Hardened alite pastes of various porosities. I. Degree of hydration, compressive strength and total porosity

Carbonation durability is an important subject for recycled coarse aggregate concrete (RAC) applied to structural concrete. Extensive studies were carried out on the carbonation resistance of RAC under general environmental conditions, but limited researches investigated carbonation resistance when exposed to chloride ion corrosion, which is an essential aspect for reinforced concrete materials to be adopted in real-world applications. This paper presents a study on the carbonation durability of two generations of 100% RAC with the effect of chloride ion corrosion. The quality evolution of recycled concrete coarse aggregate (RCA) with the increasing recycling cycles was analyzed, and carbonation depth, compressive strength and the porosity of RAC were measured before and after chloride ion corrosion. The results show that the effect of chloride ion corrosion negatively affected the carbonation resistance of RAC, and the negative effect was more severe with the increasing recycling cycles of RCA. Chloride ion corrosion led to a decrease in compressive strength, while an increase in carbonation depth and the porosity of RAC. The equation of concrete total porosity and carbonation depth was established, which could effectively judge the deterioration of carbonation resistance of RAC.

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Influence of Restrained Condition on Mechanical Properties, Frost Resistance, and Carbonation Resistance of Expansive Concrete

Materials ◽

10.3390/ma13092136 ◽

2020 ◽

Vol 13 (9) ◽

pp. 2136

Author(s):

Nguyen Duc Van ◽

Emika Kuroiwa ◽

Jihoon Kim ◽

Hyeonggil Choi ◽

Yukio Hama

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Frost Resistance ◽

Total Porosity ◽

Length Change ◽

Ratio Test ◽

Expansive Concrete ◽

Restrained Condition ◽

Carbonation Resistance ◽

Compressive Strength Test

This paper presents the results of an experimental investigation of the effect of the restrained condition on the mechanical properties, frost resistance, and carbonation resistance of expansive concrete with different water–binder ratios. In this study, length change ratio test, expansion strain test, compressive strength test, mercury intrusion porosimetry test, underwater weighing test, freezing–thawing test, and accelerated carbonation test were performed to evaluate the mechanical properties, pore size distribution, total porosity, and durability of expansive concrete under both restrained and unrestrained conditions. The test results indicate that the length change ratio and expansion strain of the expansive concrete were controlled by the restrained condition. The compressive strength of expansive concrete was enhanced by the triaxial restraining when the amount of expansive additive was 40 kg/m3 of concrete. Two hypotheses were described to explain the change of pore structure change expansive mortar. The results also indicate that the carbonation resistance and frost resistance were improved by the uniaxial restrained condition. Furthermore, the effect of the restrained condition must be considered to evaluate not only the experimental results of the expansive concrete with a high EX replacement level but also the expansive concrete combining other cement replacement materials.

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The Influence of Pore-Strucrure on the Campressive Strength of Hardened Cement Paste

MRS Proceedings ◽

10.1557/proc-42-123 ◽

1984 ◽

Vol 42 ◽

Cited By ~ 4

Author(s):

Huang Yiun-Yuan ◽

Ding Wei ◽

Lu Ping

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Pore Structure ◽

Cement Paste ◽

Total Porosity ◽

Hardened Cement ◽

Hardened Cement Paste ◽

New Information ◽

The Relationship ◽

Empirical Constants

AbstractThe pore-structure strongly influences the carpressive strength of hardened cement paste (hcp) and other porous materials, as well as other mechanical properties. The simplest but most currently used expression representing the relationship between the pore-structure and compressive strength is fram Balshin: σ = σ0 (l-P)A, in which only the total porosity P is involved as a single parameter and σ0 and A are empirical constants. The influence of pore size distribution and pore shapes etc. are not considered.The authors introduce second parameter w - the factor of relative specific surface area of the pores other than the total porosity P into consideration and a new expression is proposed:σc=K11-p/1+2p(K2(1-p))K3w+K4 all the constants K1 - K4 can be determined experimentally. By using of this expression the new information relating the influence of pore-structure on the caopressive strength of hcp can be predicted.

