A more durable pervious concrete was produced using mechanically processed carbon fiber composite scraps from the aerospace industry, referred to as cured carbon fiber composite materials (CCFCMs). ...The processed CCFCM were fiber-like shreds with large aspect ratios and were a composite of carbon fibers reinforcing the thermoset resin. CCFCMs were used as 0.5, 1, 2 vol% replacement of natural coarse aggregate in a low-porosity (well packed) pervious concrete with pea gravel. Mechanical and durability evaluation was performed compared to two baseline mixes, a neat mix with zero CCFCM (control) and a mix with 0.5 vol% replacement with commercial synthetic fibers (POLY-0.5). CCFCMs disturbed the packing arrangement of natural aggregate and resulted in higher porosity. Mechanical properties increased with more amounts of CCFCM due to bridging actions of high-aspect-ratio elements and reached similar or higher flexural strength than the control at 1 and 2 vol%. CCFCM had similar or higher mechanical properties than POLY-0.5, except the synthetic fibers increased the flexural toughness index by 85% compared to the maximum 53% increase by CCFCM. The most significant enhancement was with CCFCM-1 and 2 vol% in rapid freeze–thaw cycling and deicer chemical application evaluation. CCFCM-2 maintained 95% of its original mass and 77% of the initial dynamic modulus after more than 200 cycles. The incorporation of CCFCM as a replacement of natural aggregate shows a high potential for previous concrete while creating a new use for this high-volume waste from the automobile and aerospace industries for a circular economy.
Pervious concrete has made a comeback as a green infrastructure solution for urban areas. The fast adoption of the permeable pavement practice by many cities worldwide warrants an urgent response ...from researchers to address the lack of standards for mixture optimization, pavement design, and characterization methods, which results in field placements with insufficient strength and durability. These critical issues are the topic of this review paper. Laboratory test results relevant to the mechanical and hydrological performance of pervious concrete, e.g., compressive and flexural strength, impact and abrasion resistance, porosity and permeability, and their interrelationships are discussed in great detail. The use of additives, alternative binders, fillers, and fibers from natural sources and waste streams and their impact on pervious concrete performance parameters is reviewed. Efforts in computational modeling of mechanical, structural, and hydrological behavior of pervious concrete materials and pervious concrete pavements are also presented. Based on this extensive review of state of the art on these important matters, the areas of need for future research are identified.
•Studies of mixture composition optimization and characterization methods are discussed.•Review of effect of waste materials on pervious concrete mixture design and mechanical performance is presented.•Statistical models of pervious concrete mechanical properties are summarized.•Numerical modeling of pervious concrete stress-strain behavior and permeability are reviewed.•State of the art of pervious concrete pavement design is discussed.
We present a proof-of-principle study about the use of a sensor for the nondestructive monitoring of strength development in hydrating concrete. The nondestructive evaluation technique is based on ...the propagation of highly nonlinear solitary waves (HNSWs), which are non-dispersive mechanical waves that can form and travel in highly nonlinear systems, such as one-dimensional particle chains. A built-in transducer is adopted to excite and detect the HNSWs. The waves are partially reflected at the transducer/concrete interface and partially transmitted into the concrete. The time-of-flight and the amplitude of the waves reflected at the interface are measured and analyzed with respect to the hydration time, and correlated to the initial and final set times established by the penetration test (ASTM C 403). The results show that certain features of the HNSWs change as the concrete curing progresses indicating that it has the potential of being an efficient, cost-effective tool for monitoring strengths/stiffness development.
Every year ~ 6-8 million tonnes of shrimp, crab, and lobster shell wastes are generated, requiring costly disposal procedures. In this study, the chitin content of shrimp shell waste was oxidized to ...produce chitin nanocrystals (ChNC) and mechanically fibrillated to obtain chitin nanofibers (ChNF) and evaluated as additives for mortar. ChNF (0.075 wt%) and ChNC (0.05 wt%) retarded the final setting time by 50 and 30 min, likely through cement dispersion by electrostatic repulsion. ChNF (0.05 wt%) with a larger aspect ratio than ChNC resulted in the greatest improved flexural strength and fracture energy by 24% and 28%. Elastic modulus increased by up to 91% and 43% with ChNC and ChNF. Solid-state nuclear magnetic resonance (NMR) showed ChNF (0.05 wt%) enhanced calcium-silicate-hydrate structure with a 41% higher degree of polymerization, 9% more silicate chain length, and a 15% higher degree of hydration at 28 days. Based on the findings, chitin seems a viable biomass source for powerful structural nanofibers and nanocrystals for cementitious systems to divert seafood waste from landfills or the sea.
•Cured carbon fiber composite materials (CCFCMs) from industrial byproduct were mechanically processed for application in porous hot mix asphalt (PHMA).•The inclusion of Fine CCFCMs in PHMA improved ...the mechanical properties and draindown resistance.•As a reinforcement agent, the Fine CCFCMs improved the rutting resistance of PHMA.
Porous hot mix asphalt (PHMA) allows runoff to infiltrate through the pavement. Cured carbon fiber composite materials (CCFCM)s from aerospace production lines were ground into three size groups (Fine, Medium, and Large) and reused as reinforcement agents for PHMA in comparison to commercial synthetic fiber. The Fine CCFCMs premixed with liquid asphalt binder performed the best to reinforce PHMA in terms of indirect tensile strength and cracking resistance at both 25 °C and −10 °C. The addition of fine CCFCMs and synthetic fibers reduced the porosity by 17% and infiltration rate by up to 20%, while both fibers showed to prevent draindown of asphalt binder at an elevated temperature. The PHMA reinforced with the Fine CCFCMs performed the best in rutting resistance.
