Concrete piling? The following Zhongda Consulting brings a technical introduction to concrete piling. The relevant content is for reference.

(1) Main technical content

Concrete cracks have become a common quality problem in concrete projects. How to prevent and control concrete cracks is a technical problem that engineering and technical personnel are eager to solve. However, preventing and controlling concrete cracks is a systematic project, including every technical link in design, materials, and construction. This technology mainly describes some key technologies for preventing and controlling cracks, and improves the crack resistance of concrete, thereby achieving the purpose of preventing and controlling concrete cracks. The main contents of this technology include: design structural measures, selection of concrete raw materials (cement, admixtures, fine aggregates, coarse aggregates), factors affecting the anti-crack performance of concrete mix proportions, anti-crack concrete mix proportion design and crack resistance Concrete mix ratio optimization design methods and some technical measures in construction, etc.

(2) Technical indicators

This technology provides corresponding test methods and evaluation indicators for how to evaluate thick concrete materials and concrete crack resistance, making it operable.

(3) Scope of application

This technology is suitable for the design of concrete structures with higher crack resistance requirements, the selection of raw materials, the design and construction of crack-resistant concrete mix ratios, and the Evaluation of the crack resistance of concrete.

(4) Typical projects that have been applied

It has been applied in pilot projects and achieved good results. And give specific project examples.

Self-compacting technology

(1) Main technical content

Under the action of its own weight, concrete can fill the entire mold cavity without taking any compacting forming measures. Homogeneous concrete that leaves no voids is called self-compacting concrete. The main technical content provided by this technology: technical requirements for concrete raw materials, self-compacting concrete design points, namely fluidity, filling, segregation resistance and plasticity retention, and self-compacting concrete mix proportion design, etc.

(2) Test methods and evaluation indicators

This technology provides corresponding test methods and evaluation indicators, and provides how to control the performance of self-compacting concrete mixtures at the construction site specific provisions.

(3) Scope of use

Suitable for pouring concrete that is difficult to vibrate mechanically. Since self-compacting concrete contains a large amount of fine powder, more attention should be paid to the crack resistance of concrete. When anti-cracking measures are taken, self-compacting concrete has relatively poor crack resistance. It is not suitable for pouring continuous walls and large-area floor slabs.

(4) Engineering application examples

This technology gives an example of the application of self-compacting concrete in steel tube concrete in Shenzhen SEG Plaza. From the selection of concrete raw materials, concrete mix design, concrete mixture verification test, on-site simulation test to on-site construction, the entire process of self-compacting concrete technology is described, and the "Self-compacting Concrete Quality Standard" and "Production Technology" are formulated. Regulations" and "Construction Technical Regulations" to ensure the construction quality of self-compacting concrete.

Durability technology

(1) Main technical content

In the past concrete mix design, the main consideration was the strength index, while durability was considered less. High-performance concrete is characterized by high workability, high strength, and high durability, which is different from ordinary concrete. For marine projects, highway and bridge projects sprayed with deicing salt, and projects in saline areas, the intrusion of chlorine salt into concrete causes corrosion of steel bars, causing concrete expansion and cracking, which seriously affects the service life of buildings. The most important technical measure to improve its durability is to use high-performance concrete with high resistance to chloride ion permeability, which fundamentally improves the reinforcement performance of the concrete itself. Using conventional materials and conventional processes, high-performance concrete with strong resistance to chloride ion penetration and freeze-thaw resistance can be prepared at room temperature. The key to preparation is to select a high-efficiency water-reducing agent that matches the cement. Under the condition that the water-cement ratio is not greater than 0.35, use mineral admixtures such as fly ash, ground slag powder, and silica powder to replace part of the cement as the cementitious material. . These finely ground mineral admixtures exert a filling effect and pozzolanic reaction in the mixed concrete, making the concrete denser and thereby reducing the permeability of the concrete. Reducing the water consumption of concrete mixes and using a low water-cement ratio are key to improving the durability of concrete.

(2) Technical indicators

The inspection of the durability of high-performance concrete resistant to chlorine salt pollution should comply with the relevant provisions of the current water transportation industry standard "Concrete Quality Control Standard for Water Transportation Engineering" JTJ269, and The electric flux characterizing its chloride ion permeability should not be greater than 1000 coulombs. my country's industry standard "Technical Specifications for Anti-corrosion of Concrete Structures in Harbor Engineering" JTJ27 5-2000 proposes the following technical indicators for high-performance concrete required for concrete structures in harbor engineering:

Concrete mixture hardened concrete

Water-cement ratio Total amount of gelling matter (kg/m3) Slump (mm) Strength grade Resistance to chloride ion permeability (C)

