The effect of aggregate aspect ratio and temperature on the fracture toughness of a low cement refractory concrete

Prata, Laura Brum; Libardi, W.; Baldo, J. B.

doi:10.1590/s1516-14392003000400021

Cited by 6 publications

(8 citation statements)

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“…Castable is composed basically of two phases: a matrix phase containing hydraulic mineral plus fine refractory aggregates, and a dispersed phase consisting of coarse and medium refractory aggregates (Prata, Libardi and Baldo, 2003;ACI, 2013). As shown in Figure 2, hydraulic mineral in the CT is calcium aluminate (CA) while gehlenite (CAS), mullite, corundum and calcite (limestone) are the aggregate.…”

Section: Figure 1 Ucs Test Apparatus and Its Samplementioning

confidence: 99%

Cement material development used for cementing underground coal gasification well

Huda

2018

IMJ

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The R&D Centre for Mineral and Coal Technology of the Ministry of Energy and Mineral Resources develops an underground coal gasification (UCG) technology including its UCG test in a coal mine at Musi Banyuasin regency, South Sumatra. The UCG is safer than the underground mine since there is no worker underground however there is a concern in risk of ground water pollution. One of the methods to reduce the risk is a proper installation of well casing and cementing that seal aquifer from contact with UCG product gas. Development of special cement for cementing UCG well is needed due to its high process temperature (up to 1300°C). The objective of this research is to develop a cement material that can withstand high temperatures environment. Domestically available an oil well cement (OWC) and a castables (CT) were used for the experiments. Single material of OWC is not suitable for cementing UCG well since the OWC compressive strength reduced drastically at heat treatment above 300°C due to decomposition of portlandite and calcium silicate hydrate. On the other hand, there was a synergistic effect that resulted of higher compressive strength sample if 60% weight of OWC and 40% weight of CT was blended. The absence of portlandite and the presence of inert filler materials in the blend is believed to improve thermal and mechanical properties of the blend. ABSTRAKPusat Penelitian dan Pengembangan Mineral dan Batubara, Kementerian Energi dan Sumber Daya Mineral sedang mengembangkan teknologi gasifikasi batubara bawah tanah (underground coal gasification/UCG) dan telah melakukan uji coba UCG di sebuah tambang batu bara di Musi Banyuasin, Sumatera Selatan. UCG lebih aman dibandingkan tambang bawah tanah karena tidak ada pekerja yang berada di bawah tanah tetapi ada resiko polusi air tanah akibat kegiatan UCG. Pemasangan casing dan penyemenan sumur akan mengurangi resiko tersebut tetapi karena proses UCG melibatkan suhu hingga 1300°C maka pengembangan semen yang tahan suhu tinggi untuk penyemenan sumur UCG perlu dikembangkan. Tujuan penelitian ini adalah mengembangkan bahan semen tahan suhu tinggi. Semen sumur minyak (oil well cement/OWC) dan castables (CT) yang dapat diperoleh di dalam negeri digunakan sebagai bahan penelitian. Hasil penelitian menunjukkan OWC kurang sesuai untuk penyemenan sumur UCG karena kuat tekannya menurun secara drastis pada suhu di atas 300°C. Hal ini terjadi karena awa-komposisi portlandit dan kalsium silikat hidrat pada suhu tersebut. Di lain pihak terjadi sinergi hasil blending 60% berat OWC dan 40% berat CT pada suhu perlakuan panas di atas 300 o C yang menghasilkan kuat tekan sampel lebih tinggi dibandingkan kuat tekan sampel OWC atau CT saja. Tidak adanya portlandit dan adanya bahan pengisi dalam campuran tersebut diperkirakan menjadi sebab terjadinya peningkatan kuat tekan semen hasil blending. Kata kunci: gasifikasi batubara bawah tanah, semen sumur minyak, castables, perlakuan panas

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Section: Figure 1 Ucs Test Apparatus and Its Samplementioning

confidence: 99%

Cement material development used for cementing underground coal gasification well

Huda

2018

IMJ

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“…Such aggregates are dense (<3% open porosity) 1,2 and hard, bestowing the resulting refractory brick or castable with properties like resistance to thermal shock, wear, and shrinkage at high temperature and slag corrosion. Aggregates typically being the strongest phase (usually having high elastic modulus) can also deflect thermal shock or mechanically induced cracks improving the overall toughness of the product 3 . The other 30–40 wt% of the refractory composition is made up of small particles (<90 μm) comprising the matrix 1,4 .…”

Section: Introductionmentioning

confidence: 99%

Impact on aggregate/matrix bonding when a refractory contains zinc aluminate instead of spinel and magnesia‐chrome

2023

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The high hot strength of MgO–Cr2O3 refractory is often ascribed to its intimate aggregate/matrix bonding. For a fundamental comparison with it, ∼2 mm aggregates of MgO and Al2O3 were separately embedded in ZnAl2O4 and MgAl2O4 matrices, sintered at 1600°C, and examined. It was found that similarity of thermal expansion coefficient (TEC) between the aggregate and the matrix is critical to achieve good bonding and this is more important than the extent of interdiffusion. The TEC mismatch of ≥5.7 × 10−6 K−1 caused significant undesirable debonding in MgO aggregate/MgAl2O4 matrix sample and MgO/ZnAl2O4 despite >736 μm Zn2+ diffusion depth in the latter. Direct bonding, as inferred from a thicker interfacial reaction layer and a greater shift of the aggregate/matrix interface before and after firing, was better in MgAl2O4/ZnAl2O4 combination, followed by tabular Al2O3/ZnAl2O4 and Al2O3/MgAl2O4. Powder X‐ray diffraction indicated that the volatilization of ZnAl2O4 at 1600°C in air was negligible compared to MgO–Cr2O3.

