Average Compressive Strength Research Articles

Radiological characteristics of Self-Compacting Concretes incorporating fly ash, silica fume, and slag

This article presents the results of a comprehensive study investigating the hypothesis that higher concentrations of natural radionuclides, that are harmful to human health, may be present in Self-Compacting Concretes (SCCs) due to its higher powder material content compared to conventional concretes. The fresh (slump-flow, T500 time, V-funnel) concrete and compressive strength of SCCs prepared by replacing Portland cement with fly ash (FA), silica fume (SF), and ground granulated blast furnace slag (GGBFS) in the respective range of 5%, 12.5%, and 20% were determined. The radionuclide activity concentration of all solid concrete components and SCCs were determined using the gamma spectrometry method. Radioactivity analyses including the calculation of the activity concentration index and annual effective dose equivalents were also performed. The findings showed that the specimens with the highest average compressive strength at the end of 120th day were, respectively, SF (54.2 MPa), FA (52.2 MPa) and GGBFS (46.1 MPa) added to the SCC. The obtained concentration of the Radium-226 value (41.1) of 20% UK with added SCC was 1.8 times higher than the control concrete (22.7) and 2 times higher than 20% SF added SCC (19.7). The highest Radium equivalent activity (Raeq) values were FA20 (89.52), GGBFS20 (72.05), control concrete (70.86) and SF20 (68.01). It was determined that the FA selected for the study exceeded the limit specified for structural material (3.38 > 1) and fell in the radiologically hazardous class. It has been proven that SF can be used as a radioactivity reducing material of concretes. The results revealed that the research hypothesis was confirmed in terms of FA.

Cell Viability Assay and Surface Morphology Analysis of Carbonated Hydroxyapatite/Honeycomb/Titanium Alloy Coatings for Bone Implant Applications.

In this work, carbonated hydroxyapatite/titanium alloy (CHA/Ti) and carbonated hydroxyapatite/honeycomb/titanium alloy (CHA/HCB/Ti) plates were coated using the electrophoretic deposition dip coating (EP2D) method. Analysis of cell viability and surface morphology of CHA/Ti and CHA/HCB/Ti coatings were carried out using the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and scanning electron microscopy (SEM), respectively. In a previous study, the thickness and average compressive strength values for the CHA/Ti and CHA/HCB/Ti plates were about 63–89 μm and 54–75 MPa, respectively. The result for thickness and compressive strength in this research followed the thickness and compressive strength parameters for coating in bone implants. In this work, the cell viability for incubation times during 24 h and 48 h of CHA/Ti plates is demonstrably superior to that of CHA/HCB/Ti plates, respectively, where the cell viability for CHA/Ti plates increased to ((67 ± 2)%) after incubation for 48 h. According to the one-way analysis of variance (ANOVA), the p-value was <0.05, indicating a significant difference in the average cell viability value across the three groups. Furthermore, the surface of CHA/Ti is not changed after the coating process. These results will yield many positive biomedical applications, especially in bone implants. Overall, CHA/Ti and CHA/HCB/Ti plates can be considered candidates for biomedical applications based on an analysis of surface morphology and cell viability.

Study on Multisize Effect of Mining Influence of Advance Speed in Steeply Inclined Extrathick Coal Seam

Abstract Aiming at the multisize effect of mining in steeply inclined extrathick coal seam, taking the fully mechanized top-coal caving mining in B3+6 coal seam +425 level in the south of Wudong coal mine as the background, this paper studies the mining stress evolution law under the influence of advancing speed, analyzes the mechanical characteristics of coal samples under the mining action of steeply inclined extrathick coal seam, and completes the multisize effect study of mining in steeply inclined extrathick coal seam. The results show that the stress change theory of fully mechanized top-coal caving mining in steeply inclined seam is deduced, and the loading and unloading stress of fully mechanized top-coal caving mining is positively correlated with the advancing speed of the working face. The numerical simulation experiment shows that the ideal advancing condition increases with the advancing speed of the working face, and the cyclic loading and unloading amplitude under the mining stress path increases, the cyclic times decrease, the main influence area increases, and the acting time decreases. The peak value of mining stress, the width of the plastic zone, and its elastic energy under high-speed propulsion are obviously larger. A method of mechanical behavior analysis of coal samples is proposed, which takes the mining stress path of the numerical simulation experiment as the indoor scale loading and unloading stress path of coal samples. The average compressive strength of coal samples under the mining stress path increases with the advancing speed of the working face, and the damage degree of coal samples increases with the advancing speed of different stress paths. The input strain energy of coal cyclic loading and unloading increases with the increase in the advancing speed of the stress path. The input strain energy of the coal sample has obvious linear relationship with the advancing speed of different paths. The research results can be used for reference in the study of multisize effect of mining impact of advancing speed.

