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Alkali silicate activated slag and class F fly ash‐based binders are ambient curing, structural materials that are feasible replacements for ordinary Portland cement (OPC). They exhibit advantageous mechanical properties and less environmental impact than OPC. In this work, five sodium silicate activated slag‐fly ash binder mixtures were developed and their compressive and flexural strengths were studied as a function of curing temperature and time. It was found that the strongest mixture sets at ambient temperature and had a Weibull average flexural strength of 5.7 ± 1.5 MPa and Weibull average compressive strength of 60 ± 8 MPa at 28 days. While increasing the slag/fly ash ratio accelerated the strength development, the cure time was decreased due to the formation of calcium silicate hydrate (C–S–H), calcium aluminum silicate hydrate (C–A–S–H), and (Ca,Na) based geopolymer. The density, microstructure, and phase evolution of ambient‐cured, heat‐cured, and heat‐treated binders were studied using pycnometry, scanning electron microscopy, energy dispersive X‐ray spectroscopy (SEM‐EDS), and X‐ray diffraction (XRD). Heat‐cured binders were more dense than ambient‐cured binder. No new crystalline phases evolved through 28 days in ambient‐ or heat‐cured binders.

Parents defend their young in many ways, including provisioning chemical defences. Recent work in a poison frog system offers the first example of an animal that provisions its young with alkaloids after hatching or birth rather than before. But it is not yet known whether maternally derived alkaloids are an effective defence against offspring predators. We identified the predators of Oophaga pumilio tadpoles and conducted laboratory and field choice tests to determine whether predators are deterred by alkaloids in tadpoles. We found that snakes, spiders and beetle larvae are common predators of O. pumilio tadpoles. Snakes were not deterred by alkaloids in tadpoles. However, spiders were less likely to consume mother-fed O. pumilio tadpoles than either alkaloid-free tadpoles of the red-eyed treefrog, Agalychnis callidryas , or alkaloid-free O. pumilio tadpoles that had been hand-fed with A. callidryas eggs. Thus, maternally derived alkaloids reduce the risk of predation for tadpoles, but only against some predators.

Sodium silicate activated, slag‐fly ash binders are potential alternative binders to Portland cement. In this study, the early age properties of slag‐fly ash binders namely, set time, and heats of reaction were investigated. Set time was investigated using a combination of two methods namely, the ASTM C403 penetration testing, and s‐wave ultrasonic wave reflectometry (SUWR). The discrepancy in set time identified by these two methods suggested the presence of a soft gel which eventually hardened with time. The composition of this soft gel was analyzed by suspending the chemical reaction of the binder after the soft gel formed, but before it hardened. In order to analyze the composition of the soft gel, selective chemical extractions were performed on the binder. 29Si Magic Angle Spinning‐Nuclear Magnetic Resonance (MAS‐NMR), and FTIR spectroscopy were performed on binders and extraction residues. The soft gel contained a modified calcium silicate hydrate gel (C–N–S–H where N=Na), with a short mean chain length and no observable Al incorporation. Orthosilicate units were also found to be present in relatively high proportions when compared to hardened binders at later ages.

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