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There are several shortcomings of using granular sub-base in concrete carriageway:
(i) Since sub-base is permeable, water can seep through sub-base and soil particles will be pumped out through contraction/expansion joints when subject to traffic load. Consequently, voids are formed underneath the pavement structure and the concrete pavement may crack under severe traffic loading.
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When there is a delay between bituminous laying of different bituminous layers (i.e. roadbase, base course etc.), a tack coat is applied on top of the bituminous layers because it helps to enhance better bonding between bituminous materials. If there is insufficient bonding between adjacent bituminous layers, they behave as separate independent layers which can hardly resist the traffic loads. When applying the tack coat, it should be sprayed uniformly on the bituminous surface and allowed for sufficient curing.
We are pleased to announce that Sir Kaushal Kishore who has been helping engineering students all over the world with his useful research and project paper submissions here at engineeringcivil.com has been awarded Vishwa Karma Award 2011 by CONSTRUCTION INDUSTRY DEVELOPMENT COUNCIL (CIDC Set up by Planning Commission Govt of India) for Category Academician/Technologist/Scientist/Innovator on 7th March 2011 at New Delhi.
We wish him heartiest congratulations and hope he will win more and more awards and show us the way to make this Civil Engineering Portal a great learning website for civil engineers.
Coordinate Design & Information System (CDIS) is a technology that was first made public a decade ago in a February, 2001 article published in Professional Surveyor Magazine that can be read at www.profsurv.com/magazine/article.aspx?i=704 explaining what was to be a revolution in technology with a promise to obsolete CAD and GIS based systems.
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The engineering world is perpetually in motion, frequently transitioning from one phase to another, and constantly having to deal with the complexities of change and the impact it creates. Now more than ever the spotlight is on engineers to shape the mould, put their best foot forward and lead us through the maze to an array of engineering wonders of the 21st century.
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Besides providing load distribution in post-construction stage and working platform in construction stage, sub-base can also serve as a drainage layer to remove water coming from the pavement.
In normal practice, joints are provided in road kerbs to cater for concrete expansion and contraction. However, the location of joints in kerbs is not arbitrary and they should match with joints in concrete carriageway.
Otherwise, it is very likely that cracks may form in concrete kerbs at location of pavement joints (Ministry of Transport (1955)).
In General Specification of Civil Engineering Works (1992 Edition), in Clause 10.09 it states “Fine aggregate for concrete shall be natural river-deposited sand consisting of at least 95% by mass of quartz grains”.
The aim of such specification is to control the quality of river sand.
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The main purposes of reinforcement in concrete roads are:
(i) to control the development and pattern of cracks in concrete pavement.
(ii) to reduce the spacing of joints. In general, joints and reinforcement in concrete structures are common design measures to cater for thermal and shrinkage movement. Hence, the inclusion of reinforcement allows
the formation of tiny cracks in concrete pavement and this allows wider spacing of joints.
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For concrete carriageway, it is normally classified into two types: reinforced and unreinforced concrete pavement. The reinforcement in reinforced carriageway (in the form of mesh) is used for controlling cracking. Then one may query how unreinforced pavement can control cracking without the use of mesh reinforcement. To answer this question, one should pay attention to the features of unreinforced concrete pavement.
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