Properties Of Refractory Concrete Research Articles

Investigation of the influence of granulometric composition of the aggregate and the content of the binder on the properties of refractory concrete

Depending on the additives used, refractory concretes acquire the necessary properties: fire resistance, porosity, heat resistance, maximum application temperature, etc. The influence of the granulometric composition of the mullite aggregate and the content of the binder (cement) on the properties of refractory concrete was evaluated. MLS-62 was used as a filler (the content of the determining component Al2O3 was more than 62%), and Secar 71 high-alumina cement was used as a binder. To test the samples obtained from different granulometric compositions, the mullite aggregate was sieved in fractions (–6+3) mm, –3 mm. In the developed compositions of refractory concrete, these fractions were mixed in different percentages:(–6+3)/(–3). The cement content in the compositions varied by weight: 15%, 20%, 25%. The study was carried out in the factory laboratory, where samples of refractories of all the compositions were made by vibration pressing method. The resulting samples were dried at 110 °C and fired. It was found that after drying, samples with a cement content of 25% had the highest strength indicators content of 25% was the best result in terms of strength and shrinkage. Studies of the impact of the granulometric composition of the charge on the physical properties of refractory concrete showed that the highest strength indicators were exhibited by samples of refractory concrete with a percentage of fractions in the aggregate of 40/60 and 20/80, as well as with the highest amount of cement content in the composition – 25%.After firing at 800oC and 1300oC, the strength of the samples decreases. It was shown that the reason of this phenomenon was softening, mainly associated with dehydration of the binder. The refractory concrete obtained with the use of aggregate with a fractional composition of 20/80 and a cement.

Influence of Various Factors on the Properties of Refractory Concrete

We present some results of investigations of the influence of various factors on the improvement of operating characteristics of refractory concrete. We describe the procedures of laboratory tests and their results in the investigation of the influence of different additives and moisture content on the properties of refractory concrete.

Material Properties of Refractory Concrete under High Temperature

The paper presents the validation of physical properties of refractory concrete with heavy filling, using the measurements under high temperature, assumed for the construction of a thermal storage. The whole system, consisting of the storage core and of the insulation container, is characterized by non-stationary thermal transfer, supplied from solar radiation into the core. The validation of behaviour of the system (including its sleeping state and the dynamics of charging and discharging) is needed for the optimization of its size parameters.

Influence of mechanical activation on curing processes of refractory concrete and its properties

Significant advantages of low-cement refractory concrete with low porosity, high mechanical strength, chemical resistance and thermal stability, and adaptability to the operating conditions in linings of thermal units determine the prospects for further increase in consumption of concrete and development of scientific bases of technology of its production. A promising method of creation of composite materials with an efficient structure and improved properties is the mechanical activation.We have studied the effect of the mechanical activation of electric corundum and a matrix component of low-cement corundum concrete on the change of the morphology and physical properties of materials, hardening kinetics and properties of the concrete. It was determined that an increase in the duration of the mechanical activation of electric corundum has a significant impact on the change of acid-base balance of suspensions, reactivity of the matrix component and the rate of hardening of a paste.The experimental research showed the possibility of use of the mechanical activation of components of the low-cement corundum concrete, as an effective way of directed control of activity of the matrix component, rate of cement hydration, formation of hydrogel and colloiding of cement phase, development of crystallization contacts between cement and aggregate particles that promote formation of an efficient structure and properties of refractory concrete.

High temperature processes of phase formation in the system «cement «Gorkal-70» — microsilica»

The use of microsilica in the refractory concrete on aluminates cement contributes to the formation of an effective structure and physico-mechanical properties of concrete in linings of thermal units. The features of high-temperature processes in the system calcium aluminates cement – and the formation of the crystalline and amorphous phases are determined by the ratio of components, their mineralogical and chemical composition. The article presents the results of studies of the physical and chemical processes occurring during the thermal heating of model mixtures of hydrated compositions cement« Gorkal-70 – mcrosilica. Using the differential thermal analysis and X-ray diffraction, we have studied the effect of low quality microsilica on the mechanism of phase formation and established the mineralizing effect of impurities on the formation of the crystalline and amorphous phases. The article shows the possibility of directional control of the synthesis of anorthite and gehlenite by varying the proportion of the components of the system cement« Gorkal-70 - microsilica, which affects the formation of a given structure and properties of refractory concrete.