Influence of moisture absorption on mechanical properties and damage mechanisms of three-dimensional six-directional braided composites under hydrostatic pressure

Fibre-reinforced composites have shown a growing interest in pressure-resistant materials for deep-sea use due to their excellent properties. This paper presents the influence of the moisture absorption on the mechanical properties and damage mechanisms of three-dimensional six-directional (3D6D) braided composites under hydrostatic pressure. The bisphenol A epoxy resin, bisphenol F epoxy resin, and hydrogenated bisphenol A epoxy resin, are chosen. SEM and X-ray Micro-CT are employed to investigate the moisture absorption, tensile and compressive damage before and after subjecting to the hydrostatic pressure. Results show that the bisphenol F carbon/epoxy composite has the lowest porosity at 0.082% among the three composite materials. The average moisture absorption was the lowest at 0.3755%. Furthermore, moisture is mainly transported along micro cracks in the matrix and the fiber-matrix interface under hydrostatic pressure. After the composites absorb moisture, the average tensile strength retention rates of bisphenol A carbon/epoxy composite, bisphenol F carbon/epoxy composite, and hydrogenated bisphenol A carbon/epoxy composites drop to 88.282%, 76.34%, and 66.43%, respectively. Moreover, their average compressive strength retention rates drop to 53.15%, 74.26%, and 83.45%, respectively. The tensile and compressive strengths of the 3D6D braided composites decreased significantly after moisture absorption, mainly due to fiber-matrix debonding and matrix cracking.

Drilling Waste Disposal Technology Using Soil Cement Screens

Known technological solutions for well drilling waste utilization are analyzed. The technological decision of the device of storage of drilling waste from soil-cement elements with the device of a covering from soil-cement is offered. It is proposed to fill the repository with waste in layers of drilling mud, site soil, using a layer of composition for neutralization with the use of ash burning wood residues. The composition is proposed to be prepared near storage facilities. It is proposed to make the neutralizing composition periodically in the sludge storage as they are filled. In the case of a high level of sludge contamination with petroleum products, sorbents are added in addition to filling the storage. The thickness of the layers is chosen based on optimal humidity. It is offered to add ash from the Mykolayiv thermal power plant in the amount of 5 wt.% By weight of cement when installing the walls and covering the sludge storage from soil cement. It was found that with increasing the shelf life of samples in water to 270 days increases the average compressive strength of soil cement samples without additives and with the addition of the appropriate percentage of fly ash by more than 7%.

Microbially/CO2-derived CaCO3 cement strengthens calcareous sands and its cementation mechanism

In this text, a method to use CO2 for the treatment of calcareous sand is presented. Carbon dioxide solidification-bacteria (Streptomyces microflavus) was obtained by screening and applied to the mechanical strengthening of calcareous sand through a microbial mineralization/carbonization process. Experiments in both liquid phase and sand were carried out. The optimal mass ratio of carbon dioxide solidification-bass cteria to calcium oxide was found to be 2:1. The optimal dosage of bacterial powder was 30% of the total dry sand mass. Using the optimal recipe, the average uniaxial compressive strength of treated sand columns was 3.67 MPa and the average permeability coefficient was 4.90 × 10−3 cm/s. Compared to the other microbial induced carbonate precipitation (MICP) approaches, the proposed method does not release harmful by-products such as ammonia. The chemical composition and microstructure of the treated calcareous sand were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results showed that the CO2 carbonized product contained mainly calcite.Graphical abstract

Hierarchical Porous Ceramics with Distinctive Microstructures by Emulsion-Based Direct Ink Writing.

