Scholarly record

EFFECTS OF THE JOINT-UNCRACKING PHENOMENOM UPON THE USERS OF URBAN JOINTED PLAIN CONCRETE PAVEMENTS

M. Pradena, L. Houben

Abstract

Since early age, the concrete experiences deformations due to thermal differences and shrinkage. The Jointed Plain Concrete Pavements (JPCPs) have joints, these are weak zones where it is expected the cracks will be produced. In fact the designed slab length considers that the joints crack. During the construction of JPCPs in Chile, in wet climatic conditions, it was observed that the joints remained uncracked even 3 weeks after construction. Nevertheless, in average climatic conditions, the cracking time of the first joints in JPCPs at the same region is less than 42 hours after the concrete placement. When the concrete is wet, due to rain for instance, the effect of the shrinkage in the JPCP deformation is less. In addition, the rain produces a regulation of the temperature; therefore the thermal deformation is less as well. As the JPCPs are designed with a slab length determined for the cracked joints, if there are joints that remain uncracked the design hypothesises are not valid anymore. In particular, the objective of the present paper is to evaluate the effects of the joint-uncracking phenomenon upon the users or urban JPCPs. For that, the evaluation is made from a functional perspective on traditional JPCPs (i.e. slab length ≥ 3.5 m and sealed joints) including the value of the crack width under the joints and the joint seal effectiveness. The value of crack width is obtained by modelling with simulations that include amplitude temperature 2°C to 5°C and saw-cutting depth 25\% to 35\%. The relation crack width – Load Transfer Efficiency (LTE) is obtained from a curve originated with finite elements. It was found that the crack width under the joints must be 1.1 mm as a maximum for a LTE ≥ 70\%, associated to a good JPCP performance. All the analysed cases present crack width extgreater 1.1 mm and joints that remain uncracked. The Joint-Uncracking Phenomenon (JUPh) produces higher stresses in the pavement because the effective slab length is longer than the designed slab length, the cracks are wider and then the LTE lower. In addition, wider cracks allows the infiltration of water and incompressible in the joints accelerating the deterioration of the joint seals and the production of pavement deteriorations that finally affects the riding quality (IRI-value) related directly with the perception of the users of urban pavements. Deeper saw-cut (45\%) helps to eliminate the JUPh, but the crack width remains extgreater 1.1 mm. When short slabs and saw-cuts 50\% depth are used the crack width ≤ 1.1 mm, then LTE ≥ 70\%, and no presence of JUPh. Saw-cuts 50\% depth are not difficult to reach in practice using conventional sawer with thin blade ≤ 3 mm, associated to unsealed joints. Unsealed joints are an interesting innovation in JPCPs; they are part of the design features of JPCPs with short slabs and can be used in traditional JPCPs as well. In both cases unsealed joints have shown good results.

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DOI resolver: doi.org/10.5593/sgemsocial2014/B41/S15.079

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