Mass concrete sections and the maturity concept

1976 ◽  
Vol 3 (1) ◽  
pp. 47-57 ◽  
Author(s):  
E. G. Nisbet ◽  
S. T. Maitland
Keyword(s):  
Temperature Rise ◽  
Concrete Strength ◽  
Temperature Curve ◽  
Mass Concrete ◽  
Structural Elements ◽  
Standard Laboratory ◽  
Laboratory Conditions ◽  
Concrete Cylinders ◽  
Recording Potentiometer ◽  
Early Strength

The 28 day strength of concrete cylinders cured under standard laboratory conditions can now be reliably predicted at early ages by use of (a) the Modified Boiling Test or (b) the Autogenous Curing Test. The availability of early strength indicators for concrete can be used to great advantage during construction provided these strengths can be related to the strength of the structural elements.To permit an estimate to be made of the strength of in-place concrete on structures appurtenant to the Welland Channel By-pass, the temperature rise of the structural elements was monitored with an automatic 16 point recording potentiometer. The time temperature curve of the in-place concrete was compared to that of 6 in. by 12 in. (150 mm by 300 mm) concrete cylinders taken during casting of the structure and cured autogenously for 48 h, thus permitting an estimate of the in-place concrete strength to be made from the results of the 48 h autogenous strengths.On the basis of the in-place concrete strength estimates, decisions were made regarding the application of post tensioning forces and/or the removal of formwork and supporting shoring.

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.

Kinetic Model of Adiabatic Temperature Rise of Mass Concrete

2021 ◽  
Vol 13 (5) ◽  
pp. 771-780
Author(s):  
Shou-Kai Chen ◽  
Bo-Wen Xu
Keyword(s):  
Temperature Field ◽  
Temperature Rise ◽  
Initial Conditions ◽  
Dynamic Change ◽  
Adiabatic Temperature ◽  
Model Parameters ◽  
Hydration Reaction ◽  
Mass Concrete ◽  
Adiabatic Temperature Rise ◽  
Proposed Model

The adiabatic temperature rise model of mass concrete is very important for temperature field simulation, same to crack resistance capacity and temperature control of concrete structures. In this research, a thermal kinetics analysis was performed to study the exothermic hydration reaction process of concrete, and an adiabatic temperature rise model was proposed. The proposed model considers influencing factors, including initial temperature, temperature history, activation energy, and the completion degree of adiabatic temperature rise and is theoretically mature and definitive in physical meaning. It was performed on different initial temperatures for adiabatic temperature rise test; the data were employed in a regression analysis of the model parameters and initial conditions. The same function was applied to describe the dynamic change of the adiabatic temperature rise rates for different initial temperatures and different temperature changing processes and subsequently employed in a finite element analysis of the concrete temperature field. The test results indicated that the proposed model adequately fits the data of the adiabatic temperature rise test, which included different initial temperatures, and accurately predicts the changing pattern of adiabatic temperature rise of concrete at different initial temperatures. Compared with the results using the traditional age-based adiabatic temperature rise model, the results of a calculation example revealed that the simulated calculation results using the proposed model can accurately reflect the temperature change pattern of concrete in heat dissipation conditions.

scholarly journals Revisiting the Effect of Slag in Reducing Heat of Hydration in Concrete in Comparison to Other Supplementary Cementitious Materials

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1847 ◽  
Author(s):  
Hoon Moon ◽  
Sivakumar Ramanathan ◽  
Prannoy Suraneni ◽  
Chang-Seon Shon ◽  
Chang-Joon Lee ◽  
...  
Keyword(s):  
Blast Furnace ◽  
Temperature Rise ◽  
Adiabatic Calorimetry ◽  
Blast Furnace Slag ◽  
Isothermal Calorimetry ◽  
Heat Of Hydration ◽  
Supplementary Cementitious Materials ◽  
Maximum Temperature ◽  
Mass Concrete ◽  
Furnace Slag

Blast furnace slag (SL) is an amorphous calcium aluminosilicate material that exhibits both pozzolanic and latent hydraulic activities. It has been successfully used to reduce the heat of hydration in mass concrete. However, SL currently available in the market generally experiences pre-treatment to increase its reactivity to be closer to that of portland cement. Therefore, using such pre-treated SL may not be applicable for reducing the heat of hydration in mass concrete. In this work, the adiabatic and semi-adiabatic temperature rise of concretes with 20% and 40% SL (mass replacement of cement) containing calcium sulfate were investigated. Isothermal calorimetry and thermal analysis (TGA) were used to study the hydration kinetics of cement paste at 23 and 50 °C. Results were compared with those with control cement and 20% replacements of silica fume, fly ash, and metakaolin. Results obtained from adiabatic calorimetry and isothermal calorimetry testing showed that the concrete with SL had somewhat higher maximum temperature rise and heat release compared to other materials, regardless of SL replacement levels. However, there was a delay in time to reach maximum temperature with increasing SL replacement level. At 50 °C, a significant acceleration was observed for SL, which is more likely related to the pozzolanic reaction than the hydraulic reaction. Semi-adiabatic calorimetry did not show a greater temperature rise for the SL compared to other materials; the differences in results between semi-adiabatic and adiabatic calorimetry are important and should be noted. Based on these results, it is concluded that the use of blast furnace slag should be carefully considered if used for mass concrete applications.

