Crack Control Technology for Concrete of Super-Large Section Precast Immersed Tube

2014 ◽  
Vol 578-579 ◽  
pp. 1240-1246
Author(s):  
Jin Hui Li ◽  
Ke Xin Liu ◽  
Liu Qing Tu ◽  
Yun Pang Jiao
Keyword(s):  
Temperature Control ◽  
Raw Materials ◽  
Concrete Strength ◽  
Complex Structure ◽  
Cooling Water ◽  
Temperature Monitoring ◽  
Raw Material ◽  
Maximum Temperature ◽  
Large Section ◽  
Crack Control

As the complex structure, large size, hot climate, aggressive corrosive environment and high concrete strength grade for Super-large Section Precast Immersed Tube of Hong Kong-Zhuhai-Macao Bridge, crack control of concrete was difficult. On the basis of simulating analysis on thermal stress, temperature control design was carried out. Harmful crack could be effective controlled by series of treatment measures during construction period such as optimization of raw materials, preparation of low heat and shrinkage concrete, controlling concrete raw material temperature, mixing concrete with ice shavings and cooling water, setting up automatic maintenance system and automatic temperature monitoring system. From the monitoring results, the temperature monitoring results were consistent with the simulation data, and the maximum temperature and the temperature difference between concrete surface and internal concrete were met the requirement of temperature control standard. Moreover, the precast immersed tube didn’t appear harmful crack.

scholarly journals Problems of mineral raw material losses of quality and quantity management in developing of large-scale complex-structure deposits.

2018 ◽  
Vol 56 ◽  
pp. 04003
Author(s):  
Sergei Tkach
Keyword(s):  
Large Scale ◽  
Raw Materials ◽  
Complex Structure ◽  
Raw Material ◽  
Qualitative And Quantitative ◽  
Mineral Raw Material ◽  
Regulatory Documents ◽  
Geological Conditions ◽  
High Degree ◽  
Very High

The article deals with the problems of mineral raw material losses of quality and quantity management in developing of large-scale complex-structure and composition deposits of solid minerals. It is shown that a very high degree of mining and geological conditions variability in time and space for the development of mining units is typical for such deposits. This significantly complicates the qualitative and quantitative operating losses setting and accounting of mineral raw materials during its extraction in the framework of existing general and industry regulatory documents. Conceptual principles for face-by-face operational setting of losses and impoverishment of minerals for the conditions of bulk mining of complex-structure deposits with the formation of gross mining flow with economically feasible and specified level of quality (the content of commercial and harmful components) are stated. These principles generally do not contradict effective instructions main provisions and are made to minimize the total operating losses during the processing of several mine sections (faces).

scholarly journals Temperature Control Technology for Construction of Jinsha River Bridge

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Hui-Wu Jin ◽  
Guo-An Wang ◽  
Zhan-Ming Chen
Keyword(s):  
Temperature Control ◽  
Temperature Difference ◽  
Cooling Water ◽  
Good Health ◽  
Large Mass ◽  
Maximum Temperature ◽  
Mass Concrete ◽  
Jinsha River ◽  
Mixture Ratio ◽  
Concrete Temperature

The key problem of mass concrete temperature control is to effectively control the maximum temperature inside concrete, the temperature difference between inside and outside concrete, and the temperature difference between surface and environment. The size of the main tower cap of No. 3 Jinsha River Bridge is 37 m × 23.5 m × 5.5 m, and the cubic volume of concrete reaches 4782.3 m3, which is poured in two times. In order to ensure construction quality of mass concrete structure, prevent the large mass concrete temperature stress, through the numerical simulation of the temperature control and optimization scheme, by optimizing the mixture ratio design, reducing the temperature of concrete pouring into the mold, cooling water cycling, insulation keeping in good health and a series of measures to effectively achieve the control goal, and eliminating the temperature cracks. The measured data show that the maximum temperature inside concrete, the temperature difference between inside and outside, and the temperature difference between surface and environment are qualified, but the temperature difference control of cooling water inlet and outlet has hysteresis effect, and the temperature difference between inlet and outlet will be greater than 10°C, which should be noticed.

