Mohammad Iqbal Khan

Ground Granulated Blast Furnace Slag

Ground granulated blast furnace slag (GGBS) is a by-product from the blast-furnaces used to make iron. Blast-furnaces are fed with controlled mixture of iron-ore, coke and limestone, and operated at a temperature of about 1,500°C. When iron-ore, coke and limestone melt in the blast furnace, two products are produced—molten iron, and molten slag. The molten slag is lighter and floats on the top of the molten iron. The molten slag comprises mostly silicates and alumina from the original iron ore, combined with some oxides from the limestone. The process of granulating the slag involves cooling of molten slag through high-pressure water jets. This rapidly quenches the slag and forms granular particles generally not bigger than 5 mm. The rapid cooling prevents the formation of larger crystals, and the resulting granular material comprises around 95% non-crystalline calcium-aluminosilicates. The granulated slag is further processed by drying and then grinding in a rotating ball mill to a very fine powder, which is GGBS.

Nanostructure and Microstructure of Cement Concrete Incorporating Multicementitious Composites

The nanostructural and microstructural behavior of concrete plays a decisive role in determining the properties of a material. The pore structure of paste, mortar, or concrete affects the behavior of the material and can give insight into the materials nanostructure and microstructure and their performance. Permeability and other durability-related properties of concrete are directly affected by pore structure. The pore structure also influences strength, modulus of elasticity, volume stability, and environmental resistance. Therefore, pore size, extent, and shape are of paramount importance in deciding the suitability of materials for practical applications, and the determination of pore structure has vital importance in evaluating the performance of concrete. This investigation was performed to assess and understand the influence of fly ash and silica fume as cement replacements on the pore structure of mortar. The pore structure study was conducted by using mercury intrusion porosimetry on the cement mortar incorporating fly ash and silica fume as partial cement replacements for the preparation of various combinations of blended systems. It was observed that incorporation of fly ash has a slight pore refinement effect, while inclusion of silica fume significantly improved pore refinement.

Comparison of Diffusion and Chloride Ion Penetration of High-Performance Concrete

This paper reports the results of an investigation of chloride ion penetration and diffusion for high performance concrete. Concrete was prepared incorporating pulverised fuel ash (PFA) and silica fume (SF) with various water-binder ratios. Chloride ion penetration was measured at various ages using rapid chloride permeability test in accordance with ASTM C1202-91. Based on experimentally obtained results, isoresponse contours for chloride permeability were developed showing the interactive and optimized effect between the various parameters investigated. Diffusion coefficient of concrete was determined applying Fick’s law of diffusion. The results show that the inclusion of PFA and SF reduced both chloride permeability and chloride concentration of concrete. It was found that rapid chloride permeability values were consistent with diffusion coefficient of concrete.

Effect of age and gender in the prevalence of excessive daytime sleepiness among a sample of the Saudi population

The aim of this study is to assess whether the effect of gender on the excessive daytime sleepiness (EDS) is influenced by two confounders (age and hours of sleep per night). A cross-sectional study was conducted at King Abdulaziz Medical City-Riyadh (KAMC-R). A total of 2095 respondents answered a questionnaire that included questions regarding gender, age, hours of sleep per night, and daytime sleepiness using the Epworth Sleepiness Scale (ESS). The prevalence of EDS was 20.5% (females 22.2%, males 19.5%, p-value = 0.136). The EDS did not differ between genders, age groups, or hours of sleep per night (<6 vs. ⩾6 h). However, stratified statistical analysis shows that the prevalence of EDS did differ according to gender (25.3% in females, 19.0% in males, p-value = 0.036) in respondents with shorter hours of sleep per night. EDS was strongly related to female gender and young age (ages ⩽ 29 years) in respondents with short hours of sleep. This study reveals that one out of five of the general Saudi population has EDS. The effect of gender on EDS appeared to be influenced by hours of sleep per night. High EDS strongly related to female gender with short hours of sleep.

