scholarly journals Kinetic Hydration Heat Modeling for High-Performance Concrete Containing Limestone Powder

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Xiao-Yong Wang
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Setting Time ◽  
Dilution Effect ◽  
Heat Of Hydration ◽  
Hydration Heat ◽  
Limestone Powder ◽  
Temperature History ◽  
Degree Of Hydration ◽  
Hydration Model

Limestone powder is increasingly used in producing high-performance concrete in the modern concrete industry. Limestone powder blended concrete has many advantages, such as increasing the early-age strength, reducing the setting time, improving the workability, and reducing the heat of hydration. This study presents a kinetic model for modeling the hydration heat of limestone blended concrete. First, an improved hydration model is proposed which considers the dilution effect and nucleation effect due to limestone powder addition. A degree of hydration is calculated using this improved hydration model. Second, hydration heat is calculated using the degree of hydration. The effects of water to binder ratio and limestone replacement ratio on hydration heat are clarified. Third, the temperature history and temperature distribution of hardening limestone blended concrete are calculated by combining hydration model with finite element method. The analysis results generally agree with experimental results of high-performance concrete with various mixing proportions.

A Constitutive Law of Salt Concrete Used for Closure of an LILW-Repository

2003 ◽  
Author(s):  
H. J. Engelhardt ◽  
M. Kreienmeyer ◽  
C. Lerch ◽  
N. Mu¨ller-Hoeppe ◽  
R. Ko¨ster ◽  
...  
Keyword(s):  
Setting Time ◽  
Heat Of Hydration ◽  
Constitutive Law ◽  
Numerical Code ◽  
Model Parameters ◽  
Mass Concrete ◽  
Degree Of Hydration ◽  
Equivalent Age ◽  
Setting Process ◽  
Hydration Model

The Repository of LILW Radioactive Waste Morsleben (ERAM) is located in the Federal State Saxony Anhalt, Germany. After an operational phase of about 20 years it is now under licensing for closure. As the repository was erected in a former salt mine, there exists a void volume of approx. 6 million m3. Consequently, a closure concept was developed serving three main functional requirements: stabilization, limitation of leaching processes and sealing. It relies on a comprehensive backfilling of the openings using two mixtures of salt concretes. The concretes will be used to backfill cavities as well as to construct seals. As the salt concretes are used in the sense of a mass concrete the heat of hydration induces thermal restraint stresses inside the concrete bodies and the neighboring rocks. To show the integrity of the geological and technical barriers thermo-mechanical computations were carried out. In the numerical code which is used for safety analyses a so-called hydration model was implemented describing the evolution of strength and Young’s modulus of the concretes in relation to the degree of hydration. The hydration model includes a transformation of the temperature-dependent setting process from real time into an equivalent age, which is equal to the setting time at a temperature of 293 K. Thereafter, a coupling of the equivalent age to the degree of hydration leads to a temperature-independent description of the setting process. As the hydration of concretes strongly correlates with the amount of the generated hydration heat, the model parameters were derived from laboratory tests including measurements of the adiabatic temperature rise.

scholarly journals Effect of Waste Glass on the Properties and Microstructure of Magnesium Potassium Phosphate Cement

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2073
Author(s):  
Qiubai Deng ◽  
Zhenyu Lai ◽  
Rui Xiao ◽  
Jie Wu ◽  
Mengliang Liu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Glass Powder ◽  
Setting Time ◽  
Potassium Phosphate ◽  
Heat Of Hydration ◽  
Waste Glass ◽  
Hydration Heat ◽  
Magnesium Potassium Phosphate Cement ◽  
The Matrix ◽  
Powder Content

Waste glass is a bulk solid waste, and its utilization is of great consequence for environmental protection; the application of waste glass to magnesium phosphate cement can also play a prominent role in its recycling. The purpose of this study is to evaluate the effect of glass powder (GP) on the mechanical and working properties of magnesium potassium phosphate cement (MKPC). Moreover, a 40mm × 40mm × 40mm mold was used in this experiment, the workability, setting time, strength, hydration heat release, porosity, and microstructure of the specimens were evaluated. The results indicated that the addition of glass powder prolonged the setting time of MKPC, reduced the workability of the matrix, and effectively lowered the hydration heat of the MKPC. Compared to an M/P ratio (MgO/KH2PO4 mass ratio) of 1:1, the workability of the MKPC with M/P ratios of 2:1 and 3:1 was reduced by 1% and 2.1%, respectively, and the peak hydration temperatures were reduced by 0.5% and 14.6%, respectively. The compressive strength of MKPC increased with an increase in the glass powder content at the M/P ratio of 1:1, and the addition of glass powder reduced the porosity of the matrix, effectively increased the yield of struvite-K, and affected the morphology of the hydration products. With an increase in the M/P ratio, the struvite-K content decreased, many tiny pores were more prevalent on the surface of the matrix, and the bonding integrity between the MKPC was weakened, thereby reducing the compressive strength of the matrix. At less than 40 wt.% glass powder content, the performance of MKPC improved at an M/P ratio of 1:1. In general, the addition of glass powders improved the mechanical properties of MKPC and reduced the heat of hydration.