Hierarchical porous materials are ubiquitous in nature and have inspired the fabrication of cellular structures for a multitude of applications. As an extrusion-based 3D printing technique, direct ink writing (DIW) allows for customizable design and accurate control of printed structures. Recently, its combination with colloidal processing methods used for bulk porous ceramics, such as emulsion templating, has further extended its capability of fabricating porous ceramics across multiple length scales. In light of the recent development, the ink formulation for emulsion-based DIW can be further explored, and there is still a need for a better understanding of the structure-property relationship. Herein, we introduce two types of gelling additives, i.e., poly(ethylenimine) (PEI) and Pluronic F-127, respectively, into particle-stabilized emulsions and fabricate hierarchical porous alumina lattices by DIW. We discover that the two gelling additives can lead to distinctive microstructures due to their different gelling mechanisms. Moreover, the 3D printed hierarchical porous ceramic lattices are found to exhibit a potential energy absorption property. The effects of ink formulations, including gelling additives and solid loading, on ink rheology, microstructure, and mechanical properties are investigated. The 3D printed hierarchical porous ceramic lattices exhibit a high average porosity of 73.7%-79.3% with an average compressive strength of 1.53-9.61 MPa and a specific energy absorption of 0.33-2.67 J/g. Featuring two distinctive microstructures with tunable structural features and mechanical properties, the 3D printed hierarchical porous ceramics in this study have potential in many applications, including lightweight structures, tissue engineering scaffolds, filtration, etc.

Pengaruh Penggunaan Agregat Kasar dan Halus dari Quarry Siulak Deras dan Quarry Sungai Rumpun di Kabupaten Kerinci terhadap Kuat Tekan Beton Normal

In Kerinci Regency, especially around areas of Gunung Tujuh and Siulak areas, people generally use materials from Sungai Rumpun quarry and Siulak Deras quarry for the concrete mixture. A preliminary test by organic impurity test showed that the organic substances in the aggregate from the Sungai Rumpun quarry had a high organic content, while the aggregate from the Siulak Deras quarry had a low organic content. Therefore, this study aims to investigate the characteristics of the aggregate from Sungai Rumpun quarry and the Siulak Deras quarry and to determine the effect of the use of coarse and fine aggregate from both quarries on the compressive strength of concrete. This study is an experimental research that is conducted at the Civil Engineering Laboratory of the Padang Institute of Technology (ITP). In this study, the tests for physical properties of coarse and fine aggregates are conducted, then samples for the concrete compressive test are prepared, and the compressive strength test is carried out. Based on the results of this study, it can be concluded that aggregates from the Sungai Rumpun quarry are not recommended to be used for the concrete mixture of normal strength concrete (fc'=20 MPa), because the results of the compressive strength test showed that the average compressive strength does not reach the designed compressive strength (fc'). On the other hand, the aggregates from the Siulak Deras are recommended to be used for the concrete mixture of normal strength concrete because the compressive strength reaches the designed compressive strength.

Experimental study of the compressive properties of a wood–plastic composite at different temperatures

AbstractWood–plastic composites (WPCs) are environmentally friendly materials with good weather resistance and low cost. To investigate the feasibility of their use in different environments, a WPC was designed and subjected to a uniaxial compression test at seven temperatures to obtain the failure mode, uniaxial compressive strength, elastic modulus, proportional limit stress, peak stress, and ultimate strain. The results showed the following. The failure modes of the WPC specimens at various temperatures were mainly shear compression failure, double shear failure, and end compression failure. The uniaxial compressive strength and elastic modulus decreased with increasing temperature. Specifically, at temperatures of −60°C, 20°C (normal temperature), and 60°C, the WPC had an average compressive strength of 73.55, 33.7, and 13.51 MPa, respectively, and an average elastic modulus of 7819.11, 6141.71, and 2650.17 MPa, respectively. In terms of the WPC's stress–strain relationship, at a temperature greater than the normal temperature, the WPC had a small peak stress but good ductility; at the normal temperature and below, the WPC had a large peak stress but poor ductility. Based on these findings, the experimental phenomena and characteristic constants were analyzed to establish models of factors that reduce the uniaxial compressive elastic modulus and compressive strength of WPC at different temperatures, to provide a theoretical basis for the mechanical calculations for the application of WPC in various extreme environments.

