Improvement Of Concrete Strength Research Articles

Behavior of monostrand anchors in unbonded post tension flat slab system

Generally, the monostrand anchor, which is made of cast iron and used in the global market, has a rectangular shape. It is commonly used when low concrete stresses are induced and minimum slab thickness is needed. Multiple monostrand anchors can be used adjacent to each other at one or more horizontal levels in slabs to replace a multistrand anchor system, which combines two or more strands in the same anchor. Monostrand anchor has a proper stress distribution, while the multistrand has greater overlap zone stresses in post tension slabs. An experimental study was conducted on round monostrand anchors to investigate anchorage and anchor bearing zones. Concrete blocks were prepared, and tested at different ages. The goal is to evaluate the contribution of the concrete's strength improvement against bursting pressure caused by jacking forces at the edge zone of a flat slab. The blocks were stressed using jacking machine. Strands with two diameter sizes (12.7 mm and 15.7 mm) were used. A rigid steel framework was developed as an abutment that can withstand all jack's response forces on the tested concrete blocks. On the other hand, this framework serves as a fixation for the cables' dead ends. The concrete blocks were attached to this framework. After that, they were stressed up to failure. Hairpin reinforcement were used to strengthen the blocks, and resist the applied stresses. Multiple round monostrands were also placed adjacent to each other to produce stress concentration in the concrete blocks. Numerical models were also constructed using finite element to simulate the experimental tests and validate the obtained results. The results were also compared to ACI provision.

The improvement of concrete strength through the addition of sustainable materials (agro-waste loaded with copper ions)

The country’s rapid industrialization and urbanization stimulated extensive infrastructure development. This technique results in a shortage of construction materials, increased trash generation, and other side effects. The production of long-lasting and environmentally friendly plain concrete slabs is a critical requirement for this task. It is intriguing to observe that the ions of copper in wastewater added to agro-waste (waste tea leaves) can be used to boost the compressive strength and plain concrete slabs’ workability (or walls) as sustainable materials. Waste tea leaves+Cu were incrementally added in 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1.3%, and 1.75% by weight. Casting and testing 36 specimens (12 sets x 3 specimens) for seven- and twenty-eight- days strength. The results indicate that the strength of the sample with 0.7% waste tea+Cu is 55% and 15% more than the reference and that having only tea leaves pieces after seven days, respectively. In contrast, the 0.7% group had 46 percent and 20 percent greater strength after 28 days. These findings propose an innovative approach to dealing with toxic trash and give an accessible, practical, cost-effective, sustainable, and ecologically acceptable way of removing numerous forms of garbage.

Stress Analysis and Structural Optimization of Steel–Concrete Joint of Zhonghua Road Bridge in Liaocheng

Based on Zhonghua Road Bridge in Liaocheng city, a single tower hybrid cable-stayed bridge, the stress of the steelconcrete joint of the girder is studied using the finite element method with the software MIDAS and ANSYS. The beam element model of the whole bridge is established in MIDAS CIVIL, from which the internal forces of the critical sections of the steel–concrete joint under six adverse conditions are obtained. Then, the results are applied in the refined solid-shell finite element model established in ANSYS. With the stress analysis, it is found that when the steel–concrete joint is used in the girder of the single tower cable-stayed bridge, both the compressive strength of concrete and the tensile strength of steel can be fully used, and the structural stiffness can be smoothly transferred through the two different materials in the joint, which makes the structural behavior more reasonable. The detailed stress analysis also shows that it is prone to generate considerable stress concentration at the corners and the connection between the steel lattice chamber and the pressure bearing plate, and the concentration can be avoided by local stiffening and smoothing of the chamfers. The sensitivity analysis of the web thickness in the joints and bearing plates showed that increasing the thickness of the intermediate web would lead to a moderate reduction in the stress of the web itself, while the stress in the steel member remained relatively constant. However, when the thickness of the bearing plate is increased from 60 to 80 mm, the stress of each part of the steel plate in the steel grid will be significantly reduced, and the maximum reduction can reach 48%. The improvement of concrete strength has little effect on the stress of the steel cell, and the C50 concrete strength grade used in the design is more reasonable.

