Question

Lightweight Aggregate Production

1-how much of the materials should be melted at the sintering temperature selected in light aggregate production(what extent should the melting minerals?(feldspars etc.), how many of them protected their solid structures(water should not exceed)) What should these values be for minimum grain density and maximum compressive strength? Which materials can be used in this sense? how lightness and strength are affected when flying ash is used?

2-What should be optimum aggregate diameter in lightweight aggregate production? how the strength is affected when the size increases? how grain density is affected when the size increases?Why is that?According to which standard to lightweight aggregate strength test?

3-What is the effect of sintering time and temperature in light aggregate production

4-What should be the most appropriate drying process in light aggregate production?Why is that? Provide information on changes in light aggregate with drying(volume,strength etc.)

Answer 1

1-There are two sources to get the Light Weight Concrete(LWC) first one is naturally occuring LWC and second one ,it can be manufactured in the plant.For the artificial production of the light weight concrete the raw material such as pumic,shale,feldspars and others are heated and converted into the solid mass without liqufaction.and when the moisture is removed from the slurry of the raw material it is said to be the SINTERS .For the production of the light weight concrete it is suggested that the preheating tempreture should be 400 °C for half an hour and then sintering tempreture should be 1150°C ,only for one fourth of an hour.The given tempreture for the smelting of the minerals is adequate for the maximum compressive strength of the Light Weight Concrete.The LWC density is almost 0.70g/cc so this imply that the raw materials or minerals should be protected in maiting their solid structure.By this way the LWC is produced with the compressive strength of almost 11MPA .The effect of flyash is variable primarily but for log period it put a positive impact in the compressive strength of the LWC.Simultaneously use of fly ash derives a positive impact in maitaing the light weight of LWC so over all it has been observe that addition of Fly Ash is always benificial in reducing the weight and in achieving the high strength of LWC.

2-The diameter of light weight coarse aggregate is more than 5mm and diameter of light weight fine aggregate is less than 5mm so this is obvious that the optimum diameter of the light weight aggregate should be 5mm.The strength of fine light weight concrete is almost 2% more than the strength of coarse aggregate,the reason behind this is the density sice fine aggregate have the high density because of less availability of space among the aggregate and these could be compacted well to achieve high strength in comparison to coarse light weight aggregate.The increase in the size of aggregate leads to decrease in the density because of more air holding capicity .For the Test of Light weight aggregate concrete various methods and standard used depending on the country but they give almost similar values but the globally accepted standard for testing of light weight aggregate concrete is ASTM330/330M.