International Concrete Abstracts Portal

This paper describes the design and application of con-crete block pavements for roads, industrial hardstands and other transport applications. The paper begins with a summary of the response of segmental paving to traffic. The costs of block paving are then compared to those associated with other types of pavement. The evolution of mechanistic design procedures for this form of construction are then described. These procedures are suitable for implementation on microcomputers. Typical examples are given of the application of this methodology to both roads and heavy industrial pavements. The examples include designs specific to North American conditions.

Interstate 80, which traverses Iowa in an east-west direction, has been showing various signs of deterioration be-cause of heavier than anticipated truck traffic, both in volume and in truck weight. Several solutions have been tried, includ-ing complete replacement by a new inlay, full-depth patching, asphalt overlay, and portland cement concrete (PCC) overlay. Several factors favor PCC overlay, including economics, con-struction time, increased load capacity of the new pavement, and the need to minimize the consumption of new resources. The design provides for a 4-inch (10.2 cm) thick PCC overlay over the old lo-inch (25.4 cm) thick pavement. Preparation for the overlay required numerous full-depth patches of deteriorated joints, followed by shotblasting, milling where needed, and the application of a cement water grout. This paper discusses the design, contract requirements, construction procedures and pave-ment performance to date.

This paper describes the theory and applica-tion of a methodology for evaluating the relative effects of load and non-load-related factors on rigid pavement performance. The computation is based upon aggregated pavement performance data and pavement rou-tine maintenance cost data which can be acquired rela-tively easily on a regular basis at both network and project levels. An integral part of the methodology is a procedure developed to account for the effects of routine maintenance on pavement performance. The Interstate highways in Indiana are analyzed to demon-strate the application of the proposed methodology.

The nature of the design equations for the nonbonded concrete overlays currently used by the US Army Corps of Engineers was examined, and the original source of the equation was also examined. Using simple mechanics, it was found that the existing equation is true when the condition Elhl = E2h2 is true, where E1 3 E2 9 hl 9 h2 are the elastic moduli of the concrete overlay and the base slab, and the thickness of the overlay and the base slab, respectively. When El is assumed to be equal to E2 ' the existing equation is valid when hl = h2 is true. Also using simple mechanics, new overlay equations were developed which are suitable for different thicknesses and elastic properties in the overlay and base concrete slabs. The difference in the computed overlay thickness between the new and existing equations is not large when the overlay thickness is equal to or greater than the base slab. The difference can become significant when the overlay thickness is much less than that of the base slab. The new equations were compared with the finite element computer program for concrete overlays with various combinations of slab thickness, elastic property, and subgrade modulus. The comparisons were very favorable, indicating that the overlay equations developed in this paper are analytically correct. The validity of the equations was also examined using the results of the field full-scale accelerated traffic tests on concrete over-lays. It was difficult to judge whether the new equations are superior to the existing equation. This conclusion was expected because for all the seven test sections analyzed, the overlay thicknesses used were either equal to or greater than those of the base slabs. It is recommended at this time that the existing design equations for nonbonded overlays not be replaced by the new equations because of lack of verification from field test data.

In China steel fiber reinforced concrete has been used in several projects including the highway, street, overlay of airfield pavement, mining and tunneling, explo-sion- proof gate, etc. In this paper the toughness and the toughness index of steel fiber reinforced polymer cement matrix composites are studied. In particular, Jm, computed by an approximate for-mular of J-integral under the pe ak 1oad of load-deflection curve, as a toughness index to t hese composites is discussed. Three-point bend tests both on the notched beams and the unnotched beams of steel fiber cement composites are per-formed. O n the basis of results, the effects of the follow-ing factors: matrix, fiber content, aspect ratio, and fiber diameter, on the toughness of the steel fiber cement compos-ites are analyzed. As a result of the synergistic effect of steel fiber, polymer and matrix, the toughness of steel fiber reinforced polymer cement concrete is much higher than that of steel fiber reinforced concrete.