What is water bound macadam?
Water bound macadam roads: The roads whose wearing course consist of clean crushed aggregates, mechanically interlocked by rolling and bound together with filler material and water and laid on a well compacted base course, is called water bound macadam road.
What is the difference between WBM and WMM?
In case of WBM stone aggregates and binders are overlaid on one another at the time of construction. But in case of WMM,aggregates and binding materials are premixed in a batching plant or in a concrete mixing machine and then brought to the site for overlaying and rolling.
What are the components of WBM?
a ) Course Aggregate :
Which binding material is used in WBM?
Binding Material consisting of fine-grain material passing 0.425 mm sieve is used in WBM construction thus to prevent raveling of the stones. Kankar nodules or limestone dust may also be utilized, if locally available.
What is water bound?
Definition of water-bound 1 : restrained from going by flooding waters. 2 : consolidated or held together by water especially : thoroughly soaked at the time of laying so that a natural cement formed from water and stone dust unites the particles —used of a macadam road surface.
What is bitumen bound macadam?
Bituminous Bound Macadam. Bituminous Macadam (BM) consists of one or more courses of compacted crushed aggregate premixed with bituminous material, laid immediately after mixing. The BM is laid of compacted thickness of 75 mm or 50 mm. The BM is used for construction of base course.
What is difference between GSB and WMM?
The GSB is granular sub base and WBM is water bound macadum. The GSB is used as sub base course and it also works as filter media,as it contains coarse sand and shingle. The. WBM is used as base course and it contains stone metal mixed with binding material.
What is macadam in road construction?
macadam, form of pavement invented by John McAdam of Scotland in the 18th century. McAdam’s road cross section was composed of a compacted subgrade of crushed granite or greenstone designed to support the load, covered by a surface of light stone to absorb wear and tear and shed water to the drainage ditches.
How water bound macadam is constructed?
The full form of WBM is Water Bound Macadam. It is the layer of road constructed from broken stone aggregates bound together by stone dust or screening material and water applied during construction and compacted by a heavy smoothed wheel roller.
Which material is useful as screening in the water bound macadam road construction?
The material which is used in the construction of WBM road to fill up the voids or gap in the compacted layer of the coarse aggregate is known as screenings. It is nothing but the aggregates which is of the smaller size than the coarse Aggregates which are used to fill the voids present in the coarse aggregates.
How many layers does macadam road have?
three layers
Trésaguet had recommended a roadway consisting of three layers of stones laid on a crowned subgrade with side ditches for drainage. The first two layers consisted of angular hand-broken aggregate, maximum size 3 inches (8 cm), to a depth of about 8 inches (20 cm).
What is a water bound macadam?
The water bound macadam, commonly abbreviated as WBM, is a type of road, named after John Macadam. It consists of raw materials like clean and crushed aggregates, screening and binding materials. The aggregates are mechanically interlocked by rolling and the screenings and binding materials, are used to fill the voids in the aggregates.
What are the requirements for the construction of water bound macadam road?
Binding material should be properly approved by engineer and it should have a plasticity index value less than 6 for the construction of water bound macadam road. There are the following steps in the construction procedure of WBM road as given below;
What is screening in water bound macadam road?
Screenings are the material that is used up to fill up the excess voids present in the compacted layer of course aggregate and these materials are the aggregates of a smaller size than the coarse aggregates. Non-plastic materials are used in order to reduce the overall cost of water bound macadam road.
What are the properties of coarse aggregate in water bound macadam road?
In the construction of water bound macadam road, the coarse aggregates should hold the following properties such as; It should be durable and hard. The coarse aggregate should be free from elongated particles and flaky particles. The coarse aggregate should be in acceptable size and shape.
https://www.youtube.com/watch?v=fw98pJjrLVo