Purpose
To reduce environmental impact caused by excessive use of ordinary Portland cement (OPC) and to mitigate scarcity of base materials such as natural coarse aggregate (NCA), industrial by-products can be carefully used as alternatives to OPC and NCA, in production of concrete. This paper aims to describe the performance of using ground granulated blast furnace slag (GGBS), fly ash (FA) as a complete replacement to OPC and ferrochrome slag (FCS) as replacement to NCA in production of novel FCS based alkali activated slag/fly ash concretes (AASFC) and evaluate their performance at elevated temperatures.
Design/methodology/approach
Two control factors with three levels each i.e. FA (0, 25 and 50 per cent by weight) and FCS (0, 50 and 100 per cent by volume) as a GGBS and NCA replacement, respectively, were adopted in AASFC mixtures. Further, AASFC mixture specimens were subjected to different levels of elevated temperature, i.e. 200°C, 400°C, 600°C and 800°C. Compressive strength and residual compressive strength were considered as responses. Three different optimization techniques i.e. gray relational analysis, technique for order preference by similarity to ideal solution and Desirability function approach were used to optimize AASFC mixtures subjected to elevated temperatures.
Findings
As FA replacement increases in FCS based AASFC mixtures, workability increases and compressive strength decreases. The introduction of FCS as replacement to NCA in AASFC mixture did not show any significant change in compressive strength under ambient condition. AASFC produced with 75 per cent GGBS, 25 per cent FA and 100 per cent FCS was found to have excellent elevated temperature enduring properties among all other AASFC mixtures studied.
Originality/value
Although several studies are available on using GGBS, FA and FCS in production of OPC-based concretes, present study reports the performance of novel FCS based AASFC mixtures subjected to elevated temperatures. Further, GGBS, FA and FCS used in the present investigation significantly reduces CO2 emission and environmental degradation associated with OPC production and NCA extraction, respectively.
The wax present in petroleum sludge, generated by the refinery and at the crude production sites, consists of paraffin hydrocarbons (C18 -C36) known as paraffin wax and naphthenic hydrocarbons (C30 -C60). The present study is aimed at the recovery of wax from the petroleum oily sludge by microwave assisted solvent extraction using Toluene/MEK mixture and subsequently de-crystallizing the wax. The process variables affecting the microwave assisted solvent extraction is optimized for recovery of wax. The simultaneous effects of process variables such as irradiation time (2 -10 minutes), solvent to sludge ratio (40 -80wt %), reactant volume (100-300ml) and microwave power (80-400W) on the recovery of wax were evaluated. A central composite design and response surface methodology were used for the optimization of the extraction process. Based on the central composite design, quadratic models were developed to correlate the extraction process variables with the responses and the models were analysed using appropriate statistical methods for analysis of variance. Optimization of process variables shows the maximum recovery of wax was about 79.57 % at 300 ml of reactant volume with microwave power output of 400 W at 7.6 minutes of retention time with 56.56 % of Toluene/MEK to sludge ratio.
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