Effect of different surfactants on the properties of alumosilicate concrete

Results are presented from comparison tests of different thinners-dispersants made by the companies “SKW Polimers GmbH” and “Alcoa” and the OOO “Poliplast.” The tests were performed under comparable conditions to determine how these additives affect the physico-ceramic properties of refractory concretes based on Chinese-produced sintered bauxite of grade Rota HD and high-alumina cement SA-270.

A REVIEW OF THE POSSIBLE APPLICATIONS OF NANOTECHNOLOGY IN REFRACTORY CONCRETE

This article reviews the manufacturing nanotechnologies of modern refractory concretes and some other cementitious materials. The main part of the article focuses on the results obtained by the authors who analyzed the application of nanotechnology for manufacturing refractory concretes and examined the influence of nanostructure formation in the binding material on the properties of refractory concretes. In one case, investigations were carried out using two‐component (sodium silicate solution mixed with dicalcium silicate) and three‐component (sodium silicate solution mixed with dicalcium silicate plus calcium aluminate cement) binding materials, whereas in other case, multi‐component material, middle cement refractory concrete with mullite aggregates, microsilica and additives of single and hybrid deflocculant (polycarboxylate ether Castament FS20 and sodium tripolyphosphate) were researched. Preliminary investigations showed that the three‐component binding material under development hardens unlike the two‐component material as one of the binding components (combination of sodium silicate solution and dicalcium silicate) hardens very fast and affects the hydration process of the other component, calcium aluminate cement, which has a powerful impact on the whole structure of the already hardened material. The limited amount of water in the hardening structure provides conditions for the formation of the initial nanoclusters and nanolayers of amorphous hydrates. The application of nanotechnology in manufacturing refractory concretes has enabled to increase compressive strength 3 times – from 55 MPa to 165 MPa. Santrauka Straipsnyje apžvelgiamos per pastaraji dešimtmeti sukurtos ugniai atspariu betonu ir kai kuriu kitu cementiniu medžiagu gamybos nanotechnologijos, kurios padeda nagrineti nanostruktūru, susidariusiu kietejant šiu betonu rišamajai medžiagai, itaka fizikinems betonu charakteristikoms. Detaliau apžvelgiami rezultatai, gauti šio straipsnio autoriu, nagrinejusiu nanotechnologiju taikyma ugniai atspariu betonu gamyboje tiriant nanostruktūru susidarymo, kietejant ugniai atspariu betonu rišamajai medžiagai bei ugniai atspariems betonams su mulito užpildu, itaka šiu medžiagu savybems. Autoriu tyrimai atlikti naudojant dvinkomponente (natrio silikato tirpalo ir dikalcio silikato) bei trikomponente (natrio silikato tirpalo, dikalcio silikato ir aliuminatinio cemento) rišamaja medžiaga bei vidutinio cemento kiekio ugniai atsparu betona su SiO2 mikrodulkiu ir hibridinio deflokulianto (natrio tripolifosfatu ir polikarboksilato eteriu) priedu. Preliminarūs tyrimai parode, kad trikomponentis rišiklis kieteja kitaip nei dvikomponentis, nes viena iš rišamuju daliu (natrio silikato tirpalo ir dikalcio silikato kompozicija) kieteja labai greitai ir veikia kito komponento (aliuminatinio cemento) hidratacijos eiga, o tai turi didele itaka visai kietejančiai struktūrai. Ribotas vandens kiekis kietejančioje struktūroje padeda šalia amorfiniu hidratu formuotis nanoklasteriams ir nanosluoksniams. Pritaikius nanotechnologija ugniai atspariu betonu gamyboje, pavyko gerokai padidinti ju termini atsparuma (beveik tris kartus) ir gniuždomaji stipri (nuo 55 MPa iki 165 MPa).

Elastic properties of refractory silica concretes

The authors have designed an ultrasonic experimental apparatus and developed a procedure for using it to investigate the elastic properties of refractory concretes at 20–1500°C.