Curing temperature: A key factor that changes the effect of TiO2 nanoparticles on mechanical properties, calcium hydroxide formation and pore structure of cement mortars

Purpose This paper aims to assess the effects of chemically accelerated leaching on the physical and mechanical properties of aerial lime–cement mortars (LCMs). Design/methodology/approach Two aerial LCMs, differencing mainly in their calcium hydroxide content, were degraded by the use of an ammonium nitrate solution as a leaching agent. The leaching effects were studied by evaluating the rate of change in physical (sorptivity and mass loss) and mechanical (flexural and compressive strength) characteristics of aerial LCMs. To quantify the evolution and kinetics of degradation, the leached depth was then characterized at different levels of degradation by means of a phenolphthalein solution. Findings The experimental results showed that the dissolution of binder decreases the mass, alkalinity and strength of aerial LCMs but increases their sorptivity. A linear relationship was derived by plotting the values of leached depth against the square root of immersion time in an aggressive solution. It was found that the leached depth followed diffusion-controlled kinetics. Originality/value It was found that the global loss of compressive strength of aerial LCMs because of complete dissolution of calcium hydroxide can reach up to 80 per cent.

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Incorporation of Iraqi Rocks in the Production of Eco-Friendly Cement Mortar

Engineering and Technology Journal ◽

10.30684/etj.v38i10a.1479 ◽

2020 ◽

Vol 38 (10A) ◽

pp. 1522-1530

Author(s):

Rawnaq S. Mahdi ◽

Aseel B. AL-Zubidi ◽

Hassan N. Hashim

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Compressive Strength ◽

Water Absorption ◽

Structural Properties ◽

Mechanical Milling ◽

Cement Mortar ◽

Cement Mortars

This work reports on the incorporation of Flint and Kaolin rocks powders in the cement mortar in an attempt to improve its mechanical properties and produce an eco-friendly mortar. Flint and Kaolin powders are prepared by dry mechanical milling. The two powders are added separately to the mortars substituting cement partially. The two powders are found to improve the mechanical properties of the mortars. Hardness and compressive strength are found to increase with the increase of powders constituents in the cement mortars. In addition, the two powders affect water absorption and thermal conductivity of the mortar specimens which are desirable for construction applications. Kaolin is found to have a greater effect on the mechanical properties, water absorption, and thermal conductivity of the mortars than Flint. This behavior is discussed and analyzed based on the compositional and structural properties of the rocks powders.

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Influence of Gating System Parameters of Die-Cast Molds on Properties of Al-Si Castings

Materials ◽

10.3390/ma14133755 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3755

Author(s):

Štefan Gašpár ◽

Tomáš Coranič ◽

Ján Majerník ◽

Jozef Husár ◽

Lucia Knapčíková ◽

...

Keyword(s):

Mechanical Properties ◽

Computer Modelling ◽

Permanent Deformation ◽

Surface Hardness ◽

Technological Parameters ◽

Inlet System ◽

Die Cast ◽

Key Factor ◽

Fine Grained Structure ◽

Design Solutions

The resulting quality of castings indicates the correlation of the design of the mold inlet system and the setting of technological parameters of casting. In this study, the influence of design solutions of the inlet system in a pressure mold on the properties of Al-Si castings was analyzed by computer modelling and subsequently verified experimentally. In the process of computer simulation, the design solutions of the inlet system, the mode of filling the mold depending on the formation of the casting and the homogeneity of the casting represented by the formation of shrinkages were assessed. In the experimental part, homogeneity was monitored by X-ray analysis by evaluating the integrity of the casting and the presence of pores. Mechanical properties such as permanent deformation and surface hardness of castings were determined experimentally, depending on the height of the inlet notch. The height of the inlet notch has been shown to be a key factor, significantly influencing the properties of the die-cast parts and influencing the speed and filling mode of the mold cavity. At the same time, a significant correlation between porosity and mechanical properties of castings is demonstrated. With the increasing share of porosity, the values of permanent deformation of castings increased. It is shown that the surface hardness of castings does not depend on the integrity of the castings but on the degree of subcooling of the melt in contact with the mold and the formation of a fine-grained structure in the peripheral zones of the casting.

