Influence of Superplasticizer Quantity on Formation of Micro-Cracks during Setting and Hardening of Concretes by Acoustic Emission Method

2015 ◽  
Vol 1124 ◽  
pp. 219-224 ◽  
Author(s):  
Libor Topolář ◽  
Kristýna Timcakova ◽  
Petr Misák
Keyword(s):  
Acoustic Emission ◽  
Building Materials ◽  
Material Behaviour ◽  
Emission Method ◽  
Alkali Activated Slag ◽  
Volumetric Expansion ◽  
Hardening Process ◽  
Micro Cracks ◽  
Activated Slag ◽  
Alkali Activated

The acoustic emission phenomenon is directly associated with nucleation of cracks in building materials, therefore the changes result from the volumetric expansion causing formation micro and macro cracking in structure, which we can recognize. The main aim of the article is to compare four ways of curing alkali activated slag mortars by method of acoustic emission. A comprehension of microstructure−performance relationships is the key to true understanding of material behaviour. The results obtained in the laboratory are useful to understand the various stages of micro-cracking activity during the hardening process in quasi-brittle materials such as alkali activated slag mortars and extend them for general practice

The Identification of Cracks Formed during the Spontaneous Drying and Hardening of Alkali-Activated Slag for Different Curing Times

2016 ◽  
Vol 827 ◽  
pp. 340-343
Author(s):  
Libor Topolář ◽  
Hana Šimonová ◽  
Lubos Pazdera
Keyword(s):  
Brittle Materials ◽  
Material Behaviour ◽  
Alkali Activated Slag ◽  
Hardening Process ◽  
Curing Method ◽  
Activated Slag ◽  
Alkali Activated

This paper reports the results of measurements during hardening and drying of specimens made of alkali activated slag mortars. The aim of this paper is introduce the effect of curing method and time on the microstructure of alkali activated slag mortars. An understanding of microstructure−performance relationships is the key to true understanding of material behaviour. The results obtained in the laboratory are useful to understand the various stages of micro-cracking activity during the hardening process in quasi-brittle materials such as alkali activated slag mortars and extend them for field applications.

Differences in Electrical Properties of Portland Cement and Alkali-Activated Slag Mortars

2018 ◽  
Vol 276 ◽  
pp. 15-20 ◽  
Author(s):  
Pavel Rovnaník ◽  
Maria Míková ◽  
Ivo Kusák ◽  
Patrik Bayer
Keyword(s):  
Electrical Properties ◽  
Portland Cement ◽  
Building Materials ◽  
Elevated Temperatures ◽  
Sodium Ions ◽  
Alkali Activated Slag ◽  
Self Heating ◽  
Chemical Attack ◽  
Activated Slag ◽  
Alkali Activated

Alkali-activated slag is known as a building material for more than sixty years and is considered an alternative to Portland cement based binders. Compared to Portland cement it exhibits some superior properties such as higher resistance against chemical attack and exposure to elevated temperatures. Aluminosilicate binders are generally electrical insulators; however, electrical properties of building materials gain the importance in the new field of applications such as self-sensing or self-heating materials. This paper brings a comparison of the electrical properties, especially resistance and capacitance, between Portland cement and alkali-activated slag mortars. The measurements revealed that alkali-activated slag shows enhanced conducting properties due to the presence of mobile hydrated sodium ions and metallic iron microparticles.

