Sohan Singh

Permeability of self-compacting concrete made with recycled concrete aggregates and metakaolin

The results on the permeability properties of self-compacting concrete (SCC) containing fine recycled concrete aggregates (FRCA) and coarse recycled concrete aggregates (CRCA) are presented. The SCC mixes were prepared with 0, 25, 50, 75, and 100% replacement of fine natural aggregates (FNA) with FRCA whereas coarse natural aggregates (CNA) were 100% replaced with CRCA. To assess the durability properties of SCC made with FRCA and CRCA, tests such as rapid chloride penetrability test, initial surface absorption test, water penetration test, and capillary suction test were conducted. The microstructure has also been studied. The results indicate that replacement of CNA with CRCA significantly affect the properties of SCC whereas up to 50% replacement of FNA with FRCA has been found to marginally deteriorate the properties of SCC. Furthermore, the replacement of FNA with FRCA up to 25% has been found to improve the properties of SCC mixes up to some extent.

Carbonation resistance of self-compacting recycled aggregate concretes with silica fume

The paper presents the results of carbonation resistance of Self-Compacting Concrete (SCC) made with coarse recycled concrete aggregates and fine recycled concrete aggregates. To evaluate the carbonation resistance of SCC mixes, two different groups consisting of nine SCC mixes were prepared. The impact of coarse recycled concrete aggregates and fine recycled concrete aggregates has been quantified based on the observed performance of SCC mixes of Group-I whereas, the influence of Silica Fume (SF) has been observed on the SCC mixes of Group-II. The incorporation of SF in various SCC mixes not only improves the compressive strength, the carbonation resistance is significantly increased. It has also been observed with the scanning electron microscopy analysis that the incorporation of SF in SCC mixes containing different contents of recycled concrete aggregates, resulted in the production of SCC mixes, with higher/comparable performance to that of control SCC mix.

Flexural fatigue performance of concrete made with recycled concrete aggregates and ternary blended cements

Results of an investigation to evaluate the flexural fatigue performance of concretes made with fly ash, silica fume (SF) as partial replacement of Portland cement and 100% coarse recycled concrete aggregates (RCA) are reported. Flexural fatigue test data were obtained based on 168 static flexural tests and flexural fatigue tests conducted using Servo-controlled Actuator. The test data thus obtained were analysed and equations to estimate the flexural fatigue strength of concrete mixes were proposed. The probability distributions for the fatigue life of various concretes were also established. The flexural fatigue performance of various concrete mixes was assessed in terms of mean and design fatigue lives. The results obtained from the study show that flexural fatigue performance of concrete containing 100% RCA with 10% SF performed better than concrete containing 100% coarse natural aggregate.

Validation of carbonation behavior of self compacting concrete made with recycled aggregates using microstructural and crystallization investigations

Abstract The sustainable binary and ternary blends of Self compacting concrete (SCC) were prepared with replacement of natural fine aggregates (NFA) and natural coarse aggregates (NCA) with recycled fine aggregates (RFA) and recycled coarse aggregates (RCA) respectively sourced from construction and demolition (C&D). Accelerated carbonation tests were conducted using conventional acid/base method. The results indicate that with the increase in RFA and RCA content as replacement of NFA and NCA, decrease in the carbonation resistance of SCC has been observed. The addition of Metakaolin (MK) has been found in recompensing the respective loss in carbonation resistance up to some extent. For validating the results, microstructural and crystallization studies have been performed with the help of Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. In addition to above, compressive strength tests were also conducted for reference.

Abnormally Large Wooden Foreign Body Impacted in the Rectosigmoid Colon without Bowel Perforation

A 46 years old male presented with a history of assault and insertion of a long wooden object through his anus. Examination and radiological investigations of the patient revealed a 34x4.0 cm long wooden object in the rectosigmoid colon. The foreign body was delivered by colotomy under general anesthesia.