scholarly journals Bamboo kraft pulping

2019 ◽  
Vol 6 (4) ◽  
pp. 791 ◽  
Author(s):  
Eraldo Antonio Bonfatti Júnior ◽  
Elaine Cristina Lengowski ◽  
Alan Sulato de Andrade ◽  
Ivan Venson ◽  
Umberto Klock ◽  
...  
Keyword(s):  
Raw Materials ◽  
Basic Density ◽  
Heating Time ◽  
Kraft Pulping ◽  
Raw Material ◽  
Maximum Temperature ◽  
Extractive Content ◽  
Technological Characteristics ◽  
Bambusa Vulgaris ◽  
Pinus Spp

Despite of the wide use worldwide, the industrial potential of bamboo species in Brazil is not much investigated. However, some encouragement to revert this situation was created in last few years. The aim of this research was to evaluate the technological characteristics of the Bambusa vulgaris biomass for the production of pulp by the kraft process. The technological characteristics of the raw material were determined by the basic density, the chemical composition and the morphology of the fibers. The cooking process was carried out with the application of eight charges of active alkali, in 90 minutes of heating time and 60 minutes in the maximum temperature of 170ºC. All analyzes were also executed with the Eucalyptus spp. and the Pinus spp., in order to make a complete comparison among the species Bambusa vulgaris and the two most used raw materials for the pulp production in Brazil. The Bambusa vulgaris presented a higher basic density, lower holocellulose content and a higher total extractive content. Its fibers have intermediate length and wall thickness, similar to the Eucalyptus spp. and the Pinus spp. Considering the kraft pulping process, the species Bambusa vulgaris demonstrated to be easier to delignify besides presenting almost zero reject content and smaller consumption of active alkali. However, the Eucalyptus spp. and the Pinus spp. obtained the best yields, the lowest specific consumption of raw material and better selectivities.

scholarly journals Application of hydration heat inhibitor in crack control of mass concrete of tunnel side wall

2021 ◽  
Vol 283 ◽  
pp. 01032
Author(s):  
XiZhi Wang ◽  
MinSheng Shi ◽  
XinGang Wang
Keyword(s):  
Temperature Rise ◽  
Concrete Strength ◽  
Side Wall ◽  
Hydration Heat ◽  
Structural Deformation ◽  
Maximum Temperature ◽  
Optimal Dosage ◽  
Mass Concrete ◽  
Control Effect ◽  
Crack Control

The structural deformation caused by temperature change is the main reason for cracking of mass concrete. In order to avoid or reduce the crack of the side wall of cast-in-place mass concrete in tunnel, the effects of different dosage of hydration heat inhibitor on the internal temperature rise curve of concrete, strength and the properties of the mixture are analyzed through experimental research, and the optimal dosage of 1% of cementing material is finally determined. The engineering application results show that after adding hydration heat inhibitor to the tunnel side wall concrete, the maximum temperature rise in the tunnel side wall is obviously reduced, and the arrival time of the temperature peak is delayed. No cracks appear in the tunnel side wall, and the crack control effect is good.

scholarly journals Use of Ceramic Powder in Concrete - Strength & Durability Properties

2017 ◽  
Author(s):  
Kiran Kumar Poloju ◽  
Abdullah Tahir
Keyword(s):  
Compressive Strength ◽  
Ceramic Industry ◽  
Raw Materials ◽  
Concrete Strength ◽  
Ceramic Powder ◽  
Raw Material ◽  
Experimental Investigations ◽  
Ceramic Tiles ◽  
Ceramic Waste ◽  
The Cost

Ceramic wall tiles are used as building material in the field of construction. Manufacturing of ceramic tiles require different raw material like clay, potash, dolomite, feldspar, talc and different chemicals like sodium silicate, sodium tripoly, phosphate (STPP) in ceramic production. In the ceramic industry, about 15%-30% production goes as waste. These wastes poses a serious threat to the environment by polluting the habitant and agricultural lands. Therefore using of ceramic waste powder in concrete would benefit in many ways in saving energy & protecting the environment. The cost of deposition of ceramic waste in landfills will be saved. Raw materials and natural resources will be replaced. Which indirectly helps for reducing the greenhouse gas (co2).There is a large amount of carbon dioxide released in the cement production. In this research study the (OPC) cement has been replaced by ceramic waste powder accordingly in the range of 0%, 10%, 20%, 30% 40%, & 50% by weight for M-25 grade concrete. The wastes employed came from ceramic industry which is in Rusayl (Muscat, Oman) industrial area. Based on experimental investigations concerning the compressive strength of concrete, the following observations are made: (a)    The Compressive Strength of M25 grade concrete increases when the replacement of cement with ceramic waste up to 30% by weight of cement and further replacement of cement with ceramic powder decreases the compressive strength.   (b)  Concrete on 30% replacement of cement with ceramic waste, compressive strength obtained is 26.77 N/mm2and vice-versa the cost of the concrete is reduced up to 13.27% in M25 grade and hence it becomes more economical without compromising concrete strength than the standard concrete. It becomes technically and economically feasible and viable. It is the possible alternative solution of safe disposal of ceramic waste. Reuse of this kind of waste has advantages economic and environmental, reduction in the number of natural spaces employed as refuse dumps. Indirectly, all the above contributes to a better quality of life for citizens and to introduce the concept of sustainability in the construction sector.

