Characteristics of compressed earth blocks stabilized with concrete dust

Abstract

The construction industry's rapid expansion has led to the accumulation of substantial quantities of concrete dust (CD) which constitutes a significant portion of construction and demolition waste. This study seeks to explore the potential of utilizing concrete dust in conjunction with cement to manufacture compressed stabilized earth block (CSEB) with enhanced mechanical properties. CSEB has long been recognized as an environment-friendly and viable alternative to traditional building blocks that harm the environment. By incorporating concrete dust into the production process, recyclability and sustainability in construction practices can be achieved. In order to identify the optimal amount of stabilizers, 15 different combinations of cement and dust content were considered. These included three cement contents (4%, 6%, and 8% by weight of dry soil) and five concrete dust contents (0%, 5%, 10%, 15%, and 20% by weight of dry soil). Compressed stabilized earth blocks (CSEB) performance was evaluated in terms of strength, durability, and thermal properties. Strength characteristics were determined through unconfined compression and flexure tests, while durability characteristics were evaluated using cyclic drying-wetting, water absorption, wet compressive strength, submersion, and efflorescence tests. CSEBs without CD displayed a maximum dry compressive strength of 6.67 MPa, while those with optimal CD replacement reached a higher strength of 10.68 MPa using the same cement amount. Comparable outcomes were seen in the flexure test, with optimal CD replacement resulting in a peak strength of 1.92 MPa compared to 1.12 MPa without CD. In terms of durability, CD-absent samples showed 13% water absorption, reduced to 10.5% with higher CD content. Wet compressive strength was relatively lower for all samples, but those with optimal CD performed best at 4.83 MPa. These fabricated samples also exhibited no efflorescence or damage from submersion. Thermal conductivity, determined using the simplified Lee's method, demonstrated a gradual increase in conductivity as CD content was increased in the sample however the obtained values remained within comparable range of conventional bricks. Furthermore, to investigate the supplementary cementitious behavior of concrete dust in CSEB, microstructural and thermal analyses were conducted. Scanning electron microscope images revealed a higher concentration of C-S-H gels in the 20% dust -8% cement combination. Life Cycle Analysis (LCA) showed that considering energy consumption, Global Warming Potential (GWP) and other environmental impacts, CSEBs are superior to traditional Fired Clay Bricks (FCB). The findings suggest that CSEB blocks stabilized with concrete dust could help to reduce construction and demolition waste while also providing a more stable and sustainable alternative to traditional building blocks.