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Adding fibers is an effective way to enhance the printability and mechanical performance of 3D printable cementitious materials. Glass fibers are commonly used owing to their sound mechanical properties, high durability and affordable price. However, there is still a lack of systematic and in-depth research on the effects of adding glass fibers to cementitious materials. In this study, a series of 3D printable mortars with varying glass fiber content and water/cement (W/C) ratio were produced to evaluate their printability, flexural strength and compressive strength. The results showed that decreasing the W/C ratio generally has positive effects on printability and mechanical performance, whereas increasing the glass fiber content from 0% to 1% would substantially improve the extrudability, dimensional stability and buildability; increase the flexural strength by up to 82%; but decrease the compressive strength by up to 35%. Such large differences in the effects of glass fibers on the flexural and compressive strengths indicate significant material anisotropy. In fact, comparison of the strength results of printed specimens to those of un-printed specimens reveals that the printing process could increase the flexural strength by 98% but decrease the compressive strength by 47%. [ABSTRACT FROM AUTHOR]

With rapid urban development, natural aggregate resources have become scarce and a large number of ageing buildings are being demolished, which has resulted in a significant reduction in natural resources and a large increase in construction waste. Therefore, the reuse of solid waste, including waste powder and recycled aggregate, has attracted more and more attention. Additionally, as a prominent way to alleviate the urban heat island effect and manage stormwater runoff, pervious concrete has been widely studied and applied. In this paper, the effects of waste powder (fly ash, volcanic powder and blast furnace slag) and recycled aggregate (recycled concrete aggregate and recycled brick aggregate) on the mechanical properties, water permeability, water filtration and durability of pervious concrete are summarized and introduced, and some prospects are put forward. From the literature review, it can be found that adding the appropriate amount of solid waste or applying proper treatment methods to solid waste will not bring negative effects; rather, it would even improve the performance attributes of pervious concrete. Therefore, the use of solid waste in pervious concrete has great potential for urban construction and environmental protection. [ABSTRACT FROM AUTHOR]

• Micro Fe 3 O 4 and nano Fe 3 O 4 used together to produce EM wave absorbing mortar. • Adding micro and/or nano Fe 3 O 4 improved strength, packing and microstructure. • Co-addition of micro and nano Fe 3 O 4 has additive effect on EM wave absorption. Fe 3 O 4 (ferroferric oxide) has been proven to be useful for enhancing the electromagnetic (EM) wave absorption performance of cementitious materials. However, there are still few studies on the possible combined usage of micro Fe 3 O 4 and nano Fe 3 O 4 to further enhance the EM wave absorption performance and perhaps also the other performance attributes of cementitious materials. In this research, an attempt to utilize both micro Fe 3 O 4 and nano Fe 3 O 4 to produce EM wave absorbing mortar was made. A series of mortar mixes with varying amounts of micro Fe 3 O 4 and nano Fe 3 O 4 added were tested to investigate their combined effects on the workability, compressive strength, packing density, microstructure and EM wave absorbing properties. The results showed that the combined addition of micro and nano Fe 3 O 4 had little net effect on the workability, but significant positive effects on the compressive strength, packing density and microstructure densification, and more importantly, such combined addition could increase the EM wave absorption performance to higher than possible with only single addition of micro Fe 3 O 4 or nano Fe 3 O 4. [ABSTRACT FROM AUTHOR]