Research of Mechanical Properties of Concretes as Cement-Based Porous Materials

2012 ◽  
Vol 174-177 ◽  
pp. 322-325
Author(s):  
Ling Yun Meng
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Water Pressure ◽  
Drying Shrinkage ◽  
Repulsive Force ◽  
Shrinkage Stress ◽  
Early Age ◽  
Capillary Water ◽  
Drying Shrinkage Stress ◽  
Over Time

Abstract: The concrete as a porous cement-based material is widely used in practice. The analysis of the basic reason why the drying shrinkage stress develops in concrete at early age is made by using the principal of the equilibrium between capillary water repulsive force and molecular attracting force. The model for computing the drying shrinkage stress for nonbinding concrete is presented by relating the capillary water pressure to relative humidity. Based on it ,the model for concrete fully restrained is given. The measurement of the drying shrinkage stress and depth of cracks caused by the drying shrinkage stress is made by using translation symmetric theorem and adopting dog-shaped specimens, and the analysis of changes in depth of cracks over time for two kinds of specimens is made. using the method of comparison ,the comparison of the gradient of the drying shrinkage stress for two kinds of specimens is made ,and it comes to the conclusion that the median drying shrinkage stress in the concrete fully restrained is higher in value by 1MPa compared to the drying shrinkage stress in non-restrained concrete

scholarly journals Evaluation of the Thermal and Shrinkage Stresses in Restrained High-Performance Concrete

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3680 ◽  
Author(s):  
Yang Yang ◽  
Linhao Ma ◽  
Jie Huang ◽  
Chunping Gu ◽  
Zhenjian Xu ◽  
...  
Keyword(s):  
Thermal Stress ◽  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Shrinkage Stress ◽  
Early Age ◽  
Volume Deformation ◽  
Curing Conditions ◽  
Drying Shrinkage Stress

The early age volume deformation is the main course for the cracking of high-performance concrete (HPC). Hence, the shrinkage behavior and the restrained stress development of HPC under different restraints and curing conditions were experimentally studied in this paper. The method to separate the stress components in the total restraint stress was proposed. The total restrained stress was separated into autogenous shrinkage stress, drying shrinkage stress and thermal stress. The results showed that the developments of the free shrinkage (autogenous shrinkage and drying shrinkage) and the restrained stress were accelerated when the drying began; but the age when the drying began did not significantly influence the long-term shrinkage and restrained stress of HPC; the autogenous shrinkage stress continuously contributed to the development of the total restrained stress in HPC; the drying shrinkage stress developed very rapidly soon after the drying began; and the thermal stress was generated when the temperature dropped. The thermal stress was predominant at the early age, but the contributions of the three stresses to the total restrained stress were almost the same at the age of 56 d in this study.

scholarly journals Performance of Fly Ash-Based Inorganic Polymer Mortar with Petroleum Sludge Ash

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4143
Author(s):  
Mubarak Usman Kankia ◽  
Lavania Baloo ◽  
Nasiru Danlami ◽  
Bashar S. Mohammed ◽  
Sani Haruna ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Sodium Hydroxide ◽  
Waste Product ◽  
Drying Shrinkage ◽  
Weight Percent ◽  
Early Age ◽  
Petroleum Sludge ◽  
Precursor Material ◽  
Polymer Mortar ◽  
Sludge Ash

Petroleum sludge is a waste product resulting from petroleum industries and it is a major source of environmental pollution. Therefore, developing strategies aimed at reducing its environmental impact and enhance cleaner production are crucial for environmental mortar. Response surface methodology (RSM) was used in designing the experimental work. The variables considered were the amount of petroleum sludge ash (PSA) in weight percent and the ratio of sodium silicate to sodium hydroxide, while the concentration of sodium hydroxide was kept constant in the production of geopolymer mortar cured at a temperature of 60 °C for 20 h. The effects of PSA on density, compressive strength, flexural strength, water absorption, drying shrinkage, morphology, and pore size distribution were investigated. The addition of PSA in the mortar enhanced the mechanical properties significantly at an early age and 28 days of curing. Thus, PSA could be used as a precursor material in the production of geopolymer mortar for green construction sustainability. This study aimed to investigate the influence of PSA in geopolymer mortar.