≤0.35 ≥400≥120≥C45≤1OOO

Corresponding technical requirements are also put forward for concrete raw materials. The water reducing rate of water reducing agent is not less than 20%. The admixtures should be ground blast furnace slag with a fineness of not less than 4000 cm2/g, grade I and II fly ash and silicon powder. The fineness modulus of fine aggregate is between 2.6-3.2. The maximum particle size of coarse aggregate should not be larger than 25mm. When designing the mix ratio, the water-binder ratio should be reduced and the amount of admixture should be adjusted to ensure that the chloride ion permeability resistance index reaches the specified requirements. Concrete mixing should use a forced mixer, and the mixing time should be more than 4Os longer than conventional concrete. After concrete plastering, it should be covered immediately. After final setting, the top surface of the concrete should immediately begin continuous moisture curing for at least 15 days at normal temperature.

(3) Scope of application

Applicable to marine engineering, road and bridge engineering where deicing salt is spread in winter, salty areas and shore buildings close to the ocean, etc. that are exposed to chlorine Construction of buildings in a salt-polluted environment.

(4) Typical projects that have been applied

This technology is cost-effective, the raw materials are easy to obtain, and the preparation process is simple. Therefore, in recent years, it has been applied in various ports and cross-sea bridge projects in the north and south. Such as Shanghai Yangshan Deep Water Port Project, East China Sea Bridge, Hangzhou Bay Bridge, Yantian Port Container Terminal, Pakistan-aided Gwadar Terminal Project, etc.

The unit price increase of using high-performance concrete that is resistant to chlorine salt pollution is quite limited compared with ordinary concrete. However, compared with the effect of doubling the durability and lifespan, it greatly reduces the service cycle cost of the building and the economic benefits. The social benefits are very significant and the application prospects are very broad.

Fair-faced concrete technology

Fair-faced concrete means that after the structural concrete hardens, no decoration is added to the surface, and the natural color of the concrete is used directly as the exterior facing of the building. Using fair-faced concrete as a decorative surface has high requirements for appearance, color difference, surface bubbles, etc. Therefore, corresponding measures should be taken in concrete preparation, production, construction, maintenance, etc.

(1) Main technical content

①Concrete preparation

Concrete should use the same raw material and the same mix ratio, and the concrete mixture should have good Workability, no segregation, no bleeding.

Mineral admixtures are indispensable components of concrete. While considering the activity of the admixtures, we make full use of the different particle sizes of various admixtures to form a tight filling inside the concrete and enhance the strength of the concrete. Regarding density, in terms of admixtures, further attention should be paid to solving the adaptability of admixtures and cement, reducing the bleeding rate of concrete, and reducing the loss of concrete slump over time.

In addition to the different water-cement ratios that will lead to changes in the color of the hardened concrete, the impact of aggregates on the appearance cannot be ignored. Therefore, concrete projects with the same visual surface should use the same type of aggregates.

②Concrete formwork

In order to make the surface of fair-faced concrete smooth and bubble-free, formwork materials of different materials should be selected according to different strength levels of concrete. In addition to the release agent, The appearance of the concrete should not be affected.

③Concrete construction

When pouring concrete, the distance between the concrete feed opening and the pouring surface cannot be too large, otherwise the concrete will easily segregate. It is appropriate to allow the slurry to come out on the surface of the concrete during vibration. , and at the same time, leakage vibration and over-vibration should be avoided.

④Concrete maintenance

Concrete maintenance should ensure that the concrete surface is not polluted. Adequate and reasonable maintenance is the key to ensuring the surface and intrinsic quality of concrete after hardening.

(2) Technical indicators

①The concrete surface has no cracks, no obvious bubbles, no obvious color difference, and no obvious honeycomb pitting.

②The concrete surface is flat and smooth, and the axis and body dimensions are accurate.

③ Large cross-section and variable cross-section structure have regular lines and sharp edges and corners.

④The beam-column joints are smooth and have no clear marks.

(3) Scope of use

Fair-faced concrete adds a unique decorative effect to the building with its simple, steady, natural and pure texture. Generally used in municipal, transportation, water conservancy, aviation and other projects, it is also gradually used in residential buildings.

(4) Typical projects that have been applied

①Fair-faced concrete of the main towers of Yangpu and Nanpu Bridge

②Fair-faced concrete of the inclined cylinder of Shanghai Radio and Television Tower

③Fair-faced concrete for the pier part of the maglev train project

④Oriental Pearl TV Tower

⑤Pudong International Airport and the new terminal of Capital International Airport, etc.

Ultra-high pumping technology

Ultra-high pumping concrete technology generally refers to modern concrete pumping technology with a pumping height exceeding 200m.

Since the reform and opening up, there have been more than 1,000 high-rise and super high-rise buildings. Ultra-high pump concrete technology has become an indispensable aspect of super-high-rise building construction technology and has become a development trend favored by engineering projects in various countries. world's attention.

