Flatwise and edgewise compression strengths of sandwich panel with silica aerogel mat

Facade of building are mainly made up from red clay brick and concrete block. However, both materials are having high thermal mass and promote high indoor thermal discomfort level. Therefore, it is necessary to invent new building material that have low thermal mass and able achieve strength required. Silica aerogel possesses properties of lightweight and low thermal conductivity as compared to other construction materials. In this study, sandwich panel with silica aerogel mat was studied where the properties of sandwich panel silica aerogel mat are rarely found in previous investigations. Before checking its reliability as thermal insulation panel, the mechanical properties of this panel was investigate. The panel was made-up by concrete wythes with type N mortar and the silica aerogel mats with different thickness. Both concrete wythes were casted and then attached together with silica aerogel mat as the cover. 3 types of panel with different insulation thickness were then tested for flatwise and edgewise compression test. From the results, it was found that core thickness of silica aerogel mat has less influence in flatwise and edgewise compression strengths of the sandwich panel. All specimens achieved minimum strength of type N mortar. Therefore, it is recommended to be used in construction that has equivalent application of type N morta

Compressive and Flexural Strengths of Mortar with Silica Aerogel Powder

Excessive usage of sand in construction industries has generated many environmental issues. Silica aerogel, is able to minimise environmental issues while providing thermal resistance for building materials. Silica aerogel has properties such as lightweight, nano-porous and very low thermal conductivity compared to sand in the mortar matrix. This paper studied the compression and flexural strengths of mortar with silica aerogel as a sand replacement. Cement to sand ratio of 1:3 was used and sand was replaced with silica aerogel in the volumes of 15%, 20% and 25%. 15% volume of sand replacement with silica aerogel powder was the optimum ratio as it possessed the highest strength during experimental work. All the specimens were able to achieve the minimum strength for Type N non load bearing wall with the optimum ratio of 15% volume silica aerogel powder. In conclusion, silica aerogel mortar achieved the minimum strength of type N mortar

Mechanical and Thermal Behaviour of Thermal Insulated Cement Mortar With Silica Aerogel

Cities or towns are having a higher temperature compared to the rural area and it is known as urban heat island (UHI). UHI indirectly induces the rising of indoor temperature. The heat tends to move from outdoor toward indoor by passing through building envelope. Consequently, human indoor discomfort level is increased. As a result, application of thermal insulator to the building envelope has been put in place to address the issue of thermal discomfort. There are various thermal insulators that are available and it is important to have thermal insulators to resist the heat flow from outdoor towards indoor. Conventional thermal insulation materials are mineral wool, EPS, XPS and cork. In the meantime, silica aerogel (SA) is a newly introduced insulation material. Silica aerogel was introduced with thermal insulation criteria where it possesses properties such as, lightweight, high specific surface area, high porosity, low density and high thermal insulation value. Therefore, silica aerogel was studied in this project in the form of powder and mat to produce silica aerogel mortar and silica aerogel sandwiched mortar respectively. The objectives of the study were to determine the mechanical properties and thermal properties of mortar incorporating silica aerogel powder and silica aerogel mat as well as to evaluate the thermal performance of the silica aerogel mortar panel and silica aerogel sandwiched mortar panel. Firstly, the experiment of mechanical properties was conducted to determine the mechanical properties and obtain the optimum ratio for silica aerogel powder mortar. Based on the results, 15% vol. silica aerogel (by replacing sand) was the optimum ratio for the SA powder mortar. Meanwhile, flatwise compressive test and edgewise compressive test were investigated for silica aerogel sandwiched mortar with three different thicknesses (9 mm, 12 mm and 15 mm) and 15 mm core thickness sandwiched mortar achieved highest flatwise compressive strength. Next, all the sandwiched mortar samples and silica aerogel mortar with optimum ratio were further prepared and used for thermal conductivity and thermal resistivity test which were conducted in laboratory, while field testing for thermal performance was carried out in open space under exposure of sunlight. It was concluded that 15% vol. silica aerogel mortar and silica aerogel sandwiched mortars were determined to have lower thermal conductivity than type N mortar (exterior, non-load bearing wall component) and possess better thermal insulation property compared to type N mortar. By replacing concrete block and red clay brick with silica aerogel mortar panel or silica aerogel sandwiched mortar panel, heat flow was expected to reduce and bring least indoor temperature fluctuation, hence maintain indoor thermal comfort level

A REVIEW ON THE BEHAVIOUR, PROPERTIES AND FAVOURABLE CHARACTERISTICS FOR THERMALLY INSULATED CONCRETE FOR TROPICAL CLIMATE

Tropical outdoor environment affects indoor temperature that consecutively interferes with human thermal comfort since most time is nowadays spent within buildings. A satisfactory indoor comfort can be achieved by providing a good building envelope. Therefore, the materials applied in constructing the building envelope should show characteristics of maintaining indoor temperature from the hot and humid outdoor environment utilizing heat transfer restriction through the thermal barrier implementation. In this regard, the thermal properties and performance of these materials are essential for building construction. Concrete, the main constituent in many building materials, has long been the key element in achieving human thermal comfort in the tropical climate. Nonetheless, there exists much room for improvement for conventional concrete in offering indoor thermal comfort, and thus leading to the need for innovative advances through the enhancement of thermal insulation properties by introducing novel additive materials. Therefore, this paper reviews the thermal insulation concrete including their thermal characteristics, classification, approach, added insulation material types, and usage in the context of tropical climates, concerning human thermal comfort. Key thermal properties needed for good thermal insulation performance have been discussed, from which beneficial behaviours relevant to thermal comfort are accordingly highlighted. Based on the reviewed materials and behaviours, recommendations for the most efficient method and characteristics to maintain indoor thermal comfort in tropical countries are consequently offered. Additionally, suggestions for future exploration are given where research gaps are identified. In summary, aerogel is the best thermal insulation material (lowest thermal conductivity, fire resistance and sustainable material) and incorporation of aerogel into concrete matrix able to produce thermal insulated concrete. In conclusion, thermally insulated concrete can reduce indoor temperature and therefore maintain indoor thermal comfort while capable of reducing electricity consumption for good thermal cycle sustainability

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

Background Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications. Methods We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC). Findings In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683–0·717]). Interpretation In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required. Funding British Journal of Surgery Society