Modification of the hydration products of hydrated cement paste by fly ash, β-cyclodextrin and fly ash-β-cyclodextrin composite

Abstract: Studies on the modification of the hydration products of fly ash (FA), β-cyclodextrin (β-CD) and fly ash-β-cyclodextrin (FA-β-CD) composite cement paste samples as hydration progressed were done using X-ray diffraction analysis, scanning electron microscopy and Fourier transform infrared spectroscopy. This paper investigates the effect of FA, β-CD and FA-β-CD composite on the hydration and pozzolanic reactions. It was evident from all the analyses that β-CD improved the hydration reaction from the 7  day hydration period, while improvement on pozzolanic reaction was revealed from the 28  day hydration period. The study contributed to the knowledge of FA performance as a composite with cyclodextrin and promoted the continued inclusion of FA in concrete

The effect of fly ash, β-cyclodextrin and fly ash-β-cyclodextrin composites on concrete workability and strength

Abstract: To increase the use of fly ash (FA) as a pozzolanic material in concrete, a composite was formed with an interaction of FA with β-cyclodextrin (β-CD). Further research was carried out in this article to study the effects of replacing cement with FA (30% and 50% by mass), β-CD (0.025%, 0.05% and 0.1%) and FA-β-CD composite on the workability and strength of concrete. Workability was assessed by means of the slump test and strengths were assessed using the compressive and split tensile strength tests. Higher combined contents of FA and β- CD resulted in increased workability of concrete of up to approximately 550 %. Furthermore, the inclusion of β-CD generally increased both the compressive and tensile strengths of the concretes not containing FA by up to 10 %. When combined with FA, the β-CD resulted in increased compressive strengths of up to 63 % and tensile strengths of up to 28 %, compared to the relevant pozzolanic concretes which did not include β-CD. The study contributed to the knowledge of FA performance using cyclodextrin and promoted the continued inclusion of FA in concrete, which in turn should reduce the environmental pollution resulting from FA

The effect of Fly ash, Beta-cyclodextrin and Fly ash-Beta-cyclodextrin composites on cement paste’s viscosity and setting times

Abstract: The possibility of increasing the usage of Fly ash (FA) in concrete has been a subject of interest and investigation by the authors. In the previous work, a composite of Fly ash- β- cyclodextrin (FA-β-CD) has been seen to have the tendencies of improving hydration reaction. To have further insight on how this composite can affect the mechanical properties of concrete, its rheological properties (viscosity and setting time) are assessed in this article. FA was used in percentages of 30 and 50, while β-CD was used in 0.025, 0.05 and 0.1 percentages. These percentages were based on the total percentage of cement (by mass). The results showed that increased in FA and β-CD contents, reduced the viscosity of the cement paste. Also, higher contents of FA and β-CD, reduced the water required for consistency and extended the setting times

The effect of dry wastewater sludge as sand replacement on concrete strengths

Abstract

Investigation of the fly ash - β cyclodextrin composite on concrete’s durability indexes

Abstract: Concrete quality can be assessed by its ability to withstand its design life without failing, which is a function of its strength and durability. The effect of fly ash (FA)-β- cyclodextrin (β-CD) composite on concrete’s durability indexes was investigated in this paper. Two durability index tests (oxygen permeability and sorptivity) were used for the assessment. FA (30% and 50% by mass of cement), β-CD (0.025%, 0.05% and 0.1%) and FA-β-CD composite were incorporated in the concrete mix. Twenty four different concrete mixes were investigated at 0.5 water-binder ratio (W/B) and 0.4 W/B. The tests were performed on the concrete samples after being cured for 28 and 90 days. The results showed that β-CD and FA-β-CD composite decrease oxygen permeability and sorptivity of concrete when used at optimum percentages

Structural Characterisation of four South African fly ashes and their structural changes with β-cyclodextrin

