The Development of a Low Carbon Cementitious Material Produced from Cement, Ground Granulated Blast Furnace Slag and High Calcium Fly Ash

This research represents experimental work for investigation of the influence of utilising Ground Granulated Blast Furnace Slag (GGBS) and High Calcium Fly Ash (HCFA) as a partial replacement for Ordinary Portland Cement (OPC) and produce a low carbon cementitious material with comparable compressive strength to OPC. Firstly, GGBS was used as a partial replacement to OPC to produce a binary blended cementitious material (BBCM); the replacements were 0, 10, 15, 20, 25, 30, 35, 40, 45 and 50% by the dry mass of OPC. The optimum BBCM was mixed with HCFA to produce a ternary blended cementitious material (TBCM). The replacements were 0, 10, 15, 20, 25, 30, 35, 40, 45 and 50% by the dry mass of BBCM. The compressive strength at ages of 7 and 28 days was utilised for assessing the performance of the test specimens in comparison to the reference mixture using 100% OPC as a binder. The results showed that the optimum BBCM was the mix produced from 25% GGBS and 75% OPC with compressive strength of 32.2 MPa at the age of 28 days. In addition, the results of the TBCM have shown that the addition of 10, 15, 20 and 25% of HCFA to the optimum BBCM improved the compressive strength by 22.7, 11.3, 5.2 and 2.1% respectively at 28 days. However, the replacement of optimum BBCM with more than 25% HCFA have showed a gradual drop in the compressive strength in comparison to the control mix. TBCM with 25% HCFA was considered to be the optimum as it showed better compressive strength than the control mix and at the same time reduced the amount of cement to 56%. Reducing the cement content to 56% will contribute to decrease the cost of construction materials, provide better compressive strength and also reduce the CO2 emissions into the atmosphere

Flexural behaviour of reinforced concrete beams with horizontal construction joints

In the present research, ten simply supported reinforced concrete beams having a rectangular cross-section were cast and tested up to failure under the action of two-point loads. Eight of these beams were designed to contain horizontal construction joints (HCJs) of different number and location in the beam while the other two beams had no construction joint which were referred to as reference beams for the sake of comparison of results. All the tested beams had been designed to fail in flexure and had the same amount and type of longitudinal and transverse reinforcement as well as similar concrete properties. The results of this series of tests have indicated that the presence of HCJs in reinforced concrete beams leads to a decrease in its ultimate loads and increase in its ultimate deflection. The values of the recorded ultimate loads ranged between 83% to 98% times that of the reference beam while the ultimate deflection ranged between 102% to 133% times that of the reference beam

Impact of the National Endoscopy Database (NED) on colonoscopy withdrawal time: a tertiary centre experience

Objective Colonoscopy withdrawal time (CWT) is a key performance indicator affecting polyp detection rate (PDR) and adenoma detection rate (ADR). However, studies have shown wide variation in CWT and ADR between different endoscopists. The National Endoscopy Database (NED) was implemented to enable quality assurance in all endoscopy units across the UK and also to reduce variation in practice. We aimed to assess whether CWT changed since the introduction of NED and whether CWT affected PDR. Methods We used NED to retrospectively collect data regarding CWT and PDR of 25 endoscopists who performed (n=4459 colonoscopies) in the four quarters of 2019. We then compared this data to their performance in 2016, before using NED (n=4324 colonoscopies). Results Mean CWT increased from 7.66 min in 2016 to 9.25 min in 2019 (p=0.0001). Mean PDR in the two periods was 29.9% and 28.3% (p=0.64). 72% of endoscopists (18/25) had CWT>6 min in 2016 versus 100% (25/25) in 2019, the longer CWT in 2019 positively correlated with the PDR (r=0.50, p=0.01). Gastroenterology consultants and trainee endoscopists had longer CWT compared with colorectal surgeons both before and after using NED. Conclusion NED usage increased withdrawal times in colonoscopy. Longer withdrawal times were associated with higher PDR. A national colonoscopy audit using data from NED is required to evaluate whether wide variations in practice across endoscopy units in the UK still exist and to ensure minimum colonoscopy quality standards are achieved