Gelatin-Agar Liver Phantom to Simulate Typical Enhancement Patterns of Hepatocellular Carcinoma for MRI

Background: Hepatocellular carcinoma (HCC) is one of the most common cause of cancer-related deaths worldwide. The objective of this study is to detect the various stages of HCC through the utilization of a dynamic liver phantom with MRI. Methods: Three liver phantoms composed of different gelatin concentrations (2.5%wt, 4.0%wt, and 5.0%wt) and fixed agar concentrations were used. The HCC samples consisted of agarose and glycerol and were of varying sizes (0.5,1.0, and 2.0cm). The chemical, mechanical, electrical, and imaging properties of the phantoms were examined. The consistency of T1 and T2 signal intensities over a six-week period was studied. In addition, dynamic contrast-enhanced MRI was used to detect the HCC samples through the Dixon sequence. Results: The gelatin concentration of 5%wt was the most stable in regard to density, exhibited the lowest average compressive strength of 0.22MPa, and had the lowest electrical conductivity over the course of a six-week period. During this time, an increase in the T1 signal intensity was observed as the gelatin concentration in the sample increased. On the contrary, the least change in T1 and T2 was noted in the first sample with the 2.5% wt of gelatin. The HCC samples simulated the typical appearance of HCC, with the minimum sample size the body coil could detect being 1cm. Conclusion: Typical Enhancement patterns of HCC were simulated under MRI.

The Effect of Coarse Aggregate Size On Pervious Concrete Mixture

Along with the development progress in Indonesia, it causes the reduction of green areas. Coupled with the lack of public awareness of the environment is a problem that must be considered. Pervious concrete that be as one of the solutions in pavement construction, concrete sheet piles, retaining walls is a product that can be considered successfully in meeting expectations as an environmentally friendly construction. For road pavement, pervious concrete must have a strength of 30 MPa. Therefore, there is a need for research for the mix design of pervious concrete using the ACI 522R-10 Report on Pervious Concrete method with an initial design compressive strength of 25 MPa. The method is to vary the coarse aggregate used in the pervious concrete mixture. In this research, it is divided into 5 variations to find a mixture that is in accordance with the plan or which exceeds the initial plan, and its permeability still meets the requirements for pervious concrete. Testing of the specimens includes the volume weight test, compressive strength, split tensile strength, modulus of elasticity of concrete, porosity, absorption, and permeability. From the research, the results of the volume weight of pervious concrete are 1,974.14 - 2,187.83 kg/m3 that pervious concrete is included in the lightweight concrete group due to it has a weight below 2,200 kg/m3 . The average compressive strength of pervious concrete is 20.089 – 46.978 MPa. The value of the split tensile strength of pervious concrete is 8,968-19,127 MPa. The average value of porosity is between 8,307 – 13,097%. The average value of absorption is between 3.452 – 5.444%. The average value of the permeability is between 0.0025-0.487 cm3/sec. From this research, it can be concluded that the use of different coarse aggregates size will produce pervious concrete with different compressive strengths. The compressive strength with aggregate size 0.5x0.5 without sieving, it closed to the initial plan of 27.72 MPa, whereas the highest compressive strength is for a mixed aggregate size of 1/1 and 0.5/0.5 cm with sieving that the compressive strength achieved 46.978 MPa

