Recent progress in low-carbon binders

Cracks in cement concrete composites, whether autogenous or loading-initiated, are almost inevitable and often difficult to detect and repair, posing a threat to safety and durability of concrete infrastructures, especially for those with strict sealing requirements. The sustainable development of infrastructures calls for the birth of self-healing concrete composites, which has the built-in ability to autonomously repair narrow cracks. This paper reviews the fabrication, characterization, mechanisms and performances of autogenous and autonomous healing concretes. Autogenous healing materials such as mineral admixtures, fibers, nanofillers and curing agents, as well as autonomous healing methods such as electrodeposition, shape memory alloys, capsules, vascular and microbial technologies, have been proven to be effective to partially or even fully repair small cracks. As a result, the mechanical properties and durability of concrete infrastructure can be restored to some extent. However, autonomous healing techniques have shown a better performance in healing cracks than most of autogenous healing methods that are limited to healing of cracks having a width narrower than 150 μm. Self-healing concrete with biomimetic features, such as self-healing concrete based on shape memory alloys, capsules, vascular networks or bacteria, is a frontier subject in the field of material science. Self-healing technology provides concrete infrastructures with the ability to adapt and respond to the environment, exhibiting a great potential to facilitate the creation of a wide variety of resilient materials and infrastructures.

Self-healing cement concrete composites for resilient infrastructures: A review

Drying shrinkage in alkali-activated binders – A critical review

Properties of fresh and hardened fly ash/slag based geopolymer concrete: A review

Durability of alkali-activated materials in aggressive environments: A review on recent studies

A review on concrete surface treatment Part I: Types and mechanisms

Microstructural changes in alkali-activated slag mortars induced by accelerated carbonation

Geopolymer concretes (GPCs) can be produced by chemical activation of industrial by-products and processed natural minerals that contain aluminosilicate. There have been a few demonstrative constructions built using of GPCs as a greener alternative choice to Portland cement concrete (PCC); unfortunately, there is no standard or specification of guidelines for the design of GPC mixtures. This is partially because of so many variables affecting GPC manufacture, such as the property of raw materials, type and dosage of activator and curing scheme. Despite the fact of convention of building industry, the lack of proper mixture design method limits the wide acceptance of GPC in industry. In this paper, a review on currently reported mixture design methods of GPC prepared with slag and fly ash is presented. The various methods are classified into three categories: target strength method, performance-based method, and statistical factorial model method. The difference in the procedures, advantages and disadvantages among those methods are discussed. It is recommended that a proper design method should be chosen according to actual production situation and performance requirement of GPC.

A review on mixture design methods for geopolymer concrete

This study investigates the effects of steel fiber and silica fume on the mechanical and fracture properties of ultra-high performance geopolymer concrete (UHPGC). Four volume fractions of steel fiber (0%, 1%, 2% and 3%) and four contents of silica fume by the mass of total binders (5%, 10%, 20% and 30%) were used. The mechanical and fracture properties evaluated include the compressive, splitting tensile and ultimate flexural strengths, modulus of elasticity, flexural behavior, fracture energy and stress intensity factor. In addition, the correlations among the compressive and splitting tensile strengths, and compressive strength and elastic modulus were studied. The results indicated the increase of steel fiber dosage resulted in the decrease of the workability, but the continuous improvement of mechanical and fracture performance of UHPGC. The empirical equations for predicting elastic modulus of conventional ultra-high performance concrete overestimated the elastic modulus of UHPGC, however some prediction formulas for the splitting tensile strength of PC-based concretes could be applied for UHPGC. Silica fume had a complicated influence on workability and hardened properties of UHPGC, which is strongly dependent on its amount. The inclusion of 10% silica fume induced the increase of the flowability, but the sharp degradation of the mechanical performance, while the specimens with 20% and 30% silica fume possessed the superior mechanical characteristic to that with 5% silica fume. The steel fiber dosage could be decreased without sacrificing the mechanical and fracture performance of UHPGC, via the increase of silica fume content.

Ning Li

Papers

A review on concrete surface treatment Part I: Types and mechanisms

Microstructural changes in alkali-activated slag mortars induced by accelerated carbonation

A review on mixture design methods for geopolymer concrete

Mechanical and fracture properties of ultra-high performance geopolymer concrete: Effects of steel fiber and silica fume

A review on surface treatment for concrete – Part 2: Performance