Shear performance of beam-column joints subjected to high loading rates

High loading rates may produce in structural frames due to some actions, such as explosions or debris impact. The response of structural members to such abnormal loadings should be investigated to provide comprehensive knowledge of their capability to resist impulsive forces. The beam-column joint is considered one of the most important structural components that significantly control the robustness and integrity of a structural frame. Hence, in the current study, eight full-scale specimens of two types of beam-column joints were tested under dynamic impact load to study their response to high rate load. These two types of joints were fin-plate and single angle-cleat joints. The tests were carried out using a drop hammer to apply an impact load on the specimens from different heights with different preloading conditions. The single angle-cleat joints exhibited a better response to dynamic loads with different impact height and preloading conditions than fin-plate joints in terms of resistance and ductility. Bolt shear failure was the dominant failure mode of the two types of the joints selected

Behaviour of moment resisting reinforced concrete frames subjected to column removal scenario

Researchers awarded a considerable attention to progressive collapse analysis in recent years to avoid the partial or entire failure of structures. General Service Administration guidelines (GSA) established the base to deal with such catastrophic failure. For multi-story building, these guidelines proposed column removal scenario in which one or more columns in different locations should be removed from a structure. Then, the response of entire structure with the column omitted should sustain the loading applied ensuring no global failure occurred. In this paper, three-dimensional reinforced concrete (RC) frame is constructed and analyzed using the commercial program SAP2000. Non-linear static analysis is employed to obtain Demand Capacity Ratios (DCR) for beams and the displacement of joint connecting beams to column in the selected frame. The response of moment resisting RC frame under column removal scenario is presented and discussed in terms of strength and displacements in critical locations in RC frame to evaluate the strength of such frame against progressive collapse

Is it time we split bowel preparation for all colonoscopies? Outcomes from a national survey of bowel preparation practice in the UK

Introduction: Adequate bowel preparation is a prerequisite for effective colonoscopy. Split bowel preparation results in optimal cleansing. This study assessed the bowel preparation regimes advised by endoscopy units across the UK, and correlated the differences with outcomes. Methods: Trusts in the UK were surveyed, with data requested between January 2018 and January 2019, including: the type and timing of preparation, pre-endoscopy diet, adequacy rates and polyp detection. Trusts were grouped according to the timing of bowel preparation. χ2 test was used to assess for differences in bowel preparation adequacy. Results: Moviprep was the first line bowel preparation in 79% of trusts. Only 7% of trusts advised splitting bowel preparation for all procedures, however, 91% used split bowel preparation for afternoon procedures. Trusts that split preparation for all procedures had an inadequacy rate of 6.7%, compared with 8.5% (p<0.001) for those that split preparation for PM procedures alone and 9.5% (p<0.001) for those that provided day before preparation for all procedures. Morning procedures with day-before preparation had a higher rate of inadequate cleansing than afternoon procedures that received split preparation (7.7% vs 6.5 %, p<0.001). The polyp detection rate for procedures with adequate preparation was 37.1%, compared with 26.4% for those that were inadequate. Conclusion: Most trusts in the UK do not provide instructions optimising the timing of bowel preparation prior to colonoscopy. This correlated with an increased rate of inadequate cleansing. Splitting bowel preparation is likely to reduce the impacts of poor cleansing: missed lesions, repeat colonoscopies and significant costs

Impact of high volume GGBS replacement and steel bar length on flexural behaviour of reinforced concrete beams

