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PEA BEACH:
A commonly used term for 20mm single size gravel, particularly from marine sources where material is naturally more rounded.
PEA GRAVEL:
A commonly used term for 10mm or 20mm single size gravels, particularly from marine sources where material is naturally more rounded.
PEA SHINGLE:
A commonly used term for 10mm single size gravel, particularly from marine sources where material is naturally more rounded.
PECKER:
Hydraulic ram, which is used to break large pieces of rock down to a size, which can be crushed.
PEGGING:
This problem, with screens, is when slightly elongated particles stick in the holes in a screen and block them thus reducing the efficiency of the screen.
PENETRATION:
A test of bitumen hardness, by releasing a weighted needle into a small prepared potted sample for 5 seconds and measuring how far it sinks in. (35 Pen-Hard, 300 Pen - Soft).
PERCENTAGE REFUSAL DENSITY (PRD):
Specification for end result requirement for compaction of coated materials. The densities of materials achieved in the road are compared with a standard well-defined laboratory test.
PERMEABILITY:
This is the ability of a material to let water pass through it and drain away.
PERMITTIVITY:
Dielectric Constant. The transport and road research laboratory have shown that the ability of bitumen to weather under the combined effects of oxygen, rain and oil deposition from traffic and ultra-violet light in sunlight is related to the dielectric constant of the bitumen.
PERVIOUS MACADAM:
Wearing course of coated macadam designed to retain a high voids content to facilitate rapid drainage of surface water through the material.
PETROGRAPHIC:
A procedure to determine the composition of coarse and fine aggregate in geological terms.
PIGMENT:
A fine coloured mineral powder used to achieve coloured products by incorporation with mixed materials.
PIPE BEDDING:
Aggregate used for laying pipes into a trench to provide equal support along their length. Different sizes are used for different sized pipes.
PITCH:
The residue, liquid when hot, solid when cold, obtained from the distillation of Tar.
PLANER:
Plant used for removing old road surfaces ready for relaying.
PLASTICISER:
An agent added to fresh concrete that reduces the amount of water needed but gives an equivalent workability, or slump. Reducing the water content also reduces the need for costly cement powder; therefore strength is maintained at a lower cost. Increasing the amount of plasticiser will result in a delaying setting time (retardation), giving increased workability without the reduction in strength. Also superplasticiser, which acts in the same way but more efficiently.
PLASTICITY, PLASTIC INDEX:
This is a measure of the amount of clay in a drystone material. The plastic index is a ratio of the Plastic Limit and the Liquid Limit.
POLISHED STONE VALUE (PSV):
This is a measure of an aggregate's resistance to the polishing action of vehicle tyres. (Limestone - 40/45, Granite - 50/65, Gritstone - 55/70+).
POLYMER MODIFIED BINDER:
Bitumen, which its properties have been enhanced by the addition of polymer.
POLYPROPELENE FIBRES:
A very fine short plastic fibre that is mixed into the fresh concrete to give significant effect on long term durability in a similar fashion to air entrainment.
PORTLAND BLASTFURNACE CEMENT (P/B):
A blend of portland cement and blast furnace slag, producing a lighter shade of grey and a slower setting time giving a longer working time. Complies with BS146.
PORTLAND CEMENT (PC):
The most commonly used cement type, often on its own or mixed with other agents to provide different workability's and strengths. Complies with BS12.
PORTLAND PULVERISED FUEL ASH (P/FA -A or -B):
A blend of portland cement and pulverised fuel ash, which increases durability and reduces water cement ration. Complies with BS6588.
PRE-COATED CHIPPINGS :
Normally 20mm or 14mm high PSV aggregate with 1.5% 50 Pen coating of bitumen, which is then allowed to cool, then broken up so they can be spread onto asphalt and rolled in when the material is hot. They provide the skid resistance and texture depth.
PRESSURE FILTER:
Apparatus used to force the methylene chloride bitumen liquor from the aggregate filler through a filter paper under pressure.
PRIMARY (CRUSHER):
The first crushing process after material has been won from the ground.
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