Mechanical Properties and Microstructural Investigation of Ultra-High Performance Glass Powder Concrete

Additive of glass powder was successfully utilized in ultra-high performance concrete (UHPC) mixture.During experiment was found, that glass powder can be used instead of silica fume (SF), without decrease of mechanical properties and microstructure can be significantly increased. In experiment 100 % of quartz powder was substituted by glass powder. Quantitative and qualitative XRD analysis revealed,that glass powder improves hydration of Portland cement and in such way additional compressive strength up to 40 MPa can be gained. Designed mixtures were blended with laboratory mixer Eirich R02T and later with industrial mixer HPGM 1125. In new UHPC mixture was incorporated different amount of steel fibres. Flexural strength was increased about 5 times from 6.7 MPa to 36.2 MPa

Complex admixtures for high-strength concrete

The influence of naphthalene formaldehyde superplasticizers (NFS), lignosulfonate plasticizers (LSP) and silica fume on cement paste properties and complex usage of these admixtures for high-strength concrete production are investigated in this research. These admixtures influence the cement hydration products morphology and properties of hardened cement paste. The degree of cement hydration and Ca(OH)2 content in hardened cement paste were determined for analysis of cement hydration process with admixtures. Mechanical properties and porosity of hardened cement paste with the admixtures were tested. Optimal dosages of plasticizing admixtures and silica fume were estimated and the most efficient method of silica fume adding to concrete mixture was proposed. The results of investigation have been used for high-strength concrete production. Frist Published Online: 30 Jul 201

Influence of Water to Cement Ratio with Different Amount of Binder on Properties of Ultra-High Performance Concrete

Four different composition of ultra-high performance concrete (UHPC) have been created for this study, while W/C ratio varied from 0.25 to 0.33. Amount of cement, quartz sand and super plasticizer has been maintained constant (at 735 kg/m3, 962 kg/m3 and 36.76 l respectively). As binder glass powder and silica fume were used. Optimal fines of glass powder were selected by Chapelle test. In experiment different combinations of silica fume, glass powder and quartz powder as microfiller were used. Compressive strength up to 160 MPa were obtained. The main aim of experiment was to create relationships between w/c ratio and compressive strength and to find optimal composition of UHPC. Slump, dynamic viscosity, density, and compressive strength test methods were used. In experiment glass powder were successfully utilized in UHPC and were obtained essential results for proper composition calculation

The influence of coarse aggregate concentration on the strength of concrete and on the porosity of concrete mortar/Stambiojo užpildo koncentracijos įtaka betono stiprumui ir skiedininės dalies poringumui

The results of experiments dealing with coarse aggregate concentration influence on the concrete strength and the structure of hardened cement paste and mortar of concrete are presented in the paper. Experiments were performed on concrete with dense coarse aggregate (crushed granite) which strength is more than strength of mortar and lightweight porous aggregate (expanded clay aggregate) with strength less than that of mortar. Physical and mechanical properties of concrete with dense coarse aggregate are presented in Table 1 and the concretes with the porous coarse aggregate in Table 2. The decrease of entrained air content with the increase of coarse aggregate concentration ϕσt were determined both for concretes with dense and porous coarse aggregate. The entrained air has a significant effect on concrete strength—1% of entrained air decreases the strength of concrete about 5% [11]. The influence of the coarse aggregate concentration on the compressive strength of concrete with the constant air content is presented in Figs 3 and 4. With the increase of coarse aggregate concentration the concrete strength decreases when the entrained air content in concrete is constant. The main reasons of the concrete strength reduction are the stress concentration and structural defects near the coarse aggregate. Coarse aggregate affects the structure of mortar. Dense coarse aggregate has negligible water absorption and does not change water content in mortar of concrete, and capillary porosity of mortar remains constant when the concentration of dense coarse aggregate ϕ st increases (Fig 5). Porous coarse aggregate (expanded clay aggregate) has large water absorption (more than 16%), therefore water content in mortar of concrete is reduced and capillary porosity of mortar is significantly reduced when the concentration of porous coarse aggregate ϕ st increases (Fig 5). The entrained air content in mortar with both dense and porous coarse aggregate decreases inverse proportionally to coarse aggregate concentration ϕ st (Fig 6). The investigations have shown that suitable selection of properties and volumetric concentration of coarse aggregate can reduce stress concentration in concrete and increase the concrete strength. First Published Online: 30 Jul 201

Preconditions for the application of petrašiūnai quarry dolomite screenings and dolomite powder in conventional and self-compacting concrete mixes