The Ordinary Portland Cement (OPC) is one of the major ingredient utilized for the manufacture of concrete. The manufacturing of cement includes the release of huge amounts of CO2 gas as a main contributor for greenhouse influence and global warming. Several researchers have investigated the characteristics of OPC concrete utilizing cementitious materials like fly ash, silica fume, and Ground Granulated Blast furnace Slag (GGBS) as replacement materials. The article aims to investigate experimentally the flexural behavior of concrete beams with GGBS. The experimental work was divided into three stages, the first one consists of six reinforced concrete beam specimens with (0%, 40% and 60%) of GGBS. During this stage, the used steel bars were 8 mm diameter and 500 mm in length. In the second stage, the length of the steel bars was reduced to 400 mm with the best mixture of (GGBS+OPC) that obtained from stage 1. In the third stage, the best length of steel bars was used with the best (GGBS+OPC) ratio to be tested at 7, 14 and 28 days from the date of casting. Consequences of this exploration suggests that replacement of OPC with 40 percent GGBS with 500 mm steel bar length can be used in reinforced concrete specimens as it shows comparable results relative to control mixtures (0% GGBS)

The Impact of Using Different Ratios of Latex Rubber on the Characteristics of Mortars Made with GGBS and Portland Cement

Preserving natural resources and implementing the concepts of sustainable engineering to approach the zero waste concept helped in reducing the detrimental environmental effects in the last two-decade. Proposed re-using of Ground Granulated Blast Furnace Slag (GGBS) as an alternate solution is to get rid of them and profit from them concurrently. In this process, GGBS is used as cement substitute material to enhance mortar characteristics. On the other hand, the required water for concrete mixture should be characterized by several characters, which similar to drinkable water, therefore, using of Latex Rubber as a water substitution reduces the demand for such water in the construction industry. In this project, percentages of GGBS that have been used were 0%, 10%, 30%, and 50% which compatible with (0, 10, 20 and 30) % of Latex Rubber. Suitable tests were performed to measure properties of mortar by GGBS and Latex Rubber such as setting time, compressive strength and Permeability test (Electrical resistivity). The results obtained indicate that the setting time reduced with increasing Rubber Latex in spite of increasing the proportion of water to binder. Additionally, increasing the Latex Rubber amount leads to decrease the compressive strength and electrical resistivity of mortars

Production of Ternary Blend Binder as an Alternative to Portland Cement

Environmental pollution and the relatively high cost of waste disposal have been a major focus for scientists around the world, leading researchers to find a solution to reuse waste materials in different applications. Additionally, landfills are considered one of the biggest crisis facing the Iraqi government. Therefore, this study aims to present a new ternary mixture that consists of OPC in addition to Pulverized Fuel Ash (PFA), Ground Granulated Blast Furnace Slag (GGBS) by utilizing it as a partial substitution of cement. A new ternary mortar mixtures containing four substitution levels of cement with GGBS and PFA (0%, 30 %, 50% and 70% by weight) were carried out. The Ultrasonic Pulse Velocity (UPV) and compressive strength tests were adopted to show the influence of GGBS and PFA on mechanical features of cement mortar. Findings indicated that, the compressive strength values were reduced with increasing the GGBS and PFA proportions at all curing ages. For 70% replacement, the compressive strength values were the lowest values comparison with that for control specimens. In contrast, the GGBS and PFA had a negative and positive impacts on the UPV of mortar depending on the substitution ratio. At 30 % substitution levels, the velocity value was enhanced, while other substitution ratios affected negatively on the UPV values

Influence of High Volume RHA on Properties of Cement Mortar

This work study the impact of partial cement replacement by high volume Rice Husk Ash (RHA) on some characteristics of cement mortar like compressive strength and flexural strength at different ages. In this research, RHA was used in three different ratios (20, 40, and 60)% as a cement substitution and the findings were compared with control mixture (0% RHA). The findings demonstrated that the replacement of cement by RHA reduced the compressive strength of all selected ratios and the increase in the content of RHA lead to reduce compressive strength comparative to control sample with 100% cement as a binder at all ages. However, the flexural strength results indicated that the RHA in 20% showed approximately same results as control sample at early ages while increasing the curing period lead to improve flexural strength. Increasing RHA higher than 20% lead to decrease Flexural strength at all selected ages