Effect of partial replacement of fine aggregate by internal curing materials on mechanical properties of concrete

Internal curing has long been utilized to decrease self-shrinkage and consequently the increased danger of concrete cracking prematurely. The measured mechanical characteristics of concrete were studied in five mixes, both with and without internal curing. Two of these mixtures have a 10% replacement rate, with one using ceramic and the other Attapulgite, while the other two have a 20% replacement, with one using ceramic and the other using Attapulgite, and the fifth is a reference mixture with no replacement for comparative reasons. With an increase of 27.93%, the ceramic combination with a 20% replacement rate is judged to have the highest compressive resistance, followed by the Attapulgite mixture with a 20% replacement rate with an increase of 34.2%. The results showed that the ceramic and Attapulgite internal curing purposes were highly effective, especially with a 20% replacement. The use of crushed ceramics and attapulgite as internal curing materials improves the characteristics of concrete.

Influence of pallet pattern on top-to-bottom compression performance of unitized loads

Environmental scaling factors estimate a corrugated container’s ability to withstand various conditions it will encounter during the storage and distribution process. In this project, we examined the compressive resistance of unitized loads using differing pallet stacking patterns. To simulate real-world failure scenarios in our laboratory tests, we used two different nominal board grades of single-wall C-flute regular slotted containers loaded with a plywood panel and bagged salt to direct the failure location to the bottom of the stack. Our results showed that the columnar aligned pattern provided the greatest compressive resistance and the interlocked stacking arrangement yielded the lowest of the patterns evaluated. Based on the study results, we calculated box compression retention multipliers for each pattern and compared them to scaling factors published by the Fibre Box Association.

Do the different species of fungi impact on mycocomposites compression behaviour?

Mycelium-based composites result from the growth of filamentous fungi on organic materials such as agricultural waste streams, like sugarcane bagasse, sawdust, coffee husks, coconut mesocarp and cotton. The morphology, density, tensile, flexural and compression strength of mycocomposites change according to the type of substrate, fungal species and processing technique. The objective of this study was to evaluate the mechanical behaviour in compression of different mycelium-based materials changing the fungal species. Substrates were formulated with wood sawdust and coconut endocarp, coffee grounds and wheat bran and incubated with isolates of the fungi Pycnoporus sanguineus, Ganoderma applanattum and Hexagonia hydnoides. Pre-myceliated sterile substrates were placed in cylindrical molds and incubated at 25°C for 7 days. After this period, the composites obtained were subjected to a temperature of 80 °C for 12 hours to stop fungi further development. Mechanical tests showed the relationship between the fungi and the compressive resistance (10% strain) of resulting composites, according to ASTM D1621. The analyzes indicated that the use of Pycnoporus sanguineus fungusprovides a composite with greater resistance to compression, which suggests the application of this mycocomposite in packaging, since the primary requirement of such use is to protect the content against damage.

Mycocomposites: looking for a viable alternative to EPS

Mycocomposites have received special attention from both academic and commercial environments. These materials give a new purpose to agricultural residues, bringing benefits to companies, society and the environment. Currently, they have been studied to replace synthetic materials such as polyester. However, its field of application is still very limited, making it necessary for more research to be carried out. In this work, mycocomposites were produced in two configurations: without jute and with two jute arranged at 1/3 of the thickness in relation to the surfaces perpendicular to loading plains during bending and compression tests. The base substrate used consisted of coconut mesocarp, white wood sawdust and wheat grain pre-myceliated by the fungus Pycnopurus sanguineus. Analysis by confocal microscopy showed that the fungus produced a network of mycelial hyphae capable of uniting substrate components and incorporated jute. Composites’ mechanical properties were evaluated from three-point bending tests and compression tests. The Shapiro-Wilk tests showed that all determined mechanical properties are normally distributed. The highest compressive resistance (10% deformation) was found in the mycocomposite without jute. The analysis of variance showed that the mean flexural strength of the two configurations analyzed did not present any statistically significant difference; despite this, the composite without jute proved to be more rigid. It was verified that the flexural strength of the produced mycocomposites is located between the values found for the expanded polystyrenes EPS 100 and EPS 150, but that their compressive strength was lower. At first, the materials produced in this work exhibited the necessary properties to be applied in simple pieces such as lampshades, packaging, and plant vases. However, it is still necessary that new studies are carried out to verify the feasibility of its application in the field of engineering, such as in civil construction panels, where EPS are used.

