Concrete mix ratio, how is it calculated. How much do you use for various aggregates?

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1. Design and calculation of mix ratio.

According to JGT55-2000 and domestic bidding documents for highway engineering.

The second volume of the 2003 edition of the template, combined with the actual situation of the construction site, the design and calculation of C30 ordinary concrete, the specific process is as follows:

1. Calculate the strength of the trial

MPa2, calculate the water-cement ratio.

w/c=aa×fce/?。

3. Select the water consumption per cubic meter of concrete: mwo = 180kg m3 when mixed with admixtures:

4. Calculate the amount of concrete cement per cubic meter: mco=mwo (w c)=?kg m35, select sand rate:

6. Calculate the amount of coarse and fine aggregate per cubic meter of concrete (MCP value is 2420kg m3): MCO+MGO+MSO+MWO=MCP

s=mso/(mgo+mso)×100%

mso=?kg/m3

mgo=?kg/m3

mco:mgo:mso:mwo=?

The methods and steps of ordinary concrete mix design should comply with the industry standard JGJ issued by the Ministry of Construction

Design procedures for general concrete mixture. The standard specifies that there should be three steps in the design of the mix ratio.

design calculation of mix ratio; 2)

Trialing; 3) Adjustment and determination of the mix ratio. The standard gives a number of technical parameters for national unity, such as the calculation formula of concrete trial strength, the selection table of concrete water consumption, the selection table of concrete sand rate, etc. In addition, the mix design must also master GB

Code for construction and acceptance of concrete structure engineering and GB

j107287

Concrete strength inspection and evaluation standards.

Preparation and inspection of raw materials Concrete consists of four materials: cement, sand, gravel and water. A fifth material (admixtures and admixtures) has now been added

These materials have quality inspection standards, and the properties of the materials can be known by testing and comparing the standards.

Cement: Before the use of cement, in addition to holding the manufacturer's certificate, it should also be used for routine inspections such as strength, setting time, and safety.

Sand and gravel is coarse and fine aggregate, which mainly tests the mud content, particle gradation and other indicators.

Water: Drinking water should be used for mixing concrete, and when other water sources are used, the water quality should be in line with JGJ

Specification of water standard for concrete mixing.

Admixture: Due to the small amount of concrete admixture, it can significantly improve the performance of concrete, save cement and improve work efficiency, so it is more commonly used. With admixtures, care should be taken not only to comply with GB

According to the provisions of the J119 technical specification for the application of concrete admixtures, the special construction mix ratio of admixture concrete should also be determined by testing.

In order to adjust the strength grade of concrete, save cement, and improve the performance of concrete mixture, fly ash and other admixtures must be mixed into concrete, and its quality should be in line with GB

1596 provisions for fly ash in cement and concrete.

For example, the mix ratio of C15 concrete is 246 kg of cement, 767 kg of sand, 1199 kg of stone, and 175 kg of water, that is, 1 ratio.

When the concrete is put into the formwork, it is necessary to avoid pouring it into the formwork, otherwise it will impact and damage the formwork, especially when the pouring height exceeds two meters, it must be handled with professional materials. After the concrete is configured, it must be used up within 5 hours, so as to avoid cold joints during construction.

And the time difference between the two pourings.

It should not be more than half an hour, otherwise it will reduce the quality of the concrete.

Concrete precautions.

Concrete admixtures.

It can improve coagulation workability, increase strength, adjust setting time, and improve durability. According to the purpose of use, performance requirements, construction technology, climatic conditions, etc.: combined with the performance of concrete raw materials, mix ratio and adaptability to cement and other factors, the type and amount should be determined through experiments.

In addition to sand and gravel. The quality must meet the requirements of the quality standards for the sand and gravel used in each grade of concrete. Concrete strength.

Only under the normal range of temperature and humidity can the normal development be guaranteed, and the maintenance should be given in accordance with the provisions of the construction specifications, and the sun should be protected from dehydration in summer, and moisturizing and frost damage in winter.

The so-called concrete construction mix ratio refers to the proportional relationship between the components of the concrete.