Enantioselective Synthesis and Photoreactivity of a Diazirinyl-substituted (R)-β-Phenylalanine

2014 ◽  
Vol 69 (11-12) ◽  
pp. 1088-1096 ◽  
Author(s):  
Jan-Niklas Schäckermann ◽  
Thomas Lindel
Keyword(s):  
Amino Acid ◽  
Absolute Configuration ◽  
Enantioselective Synthesis ◽  
Thermally Stable ◽  
Standard Laboratory ◽  
Laboratory Conditions ◽  
Quantumchemical Calculations ◽  
Valence Tautomers ◽  
The Absolute

Abstract The first enantioselective synthesis of a photoreactive (R)-β-phenylalanine is described. In the key step, m-diazirinyl-substituted benzaldehyde is converted to a chiral sulfinimine in a Ti(OEt)4- mediated reaction, followed by diastereoselective enolate addition. The absolute configuration of photo (R)-β-phenylalanine was confirmed by Mosher analysis. The photo amino acid proved to be thermally stable under standard laboratory conditions. Irradiation in toluene afforded cycloheptatriene=norcaradiene valence tautomers, together with carbene benzylation. Quantumchemical calculations indicate a small triplet-singlet gap.

Research and Applying Evolution of High Efficient Water-Reducing Agent for High Performance Concrete

2012 ◽  
Vol 610-613 ◽  
pp. 573-576
Author(s):  
Zheng Jun Wang ◽  
Jia Bin Liang
Keyword(s):  
High Performance ◽  
Lightweight Concrete ◽  
High Performance Concrete ◽  
Concrete Strength ◽  
High Strength ◽  
Reducing Agent ◽  
Mass Concrete ◽  
Green Concrete ◽  
High Efficient ◽  
Strength And Durability

This paper discusses the development of water-reducing agent and the present situation of the application of high performance concrete. The traditional concrete will be substituted by high performance concrete, green concrete. In the course of appearance of high performance and green, concrete admixtures plays an extremely important role. Concrete water-reducing agent is admixture of the main part. In the case of keeping liquidity, it can make water consumption reduce, so the concrete strength and durability can be improved. It is applicable to all kinds of industrial and civil construction engineering, and it can be applied to different strength grade of concrete. It has important significance for mass concrete engineering, marine building facilities, and component and product of high strength lightweight concrete.

Large Ranging of Ultrasonic Testing Inspection Internal Defects of Mass Concrete Structure

2013 ◽  
Vol 357-360 ◽  
pp. 1492-1497
Author(s):  
Lin Liu ◽  
Wen Zhao
Keyword(s):  
Concrete Structure ◽  
Linear Trend ◽  
Ultrasonic Method ◽  
Concrete Strength ◽  
Ultrasonic Test ◽  
Test Method ◽  
Mass Concrete ◽  
Velocity Of Sound ◽  
Internal Defects ◽  
Test Distance

The ranging greater than 3m is not accorded with china engineering construction standardization association standard TECHNOLOGICAL SPECIFICATION FOR INSPECTION OF CONCRETE DEFECTS BY ULTRASONIC METHOD[CECS 21:200 (Transducer spacing is 2~3m). This paper studied large ranging of ultrasonic test mass concrete structure, and analyzed a project instance that was inspected the internal defects of mass concrete structures with various test methods, compared of those results. As detection is shown, first, with the test distance increased to 5.1m, the velocity of sound shows a linear trend of continuous development trend. Second, responds to improve of concrete strength, the velocity of sound increases, but not shows a linear trend. In addition, with the test distance increasing, concrete strength increases, but the velocity is down. A large ranging of ultrasonic test method was developed based on these observations.

Effect of Naphthalene Compounded Superplasticizer on Strength and Shrinkage of Ready-Mixed Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 488-495
Author(s):  
Yu Fei Wang ◽  
Han Dong Yan
Keyword(s):  
Cement Paste ◽  
Test Data ◽  
Concrete Strength ◽  
Reducing Agent ◽  
The Other ◽  
General Rules ◽  
Early Strength ◽  
Ready Mixed Concrete ◽  
Mixed Concrete

Superplasticizer is widespread applied in the ready-mixed concrete in China. In the specific engineering, it is not only has the requirement of water-reducing ratio for superplasticizer, but also the superplasticizer has to meet the demand such as early-strength, air-entraining, retarding and so on. In current, the naphthalene compounded superplasticizer is conducted on the basis of the FDN modification. This paper selects two kinds of representative naphthalene compounded superplasticizers, one is the setretarder superplasticizer (WRA1), and the other one is the early strength-air entraining-retarding superplasticizer (WRA2). The effect of performance on neat cement paste, mortar and concrete which mixed with the two admixtures are compared with the benchmarks (not mixed with water reducing agent) and mixed with FDN. Through the analysis and comparison of the test data, the general rules of the naphthalene compounded superplasticizer to concrete strength and shrinkage are put forward in this paper. Also, according to those rules, it poses the concrete problems to be noted in the production. This may have guidance for reducing the early cracks of ready-mixed concrete.

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