Influence of Aluminium and Autoclaving Temperature on the Properties of Autoclaved Aerated Concrete

Autoclaved aerated concrete (AAC) prepared by the mixing of ordinary Portland cement, lime powder, sand, aluminium powder and water. This study covers the variation of physical, mechanical and functional properties of autoclaved aerated concrete with autoclaving temperature and aluminium content and compared with that of normal weight cement mortar sample. In this work, two dosage of aluminium content of 0.4% and 0.8% of the dry weight of ordinary Portland cement and three different autoclaving temperature of 160oC, 180oC and 200oC were used. AAC sample with 0.8% aluminium and 160oC temperature had unit weight of 1490kg/m3 which was lowest among all samples including the control or normal weight cement blocks. Weight reduction of AAC sample was 31.53%. AAC sample with 0.4% aluminium and 200oC autoclaving temperature gave maximum compressive and tensile strength of 19.4MPa and 1.81MPa respectively which were close to that of normal weight concrete and strength of AAC increased with autoclaving temperature and decreased with aluminium content. In this research, the functional propertiesof AAC, absorption capacity was much higher than normal weight concrete and this capacity was increased with aluminium content and with decreasing autoclaving temperature and unit weight of AAC. For AAC with 0.8% aluminium and 160oC temperature gave maximum water absorption capacity (=9.93%). Again, surface absorption rate was higher for first 12hours and with time it would be constant because of its saturated position. Journal of Engineering Science 12(3), 2021, 11-17

PHYSICAL AND ENGINEERING PROPERTIES OF PEAT SOIL STABILIZED WITH THE ADMIXTURE OF CACO3+RICE HUSK ASH DUE TO WATER INFILTRATION FROM SURROUNDING AREAS

Peat is a type of soil with high organic content, very low bearing capacity, and high uneven settlement. Some methods to improve soil have been applied to peat in order to make it strong enough for civilization-building foundation situated on it. Peat stabilization is a method that is continuously developed considering that the cost it needs is lower and this approach is more environmentally friendly compared to other methods. The admixture of lime (CaCO3) and Rice husk ash, a new ecofriendly stabilizer material, has been applied to peat soil and showed a good result. However, in studies conducted previously, the effect of water infiltration from surrounding areas of soil was stabilized was not involved as variable influencing the change of parameter. Based on that, this laboratory study was carried out to model the real condition in the field when the stabilization is performed and to identify the physical and engineering changes of peat soil in the 10th, 20th, and 30th days of stabilization in its border and middle parts, with the percentage of material stabilizer 5%, 10%, 15% and 20% of the unit weight of the initial condition of peat. The result of laboratory test shows that the addition of admixture of lime (CaCO3) and rice husk ash can improve the physical and engineering properties of peat soil are stabilized. Water infiltration occurred on peat soil is stabilized has not affected the physical and engineering properties of the soil. It can be seen from the physical and engineering properties of the border and central parts of peat soil is stabilized that still have a similar value. It is assumed to be caused by CaSiO3 gel formed still needs a longer duration to become stable gel. However, in this initial study it was known that the more stabilizers added, made the better the parameters of the stabilized peat soil.

Resolving the Multiplicity of Exoplanet Host Stars in Gemini/NIRI Data

The majority of stars have one or more stellar companions. As exoplanets continue to be discovered, it is crucial to examine planetary systems to identify their stellar companions. By observing a change in proper motion, companions can be detected by the acceleration they induce on their host stars. We selected 701 stars from the Hipparcos–Gaia Catalog of Accelerations (HGCA) that have existing adaptive optics imaging data gathered with Gemini/Near InfraRed Imager (NIRI). Of these, we examined 21 stars known to host planet candidates and reduced their archival NIRI data with Gemini’s DRAGONS software. We assessed these systems for companions using the NIRI images as well as Renormalized Unit Weight Error values in Gaia and accelerations in the HGCA. We detected three known visible companions and found two more systems with no visible companions but astrometric measurements indicating likely unresolved companions.

