Sewage sludge ash characteristics and potential for use in bricks, tiles and glass ceramics

The characteristics of sewage sludge ash (SSA) and its use in ceramic applications pertaining to bricks, tiles and glass ceramics have been assessed using the globally published literature in the English medium. It is shown that SSA possesses similar chemical characteristics to established ceramic materials and under heat treatment achieves the targeted densification, strength increases and absorption reductions. In brick and tile applications, technical requirements relating to strength, absorption and durability are achievable, with merely manageable performance reductions with SSA as a partial clay replacement. Fluxing properties of SSA facilitate lower firing temperatures during ceramics production, although reductions in mix plasticity leads to higher forming water requirements. SSA glass ceramics attained strengths in excess of natural materials such as granite and marble and displayed strong durability properties. The thermal treatment and nature of ceramic products also effectively restricted heavy metal leaching to low levels. Case studies, predominantly in bricks applications, reinforce confidence in the material with suitable technical performances achieved in practical conditions.</jats:p

Chloride ingress in concrete::limestone addition effects

This paper presents analysis and evaluation of experimental results of chloride ingress and chloride-induced corrosion resistance of concrete made with Portland limestone cement (PLC). The results were mined from 169 globally published studies from 32 countries since 1989, yielding a matrix of 20 500 data points. This study showed that chloride ingress in concrete increases with increasing limestone (LS) content, within the range permitted in BS EN 197-1:2011. However, this effect is less for PLC concrete mixes designed for strength equal to corresponding Portland cement (PC) concrete mixes than those designed on an equal water/cement (w/c) basis. The results also showed that Eurocode 2 specifications for chloride exposure, in terms of characteristic cube strength of concrete or w/c ratio, may need to be reviewed for the use of LS with PC. This study also investigated other influencing factors such as cement content, LS fineness, the method of producing PLC, aggregate volume content and particle size, combined chloride and sulfate environment, curing and exposure temperature. A comparison was made for the performance of PLC concrete in terms of pore structure and related properties, strength, carbonation and chloride ingress. Procedures to improve the resistance of PLC to chloride ingress in concrete are proposed. </jats:p

Municipal incinerated bottom ash (MIBA) characteristics and potential for use in road pavements

The characteristics of municipal incinerated bottom ash (MIBA) and its performance in road pavement applications is assessed through systematic analysis and evaluation of the global experimental data. MIBA has been used in unbound, hydraulically and bitumen bound forms. As unbound material, after processing, MIBA exhibits suitable mechanical properties for use as capping, fill and sub-base material, which has been successfully demonstrated in field testing. In hydraulically bound form, MIBA can be a viable aggregate component in subbase and roadbase layers at low to moderate contents, depending on the performance requirements and binder content. As bituminous bound aggregate in roads, the material can be fit for use at low contents, which is reinforced by a number of completed case studies, with the allowable MIBA fraction controlled by the voids contents, abrasion resistance and bitumen content requirements. Keywords: Municipal incinerated bottom ash, Road pavements, Sustainability, Recycled construction material