Precast concrete paving blocks as a surfacing for local pavements

Abstract

The use of segmental paving to form hardened surfaces intended for trafficking has a far-reaching history. Its use continued through different civilisations although the methods of construction differed depending on the types of material available, the soil type and the type of traffic to be carried. Paving with bricks made of burnt clay became common some nine hundred years ago, especially in areas that lacked sufficient quantities of natural stone. The advent of bituminous and cementitious binders, that allowed the in situ casting of road surfaces, led to a decline in the use of segmental block paving. This decline persisted until the invention in the latter half of the century of machines capable of the economical production of high-quality, precisely dimensioned concrete blocks. This resulted in a re-awakening of the older forms of segmental paving and, consequently, a growth in their use. In countries where modern block paving has been introduced during the last twenty-five years, early use was generally limited to areas where it was chosen for its aesthetic appeal, as in the case of shopping malls, footpaths, walkways and landscaping purposes, among others. As confidence in its use developed and the appreciation of its potential grew, the use of concrete block paving spread to practically all types of road except for high-speed highways. The undersigned's interest in the potential of precast concrete paving blocks began in 1997 when a study was undertaken to investigate the possibility of the use of waste glass as an aggregate in the production of such blocks. The results obtained from this study were encouraging and this led to the conviction that locally-manufactured and commercially available blocks could be adopted as an ideal solution for the surfacing of roads in residential areas. The use of precast concrete paving blocks is still in its infancy in Matta and is in fact limited to small-scale applications. This dissertation aims to investigate the properties of local products in order to advocate in favour of their use in the construction of lightly trafficked roads and hard-landscaped areas. Chapter 1 of this dissertation is intended to introduce the reader to the world of segmental paving and consists of a review of the history of segmental paving, the identification of the types and properties of concrete paving blocks and a study of the vast range of applications of these blocks. Chapter 2 deals with the production of concrete paving units and gives an exhaustive description of the three major methods of manufacture in common use. Although segmental paving is generally chosen for its aesthetic appeal, this is often marred by poor detailing. It is therefore important that the method of construction of such pavements is carefully specified and controlled. Chapter 3 is therefore intended to outline good practice procedures for the laying, detailing and maintenance of segmental pavements. Pavement design has generated a tot of research world-wide and block pavement design is no exception. One should not forgot that a perfect design method for bituminous and concrete roads has been sought for decades without absolute success, mainly due to the large numbers of variables involved in any analysis. Chapter 4 deals with accepted and recommended approaches to the design of a concrete block pavement. Most countries have standard specifications for concrete paving products to ensure that the units provided are suitable for their intended use. The general forms of these standards have much in common, although there are wide differences in the testing methods adopted and, in some cases, the minimum values of the more important physical properties. For the purposes of this dissertation the standards set out in the relevant British Standards have been used as a benchmark in the testing carried out, as outlined in Chapter 5. This chapter also reproduces the results obtained from the testing programme. Appendices A, B, C and D describe the test procedures used in the testing programme. When carrying out research on this form of pavement surfacing it was noted that the terminology used in different countries and by different authors was not always consistent and that this might lead to confusion. Appendix E consists of a Glossary of Terms and was compiled on the basis of various source documents. Throughout the text of this dissertation the terms used have the respective definition given in this Appendix. This study is certainly not exhaustive and the results obtained may be interpreted in various ways. Chapter 6 outlines the undersigned's conclusions and suggestions for further studies that could be performed in this field.