Q1. What are the types of macadam roads?Ans. These are of 5 types :1. Water-bound macadam it is a layer composed of broken stone aggregates which are bound together by stone dust and water with consolidation of layers with heavy roller.2. Traffic-bound macadam it is a wearing surface which is composed of broken stones or gravel which is consolidated by action of traffic, intermittent blading and dragging. This type of surface is generally built up by successive applications of 2 or more layers 2.5 to 5 cm thick.3. Wet mix macadam it consists of clean, crushed, graded aggregates premixed with granular materials and water and dense rolled on prepared surface. It is an improvement over conventional WBM and is in more durable pavement layer.4. Bituminous penetration macadam it is a thin layer of small aggregates, uniformly spread to fill surface voids of the 1st course and then rolled and followed by another light application of bituminous material.5. Cement-bound macadam it is a type which replaces bituminous materials by Portland cement or grout which is forced into the voids of the compacted stone layer.

Q2. Elaborate on water-bound macadam roads.Ans. WBM has a thickness range from 8-30 cm depending upon the purpose and principle used. The major purpose of WBM is as basis for flexible pavements and bituminous varying surfaces. One course construction is permitted to 12.5-15 cm compacted thickness, 22.5cm for a 2-course construction and each compacted layer is expected to compress from 75-80% of loose thickness.Material requirements of WBM are as follows: Trap rock with specific gravity 2.8-3.1 Hard lime stone, dolomite and granite from specific gravity 2.6-2.8 Sandstone and quartzite from specific gravity 2.4-2.7 Specifications of construction of WBM IRC 19-2005, 3rd edition

Q3. Write a short note on WMM.Ans. In WMM construction, crushed, graded aggregates and granular materials are mixed with water and rolled to a dense mass on a prepared surface.

Advantages of WMM construction over WBM construction are : Superior gradation of aggregates Faster rate of construction Higher standard of densification Less consumption of water Standards of IRC 2005 can be easily executedThickness of individual layers should not be less than 75 mm and should not be more than 200mm.Guidelines for construction of WMM - IRC 109-1997.

Q4. Write about construction of WMM roads.

Q5. What are the important considerations in WMM construction process?Ans.1. Needle or table vibrator can be used where moisture is present in the fine aggregates so that it doesnt flow out of the side walls of the WMM road.2. Excessive silt or clay in the fine aggregates shouldnt be permitted.3. The mixed materials should be transported immediately after mixing to avoid segregation and moisture loss.4. There should be minimum joints in WMM roads.5. A single paver of 7 m width and2 pavers of 3.5 m width should be worked at short distances should be used for obtaining good results.6. After the final compaction of WMM roads, it is allowed to dry for 24 hours before overlaying it with a bituminous layer.

Q6. Elaborate on bituminous macadam roads.Ans. It consists of graded course aggregates coated with bituminous binder and the strength of BM roads is derived from the mechanical interlocking of aggregate particles and cohesion imparted by the binder. The void content of bituminous macadam roads is 20-25% and the layer is of thickness 50-100 mm.

Q7. Elaborate on dense bituminous macadam roads.