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Study on effect of mechanical sand on mechanical properties and fractal characteristics of mortar pore structure

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/643/1/012039 ◽

2021 ◽

Vol 643 ◽

pp. 012039

Author(s):

Can Chen ◽

Haicheng Yang ◽

Fang Yu

Keyword(s):

Mechanical Properties ◽

Pore Structure ◽

Fractal Characteristics

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Characteristics of Lightweight Cellular Concrete and Effects on Mechanical Properties

Materials ◽

10.3390/ma13122678 ◽

2020 ◽

Vol 13 (12) ◽

pp. 2678 ◽

Cited By ~ 1

Author(s):

Wei Yu ◽

Xu Liang ◽

Frank Mi-Way Ni ◽

Abimbola Grace Oyeyi ◽

Susan Tighe

Keyword(s):

Mechanical Properties ◽

Pore Structure ◽

High Definition ◽

Pore Characteristics ◽

Software Applications ◽

Solid Part ◽

Electron Microscopes ◽

Lab Test ◽

Scanning Electron Microscopes ◽

Cellular Concrete

This study investigated the pore structure and its effects on mechanical properties of lightweight cellular concrete (LCC) in order to understand more and detailed characteristics of such structure. As part of investigation, environment scanning electron microscopes (ESEM) and industrial high-definition (HD) macro photography camera were separately used to capture and compare images of specimens. Physical properties of the pore structure, including pore area, size, perimeter, fit ellipse, and shape descriptors, were studied based on the image processing technology and software applications. Specimens with three different densities (400, 475, and 600 kg/m3) were prepared in the laboratory. Firstly, the effects of density on the characteristics of pore structure were investigated; furthermore, mechanical properties (compressive strength, modulus of elasticity and Poisson’s ratio, flexural strength and splitting tensile strength of LCC) were tested. The relationships among pore characteristics, density, and mechanical properties were analyzed. Based on the results obtained from the lab test—comparisons made between specimens with high-densities and those with low-densities—it was found significant variability in bubble size, thickness, and irregularity of pores. Furthermore, the increase of density is accompanied by better mechanical properties, and the main influencing factors are the thickness of the solid part and the shape of the bubble. The thicker of solid part and more regular pores of LCC has, the better mechanical properties are.

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The characterization and preparation of porous low dielectric films using various cyclodextrins as template materials

MRS Proceedings ◽

10.1557/proc-766-e8.10 ◽

2003 ◽

Vol 766 ◽

Cited By ~ 7

Author(s):

Jin-Heong Yim ◽

Jung-Bae Kim ◽

Hyun-Dam Jeong ◽

Yi-Yeoul Lyu ◽

Sang Kook Mah ◽

...

Keyword(s):

Thin Film ◽

Mechanical Properties ◽

Dielectric Constant ◽

Pore Structure ◽

Pore Diameter ◽

Dielectric Films ◽

Low Dielectric Constant ◽

Cyclodextrin Derivatives ◽

Low Dielectric ◽

Low K

AbstractPorous low dielectric films containing nano pores (∼20Å) with low dielectric constant (<2.2), have been prepared by using various kinds of cyclodextrin derivatives as porogenic materials. The pore structure such as pore size and interconnectivity can be controlled by changing functional groups of the cyclodextrin derivatives. We found that mechanical properties of porous low-k thin film prepared with mCSSQ (modified cyclic silsesquioxane) precursor and cyclodextrin derivatives were correlated with the pore interconnection length. The longer the interconnection length of nanopores in the thin film, the worse the mechanical properties of the thin film (such as hardness and modulus) even though the pore diameter of the films were microporous (∼2nm).

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