Design and evaluation of an innovative composite silicate-based surface treatment agent of concrete

Silicate-based surface treatment agent is a sustainable material to provide a sealing coat on the surface of Portland cement concrete to improve its hardness, impermeability, chemical durability, and abrasion resistance. A type of composite surface treatment agent of concrete is introduced in the paper, using potassium silicate and lithium silicate as main agents and different contents of lithium sulfate, urea, triethanolamine, organosilicon polyether surfactant, and fluorocarbon surfactant as additives. An orthogonal test was conducted to evaluate the effects of different proportions of the two main agents and five additives. The gelation time and viscosity of the agent and the rebound value and penetration depth of the tested concrete samples were tested to evaluate the performance of the designed composite material. The results showed that the two main agents had significant influences on the viscosity, while potassium silicate had the greatest influence on the rebound value. For penetration depth, urea, triethanolamine, organosilicon polyether nonionic surfactants, and fluorocarbon surfactants all had significant effects. The proper ingredients were selected based on the test results, and the optimum proportion of the designed surface treatment agent was determined based on variance analysis of the test results. Two representative commercial inorganic surface treatment agents were selected to compare with the optimum proportion of the designed material, and the effects of the material on the microstructures of the concrete specimens were analyzed by scanning electron microscope (SEM). The mechanism is that Calcium Silicate Hydrate (CSH) gel and ettringite generated can effectively improve surface properties of concrete. The results showed that the optimum proportion of the designed material can effectively block micropores in the surface layer, thus significantly decreasing the concrete porosity, which is conducive to the rapid improvement of concrete strength and compactness.

Experimental and Numerical Study on Axial Compression Cold-Formed Steel Composite Wall under Concentrated Loads

This paper presents the experimental and numerical studies in the investigation of the concentrated compressive behaviors of cold-formed steel-foam concrete composite wall. The failure modes, load–displacement curves, and load–strain curves of the specimens were obtained from the experiments. The infilled specimen failed due to distortional buckling of the end stud and cracking of the concrete near the corner of the wall. The strength of the high strength cold-formed steel was not being fully utilized. A finite element model was established by ABAQUS software and validated by the test results to investigate the effect of the concrete strength, steel strength, the spacing between stud openings, and the thickness of the concrete protective layer on the behaviors of the composite wall. The results indicate that the improvement of concrete strength has the most obvious effect on the bearing capacity of the composite wall, while the changes in steel strength, concrete cover thickness, and hole spacing have limited effects.

Numerical study of fractal analysis of crack propagation in concrete under different strain rates by meso‑scale particle element modeling

In order to explore the influence of concrete multiple cracks development on dynamic improvement mechanism under higher strain rates, a method to quantitatively describe the relationship between stress and multiple cracks development in the procesds of higher strain rates is proposed. By meso‑scale particle element modeling, SHPB stamping tests of concretes under different strain rates (30s−1≤ε˙≤140s−1) are simulated. The simulation results show that the stress-strain relationship and the law of dynamic strength improvement of concrete are consistent with the experimental results. The crack propagation in concrete under different strain rates is recorded and quantitatively described by the fractal box dimension. The crack propagation in concrete under different higher strain rates is divided into three stages, including micro crack initiation and stability stage, connectivity, extension and widening stage and fragmentation stage. This paper establishes and analyzes the relationships between stress, crack fractal dimension and strain rates under different strain rates. The research shows that at low strain rate the development of multiple cracks and failure of aggregates in concrete have a great impact on the dynamic improvement of concrete. As the strain rate increases, the inertia effect has a greater impact on the dynamic improvement of concrete.

