Effect of aggressive chemicals on durability and microstructure properties of concrete containing crushed new concrete aggregate and non-traditional supplementary cementitious …

The increasing awareness and usage of traditional supplementary cementitious materials (SCMs) in concrete have pressured the construction industry to look for alternatives to overcome the concerns over their plentiful availability in the future. This research illustrates the performance of recycled aggregate concrete prepared with the incorporation of available industrial by-products, namely rice husk ash (RHA), palm oil fuel ash (POFA) and palm oil clinker powder (POCP) as alternatives for traditional SCMs. The effect of hydrochloric (HCl) acid and magnesium sulfate (MgSO 4) attack was evaluated by measuring the change in mass, compressive strength and microstructural analysis. The results revealed that the incorporation of RHA, POFA and POCP up to 30% minimizes concrete deterioration and loss in compressive strength when the specimens were exposed to HCl solution. In addition, the scanning electron

Development of Self-Consolidating High Strength Concrete Incorporating Treated Palm Oil Fuel Ash

Palm oil fuel ash (POFA) has previously been used as a partial cement replacement in concrete. However, limited research has been undertaken to utilize POFA in high volume in concrete. This paper presents a study on the treatment and utilization of POFA in high volume of up to 50% by weight of cement in self-consolidating high strength concrete (SCHSC). POFA was treated via heat treatment to reduce the content of unburned carbon. Ordinary Portland cement was substituted with 0%, 10%, 20%, 30%, and 50% treated POFA in SCHSC. Tests have been conducted on the fresh properties, such as filling ability, passing ability and segregation resistance, as well as compressive strength, drying shrinkage and acid attack resistance to check the effect of high volume treated POFA on SCHSC. The results revealed that compared to the control concrete mix, the fresh properties, compressive strength, drying shrinkage, and resistance against acid attack have been significantly improved. Conclusively, treated POFA can be used in high volume as a cement replacement to produce SCHSC with an improvement in its properties

Durability characteristics of self-consolidating high strength concrete containing ground palm oil fuel ash as a partial cement replacement / Belal Gamal Muthanna Alsubari

Palm oil fuel ash (POFA) is considered as a waste material, and it is dumped into landfills without any commercial return or cycling which considered as a costly practice. Previous studies have shown that POFA is a pozzolanic material and can be used as a partial cement replacement in concrete. However, there is a little information regarding the use of POFA as a cement replacement for producing self-consolidating high-strength concrete (SCHSC) as well as there is not any report in the case of durability properties of this type of concrete. In this study POFA has been used as a partial cement replacement to produce SCHSC. Samples were made by replacing Type I Portland cement with various proportions (0%, 10%, 15%, and 20%) of POFA. Fresh properties such as filling ability, passing ability, and segregation resistance were examined to fulfil the requirements of self-compacting concrete according to EFNARC standard. The hardened properties and durability characteristics, such as compressive strength, drying shrinkage strain, rapid chloride permeability, initial surface absorption, acid attack, sulphate attack, and water absorption tests have been studied. Test results showed that SCHSC integrated with POFA can be produced with no adverse effects on the fresh properties. Incorporating ground POFA caused a reduction in the drying shrinkage strain of all the mixes containing POFA compared to concrete made with OPC. SCHSC containing ground POFA showed a significant reduction in the initial surface absorption, and 20% cement replacement level with the POFA exhibited the lowest initial surface absorption compared to all mixes. Integration of ground POFA as a partial cement replacement increases the resistance of SCHSC towards rapid chloride permeability, acid attack, and sulphate attack. 20% cement replacement showed the highest resistant toward chemicals attack. Conclusively, incorporating POFA as a partial cement replacement in SCHSC does not cause adverse effects on the fresh properties and significantly improved durability characteristics of SCHSC concrete

Development of Self-Consolidating High Strength Concrete Incorporating Treated Palm Oil Fuel Ash