scholarly journals Effect of Portland Cement versus Sulphoaluminate Cement on the Properties of Blended Lime-Based Mortars Prepared by Carbide Slag

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1012
Author(s):  
Song Nie ◽  
Jianfeng Wang ◽  
Mingzhang Lan ◽  
Yali Wang ◽  
Qiaowei Zhang
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Water Absorption ◽  
Drying Shrinkage ◽  
Hydrated Lime ◽  
Capillary Water ◽  
Capillary Water Absorption ◽  
Sulphoaluminate Cement ◽  
Carbide Slag ◽  
Green Development

In order to improve the properties of lime-based mortars and promote the green development of the construction industry, blended lime-based mortars were prepared by using carbide slag instead of hydrated lime, and the additions of Portland cement and sulphoaluminate cement were studied in our work. The paper focused on mechanical properties, porosity, capillary water absorption and drying shrinkage of both types of blended mortars. The chemical composition and microstructure of hydration products were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that sulphoaluminate cement provided more contributions to mechanical properties, capillary water absorption and early shrinkage compared to Portland cement.

Modeling Drying Shrinkage Stress Gradients in Concrete

2004 ◽  
Vol 26 (2) ◽  
pp. 1-8 ◽  
Author(s):  
Zachary C. Grasley ◽  
David A. Lange
Keyword(s):  
Drying Shrinkage ◽  
Shrinkage Stress ◽  
Stress Gradients ◽  
Drying Shrinkage Stress

Effect of Steel and Alkaline-Resistance Glass Fibre on Mechanical and Durability Properties of Lightweight Foamed Concrete

2012 ◽  
Vol 626 ◽  
pp. 404-410 ◽  
Author(s):  
Muhammad Hafiz Ahmad ◽  
Hanizam Awang
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Water Absorption ◽  
Glass Fibre ◽  
Steel Fibre ◽  
Drying Shrinkage ◽  
Early Age ◽  
Durability Properties ◽  
Alkaline Resistance ◽  
Foamed Concrete

This paper investigates the effect of steel fibre and alkaline-resistance glass fibre lightweight foamed concrete with fly ash inclusion towards mechanical and durability properties. The lightweight foamed concrete (LFC) with a density of 1000 kg/m3with constant water sand ratio of 1: 1:5 and water cement ratio of 0.45 was cast and tested. Steel and alkaline-resistance glass fibres were used as additives and 30% of cement was replaced by fly ash. Detail experiments were setup to study the behaviour and reaction of additives which is expected to give different results on mechanical and durability properties of LFC. Compared to AR-glass fibre, steel fibre has greater contribution in terms of mechanical properties. SFLFC resulted as the most effective approach for compressive, flexural, tensile split and water absorption with strength 6.13 N/mm2, 1.96 N/mm2, 1.52 N/mm2and lowest water absorption at 6.5% respectively. On the other hand, AR-glass fibre is better in controlling drying shrinkage which leads to controlling the cracking at early age. Fly ash does not change the mechanical properties and durability due to unprocessed stage to its finer forms.

Internal Relative Humidity and Drying Shrinkage of Lightweight Aggregate Concrete

2014 ◽  
Vol 629-630 ◽  
pp. 473-480
Author(s):  
Xiu Hua Zheng ◽  
Yu Feng Zhai ◽  
Shi Zuo Zhan ◽  
Shu Jie Song
Keyword(s):  
Relative Humidity ◽  
Early Stage ◽  
Drying Shrinkage ◽  
Lightweight Aggregate ◽  
Lightweight Aggregate Concrete ◽  
Early Age ◽  
Aggregate Concrete ◽  
Cement Ratio ◽  
Air Content ◽  
Internal Relative Humidity