Review of the key parameters of the international calculation guidelines for non-circular RC columns confined with CFRP composites. Comparison with medium and large-scale tests

Several international guides offer recommendations for the calculation and design of reinforcements with fibre reinforced polymer (FRP) composites. To strengthen axially-loaded columns, the guides adopt design stress–strain models based on extensive research into small-scale specimens of plain concrete confined with FRP. However, through this type of testing, it is difficult to accurately predict the behaviour of existing full-scale reinforced concrete (RC) columns confined with FRP composites.This paper presents a review of the formulation proposed by four international guides. The study compiles the available test results on medium and large-scale rectangular RC columns confined with carbon FRP composites subjected to axial compression concentric load.The predictions of the axial strength and the ultimate strain of the FRP-confined concrete are compared to the experimental results. The minimum confinement ratio (CR) recommended in the guides to guarantee sufficient confinement level is also analysed, alongside the estimation of the effective strain in the CFRP jacket at failure. The results obtained have proven uneven.The best predictions of the concrete strength improvement have been obtained with the ACI and fib guides. In general, to comply with the minimum CR proposed by the guides fails to prevent a softening stress–strain response, frequent in the rectangular tests analysed. The more restrictive CR criteria (from the CNR and fib guide) have shown themselves to be more suitable.The ultimate strain of the confined concrete is underestimated by the guides and the errors obtained are much higher than in the prediction of the strength enhancement ratio.Despite the widespread dispersion of the results, the mean value of strain efficiency factor obtained in the tests is similar to the value of 0.55 recommended by ACI. This parameter is not easy to determine for rectangular columns, but its estimation is essential for the calculation.

Sustainable Energy Recovery From the Malaysian Coal Bottom Ash and the Effects of Fineness in Improving Concrete Properties

The particle size (µm) of coal bottom ash displayed significant effects on the concrete engineering properties. This research aims to assess the improvement of engineering properties of concrete containing CBA (fineness: 75 and 100 µm) known as Mix 75 and Mix 100, and to optimize the percentage of coal bottom ash as supplementary cement materials in concrete. The physicochemical properties of coal bottom ash were analyzed using X-ray fluorescence, X-ray diffraction, particle size distribution (PSD), and a scanning electron microscope. The strength of concrete was determined based on workability and compressive and splitting tensile strengths. The concrete strength improvement was optimized by response surface methodology. The results of the study showed that coal bottom ash was rich in silicates based on the highest peak at 45°. The scanning electron microscope images showed that coal bottom ash has few cenospheres and components of irregular-shaped char particles. The splitting tensile strengths in 28 curing days gradually decreased with an increase in coal bottom ash. The optimal percentage of coal bottom ash in Mix 75 is equivalent to 6% within 45.4 curing days producing 40 MPa of compressive strength. Meanwhile, the optimal percentage of CBA in Mix 100 is equivalent to 12% within 56 curing days producing 50 MPa of compressive strength. The future works needed to extend the experimental observations are the economic analysis and effect of the greenhouse reduction on the usage of CBA in building infrastructure.

Analysis of CFRP Confined Concrete Cylinders by using ABAQUS Software

The fiber-reinforced polymer (FRP) wrapping is widely used in concrete column strengthening, as it can enhance concrete strength and ductility. This study aims to develop finite element numerical model that can capture the behavior of the short cylinder column confined with CFRP. After validating the proposed finite element models with previous experimental works, a series of parametric studies have been conducted, including, CFRP number of layers, concrete grade, confinement configuration, and size of samples are investigated in terms of stress-strain curves, ductility, and volumetric strain. The results indicate a significant improvement in concrete strength after fully CFRP wrapping. However, the partial confinement records less improvement in concrete strength but considerable ductility. By increasing the specimen’s size and maintaining the same confinement ratio, the strength enhancement was decreased. Based on this observation; it can be concluded that; by increasing the samples sizes, it should be escorted with more confining ratio than that of the small size. Moreover, it was concluded that as the number of layers increases the ductility increases whether it was full or partial confinement configuration. The CFRP confinement can control the specimen’s dilation during the axial compression test thus presenting less volumetric strain. The proposed formula by (Lam & Teng, 2003) that can predict the stress-strain response of FRP full confined concrete cylinder was compared with the corresponding values. The results indicated that; a good matching was noticed only for the samples located in the same area that was studied by (Lam & Teng, 2003).