The Effect of Coarse Aggregate Size On Pervious Concrete Mixture

Along with the development progress in Indonesia, it causes the reduction of green areas. Coupled with the lack of public awareness of the environment is a problem that must be considered. Pervious concrete that be as one of the solutions in pavement construction, concrete sheet piles, retaining walls is a product that can be considered successfully in meeting expectations as an environmentally friendly construction. For road pavement, pervious concrete must have a strength of 30 MPa. Therefore, there is a need for research for the mix design of pervious concrete using the ACI 522R-10 Report on Pervious Concrete method with an initial design compressive strength of 25 MPa. The method is to vary the coarse aggregate used in the pervious concrete mixture. In this research, it is divided into 5 variations to find a mixture that is in accordance with the plan or which exceeds the initial plan, and its permeability still meets the requirements for pervious concrete. Testing of the specimens includes the volume weight test, compressive strength, split tensile strength, modulus of elasticity of concrete, porosity, absorption, and permeability. From the research, the results of the volume weight of pervious concrete are 1,974.14 - 2,187.83 kg/m3 that pervious concrete is included in the lightweight concrete group due to it has a weight below 2,200 kg/m3 . The average compressive strength of pervious concrete is 20.089 – 46.978 MPa. The value of the split tensile strength of pervious concrete is 8,968-19,127 MPa. The average value of porosity is between 8,307 – 13,097%. The average value of absorption is between 3.452 – 5.444%. The average value of the permeability is between 0.0025-0.487 cm3/sec. From this research, it can be concluded that the use of different coarse aggregates size will produce pervious concrete with different compressive strengths. The compressive strength with aggregate size 0.5x0.5 without sieving, it closed to the initial plan of 27.72 MPa, whereas the highest compressive strength is for a mixed aggregate size of 1/1 and 0.5/0.5 cm with sieving that the compressive strength achieved 46.978 MPa

Radar-stealth and load-bearing corrugated sandwich structures with superior environmental adaptability

The engineering design of lightweight multifunctional composite structures is an attractive research subject with enormous potential in the aerospace and marine fields. Nevertheless, the mechanical and electromagnetic performance of variable-curvature structures has been seldom investigated. Herein, a novel multifunctional sinusoidal corrugated sandwich structure with impedance-type frequency selective surface (FSS) is proposed to provide superior out-of-plane load-bearing capacity and broadband microwave stealth performance. A precise theoretical model is proposed to predict the out-of-plane compressive strength of sinusoidal corrugated structures. The model is based on the Timoshenko beam theory and a modified plastic hinge theory, considering the actual stress distribution on the cross-section. The selective laser sintering (SLS) method is employed to fabricate a series of specimens with different structural parameters. The simulation analysis and experimental results suggest that the proposed mechanical model possesses high precision and wide applicability. The proposed multifunctional sandwich structure has an average ultimate compressive strength of 1.106 MPa and broadband microwave stealth (maximum reflectivity of −8.8 dB in 2–18 GHz). Environmental factors are found to have little effect on microwave reflectivity, including out-of-plane compressing (2 dB), frosting (0.5 dB) and holing (0.5 dB). The present study provides an example of broadband microwave stealth and load-bearing structure with superior environmental adaptability.

Utilization of Plastic Waste Material in Masonry Bricks Production Towards Strength, Durability and Environmental Sustainability

The level of generated plastic waste has awash over a billion metric tonnes of this waste into our environment. If an effective long-lasting solution to this impending disaster is not provided through recycling, reengineering, and conversion of this waste to resourceful materials. Then sustainability and conservation of natural non-replenishable materials will be severely threatened. The aims to avert the impending consequences of this disaster and conserve natural materials have given rise to a sustainable future in the production of low carbon embedded construction materials. Under these circumstances, this study, therefore, presents the strengths and durability of waste plastic bricks (WPB) produced from blending scrap PET plastics and foundry sand. The WPB masonry bricks were produced using ratios of 10:90, 20: 80, and 30: 70 to the combined dry mass of PET and sand. Series of compressive strength tests, modulus of rupture (MOR) tests, apparent porosity tests, water absorption tests, salt-resistance tests, ultrasonic pulse velocity, and scanning electron microscopy (SEM) tests were conducted to investigate the strength and durability of the WPB in conformance with the South African National Standard (SANS 227) for individual load-bearing masonry face brick unit. Compared to the clay bricks with 18 MPa what of strength, the test result revealed that the WPB rendered an average compressive strength of 35.2 MPa. Furthermore, the test result showed that the WPB recorded significant strength resistance under tension compared to the clay brick due to the ductility properties of scrap plastic waste. Also, the acid effects were significantly resisted on the surface WPBs due to the hydrophobic property of the PET- waste. The stiffness of the clay bricks portrayed brittle response, whereas WPBs benefited with high ductility properties, therefore, revealed a great proportionality between the dynamic modulus and ultrasonic pulse velocity (UPV) with a coefficient of determination (R2) of 90%.

