The past and future of sustainable concrete: A critical review and new strategies on cement-based materials

In corrosion environment, corrosion ions can easily penetrate from the surface into the inside of the concrete due to the porous structure of the surface; in this case, concrete can inevitably suffer from the damage. In this study, an attempt to use nano SiO2 (NS) and silica fume (SF) modifying cement mortar as a Surface Protection Material (SPM) was made, in order to promote penetration resistance of the whole system. SPM was coated on the surface of matrix, and then interfacial bond strength between matrix and SPM was measured; shrinkage consistency was also considered; the chloride penetrability of the system was examined as well. To reveal the mechanism, effect of NS and SF on pore structure, Interfacial Transition Zone (ITZ), hydration process, and compressive strength of SPM were investigated. The results show that matrix coated with SPM on the surface has a good integrity, with excellent interfacial bond strength and little difference in shrinkage, and chloride diffusion coefficient of the system was considerably declined, in comparison with the matrix, showing an excellent penetration resistance. The mechanism behind is that SPM, which was modified with SF-NS, shows the excellent impermeability, and this kind of material existing on the surface can noticeably obstruct the chloride ions penetrating into the inside. In cement hydration process, SF and NS can not only consume a large amount of CH to form dense C-S-H, but also exert the grading filling effect, resulting in the decline in porosity, the increase in density, the improvement in microstructure of ITZ, and the enhancement in mechanical performance. The findings can provide useful experience for the design of the cement-based materials servicing in high corrosion environment.

Nano-silica and silica fume modified cement mortar used as Surface Protection Material to enhance the impermeability

Municipal solid waste incineration (MSWI) bottom ash has gained increasing attentions for its friendly application worldwide, due to promotion of waste recycling One of the biggest concerns for incineration bottom ash (IBA) utilization lies in its elevated metal concentrations and leaching potential While challenges faced by the user are miscellaneous based on several aspects—regulations and rules, the heterogeneity of IBA sources, specific risks arisen from individual applications and/or mixed public views, etc Extensive knowledge on IBA characterization, existing treatment and application contributes to optimize life cycle of the bottom ash, herein enhancing the IBA management practices On the understanding that both feedstock and the process for incineration are various, properties, treatments and applications of the IBA are accordingly different Nevertheless, literature reviewed data indicate evidently that IBA, varying in its original resources and treatment facilities though, shares common geotechnical and chemical properties As the technology development on the IBA is dominated by these common properties, through which the proper treatment and application could be well determined In this review three perspectives were concentrated First, general properties of IBA eg heavy metals and their leaching potential, bulk components, particle size distribution and pH were investigated, whereby the general trends were indicated with collective plots Secondly, the existing status quo on IBA treatment methods and applications were investigated, suggesting a highest potential as low-strength aggregates Thirdly, toxicity studies and LCA on IBA as emerging research topics were also investigated, to further justify its application feasibility

Review of MSWI bottom ash utilization from perspectives of collective characterization, treatment and existing application

Utilization of lithium slag by wet-grinding process to improve the early strength of sulphoaluminate cement paste

A Literature Review on Cold Recycling Technology of Asphalt Pavement

Utilization of municipal solid waste incineration bottom ash in blended cement

For lack of laboratory and field performance data on stabilization of reclaimed asphalt pavement (RAP) aggregate and stabilized soil (S) for road bases and subbases construction, the influences of RAP/S ratio, cement and fly ash content, modifying agent (MA) on the compact, unconfined compressive strength, indirect tensile strength and water stability of the CIR mixtures were investigated. The experimental results showed that the maximum dry density and the optimum moisture content of the mixture changed significantly with the RAP/S ratio and cement-fly ash content. Unconfined compressive strength, indirect tensile strength and water stability were improved significantly by the addition of MA, and the water stability was improved by nearly 20% on average. Scanning electron microscopy(SEM) images indicated that MA accelerated the hydration of cement-fly ash system. Needle-like AFt and fibrous C-S-H gel were observed in the mixtures, which resulted in the cementation effect among the CIR mixture particles and a more compact microstructure. All these could be the cause of high strength of the CIR mixtures with MA.

Xiao-Bo Yin

Papers

Utilization of municipal solid waste incineration bottom ash in blended cement

Cement-fly ash stabilization of cold in-place recycled (CIR) asphalt pavement mixtures for road bases or subbases