The building sector is figuring out how to lower its embodied CO₂ in a sustainable way. The technology, known as Carbon Capture, Utilization, and Storage (CCUS), offers a possible remedy for this issue. Accelerated carbonation is one method of sequestering CO₂ in concrete. In this study, an M25 grade of concrete is made using Ordinary Portland Cement with 0–30% replacements of Class F fly ash. The specimens were exposed to accelerated carbonation curing for 6 h, 24 h, and 72 h, and then the specimens were tested for their compressive strength, carbonation depth, and pH. The CO₂ uptake was measured by Thermogravimetric analysis (TGA), and the occurrence of carbonation was confirmed using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The results of the study indicate a significant improvement in the compressive strength with a percentage increase of 70.46%, 111.28%, 30.36%, and 36.69%, respectively, for 0%, 10%, 20%, and 30% fly ash contents in concrete samples subjected to 72 h of accelerated carbonation curing without affecting its alkalinity. The study reiterated that accelerated carbon curing is an advisable method for countries like India that are undergoing rapid economic developments.

The utilization of class F fly ash (F-FA) is limited to 15–30% as a substitution for cement. The study intends to tap into the potential of high-volume F-FA as a pozzolan and micro filler by eliminating aggregates. The article presents the long-term behavior of a novel cement composite called no-aggregate concrete (NAC), incorporating 20% ordinary Portland cement (OPC) and 80% F-FA, with polypropylene (PP) fibers in 0.6, 0.8, and 1.0% volume fractions, in a corrosive environment. The bulk diffusion of preconditioned 100 mm cubes reveals that all mixtures’ chloride-binding capacity increases significantly with prolonged exposure. The total chloride content for mixtures M1, M2, and M3 is within acceptable limits as per EN 206. M4 with 1.0% PP fibers shows a higher total chloride content at 2 cm depth. The average chloride content for all mixtures is within 0.4%. The compressive strength of mixtures cured in water is about 90 MPa at 730 days, and is severely affected in the absence of fibers in a corrosive environment. The microstructure of mixtures at 730 days displays a cohesive, compact, continuous matrix, and the presence of unreacted F-FA.

This article presents the long-term mechanical properties of a novel cement composite, no-aggregate concrete (NAC), containing 80% of low-calcium (class F) fly ash (F-FA) and 20% ordinary Portland cement (OPC) without aggregates. The study investigates the effect of adding polypropylene fibers (PPFs) in varying volume fractions to NAC by conducting compressive, splitting tensile, flexural, bond strength, and sorptivity tests, emphasizing the morphological features over a curing duration of up to three years. The results indicate that adding PPF has an insignificant effect on compressive strength. However, flexural, splitting tensile, and bond strength improve with an increasing volume fraction of PPF. The addition of PPF achieves a ductile failure which is desirable. The initial and final water absorption rate (sorptivity) reduces with the addition of PPF. Further, scanning electron microscopy (SEM) images reveal dense precipitation of C-S-H, while energy-dispersive X-ray spectroscopy (EDS) quantifies the hydration products. The ultrasonic pulse velocity (UPV) affirms the composite’s excellent quality.

Objective: To study the effect of Polypropylene Fiber (PF) on the durability of No-Aggregate Concrete (NAC), replacing aggregates completely by incorporating fly ash and minimal water for hydration. Method: The chemical durability characteristics such as water absorption, sorptivity and resistance to acid attack are tested for NAC with PF in 0.2, 0.4, 0.6 and 0.8 percentage of volume replacement with fly ash and compared with control NAC. The reason for using PF is to improve the tensile strength of NAC. In the previous study conducted on NAC steel fibers were used, which settled down due to high relative density. Findings: The test results on water absorption show that PF with 0.4 percentage of volume replacement with fly ash offers better resistance. Even though the water absorption for other volume fractions do not vary significantly at the age of 28 days. This is due to the pores which will get subsequently filled by secondary C-S-H gel at later ages leading to less absorption. The test results for sorptivity and resistance to acid attack reveal that PF with 0.6 percentage of volume replacement with fly ash offers better resistance compared to other volume fractions. As pozzolonic reaction of fly ash is directly related to permeability, considerable imperviousness may develop at later ages. The results on resistance to acid attack for NAC with PF shows considerable loss in strength. This cannot be justified at this stage as only visual inspection is done, but the penetration of acid is not measured. However, the surface of the specimen turned softer but they are structurally intact. Improvement: The test results presented in this paper are at early ages and these parameters are under study for later ages up to 180 days.