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Porosity In The Microstructure Of Blended Cements Containing Fly Ash

MRS Proceedings ◽

10.1557/proc-137-381 ◽

1988 ◽

Vol 137 ◽

Cited By ~ 1

Author(s):

H. H. Patel ◽

P. L. Pratt ◽

L. J. Parrott

Keyword(s):

Compressive Strength ◽

Image Analysis ◽

Fly Ash ◽

Blended Cement ◽

Total Porosity ◽

Major Change ◽

Relative Volume ◽

Blended Cements ◽

Backscattered Electron ◽

Electron Imaging

AbstractThe changes in porosity of OPC and an OPC-fly ash blended cement during hydration have been studied at water/solids ratios of 0.35, 0.47 and 0.59, cured for times of up to 1 year at 25°C. The porosity was measured indirectly by methanol exchange and methanol adsorption techniques and, directly, by quantitative image analysis using backscattered electron imaging in the scanning electron microscope. Measurements of porosity and of remaining anhydrous material by image analysis showed good correlation with indirect methods. Measurement of the diffusion of methanol and of the compressive strength were made in parallel with the determination of the porosity during hydration and attempts were made to relate the properties to the microstructure. For both binders the reduction of total porosity with increased reaction was small. The major change in pore structure was the subdivision of coarse pores by gel to form finer pores. Compressive strength and diffusion properties were dominated by the relative volume of coarse pores.

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Degree of hydration and compressive strength of conditioned samples made of normal and blended cement system

KSCE Journal of Civil Engineering ◽

10.1007/s12205-011-1193-x ◽

2011 ◽

Vol 15 (7) ◽

pp. 1253-1257 ◽

Cited By ~ 11

Author(s):

Nasir Shafiq

Keyword(s):

Compressive Strength ◽

Blended Cement ◽

Degree Of Hydration ◽

Cement System

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INVESTIGATIONS ON THE RELATIONSHIP BETWEEN POROSITY AND STRENGTH OF ADMIXTURES MODIFIED HIGH PERFORMANCE SELF-COMPACTING CONCRETE

Journal of Civil Engineering and Management ◽

10.3846/13923730.2014.897978 ◽

2016 ◽

Vol 22 (4) ◽

pp. 520-528 ◽

Cited By ~ 1

Author(s):

Beata ŁAŹNIEWSKA-PIEKARCZYK

Keyword(s):

Compressive Strength ◽

High Performance ◽

Total Porosity ◽

Self Compacting Concrete ◽

Research Results ◽

Air Content ◽

New Generation ◽

The Relationship ◽

Viscosity Modifying Admixture

The influence of a type of new generation: superplasticizer (SP), anti-foaming admixture (AFA) and viscosity modifying admixture (VMA) on the air-content, workability of high performance self-compacting concrete (HPSCC) is analyzed in the paper. The purpose of this study was to examine the influence of type of the admixtures on porosity of HPSCC in the aspect of the compressive strength. The research results indicated that type of admixtures and its combinations result in different strengths of HPSCC, regardless of the total porosity characteristics of HPSCC.

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A Study on the Development Mechanism of Early Strength in Cement Mortar Using an Early-Strength Polycarboxylated Agent

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.348-349.473 ◽

2007 ◽

Vol 348-349 ◽

pp. 473-476

Author(s):

Won Jun Park ◽

Han Seung Lee ◽

Ki Bong Park

Keyword(s):

Compressive Strength ◽

High Performance ◽

Cement Mortar ◽

Early Age ◽

Hydration Products ◽

Degree Of Hydration ◽

Exact Analysis ◽

Mortar Strength ◽

Early Strength ◽

Micro Structures

It is well known that PC (polycarboxylate) agent is superior to other agents for the early-strength of concrete. Thus, this study investigates the development of mortar strength using various agents. To prove this, various factors were tested. Furthermore, this study measured compressive strength at the age of 18, 24, 36, 72, and 168 hours and gave a request text TG/DTA to observe minute structures. In addition, this study took pictures of minute structures using an SEM for each agent at the same age. According to the results, mortar using an early-strength PC agents is faster than a general water reducing AE agent, high performance PC agents, and other agents in the acceleration of hydration at the same early age. A TG/DTA test shows that the early-strength PC agents create more hydration products, such as Ca(OH)2, than others at the same age. The degree of pH in each agent is unrelated to the degree of hydration in mortar. An MIP analysis confirms these results. However, other methods are required the exact analysis of micro structures.

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

Advances in Civil Engineering ◽

10.1155/2021/4002536 ◽

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.

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