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The use of phase-change materials (PCM) in concrete has revealed promising results in terms of clean energy storage. However, the negative impact of the interaction between PCM and concrete on the mechanical and durability properties limits field applications, leading to a shift of the research to incorporate PCM into concrete using different techniques to overcome these issues. The storage of clean energy via PCM significantly supports the UN SDG 7 target of affordable and clean energy. Therefore, the present study focuses on three aspects: PCM type, the effect of PCM on concrete properties, and connecting the outcome of PCM concrete composite to the United Nations sustainable development goals (UN SDGs). The compensation of reduction in strength of PCM-contained concrete is possible up to some extent with the use of nanomaterials and supplementary cementitious materials. As PCM-incorporated concrete is categorized a type of building material, the large-scale use of this material will affect the different stages associated with building lifetimes. Therefore, in the present study, the possible amendments of the different associated stages of building lifetimes after the use of PCM-incorporated concrete are discussed and mapped in consideration of the UN SDGs 7, 11, and 12. The current challenges in the widespread use of PCM are lower thermal conductivity, the trade-off between concrete strength and PCM, and absence of the link between the outcome of PCM-concrete composite and UN SDGs. The global prospects of PCM-incorporated concrete as part of the effort to attain the UN SDGs as studied here will motivate architects, designers, practicing engineers, and researchers to accelerate their efforts to promote the consideration of PCM-containing concrete ultimately to attain net zero carbon emissions from building infrastructure for a sustainable future. [ABSTRACT FROM AUTHOR]

This study assesses the characteristics of preplaced aggregate concrete prepared with alkali-activated cement grout as an adhesive binder. Various binary blends of slag and fly ash without fine aggregate as a filler material were considered along with different solution-to-solid ratios. The properties of fresh and hardened grout along with the properties of hardened preplaced concrete were investigated, as were the compressive strength, ultrasonic pulse velocity, density, water absorption and total voids of the preplaced concrete. The results indicated that alkali-activated cement grout has better flowability characteristics and compressive strength than conventional cement grout. As a result, the mechanical performance of the preplaced aggregate concrete was significantly improved. The results pertaining to the water absorption and porosity revealed that the alkali-activated preplaced aggregate concrete is more resistant to water permeation. The filling capacity based on the ultrasonic pulse velocity value is discussed to comment on the wrapping ability of alkali-activated cement grout. [ABSTRACT FROM AUTHOR]

The present study performed material characterization and assessed the piezoresistive sensing capabilities of thin-walled carbon nanotube (TWCNT)-embedded ultra-high performance concrete (UHPC). TWCNTs were incorporated into UHPC from 0 to 0.5% by cement mass. The fresh-state behavior of the samples degraded as the TWCNT content increased. The TWCNT content lower than 0.2–0.3% induced a nucleation effect in the samples; nevertheless, the TWCNT content exceeding this range hindered the hydration. The degree of autogenous shrinkage of the samples proportionally decreased with the TWCNT content owing to the hindered hydration and nano-reinforcing effect of TWCNTs. The electrical percolation threshold range was found to be approximately 0.2% in the TWCNTs, which was further proven by the notable FCR variations in the sample with TWCNT of 0.2% upon cyclic loading test. TWCNTs exceeding the percolation threshold level exhibited stable FCR values regardless of the extent of compressive loading, loading frequency, and number of loading cycles. [ABSTRACT FROM AUTHOR]

• Waste rubber tire aggregate (WRTA) derived from end-of-life tires replaced clay brick aggregate (CBA) in concrete. • The flexural performance of reinforced concrete beams, mechanical properties, and shrinkage of concrete with untreated and chemically treated (bleaching powder-BP and NaOH) were assessed. • Concrete made with WRTA treated with NaOH and BP has significantly enhanced the mechanical properties and mitigated shrinkage. • WRTA treatment with BP exhibited more promising performance than NaOH. • 15 % WRTA treated with BP solution for 72 h was recommended for structural concrete production. The disposal of waste end-of-life vehicle tires has become a major environmental issue around the globe, as it is not completely biodegradable and can be a massive threat to the environment. Several researchers have attempted to use tires as aggregate with and without chemical treatment. However, to the best of the authors' knowledge, no research has investigated the performance of clay brick aggregate (CBA) concrete by replacing the CBA with bleached powder-treated waste rubber tire aggregate (WRTA) at different treatment times. Within this context, this study examines the mechanical strength, shrinkage, and flexural performance of reinforced concrete (RC) beams made with seven replacement percentages (0, 5, 10, 15, 20, 30, and 50 % by volume) of CBA by WRTA treated with H 2 O, NaOH, and bleaching powder (BP) for 2 h and 72 h. The experimental outcomes reveal that as the percentage of untreated WRTA increases, the slump, dry density, and mechanical strength decrease. Furthermore, concrete shrinkage increases with the increasing content of untreated WRTA in the mix. Likewise, the flexural load of RC beams declines with an increased percentage of untreated WRTA. It has been observed that the concrete made with WRTA treated with NaOH and BP has significantly higher mechanical strength, a flexural load carrying capacity of RC beams, and lower shrinkage compared to the untreated WRTA. The improvement in all properties was more remarkable for the treatment with BP than NaOH and treatment of 72 h than 2 h. The findings reveal that 15 % WRTA treated with BP solution for 72 h can be used as a CBA replacement whose design strength is not significantly high (f c a t 28 d a y s ≈ 20 MPa). [ABSTRACT FROM AUTHOR]

• Overburnt distorted brick aggregate (ODBA) replaced coarse aggregate (regular brick aggregate-RBA) in concrete. • Mechanical strength and porosity before and after high temperatures were investigated. • Incorporating ODBA enhanced the mechanical properties and porosity of concrete. • Concrete with ODBA performed better at elevated temperatures than the RBA. • 75% ODBA was recommended for the production of structural concrete. This study examines the mechanical and durability properties of five concrete mixes made with different replacement percentages (0 %, 25 %, 50 %, 75 %, and 100 % by volume of regular brick aggregates-RBA) of RBA by overburnt distorted brick aggregate (ODBA) before and following exposure to elevated temperatures (250, 400, and 600 °C). The compressive, splitting tensile strength and the flexural load of the beams increased by 17 %, 23 %, and 18 %, respectively, at 28 days, when 75 % RBA was replaced with ODBA. The porosity decreased for the concrete containing up to 75 % ODBA. Conversely, the compressive strength decreased as the temperature increased, which agrees with the increased porosity with the increasing temperature. [ABSTRACT FROM AUTHOR]