Effects of combination mode on mechanical properties of bi-material samples consisting of rock and coal

We performed uniaxial compression tests on coal–rock, rock–coal, and rock–coal–rock bi-material samples. We studied their mechanical behavior using an acoustic emission monitoring and digital speckle strain measurement systems. The average uniaxial compressive strengths of the rock–coal–rock, coal–rock, and rock–coal bi-material samples were 20.54 MPa, 14.28 MPa, and 14.03 MPa, respectively. The strength of the coal determines the overall strength of the bi-material sample. However, the overall strengths of the coal–rock, rock–coal, and rock–coal–rock bi-material samples were greater than that of coal by 11.76%, 10.19%, and 31.84%, respectively. A crack in the coal part of a bi-material sample can develop and spread to the rock part, thus resulting in its splitting failure. The rock–coal–rock bi-material samples exhibited plastic failure, while the coal–rock and rock–coal bi-material samples exhibited brittle failure. Progressive failure of the coal sample induced rebound deformation of the rock sample. The rebound deformation rates of the rock–coal–rock, coal–rock, and rock–coal samples were 0.57%, 0.09%, and 0.12%, respectively. In the pre-peak stage, the average elastic energy of the rock–coal–rock bi-material sample was 92.57%, indicating a strong ability to store external energy. In the post-peak stage, the average post-peak release energy of the rock–coal–rock bi-material sample was the largest, but the average surplus energy was the smallest. Therefore, the rock–coal–rock bi-material exhibited the highest macro-cracking but the dynamic behavior was the least prominent. The coal–rock and rock–coal bi-material samples exhibited less prominent macro-cracking after failure but a more pronounced dynamic behavior.

COMPRESSION STRENGTHS CORRESPONDENCE OF CONCRETES ACCORDING TO THEIR CLASSES AND MARKS

The article presents the problems related to the application of the provisions of the new European standards EN for concrete production, after the withdrawal of the obsolete national standards GOST regarding the correspondence of the classes to the concrete marks. In the context of the application of harmonized standards, there has been a need to establish the correspondence of classes to concrete marks, in order to help design and construction companies to correctly establish the strength mark of concrete to the corresponding class of concrete. The concrete class establishes the normative resistance of concrete for the calculation of constructions, for the service limit state, the prismatic resistance to compression adopted as normative resistance. The ratio between concrete classes and marks, in terms of compressive strength, is determined by the normative coefficient of variation V = 13.5%. The degree of homogeneity of the quality of the concrete is determined according to the values of the standard deviation σ and the average compressive strength of the concrete. As a result of the research, intermediate classes of concrete have been identified, which are not indicated in the normative documents, related to the production of concrete.

Optimizing the L/S Ratio in Geopolymers for the Production of Large-Size Elements with 3D Printing Technology.

Geopolymer concretes can be a viable alternative to conventional Portland cement-based materials. In their design, it is important to maintain an appropriate liquid-to-solid ratio (L/S), which affects several properties, such as the compressive strength, water absorption, and frost resistance. The objective of this paper is to analyze the influence of the fly-ash and metakaolin precursor types for three different L/S ratios: 0.30, 0.35, and 0.45. The results of the physical and mechanical properties, including the apparent density and compressive strength, as well the durability parameters, including frost resistance and water penetration depth, are presented in this paper. It was found that as the L/S ratio decreased, the average compressive strength increased for all materials. After freeze–thaw cycles, decreases in the compressive strength properties were observed for all types of materials—metakaolin- and fly ash-based—irrespective of the L/S ratio. Moreover, the frost resistance of geopolymers increased with the increase in the L/S ratio. The printability of the mixes was also verified in order to confirm the application of the developed materials to additive manufacturing processes.

