Bio-based aggregate in the production of advanced thermal-insulating concrete with improved acoustic performance

Concrete is the most utilized man-made building material and its global production reaching 25 billion tons per year represents a huge burden on our environment. Unsurprisingly, a lot of effort is dedicated to searching for suitable replacing materials of concrete constituents, e.g. of mineral aggregate that usually forms 70-80 vol% of fresh concrete mix, not only to reduce the depletion of our natural resources, but, at the same time, to improve some of the concrete properties. For example, dense building materials are not very effective in acoustic -insulation performance. In this context, renewable resources can provide a possible solution in the prepara-tion of advanced concrete composites that will help to reduce noise originating in high populated urban and/or industrialized areas. This paper is focused on the application of carbonized lightweight bio-based aggregate (BA), having about 63 % lower thermal conductivity compared to the traditional ones, in the manufacturing of lightweight concretes which, related to BA quantity in mixes, dispose with considerably mitigated thermal transport properties and enhanced acoustic-insulation function. Traditional dense aggregate was replaced with the bio-based alternative in the amount of 0-100 vol% and the batch water content was adjusted to keep similar consistency (class S4) of fresh concrete mixes. After 28 days of water curing, the development of dry bulk density, open porosity, flexural and compressive strengths as well as thermal and acoustic performance in the dependence on bio-based aggregate content were determined on hardened specimens. Experimental investigation revealed significant lightening effect of BA particles having a honeycomb-like porous structure and thus promoting the high thermal and acoustic performance of developed concretes. Accordingly, hardened concrete samples with alternative aggregate content only showed 7.5 times lower thermal transport and about 16.2 % improved acoustic performance compared with ordinary dense concrete. In addition, lower BA dosages (up to 50 vol%) allowed to produce concretes disposing sufficient strength parameters - average flexural strength about 6.5 MPa and compressive strength about 27.0 MPa maintaining their usage for structural purposes. Furthermore, bio-based aggregates are sorted among renewable resources that may mitigate environmental impacts connected with the quarrying of traditional filling materials, and thus contribute to higher sustainability of concrete production.