Palm oil fuel ash (POFA) has previously been used as a partial cement replacement in concrete. However, limited research has been undertaken to utilize POFA in high volume in concrete. This paper presents a study on the treatment and utilization of POFA in high volume of up to 50% by weight of cement in self-consolidating high strength concrete (SCHSC). POFA was treated via heat treatment to reduce the content of unburned carbon. Ordinary Portland cement was substituted with 0%, 10%, 20%, 30%, and 50% treated POFA in SCHSC. Tests have been conducted on the fresh properties, such as filling ability, passing ability and segregation resistance, as well as compressive strength, drying shrinkage and acid attack resistance to check the effect of high volume treated POFA on SCHSC. The results revealed that compared to the control concrete mix, the fresh properties, compressive strength, drying shrinkage, and resistance against acid attack have been significantly improved. Conclusively, treated POFA can be used in high volume as a cement replacement to produce SCHSC with an improvement in its properties

Heat-treated palm oil fuel ash as an effective supplementary cementitious material originating from agriculture waste

Palm oil fuel ash (POFA) is generated from the combustion of oil palm waste. This ash is considered a disturbance to the environment since it is dumped without being profit return or recycled, thus causing environmental problems and human health hazards. However, it has been proven that POFA is a pozzolanic material that can be utilized as cement replacement in concrete. If POFA is heated at high temperature, it exhibits better pozzolanic performance. In this study, the treatment processes as well as microstructure and pozzolanic characteristics of POFA are considered. Ordinary Portland cement was replaced with 0, 30, 50, and 70% treated POFA (T-POFA) in a paste. The hydration products of different hardened pastes were checked by means of simultaneous thermal analysis (STA), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM) in order to assess the effect of TPOFA on the paste microstructure. According to the test results, the physical properties and chemical composition of T-POFA greatly enhanced due to heat treatment and the milling process. It was observed that the calcium hydroxide content decreased in pastes containing T-POFA upon hardening, which is evidence of its consumption by the pozzolanic reaction. The FESEM images displayed needle-like and reticular C–S–H phases in the control paste, while floc-like and fibrous-like C–S–H phases well-connected to each other were observed in the pastes containing T-POFA

Punching Strength of Reactive Powder Reinforced Concrete Flat Slabs

This research is devoted to investigating experimentally the punching shear strength of reactive powder concrete slabs under monotonic loading. All slabs have the same flexural reinforcement and same dimensions (1000mm length,600mm width,50mm thickness). The experimental program includes casting and testing of sixteen slabs tested under monotonic loading. The major parameters adopted in the current research include the shape of column (circle, square), column size (twocolumn sizes), number of columns (one, two), and the distance between two columns (3d,5d,7d). Results showed that, the slabs with circular column sections have slightly higher ultimate load than those with square column sections. An increasing column area increases the load of punching shear failure. It was found that the ultimate failure load for slabs with two columns is greater than the slabs with one column. Related to the effect of distance between the two columns for monotonic, it was found that the slabs maximum load reaches the maximum value at distance between the two columns equal to(7d) for a circular section with a diameter of 85mm and 113mm and square section with dimensions of (100*100)mm. While the maximum failure load reaches the maximum value when the distance between two columns (d) for a square section with the dimension of (75*75)mm. Related to the crack patterns, it was noticed that for slabs with larger columns sections with the distance between columns equal to 7d, the failure zone extended (in a large direction) to the slab sides

Effect of Magnesium Sulphate on Self-Compacting Concrete Containing Supplementary Cementitious Materials

The length change is negligible and can be attributed to the normal distension of concrete. On the other hand, concrete suffering from mass loss gives a good indicator about the durability of SCC. Permeability of concrete is an important factor in classifying its durability generally; concrete with low Permeability will afford better protection of the reinforcement within it than concrete with high Permeability. In this paper, the assessment of magnesium sulphate (MS) attack on concrete containing various ratios of the supplementary cementitious materials (SCM) was investigated for concrete containing FA, RHA, and GGBS with cement replacement levels of 15%, 10%, and 5%, respectively, based on the selected samples from the concrete to the statement of the effect of magnesium on some of the characteristics of concrete such as compressive strength, height, and weight compared with similar samples but under laboratory conditions dry and moist water treatment. Test results showed that the SCC content SCM appear to have higher strength values than those stored in water and air sample; the highest value of mass loss is recorded for the control mixture compared with concrete content SCM, and the change in length in curing concrete is much less relative to the change for concrete immersed in MS

