Concrete grinding residue is the waste product resulting from the grinding, cutting, and resurfacing of concrete pavement. Potential beneficial applications for concrete grinding residue include use as a soil amendment and as a construction material, including as an additive to Portland cement concrete. Concrete grinding residue exhibits a high pH, and though not hazardous, it is sufficiently elevated that precautions need to be taken around aquatic ecosystems. Best management practices and state regulations focus on reducing the impact on such aquatic environment. Heavy metals are present in concrete grinding residue, but concentrations are of the same magnitude as typically recycled concrete residuals. The chemical composition of concrete grinding residue makes it a useful product for some soil amendment purposes at appropriate land application rates. The presence of unreacted concrete in concrete grinding residue was examined for potential use as partial replacement of cement in new concrete. Testing of Florida concrete grinding residue revealed no dramatic reactivity or improvement in mortar strength.

No abstract

No abstract

The time at which portland cement concrete transitions from a viscous suspension of particles to a rigid interconnected matrix is commonly referred to as "time of set" and is a critical parameter when placing concrete structures. Use of chemical admixtures in concrete for water reduction or acceleration of hydration alters setting behavior; laboratory quality control testing is required to define the altered setting behavior. Use of the Virtual Cement and Concrete Testing Laboratory (VCCTL) for prediction of early age concrete behavior has been limited to plain portland cement concrete. Direct modeling of kinetic and thermodynamic behavior for admixture modified concrete remains challenging. An indirect method to simulate admixture alteration of set is proposed. Hydration simulations are time calibrated using heat of hydration curves obtained from admixture bearing pastes. Simulation results are compared to mortar setting tests, with agreement in certain cases falling within standard specified precision values.

This article presents a novel application of metaheuristic optimization and rating techniques to virtual test results for cement and mortar, and presents objective computational methods for the evaluation and selection of cementitious materials based on simulated material testing. A scalable approach based on particle swarm optimization of the National Institute of Standards and Technology Virtual Cement and Concrete Testing Laboratory (VCCTL) is successfully demonstrated using ∼150,000 combinations of cement phase distributions and water‐to‐cement ratios, with as few as 10% of the VCCTL runs required to obtain the optimal solutions. The application of Pareto front analysis reveals an inherent trade‐off between the modulus of elasticity, time of set, and kiln temperature (using alite:belite as a proxy) at the performance limits. This study also provides a means to objectively characterize cements in these contexts using a maximum likelihood estimator to calculate a score from the cumulative distribution function, using a random subset of the 150,000 simulated cement pastes. The proposed approach provides a new pathway to optimally proportion raw materials (and eventually waste by‐products) to reduce production costs, extend the life of a quarry, or reduce the carbon footprint of cement plants.

No abstract

No abstract

No abstract