• Cost-Effective Use of Sustainable Cementitious Materials as Reactive Filter Media (Phase I)

      Li, Wenbing; Shi, Xianming (2019-08-31)
      This report presents a laboratory study on the use of nano SiO2 as modifier in crushed fines recycled concrete (CFRCs), coupled with thermal treatment, with the goal of fabricating a sustainable reactive medium to capture the chloride anions in deicer-laden stormwater runoff. A uniform design (UD) scheme was employed for the statistical design of experiments. Predictive models were developed based on the experimental data to quantify the influence of each design parameter on the effectiveness of removing Cl- ions from simulated stormwater. The models were verified, and then employed for predictions. Finally, the samples of different CFRCs modified by nano SiO2 and heating regimes were prepared under the optimal parameters identified via the Response Surface Methodology (RSM). The optimal processing of CRFCs include the use of admixing nano SiO2 at 0.3% (by mass), then heating the material at 525oC for 3h. The structure and properties of these CFRCs materials were characterized by XRD, FTIR, BET, SEM and EDS. These advanced characterization tools revealed that the modified CFRCs achieved great potential to chemically bind chloride anions. This work is expected to produce substantial benefits for highway agencies and other stakeholders of deicer stormwater runoff, through enhanced understanding of the efficacy and appropriateness of cementitious filter media in passive reactive systems for decreasing contaminant loading in stormwater runoff. The use of CRFCs as a low-cost sorbent will be economically attractive and environmentally sustainable, diverting them from waste stream and landfill and towards sustainable stormwater management.
    • A Novel Systematic Strategy Towards Air-Purifying, Corrosion Resistant and Self-Healing Concrete Infrastructure

      Yang, Zhengxian (2019-09-15)
      Transportation causes major emissions of harmful gases (NOx, CO, VOCs). These pollutants also travel long distances to produce secondary pollution such as acid rain. The most popularly used photocatalytic cementitious composites based on TiO2 achieve the air purification function under ultraviolet sunlight, significantly impeding a broader application of photocatalytic cementitious composites. This study focused on developing an environmentally friendly and durable cementitious system based on the multifunctional photocatalytic Graphitic carbon nitride (g-C3N4). The photocatalytic cementitious composites (PCC) were prepared in three manners: (1) incorporating g-C3N4 nanosheets (CNNs) in cement at three mixing dosages (0.5%, 1% and 2% by weight of cement), (2) applying CNNs at various concentration levels as the coating on recycled asphalt pavement aggregate, (3) applying CCNs s with vinyl chloride/vinyl ester/ethylene copolymer (as a binder) as the coating on cement mortar. The photocatalytic performance and durability of the newly developed cementitious composites were evaluated systematically and the results showed that the PCC hold marked efficiency in terms of NOx removal and self-cleaning when the CNNs were applied in a proper way. The obtained knowledge sheds light on a future perspective of developing a novel systematic strategy towards air-purifying, corrosion resistant, and self-healing concrete infrastructure.
    • Pre-Stress Loss Due to Creep in Precast Concrete Decked Bulb-Tee Girders Under Cold Climate Conditions

      Vandermeer, Drew; Ahn, Il-Sang (2019-07-31)
      Accurate estimation of pre-stress losses is one of the important issues for the design of precast, pre-stressed concrete bridge girders. While this subject has been long studied by many researchers, studies on pre-stress losses in cold climates are minimal. In the present research, long-term pre-stress loss due to concrete creep was studied based on concrete creep test. Two concrete creep test frames were fabricated and placed indoors and outdoors. Concrete strains were measured by Demountable Mechanical Strain Gauge (DEMEC) from two 612 high-strength concrete cylinders in each frame. The concrete strains were collected for 11 months (7/26/2017 – 6/21/2018) after loading, and outdoor ambient temperature dropped below 0C between 100 and 250 days. Between 50 and 100 days, two curves from the two frames are similar in their patterns and values. After 100 days, the total strain from the indoor frame slowly increased reaching 1,600 and 1,700 after 250 days. However, the total strain from the outdoor frame varied between 1,000 and 1,500 and the averaged total strain was 1,300 after 250 days. In cold temperature, the occurrence of concrete creep and shrinkage was suppressed.