A conceptual design of two-stream alkali-activated materials

To properly control the reaction kinetics and fresh properties evolution in conventional alkali-activated materials (AAMs), a conceptual design of two-stream AAMs has been proposed in this study. This is achieved by dividing the solid and liquid components in AAMs, including blast furnace slag (BFS) and electric arc furnace slag (EFS)...

A novel bi-level temporally-distributed MPC approach: An application to green urban mobility

Model predictive control (MPC) has been widely used for traffic management, such as for minimizing the total time spent or the total emissions of vehicles. When long-term green urban mobility is considered including e.g. a constraint on the total yearly emissions, the optimization horizon of the MPC problem is significantly larger than the...

Adaptive Parameterized Control for Coordinated traffic Management Using Reinforcement Learning

Traffic control is essential to reduce congestion in both urban and freeway traffic networks. These control measures include ramp metering and variable speed limits for freeways, and traffic signal control for urban traffic. However, current traffic control methods are either too simple to respond to complex traffic environment, or too...

Prediction & optimization of alkali-activated concrete based on the random forest machine learning algorithm

Alkali-activated concrete (AAC) is regarded as a promising alternative construction material to reduce the CO₂ emission induced by Portland cement (PC) concrete. Due to the diversity in raw materials and complexity of reaction mechanisms, a commonly applied design code is still absent to date. This study attempts to directly...

A mix design methodology of blast furnace slag and fly ash-based alkali-activated concrete

Although the application of blast furnace slag and fly ash-based alkali-activated concrete (BFS/FA-AAC) has both economic and environmental benefits, it is limited by the lack of a straightforward mix design method. In this paper, an experiment was conducted to investigate the effect of control factors, including the Na₂O/binder...

Optimal Sub-References for Setpoint Tracking: A Multi-level MPC Approach

We propose a novel method to improve the convergence performance of model predictive control (MPC) for setpoint tracking, by introducing sub-references within a multilevel MPC structure. In some cases, MPC is implemented with a short prediction horizon due to limited on-line computation capacity, which could lead to deteriorated dynamic...

Effect of Activator Solutions on the Thixotropic Behavior of Alkali-Activated Slag Concrete

Alkali-activated material (AAM) is developed as a green alternative binder to replace Portland cement (PC) in the construction field. However, the large-scale application with AAM concrete is limited so far, with the insufficient knowledge of rheological behavior being a major obstruct. Thixotropy of concrete is of great interest, which can...

Grammatical-Evolution-based parameterized Model Predictive Control for urban traffic networks

While Model Predictive Control (MPC) is a promising approach for network-wide control of urban traffic, the computational complexity of the, often nonlinear, online optimization procedure is too high for real-time implementations. In order to make MPC computationally efficient, this paper introduces a parameterized MPC (PMPC) approach for...

Interpretation of the early stiffening process in alkali-activated slag pastes

To better understand early stiffening of AAS pastes, distinctive microstructural features by varying the silicate modulus (Ms) have been visualized with in-situ microscopy. In addition, the activation reaction was monitored with multiple approaches, while solid and liquid phases in hydrating AAS were characterized separately. In silicate...

A mix design methodology of slag and fly ash-based alkali-activated paste

In this paper, a series of experiments were conducted to systematically and quantitively explore the effects of control factors on the early age properties, i.e., workability and strength of slag and fly ash-based alkali-activated paste (BFS/FA-AAP). The control factors on the workability (flowability and setting time) of BFS/FA-AAP include...

Evaluation of rheology and strength development of alkali-activated slag with different silicates sources

This study provides a detailed investigation on the reproducibility of two groups of alkali-activated slag (AAS) mixtures, from both fresh properties and strength development perspectives. Three different commercial sodium silicate solutions and one lab-produced silicate activator (made of silica fume and sodium hydroxide) were used to...

Effect of High-Range Water-Reducing Admixtures on Alkali-Activated Slag Concrete

The rapid workability loss of alkali-activated materials (AAM) has been a major obstacle limiting its onsite application. In this study, two conventional SPs (made of polynaphthalene sulfonate (PNS) and lignosulfonate (LS) salts), which have been reported to be effective in some specific AAM mixtures were separately applied in alkali...

Fresh and hardened properties of alkali-activated slag concrete: The effect of fly ash as a supplementary precursor

The present study explores the possibility of replacing blast furnace slag (BFS) with coal fly ash (FA) to produce alkali-activated material (AAM) concrete with hybrid precursors. With an increased FA replacement ratio, the reaction kinetics, fresh and hardened properties of AAM mixtures have been investigated. The retardation effect on the...

Combined MPC and reinforcement learning for traffic signal control in urban traffic networks

In general, the performance of model-based controllers cannot be guaranteed under model uncertainties or disturbances, while learning-based controllers require an extensively sufficient training process to perform well. These issues especially hold for large-scale nonlinear systems such as urban traffic networks. In this paper, a new...

Future perspectives for alkali‐activated materials: from existing standards to structural applications

The production of cement and concrete contributes significantly to global greenhouse gas emissions. Alkali‐activated concretes (AACs) are a family of existing alternative construction materials that could reduce the current environmental impact of Portland cement (PC) production and utilisation. Successful applications of AACs can be found in...

Rheology of alkali-activated slag pastes: New insight from microstructural investigations by cryo-SEM

This study aims to interpret the early-stage rheology of alkali-activated slag (AAS) paste from microstructure perspectives. The microstructures visualized by cryogenic scanning electron microscopy (cryo-SEM) revealed the essential distinction between hydroxide and silicate-activated slag pastes. The hydroxide-based mixture showed typical...