Mock-up performance evaluation study for crack reduction of blast furnace slag powder concrete mixed with expansive and swelling admixtures.

In this study, the drying shrinkage and crack reduction characteristics of blast furnace slag concrete mixed with expansive and swelling admixtures were investigated. Basic performance experiments were conducted using different mixtures of ground granulated blast-furnace slag (GGBS), with calcium sulfoaluminate as the expansive admixture and bentonite and hydroxypropyl methyl cellulose (HPMC) as swelling admixtures. Bentonite outperformed HPMC as a swelling admixture. Specimens were then prepared for mock-up tests to evaluate the drying shrinkage of blast furnace slag concrete with different combinations of bentonite, a hardening accelerator, and a self-healing agent. The addition of bentonite and calcium phosphate as a self-healing agent in small quantities reduced the drying shrinkage of the specimens, thereby reducing cracks. The cement mixture composed of 30% GGBS, 1% bentonite, and 1% calcium phosphate (30-E1-I1) showed the optimal performance among the specimens. Further, crack monitoring was performed in concrete made with ordinary Portland cement and optimal mixture 30-E1-I1. No cracks were observed for the optimal mixture. This shows that GGBS concrete can be used in practical and field applications, subject to mid- and long-term tests for cracking.

Primary and secondary aerosols in small passenger vehicle emissions: Evaluation of engine technology, driving conditions, and regulatory standards.

The characteristics of primary gas/aerosol and secondary aerosol emissions were identified for small passenger vehicles using typical fuel types in South Korea (gasoline, liquefied petroleum gas (LPG), and diesel). The generation of secondary organic aerosol (SOA) was explored using the potential aerosol mass (PAM) oxidation flow reactor. The primary emissions did not vary significantly between fuel types, combustion technologies, or aftertreatment systems, while the amount of NH3 was higher in gasoline and LPG vehicle emissions than that in diesel vehicle emissions. The SOA emission factor was 11.7-66 mg kg-fuel-1 for gasoline vehicles, 2.4-50 mg kg-fuel-1 for non-diesel particulate filter (non-DPF) diesel vehicles (EURO 2-3), 0.4-40 mg kg-fuel-1 for DPF diesel vehicles (EURO 4-6), and 3-11 mg kg-fuel-1 for LPG vehicles (lowest). The carbonaceous aerosols (equivalent black carbon (eBC) + primary organic aerosol + SOA) of diesel vehicles in EURO 4-6 were reduced by up to 95% compared to those in EURO 2-3. The expected SOA yield increased through the hot-condition combustion section of a vehicle, over the SOA range of 0.2-155 µg m-3. These results provide the necessary data to analyze all types of SOA generated by the gas-phase oxidation in vehicle emissions in metropolitan areas.