Despite lower environmental impacts, the use of Portland Limestone Cement (PLC) concrete has been limited due to its reduced later age strength and compromised durability properties. This research evaluates the effects of nano calcium carbonate (CaCO₃) on the performance of PLC concrete. The study follows a series of experiments on the fresh, hardened, and durability properties of PLC concrete with different replacement rates of nano CaCO₃. Incorporation of 1% nano CaCO₃ into PLC concrete provided the optimal performance, where the 56 days compressive strength was increased by approximately 7%, and the permeability was reduced by approximately 13% as compared to Ordinary Portland Cement (OPC) concrete. Further, improvements were observed in other durability aspects such as Alkali-Silica Reaction (ASR) and scaling resistance. Additionally, nano CaCO₃ has the potential to be produced within the cement plant while utilizing the CO₂ emissions from the cement industries. The integration of nanotechnology in PLC concrete thus will help produce a more environment-friendly concrete with enhanced performance. More in-depth study on commercial production of nano CaCO₃ thus has the potential to offer a new generation cement—sustainable, economical, and durable cement—leading towards green infrastructure and global environmental sustainability.

Fly ash is widely used in the cement industry to improve the performance and durability of concrete. The future availability of fly ash, however, is a concern, as most countries are inclining towards renewable energy sources as opposed to fossil fuels. Additional concerns have been raised regarding the impact of strict environmental regulations on fly ash quality and variability. This paper, therefore, evaluates if nano calcium carbonate (nano CaCO₃) can be used as an alternative to fly ash. This paper presents comprehensive testing results (fresh, hardened, and durability) for OPC (Ordinary Portland Cement) and PLC (Portland Limestone Cement) concretes with 1% nano CaCO₃ and compares them to those for concretes with fly ash (both Class F and C). Compared to concretes with fly ash, OPC and PLC with nano CaCO₃ presented improved testing results in most cases, including later age strength, permeability, and scaling resistance. As nanotechnology in concrete is a relatively new topic, more research on the efficient use of nanotechnology, such as for proper dispersion of nano CaCO₃ in the concrete, has potential to offer increased benefits. Further, nano CaCO₃ is environmentally and economically viable, as it has the potential to be produced within the cement plant while utilizing waste CO₂ and generating economic revenue to the industry. Thus, nano CaCO₃ has the potential to serve as an alternative to fly ash in all beneficial aspects—economic, environmental, and technical.

A section of jointed concrete pavement on U.S. 75, which was built from 1982 to 1985, in the Paris District of the Texas Department of Transportation (TxDOT) experienced severe pumping and settlement, even though two types of treatment (full depth repair and polyurethane foam injection) were performed. An extensive field investigation was conducted using ground penetrating radar, falling weight deflectometer, dynamic cone penetrometer, and coring to identify the causes of the continued pumping and settlement problems, and develop an optimal repair strategy. The pavement evaluation included tie bar condition, load transfer efficiency (LTE) at transverse and longitudinal construction joints, and base support conditions. Some of the tie bars failed in shear due to corrosion, which resulted in substantially low LTEs ( <40% ) at longitudinal construction joints. Pumping and settlement problems were more pronounced where the tie bars failed; the resulting large deflections exacerbated the pumping and settlement...

This paper presents the performance of continuously reinforced concrete pavement (CRCP) constructed in 1995 that utilized recycled concrete aggregate (RCA) as both coarse and fine aggregates. The project is Houston on a section of IH-10 between Loop 610 W and IH-45. In this project, no virgin aggregates were used. Concerns were raised regarding the performance of CRCP containing RCA. Detailed study was conducted to evaluate concrete material properties containing RCA. The properties of recycled aggregate measured in this study compared with virgin aggregate are consistent with those reported elsewhere: low specific gravity, higher water absorption, sulfate soundness loss, LA abrasion loss, and thermal coefficient. Little variation was observed in the paving operation due to the use of 100 % recycled coarse and fine aggregates. The moisture control of recycled aggregate, especially fine aggregate, is critical in producing consistent and workable concrete. The short-term and long-term performance of the reconstructed CRCP has been excellent, with tight crack widths and little spalling. Between concrete with virgin aggregates and concrete with recycled aggregates, there is no significant difference in thermal coefficient and permeability; however, there are significant differences in modulus of elasticity, compressive and indirect tensile strength, and water absorption. The low modulus of RCA concrete and good bond between recycled coarse aggregates and new mortar appear to be the key ingredients for good pavement performance. After more than 10 years of service under heavy traffic, the CRCP section containing 100% RCA is still providing excellent performance with no single structural distress.

The main objective of this study is to identify the cause of the punchouts observed on Interstate Highway 30 (IH-30), and to identify possible rehabilitation alternatives. Several nondestructive tests, as well as coring and trenching, were conducted in both distressed and nondistressed areas. Middepth horizontal cracks were found during routine repair and by the trenching performed in this study. It is believed that due to temperature variation at an early stage, horizontal cracks developed at the middepth interface between the steel and concrete. The truck traffic caused the horizontal cracks to deteriorate further. Repetitive truck traffic and thermal loading forced the concrete to crack vertically from the middepth where there were horizontal cracks. The closely spaced transverse and longitudinal cracks, along with the delamination, caused punchouts. Although the problem is not imminent, an immediate seal plus a 75 mm heavy-duty stone matrix asphalt (SMA) overlay will probably provide the most cost-effective remedy for this section of IH-30. Existing distressed areas should be repaired before the rehabilitation. To slow the deterioration, the district should use a latex modified chip seal or asphalt rubber seal (AC15-5TR) followed by a 75 mm heavy duty SMA. This is to provide bonding between the concrete and SMA overlay. If the district chooses to do nothing at this time, it will become costly in 2–3 years if current environmental and traffic conditions hold. The cost to repair a severely deteriorated continuously reinforced concrete pavement (CRCP) would be several times more than the 75 mm heavy duty SMA overlay.