scholarly journals PENGARUH PENAMBAHAN ABU JERAMI PADI TERHADAP KUAT TEKAN BETON

Jurnal CIVILA ◽  
2017 ◽  
Vol 2 (2) ◽  
pp. 9
Author(s):  
Adytia Eko Sutrisno ◽  
Dwi Kartikasari
Keyword(s):  
Compressive Strength ◽  
Rice Straw ◽  
Raw Materials ◽  
Concrete Strength ◽  
Raw Material ◽  
Silica Sand ◽  
Alternative Materials ◽  
Continuous Mining ◽  
O 15 ◽  
Straw Ash

Cement is one of the main ingredients in the manufacture of concrete. The raw material is used in the manufacture of cement are limestone, silica sand, clay and iron sand. Cement is a material made of material that belong to natural resources that cannot be renewed, so that the raw material inventory of cement in nature is getting less. Continuous mining of cement raw materials has an impact on natural damage. It encourages the discovery of alternative materials as an additive to the manufacture of concrete. The method of data analysis begins with the investigation of cement material, coarse aggregate, fine aggregats and rice straw ash. Concrete is added with rice straw ash with variations of 0%, 5%, 10%, and 15% additions. The test specimen are cylinders with size ø 15 cm x 30 cm and the planned compressive strength is 14.5 MPa. After going through the treatment period for 7 days, the value of compressive strength is then correlated to the age of 28 days. Based on research that has been done at Civil Engineering Laboratory of Islamic University of Lamongan, it is found that there is a decrease of strength on each addition of ash straw content of paddy. Use of rice straw ash in concrete mix with variation of 0%, 5%, 10%, and 15% addition of The weight of cement has an impact on the decrease of concrete strength value. The compressive strength values obtained at the age of 28 days are 18,440 Mpa, 15,366 Mpa, 13,948 Mpa, and 12,530 Mpa.

Theoretical Substantiation of the Foam Concrete Strength Formation Laws

2020 ◽  
Vol 1011 ◽  
pp. 92-96
Author(s):  
Lyubov Morgun ◽  
Vladimir Morgun ◽  
Alla Bogatina ◽  
Aleksei Revyakin
Keyword(s):  
Mass Transfer ◽  
Raw Materials ◽  
Concrete Strength ◽  
Mass Transfer Rate ◽  
Raw Material ◽  
Aggregative Stability ◽  
Hardened Concrete ◽  
Foam Concrete ◽  
Dispersion Parameters ◽  
Concrete Mixtures

A detailed theoretical analysis of the processes occurring in foam concrete mixtures in the period between their laying in the mold and the phase transition “from viscous to solid” completion moment. The stages of the formation of inter-pore septa in foam concrete mixtures, depending on the material nature and shape of the solid dispersed particles of raw materials, are sequentially considered. It is shown that their shape affects the mass transfer rate and the density of inter-pore septa during the structure formation. The reasons for the fluctuations in the elasticity of foam films during the predominance period of viscous bonds between the components of the raw material are described. The gas inclusions factors of influence on the dispersion parameters and, as a consequence, the aggregative stability of foam mixtures, are ranked. The positive dispersed reinforcement effect on the mass transfer processes in mixtures and the hardened concrete strength is substantiated.

scholarly journals Actual Temperature Evolution of Thick Raft Concrete Foundations and Cracking Risk Analysis

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Yuwen Ju ◽  
Honggang Lei
Keyword(s):  
Temperature Gradient ◽  
Temperature Control ◽  
Temperature Difference ◽  
Temperature Monitoring ◽  
Temperature Evolution ◽  
Maximum Temperature ◽  
Engineering Project ◽  
Maximum Temperature Difference ◽  
Concrete Core

