AIR-ENTRAINMENT PROBLEM IN SELF-COMPACTING CONCRETE

2009 ◽  
Vol 15 (2) ◽  
pp. 137-147 ◽  
Author(s):  
Janusz Szwabowski ◽  
Beata Łaźniewska-Piekarczyk
Keyword(s):  
Frost Resistance ◽  
Air Entrainment ◽  
Actual State ◽  
Self Compacting Concrete ◽  
Concrete Technology ◽  
Porosity Structure ◽  
Problematic Issue ◽  
Concrete Testing ◽  
Entrainment Effect ◽  
New Generation

According to the actual state of knowledge and in accordance with the PN‐EN 2006–1 norm, it is recommended to use air‐entrainment as a basic way of assuring frost‐resistance of concrete. In case of self‐compacting concrete (SCC), achieving adequate air‐entrainment is a problematic issue because of one of the side‐effects of the functioning of a new generation of superplasticizers, i.e. excessive air‐entrainment (considerably higher than 2%) in a self‐compacting concrete mix. Thus, in this situation, the dosage of an air‐entraining admixture has to be reduced. It was discovered that the cause of an air‐entrainment effect of superplasticizers is a decrease of the surface tension value of the liquid phase in paste. In the paper, the problem of air‐entrainment is discussed, formed as a result of the functioning of a superplasticizer on the characteristics both of concrete and a mixture, depending on the content. To verify the influence a superplasticizer and an air‐entraining admixture have on concrete porosity structure parameters, concrete samples were tested during 300 cycles of freezing and testing the porosity structure according to PN‐EN 480–11. The tests of the structure show that air pores, depending on the level of mix flowability, can be regular and similar in shape and size to pores formed as a result of air‐entrainment admixture action. According to the actual state of knowledge on concrete technology, concrete is frost‐resistant if the value of porosity structure parameter stays within precisely set limits. The results of concrete testing have shown that the parameters of porosity structure do not stay within the precisely set limits, but self‐compacting concrete gets frost‐resistance F300 according to PN‐88/B‐06250. Issues connected with this fact are the subject of this paper. Santrauka Laikoma, kad betono atsparumą šalčio poveikiui galima užtikrinti naudojant orą įsiurbiančius priedus. Savaime susitankinančio betono orą įsiurbiančių priedų taikymas ypač painus, nes šiuo atveju galima naudoti tik naujos kartos plastiklius, kurie pasižymi didesniu oro įsiurbimu – >2 %. Norint įvertinti superplastiklių ir orą įsiurbiančių priedų įtaką betono porėtosios struktūros parametrams, buvo ištirta betono bandinių po 300 šaldymo ciklų struktūra pagal PN-EN 480-11 normų reikalavimus. Tyrimų rezultatai parodė, kad nors porėtosios struktūros parametrai nevisiškai atitinka reikalavimus, savaime sutankėjantis betonas pagal PN-88/B-06250 reikalavimus yra F300 klasės. Būtent šis klausimas išsamiai nagrinėjamas straipsnyje.

THE INFLUENCE OF THE TYPE OF ANTI-FOAMING ADMIXTURE AND SUPERPLASTICIZER ON THE PROPERTIES OF SELF-COMPACTING MORTAR AND CONCRETE

2012 ◽  
Vol 18 (3) ◽  
pp. 408-415 ◽  
Author(s):  
Beata Łazniewska-Piekarczyk ◽  
Janusz Szwabowski
Keyword(s):  
Compressive Strength ◽  
Air Entrainment ◽  
Similar Degree ◽  
Air Bubbles ◽  
Self Compacting Concrete ◽  
Research Results ◽  
Porosity Structure ◽  
Air Content ◽  
Loss Of Self ◽  
Sem Analyses