The objective of these experimental studies is to evaluate (verify) the possibility of applying by-products (0/2 mm fraction dolomite screenings or dolomite powder) obtained in the process of producing crushed dolomite from Petrašiūnai dolomite quarry rocks in concrete technology. A rational application of this material expands the range of concrete mix aggregates and provides an integrated use of dolomite rock by consuming less attractive by-products of dolomite processing. The article discusses the possibilities of using the above introduced dolomite by-products in concrete applications and gives a preliminary assessment of physical, mechanical and technological characteristics of commercial and technological concrete with dolomite screenings. 0/2 mm fraction dolomite screenings from Petrašiūnai dolomite quarry with an average density of 2600 kg/m3, a bulk density of 1690 kg/m3, a bulk porosity of 39.1%, fine particle content (contamination with dust and clay particles) of < 4,9%, a specific surface of 1085 cm2/g determined by Blaine tester were used for experimental study. The physicalcharacteristics of dolomite powder and dolomite screenings additionally crushed in a lab ball mill were similar: an average density of 2600 kg/m3, a bulk density of 1210 kg/m3, a bulk porosity of 53,5% and a specific surface after additional milling of 3030 cm2/g and 4070…4200 cm2/g respectively. Dolomite particles have a rough, conchoidal and porous surface, however, their form is close to cubic or even oval while their edges are less sharp (mechanically grated) compared to granite or other crushed stone screenings. Therefore, dolomite particles bond very well with cement stone and almost do not increase water demand for producing a paste of normal consistency and do not weaken the rheological properties of the mixes. Dolomite screenings or dolomite powder from Petrašiūnai quarry have stable mineral composition, but the XRD patterns of rock provide little information: although dolomite peaks are prevailing, quartz and feldspar peaks can also be noticeable. Moreover, ferrous minerals (pyrite, limonite) are present in dolomite, nevertheless, so few particles of these impurities are so small (< 0.2 mm in diameter) that they pose no risk of the potential destruction of concrete. Energy consumption of crushing dolomite screenings to reach the fineness of cement particles is much lower compared to crushing granite screenings. The crushed granite screenings are 1.5–2 times finer compared to the fineness of dolomite screenings crushed for the same time. Besides, the fineness of carbonate rock powder can be easily adjusted by changing crushing time. Therefore, dolomite screenings is a very perspective raw material for producing concrete micro-aggregates. No pozzolanic behaviour of dolomite screenings and dolomite powder during the short-term curing of cement stone or concrete under normal (room) temperature conditions were observed, and therefore a rational application of these mineral admixtures in conventional concretes would be only as substitutes for fine aggregate (sand) and only partly for cement. Most probably, dolomite powder can behave as a weak pozzolanic admixture at higher temperatures (above 50 oC); however more detailed studies are required to prove this supposition. The powdered dolomite admixture does not increase water demand for obtaining the paste of normal consistency but improves the structure of cement stone pores and frost resistance. The crushed dolomite screenings reduce the compressive and bending strength of concrete cured under ordinary temperature conditions; however, a small content of these admixtures (up to 15 ÷ 20 per cent of cement mass) can be recommended for self-compacting concrete and other fine-grained concrete mixes because the deterioration of the mechanical characteristics of cement stone is insignificant, i.e. about 10 ÷ 12 per cent. Dolomite screenings substituting for sand (or a part of sand) in conventional Portland cement concrete improve the granular composition of the mix, increase the content of fine (0.063 ÷ 0.25 mm) fractions and grow in the compressive strength of such concrete by 12 per cent. Such concrete has a better structure dominated by closed pores. Therefore, fine aggregate from dolomite screenings (or with them) is recommended for Portland cement mixes or cement grouts. Petrašiūnų dolomito atsijų ir dolomitmilčių tinkamumo įprastinio sunkiojo ir susitankinančio betono mišiniuose prielaidos Santrauka Šių eksperimentinių tyrimų tikslas – įvertinti šalutinio dolomito uolienos perdirbimo produkto 0/2 mm frakcijos atsijų ir jų malinio, vadinamo dolomitmilčiais, naudojimo galimybes betono technologijoje.Straipsnyje aptariamos įvardytų produktų iš dolomito naudojimo betono mišinyje prielaidos ir įvertinamos fizikinės, mechaninės bei technologinės prekinio ir technologinio betono su dolomito atsijomis savybės. Dolomito atsijų ir dolomitmilčių pucolaninės savybės per trumpalaikį cementinio akmens ar betono kietėjimo laikotarpį normalioje (kambario) temperatūroje nepasireiškė, todėl šiuos mineralinius priedus racionalu naudoti įprastiniuose betonuose tik kaip smulkaus užpildo (smėlio) ir iš dalies cemento pakaitalą. Maltų dolomito atsijų priedas nepadidina vandens kiekio normalaus tirštumo tešlai gauti, pagerina cementinio akmens porų struktūrą ir jo atsparumą šalčiui. Maltos dolomito atsijos sumažina įprastinėje temperatūroje kietėjusio cementinio akmens gniuždomąjį ir lenkiamąjį stiprį, tačiau nedidelis jų kiekis (iki 15–20 proc. cemento masės) gali būti rekomenduojamas susitankinančio ir kitokio smulkiagrūdžio betono mišinyje, nes cementinio akmens mechaninės savybės sumažėja šiuo atveju nedaug – apie 10–12 proc. First Published Online: 16 May 2013 Reikšminiai žodžiai: dolomitas, Petrašiūnų karjeras, dolomito atsijos, dolomitmilčiai, pucolaninis aktyvumas,betonas, smulkus užpildas, gniuždomasis stipri

