chemical composition and relative content of each component in asphalt, it can be divided into: sol type structure, gel structure, and sol-gel structure.

In the construction of asphalt concrete pavement on a certain highway, asphalt with () structure should be used.

viscosity

Plasticity

temperature sensitivity

atmospheric stability

construction safety

Summarize

Technical indicators of petroleum asphalt

Selection of petroleum asphalt

Blending of asphalt

Divided by mineral gradation type

Divided according to the density of the mixture

Divided according to the nominal maximum particle size (DM) of aggregates

Divided according to the construction temperature of the mixture

Asphalt concrete refers to a mixture of asphalt and mineral materials that is cooled and solidified after mixing. Asphalt concrete has good impermeability, good flexibility and self-healing closing functions. It is very suitable as a hydraulic anti-seepage body (anti-seepage core wall, anti-seepage panel, etc.) that needs to withstand uneven deformation. Hydraulic asphalt concrete refers to the general term for asphalt concrete used in water conservancy and hydropower projects.

Asphalt mortar: It is an asphalt mixture made of asphalt materials, mineral fillers and sand.

Hot asphalt mortar: It is made by first preparing asphalt materials and mineral powder into asphalt cement, and then adding sand at 140~160℃ and mixing well. The temperature during use is 160~180℃ to facilitate dense pouring.

Cold asphalt mortar: It is prepared with liquid asphalt or emulsified asphalt. The mineral materials do not need to be heated and dried, and have the advantages of safe and convenient construction.

Asphalt glue: It is a colloidal material prepared by mixing an appropriate amount of mineral powder or part of fibrous filler into asphalt. Commonly used mineral fillers mainly include talc powder, limestone powder and asbestos.

Asphalt glue is mainly used for pasting membranes, caulking, joints, leak repair, making the bottom layer of waterproof layer and the sealing layer of hydraulic asphalt concrete anti-seepage panel, etc.

Asphalt glue is used as the sealing layer of hydraulic asphalt concrete anti-seepage structure, which can increase surface density, delay aging and increase anti-seepage performance.

Rubber modified asphalt

Resin modified asphalt

Thermoplastic rubber modified asphalt

Mineral filler modified asphalt

SBS modified asphalt waterproofing membrane ((used in cold areas)

APP modified asphalt waterproofing membrane (used in hot areas)

PVC modified tar asphalt waterproof material

Reclaimed rubber modified asphalt waterproofing membrane

①High temperature sensitivity

②Poor atmospheric stability

③Poor plasticity

④Good adhesion to mineral aggregate surface

⑤ Toxic, smelly, strong antiseptic ability

·Asphalt is an organic cementitious material, which is a mixture of complex polymer hydrocarbons and non-metallic (oxygen, sulfur, nitrogen, etc.) derivatives. It is in solid, semi-solid or liquid state at room temperature.

·Asphalt has a dense structure, good plasticity and adhesion, and has properties such as non-conductivity, non-water absorption, impermeability, and resistance to acid and alkali corrosion.

·Asphalt is insoluble in water, but soluble in a variety of organic solutions.

·Mainly used for roofing, underground and underwater waterproofing projects, anti-corrosion projects, paving roads and airport runways, etc.

ground asphalt

tar pitch