## 1 Introduction
[30] reported that high-albedo construction materials in urban areas are enough to alleviate high temperatures in megacities worldwide, such as Shenzhen and Hong Kong in China. The albedo of some common materials used in pavement construction is given in Table 1, where it can be seen that in comparison with asphalt, they are rather high [31; 32; 33; 34; 35]. Concrete is a mix composed of Portland cement (grey or white) [36], aggregates, water, chemical admixtures, and sometimes supplementary cementitious materials (SCM) such as coal fly ash, blast-furnace slag and silica fume. Besides, the external concrete surface may be covered by a fine white layer of calcium carbonate formed by carbonation [37] or salts deposition (efflorescence). Albedo of smooth-surface concrete ranges from 0.41 to 0.77. Moreover, white-cement smooth concrete's albedo value is approximately 0.18-0.39 higher than that of grey-cement smooth concrete [31]. Nevertheless, abrasion, weathering and dirt reduce concrete albedo about 0.05-0.19. These albedo values are higher than albedo values found in many natural surfaces (e.g., desert is 0.35 and jungle is 0.12) [31]. Another way of fighting against climate change is the use of cost-effective new materials such as polymer wastes and nanofibers [38; 39]. In addition, they could have a positive contribution to the concrete albedo. The Leadership in Energy and Environmental Design (LEED) program for certifying the amount of sustainability incorporated in a building design is one of the most widely utilized green building rating systems in the world [40]. There are 110 points available through seven categories (base certification: 40-49; silver: 50-59; gold 60-79, and platinum \(>\) 80 points). One point can be scored in the credit 7.1 by using hardscape materials with an SRI of at least 29, such as conventional concrete pavements [41]. Additionally, 1-2 points could be scored under the materials and resources credit 4 for recycled content. These points may be awarded if at least 10-20% of the total cost of the materials contains by-products and recycled materials. Some blended cements such as slag cements are considered in LEED as a material made with recycled constituents [40]. Climate change has become a central concern in local policy. In 2005, The C40 Cities Climate Leadership Group was founded. This is a network of mayors of about 100 world-leading cities worldwide working together to confront the climate change crisis. In 2020, 54 cities representing about 10% of the world's economy finalized climate action plans in line with avoiding climate change. In 2021, the C40's Leadership Standards for 2021-2024, to ensure C40 are on the way to a zero-carbon future, went into effect. Furthermore, C40 partnered with The Global Cool Cities Alliance (GCCA), which was launched in 2010. One project of this group is the \"100 Cool Cities\" program that will endeavor to obtain commitments from 100 major cities worldwide and great implementation of cool pavements and roofs in a timely and predictable manner [42]. Considering that pavements and roofs comprise roughly 60% (normally, roofs account for 20-25%, whereas pavements for approximately 40%) of city surfaces, pavements and roofs with high solar reflectance could help to reflect away the summer temperatures of cities (Urban Heat Island, (UHI)), improving outdoor comfort by reducing summer air temperature by 2-3 \({}^{\circ}\)C.  
The City of Madrid committed to ensuring that a large area of the city will be \"zero-emission\" by 2030, by signing the C40 Green and Healthy Streets Declaration on 9 th December 2019. The specific objectives for each of the strategic objectives are defined within the context of the overall commitment of the Roadmap to Climate Neutrality by 2050. Within the strategic objective named \"A cooler city\", there is a specific objective to encourage the use of high-albedo building materials [43]. This paper is focused on testing reflective concrete pavements.