There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The Role of Inorganic Polymer Technology in the Development of ‘Green Concrete’

Carbon (C) is a crucial material for many branches of modern technology. A growing number of demanding applications in electronics and telecommunications rely on the unique properties of C allotropes. The need for microwave absorbers and radar-absorbing materials is ever growing in military applications (reduction of radar signature of aircraft, ships, tanks, and targets) as well as in civilian applications (reduction of electromagnetic interference among components and circuits, reduction of the back-radiation of microstrip radiators). Whatever the application for which the absorber is intended, weight reduction and optimization of the operating bandwidth are two important issues. A composite absorber that uses carbonaceous particles in combination with a polymer matrix offers a large flexibility for design and properties control, as the composite can be tuned and optimized via changes in both the carbonaceous inclusions (C black, C nanotube, C fiber, graphene) and the embedding matrix (rubber, thermoplastic). This paper offers a perspective on the experimental efforts toward the development of microwave absorbers composed of carbonaceous inclusions in a polymer matrix. The absorption properties of such composites can be tailored through changes in geometry, composition, morphology, and volume fraction of the filler particles. Polymercomposites filled with carbonaceous particles provide a versatile system to probe physical properties at the nanoscale of fundamental interest and of relevance to a wide range of potential applications that span radar absorption, electromagnetic protection from natural phenomena (lightning), shielding for particle accelerators in nuclear physics, nuclear electromagnetic pulse protection, electromagnetic compatibility for electronic devices, high-intensity radiated field protection, anechoic chambers, and human exposure mitigation. Carbonaceous particles are also relevant to future applications that require environmentally benign and mechanically flexible materials.

A review and analysis of microwave absorption in polymer composites filled with carbonaceous particles

Recent advances in understanding the role of supplementary cementitious materials in concrete

Concrete is very sensitive to crack formation. As wide cracks endanger the durability, repair may be required. However, these repair works raise the life-cycle cost of concrete as they are labor intensive and because the structure becomes in disuse during repair. In 1994, C. Dry was the first who proposed the intentional introduction of self-healing properties in concrete. In the following years, several researchers started to investigate this topic. The goal of this review is to provide an in-depth comparison of the different self-healing approaches which are available today. Among these approaches, some are aimed at improving the natural mechanism of autogenous crack healing, while others are aimed at modifying concrete by embedding capsules with suitable healing agents so that cracks heal in a completely autonomous way after they appear. In this review, special attention is paid to the types of healing agents and capsules used. In addition, the various methodologies have been evaluated based on the trigger mechanism used and attention has been paid to the properties regained due to self-healing.

https://biblio.ugent.be/publication/4144354/file/4144368.pdf

Self-Healing in Cementitious Materials—A Review

This paper presents basic information on the mechanical properties of steel fiber-reinforced, high-strength, lightweight concrete with compressive and flexural strengths up to 85.4 MPa and 11.8 MPa, respectively. The influence of steel fiber on modulus of elasticity and Poisson's ratio of concrete are investigated, and flexural fracture toughness is calculated. Test results show that the effect of fiber volume fraction (Vf) and aspect ratio (lfdf) on flexural strength and fracture toughness is extremely prominent, compressive strength is only slightly improved, and tensile/compressive strength ratio is obviously enhanced. It is observed that the flexural deflection corresponded to ultimate load increased with the increase of Vf and lfdf, and due to fiber arresting cracking, the shape of the descending branch of load-deflection tends towards gently.

Mechanical properties of steel fiber-reinforced, high-strength, lightweight concrete

The effect of hybrid fibers and expansive agent on the shrinkage and permeability of high-performance concrete

Mechanical properties of high-strength concrete after fire

The effect of limestone on the hydration and microstructural development of ultra high performance concrete (UHPC) with different levels of replacement (34%, 54% and 74% by volume) was investigated. Up to 54% replacement of cement by limestone the mixes showed better workability and higher compressive strength (170 MPa at 56 days for 54% addition) compared to a classical mix (155 MPa) with no limestone replacement. The kinetics of hydration were compared for different replacement levels using isothermal calorimetry. The phase development was quantified by X-ray diffraction with Rietveld method combined with thermal gravimetric analysis. The pore structure was examined by mercury intrusion porosimetry. The composition of hydration products was determined by scanning electron microscopy with energy dispersive X-ray analysis. The results showed that the hydration degree of the cement is increased from 39% for classical UHPC to 66% for the UHPC with 54% of limestone.

Effect of cement substitution by limestone on the hydration and microstructural development of ultra-high performance concrete (UHPC)

In this research the effects of nano-SiO 2 particles on the mechanical performance, hydration process and microstructure evolution of ultra-high performance cementitious composites were investigated by different methods. The results showed that the compressive and flexural strength increased with the increase of the nano-SiO 2 content up to 3% and due to agglomeration of nano-SiO 2 particles, the mechanical properties decreased slightly when the nano-SiO 2 content was more than 3%. The hydration process was accelerated by the addition of nano-SiO 2 . The porosity and the average pore diameter decreased with the increase of the nano-SiO 2 content and aging. The microstructure was more homogenous and dense for nano-SiO 2 specimens as compared to the control specimen. All of these improvements could be mainly attributed to the pozzolanic and filler effects of nano-SiO 2 .

Wei Sun

Papers

Mechanical properties of steel fiber-reinforced, high-strength, lightweight concrete

The effect of hybrid fibers and expansive agent on the shrinkage and permeability of high-performance concrete

Mechanical properties of high-strength concrete after fire

Effect of cement substitution by limestone on the hydration and microstructural development of ultra-high performance concrete (UHPC)

Effects of nano-SiO2 particles on the mechanical and microstructural properties of ultra-high performance cementitious composites