Page 13 - Minutes of Proceedings of Civil Engineers Vol CXCV 1913-14 Part 3 Correspondence

1:18 coIrRESpoNDENcri oN THE coNSTRUcrtoN oF fMiuures ol Mr.coulchcr. Mr', C. l!. ll. Cour,cul:n wil,s especinlly interested in thr.l tvolk exe- cutetl below wl,tol irt berths Nos, 47r48, and 49. The uprvrrd slopo given to tho herutler fa,cing-blocks wns ingenious and ensur.od the bed beitrg prupelly fillcd with mrrss-concrete herrting. lle preferred to rrso tlippirrg lngs for dcpositing concrete to f<-rlrn thr: foundations f<-rr lrlock work, whcle such foundations were less thtrr l5 inches in rlopth. It rvls usurrl to hang four. or six bl,gs-rrccolding to the rvirlth of tlre foundltion-in rr row olr il berm, l,rrrl if the divels wero expelicrrccd rnen thoy were able to rnrtke a sound job, lc:r,virrg tr, sulfrce only slightly inferior to thrt of similnr rvor'l< c:rrlictl orrt irr the dly. He had found that usurrlly, antl especirr,lly iu tloop rvater, thc concrete depositetl from skips folured humps :r,nd lrollorvs, tnd rvhen these were screeded level the result wls sellom s:rbisf:rctory. A run of only 500 feet from the mixer on a nlore ol' Icss lough load was often sufticient, to cause the concrete to stifl'en irr tho skip, and to be discharged in lumps. Deep water was l,rrotlrct cnuse tending to stiffen concl.ete, and souretimes irr 35 or 40 foot of wrter it miglrt be found that the concrcte had conro awry florrr tho skip in a single cube the size of the skip. When this occut'retl it should be left untouched and it rvoultl crumble grrrdul.lly itrto trr oldinrr,ry heap. To ensure the best results in deep lvater it rrppooled to be nocessary to mix the concrete on the site as quickly rrs lxrssible rr,nd to tleposit it without l,ny delay, rw 5 minutes rnight bo srrlliciont to cause the concrete to stiff'en as described abovc. It wl,s ouscntiu,l tllrt, only tripping bags of rrpproved design should lxr usorl, othorrvisr: the concrete might hang in them and hrr"ve to be sclryorl out, to the detriment, of the work. tr'or some years he had usotl n, lrrrg dosignod by himself nnd shown in lig.l9 (p. 129). Thc spocinl fcrltttro rvts the iron ring about 15 inches in diameter', insteacl of tho usurrl strriglrt bar', to lvhich the cilnvil,s btg rvns sewn. After tho lrr,g luul beorr {illed, a flap of c&nvas was t,ucked over the top to l)r'(!r{orvo tlro c<-rncleto from wrsh while being lowered through the rvrutor to tlro rlivers. These bags ensured the discharge of the cotrct'oto with purcticllly no loss of cement, and very reliable wor.k coultl bo tlorro rvil,lr thenr. With regnrd to the cement .. settlings " nrotrtiotrotl lry tho Arrthor, he believed that the greater part of thoso rrrrnu frorrr tlre concr.ete while it was actually being dis- t:lurrgorl frorrr tllr skip ; ancl that, the amount of cement wtr,shetl frrrur tho ilrp of tlur skip, while it was being lowered through the wrlttu', wrw irivirrl n,rrrl rllircted only the top inch or so of properly- ! rrrixtr