The effectiveness of dowel bars in concrete pavements - Literature review Example

Dowel bars are popularly used in load transfer system over joints. This research paper critical examines various aspects of dowel bars from the theory behind these bars to how they ought to their proper placement in the joints. Stresses in Concrete Pavement A concrete pavement is generally referred to as a rigid pavement. It is multilayered with layers being placed on top of each. The strength of the layers decreases downwards. Figure 1 (Pavement Analysis and Design n.d) The major factors that subject concrete pavements to stresses are “the action of traffic wheel loads, the expansion and contraction of the concrete due to temperature changes, yielding of the subbase or subgrade supporting the concrete pavement, and volumetric changes” (Garber & Hoel 2009, p. 1085). In studying how concrete pavements are subjected to stresses, some basic assumptions have to be made. 1. Concrete pavement slabs are viewed as unreinforced concrete beams.

This therefore means that even if there is some reinforcement made, for instance by including steel, it is ignored (Garber & Hoel 2009, p. 1085). 2. Flexural and direct tensile stresses significantly contribute to creation of transverse and longitudinal cracks (Garber & Hoel 2009, p. 1085). 3. The subbase or subgrade layer below the concrete pavement is an elastic material. . Temperature changes lead to expansion and contraction of concrete pavement and this may in turn subject concrete pavement to tensile and compressive stresses.

Tensile and compressive stresses will depend on how wide the range of change in temperature is (Garber & Hoel 2009, p. 1085). If the range of the temperature between the top and the bottom of a concrete pavement is big enough then curling is likely to take place. If the upper surface has a higher temperature than the lower surface then the then a compressive stress at the upper surface will be experienced while the lower surface experiences tensile stress. The reverse occurs when there is change in temperature such that the top is cooler than the bottom of the concrete pavement.

Freeze-thaw damage can also result to stressing concrete pavements. This often occurs when sedimentary aggregate is used and is often exposed to freeze-thaw cycles. These cycles often lead to durability cracking (Pierce 2009 p. 20). Wheel load stresses It has been noted that traffic wheel loads induce flexural stresses. Flexural stresses induced in this manner are dependent on the position of the line of action of the load, simply the location of the wheels, with respect to the pavement edge.

Joint seal damage stresses Damages which may occur at the joints often exposes concrete pavement to a lot of stresses. The five damages which are likely to occur at the joints are: Adhesive failure when joint seal material debonds from the concrete surface; cohesive failure which may occur when the joint sealant material splits within the sealant; extrusion occurs when the joint sealant is pushed or pulled out of the joint due to slab movement and/or traffic; oxidation occurs due to exposure to the elements; and infiltration occurs when