Interaction of composite fume suppression and odor elimination agents with crumb rubber modified asphalt: Inhibition behavior of volatile organic compounds (VOCs) and inorganic fume.

The production and construction of crumb rubber modified asphalt (RMA) at high temperatures can produce a large amount of toxic fume, which is detrimental to human health and environment. In this study, a series of composite fume suppression and odor elimination agents (CSEAs) with both physical adsorption and chemical capture functions were adopted to reduce the emissions of volatile organic compounds (VOCs) and hydrogen sulfide (H2S). The material composition, microstructure, and specific surface area of CSEA were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and N2 adsorption-desorption isotherm (BET). The inhibitory effects of adding CSEA on toxic fume emissions from RMA at high temperatures were investigated through a combination of fume emission tests, H2S gas detection, gel permeation chromatography (GPC), and gas chromatography-mass spectrometry technology (GC-MS). The adsorption behavior of CSEA on H2S was analyzed through adsorption dynamics. Results showed that the physical and chemical properties of CSEA are stable while chemical adsorption dominates the CSEA's effect on H2S. ZnO and Ca(OH)2 exhibit good crystallization effects on the surface of the carrier by forming mesoporous structures mostly above 3.4 nm in size. The incorporation of CSEA significantly reduced the total emissions of RMA fume and the main components of VOCs in which the average inhibition rate of H2S can reach 44 % at an initial 30 mins.

Weather aging effects on modified asphalt with rubber-polyethylene composites.

Weather aging may cause more severe degradation on asphalt than thermal-oxidative aging due to the synergistic effect among oxygen, heat, ultraviolet (UV) radiation, and moisture. This study aimed to investigate weather aging effects and anti-aging mechanisms on asphalt modified with rubber-polyethylene (PE) composites. The modified binder blends and asphalt mixtures were subjected to outdoor weather aging. Dynamic shear rheometer (DSR), Fourier transform infrared spectroscopy (FTIR), Gel permeation chromatography (GPC), and optical microscopy tests were adopted to characterize the rheological properties, aging resistance, polymer degradation, and anti-aging mechanisms of modified binder blends, respectively. Mixture performance tests including Asphalt Pavement Analyzer (APA) and Ideal-CT tests were used to evaluate rutting and cracking resistance of asphalt mixtures. Results showed that weather aging can cause more severe aging to asphalt binders than pressure aging vessel (PAV) due to the severe degradation of PE particles. Rubber-PE composites alloyed with an extruder proved to stabilize PE particles in asphalt and significantly improve the aging resistance of modified binder blends. The enhanced aging resistance is attributed to the dispersion of PE particles and carbon black released by soluble rubbers.

Mix design optimization and early strength prediction of unary and binary geopolymer from multiple waste streams.

Geopolymer has received increasing amounts of attention recently due to its potential utilization of industrial and urban wastes. However, the variability of source materials and the complexity of mixture design hinder geopolymer applications derived from various waste streams. There is a need for a practical and quick scanning tool for material evaluation and mixture design optimization. Six types of industrial and urban wastes, two types of reagents, and two curing temperatures were employed in this study to systematically evaluate the feasibility of using isothermal calorimetry to optimize the geopolymer mixture design and predict the three-day strength. Test results show that isothermal calorimetry has the potential to quantify the compositional differences between source materials, identify the different kinetics of geopolymers, and determine the mechanical properties of final products. For the source materials with similar microstructure and fineness, fairly strong correlations between heat and strength could be found with R2 = 0.91 for the NaOH solution and R2 = 0.90 for the composite solution.