Yining Ding

Nano-carbon black and carbon fiber as conductive materials for the diagnosing of the damage of concrete beam

The nano-carbon black (NCB) and carbon fiber (CF) as electric conductive materials were added into the concrete. The effect of the NCB and CF on the mechanical properties and on the fractional change in resistance (FCR) of concrete was investigated. The relationships among the FCR, the strain of initial geometrical neutral axis (IGNA) and the beam damage degree were developed. The results showed that the relationship between the FCR and IGNA strain can be described by the First Order Exponential Decay function, and the internal damage of concrete beam was reflected by the relationship between damage degree and resistance.

Performance of alkali-activated mortars for the repair and strengthening of OPC concrete

Abstract Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. In the United States alone, the rehabilitation needs are estimated to exceed 1.6 trillion dollars over the next five years. Since the majority of the existing infrastructure is concrete based, this means that concrete infrastructure rehabilitation is a hot issue. Besides, the sooner concrete deterioration is tackled, the lower are the rehabilitation costs. The majority of current commercial repair materials are not cost efficient and some even present both technical and worrying environmental limitations. This chapter provides a literature overview on concrete repair materials, highlighting current problems faced by them. The potential of alkali-activated mortars to overcome those limitations is analysed.

Nanoparticles for high performance concrete (HPC)

Abstract: According to the 2011 ERMCO statistics, only 11% of the production of ready-mixed concrete relates to the high performance concrete (HPC) target. This percentage has remained unchanged since at least 2001 and appears a strange choice on the part of the construction industry, as HPC offers several advantages over normal-strength concrete, specifically those of high strength and durability. It allows for concrete structures requiring less steel reinforcement and offers a longer serviceable life, both of which are crucial issues in the eco-efficiency of construction materials. Despite the growing importance of nanotechnology, investigations into the incorporation of nanoparticles into concrete are rare (100 out of 10,000 Scopus concrete-related articles published in the last decade). It therefore remains to be seen how research in this area will contribute to concrete eco-efficiency. This chapter summarizes the state of current knowledge in the field and considers the influence of nanoparticles on the mechanical properties of concrete and its durability. It also includes the control of calcium leaching. The problem of efficient dispersion of nanoparticles is analyzed.

The suitability of concrete using recycled aggregates (RAs) for high-performance concrete (HPC)

Most studies related to concrete made with recycled aggregates (RA) use uncontaminated aggregates produced in the laboratory, revealing the potential to re-use as much as 100%. However, industrially produced RA contain a certain level of impurities that can be deleterious for Portland cement concrete, thus making it difficult for the concrete industry to use such investigations unless uncontaminated RA are used. This chapter reviews current knowledge on concrete made with RA, with a focus on the crucial importance of the presence of impurities, and how those aggregates are not suitable for the production of high-performance concrete (HPC). The potential of geopolymers to produce HPC based on high volume RA is also discussed.

Concrete with polymeric wastes

Abstract: The volume of polymeric wastes such as tyre rubber and polyethylene terephthalate (PET) bottles is increasing at a fast rate. An estimated 1000 million tyres reach the end of their useful lives every year and 5000 million more are expected to be discarded in a regular basis by the year 2030. Only a small part is currently recycled and millions of tyres are just stockpiled, landfilled or buried. As for PET bottles annual consumption is over 300 000 million units. The majority is just landfilled. This chapter reviews research published on the performance of concrete containing tyre rubber and PET wastes. Furthermore it discusses the effect of waste treatments, the size of waste particles and the waste replacement volume on the fresh and hardened properties of concrete.

Self-sensing concrete with nanomaterials

Abstract: Conductive concrete containing nano carbon black (NCB) and carbon fibre (CF) to enable the self-diagnosis of strain and damage was studied. The effect of NCB and CF on workability, mechanical properties and fractional change in resistance (FCR) in fresh and hardened concrete was analysed. The relationship between the FCR, the strain of initial geometrical neutral axis (IGNA) and the degree of beam damage was established. The results showed that the relationship between the FCR and the IGNA strain can be described by the First Order Exponential Decay function, and that the slope of this function reflects the sensitivity of conductive concrete. Based on the above relationship and damage mechanics theory, internal damage to the concrete is indicated by the relationship between the degree of damage and resistance. This self-sensing of strain in conductive concrete can be applied in monitoring damage to flexible components.