In this paper, the influence of water cement ratio, prewetting degree of lightweight aggregate, flyash content and air content on the internal relative humidity (IRH) and drying shrinkage of lightweight aggregate concrete (LAC) were studied using a relative humidity sensor and drying shrinkage apparatus. Results showed that the IRH of concrete decreased rapidly at early age and slowed down at late age, and prewetting lightweight aggregate could compensate the loss of IRH. The effect of compensation could be enhanced with the increasing of prewetting degree of lightweight aggregate, and the addition of flyash retarded the decrease of IRH at early age. The drying shrinkage of LAC increased quickly at early stage and it slowed down to the even after 60 days or longer age. Furthermore, the drying shrinkage of LAC increased with increasing of water cement ratio. The effect of air content on the drying shrinkage of LAC was limited at early stage. However, at the late stage it grew at different level with increasing of air content. By raising the prewetting degree of lightweight aggregate, mixing with proper dosage of flyash, the shrinkage rate of LAC can be reduced markedly. Key words: lightweight aggregate concrete, internal relative humidity, drying shrinkage, prewetting degree, flyash.

scholarly journals The Modeling Research on the Early-Age Shrinkage of UHPFRC in Different Curing Conditions

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Song Han ◽  
Yazhou Liu ◽  
Dan Liu ◽  
Mingzhe An ◽  
Ziruo Yu
Keyword(s):  
Relative Humidity ◽  
Pore Structure ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Calculation Model ◽  
Fiber Reinforced Concrete ◽  
Early Age ◽  
Chemical Shrinkage ◽  
Hydration Degree ◽  
Curing Conditions

The early-age shrinkage of ultra-high performance fiber reinforced concrete (UHPFRC) in dry, sealed, and soaked curing was systematically measured. The calculation model of early-age shrinkage was established based on the theory of shrinkage of cementitious materials. According to the results of the relative humidity, hydration degree, pore structure, and elastic modulus of hardened slurry, the shrinkage calculation model in different curing conditions was calibrated. The results show that the early-age shrinkage of UHPFRC can be divided into three parts: chemical shrinkage, autogenous shrinkage caused by self-drying, and drying shrinkage caused by external drying. Based on the degree of hydration, the chemical shrinkage model was established. Based on the pore structure, the hydration degree, and the relative humidity of hardened slurry, the autogenous shrinkage model was established by introducing the effective pore coefficient. The drying shrinkage model was established based on the internal humidity. According to the shrinkage of soaked samples, the calculated value of chemical shrinkage in sealed and drying conditions was calibrated. This research provides theoretical support for the structural design and engineering application of UHPFRC.

scholarly journals Synergistic Benefits of Using Expansive and Shrinkage Reducing Admixture on High-Performance Concrete

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2514 ◽  
Author(s):  
Tian-Feng Yuan ◽  
Seong-Kyum Kim ◽  
Kyung-Teak Koh ◽  
Young-Soo Yoon
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Shrinkage Stress ◽  
Early Age ◽  
Test Results ◽  
Shrinkage Cracking ◽  
Shrinkage Cracks ◽  
Shrinkage Reducing Admixture

High-performance concrete (HPC) is widely used in construction according to great mechanical properties, but it has a high risk of shrinkage cracking due to autogenous shrinkage stress. Therefore, the aim of this research was to investigate the effect of a combination of expansive admixture (EA) and shrinkage reducing admixture (SA) on the autogenous shrinkage of high-performance concrete without heat treatment. Two different EA to cement weight ratios of 0.0, 5.0%, and two different SA to cement weight ratios of 0.0, and 1.0% were combined and considered. To investigate the differences in the time-zero conditions effect on the autogenous shrinkage behaviors, four different initial points were compared. The test results indicate that the EA and/or SA content was conductive to a little bite increase compressive strength (22.6–37.9%) and tensile strength (<4.8%). According to the synergistic effect of the EA and SA on the HPC, the autogenous shrinkage significantly decreased (<50%), as compared to those specimens with only one type of admixture (EA or SA). Furthermore, all the specimens incurred restrained autogenous shrinkage cracks at an early age, except the specimen using the combined EA and SA. Therefore, it can be concluded that the combination of EA and SA is effective for improving the properties of HPC.

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