International Concrete Abstracts Portal

The uncontrolled urban development of the last century caused high land consumption and strong non-renewable natural raw materials utilization. To solve the problems generated by soil sealing, the building sector has developed a pervious concrete manufactured with Portland cement and natural aggregates. Although this mixture mitigates the effects of soil sealing, the production of a Portland-based pervious concrete has a strong environmental impact.

The purpose of this research is to investigate an alkali-activated slag-based pervious concrete (AASPC) manufactured with tunnel muck (TM) as recycled aggregate instead of natural sand and gravel and to evaluate the relationship between aggregate size and physico-mechanical properties of no-fines concrete.

Six different single-sized recycled aggregates from tunneling works (drilling and blasting technique) were used to produce six different AASPCs that were characterized in terms of compressive strength, porosity, and water permeability under constant and variable flow.

Experimental results evidenced that the average size of aggregates strongly influences the open and total porosity of the materials, thus determining very different compressive strengths (from about 6 MPa for concrete with 16-22 mm gravel to 20 MPa for concrete made with 1-2 mm sand) and water permeability. Finally, the environmental impact of these mixtures (energy requirements, CO₂ emissions, and natural raw materials consumption) is strongly reduced in comparison to traditional Portland-based no-fines concrete at equal strength class.

We analyzed pervious concrete with regard to its acoustic absorption behavior. For this purpose, we cast a pervious concrete test series using different coarse aggregates varying in shape (crushed vs. rounded) or size (2-5 mm (0.08-0.20 in.)), to 8-11 mm (0.31-0.43 in.)). All test series were compacted in a gyratory compactor with variable intensities to reach an aimed total porosity of 25.0, 22.5, and 20.0 % by vol. and thus to evaluate the effect of the amount of the porosity beside the effects of aggregate shape and geometry on the acoustic absorption. Furthermore, we quantified the effect of the pervious concrete layer height on its acoustic absorption by a stepwise alternate cutting and measuring of the specimens at layer heights from 100 mm (3.94 in.) to 40 mm (1.74 in.). We used the first maximum of the absorption coefficient, its frequency, and the sound wave propagation speed in the porous material to evaluate the acoustic absorption. In general, a higher porosity, bigger grain size, the use of rounded aggregates, and higher cylinder height increases the acoustic absorption. A characteristic pore structure factor was found, which allows a prediction of the frequency in dependence of the cylinder height.

In this work, the freeze/thaw resistance and ambient-temperature salt resistance of fly ash geopolymer pervious concrete specimens were investigated separately, to isolate the physical and chemical phenomena underlying their deterioration during “salt scaling”. The laboratory investigation examined four groups of samples, with portland cement or activated fly ash as the sole binder, with or without graphene oxide (GO) modification, respectively. The incorporation of GO significantly improved the resistance of pervious concrete to freeze/ thaw cycles and ambient-temperature salt attack, regardless of the binder type. The specimens were then examined by using X-ray Diffraction (XRD) method, which revealed that the mineralogy and chemical composition of fly ash pastes differed significantly from those of cement pastes. Nuclear magnetic resonance (NMR) was also employed to study the chemical structure and ordering of different hydrates. This work provides an enhanced understanding into the freeze/thaw and salt scaling resistance of fly ash pervious concrete and the role of GO.

In the U.S. and around the world, large amounts of waste latex paint are generated annually, which creates a significant challenge in terms of disposal in an economic manner. Paint contains some chemicals that may be harmful to the environment if recycled as it contains volatile organic compounds. However, waste latex paint can be used to produce an economic latex-modified pervious concrete that is similar or superior to regular pervious concrete. Previous studies investigated recycling waste latex paint in concrete applications such as sidewalks. This study investigates the use of waste latex paint in producing pervious concrete and the effect of using different ratios of paint addition on the properties of the studied mixtures. The properties evaluated included physical, mechanical and hydraulic properties. Results show that while waste latex paint recycling in pervious concrete can slightly reduce its mechanical properties at 5% polymer to cement content, it can still be a viable option to prevent paint disposal in landfills.

First noticed by T. C. Powers, et al in 1948, [22] as beneficial for hydration by supplying water internally, specifiers and contractors in 2012 have grasped how the process of internal curing is implemented, how hydration behaves, and how improvements in mechanical properties, durability, and cost may be beneficial. To meet the time-dependent hydration needs of the concrete, having sufficient water internally available, when, as, and where needed, is vital for achieving optimum characteristic qualities. There is lower life cycle cost with internal curing (IC) and frequently lower first cost. In 2012, the number of projects using internal curing is increasing at an escalating rate, because the process is simple and economically implemented. Pavements, bridges, buildings, and pervious parking lots are being started now in this recession, because specifiers and contractors are saving dollars, as they build longer lasting structures while costs and interest rates are low. Developed initially to reduce autogenous shrinkage in low water-cement ratio and high performance concretes, internal curing has been found to reduce drying shrinkage. Other benefits found include reduced permeability, increased compressive and flexural strengths, less warping, stronger interfacial transition zones, greater durability, and lower carbonation.