Rice Husk Ash

Rice husk ash (RHA) is generated by burning rice husk. On burning, cellulose and lignin are removed leaving behind silica ash. The controlled temperature and environment of burning yields better quality of rice-husk ash as its particle size and specific surface area are dependent on burning condition. The ash produced by controlled burning of the rice husk between 550°C and 700°C incinerating temperature for 1 h transforms the silica content of the ash into amorphous phase. The reactivity of amorphous silica is directly proportional to the specific surface area of ash. The ash so produced is pulverized or ground to required fineness and mixed with cement to produce blended cement.

Ring Test for the Measurement of Restrained Shrinkage of Concrete

Shrinkage of repair material is the major factor inducing cracking in concrete repairs. Induced cracks in repair materials are due to restrained shrinkage. The ring test is commonly used to assess the potential for restrained shrinkage induced cracking due to its simplicity and versatility. The restrained ring test is becoming widely used as a standard test method to assess the potential for early-age cracking in concrete. In this investigation, a ring test set up was developed to measure the restrained shrinkage of various repair materials available in the local market. Keeping in view the importance of the local environment, two environment conditions were used; Lab Environment (Temperature 23±2°C) and the open environment of Riyadh. These environmental conditions were used taking into account the local environmental conditions. The samples were outside for almost one year and encountered all weather conditions of Riyadh. It has been observed that some materials although manufactured by highly reputed companies didnt comply fully in restrained shrinkage tests.

Nanosilica and its Future Prospects in Concrete

The implementation of nanotechnology in concrete has led to an active incorporation of nano silica in concrete in a global level. Different methods of nano silica production are available and vary from expensive to cost-effective routes. Nano silica particle sizes and their chemical and physical nature depend on the method of production. Several types of dispersed nano silica are recommended to be used in concrete due to practical reason. However, the dry powders of nano silica particles are difficult to be dispersed in concrete and require special types or family of nano superplasticizers. The effective addition of nS leads to C-S-H with improved cementitious properties.

Direct Tensile Strength Measurement of Concrete

The evaluation of the tensile strength and determination of the tensile stress-strain curve using indirect tests becomes approximate hence there is a necessity for exploring direct tensile strength measurement. This investigation is part of ongoing research on the development of direct tensile strength measurement. In this paper direct tensile strength test has been proposed and the results obtained have been compared with compressive strength and flexural strength. It has been found that results obtained are well comparable and relationships are similar to that proposed in earlier findings.

Role of broncho: alveolar lavage in approaching interstitial lung diseases

Bronchoalveolar lavage (BAL) is a simple and safe procedure performed during flexible bronchoscopy. BAL provides an important diagnostic tool in the diagnosis of various diffuse lung diseases. BAL fluid analysis for cell count and differential, bacteriology and cytology may suggest specific disease or give alternative diagnosis. Nevertheless, BAL is seldom useful as a “stand-alone” diagnostic test for various diffuse pulmonary diseases. Confident diagnoses can be obtained when clinical evaluation and high-resolution computed tomography of the chest (HRCT) findings are combined with BAL fluid analysis and/or transbronchial lung biopsy. BAL may also be helpful in determining the response to treatment and prognosis of interstitial pulmonary disease. This review is about the role of BAL in approaching patients with interstitial lung diseases (ILDs) and will describe the value of different cell patterns found.

Carbonation of High Strength Concrete

High strength concrete consisting of binary and ternary blended cementitious systems based on ordinary Portland cement, pulverised fuel ash and silica fume were investigated for carbonation. PFA up to 40% was used and to these blends 0, 5, 10, and 15% SF was incorporated as partial cement replacement. Results of carbonation of concrete cured in mist and air are reported. It was found that carbonation linearly increases with an increase in PFA content. Concrete with OPC only and concrete with 10% SF content showed insignificant change in carbonation when comparing air cured and mist cured concrete. The maximum carbonation depth observed for air cured concrete (containing 40% PFA) was less than 4 mm while in the case of mist cured concrete it was less than 2 mm. This depth is still far less than the cover of reinforced steel bars to cause corrosion.