Weihua Jin

Glascrete -Concrete with Glass Aggregate

Post-consumer glass represents a major component of solid waste, yet its use as an aggregate in concrete is problematic because of the strong alkali-silica reaction (ASR) between the cement paste and the glass aggregate. In a research project at Columbia University, the use of crushed waste glass as aggregate for concrete products was investigated. Fundamental aspects of ASR in concrete with glass aggregate were studied. It was shown that waste glass ground to U.S. standard sieve size No. 50 or smaller causes mortar bar expansions in the American Society for Testing and Materials C 1260 test of less than 0.1%, which is less than that of reference bars without any glass. Also, green glass does not cause any expansion to speak of, and finely ground green glass has the potential of an inexpensive ASR suppressant. Specific concrete products with glass aggregate are currently under development. These include concrete masonry blocks with 10% mixed color waste glass aggregate and glascrete products with 100% color-sorted glass aggregate for numerous architectural applications.

Design and Application of Concrete Tiles Enhanced with Microencapsulated Phase-Change Material

AbstractPhase-change materials (PCMs) have a high heat of fusion compared to that of traditional material, and for this reason, they are able to store and release larger amounts of energy at their transition temperature. The inclusion of PCMs in buildings has attracted much interest worldwide because of their ability to reduce building energy demand and increase indoor comfort. This paper presents the development and testing results of a concrete tile system with microencapsulated PCMs. The concrete tiles were cast for use in a high-performance house built for the Solar Decathlon China 2013 competition. The paper shows that the addition of PCMs reduced the overall compressive and flexural strength properties of the concrete. A more than 25% decrease in compressive strength was observed with the addition of 20% PCM per volume of concrete. However, a significant improvement in the thermal properties of the concrete tile PCMs was measured. The thermal energy storage capability of the PCM-enhanced concrete ti...

Dynamic Fracture of Cellular Cementitious Plates under Blast/Shock Loading

The response of cellular cementitious flat plates of circular shape with or without additives to shock wave loading has been investigated experimentally in the CCNY Shock Tube Research Facility. Cementitious cellular foam plates without and with polypropylene fiber reinforcement were tested. The traveling shock wave generated by the rupture of an aluminum diaphragm exits the shock tube, and subsequently expands and impacts the specimen in the form of blast wave. This interaction generates a reflection of the incoming shock wave propagating in the opposite direction and at the same time triggers waves within the cementitious specimen which eventually initiate the appearance of cracks. The experiments have indicated that the cellular plates develop cracks initially in the radial direction which then branch out into irregular directions leading to the break of the plates. These cracks start at the high stress concentration region close to the center or are aligned with pre-existing cracks. INTRODUCTION Material systems based on cement foams or cellular concrete are suited for developing applications which require energy dissipation. These brittle closed-cell foams with no permeability and high porosity exhibit a concave stress-strain relationship which is associated with irreversible compaction of the internal structure. Such materials are often used for attenuation of applied stresses such as, packaging, impact protection and blast mitigation. High amplitude stress waves produced in the material can cause significant damage, well before the structure shows signs of deflection (Eamon et al., 2004). The cellular microstructure of foams endows them with several favorable characteristics for use in developing protective arrangements, such as, a low weight and relatively constant strength at large strain associated with crushing of the microstructure (see Gibson and Ashby, 1988; Nian et al, 2003; KazemiKamyab et al., 2011; Nian et al., 2012). Developing material systems for energy dissipation using foams requires an understanding of the response under various transient loading such as air

Optical Characterization of Translucent Stone Subject to Degradation

Marble is an aesthetically appealing and thermodynamically ‘cool’ building material. However, when subject to weathering, marble building facade elements undergo surface degradation that result in changes to appearance and optical properties. These changes impact both the aesthetics and the thermal characteristics of the marble. This chapter highlights an experimental approach for the characterization of these changes, and numerical simulations for studying the corresponding impact on building energy performance when marble is used as an envelope finishing layer. Optical characteristics studied include gloss, solar reflectance, transmittance and absorbance. Changes in the optical characteristics of marble are used to assess the effect of degradation on it’s thermal properties.