Electrical Properties of Alkali-Activated Slag Mortar with Carbon Fibres

2017 ◽  
Vol 908 ◽  
pp. 100-105 ◽  
Author(s):  
Pavel Rovnaník ◽  
Maria Míková ◽  
Ivo Kusák
Keyword(s):  
Mechanical Properties ◽  
Electrical Properties ◽  
Building Materials ◽  
Specific Conductivity ◽  
Carbon Fibres ◽  
Alkali Activated Slag ◽  
Order Of Magnitude ◽  
Activated Slag ◽  
Mixing Water ◽  
Alkali Activated

Building materials with enhanced electrical properties gain the importance in the new field of applications such as self-sensing or self-heating materials. In this paper, 3 mm long carbon fibres were used as a conductive admixture to alkali-activated slag mortar in order to reduce its resistivity. The amount of carbon fibres was ranging from 0.5 to 4.0% of the slag mass and the effect of the conductive admixture on the mechanical properties, electrical impedance, specific conductivity, and microstructure of alkali-activated slag composite was investigated. Only 0.5% of carbon fibres caused a significant decrease in impedance of alkali-activated slag composite and the addition of 4% reduced the impedance by one order of magnitude for low AC frequencies. However, due to problematic dispersion and higher demand of mixing water, the mechanical properties were deteriorated, especially at higher content of carbon fibres.

scholarly journals Flexural Fatigue Life Reliability of Alkali-Activated Slag Concrete Freeze-Thaw Damage in Cold Areas

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Bin Chen ◽  
Jun Wang
Keyword(s):  
Fatigue Life ◽  
Building Materials ◽  
Fatigue Properties ◽  
Test Results ◽  
Distribution Fitting ◽  
Flexural Fatigue ◽  
Alkali Activated Slag ◽  
Freeze Thaw ◽  
Activated Slag ◽  
Alkali Activated

Studying the application of alkali-activated slag concrete for roads in cold areas is of great significance for promoting and developing green building materials. In this study, the effect of freeze-thaw damage on the flexural fatigue properties of alkali-activated slag concrete was studied and the fatigue life of alkali-activated slag concrete with various degrees of damage after freeze-thaw cycles was studied through a three-point flexural test. The results show that the flexural fatigue life decreases with freeze-thaw cycles from 0 to 150 times. Through a distribution fitting test and K-S test results, the flexural fatigue life followed both the two-parameter and three-parameter Weibull distributions. Between them, the three-parameter Weibull distribution fitting had a higher accuracy and better test results. The results of the reliability analysis show that the curves of alkali-activated slag concrete samples with various degrees of freeze-thaw damage for various failure probabilities have good correlation under different stresses, and the correlation correlations were greater than 0.81. The flexural fatigue life of alkali-activated slag concrete samples with various degrees of freeze-thaw damage was more sensitive to freeze-thaw damage under high stresses. It is suggested that the fatigue design of alkali-activated slag concrete should consider the adverse effects of cold areas, and the reliability should be improved accordingly.

Crack Initiation of Alkali-Activated Slag Based Composites with Graphite Filler

2018 ◽  
Vol 761 ◽  
pp. 57-60
Author(s):  
Hana Šimonová ◽  
Libor Topolář ◽  
Pavel Rovnaník ◽  
Pavel Schmid ◽  
Zbyněk Keršner
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Building Materials ◽  
Crack Opening ◽  
Graphite Powder ◽  
Unstable Crack ◽  
Alkali Activated Slag ◽  
Fracture Tests ◽  
Activated Slag ◽  
Alkali Activated

The alkali-activated slag is an alternative building material to ordinary Portland cement based materials. This type of material is effective in reducing CO2 emissions and energy consumption. Addition of graphite powder increases its electric conductivity, hence, introducing new functionality to building materials such as self-sensing and self-heating properties. In this study, the effect of graphite filler on the crack initiation of alkali-activated slag composite is investigated. The graphite powder was added in the amount of 5, 10 and 15% with respect to the slag mass. Beam specimens with an initial stress concentrator were tested in three-point bending at the age of 28 days. The load versus crack mouth crack opening displacement (F–CMOD) diagrams were recorded during the fracture tests and subsequently evaluated using the Double-K fracture model. This model allows the quantification of two different levels of crack propagation: initiation, which corresponds to the beginning of stable crack growth, and the level of unstable crack propagation. The course of fracture tests was also monitored by acoustic emission (AE) method.

Sign in / Sign up

Export Citation Format

Share Document