Study on the hydration heat of binder paste in high-performance concrete

2002 ◽  
Vol 32 (9) ◽  
pp. 1483-1488 ◽  
Author(s):  
Yunsheng Zhang ◽  
Wei Sun ◽  
Sifeng Liu
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Hydration Heat

Evaluation of Setting Time in Ultra High Performance Concrete

2012 ◽  
Vol 525-526 ◽  
pp. 621-624
Author(s):  
Sung Wook Kim ◽  
Jung Jun Park ◽  
Doo Youl Yoo ◽  
Young Soo Yoon
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Setting Time ◽  
Autogenous Shrinkage ◽  
High Strength ◽  
Initial Crack ◽  
Test Method ◽  
Plastic State ◽  
Ultra High Performance Concrete ◽  
Confining Stress

Ultra high performance concrete (UHPC), characterized by a high strength and high ductility, is also subjected to large shrinkage due to its low water-to-binder ratio and its large content in high fineness materials. The large amount of autogenous shrinkage of UHPC can induce crack on structural member when it was restrained with reinforcement and form. However, shrinkage of UHPC in plastic state is not generating confining stress, which is the main cause of initial crack. Normally, the setting time in concrete is an index to distinguish shrinkage which occur confining stress or not. An estimation of setting time is conducted in compliance with ASTM C 403 till now however, that test standard reveals error of results due to discordance of test condition as following with concrete type. This study therefore evaluated setting time of UHPC through the modified test method which was proposed by KICT. Test results and analyses proved a discrepancy of setting time between ASTM and proposed method. The proposed method put faith in evaluation of setting time in accordance with UHPC.

Potential of finely ground limestone powder to benefit ultra-high performance concrete mixtures

2017 ◽  
Vol 141 ◽  
pp. 335-342 ◽  
Author(s):  
Jedadiah F. Burroughs ◽  
Jay Shannon ◽  
Todd S. Rushing ◽  
Kevin Yi ◽  
Quinn B. Gutierrez ◽  
...  
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Limestone Powder ◽  
Ultra High Performance Concrete ◽  
Concrete Mixtures ◽  
Ground Limestone

scholarly journals Mechanical Performance and Microstructure of Ultra-High-Performance Concrete Modified by Calcium Sulfoaluminate Cement

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Meimei Song ◽  
Chuanlin Wang ◽  
Ying Cui ◽  
Qiu Li ◽  
Zhiyang Gao
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Ultra High Performance Concrete ◽  
Maximum Heat ◽  
Degree Of Hydration ◽  
Calcium Sulfoaluminate ◽  
Shrinkage Property

High autogenous shrinkage property is one of the disadvantages of ultra-high-performance concrete (UHPC), which may induce early age cracking and threaten the safety of concrete structure. In the present study, different dosages of calcium sulfoaluminate (CSA) cement were added in UHPC as an effective expansive binder. Hydration mechanism, autogenous shrinkage property, and compressive strength of UHPC were carried out to investigate the effect of CSA addition on the mechanical properties of UHPC. Scanning electron microscopy was also employed to characterize the intrinsic microstructural reasons relating to the changes in macroproperties. Based on the XRD diagram, increasing formation of ettringite and Ca(OH)2 can be found with increasing CSA content up to 15%. In the heat flow results of UHPC with 10% CSA addition, the maximum heat release increases to 2.6 mW/g, which is 8.3% higher than the reference UHPC, suggesting a higher degree of hydration with CSA addition. The results in autogenous shrinkage show that CSA expansion agent plays a significantly beneficial role in improving the autogenous shrinkage of UHPC. The corresponding autogenous shrinkage of UHPC is −59.66 μ ε , −131.11 μ ε , and −182.31 μ ε , respectively, at 7 d with 5%, 10%, and 15% addition, which is 108%, 117%, and 123% reduction compared to the reference specimen without CSA. In terms of compressive strength, UHPC with 5%, 10%, 15%, and 20% CSA addition has 10.5%, 17.4%, 30.2%, and 22.1% higher compressive strength than that for the reference UHPC at 28 d. Microstructural study shows that there is an extremely dense microstructure in both the bulk matrix and interfacial transition zone of UHPC with 10% CSA addition, which can be attributed to the higher autogenous shrinkage property and can therefore result in higher mechanical performance.

scholarly journals Cost-Effective High-Performance Concrete: Experimental Analysis on Shrinkage

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2730
Author(s):  
Barbara Kucharczyková ◽  
Dalibor Kocáb ◽  
Petr Daněk ◽  
Ivailo Terzijski
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Setting Time ◽  
Mechanical Strain ◽  
Cost Effective ◽  
Strain Gauges ◽  
Early Age ◽  
Dry Air ◽  
First Case

This paper focuses on the experimental determination of the shrinkage process in Self-Compacting High-Performance Concrete (SCC HPC) exposed to dry air and autogenous conditions. Special molds with dimensions of 100 mm × 60 mm × 1000 mm and 50 mm × 50 mm × 300 mm equipped with one movable head are used for the measurement. The main aim of this study is to compare the shrinkage curves of SCC HPC, which were obtained by using different measurement devices and for specimens of different sizes. In addition, two different times t0 are considered for the data evaluation to investigate the influence of this factor on the absolute value of shrinkage. In the first case, t0 is the time of the start of measurement, in the second case, t0 is the setting time. The early-shrinkage (48 h) is continuously measured using inductive sensors leant against the movable head and with strain gauges embedded inside the test specimen. To monitor the long term shrinkage, the specimens are equipped with special markers, embedded into the specimens’ upper surface or ends. These markers serve as measurement bases for the measurement using mechanical strain gauges. The test specimens are demolded after 48 h and the long term shrinkage is monitored using the embedded strain gauges (inside the specimens) and mechanical strain gauges that are placed, in regular intervals, onto the markers embedded into the specimens’ surface or ends. The results show that both types of measurement equipment give a similar result in the case of early age measurement, especially for the specimens cured under autogenous conditions. However, the early age and especially long term measurement are influenced by the position of the measurement sensors, particularly in the case of specimens cured under dry air conditions. It was proven that the time t0 have a fundamental influence on the final values of the shrinkage of investigated SCC HPC and have a significant impact on the conclusions on the size effect.

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