P. Hari Prasad Reddy

Role of fly ash in control of alkali induced swelling in kaolinitic soils: a micro-level investigation

Surprising heave behaviour in non-swelling kaolinitic soils is experienced in the recent years due to alkali contamination. The ever increasing number of reported failure of structures highlights the need to plan proper control for alkali-induced swelling. Thus, the present paper focuses on the utilisation of fly ash to control the swelling of three kaolinitic soils contaminated with highly concentrated alkali solutions. Different percentages of class F fly ash was used to reduce the alkali-induced swelling in soils. Results indicate that the kaolinitic soils contaminated with different concentrations of alkali solutions exhibited remarkable changes in swelling behaviour. Reduction in swelling was observed in all three soils under consideration. A reduction in swelling of about 68% was noted in red earth when treated with 20% fly ash. However, it was found that 10% fly ash was sufficient to control the undesirable swelling in case of ball clay and china clay. X-ray diffraction and scanning electron microscopy studies enlighten the mineralogical and morphological changes that occured in alkali-contaminated kaolinitic soils stabilised with fly ash.

Iron impregnated biochars as heterogeneous Fenton catalyst for the degradation of acid red 1 dye

In the present work, Acid Red 1 (AR1) dye degradation by two heterogeneous Fenton catalysts, namely iron loaded rice husk biochar (Fe-RHB) and coir pith biochar (Fe-CPB) are studied. Biochar prepared from RHB and CPB were sonicated in the presence of ferric nitrate for the synthesis of Fe-RHB and Fe-CPB by incipient impregnation method. Effect of operational parameters such as pH, the dosage of catalyst, H2O2 concentration and temperature were examined. Characterization of the synthesized Fenton catalyst, Fe-RHB and Fe-CPB were analysed by SEM, EDS, XRD and XPS techniques. In Fe-RHB Fenton system, maximum dye removal efficiency of 97.6% and TOC removal efficiency of 84.2% were obtained at pH 3 for 50 mg L-1 of AR1 concentration, with 16 mM of H2O2 and 5 g L-1 of catalyst dosage within 120 min reaction time. Similarly, for Fe-CPB, maximum dye removal efficiency of 99.1% and TOC removal efficiency of 86.7% were obtained with 16 mM of H2O2 and 4 g L-1 of dosage for 50 mg L-1 of initial dye concentration at pH 3. The prepared catalysts can be reused for successive cycles as the catalyst materials are highly stable and have very less iron leaching property.

Ground granulated blast furnace slag to control alkali induced swell in kaolinitic soils

Abstract The failures of industrial buildings caused by alkali contamination of soils necessitate better understanding of their behaviour and proper control measures. In this paper an attempt has been made with GGBS to control the effect of alkali induced swell in kaolinitic soils. Three soils namely red earth, ball clay and china clay, which are non-swelling in nature and predominantly containing kaolinite mineral of varying amount, were considered for the study. Free swell tests were conducted on soils with 4N NaOH solution as pore fluid. The results showed that the dispersive nature of kaolinite clay particles under alkaline conditions along with mineral alterations resulted in the high swelling in kaolinitic soils. GGBS treated soils showed considerable reduction in swelling during alkali contamination and the percentage of GGBS required for controlling the swelling varied with the type of soil. The reduction in swelling with GGBS is attributed to the calcium alumina silicate mineral formations.

Effect of High Molar NaOH Solutions on Fly Ash

It is known that increased swell in soils with alkali solution can occur due to either increased cation exchange capacity and/or due to mineralogical changes. In the recent past lime is known to effectively control alkali induced heave in kaolinitic soils. Thus the efficiency of lime to produce pozzolanic compounds which aid in binding of soil particles increases in alkaline condition. In the search of cost effective pozzolanic materials to control the alkali induced heave, fly ash has gained due attention. Fly ash can be used if it is resistant to alkali and does not produce compounds that cause undesirable swelling. The paper attempts to understand the effect of different concentrations (1M, 2M and 4M) of sodium hydroxide (alkali) solution on the swelling and compressibility of fly ash. The results clearly indicate that no swell is observed with any concentrations of alkali solution even after allowing the samples to interact with alkali solution for longer duration. X-ray diffraction and SEM studies reveal that the pozzolanic compounds that form in fly ash due to alkali interaction can help in inhibiting the swelling. Thus fly ash seems to be a promising material to control the swelling in soils.