High cement content is often found in concrete mix designs to achieve the unique fresh-state behavior requirements of 3D Printable Concrete (3DPC), i.e., to ensure rapid stiffening of an extruded layer without collapsing under the stress applied by the following layers. Some materials with high water absorption, such as recycled concrete aggregates, have been incorporated in concrete mix designs to minimize environmental impact, nevertheless, the fine powder fraction that remains from the recycled aggregate processing still poses a challenge. In the case of 3DCP, few studies are available regarding mix designs using Recycled Concrete Powder (RCP) for 3D printing. In this context, this study presents the use of RCP as a filler to produce a printable mixture with low cement content. An RCP with 50 μm average particle size was obtained as a by-product from Recycled Concrete Aggregate production. Portland cement pastes were produced with 0%, 10%, 20%, 30%, 40% and 50% of cement mass replacement by RCP to evaluate its effects on the hydration reaction, rheology, and compressive strength. It was found that the studied RCP replacement was not detrimental for the hydration reaction of Portland cement during the initial hours, and at the same time it was capable of modifying the rheological parameters of the paste proportionally to the packing density of its solid fraction. The obtained results indicated the viability of 3DCP with up to 50% cement replacement by RCP. It was concluded that RCP presents good potential for decreasing the cement consumption of 3DPC, which in turn could decrease its associated environmental impact while providing a destination for a by-product from recycled concrete aggregate production.

As ground glass pozzolan has recently been considered a supplementary cementitious material by the Canadian Standard of Association (CSA A-3000) and the American Standard (ASTM-1866), there is limited study on ground glass utilization on site. So, in this study, several sidewalk projects were performed by the SAQ industrial chair, the University of Sherbrooke, Quebec, Canada, from 2014 to 2017 on fields with different proportions of ground glass (i.e., 10, 15, and 20%) in different conditions are considered in such a cold climatic region. Sidewalks are a non-structural plain concrete element that is among the most exposed to chloride, and freezing and thawing in saturated conditions of municipal infrastructures. Coring campaigns were carried out after several years of exposure to these concrete (between 5 to 8 years). The results of core samples extracted from the sites were compared to the laboratory-cured samples taken during the casting. These laboratory concrete mixtures were tested for fresh, hardened (compressive strength), and durability (freeze-thaw, scaling resistance, chloride ion penetrability, electrical resistivity, and drying shrinkage) properties (up to 1 year). The results show that ground glass concrete performs very well at all cement replacement in all manners in terms of long-term performance. Besides that, using ground glass pozzolan in field projects also decreases carbon footprint, and environmental and glass disposal problems.

The U.S. National Ocean Service estimates 95,741 miles (154,080 km) of shoreline in the United States, where 163 miles per year are hardened by bulkheads and riprap. These shoreline protection techniques are costly and require frequent maintenance. Different agencies are examining “nature-based” solutions that combine vegetation with traditional concrete. Digital construction, advanced manufacturing, and innovative cementitious composites have also been proposed as potential means to lower material use, cost, and environmental impact. This paper presents a novel advanced manufacturing technique using a reactive-diffusion morphological process, called “dry-forming,” to three-dimensionally (3-D) printed concrete structures of various shapes, sizes, and complexities with standard concrete mixtures. This technology has reduced 60% of material use, enhanced local habitats, and increased the resiliency of the shoreline to sea level rise. The widespread use of this technology would increase the resiliency of coastal communities, protect aquatic life, and protect waterfront public and private real estate investments.

Determining in-place properties of mass concrete placements is elusive, and currently, there are minimal to no test methods available that are both predictive and a direct measurement of mechanical properties. This paper presents a three-stage testing framework that utilizes common laboratory equipment and laboratory scale specimens to quantify the thermal and mechanical properties of mass high-strength concrete placements. To evaluate this framework, four mass placement of varying sizes and insulations were cast where temperature histories were measured at several locations within each placement where maximum temperatures of 107 to 119°C were recorded. The laboratory curing protocols were then developed using this mass placement temperature data and the three-stage testing framework to cure laboratory specimens to represent each mass placement. Laboratory curing protocols developed for center and intermediate regions of the mass placements reasonably replicated thermal histories of the mass placements, while the first stage of the three-stage framework reasonably replicated temperatures near the edge of the mass placements. Additionally, there were statistically significant relationships detected between calibration variables used to develop laboratory curing protocols and measured compressive strength. Overall, the proposed three-stage testing framework is a measurable step towards creating a predictive laboratory curing protocol by accounting for the mixture characteristics of thermo-mechanical properties of high-strength concretes.

Carbonatable calcium silicate cement (CSC) is a promising approach to reducing the carbon footprint associated with concrete production. Carbonatable CSC gains strength by reacting with carbon dioxide (CO2). While the concept of carbonation is well known, more information on the curing process is needed. This study focuses on studying the impact of drying time, carbonation duration, and degree of saturation (DOS) on the carbonation reaction of CSC mortar. Samples were exposed to different drying durations at controlled environmental conditions to reach various DOSs ranging from 100 to 0%. The samples were then exposed to carbonation under the same environmental conditions for different durations. Neutron radiography (NR) was performed on the samples during drying to determine the DOS corresponding to various drying durations. NR was also used during the carbonation period to determine the degree of carbonation (DOC) in real time. The impact of carbonation on the diffusivity of water vapor (Dh) and pore size distribution of CSC-based samples was examined using dynamic vapor sorption (DVS). It was concluded that the carbonation reaction increased as the DOS decreased from 100 to 40%. The carbonation reaction ceased for samples with DOS values less than 6% DOS. It was also concluded that as the DOC increased, the pore structure was refined, which led to a decrease in the Dh of the CSC mortar samples.