A Sustainable and Environmentally Friendly Concrete for Structural Applications

Abstract

The purpose of this study is to utilize waste products—precipitated calcium carbonate (PCC) and upcycled recycled concrete aggregate (upcycled RCA or UCA)—in civil works projects. To do so, tests must be performed to determine the engineering properties of the materials in which PCC and UCA are sequestered. PCC is a fine to coarse grain waste product generated during the production of sugar from sugar beets. UCA is produced from demolished and returned concrete by the extraction of primarily calcium and alkalinity. The study also includes the use of both PCC and UCA in the same concrete mix design. The test results on PCC alone show that the optimum content to achieve a minimum 28 MPa (4000 psi) compressive strength is 25% and 30%. The corresponding compressive strength of mixes in which conventional aggregate was replaced by UCA is about 48 MPa (7000 psi) to 55 MPa (8000 psi) at the same water: cement ratio (0.44) by weight. The compressive strength of concrete with 25% to 30% cement replaced by PCC and varying aggregates replaced with UCA ranges from 19.3 to 40 MPa (2800 to 5800 psi). Other tests on PCC and UCA include tensile strength of 2 to 3 MPa (293 to 423 psi) and flexural strength of 1.3 to 1.9 MPa (183 to 279 psi). Analytical techniques such as X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX), and scanning electron microscopy (SEM) were used to identify the constituent elements and chemical compounds present in PCC, including calcium carbonate and silica. Based on the test results, the composition of PCC by weight indicates 45.9% calcium, 39.4% oxygen, and 9.2% carbon. Based on the results of this study, we can expect to reduce carbon emissions in the production of cement and aggregates, as well as utilize waste products in the civil engineering field.

Soil Stabilization Using Precipitated Calcium Carbonate (PCC) Derived from Sugar Beet Waste

“…It was challenging for the ISU team to ascertain whether PCC had a binding effect on concrete. Thus, this study serves as supporting research for the concrete research mentioned in [26,27]. [26,27].…”

“…The research on concrete conducted by our team found that Portland cement can be replaced by PCC up to 30% by weight while still maintaining the compressive strength of concrete above 27.6 MPa (4000 psi) [26,27]. However, there is a decreasing trend in compressive strength as the amount of PCC content increases, as shown in Figure 1.…”

“…Figure 1.Compressive strength of concrete containing PCC[26,27]. From the left, the first bar with a black outline without color fill is the normal concrete, while gray bars represent concrete with various amounts of PCC.…”