STUDY ON THE PROPERTIES OF POLYURETHANE-CEMENT COMPOSITE (PUC)

In order to study the properties of polyurethane cement composite (PUC) material, this paper has carried out the tests of compressive resistance, flexural resistance, axial tension, bonding and acid and alkali corrosion resistance of the material. The average compressive strength of the material is 59.3 MPa, the average flexural strength is 41.5 MPa, and the average axial tensile strength is 31.0 MPa. The bonding strength between the material and concrete in axial tension is 3.56 MPa, and that between the material and concrete in bending is 3.16 MPa. The failure interface of the two bond tests is not on the bond surface, indicating that the polyurethane cement composite (PUC) material has good bonding property. The chemical corrosion resistance test of polyurethane cement material showed no visible change on the surface of the material, indicating good chemical corrosion resistance.

Experimental Study on the Compaction and Deformation of Filling Gangue by Reducing Waste Gangue for Filling Mining

The coal mining technology of fully mechanized solid filling is an efficient and green mining method that integrates “sediment reduction” and “emission reduction.” However, the discharge of wasted gangue and surface subsidence are controlled by the amount of wasted gangue used in filling mining and the compaction rate of gangue filled into a goaf, respectively. To increase the consumption of wasted gangue and reduce surface subsidence, mixed gangue composed of equal-quality washed gangue and crushed gangue is proposed as a raw material for solid filling on the basis of gradation theory. Next, a screening experiment was performed to analyze the grain gradation of different specimens, and a compression experiment was executed to compare and analyze the compression characteristics. The results show that the nonuniformity coefficient of mixed gangue is 55.2 and the curvature coefficient is 1.53, which significantly improve the grain gradation of washed gangue. The degree of relative compaction of mixed gangue is 1.226, which is significantly lower than that of washed gangue, which is 1.33. The deformation modulus of mixed gangue is 23–135 MPa, which is better than that of washed gangue (26–100 MPa), indicating that the compressive resistance of mixed gangue is significantly improved. The case study of the Tangkou mine suggests that mixed gangue greatly promotes the consumption of wasted gangue and can effectively control the surface deformation.

Effect of residual stresses and cold-straightening on the compressive resistance of solid round steel columns

The objective of this research is to study the effects of residual stresses and cold-straightening on the compressive resistance of solid round steel columns. Thermal residual stresses in selected solid round sizes were determined from experimental study, finite element analysis, and previous research. In the experimental investigation, classical boring-out method using water-jet technology was applied on four samples with different diameters. Finite element models were constructed for the determination of thermal reidual stresses for columns with 12 different diameters. The results were then compared with results obtained from a recent study on the predictionof symmetrical residual stresses in solid rounds using X-ray diffraction method. For the non-symmetrical residual stresses arising from cold-straightening, the equation developed by Nitta and Thurlimann was adopted in the finite element modeling to study the effect of non-symmetrical residual stresses on the compressive resistance of solid round steel columns. The Finite Element Analysis has been conducted on different bar diameter (1.5 inch to 12 inch diameter) and length, as well as initial out-of-straightness.

Effect of residual stresses and cold-straightening on the compressive resistance of solid round steel columns

The objective of this research is to study the effects of residual stresses and cold-straightening on the compressive resistance of solid round steel columns. Thermal residual stresses in selected solid round sizes were determined from experimental study, finite element analysis, and previous research. In the experimental investigation, classical boring-out method using water-jet technology was applied on four samples with different diameters. Finite element models were constructed for the determination of thermal reidual stresses for columns with 12 different diameters. The results were then compared with results obtained from a recent study on the predictionof symmetrical residual stresses in solid rounds using X-ray diffraction method. For the non-symmetrical residual stresses arising from cold-straightening, the equation developed by Nitta and Thurlimann was adopted in the finite element modeling to study the effect of non-symmetrical residual stresses on the compressive resistance of solid round steel columns. The Finite Element Analysis has been conducted on different bar diameter (1.5 inch to 12 inch diameter) and length, as well as initial out-of-straightness.

Numerical Modelling of Axially Loaded Helical Piles: Compressive Resistance

Helical piles are foundation systems used to support compression, tension, and lateral loads. However, this type of piles was used around the world for more than 25 years. Its behavior, especially in Iraq, is still unknown and scare. The present study is carried out by analyses of this type of pile using the finite element method. Modeling of the helical pile geometry has been proposed using the finite element through the computer program Plaxis 3D. Parametric analyses were also performed. The main parametric study is the effect of a number of the helix, spacing between helix, the helix diameter, and helix configuration. The main conclusion is that as the number of helix increases, the bearing capacity increases further more than the higher the distance between helix, the higher bearing capacity. Maximum pile capacity with the case of three-helix increased by 115.4 %compared to the case without helix. Pile capacity with the case of spacing 3.5 D reached 130.7 % compared to the case of spacing 0.5 D. The value of displacement decreased with increasing spacing between the helices, while the value of displacement increased with the decrease in the spacing between the helices for top, middle, and bottom helix.