To prevent excessive air entrainment, superplasticizers (SPs) should not only be compatible with cement, but also should not create the air-entraining effect in mortar. In order to counteract excessive air entrainment, anti-foaming admixtures (AFAs) can be used to prevent the formation of air bubbles. This paper investigates the influence of the type, amount and time of introduction of AFAs on air-entrainment, rheological properties and workability loss of self-compacting mortar. The research results prove that AFAs decrease air-content in mortar. Mortar containing an AFA does not undergo segregation, as is the case with mortars of a similar degree of fluidity with no AFA and incorporating an SP only. Moreover, mortar with an AFA keeps initial consistency for longer in comparison to mortar with a SP only. The properties of hardened mortar mixes are also investigated. The research results show that AFAs do not have a significant influence on the compressive strength of mortar mixtures. The compressive strength of mortar mixtures incorporating an AFA is similar to mortar with a non-air-entraining SP. Moreover, AFAs increase significantly the flexural strength of mortar. In most cases, AFAs do not decrease the absorbability of mortar. Only two types of AFAs increase slightly the absorbability of mortar. In order to explain this phenomenon, a research was performed investigating the porosity structure according to the EN 480-11 (1999) and SEM analyses of two types of self-compacting concrete (SCC): one made of mortar with an AFA and the other without AFA. The freeze-proof resistance of SCC (made of the same mortar mixes) was also investigated according to PN-88/B-06250 (2003). The results show that the type of AFA and SP significantly influences porosity characteristics and frost-resistance of SCC.

scholarly journals Cements with calcareous fly ash as component of low clinker eco-self compacting concrete

2019 ◽  
Vol 9 (1) ◽  
pp. 196-201
Author(s):  
Jacek Gołaszewski ◽  
Grzegorz Cygan ◽  
Tomasz Ponikiewski ◽  
Małgorzata Gołaszewska
Keyword(s):  
Fly Ash ◽  
Hardened Concrete ◽  
Self Compacting Concrete ◽  
Basic Properties ◽  
Ecological Self ◽  
Different Types ◽  
Hardened State ◽  
Main Component ◽  
New Generation ◽  
Good Workability

AbstractThe main goal of the presented research was to verify the possibility of obtaining ecological self-compacting concrete of low hardening temperature, containing different types of cements with calcareous fly ash W as main component and the influence of these cements on basic properties of fresh and hardened concrete. Cements CEM II containing calcareous fly ash W make it possible to obtain self-compacting concrete (SCC) with similar initial flowability to analogous mixtures with reference cement CEM I and CEM III/B, and slightly higher, but still acceptable, flowability loss. Properties of hardened concretes with these cements are similar in comparison to CEM I and CEM III concretes. By using cement nonstandard, new generation multi-component cement CEM “X”/A (S-W), self-compacting concrete was obtained with good workability and properties in hardened state.

scholarly journals Frost durability of steel fiber self-compacting concrete for pavements

2016 ◽  
Vol 11 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Jerzy Wawrzeńczyk ◽  
Agnieszka Molendowska ◽  
Adam Kłak
Keyword(s):  
Steel Fibre ◽  
Air Entrainment ◽  
Hardened Concrete ◽  
Polymer Microspheres ◽  
Self Compacting Concrete ◽  
Freeze Thaw ◽  
Concrete Mix ◽  
Finished Surface ◽  
Frost Durability ◽  
Scaling Resistance

The paper presents the results from the research on self-compacting concrete with different steel fibre type addition. The reference self-compacting concrete mix with water/binder = 0.33 was prepared, then modified with steel fibres in the amounts of 0–60 kg/m3 and air entrained with polymer microspheres (40 μm diameter). The major objective of the research was to determine the effect of steel fibre and air content on the self-compacting concrete mix properties and hardened concrete frost durability. The tests also included internal cracking and scaling resistance evaluation for concrete specimens subjected to cyclic freeze-thaw process − two beams were frozen in air and two beams were partially submerged in water and then frozen. The scaling resistance was tested using the slab method on the specimens with sawn surface and on the specimens with natural finished surface. Non-air entrained steel fibrereinforced concretes, despite their high strength class (C55/67–C60/75) and medium absorption (4.34–5.11%), showed unsatisfactory resistance to internal cracking and scaling tests. The beams partially submerged in water failed after 100 freeze-thaw cycles, which confirms a significant influence of water uptake from moist environment during freeze-thaw cycles and the acceleration of the damage process. Test results indicate that air entrainment with polymer microspheres is a very effective method and allows obtaining very good air pore structure parameters and frost resistance results. The specimens with top − finished surface exhibited less damage in the scaling resistance tests in relation to the specimens with sawn surface.

