The test is applicable to hot mix designs using bitumen and aggregates upto a maximum size of 25mm. In this method, the resistance to plastic deformation of cylindrical specimen of bitumenous mixture is measured when the same is loaded at periphery at 5 cm per min. This test procedure is used in designing and evaluating bitumenous paving mixes. The test procedure is extensively used in routine test programmes for paving jobs. There are two major features of the marshall method of designing mixes namely, a) density – voids analysis b) Stability – flow tests. The marshall stability of mix is defined as a maximum load carried by a compacted specimen at a standard test temperature of 60ºC. The flow value is deformation the marshall test specimen under goes during the loading upto the maximum load, 0.25 mm units. In this test and attempt is made to determine optimum binder content for the type of aggregate mix and traffic intensity.
The apparatus consists of :
1) A loading unit motorized, capacity 5000kgf with two telescopic pillars and an adjustable cross head. Limit switches are fitted inside to control upward or downward movement of the pillars. On-off reversing switch and indicator lamps are on the front side while a hand wheel to manually move the pillars is on the right. The load frame has fixed speed of 5.08cm per minute. Operated on 230 Volts A.C.
2) 1 No. Compaction pedal with specimen mould holder.
3) 2 Nos. Compaction Rammers, 4.5kg weight and free fall 45.7cm.
4) 1 No. Breaking head assembly with provision to fix flowmeter.
5) 3 Nos. Specimen mould 10.16cm I.D. x 7.6cm high with base plate and extension collar.
6) 1 No. Kit for specimen extraction, consists of one each load transfer bar, steel ball, specimen extracting plate.
(a) Integral type Proving Ring capacity 3000 kgs.
(b) A dial gauge 0.01 x 25mm
(c) Universal Water Bath S.S. with false bottom and pyramid shaped lid to accomodates 3 Nos. marshall specimen
(d) Thermometer 0 – 250ºC x 1ºC