Abstract: This paper looks into the microstructural characteristics of some South African fly ashes and their structural changes with β-cyclodextrin so as to compare their structural responses to FA- βCD composite. Four different fly ashes, obtained from different power stations in South Africa were subjected to XRF, particle size distribution, XRD and FTIR analysis. FA-βCD composites were subjected to XRD and FTIR analyses. The XRF analysis showed that all the fly ash samples used are in class F with SiO2 + Al2O3 + Fe2O3 greater than 70 %. The average particle sizes of all the fly ash samples are less than 0.075 mm. The major mineral phase in all the fly ash samples investigated is Quartz (SiO2). The FTIR analysis shows Si-O-Si asymmetric and Al-O Symmetric stretching vibrations in all the fly ash samples. FA-βCD composites for all the fly ashes revealed additional upcoming peaks between diffraction angles (2θ) 100 and 250, which are not in their raw fly ashes..

Durability index of dry sludge incorporated concrete when used as sand replacement

Abstract: It is paramount to look for alternative ways of disposing dry sludge, as present disposal methods are environmentally unsustainable. Hence, the investigation on the possible inclusion of dry sludge in concrete. More specifically, this paper presents and discusses the effect of dry sludge used as a partial sand replacement on concrete durability indexes. Two durability indexes were assessed in this article, which are Oxygen permeability index (OPI) and chloride conductivity index (CCI). The OPI gives an indication of concrete’s resistance to the flow of water through continuous pores, at a given pressure and temperature, while the CCI provides an indication of concrete’s resistance to chloride infiltration. Dry sludge was used as a sand replacement, in the proportion of 0 %, 1 %, 3 % and 5 %. The 0 % sample served as the control sample. Three water cement ratios (W/C), of 0.67, 0.69 and 0.80, were assessed. The samples were water cured for 28 and 90 days before testing. The results showed that higher W/C and higher sludge replacement had a detrimental effect on concrete OPI. In addition, the CCI results show that dry sludge had a positive ionic reaction and good sulphuric attack resistance on concrete

Characterization of rice hull ash and its performance in turbidity removal from water

This study characterizes the locally obtained samples of rice hull ash and investigates its performance on turbidity removal from water. Four samples of this material were studied, namely, unwashed parboiled rice hull ash (UPRHA), washed parboiled rice hull ash (WPRHA), unwashed unparboiled rice hull ash (UUPRHA), and washed unparboiled rice hull ash (WUPRHA). Scanning electron microscopy (SEM), x-ray diffractometer (XRD), and Fourier infrared spectroscopy (FTIR) were carried out to characterize these samples. A filtration process was carried out to investigate the effectiveness of the rice hull ash medium in removing water turbidity. The XRD results showed the silica, which is present in the ashes, to be cristobalite, quartz, and tridymite. The silica contents of the UUPRHA and WUPRHA were observed to be 77.10% and 98.24%, respectively, while those of UPRHA and WPRHA were 79.07% and 94.97%, respectively. The SEM images showed agglomeration of ash particles after the ashes were washed. The washed RHA samples showed improved pH, a good percentage of turbidity removal (<5 NTU) from water sample. Washing RHA with distilled water increased the efficiency of RHA in turbidity removal from water and regulated water pH to an acceptable range

Prediction of the torsional capacity of CFDST steel columns using extreme gradient boosting tree-based machine learning technique

This study presents an eXtreme Gradient Boosting (XGBoost) algorithm for predicting the torsional capacity of circular Concrete-Filled Double Skin Tubular (CFDST) steel columns under pure torsion. Utilizing a dataset of 806 columns generated through non-linear finite element analysis, the of XGBoost model outperforms existing empirical models with R² values of 99.5% (training) and 97.6% (testing). SHapley Additive exPlanations (SHAP) framework aided in interpreting predictions at both global and local levels. Key influencing variables include concrete compressive strength, outer steel tube yield strength, outer steel tube thickness, and inner steel tube thickness. The study highlights the effectiveness XGBoost as a promising alternative to traditional empirical models for accurate torsional capacity predictions in CFDST steel columns