The Determination of Frost Resistance on Ultra High Performance Concrete

2014 ◽  
Vol 1025-1026 ◽  
pp. 1005-1009 ◽  
Author(s):  
Michaela Kostelecká ◽  
Jiří Kolísko
Keyword(s):  
Frost Resistance ◽  
High Performance ◽  
High Performance Concrete ◽  
Silica Sand ◽  
Ultra High Performance Concrete ◽  
Concrete Technology ◽  
Normal Concrete ◽  
Different Types ◽  
High Range

The ultra high performance concrete (UHPC) has very special properties that are expressively different of normal concrete. Due to its high compression strength greater than 150 MPa, tensile strength greater than 20 MPa and improved durability, these represent significant advances in concrete technology. These materials include Portland cement, silica fume, quartz flour, fine silica sand, high-range water-reducer, water and either steel or organic fibres. Depending on the type of fibres used can influence the compressive strength. The article describes the tests of frost resistance on UHPC plates with different types of textiles armatures. The aim of the testing is describe influence of textiles armatures in UHPC matrix in extreme conditions.

The Influence of W/C Ratio and Superplasticizer Type on Porosity of Concrete with Air-Entraining Cement with Fly Ash

2018 ◽  
Vol 279 ◽  
pp. 266-270
Author(s):  
Beata Łaźniewska-Piekarczyk
Keyword(s):  
Fly Ash ◽  
Fresh Concrete ◽  
Air Entrainment ◽  
Hardened Concrete ◽  
Research Results ◽  
Concrete Mix ◽  
European Standards ◽  
New Generation ◽  
Air Entrained Concrete

The research results of stability of air-entrainment of concrete acc. PN-EN 480-1 in case of innovate air-entraining multi-component cement CEM II/B-V is presented in the paper. The influence of PCE, naphthalene and phosphonamidite based superplasticizers and w/c ratio: 0.45, 0.50 and 0.55 on air-entrainment and consistency of fresh concrete mix was investigated. The research results indicated that with increasing w/c ratio the air-entrainment of concrete increases. Moreover, in case of an increase in the degree of liquidity of the air-entrained concrete made of participation of the innovative, air-entraining multi-component cement CEM II/B-V, first and new generation superplasticizers based on modified naphthalene, and then modified phosphonamidite should be used. PCE based superplasticizer cause the too high air-entrainment of concrete. The research results proved, that the porosity of hardened concrete meets the European standards for frost-resistant concrete.

Research of Steel Fiber Self-Compacting Concrete Frost Resistance

2012 ◽  
Vol 174-177 ◽  
pp. 721-725 ◽  
Author(s):  
Ming Bao Gao ◽  
Yan Ru Zhao ◽  
Xiao Yan He
Keyword(s):  
Elastic Modulus ◽  
Frost Resistance ◽  
Steel Fiber ◽  
Concrete Specimen ◽  
Test Method ◽  
Dynamic Elastic Modulus ◽  
Self Compacting Concrete ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

With the fast freeze-thaw test method, the c50 steel fiber self-compacting concrete was carried out 300 tests of freeze-thaw cycle. In the process of freeze-thaw cycles, it determined by the quality of the concrete specimen, dynamic elastic modulus and strength, and analyzed the steel fibers and their different contents on frost resistance of self-compacting concrete impact. The results showed that: steel fiber self-compacting concrete in freeze-thaw cycle can play constrained role in the quality loss, dynamic elastic modulus and intensity, and can significantly improve the self-compacting concrete frost resistance. Within a certain range, the more steel fiber, the stronger of frost resistance.

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