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Abstract

Mechanical and durability properties of concrete with cement replaced by finely grounded glass powder in high volume up to 60% were investigated. XRD and TGA analyses indicated that the fine glass powder reacted with calcium hydroxide to form calcium-silicate-hydrates. As such, the microstructures of concrete were more compact and homogeneous, especially at the interfacial transition zone. Concrete with cement replaced by 15% and 30% glass powder exhibited the highest strength increase and correspondingly the lowest porosity. Beyond a replacement of 30%, calcium hydroxide became insufficient for the pozzolanic reaction of glass powder. However, the high volume glass powder concrete retained distinct resistance against water and chloride ingress, due to the reduction in pore size and connectively. Reductions of 77%, 83%, 96%, 91% and 92% were observed respectively for water penetration depth, sorptivity, conductivity, chloride diffusion and migration coefficients in concrete with cement replaced by glass powder by 60%.

4. Conclusions

The use of high volume glass powder as cement replacement in concrete was proposed in this study. A comprehensive experimental program was conducted to investigate the microstructures, mechanical and durability properties of such concretes, focusing on the performances in the long term. After one year of curing, XRD and TG results indicated that calcium hydroxide had become significantly consumed by the pozzolanic reaction of glass powder where more than 30% cement was replaced by glass powder. As a result of this pozzolanic reaction, all mixes containing glass powder exhibited superior performances compared to the reference concrete. Despite a higher porosity in the mixes with high volume glass powder (45% and 60%), they still exhibit much better resistance to the transport of water and chloride ions, attributed to the refined pore system and densified transition zone. Compared with previous works, this study extended the application of recycled glass as supplementary cementitious material to a much larger amount, up to 60%. Besides the lower amount of raw materials, waste disposal, energy consumptions and carbon footprint, the advantages of high volume glass powder concrete have been demonstrated in this study by the better mechanical behaviors, and more distinctly by the higher durability performance. Also, in this study, a laboratory scale ball mill was used to reduce the glass particle size to the desired fineness. In practice, more efficient equipment such as industrial scale mill can be used for this purpose which could further reduce the energy consumption in the grinding.