Adjustment steps: set the laboratory mix ratio for cementitious material: cement:

Water: Sand: Stone = 1:

x:y:z, the moisture content of the sand on site is m, and the moisture content of the stone is n, then the construction mix ratio is adjusted as:

1：(x-y*m-z*n)：y*（1+m）：

z*（1+n）。

Concrete mix design is a very important work in concrete engineering, which directly affects the smooth construction of concrete, the quality of concrete engineering and the cost of concrete engineering.

1) Concrete mix design basis:

Code for Design of Ordinary Concrete Mix (JGJ 55 2011) "Code for Acceptance of Construction Quality of Concrete Structures" (GB 50204 2015) "Quality Control Standard for Concrete" (GB 50164 2011).

Test Method for Properties of Ordinary Concrete Mixture (GB T 50080 2002) "Test Method for Mechanical Properties of Ordinary Concrete" (GB T 50081 2002).

Concrete strength inspection and evaluation standards (GB T 50107 2010) and sand, stone, admixtures, admixtures related standards.

2) Principles of concrete mix design:

1. The workability of the concrete mixture can meet the needs of construction;

2. The strength of the concrete can meet the requirements of the design;

3. Concrete should have good durability;

4.In meeting the above requirements, minimize costs and increase benefits.

On December 28, 2000, the Ministry of Construction of the People's Republic of China approved the implementation of the industry standard "Design Regulations for Ordinary Concrete Mix" (JGJ 55 2000) on April 1, 2001. The original industry standard "Design Code for Ordinary Concrete Mix" (JGJ T 55-96) shall be repealed at the same time.

This realignment is mainly a revision of the original industry standard Huai Zhun "Design Code for Ordinary Concrete Mix Ratio" (JGJ T55-96).

1、fcu,0=fcu+

2, W C = AA * FCE (FCU, O + AA * AB * FCE) = 3, according to the construction requirements, the concrete design slump is 120mm 160mm, take the unit water consumption of 215kg, the addition of retarding high-efficiency superplasticizer, water reduction rate δ = 22%, then the concrete unit water consumption: MW0 = MW (1-δ) 215 * (1-22%) = 168kg

4. The amount of cement per unit is Changyou: MC=MW

2.Unit cement consumption.

mc=mwo/w/c=168/

Cement replaced with fly ash with a substitution coefficient of =, there is.

Cement dosage: mc1=mc*(

Fly ash dosage: mf1=mc*

Dosage of superplasticizer: MFDn1=(MC1+MF1)*Assuming that the unit bulk density of concrete MCP=2400kg m and the sand rate S=39%, there is:

Fine aggregate MS1 = 730kg, coarse aggregate MG1 = 1142kg.

3.Concrete Fit Pure Resistance Ratio Table:

Concrete memorial marking: water (kg m3), cement (kg m3), sand.

Batching ratio of concrete: The volume of the three-phase of the concrete mixture is roughly 73% 84% of the total volume, the liquid phase accounts for 15% 22%, and the gas phase accounts for 1% 5%.

The volume of the three phases is not static, in the process of condensation hardening after construction, the volume occupied by the three phases will continue to change, but the changes will decrease after the final condensation, which is manifested as the total volume and liquid phase are decreasing, while the gas phase is increasing, mainly caused by the loss of liquid phase, evaporation and absorption by the solid phase.

In addition, the volume of the three phases can also change with changing environmental conditions. The change of three-phase volume is one of the main reasons for the cracks in concrete, especially before the final setting of concrete (that is, it is generally considered that the cracks caused by shrinkage with accompaniment, drying shrinkage, etc.), but if effective maintenance measures are taken in time after pouring, the obvious control effect can be obtained.

Durability requirements are met

Concrete mixture.

The design should not only meet the structural design.

The durability requirements such as impermeability and frost resistance should also be considered, such as pavements and bridges in severe cold areas, structures in the range of water level rises and falls, and structures exposed to chlorine pollution.

In order to ensure that these concrete structures have good durability, it is not only necessary to optimize the concrete mix design, but also to optimize the raw materials used in the concrete before the concrete mix design, and the selection of good raw materials is the basic premise to ensure that the designed concrete has good durability.

The above content reference: Encyclopedia - concrete mix ratio.