An Investigation on a Plane-Based Dynamic Calibration Method for the Handheld LiDAR Scanner

A plane-based dynamic calibration method had been proposed by the previous study for the GeoSLAM ZEB Horizon handheld LiDAR scanner. Only one preliminary test was presented. Therefore, three datasets in a calibration field were collected in this study on different dates and at different times on the same date to investigate the efficiency of the proposed calibration approach and calibration results. The calibration results for these three datasets showed that all average residuals were closer to 0, and all a posterior unit weight standard deviations of the adjustment were also significantly reduced after calibration. Moreover, the RMSE (root mean square error) of the check planes was improved by about an average of 32.61%, 28.44%, and 14.7%, respectively, for the three datasets. The improvement was highly correlated with the quality of the calibration data. The RMSE differences of all check planes using calibration data collected on different dates and at different times on the same date for calibration was about 1–2 cm and less than 1 mm, respectively. There was no difference in the calibration results, demonstrating the efficiency of the proposed calibration approach and the calibration results during the two different dates.

Qualitative Rating System for Drainability of Roadway Base Materials

Poor drainage of roadway base/subbase materials can lead to increased pore water pressure, reduction of strength and stiffness, and freeze-thaw damage. Base course drainability is dependent on physical properties of the material that affect its water flow and retention behavior including particle size distribution, fines content, density or porosity, the geometric and boundary conditions of the pavement system, and site-specific environmental conditions. Objectives of this project are to quantitatively assess permeability and water retention characteristics of representative roadway base materials, to derive predictive equations for indirect estimation of material properties that control drainability, and to develop and recommend rating systems for assessing more general base materials. Laboratory tests were conducted on 16 samples of materials used in or considered for use in roadway applications to determine grain size distribution, hydraulic conductivity, and soil-water characteristic curves. Results are correlated to grain size characteristics including percent gravel, percent fines, grain size indices (e.g., D10, D30), and unit weight. Procedures are provided to qualitatively assess drainability as “excellent,”“marginal,” or “poor,” from grain size, thereby offering a rationale to reduce pavement life cycle costs, improve safety, realize material cost savings, and reduce environmental impacts.

Sound Absorption Performance of Aluminum Silicate Fiber for Noise and Vibration Reduction of Distribution Transformer

In view of the low-frequency noise problem in urban substation, the sound absorption (SA) properties of aluminum silicate fibers (ASF) with different materials, unit weight, plate thickness and cavity thickness were tested in this paper. It was found that the high-purity ASF with larger unit weight, plate thickness and cavity thickness had larger low-frequency SA coefficient, which provided technical support for the development of new low-frequency noise reduction materials for substation.

Sustainable deployment of crushed concrete aggregates strengthened with cement and sand

Purpose: Paper assessed the feasibility of crushed concrete aggregates (CCA), a subsidiary of construction and demolition (C&D) waste, blended with cement and sand to form a composite for civil engineering field applications. Design/methodology/approach: The compaction and strength characteristics of CCA were observed by conducting Proctor compaction and California Bearing Ratio (CBR) tests. Different proportions of CCA, sand and cement were used. Moreover, the effect of curing period (0, 4, 7, 14 and 28 days) was also studied. In addition, regression analyses were performed to develop empirical expressions to predict the compaction and strength characteristics of the CCA composite. Findings: Increasing the CCA content up to 50% increases the maximum dry unit weight (MDUW) and decreases the optimum moisture content (OMC). However, on further increasing its content the MDUW decreases and OMC increases. Percent increase in the CBR value can go up to 412% if the CCA content is increased up to 50%. However, the percent reduction in CBR of about 20% can take place if 100% CCA content is used. Moreover, multiple regression shows that the experimental results are in good agreement with the predicted values. Research limitations/implications: The results obtained are purely dependent on the type of material. However, they are in favour of the used material as a probable option for road sub-base layer, and also for reducing burden on available natural resources. Therefore, it is recommended to conduct some initial tests to confirm the feasibility of the material. Practical implications: The proposed study will guide the design Engineers to choose CCA as one of the potential materials for road construction. Originality/value: It was observed that there is a need to maximize the utilization of C&D waste without making any compromise with its mechanical properties. So keeping that in view, the present study was conducted.

