APPLICATION OF PERVIOUS CONCRETE IN ROAD CONSTRUCTION
This paper presents an overview of the properties of porous concrete, and the advantages of its use in pavement structures. Two mixtures of pervious concrete and a reference concrete mixture commonly used for concrete pavements are prepared and their properties compared: consistency, compressive and flexural strength, porosity and density, dynamic modulus of elasticity, as well as permeability. The possibility of their application in concrete pavements is estimated in accordance with the requirements given in General technical conditions for roadworks. Mixture with a small amount of cement and addition of superplasticizer did not meet minimum porosity and permeability required for pervious concrete. In contrast, a mixture with a higher amount of cement and without the addition of superplasticizer was evaluated as pervious one, but does not have a compressive strength required for road construction. Therefore, it is necessary to direct further research towards improving the compressive strength of mixtures of pervious concrete.
Pervious Concrete Mixture Proportions for Improved Freeze-Thaw Durability
Recent stormwater management regulations from the Environmental Protection Agency (EPA) and greater emphasis on sustainable development has increased interest in pervious pavement as a method for reducing stormwater runoff and improving stormwater quality. Pervious concrete is one of several pervious pavement systems that can be used to reduce stormwater runoff and treat stormwater on site. Pervious concrete systems have been used and are being proposed for all parts of the United States, including northern climates where severe freezing and thawing can occur. The purpose of the research is to develop pervious concrete mixtures that have sufficient porosity for stormwater infiltration along with desirable porosity, strength, and freeze-thaw durability. In this research, concrete mixtures were developed with single-sized river gravel aggregate (4.75 mm) and constant binder contents, together with high range water reducer. River sand was used as a replacement for up to 7 % coarse aggregate. Two different types of polypropylene fibers (a shorter fibrillated variable-length and a longer fibrillated single-length) were incorporated at several addition rates from 0 to 0.1 % by volume of concrete. The engineering properties of the aggregate were evaluated along with the porosity, permeability, strength, and freeze-thaw durability of selected concrete mixtures. The results indicate that the use of sand and fibers provided beneficial effects on pervious concrete properties, including increased strength, maintained or improved permeability, and enhanced freeze-thaw resistance.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.