The grading and shape of commercial sizes of aggregates

✍ Scribed by Markwick, A. H. D.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1942
• Weight: 708 KB
• Volume: 61
• Category: Article
• ISSN: 0368-4075
• DOI: 10.1002/jctb.5000610601

✦ Synopsis

In ronncsioii with tlir mvision of tltc 13ritisl1 Stntitlnnl Speifiiation for *' Sires of Itoiiildonc iirirl Vliippittgs " (13.S. 09-1339) n strtdg IIIIII ticen ninclo of conmerciiil sizcs of ngbm,qntee, with tho principnl olijert-of selecting tolrriinces for grnding niid slinlm, wliich sliould m r y cotisixtently with size.

Since tlic 13.S. sioves &tl in ninking sieve nnnIyfics bcnr no cmstilnt rntio to ciicli otlier, it itns first nccesvlry to cxprcse tho Him clistribntioli imlc~iciidciitly of Llicsu sieves.. Closer strnly of the sizo clisttibritiort HIIOWII tlint i t is n ~i i i n i ~i e t ~ tIistriIiution siinilnr to tho '' norninl " distrihi-' tioti of stntistics, nnrl p i i n bo coniplotely clcfincct IIJ' the nienn sin? nnd IIIU stiindiird tlerintion of tho clistribntioti. Tlio degree of concentnition of tliu size distribution nboiit tho n~eiiii size, or tltc closcness of the griidirig, m n IJO convenicntly oxpmssed by the mtio nicnn Rize/stnntlnrd tlevintion. wliicli is indopcntlent of tho nizo of tlidnggregnte. This form ofclistrilnitiurl is sliown to ntiso from tlic screening proeesRR. Esiiinhintion of tlic grnding nnrI d t n p of mnuy conimercinI nnnlpIcs alio\ss tlmt n Iirogccsivo rcdriction osiets in tho averago clowncsx of grriiling in tlio snlnllcr sizes, Tlicso sizes ntso coiitnin 011 the iivcriifie II grcnter proportion of flnky nnd clongntcd niiiterinl. Tho closeness of tltc grntIings.alacifiet1 in 1j.S. ~X&-lWdu is thcmforo progwwicely r c c l i i ~~c l nn tlrc noniiniil xizo of stono becon~cs rii~nllor, nnil tlic pcrtnittetl tolcrnnccn on elongntcd ninteriiil nre incrcnsetl in tho sninllcr nonlitinl aims of stone. In spitc of tlic fnct tlint the present tolernncrs nm less xtringent tlitin tllosc of tho prctioirs two nlitions, wry mnny cotr~ttiorriril ninterinls ~voitlil not Iiic\*u eonipliccl with tlie nmentled specificntioti, nntl a gencrnl itnprovetaent nppcrirs to bo dcsirnMo in comniercinl sizes of nggrcgntcs na regnrtlx botli grntling iinrl slinp.

Aggregates iuny lie innrketcd in one of soveriil forius : (1) 11s criishcr-run or riui-of-pit iiinteriiil (all-iii btilltist) ; (2) 11s coitcrctc iiggrrgiitcs iii nlticli the sizes will vnry froiii, my, 1) iii. or 9 iii. tlowiwiirds to j0. in. ; (3) in rnrious coiiiiiicrcinl sizes or '* gnuges " wlicre, hy siiitiiblc screeiiiitg, the riuigc of sizes is rcst.rictetl ns fnr ns is picticnlile to the noriiiuul s k o ; (4) its itiistures of ii ~i u i ~~l i c r of coirinicrcinl sizes coiiiliiiirtl in sliecifietl ,proliortioiis to the reqiiireiiietits of the custotiier.

This ~i i i ~) c r tlcscribes iiivest,igiitioits iriiide to iissiut the C'oniiiiittee rcs~ioiisil~le for the rcceitt rcyisioii of t,lie British Stiitidrirtl Spccificrit ioii goreriiiiiy the griidiiig iiiitl sliiipe of conuncrciiil sizes of roatlstoiie * ~'cuivii Coprrigli t tworsotl. Fia. 1 Diatrihtioir o/ aire in a aunsple of $-in. gruiiite large iiiiiiilior of siilisizcs, the coiititiuoils Iiutiiltetl tlist,riltutioti ciicve tilttiriiied \voiiltl 11s t lie true size tliatriliiitioii iti tlio itiritcriiil. The itoiiiiniil cotnttierciril size of the ,iiiiitcriill is tlefiiietl by tho suiiillest, size of I M . t h o tlint will retiiiii iiot wore tliuri 15% of tlie sriiii~~le, iitiil it will tic seeit to t1ifti.r coiisitlernlily from tlio iiieaii size. n OF Cu,\i.w:nri.u, SIZE+ IJP Ac;t:iwt:.crw I.llllle. Ill42