MANUAL 4 - Construction Industry Development Board

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<strong>MANUAL</strong> 4 – BITUMINOUS PAVEMENT SEALS Figure 4.11: Minimum thickness acceptable By splitting the half width into two or three even parallel sections, it is easier to ensure a consistent thickness of surfacing and achieve the minimum wet thickness of > 8 mm. 5. Notes to designer/consultant 5.1 Design of slurry 5.1.1 Slurry seal binder content The slurry seal binder must be a stable grade 60% Anionic emulsion. The bulking of the aggregate must be taken into consideration when determining the amount of emulsion for the mix. Table 4.5 gives an indication of the slurry seal binder content for a range of traffic volumes for 1 m 3 of dry aggregate. Traffic volume (vpd) Binder content (litres/m 3 ) 50 – 500 500 – 1 500 1 500 – 2 500 5.1.2 Water content of slurry Table 4.5: Binder content 60 240 230 The approximate amount of water to be added to the slurry is 235 litres per m 3 . This amount could either be increased if the aggregate is completely dry and hot conditions prevail or reduced if the aggregate is damp. It is recommended a trial mix be prepared and, once the amount of water required is established, it is used consistently for the rest of the work to obtain a uniform mix. IMPLEMENTING EMPLOYMENT INTENSIVE ROAD WORKS 49 MODULE 1 2 3 4 5 5.1 5.2 6
MODULE 1 2 3 4 5 6 7 <strong>MANUAL</strong> 4 – BITUMINOUS PAVEMENT SEALS 5.1.3 Aggregate for the slurry Grading of aggregate The aggregate for the Cape seal slurry must be carefully selected. Generally speaking, the medium grade grading for the slurry must be selected. The grading curve, depicted in Table 4.6, can be used as a guide for selecting the aggregate. Sieve size (mm) Percentage by mass passing 6,700 4,750 2,360 1,180 0,600 0,300 0,150 0,075 5.1.4 Bulking of aggregate Table 4.6: Grading of aggregate 100 82 – 100 56 – 95 37 – 75 22 – 50 15 – 37 7 – 20 4 – 12 Bulking of the aggregate is a problem which must be addressed, especially if the aggregate is damp. If the aggregate is dry, there is no problem. Normally aggregate supplied from the crusher is damp and the problem will arise when part of the heap is damp and part dry. To overcome this, thoroughly wet the heap to be used with a hose, some 6 to 8 hours, or more, before use (and cover the heap with a plastic cover). Find the degree of bulking, using the following procedure: 1. Determine the inside height of the 25 litre can (say y). 2. Fill the can with damp material in the normal way when feeding the concrete mixer. 3. Strike off the excess material in the can and level with the top of the can. 4. Add water to the can of aggregate until completely saturated, making sure all the air is released by rodding the can with a thin rod (e.g. rake handle or reinforcing bar). 5. Pour off excess water and measure the drop in height of the aggregate (say x). 6. Then x/y will give the degree of bulking (bulking factor) for adjustments of the quantity of emulsion to be used in the mix. IMPLEMENTING EMPLOYMENT INTENSIVE ROAD WORKS 50
Page 1 and 2: Implementing employment intensive r
Page 3 and 4: Implementing employment intensive r
Page 5 and 6: Overview of the practice manuals Th
Page 7 and 8: MANUAL 4: Bituminous pavement seals
Page 9 and 10: MODULE 1 2 3 4 5 6 7 MANUAL 4 - BIT
Page 13 and 14: MODULE 1 2 3 4 5 6 7 Note Do not ta
Page 35 and 36: MODULE 1 2 3 4 5 6 7 Rate of binder
Page 39 and 40: MODULE 1 2 3 4 5 6 7 6 MANUAL 4 - B
Page 41 and 42: MODULE 1 2 3 4 5 6 7 Typical spread
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Page 59 and 60: MODULE 1 2 3 4 5 6 7 Slurry seal wo
Page 69 and 70: MODULE 1 2 3 4 5 6 7 Rate of binder
Page 79 and 80: MODULE 1 2 3 4 5 6 7 Note MANUAL 4
Page 91 and 92: eferences The framework agreement f
Page 93 and 94: Notes

MANUAL 4 - Construction Industry Development Board

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