An experimental study was carried out to understand the electrical percolation thresholds of different carbon-based nano-and micro-scale materials in cementitious composites. Multi-walled carbon nanotubes (CNTs), graphene nanoplatelets (GNPs) and carbon black (CB) were selected as the nano-scale materials, while 6 and 12 mm long carbon fibers (CF6 and CF12) were used as the micro-scale carbon-based materials. After determining the percolation thresholds of different electrical conductive materials, mechanical properties and piezoresistive properties of specimens produced with the abovementioned conductive materials at percolation threshold were investigated under uniaxial compressive loading. Results demonstrate that regardless of initial curing age, the percolation thresholds of CNT, GNP, CB and CFs in ECC mortar specimens were around 0.55%, 2.00%, 2.00% and 1.00%, respectively. Including different carbon-based conductive materials did not harm compressive strength results; on the contrary, it improved overall values. All cementitious composites produced with carbon-based materials, with the exception of the control mixtures, exhibited piezoresistive behavior under compression, which is crucial for sensing capability. It is believed that incorporating the sensing attribute into cementitious composites will enhance benefits for sustainable civil infrastructures.

No abstract

No abstract

No abstract

No abstract

The use of lightweight concrete can provide specific advantages that are favoring for mitigating seismic risk in building design. On the other hand, a significant reduction of carbon footprint could be possible through the use of geopolymer concrete. However, geopolymer concrete is mostly assessed through small specimens without reinforcement elements. This paper aims to couple the advantage of lightweight mixtures and ambient-cured geopolymerization in reinforced beams. To do this, engineering performance of reinforced lightweight geopolymer concrete was extensively investigated with different aspects. In mixtures, pumice and volcanic tuff aggregates were used with an appropriate gradation. Flexural strength, deflection capacities, initial stiffness, ductility, and energy dissipation capacity of reinforced geopolymer beams were investigated with the proposed configuration. Compressive strength and unit weight of the developed mixtures were also evaluated to meet design requirements for lightweight concrete. Results indicated that certain engineering properties (energy dissipation capacity and initial stiffness) of developed lightweight geopolymer concrete were considerably comparable with lightweight Portland cement-based concrete. Although compressive strength and unit weight of the developed geopolymer mixtures were satisfying, microstructural analysis indicated a weak bonding behavior between paste and lightweight aggregates.

No abstract

No abstract