Study on the mechanical behavior and micro-mechanism of concrete with coal gangue fine and coarse aggregate

Coal gangue is waste rock generated from coal mining, which results in vast land occupation in mines and severe environmental pollution. Owing to the similarity between coal gangue and natural aggregates, concrete preparation from coal gangue has been considered effective for solving gangue problems. In this study, to further improve the on-site utilisation rate of coal gangue, coal gangue was used to replace fine and coarse aggregates for preparing mortar and concrete. The macro and microscopic characteristics of coal gangue mortar (CGM) and coal gangue concrete (CGC) were investigated while considering the effects of coal gangue fine aggregate (CGFA) replacement ratio, curing time, and water-to-cement ratio. To investigate the macro properties, flexural, compressive, and splitting tensile tests were performed. The results show that CGM and CGC with an appropriate CGFA replacement ratio of 25% exhibited optimal performance. Additionally, by replacing all aggregates with CGFAs and coal gangue coarse aggregates, the 28 d compressive strengths of samples W0.5R100 and W0.4R100 were 44.8 and 52.24 MPa, respectively, which satisfied the C30–C50 concrete strength requirements. Moreover, a model is proposed for predicting the splitting tensile strength of the CGC to address the overestimation of existing national standards. For microscopic analysis, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy were conducted to illustrate the hydrated products and micromorphology of CGC under different conditions, as well as to discuss the effect of the mechanism on strength. Based on the micro analysis, the mechanism of CGFAs is summarised as a coal gangue–Ca(OH)2–H2O reaction system: volcanic-activated SiO2 and Al2O3 in CGFAs react with calcium hydroxide (CH) crystals, and more CH is consumed; subsequently, more calcium silicate hydrate gels and ettringite crystals are produced in the secondary hydration reaction, contributing to a denser microstructure and improvement in concrete strength at the late stage. In particular, gismondine is observed as a new hydration product in the reaction of CGC, which differs from that of normal concrete. This study provides a basis for the large-scale utilisation of coal gangue in situ.

Mechanism analysis of strength evolution of concrete structure in saline soil area based on 15-year service

This paper investigates the strength evolution of pile foundation concrete structures in saline soil areas of inland China after 15 years of service using field exposure field tests. NMR, XRD, SEM, and other test methods investigate the mechanism. According to research findings, the strength of concrete with different mix ratios has increased after 15 years compared to the strength of the pouring period (56 days). The continuous hydration of cementitious materials can continuously refine the pore structure of concrete and reduce the porosity of concrete, which is the main reason for the improvement of concrete strength. In saline soil, pile foundation concrete is susceptible to erosion by SO42– and CO32–. With sufficient space, a large amount of C-(A)-S-H gel generated during concrete hydration, calcite and other products produced during carbonization, and secondary ettringite generated during sulfate attack on concrete can effectively fill the pores in the concrete. These properties confer improved strength to concrete. The reinforcement corrosion tests reveal that most steel bars have not corroded. Only a small portion of the steel bars near the bottom of the pile foundation has eroded due to the thin reinforcement protection layer. After fifteen years, the concrete with a high water-binder ratio (0.59) mixed with corrosion inhibitors deteriorated in pore structure and suffered mild thaumasite sulfate attack. The concrete has low porosity and a high proportion of tiny pores due to its low water-to-binder ratio (0.35) and corrosive inhibitor. These characteristics effectively prevent external corrosive ions from corroding the concrete while protecting the internal steel bars, making them suitable for long-term use in inland saline soil areas of China.

