1156 posts
Quality control Question 19
I want to know what is Roslin Ramler slope and characteristic value forcements? Do they have any relationships and how do you understand the fineness by using them.
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1156 posts
Re: Quality control
The Rosin-Rammler-Sperling-Bennett particle size distribution for cement is found by measuring the residue on various sieves (25,32,45,63,90 micronsetc.) Alternatively you can use laser granulometry or some other method of measuring the residues. You then plot the natural log of the sieve sizes on the x axis (ln(sieve)), against the double natural log of 100 divided by the residue on the y axis (ln(ln(100/Residue))). The reason for using these axes is that for fine powders such as cement the plot approximates to a straight line. The slope of the line gives a measure of the "tightness" of the particle size distribution and varies from 0.8 to 1.1 for cements, dependent on the type of equipment used for grinding. The characteristic grain size is the sieve size where 36.8 per cent of the cement would be retained. This can be calculated from the slope and intercept of the RRSB line and is typically between 20 and 30 microns for cement.
1156 posts
Quality control Question 20
We are currently using blast furnace slag as the only additive to our new product of masonry cement but we are failing to control the compressive strengths within the desired levels. We are getting on average 26MPa at seven days and we are add in 70 per cent slag. What’s the way forward and please tell me more about masonry cement as this a new area for me.
1156 posts
Re: Quality control
Masonry cement is usually made with Portland Cement clinker, gypsum, up to 30 per cent limestone addition and organic additives such as lignosulphonates to increase the workability of the mortar produced with the cement. High strength is not the property that is important with masonry cement. More important is high workability and adhesion to allow the mortar to bind masonry together or to be rendered onto the surface of masonry.