Strengthening of foundation of Church of Holy Cross-discovery in Laukuva

The article discusses the underpinning works of the Laukuva Holy Christ Discovery Church. This church is a sacral building of the period of Romanticism, for the construction of which a peculiar bricklaying technique characteristic of architecture of the Lithuanian Romanticism was used. Stone masonry construction was popular at that time not only because it was cheap, but also because it was used as an artistic means of construction. Succeeding generations attempted to eliminate certain drawbacks of this style, which were mainly caused by the insufficient hydraulic properties of lime and disability of lime solutions to resist to climate impact. The cracks which emerged in the church of Laukuva were filled in with a concrete solution. Visual evaluation of samples of lime solutions allows assuming that the Laukuva Church constructors of the 19th century made a mistake characteristic of constructors of previous historical periods, i.e. they used a “thick” solution and a rather inert filling. The probing of the condition of the foundation demonstrated that the foundation of the church was based on the wooden grate, which rotted. It was noticed that the lime solution cementing the stones of the foundation was very shaky. Having identified the cause of the deformations of the buildings, it became clear that first of all it is necessary to strengthen the foundations laid with boulders. The shaky conditions of the foundation made it impossible to use concrete vibrators. Constructors had to prepare a rather high-flow concrete mix, which could be thickened manually. Expectations are that the plastic and stable concrete mix used to strengthen the foundation of the Church of Laukuva will determine its durability

