ANALYSIS OF CONCRETE PAVEMENTS ON STABILIZED COLLAPSIBLE SOILS

Abstract

Collapsible soils are susceptible to volume changes or volume shrinkage as moisture content in the soil varies or changes by various natural or man-made occurrences. Rigid pavements construction is a constant and significant source of problem in the design and construction of foundations of buildings and highways. Collapsible soil are the specific type of soil which occurs mainly in African countries like Egypt, Iran, Iraq, Syria, Asian countries like India, mainly north and north west part of the country i.e., regions of Rajasthan, Ladakh, some regions of Maharashtra, Some regions of Punjab and Haryana, Asian countries like Afghanistan, Kazakhstan, American states like California, Nevada, Itaho and European countries like some parts of Spain, Blue Nile regions and White Nile regions and Valley Region of the Great Rift, Middle east countries including Dubai, Saudi Arabia, Qatar, Sharjah and other parts of the world. These countries are constructing structures like buildings, highways, bridges, etc. on such soils and adopting various methods for soil improvement for safety purposes. Before starting construction of any type of structure like buildings or highways, peak consideration factor is safety, economy and durability. There is a need and demand of higher value of the strength criteria parameter along with equivalent controlled decrease in cost of the foreign material leading to overall economy and decrease in the gross construction cost which are the sure signs of progress and development. Collapsible soils present problems to engineers in the construction of durable roads. The two main concerns are shrinking and losses of shear strengths of soils and changes in materials properties under a wide ranges of moisture contents. Volumes changes in collapsible soil can be signification and occurs as the moistures contents changes. Rigid pavements or flexible pavements constructions has been a particular challenge to engineers because of the volumetric changes reasons which is causing roads instability, causing pavements surfaces unevenness and cracking, severe cracking and then finally early and premature deteriorations and then reconstructions or replacements. As the moisture contents of the soils increases above a certain level, strengths as well as dry densities of the soils decreases and the plasticities of the soils increases. As a result, there will be requirements of maintenances and early and premature roads replacement will become necessary. For improvising the engineering properties of soils, a kind of materials are used called soil 6

stabilizers such as waste products and metallic elements and Geosynthetics etc. are put into use. These products normally have a large life span and they also don’t undergo biological degradation but they can create environmental issues and problems. That is why the demand of waste materials and biodegradable natural fibers are getting popularity. Using waste materials as a construction materials has always been an attraction and huge opportunity in business world. Nowadays, companies have started to examine various ways of saving wastes products in their every-day activities for both economies as well as hygiene purposes. According to CEST (Centre-of-Exploration-of-Science-and-Technology), costs of waste materials are generally about 6 times higher than what it is expected. Reduction of waste materials also cause improved hygienic conditions of the surrounding areas by reducing leaching into the ground water table. Concrete or rigid pavements are generally constructed of Portland cement concrete. They generally consist of three layers which are PCC slab as surface layer, base layer as intermediate layer and the soil sub grade. The concrete pavements have high flexural strength and are these are capable of resisting very high tensile stresses. Rigid pavements possess also have very high flexural stiffness or flexural rigidity. These pavements can transfer load through slab action but not by grain to grain transfer which is in the case of flexural pavements. They are made of Portland cement concrete either plain or reinforced or pre –stressed concrete. The plain cement concrete are expected to take up approx. 4 MPa of flexural stress. Rigid pavements constructed on soils of collapsing nature generally suffers by cracking, huge differential settlements which ultimately causes the loss of resources, money, and time of the constructing authorities. Hence there is a need to properly investigate the mitigation and prevention of the collapse of the soil.