Heat of the hydration-induced temperature evolution of a 3.30 m thick raft concrete foundation for wind turbines at the early ages was monitored in situ through a temperature sensor testing system. The temperature variation patterns and risk of cracking were studied. Finite element analysis (FEA) conducted on the temperature fields determined the lower thickness threshold requiring temperature control. A comprehensive temperature control approach suitable for thick raft foundations was proposed based on a practical engineering project. Temperature monitoring and analysis results showed that the early temperature field evolution featured two characteristic phases: heat accumulation and heat release. A remarkable temperature gradient was observed along the vertical direction of the foundation. The maximum temperature difference between the concrete core and the top surface was approximately 35°C, indicating a risk of cracking. The accuracy of the FEA was ensured by adopting the concrete heat generation rate obtained from the adiabatic temperature rise test. A further FEA performed on foundations with various thicknesses demonstrated that a thicker foundation corresponded to a higher vertical temperature gradient. Moreover, a raft thickness larger than 2.50 m corresponded to a maximum temperature difference between the concrete core and the surface higher than 25°C, above which cracking prevention measures should be taken. Field test results proved the applicability of a suite of temperature feedback regulation measures proposed herein, including layered pouring, thermal insulation, and in situ real-time temperature monitoring, to thick raft mass concrete structures with relatively small volumes. Good control of temperature difference was achieved using this approach.

scholarly journals Evaluation of Synthesized Catalytic Complex Structure-Forming Ability during Paraffin Base Tar Upgrade

2018 ◽  
Vol 7 (4.36) ◽  
pp. 1006
Author(s):  
Alim F. Kemalov ◽  
Ruslan A. Kemalov ◽  
Adiko Serge-Bertrand
Keyword(s):  
Chemical Nature ◽  
Raw Materials ◽  
Complex Structure ◽  
Strength Properties ◽  
Raw Material ◽  
Low Molecular Weight ◽  
Catalytic Complex ◽  
Bituminous Materials ◽  
Heavy Oil Residues ◽  
Selection Of

The combination of the synthesized multicomponent bifunctional catalytic complex (MBC) components with heavy oil residues (HOR) of the paraffin-naphthenic (P-N) base leads to the chemical structuring of the hydrocarbon (HC) segments of the raw material molecules, and the specifics of HOR physicochemical structure, which will be the criteria for the selection of modifiers with a certain chemical nature [1,2,3,4]. It has been established that the introduction of catalytic activators in the tar composition promotes both the intensification of the oxidation process and the production of bituminous insulating material (BIM) with high physicomechanical properties [1,2,4].Raw materials for the production of special bituminous materials must be highly resinous with a P-HC content of up to 3% by weight. Based on the works by A.S. Kolbanovskaya [6], this is explained by the fact that the dispersed structure of bitumen is significantly dependent on the content of P-HC, since the dispersed phase in the oils is formed by naphthenic (N-) and PN-A-HC at certain temperatures with the side chains of the paraffinic P-HC series. If their content is more than 3% by weight the crystallization skeleton of P-HC is developed, which provides stiffness and reduces the plasticity interval for the system. Together with this, it is known that in the process of HOR oxidation the amount of low-molecular-weight oil A-HC decreases continuously, and the relative amount of PN-HC increases. Due to this, the affinity of the dispersion medium (DM) decreases to asphaltenes [7,8,9], which, moreover, becomes larger, which leads to THE deterioration of the cohesion and adhesion-strength properties of BIM.  

Measures to Control the Temperature of the Concrete Cracks in Foundation Mass

2015 ◽  
Vol 723 ◽  
pp. 309-312
Author(s):  
Zi Chun Mao ◽  
Dong Wang ◽  
Yuan Bo Liu
Keyword(s):  
Temperature Stress ◽  
Material Selection ◽  
Raw Materials ◽  
Concrete Strength ◽  
Control Measures ◽  
Raw Material ◽  
Stress Generation ◽  
Grade Configuration ◽  
Exploratory Research ◽  
Raw Material Selection

In the construction process, the concrete has been get fully utilized, there have been a variety of concrete strength grade configuration requirements and the corresponding raw materials. In the pouring process large volume concrete base, since the temperature stress generation will produce concrete temperature cracks, so the concrete pouring, raw material selection, after pouring temperature control measures have higher requirements. Based on a practical project, the construction of the control temperature stress did some exploratory research.

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