Modifying the composition of hollow-core slab concrete

The questions of the extruded concrete composition and the possibilities of modifying it are very important for the technology for the extruded concrete. The gained experience of working with the extruders of hollow core slabs shows that the operators of such equipment frequently choose an improper strategy for the production process. The main drawbacks are as follows: a) the use of fairly stiff mixture that is far above the necessary Vebe consistency class V2 for this technology; b) the over saturation of the mixture with coarse aggregates which determines a low compaction factor of the mixture; c) the rejection of using concrete admixtures which causes equipment overloads or led to its exploitation in the limitary conditions. Besides, the experience of using extruders proves that all parameters predicted by standards and other norms (for example, concrete strength class C40/50 or C50/60 including water cement ratio W/C<0,45) are obtainable without large efforts. Therefore, the main criteria for the suitability of such concrete modifi cation have rather technological character including the lowest energy consumption during shaping and the compaction of the semi manufacture of the reinforced article as well as the highest structural strength or stability of the fresh concrete slab. Whereas the mechanical properties (mainly strength) of such hardened concrete are mostly within acceptable values, it cannot be treated as the main criterion for optimizing the extruded concrete composition. Extruded concrete compositions used for producing hollow-core slab were chosen for technological and laboratory scale investigations. The amount of Portland cement in the concrete mixture was 335…370 kg/m3, sand made 0/2 mm grade – 330…440kg/m3 and 0/4 mm grade – 680…510 kg/m3; the amount of coarse aggregates 200…325 kg/m3 and 755…825 kg/m3 for grades 2/8 mm and 11/16 mm respectively; W/C ratio 0,34…0,39. The crushing strength of the extruded concrete was within 57…68 MPa and more (the results of technological trials). The character of the structure and the compaction level of the extruded mixture are the indicators of its technological suitability. Adding common lignosulfonate-based plasticizer (up to 1% of the cement mass) or a very small dose (0,2…0,3%) of the new generation super plasticizer with or without air entrainment agent could improve the structural and technological properties of such concrete. The experience obtained during laboratory scale investigations and on trials for the manufacturing lines of hollow core slabs shows that the main cause of such improvements is a better dispersion of cement particles in the stiff concrete mixture while the cohesion of the mixture of the freshly extruded article rests near unchanged. The effectiveness of such improvement was proven within the process of observing the level of the consumption of compaction energy – it was registered by the control console of extruders. After improvements in the concrete mixture were carried out, the consumption of compaction energy was reduced by 20…25 %. Investigations into concrete cores drilled-out from the hardened articles prove the apparently better structure of the modifi ed concrete while concrete strength and other physical properties rests rather unchanged (if the mixture W/C ratio rests unchanged). Improvements to concrete structure manifests by the absence of ‘air pockets’ (large pores of irregular form, air gaps trapped during mixture extrusion and compaction), more gradually distributed and comparatively small pores, the absence of internal concrete structure zones with cleft aggregates and loose sand particles and evenly coloured concrete (which proves a very good distribution of cement particles). The use of an air entrainment agent in the stiff concrete mixture allows reducing the dose of the plasticizer (super plasticizer) and reduces the density and crushing strength of the extruded concrete. Such was negligible during investigation and technological trials (up to 1,5 % of concrete density and about 3 % of strength), it was concluded that the air entrainment agent could be used in the extruded concrete for articles the exploitation conditions of which are severe, for example, for class XF2 etc. Tuštymėtųjų perdangos plokščių betono sudėties modifikavimas Santrauka Straipsnyje aptariami ekstruziniu būdu formuojamų gelžbetoninių gaminių (tuštymėtųjų plokščių) betono sudėties parinkimo ir modifi kavimo klausimai, susiję su formavimo įrangą tausojančio darbo režimo taikymu (didelių energinių sąnaudų nereikalaujančiu betono mišinio sutankinimu, tuo pat metu išlaikant ekstruziniam formavimui būtiną mišinio koheziją) ir optimalios betono struktūros gavimo aspektais. Laboratoriniais tyrimais ir gamybiniais bandymais bei pagal specialią metodiką išpjautų betono kernų savybių tyrimais įrodyta, kad tinkamai modifi kavus ekstruzinio betono sudėtį, įmanoma išlaikyti visus šiems gelžbetoniniams gaminiams reikalaujamus betono parametrus: betono mišinio standumo (Vebe) klasę V2, betono gniuždomojo stiprio klases C40/50 ir C50/60, esant mažam V/C ir taupiai naudojant portlandcementį (330–360 kg/m3). Be to, gaunama tanki ir vienodai sutankinta betono struktūra. Toks modifi kavimas susijęs su stambiųjų ir smulkiųjų betono užpildų santykio parinkimu ir plastiklių (superplastiklių) naudojimu mišinyje. Įrodyta, kad nedidelio kiekio orą įtraukiančių įmaišų naudojimas standžiame betono mišinyje leidžia formuoti konstrukcijas, kurios gali būti eksploatuojamos agresyvesnėmis aplinkos poveikio sąlygomis (pvz., XD3 ir XF2). First Published Online: 16 May 2013 Reikšminiai žodžiai: ekstruderis, tuštymėtosios plokštės, Vebe konsistencija, betono mišinys, V/C santykis, plastiklis, betono kernai, poro

Blended Cements Produced With Synthetic Zeolite Made from Industrial By-Product

Zeolites are appropriate supplementary cementitious materials in cement and concrete industry. In the present work synthetic zeolites was used like supplementary material in hardened cement paste and some properties as well as its influence on Portland cement hydration was determinate. X-ray powder diffraction, scanning electronic microscopy and energy-dispersive X-ray spectroscopy, FTIR spectroscopy were used as investigation methods. The compressive strength of hardened cement paste was measured at day 3, 28 and 60. The instrumental analysis showed that zeolite A(Na) dominates and unreacted Al(OH)3 remains in investigated synthetics zeolites, made from thermal and mechanical treated AlF3 production waste. The Chapelle test showed that both zeolites have good pozzolanic properties. The samples compressive strength remained close to the control samples compressive strength, reducing the amount of Portland cement, i.e., changing it by zeolite. After 60 days, the compressive strength was the best in the samples where 5% of Portland cement was replaced by the 2-zeolite. The compressive strength of the samples increased by 9 % compared with control samples. This research provides a real opportunity to save cement thus disposing the waste.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5635</p

The utilization of biomass bottom ashes in cement system

AB „Lifosa“Kauno technologijos universitetasVytauto Didžiojo universitetasŽemės ūkio akademij