M.S.H. Khan

Chloride binding ability and the onset corrosion threat on alkali-activated GGBFS and binary blend pastes

This paper presents an experimental study to investigate the chloride binding ability of alkali-activated ground granulated blast furnace slag (GGBFS) and binary blend pastes. Free chloride and total chloride were measured to assess the chloride binding ability. pH measurement was performed to obtain [Cl−/OH−] ratio to assess the onset corrosion threat. The results showed that bound chloride significantly increased in GGBFS pastes and it gradually increased with GGBFS content in the binary blends. GGBFS paste mixed with deionised water and binary blend pastes showed corrosion risks although their free chloride contents were significantly low. The results further demonstrated that Ordinary Portland cement may be a more appropriate option than NaOH for activating GGBFS in terms of corrosion resistance.

Carbonation of Limestone Calcined Clay Cement Concrete

This study aims to investigate the carbonation resistance of limestone calcined clay (LC3) concrete. Ordinary Portland Cement (OPC) substitution rates considered were 15%, 30% and 45%. Low grade calcined clay was used with about 50% amorphous phase. Phenolphthalein indicator test was carried out in order to assess the carbonation depth of concrete exposed to natural and accelerated carbonation. Overall, results show that the carbonation front penetration is consistently increasing with the increase in OPC substitution rate Generally, LC3 concrete under performs compared to reference OPC concrete having similar 28 days compressive strength. At 30% OPC substitution rate, performance of LC3 concrete is close to that of OPC counterpart concrete, both having an average 28 days compressive strength of 36 MPa. Only a marginal increase in concrete cover would be enough to maintain the same service life. This is an important outcome showing that LC3 concrete with OPC substitution up to 30% is suitable for a large range of applications including outdoor exposure (assuming no other aggressive ions are involved). However, LC3 concrete with OPC substitution beyond 30% is not suitable in exposure condition where carbonation induced steel reinforcement corrosion can be an issue.

A Recent Study on Routing Protocols in UWSNs

Recent research has seen remarkable advancement in the field of Under Water Sensor Networks (UWSNs). Many different protocols are developed in the recent years in this domain. As these protocols can be categorized in a variety of ways according to the mechanisms and functionalities they follow, hence it becomes important to understand their principal working. In this research we have introduced three analysis methods; Clustering based, Localization based and Cooperation based routing by selecting some recent routing protocols in the field of UWSN and presented a comparative analysis according to the categories in which they lie. This research has been taken theoretically and is qualitative one. Also a detail analysis of their key advantages and flaws are also identified in this research.