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Calcium aluminate cement (CAC)—based strain hardening cementitious composites (SHCC) has been developed and used for the rehabilitation of sewerage pipelines. In addition to well-known microbiologically induced corrosion, CO2 concentration in the sewerage environment is high, which may cause significant carbonation of pipelines. Thus, this paper aims to investigate the effects of carbonation on the mechanical performance of CAC-based SHCC. Two types of CAC-based SHCC with different strength grades and a referenced OPC-based SHCC were prepared. The accelerated carbonation test was conducted in a carbonation chamber with a 5% CO2 concentration. The compressive and tensile behaviour of SHCC was tested first, and microstructure analysis, e.g., X-ray diffraction and scanning electron microscopy, was then performed. The results showed that CAC-based SHCC specimens exhibited robust strain-hardening performance as well as large deformation capacity in tension due to the fiber-bridging effect. Also, the compressive and tensile strength was significantly improved as well as achieving a higher tensile strain capacity after carbonation when compared with OPC-based SHCC. Microstructure analysis revealed that the metastable phases in carbonated CAC-based SHCC were converted into stable phases and calcium carbonate polymorphs, densifying the binder matrix. The obtained results of this paper may provide new insight into utilizing carbonation to avoid the unstable conversion of hydrates in calcium aluminate cement.

Humans are simultaneously exposed to phenols and phthalates (PAEs). However, the mixture effect of phenols and PAEs on the body size of twins is lacking. From 2016 to 2018, we recruited 228 pregnant twins and collected up to three urine samples. A total of 8 PAE metabolites and 7 phenols were detected in urine by liquid chromatography-tandem mass spectrometry. Chemical individual and mixture effects were estimated. Multivariable linear regression results presented the percentage change in twins' growth differences at one month old with maternal PAE and phenol exposure. These chemicals were positively associated with weight differences during the entire trimester. Moreover, the quantile g-computed model showed that increased urinary concentrations of all chemicals by one quartile were associated with a 22.85% (95%CI: 11.21-35.72%), 22.60% (95%CI: 12.31-33.83%), and 24.05% (95%CI: 13.11-36.05%) larger weight difference within twins in each trimester, respectively. Increasing all PAE metabolites and phenols by one quantile across the entire trimester, weight differences increased by 26.61% (95% CI: 15.79%, 38.44%), and height differences increased by 15.84% (95%CI: 3.92%, 29.13%). Co-exposure to PAEs and phenols may primarily play a role in twins' growth.

lum sludge is a typical by-product of the drinking water industry. Due to the rapid population growth and improved living standard, the amount of stockpiled sludge has increased significantly. In this study, the effects of limestone and alum sludge as cement replacement on the properties of mortar were investigated. 30% of cement was replaced with sludge and limestone, and the mass ratio of sludge to limestone was designed as 1:2, 1:1, and 2:1. The obtained results indicated that the mechanical performance of mortar samples, e.g., compressive strength, flexural strength, and water sorptivity, was improved with the combination of sludge and limestone at the mass ratio of 1:1 and 2:1. Through x-ray diffraction, thermalgravimetric analysis, backscattered electrons images, and mercury intrusion porosimetry tests, such an improvement could be explained by the fact that limestone reactivity raised in a limestone-sludge-cement system due to enrichment with aluminates, and the formation of hemicarboaluminate was promoted. The reaction between limestone and sludge, along with the pozzolanic reaction of sludge, contributed to improved strength and densified pore structure, especially for the refinement of capillary pores. Therefore, the combination of sludge and limestone might increase the cement substitution rate than using one of them alone. Refereed/Peer-reviewed