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“…Brojne publikacije posvećene su ovoj oblasti ispitivanja vatrostalnog betona. [35][36][37][38] Ranije su kao sirovine za dobijanje vatrostalnih materijala korišćeni gotovo isključivo prirodni materijali. Danas se oni u velikoj meri zamenjuju veštački dobijenim materijalima (npr.…”

Section: Dostignuća I Tendencije U Oblasti Ispitivanja I Projektovanjunclassified

“…Početna čvrstoća K1 betona je neznatno veća od čvrstoće betona B1, što se može objasniti većom tvrdoćom korundnog agregata. Uticaj tvrdoće agregata na pritisnu čvrstoću betona se često nepravedno zanemaruje, ali činjenica je da agregat kao najtvrđa komponenta utiče na pritisnu čvrstoću betona [35] . Beton K3 ima značajno veću polaznu pritisnu čvrstoću u odnosu na ostale betone iz obe serije, što se može objasniti povoljnom kombinacijom više faktora: niskog vodo-cementnog faktora, primene agregata velike tvrdoće, pogodnog granulometrijskog sastava, adekvatnog veziva, uticaja aditiva silika praha na efikasno "pakovanje" čestica, male poroznosti, itd.…”

Section: čVrstoća Pri Pritisku Vatrostalnih Betonaunclassified

“…Iako se u literaturi [72] može naći podatak da se u boksitnom betonu formira veća količina mulita nego u korundnom, pritisna čvrstoća betona K3 je veća od pritisne čvrstoće B3. Razlozi za ovakva svojstva K3 mogu biti različiti: moguće je da se kod K3 formirala veća količina mulita ako je postojala veća količina nevezanog Al 2 O 3 zaostalog iz faznih transformacija koje su se odvile do 1400 ºC, tvrdoća korundnog agregata je veća od boksitnog, uglasti oblik zrna korunda omogućava bolje povezivanje istih pri zbijanju što materijalu obezbeđuje vrstu jakog "skeleta" [35] , poroznost betona K3 je manja nego B3, itd.…”

Section: čVrstoća Pri Pritisku Vatrostalnih Betonaunclassified

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Influence of microstructure on properties of refractory concretes

Terzić¹

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This dissertation is concerned with investigation of influence of microstructure on refractory concrete properties. Refractory concretes were designed on basis of following components: synthetic aggregates-corundum and bauxite, high-aluminate cement and admixtures. Main goal of the investigation is to find correlation between microstructure and the most important concrete properties such are: physical, mechanical, thermo-mechanical properties and parameters of sintering process. There is insignificant number of papers in accessible literature that are concerned with theme of effect which microstructure has on corundum and bauxite based refractory concretes. Two groups of refractory concretes were investigated: first group contained corundum as aggregate and second group contained bauxite as aggregate and chamotte as filler. Concrete design was modified with admixtures: Litopix and silica fume. Hardened concrete specimens were thermally treated at following temperatures: 110, 300, 800, 1000, 1300 and 1500 ο C. Afterwards, following properties were determined: bulk density, water absorption, apparent porosity, mechanical compressive and flexural strengths. Image Pro Plus program for image analysis was applied for determination of size and number of pores within concrete structure. Non-destructive investigation method (Ultrasonic Pulse Velocity technique) was used for determination of correlation between compressive strength and temperature, and also porosity and temperature. Refractoriness and refractoriness under load were investigated for both groups of concrete. Mechanism of sintering and rate of sintering process were investigated during secondary state creep. Phase composition of refractory concretes was investigated using XRD. Micro-structural changes on following temperatures: 110, 1000 and 1500 ο C were followed on SEM micro-photographs. Chemical composition of grains and cement matrix was determined with EDS. Investigation results showed that both corundum and bauxite based concrete can be used as lining of metallurgical plants, as well as other plants operating at high temperature. Corundum based concretes showed better properties than bauxite concretes. Properties of both groups of concrete were improved with application of admixtures. Silica fume decreased water-cement factor, improved "packing" of componential grains and enabled mullite formation at 1500 ºC. Silica fume, also, decreased porosity and increased mechanical flexural and compressive strength of both bauxite and corundum concretes. In case of bauxite concretes, silica fume increased refractoriness and refractoriness under load. Litopix stabilized concrete structure by which degradation of mechanical properties was prevented. Corundum concrete with silica fume as admixture showed highest thermo-mechanical, mechanical and thermal properties. This dissertation represents contribution in global investigation of phenomena of micro-structural formation and its influence on properties and performances of concrete subjected to high temperature. It i...

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The effect of aggregate aspect ratio and temperature on the fracture toughness of a low cement refractory concrete

Cited by 6 publications

References 5 publications

Cement material development used for cementing underground coal gasification well

Cement material development used for cementing underground coal gasification well

Impact on aggregate/matrix bonding when a refractory contains zinc aluminate instead of spinel and magnesia‐chrome

Influence of microstructure on properties of refractory concretes

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