Performance on Jute Fiber Reinforced Concrete with Admixtures and the Replacement of Fine Aggregate by Moorum Soil

As is generally known, the globe is rapidly developing, and building construction plays a crucial role in this development. If we go into further detail, the increased use of concrete results in a depletion of natural resources. We considered substituting the following measurements for part of the concrete's proportions in order to conserve our natural resources. To preserve natural resources like fine aggregate, we are employing metakaolin as an additive in partial substitution of cement at the following percentages: 0%, 5%, 7.5%, 10% and 12.5%. In fine aggregate, we are substituting moorum soil to varying degrees (0, 5, 10, 15 and 20%). To improve the concrete's mechanical and lasting qualities, we use several types of fibres. Concrete is good at compression and weak attention. We are incorporating jute fibres into the volume of concrete with a 25 mm length in various percentages, such as 0%, 0.5%, 1%, 1.5% and 2%, to enhance the tensile qualities of the concrete because we are aware that it is strong in compression but weak in tension. The largest 28-day strength improvement of concrete can be anticipated at partial replacements in the 10-15% range, according to the test results obtained with compressive strength and split tensile strength tests in this instance. The strength parameters are increasing as a result of the combined use of metakaolin.

Utilization of Quarry Dust as a Partial Replacement of Sand in Concrete Making

The use of crushed quarry dust as a partial replacement of river sand in concrete production was investigated in this study. This is expedient as quarry dust can be available at some locations with insufficient river sand for construction purposes. The use of quarry dust is also in concrete is also a measure necessary for improvement of concrete strength. River sand was replaced with quarry dust for different mix designs of concrete for 0% to 25% replacement levels with 5% intervals. The physical properties of river sand and quarry dust were tested and reported and the workability as well as compressive strengths of the concrete mixtures were also tested. It was observed that the slump values increased with increase in percentage replacement of sand with quarry dust. The compressive strength of cubes at 28 day curing for control mixture of 1:3:6 at 0% partial replacement of river sand with quarry dust was 12.6N/mm2 but compressive strengths of 21.5 N/mm2 and 26.0 N/mm2 were gotten for 1:2:4 concrete and 1:1.5:3 concrete respectively. As the quarry dust content increased to 25%, the 28day compressive strength increased to 13.58 N/mm2 and 21.57 N/mm2 for the 1:3:6 and 1:2:4 mixes respectively. Compressive strength values decreased to a value of 25.72N/mm2 for the 1:1.5:3 concrete mix. The maximum compressive strength values were reached at 20% quarry dust content at the age of 28 days for the three concrete grades investigated. The increase in compressive strength with inclusion of quarry dust was attributed to the higher specific gravity of quarry dust above river sand. The compressive strength of quarry dust concrete continued to increase with age for all the percentages of quarry dust contents. Quarry dust was recommended as a suitable partial replacement for river bed sand in concrete production.

Mixture optimization for environmental, economical and mechanical objectives in silica fume concrete: A novel frame-work based on machine learning and a new meta-heuristic algorithm

Partial replacement of cement by silica fume in concrete provides advantages such as mitigation of the impact on the environment of carbon dioxide emitted during cement production, recycling of industrial by-products and improvement of concrete strength and durability. The optimization of the mixture of silica fume concrete (SFC) requires trade-off among multiple objectives (strength, cost and embodied CO2) and consideration of a large number of variables under highly nonlinear constraints. Obtaining the Pareto front of this multi-objective optimization (MOO) problem is computationally expensive. To address this issue, the present study develops a MOO model using machine learning (ML) techniques and a new meta-heuristic algorithm. Firstly, the relationships between components and SFC properties are modelled on a dataset using a back propagation neural network (BPNN) model. Then an individual-intelligence-based multi-objective beetle antennae search algorithm (MOBAS) is developed to search for optimal SFC mixtures that maximize UCS, and minimize cost and embodied CO2 under defined constraints. Results indicate that the proposed MOBAS is more computationally efficient with satisfactory accuracy in comparison with algorithms based on swarm intelligence. The MOO model achieves reliable predictions for UCS with a very high correlation coefficient (0.9663) on the test set. The Pareto front of optimal SFC mixture proportions of the MOO problem is successfully obtained using the proposed model. The proposed frame-work improves the efficiency in SFC mixture optimization and can facilitate appropriate decision making before construction.