Forecasting the Compressibility Parameters of Gypseous Soil using Artificial Neural Networks

To ensure safe design of structures against settlement, it is necessary to determine the compressibility parameters of the underneath soil especially compression and rebound indices. In this paper, an approach to forecast the compressibility parameters of gypseous soils based on index parameters was developed using Artificial Neural Networks technique. Two equations were developed to estimate compression and rebound indices using back propagation algorithm to train multi-layer perceptron, in which good agreements were achieved. The input parameters used were: the depth, gypsum content, liquid limit, plastic limit, plasticity index, passing sieve No.200, dry unit weight, water content and initial void ratio. Two output parameters were determined including compression index and rebound index. A parametric study was also conducted to investigate the generalization and robustness of both models. The findings indicate that both models were reliable within the range of utilized data. It was found that gypsum content has the highest effect on the compressibility index followed by water content, plasticity index, dry unit weight and plastic limit, while other parameters have lower effect. The gypsum content has the highest effect again on the rebound index followed by passing sieve No.200, initial void ratio, plastic limit and plasticity index, while other parameters have lower effect.

Experimental Study on Light Weight Concrete Block with Double Core and Double Mesh Using Granulated Corn COB

A light weight concrete block using granulated corncob as an aggregate is investigated in this research work. Considering corn cob after removing the corn is said to be agricultural waste. Finding practical uses of this waste for manufacturing concrete block may preserve the environment and also allow green technologies. These concrete blocks are studied in terms of compressive strength, water absorption; density and unit weight were experimentally studied. The results obtained are submitted which shows that corn cob blocks have sufficient material properties for non-structural application in building for construction of partition walls. This is the alternative for blocks in expanded clay, expanded polystyrene, particles of cork, coconut coir etc. In this research a clay brick is compared as a reference block or control block. Nine specimen blocks were prepared in a size of 400mm x 200mm x 100mm and cured for 7 days, 14 days and 28 days and subjected to compressive strength test, water absorption test and density. The results are compared with conventional clay bricks. Corn cob blocks offered a good strength, low density and less water absorption. Keywords: Agricultural waste, compressive strength, durability, granulated corn

Karakteristik Beton Mutu 16,9 MPa Mengunakan 1% Kawat Bendrat dengan Variasi Panjang

The research aimed to determine the characteristics of the 16.9 MPa, using steel fibers (bendrat wire) with lenght variations in the concrete mixture 1% by volume-weight of the concrete. This research is an explanatory research with research questions are: how significant is the difference, and what are the characteristics. The total population of each treatment is 12 specimens with a sample of 5 specimens for compressive strength and 4 specimens for split tensile strength for each given treatment which is a random sample, specifically: A (reference concrete); B, C, D, and E for concrete with length variation an expressed as L/D fiber ratio of 50; 62.5; 75 and 87.5. The concrete material meets the standard. At the level of significance 0,05 indicates that the test data are normal distribution and uniform and the characteristics of concrete between reference concrete and concrete fiber different variance values. The unit weight between the reference concrete and the fiber concrete is slightly identical. The slump value decreases with increasing L/D fiber ratio. The concrete characteristics increase up to an L/D fiber ratio of 75. It generates a compressive strength of 19.47% of the design and 16.60% of the reference concrete (17,316 MPa). The split tensile strength is 2,753 MPa (22.29% higher than the design 2,251 MPa) and 18.83% of the reference concrete (2,317 MPa). The flexural strength was 3.638 MPa (18.01% of the 3.083 MPa design) and 1.97% of the reference concrete (3.144 MPa).