(1) Main technical content

①Quality of raw materials

The raw materials for preparing ultra-high pumping concrete are very different from ordinary pumped concrete. As the most basic cementing material - cement, in addition to the dosage, the rheology of cement should also be fully considered, that is, the compatibility of cement and high-performance water reducing agent. Only with good compatibility between the two can we obtain low water consumption and large amounts of water. It has excellent fluidity and low slump loss over time. In addition to the quality of fine aggregates that should comply with the "Quality Standards and Inspection Methods for Sand for Ordinary Concrete" (JGJ52), medium sand with different fineness modulus should be used for concrete of different strength levels. As an important component of high-performance high-pumping concrete, admixtures need to be carefully selected from various aspects such as activity, particle composition, water-reducing effect, heat of hydration, and pumping performance. As admixtures, single-component admixtures can no longer play their role well, and admixtures solely for the purpose of reducing water cannot achieve the purpose of using ultra-high pumping concrete. Multi-component compounding of admixtures, as well as specific The engineering preparation of admixtures with specific requirements has become an important aspect for admixture manufacturers to strengthen on-site services.

②Concrete preparation

The preparation of ultra-high pumping concrete must also study the relationship between the integrity, fluidity and pumpability of fresh concrete. Direct measures of concrete pumpability are to be studied.

③Pumping equipment

Pumping concrete is inseparable from concrete delivery pumps. Therefore, pumping equipment with high pressure, large displacement, wear resistance and strong adaptability is also a must. Less. In addition, the design of pumping pipelines, how to reduce resistance and shorten the route is also an aspect of pumping technology research.

(2) Technical indicators

①Concrete pumping height>200m.

②The performance of hardened concrete meets the design requirements.

③Concrete expansion degree>600mm, inverted cone method concrete falling time (3) Scope of application

Ultra-high pumping concrete is suitable for various super high-rise buildings with a pumping height greater than 200m .

(4) Typical projects that have been applied

①Jin Mao Building. The pumping height is 382.5m, and 174m3 is pumped at one time.

② Plaza 66. The pumping height is 288m, and the standard floor of the main building has more than 1,000 m3 of concrete per floor.

Pavement construction technology

(1) Main technical content

①In terms of mix design: using asphalt concrete mix design and chart production computer-aided systems, Automatically calculate the mix ratio of mineral materials, generate and adjust grading curves; automatically draw the relationship between various Marshall test indicators and asphalt dosage, calculate the optimal asphalt dosage; provide sand screening record tables and screening curves. The calculation speed is more than 20 times higher than manual calculation.

②In terms of construction technology and construction technology:

The structure of each layer of surface layer A should be selected according to the performance and function required by the layer in use. The three layers of the road should be made of dense skeleton. structure, it is not advisable to choose a suspended structure.

The optimal discharging temperature, paving temperature, and compaction temperature of B mixture; the temperature loss rules of modified asphalt mixture during transportation, paving, and compaction; effectively prevent Measures for temperature loss during the paving and rolling process minimize the uneven compaction caused by temperature differences during the paving and rolling forming process; the appropriate combination and rolling control of the mixture rolling equipment.

C For modified asphalt SMA pavement, the traditional rolling process is changed and the compaction work is increased, so that the mixture is formed at high temperature, the compaction degree is high, and the stones are not crushed. The grease does not float, and the depth of the surface structure reaches the standard upper limit.

(2) Technical indicators

①Engineering quality control standards during the construction process of modified asphalt mixture

(3) Scope of application

Suitable for paving single-layer and double-layer structures of hot-mix modified asphalt pavement such as high-grade highways, factory and mine roads, and airport runways.

(4) Typical projects that have been applied

This technology has been used in the third contract of Xincang Pavement (SAC structural surface layer) of Shihuang Expressway in Hebei Province, and the AB-24 standard of Lianxu Expressway in Jiangsu Province , Fenguan Expressway OPQ23 standard, Fenguan Expressway OPQ21 standard, Xusu Expressway standard 21 (modified asphalt SMA structure), Zhejiang Kangtaiqu Expressway standard 8 (AK anti-slip structure), Shanxi Dayun Expressway standard 7, Fujian Ningde Expressway B1 standard (AC structure), Beijing-Zhuhai Expressway Hubei Second Contract (Superpave12.5 structure) and other projects have been successfully applied. From 2000 to the end of 2003, the cumulative number of modified asphalt pavements was 267.821km. These projects have all been completed and were all excellent projects when they were delivered. After being put into use, their performance has been recognized by the owners and society, and they have good social reputation.

The modified asphalt pavement construction technology was researched and developed by the First Highway Engineering Bureau of China Road and Bridge Corporation, and is a key technology development project funded by China Road and Bridge Corporation.

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