Sustainable palm oil fuel ash mortar used as partial adhesive replacement in flexurally strengthened RC beams

Structural strengthening comprises modification of the structural elements to enhance their load bearing capability, stiffness, toughness, and ductility. The present study is an experimental investigation on the performance of reinforced concrete (RC) beam specimens strengthened by the side near surface mounted (SNSM) technique with reinforcement strengthening of glass fiber reinforced polymer (GFRP) bars in flexure. Sustainable palm oil fuel ash (POFA) mortar (PM) and normal mortar were used as bonding mediators between the concrete substrate and GFRP bars as a replacement for epoxy adhesive. A total of eight specimens, in which one was a control, one was strengthened by GFRP bars and full epoxy adhesive in grooves, and six specimens were strengthened by GFRP bars and partial replacement of epoxy adhesive by PM and NM, respectively. The specimens were tested in the static condition under four-point bending. During the test, the loads, deflection, and strains of the specimens were stored in a data logger and the failure modes of the specimens were observed. Critical discussions were made based on the flexural capacities, load-deflection, ductility, energy absorption, the influence of epoxy replacement and the type of mortars in the strengthened specimens as compared to the control specimen. ACI 440.2R-08 and ACI 318-11 were applied to predict the ultimate load-carrying capacity and deflection characteristic graphs of the tested specimens. The predicted results of the specimens were in close agreement with the experimental results. The test results also exhibited that the epoxy substituted by sustainable PM had superior flexural performance to the NM strengthened SNSM-GFRP bar specimens, particularly when considering the economic and eco-friendly viewpoint.</p

Effect of bonding materials on the flexural improvement in RC beams strengthened with SNSM technique using GFRP bars

In this paper, the effectiveness of cement mortar as bonding materials in the strengthening of reinforcements and concrete surface for flexural improvement of reinforced concrete (RC) beams were investigated. Recently, side near surface mounted (SNSM) and existing near surface mounted (NSM) techniques with glass fiber reinforced polymer (GFRP) bars are adopted as the strengthening methods for RC beams in which varieties of epoxy adhesive were replaced with cement mortar. In this study, one control and seven strengthened beams were tested under four-point loading in a static condition. The load-carrying capacities, failure modes, deflection, strains characteristic, parametric study and energy absorption capacities are addressed through laboratory experiments. The results revealed that the flexural performance was successfully achieved by using cement mortar as a replacement for adhesive. The SNSM strengthening technique exhibited better structural performance compared with the existing NSM technique in all aspects

Torsional Behavior of RC Beams with Transverse Openings Strengthened by Near Surface Mounted-Steel Wire Rope Subjected to Repeated Loading

The presence of the openings negatively effects on the strength of the beams where they act as a weak point because of the sudden change in the cross-section of the beam, so it becomes necessary to make strengthening for the beams to resist the effect of the openings and improve the strength of the beams, especially if the beams are subjected to repeated loads because of its effect on the strength at the failure. This paper studies the effect of the openings on the beams subjected to repeated loading and determine the extent of the increase in the strength of the beams when strengthened by the NSM technique. The experimental program included casting and testing fifteen RC beams, six of them considered as a control beams (three with strengthening and three without strengthening), and nine of them having circular transverse openings in different locations and strengthened by the NSM technique. Every type of beams is tested under three different types of loads (monotonic, constant repeated load, and incremental repeated load). All of the beams have the same dimensions and same reinforcement. The results show that all the beams with transverse openings are affected by repeated loads where the ultimate torque decreases and the twist angle increases. The existence of openings has a noted effect on reducing the ultimate torque, whereas the percentage of decrease in the ultimate torsional capacity reached 43.83% at the beam where the opening location is closest to the support (at the quarter of the clear span) and subjected to constant repeated loads, and the ultimate torque is significantly improved when the opening position is moved away from the supports. Also, the existence of strengthening reduced or eliminated the influence of openings on the ultimate torque compared with related non- strengthened beams