The predominant trend in today's industrial activities is focused on the development of quality systems to satisfy customers. The following paragraphs provide an overview of some basic elements for developing a quality system in a construction company. The recommendations are based on the international ISO 9000 standards, which represent the global trend for organizing and supporting quality systems within service and product-based companies.
The asphalt mixtures commonly used in road construction are of the dense or coarse type. For the sake of clarity, these mixtures will hereafter be referred to as conventional. In wearing courses, dense mixtures are generally used, while in intermediate or base layers, either dense or coarse mixtures are applied.
The methodology of the Marshall design model was developed with the purpose of determining the optimal proportions of asphalt binder and aggregate (separated by sieves), which simultaneously achieve characteristics of stability, durability, flexibility, and porosity in the asphalt mixture thus produced.
For a binder to provide cohesion to a granular material, it must first envelop and coat it, adhering to it. If there is no aggregate-binder adhesion, the aggregate particles will hardly remain united, and the mixture will easily disintegrate. This aggregate-binder bond, which forms easily when the aggregate is dry and the binder has a fluid consistency, can be lost in the presence of water. The aggregate has a greater affinity for water than for the bitumen, and water gradually gets between the bitumen and the aggregate, causing a stripping process.
The equipment used for the construction of roller-compacted concrete (RCC) pavements is basically the same as that used for the mixing, transportation, placement, and compaction of asphalt concrete pavements. As is obvious, since it is a different material from the one for which the equipment was designed, certain considerations must be taken into account, which are detailed below.