Mechanical properties of semi-lightweight concrete containing nano-palm oil clinker powder

The traditional materials used in concrete will run out some day. Therefore, waste materials can be used as an alternative material in concrete production. Palm oil clinker (POC) is one of these wastes. A new method to improve the performance of waste material characteristics is to treat and grind the waste materials to achieve nano-particle size. This study focused on the improvement of concrete strength by using different proportions of nano-palm oil clinker powder (NPOCP) as cement replacement, with a full replacement of POC as the coarse aggregate. Numerous replacement levels for cement have been conducted using NPOCP with 0% as the control mix and 10%, 20%, 30% and 40% of the total binder weight to test slump, density and compressive strength. Results illustrated that the workability of semi-lightweight aggregate concrete (semi-LWAC) increases along with the increase of NPOCP content. Density also decreases along with the increase of NPOCP in the concrete mix. Moreover, the NPOCP with 40% as replacement level has the lowest compressive strength value among all other mixtures, and the 10% replacement level has the highest compressive strength of 39 MPa.

Efficiency of Supplementary Cementitious Materials and Natural Fiber on Mechanical Performance of Concrete

In this research study, mechanical properties of silica fume bagasse ash plain concrete (SFBA-PC) and silica fume bagasse ash basalt fiber-reinforced concrete (SFBA-BFRC) are studied. A total of fifteen concrete mixes are prepared for three separate concrete groups (five for each concrete group). The first group of SFBA-PC contains fixed optimum content of silica fume, i.e., 8%, by cement mass, and variable contents of bagasse ash, i.e., 0%, 5%, 10% and 15%, by cement mass. In the second and third groups of SFBA-BFRC, mixes are prepared like the first group of concrete, but only basalt fibers are added with two different percentages of 0.5% and 1.0%, by concrete volume, respectively. For the evaluation of each concrete mix, different mechanical tests are conducted to determine the stress–strain and load–deflection behavior. In addition to this, split-tensile strength and water absorption tests are also performed for each type of concrete mix. The scanning electron microscopy (SCM) analysis is performed, which has confirmed the pozzolanic activity and filler effect caused by SCMs, which has also improved the bridging effects of basalt fiber that results in concrete strength improvement. The results indicated that the mechanical properties of SFBA-BFRC are generally improved in comparison with those of SFBA-PC. In all three groups of concrete, 10% BA is found to be the optimum content, and SFBA-BFRC containing 8% silica fume, 10% bagasse ash and 1.0% basalt fiber content showed overall better performance under multiple testing scenarios.

Impact of Chemically Treated Waste Rubber Tire Aggregates on Mechanical, Durability and Thermal Properties of Concrete

Studies have shown that the incorporation of waste tire rubber aggregates reduces the strength, increases permeability and decrease thermal conductivity of concrete. However, only a few studies have investigated the effect of surface-modified rubber aggregates on the properties of concrete. This study investigates the effect of the surface treatment of waste tire rubber as coarse aggregates with different oxidizing solutions and different treatment durations on the mechanical, durability and thermal properties of concrete. The properties of concrete incorporated with 8% rubber coarse aggregates (by volume of natural aggregates) which were treated with three different solutions: water (H2O), 20% sodium hydroxide (NaOH) and 5% calcium hypochlorite [Ca(ClO)2] (both as% weight of water) for durations of 2, 24, and 72 h, respectively. The effect of these treatments on the compressive strength, splitting tensile strength, water permeability, thermal conductivity and diffusivity of concrete was investigated. Results show that Ca(ClO)2 has a more positive effect on the strength and permeability compared to NaOH solution and water. Experimental results were statistically analyzed using ANOVA and Post Hoc tests. The analyses showed that the improvement of concrete strength is only significant when the treatment with NaOH and Ca(ClO)2 is prolonged to 72 h. Furthermore, the microstructural analysis of concrete showed that the improvement in the strength is due to the improved bonding between cement paste and rubber aggregates as a result of surface treatment. This microstructural improvement also resulted in lower water permeability of concrete. However, the thermal conductivity and diffusivity increased when the surface treatment duration increases as there are less air voids in the samples. This study shows that, with appropriate pretreatment, a certain percentage of natural aggregates can be safely replaced with waste tire rubber aggregates while maintaining sufficient quality of the resulting concrete.