Geotechnical properties of some tidal flat sediments of Khor-Abdullah coast, southern Iraq

This research involves geotechnical studies for some tidal flat sediments of Khor-Abdulla coast in the southern Basra city. This area has an important strategic location in future, the Iraqi Government intending to establish large engineering projects such as a big Basrah port. Sediment samples have been taken at a depth of 1.25 m to study the physical, chemical, and engineering properties of this region’s sediment. The investigation results reveal that its average high natural moisture was 37.5 %, Liquid Limit LL 45.5 %, Plastic Limit PL 26.5 %, Plasticity Index PI 19%. Hence, these sediments show high clay percentages (85-65%). It can be classified as Silty Clay sediments with low plasticity. Engineering tests resulted in average Compression Strength of 206 kN/m2, Max. dry density 1.63 g/cm3 while consolidation coefficient 0.15 m2/year, consolidation index (0.28) with initial consolidation 35.5 kN/m2, and swelling index 0.071. These factors indicate a week sediment with low plasticity. Chemical tests results reveal high concentrations of sulfates chlorides, and organic matters. TDS were 30666 mg/l, CaCO3 41 mg/l, sulfate 2987 mg/l, Mg 600 mg/l, Ca 46.6 mg/l, and chlorides 1334.2 mg/l. while EC 44.5 mmhos/cm, pH 7.7.&#x0D; &#x0D;

Microstructure properties of poly(phospho-siloxo) geopolymeric network with metakaolin as sole binder reinforced with n-SiO2 and n-Al2O3

This study discusses the influence of the addition of small amounts of nano silica (n-SiO2, NS) and nano alumina (n-Al2O3, NA) to the metakaolin binder hardened by phosphoric acid and cured at an elevated temperature (80 ​°C) for 24 ​h. The condensed phosphor polymeric unit made up of Si–O–Al–O–P is studied by regulating the Si/P ratio at 1.7 in the control sample (MK0) and at 1.42 by using a powdered form of 1% n-SiO2 (MS) and 1% n-Al2O3 (MA). The addition of NS improved the average compressive strength of the specimens (MS) to 58.3 ​MPa, which is 25% higher than the control specimen, and the addition of NA led to a sharp increase of compressive strength by 45% (65.2 ​MPa) for the MA specimens. SEM micrographs revealed a higher compactness of the microstructure. The characteristic changes occurring in the polyphospho-silioxo network were analysed using X-ray diffraction (XRD), Fourier transforms infrared (FT-IR) and magic angle spinning nuclear magnetic resonance (MAS-NMR) (29Si, 27Al, 31P). The formation of P–O–Al during the reaction has been ascertained from the presence of the Q1(2Al), Q2(2Al) and Q1 (0,1Al) environments in the 31P NMR spectrum. The nano additive does not alter the tetra-coordinated alumina, whereas it enhances Hexa coordination of Al as confirmed from the 27Al NMR spectra. The coordination of Si with Al and P is confirmed from the 29Si spectral analysis in all the specimens and the addition of NA to metakaolin binder yields more crystalline phases of AlPO4 embedded in an amorphous matrix with a higher Al/P ratio as evident from EDAX analysis.

RSM-Based Optimized Compressive Strength of Mix Design Concrete Aggregates of Clamshell, Iron Sand, and Epoxy Resin

The need for environmentally friendly concrete that has above average compressive strength continues to be pursued to meet the infrastructure needs of humans. The availability of materials derived from organic waste such as clamshells is thought to be used as an aggregate from concrete which is more environmentally friendly when combined with previously known inorganic materials. The purpose of this study was to optimize the compressive strength of concrete-filled with clamshell powder (CSP), iron sand, and epoxy resin. An optimization approach based on response surface methodology (RSM) was used in this study. Iron sand used is 10% (w/w). The CSP used is in the range of 1 to 4% (w/w). The epoxy resin used is in the range of 10.5 to 14.40% (w/w). The temperature and time of curing were carried out in 301 to 333 K and 4 hours, respectively. The age of concrete is measured in the range of 1 to 28 days. The cylindrical molded concrete has a diameter and height of 100 mm and 200 mm, respectively. All samples were measured for compressive strength using the UTM RTF-1350 (capacity of 250 kN). The concrete composition with epoxy resin (11.93%, w/w) to the standard concrete aggregate mixture produced the highest compressive strength (71.49 MPa). However, the addition of CSP as a filler in concrete has provided a compressive strength (31.18 MPa) above concrete by the Indonesian National Standard (SNI). The combination of CSP and epoxy resin under high-temperature curing conditions is possible to increase the compressive strength of concrete to 45.65 MPa.