1.1 Life Cycle Assessment (LeA): a fascinating and sophisticated tool The greening of the economy is not a new task, but it is a challenge for which a lot of tasks still have to be done. It is known that the main source of environ mental deterioration by industry is not any more the chimneys and other process related emissions, but the products and services produced. Products are regarded as carriers of polIution: they are not only a potential source of polIution and waste during their use; they are also a cause of resource depletion, energy consumption, and emissions du ring their life starting with the extraction of the raw materials and ending with their disposal (i.e. connecting production and consumption stages). The challenge of these decades is now the greening of products and services. The new focus on products (cp. OosterhuislRubik/ScholI 1996) was introduced as a policy approach of shared responsibility in which different actors are in volved along the life-cycle of a product, each having specific responsibilities.

The observation that the durability of concrete often is lower under the combined influence of frost and deicing salts than under frost influence alone is discussed with regard to several physical aspects and mechanisms, for example, hydrodynamic effect, capillary effect, supercooling, lowered melting point of water in smaller pores, layer- by-layer freezing. It is concluded that some of the most detrimental factors with regard to the durability of concrete are supercooling of water and aqueous solutions and a higher degree of saturation of the concrete in the presence of salts. The differing effects of dry application of deicing salts on snow-and-ice-covered concrete (temperature shock) compared to the preventive salt application on humid concrete (prevention of ice formation, but with some negative aspects) are discussed.

The interaction of time under load and number of tensile fatigue cycles has been investigated for 0°/90° E-glass/epoxy laminates. The frequency was varied from 0.01 to 1.0 Hz, and the stress ratio was varied from 0 to 1.0 (static fatigue). Square wave and spike loading data indicate a higher initial strength but also a higher rate of loss of initial strength per decade of cycles for waveforms with less time at maximum stress. S-N curves tend to converge at low stress to the same number of cycles to failure, regardless of waveform. Long-term results are reported for fiberglass box beams fatigued for up to 108 cycles at relatively low loads, where matrix cracking and delamination damage were studied. A brief description is also given of field failures involving crack growth in a brittle mode, normal to the fibers.

The mode of fatigue crack growth is described for a 0/90° E-glass/epoxy laminate under cyclic tension-tension loading. Crack growth appears to occur in a stepwise fashion with the crack remaining stationary for many cycles before each step of growth, whereupon a ligament of longitudinal ply at the crack tip is broken. A simple theory is described which assumes that the ligament at the crack tip is fatigued according to the S-N curve of the unnotched material. Using an assumed stress field and cumulative damage law, the number of cycles for initial growth from a notch and the rate of crack growth thereafter are predicted, and good agreement is demonstrated with experimental data.