Stress strain performance of steel spiral confined recycled aggregate concrete

Improvement of concrete strength owing to confinement by lateral reinforcement is disregarded in the current concrete design practice. The focus of this study is to use the pre-existing lateral reinforcement to enhance the behaviour of recycled aggregate concrete (RAC). The stress strain performance of steel spiral confined concrete specimens with different confinement pressure, recycled aggregates (RA) replacement ratio and target strength is studied. The results show a decrease in compressive strength of concrete with the rise in RA replacement ratio. Around 43, 37 and 33% drop in the strength is observed for 100% RA replacement ratio having different target strengths of NAC (i.e., 25, 40 and 60 MPa). However, steel confinement has a positive role to offset the negative effect of RA on strength. The rise in the confinement pressure results in improved ductility and stress strain behaviour of RAC. Due to scant research work related to steel spiral confined RAC, existing models cannot estimate the stress strain performance of steel spiral confined RAC effectively. Therefore, a new model is developed in this study, considering a large experimental program. The newly developed model can be effectively used to predict the stress strain performance of both steel spiral confined normal aggregate concrete and RAC, which provides guidelines for the design of RAC members. Furthermore, a relationship is also developed to determine the allowable content of RA for given confinement without affecting the concrete strength, which may be used to decide the allowable content of RA in designing the RAC compression members.

Effect of high-volume ultrafine palm oil fuel ash on the engineering and transport properties of concrete

Palm oil fuel ash (POFA) is a by-product in palm oil manufacturing and is currently disposed to open areas and landfills without any previous treatment, thereby causing environment pollution. The use of small-particle-sized ground POFA to prepare ultrafine POFA (UPOFA) is a suitable method to improve its characteristics as a supplementary cementitious material. Although high-volume POFA exhibits reduced mechanical properties in the early ages, heat treatment and further grinding reduce its carbon content and increase its pozzolanic activity. In this study, UPOFA was used to minimise the cement content in concrete mix. Cement was replaced with UPOFA at 0 %, 20 %, 40 %, 60 % and 80 % ratios to produce green concrete. Results revealed that the UPOFA showed remarkable improvement in concrete strength, especially with 20 % and 40 % substitution levels. By contrast, the compressive strength reduced at high replacement levels to be 34.5 MPa at 28 days. The water absorption of concrete containing UPOFA is considerably reduced, thus improving the concrete’s durability.

Performance of concrete containing mussel shell (Perna viridis) ash under effect of sodium chloride curing

Mussel shell is a type of waste that consist large amounts of calcium content (CaCO3) (>95%). It is potentially to be used as concrete filler which can reduce porosity in concrete micro-structure (compacted concrete) and indirectly reduce quantity of water used to maintain concrete workability. This paper investigates the performance of mussel shell waste as an admixture in normal concrete. These waste were crushed using ball mill for 5 hour then sieved with 75μm sieve sizes. Five different percentages of mussel shell ash (MSA) were incorporated in concrete as an admixture 0%, 1%, 2%, 3% and 4% (S0, S1, S2, S3 and S4) base on w/c 0.5 according to DoE method with total of 90 samples. Specimens then were cured using 2.37% of sodium chloride (NaCl) solution for 7 and 28 days. Data were analysed according to physical, mechanical and its durability properties of materials and its specimens. Particle size analysis (PSD), specific gravity, SEM image and setting time are measured on MSA, OPC and samples MSA concrete included slump analysis for concrete workability. While it’s mechanical and durability properties of MSA concrete were analyses through compressive, split tensile and water capillary absorption. The result showed that increment percentages of MSA could effect on the strength of both compressive and split tensile. However, minimum percentages of MSA of 1% gained higher strength compared to control specimen. The differences between MSA percentages and its curing duration incorporated indicating an improvement while S1 and S3 indicates lower rate of capillary absorption for 7 and 28 days each. Overall, the results to establish concrete strength improvement of MSA in concrete should be limited to 1% uses. While S2 and S4 for concrete permeability and workability. With this percentages, concrete display an improvement behaviours according to its strength and durability towards sodium chloride exposure.