Looking Back: Laying a unique surface when the Tamar Bridge was built
"IN 1960 I was 18 years old and had joined the Limmer & Trinidad Lake Asphalt Company," writes Pete Organ.
"The company were based in an office and yard at Pomphlett directly on the A379 which was then a single carriageway road leading into the Iron Bridge over the River Plym and situated opposite what is now Morrisons on the side of the creek. Your readers may remember the large wall mounted clock.
"The business consisted of six mastic asphalt gangs and each gang consisted of two spreaders a labourer and a mixerman. It was a boom time with plenty of work available.
"Mastic asphalt is laid by hand with each spreader using wooden floats and fillet sticks which he makes himself. They lay the asphalt in a kneeling position wearing self made knee pads usually cut from old tyres. The solid blocks of asphalt are broken into four and thrown into a gas fired mixer containing paddles which prevent the mastic from burning and stir it to the correct consistency once it has warmed and melted. Mastic asphalt has more elasticity than rolled asphalt and is used mostly in buildings and is all hand laid. Rolled asphalt is laid by Barber Green machines as a road surface.
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"In the early Sixties the city centre was still being constructed with all the shops having flat roofs covered with mastic asphalt which has a lifespan of at least 30 years and can be easily repaired if cracks appear causing leaks. It is also used in building foundations to avoid water penetration. The Civic Centre foundations were water proofed with mastic asphalt as was the Civic Centre butterfly roof. Other buildings waterproofed at that time included Wrigleys and Treliske Hospital.
"It was at this time in the early Sixties that Limmer & Trinidad won the contract to surface the suspended section of the new Tamar Bridge. Due to the movement of this structure the architects had specified the use of various mastic asphalts consisting of a very flexible base coat laid on to the primed concrete and then a harder top coat which had bitumen coated chippings rolled into the surface. Before this set off a crimper roller was run over the surface to create an anti-skid finish.
"The quantity of materials and the plant required to surface the bridge was enormous. The normal Mastic Asphalt Mixers used locally had a one- or two-ton capacity and in order to complete the work in the timescale required the Company arranged for two coke fired four-ton capacity machines and two gangs to be brought down from Liverpool. Lorry loads of asphalt blocks were delivered daily from Somerset and coated chippings were sourced locally.
"Many loads of coke were required to stoke up the mixer machines to melt the mastic asphalt. Unlike rolled asphalt mastic asphalt can only be laid on to a dry surface so work is suspended on wet days and then gas guns are used to dry the surface. The two teams worked seven days a week laying by hand some 16 tons of asphalt each day. When the road surface was completed local gangs surfaced the footpaths and the whole project was somehow completed on time."
Great story Pete, crossing that bridge will never be quite the same again! Incidentally I wonder if anyone can answer Peter's postscript.
"The last job was inserting a solid brass plug into the road surface exactly at the centre of the Bridge which marked the boundary between Devon and Cornwall. The top was left exposed showing it to be a boundary marker and one of the Bridge surveyors marked the exact spot for us to insert the marker. How long was this small item visible and what happened to it when subsequent resurfacing was carried out?