Chemical Analysis of Magnesia and Magnesia-Alumina Refractory Materials——Gravimetric method for determination of loss on ignition

1 Scope This standard specifies the gravimetric method for determination of loss on ignition.

Preparation of Magnesia Insulation Materials by Walnut Shell Powder Impregnated with Silica Sol

In order to reduce the thermal energy loss of high temperature kilns and furnaces and lower the surface temperature of the kiln body,magnesia insulation materials were prepared using self-made magnesia porous aggregates(using high purity magnesia powder as starting material and potassium oleate as the foaming agent),middle grade magnesia powder,calcium aluminate cement,and SiO_(2) micropowder as starting materials,introducing walnut shell powder impregnated with silica sol(short for Sws)as a pore-forming agent.The effects of the Sws addition(0,10%,15%,and 20%,by mass)and the sintering temperature(1300,1350,1400,and 1480℃)on the properties of magnesia insulation materials were studied.The results show that(1)for the specimens fired at 1480℃,when the Sws addition is 10%,the cold compressive strength is 22 MPa;when the Sws addition is 20%,the thermal conductivity is 0.368 W·m^(-1)·K^(-1)(350℃);(2)nano-silica in the silica sol reacts with MgO in the matrix to form forsterite,which encapsulates the pores volatilized from the walnut shell powder and forms closed pores.

Effect of Hot Environment on Strength and Heat Transfer Coefficient of Nano-Clay Concrete Paper Title

This study selected water-cement ratio 0.5 and slump 16 cm for ACI mix design, and used nano- clay to replace 0.1%, 0.3% and 0.5% of cement by weight to make cylinder and angle column specimens. The effects of different high temperatures on the compressive strength and heat transfer coefficient were tested, and the ignition loss of nano-clay cement paste was measured. The results showed that an appropriate replacement of nano-clay for 0.3% - 0.5% of cement can enhance the strength and heat transfer coefficient of concrete, especially 0.3% replacement. The 0.1% nano- clay replacement for cement reduces the strength and heat transfer coefficient of concrete. When the ambient temperature exceeds 300?C, the nano-clay concrete strength begins to decline, and the heat transfer coefficient decreases greatly, the effect of hot environment on the strength trend of nano-clay concrete is similar to that on normal concrete. When the nano-clay replaces cement by 0% - 0.5%, the ignition loss is approximately in exponential and logarithmic relationships to the compressive strength respectively when the ignition loss is smaller than and greater than 6%.

Typhoon events recorded in coastal lagoon deposits,southeastern Hainan Island

Coastal lagoon deposits provide evidence for the magnitude and frequency of past tropical cyclones prior to instrumental records and historical documentation.In the present study,we attempt to analyze the sedimentary records containing typhoon information for the northern South China Sea region.For this purpose,sediment cores were collected from two coastal lagoons in the southeastern Hainan Island,and were analyzed in laboratory to derive the data sets about grain size,organic and inorganic carbon contents,and deposition rates.The grain size and organic-inorganic carbon data were used to formulate the proxies of typhoon events.The deposition rates,as calculated using the CRS 210 Pb method,are around 0.5 mm/a for both lagoons,on the basis of which an age model is established.Within the cores,sedimentary layers associated with 35 typhoon events have been identified.On such a basis,a 350 year history of local typhoon activities is reconstructed by incorporating the 210 Pb dating results,typhoon-induced sedimentation patterns and the historical documents.A comparison of the frequency of typhoon occurrence with the regional climate records indicates that the observed changes in tropical cyclone activity patterns,as revealed by the lagoon sedimentary records,may be related to El Ni？o,Pacific Decadal Oscillation（PDO）,North Atlantic Oscillation（NAO）,sunspot,and other potential climate drivers that affect the tropical cyclone variability.This study demonstrates that the sedimentary record of storms can be analyzed in combination with historical documents,to provide meaningful information on past storm activities and their long-term variability.

The Effect of Fly Ash Quality on the Engineering Properties of High-Performance Concrete

Fly ash is the most inexpensive cementitious material,and its presence in concrete has increased in recent years because it has become more durable and environmentally friendly.This study examines densified mixture concrete and the effect of fly ash quality on high-flow,high-strength concrete.Tests show that when the same mixture achieves identical flow standards(slump >250 mm;slump flow >600 mm),the fly ash quality affects the nature of the concrete;additionally,and adding Class F fly ash to concrete(loss on ignition=6%)is more workable than adding Class C fly ash(loss on ignition=3%).However,adding fly ash with a high loss on ignition(9%)to concrete requires a substantial increase in the mixing water and a dose of superplasticizer to achieve the required workability.This reduces the quality of the concrete,which subsequently deteriorates its safety and durability.

Non-standard tests for process control in chemically bonded sands

Chemically bonded sand cores and molds are more commonly referred to as precision sand systems in the high production automotive powertrain sector. Their behavior in contact with molten metal can lead to casting defects. Consequently, the interaction is of great interest and an important part of metal casting technology. The American Foundry Society(AFS) sand testing is based on physical, mechanical, thermal and chemical properties of the sand system. Foundry engineers have long known that certain AFS sand tests provide limited information regarding control of molding and casting quality. The inadequacy is due to the fact that sand casting processes are inherently thermo-mechanical, thermo-chemical and thermo-physical. Non-standard foundry sand testing has proven useful for laboratory measurement of these characteristics in foundry sand using a disc-shaped specimen. Similarly, the equivalent disc-shaped specimens are used for casting trials. In order to accomplish near-net-shape casting with minimal defects, it is necessary to understand both the properties of the sand system, as well as the interface of molten metal when different binders, additives and/or refractory coatings are used. The methodology for the following non-standard chemically bonded sand tests is described:(1) disc transverse;(2) impact;(3) modified permeability;(4) abrasion;(5) thermal distortion;(6) quick loss on ignition. The data related to the non-standard sand tests were analyzed and interpreted. The test results indicate that there is relatively lower test-to-test variability with the disc-shaped specimens. The non-standard tests were able to discriminate between the chemically bonded polyurethane cold box sand specimens. Further studies should be conducted on various other sand and binder systems as well as on different specimen thicknesses.