Assessment of concrete road paving blocks with coal bottom ash: Physical and mechanical characterization

Urban road pavements made by interlocking concrete paving blocks (CPB) manufactured using industrial by-products are an improving sustainability goal for light traffic areas. Through physical and mechanical characterization, this paper aims to assess CPB with coarse coal bottom ash (CBA), a novelty in aggregate grading terms. Then, eight dry concrete mixtures (two with CBA and six without CBA) were designed with two water/cement ratios (0.63 and 0.73) to produce rectangular CPB 20 cm x 10 cm x 8 cm (length x width x thickness) by a vibro-press machine. The correlation was established between the CPB compressive strength (fc) and dynamic and static elasticity modulus (Ed and Es, respectively). Negatively, the mixtures 20S-0.73 and 20SG19-0.73, with CBA and water/cement ratio of 0.73, showed CPB with the highest air content at 28 days (11.72 % and 10.90 %, respectively). Positively, the mixes REF-0.73 and 20G19-0.73, with water/cement ratio of 0.73 and the last with CBA, presented the highest fc at 28 days (25.34 MPa and 25.05 MPa, respectively). Furthermore, an R2 coefficient of 0.18 was determined be-tween the Es results from empirical equations with fc or Ed. This paper showed that more water might be necessary to better concrete mechanical behavior. Also, it was possible to facilitate the determination of Es for CPB with fc and Ed. However, empirical equations for Es with more data, such as water absorption, air content, and unit mass, are required for a better correlation between concrete's mechanical and physical properties.

Automated summary

This paper explores the physical and mechanical characteristics of concrete paving blocks made with coarse coal bottom ash as aggregate. Eight different concrete mixtures were designed, and it was found that the highest compressive strength was achieved with a water/cement ratio of 0.73. However, the concrete blocks containing coal bottom ash showed higher air content after 28 days.