Mechanical Behavior and Permeability of Plastic Concrete Containing Natural Zeolite under Triaxial and Uniaxial Compression

This paper represents a series of laboratory tests to illustrate the effects of natural zeolite and sulfate environment on the mechanical behavior, hydraulic properties, and microstructure of plastic concrete. Plastic concrete (Pl-C) is comprised of cement, water, aggregate, and bentonite. Because cement production is responsible for a significant amount of carbon dioxide emissions into the atmosphere, cement was replaced in five different percentages of 0%, 10%, 15%, 20%, and 25% by natural zeolite (Z). Moreover, all the specimens were cured in chambers simulating sulfate attack. The mechanical behavior of plastic concrete containing natural zeolite (Pl-CZ) was studied using a series of confined and unconfined compression tests. Hydraulic properties were evaluated using three different confining pressures of 200, 350, and 500 kPa. Scanning electron microscopy (SEM) images were utilized to explore the microstructure of Pl-CZ specimens. The test results show that, although increasing the zeolite content decreased the unconfined strength, peak strength, and the elastic modulus in the early ages, at the later ages, it increased the unconfined strength as well as the peak strength and the elastic modulus, while it decreased the permeability. As illustrated in SEM images, specimens cured in the sulfate environment indicated lower porosity which led to having higher unconfined strength, elastic modulus, and peak strength, along with lower permeability.