**4.2 Reduction of the amount of cement by means of optimised structural pavement design**

Since all the desired objectives and requirements of an engineering structure are specified in the design phase [75], in the case of concrete pavements, the structural design plays an important role in improving the sustainability of the road infrastructure [76]. In this regard, the design method of short slab Jointed Plain Concrete Pavements (JPCP) is a patented alternative that proposes to shorten the slabs size in such a way that there is only one set of wheel loads per slab [77, 78]. Therefore, the traditional configuration where the slab can support the full vehicle load does not occur. The benefits of this design include, as well, a reduced slab curvature. In this way, the pavement thickness can be reduced up to 10 cm [78], which means than less concrete is required, and then the demand of cement, aggregates and water decreases.

Additionally, it is postulated that the primary method of transferring loads between slabs is the aggregate interlock mechanism, and then, dowel bars are not part of the standard design.

These features result in savings of approximately 20% of the construction cost, which makes concrete pavements with optimised geometry a competitive solution compared to asphalt pavements when only construction costs are considered in the analysis, i.e. without life-cycle costs [78]. This is especially relevant in developing countries, where construction costs can be the main limit to the application of more durable pavements with less maintenance intervention requirements than asphalt pavements [79, 80]. In fact, promising experiences with concrete pavements with optimised geometry have been carried out in developing countries such as Chile, Guatemala, Nicaragua and Peru [78, 81–83]. Moreover, evaluations of short slab test sections in the United States indicate that these pavements have the ability to maintain in-service performance similar to traditional concrete pavements up to 51.3 million equivalent axle loads (ESAL) [84].

In order to estimate the benefit of this engineering innovation, the emissions generated in 18 short slab projects and their traditional JPCP equivalents were compared [85]. The assessment was based on environmental management principles and measures the impact on the environment and human health [86, 87]. Furthermore, it is assumed that the design hypotheses are fulfilled and then the inservice performances of both pavement alternatives are equivalent. For this reason, the evaluation is focused from the material procurement stage to the construction phase, which presents differences between the two design philosophies.

The results indicate that, for all cases evaluated, the concrete pavements with optimised geometry generate lower harmful impacts (**Figure 2**). Regarding environmental impacts, all indicators presented reductions above 10%, with global warming, acidification and ozone depletion showing the highest reductions with 33%, 27% and 24%, respectively. In terms of human health impacts, short slab pavements reduce, as well, exposure to carcinogenic, non-carcinogenic and respiratory pollutants by 26%, 23% and 27% respectively.

The reduction in these indicators reflects that concrete pavement with optimised geometry contribute to a more sustainable construction. The visible advantages of short slab pavements are related to their ability to maintain a performance similar to a traditional JPCP while using thinner slabs. This reduction means less cement consumption, which is the main generator of emissions.

*Different Approaches to Develop More Sustainable Concrete Alternatives DOI: http://dx.doi.org/10.5772/intechopen.100194*

**Figure 2.** *Percentage of emission reduction with short slabs [85].*

#### **4.3 Increasing durability to reduce the concrete demand**