Pervious concrete pavements have received increasing interest for stormwater management, especially with record-breaking extreme weather events, including floods. To efficiently direct stormwater, ...pervious concrete design should provide sufficient hydraulic conductivity that can be maintained over its service life. To study the impact of mixture parameters (aggregate gradation, aggregate-to-paste ratio, and porosity) on hydraulic conductivity and extent of clogging, an approximate model of pervious concrete as sphere packing was generated by the Discrete element method (DEM). The DEM was used in a Pore-scale finite volume (PFV) model to predict the hydraulic properties of pervious concrete. The model was validated with hydraulic conductivity results of seventy pervious concrete cylinders and then used to simulate the clogging of voids with sediments. At a sediment load rate of 0.1 kg/m2 with 0.25–1 mm particle size, the hydraulic conductivity of sphere packings at initial porosity of 20 and 30 % dropped by 66 and 56 %, respectively. The simulations showed that, at the same porosity, larger pore volume (formed by using larger aggregate size) results in a significant drop in permeability due to sediments accumulation.
Pervious concrete (PC) pavements are used for stormwater management and flood mitigation. However, the highly porous macrostructure of PC results in low mechanical properties compared to portland ...cement concrete (PCC). Cured Carbon Fiber Composite Material (CCFCM) is heavily used in manufacturing of high-performance products. Therefore, large quantities of excess CCFCM materials are generated, requiring proper disposal and reuse applications. In this study, recycled CCFCM were used as discrete structural reinforcement in a PC pavement demonstration project. In addition to one Control section, two pavement sections were paved using PC mixed with 0.27 and 0.40% volume fractions of CCFCM, respectively. Field cores and cast specimens from CCFCM-PC mixes achieved similar 7 and 28-day flexural, tensile, and compressive strengths to the Control, although their porosity was higher. Furthermore, CCFCM-PC sections had higher infiltration rates than the Control. Using lightweight deflectometer load testing, CCFCM-PC pavement sections showed lower surface deflection than the Control under the same applied load. Based on these findings, CCFCM was successfully implemented as reinforcing elements in PC, providing an environmentally-friendly solution to recycle this material.
Nondestructive methods to obtain the electrical conductivity (σ) or resistivity (ρ) of concrete are gaining popularity for durability evaluation. However, these methods are susceptible to the effects ...of curing and conditioning, primarily temperature and degree of saturation. Before σ of concrete at varied temperatures can be used for durability assessment, appropriate corrections must be made to account for the effect of temperature (T). In this study, two existing and one new temperature correction methods were evaluated for 12 mortar mixtures varying in water-to-cementitious material ratio (w/cm) and the content and types of supplementary cementitious materials (SCM). Mortar specimens instrumented with embedded sensors were cured in sealed conditions for 11–13 months. After this period, the sealed specimens were subjected to stepwise temperature change in 5–50°C range while σ was recorded using the embedded sensors. Linear, bilinear, and Arrhenius temperature correction (LTC, BLTC, and ATC, respectively) were fitted to the obtained σ-T datasets and were evaluated for fitness. LTC provided an acceptable fit to the σ-T data (R2 > 0.81) but was found the most suitable in 5–30°C temperature range. BLTC was defined as a combination of two distinct LTC below and above the reference temperature at 23°C and had a better fit to the data (R2 > 0.96). Lastly, ATC showed the best fit among the tested methods (R2 > 0.98) and was found applicable for the full tested temperature range. Comparison of correction coefficients among the mixtures indicated that increase in w/cm results in less sensitivity of σ to temperature. Mixtures with SCM generally exhibit higher temperature sensitivity compared to the corresponding plain mixture. Since the variations in correction coefficients were not substantial (less 18% variation among 10 of 12 mixtures), a single value of activation energy of conduction (Ec) at 32 kJ/mol was identified as the general recommendation for all the tested mixtures.
Nanomaterials have been widely researched for use in construction materials. Numerous studies demonstrate that nanomaterials in small quantities can significantly improve the macroscopic properties ...of cement paste, mortar, or concrete through various mechanisms. Nanomaterials retrieved from biomass sources have recently gained particular research interest due to remarkable structural properties and the source material’s abundance and renewability. Cellulose and chitin are the most abundant polysaccharides in nature; thus, they are candidates for nanomaterials extraction as multifunctional additives in cementitious systems. In recent years, cellulose nanomaterials in cementitious composites have been extensively investigated, but chitin nanomaterials and starch derivatives for cement and concrete are still emerging research areas. This review article starts with an overview of polysaccharide nanomaterials’ (PNMs) physicochemical properties as a result of different chemical and mechanical extraction processes. Next a brief overview of cement hydration chemistry and microstructure and the interfacial interactions between the cement and the various surface chemical functionalities of PNMs are discussed. Then, the key mechanisms governing the cement strength enhancement by PNMs, such as bridging, nucleating and filling effect, and internal curing, are described. Finally, the impacts of PNMs on other properties of the cement are discussed.
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