Study of Effective Barite Concrete Mix Design for Gamma-ray Attenuation

Preliminary study of heavyweight concrete has been conducted, providing basic information of mix design to attenuate γ-ray. This study summarizes some mixtures and compares with mixtures that are widely used in Thailand since the potential of local materials is needed to be more explored. Proportional determinations of heavyweight mixture are majority affected by workability, density, and material cost; the lack of these data is also another reason in performing this study. We limit our study into barite (BaSO4) because they are highly available in Thailand and we expect to use it for a mass production. Modification experiment is expected to achieve effective barite concrete mixture using local material from Thailand and measure relevancy when it applies in Thailand. This experiment evaluated density of concrete, compressive strength, and linear attenuation coefficient of concrete as parameter to determine the effectiveness of the mixture. 7 different barite concrete mixtures with 3 variations of w/c ratios and 3 classifications of coarse aggregate percentages will be examined. Using Cesium-137 and Cobalt-60 energy sources, linear attenuation coefficient (μ) of barite concrete will be measured with different energies which are 0.662 MeV, 1.173 MeV, and 1.332 MeV. W/c ratio has significant impact to workability, associated to strength of concrete and indirectly influences the concrete density. Not only w/c ratios, percentage of coarse aggregate in mixture also impact to linear attenuation coefficient of concrete. We concluded that the effective barite coarse percentage for appropriate workability but still has high density and strength is 0.65 for all water-cement ratios. Consideration addition percentage of coarse aggregate into mixture must be taken wisely due to segregation effect and voids in concrete. Furthermore, barite concrete has high capability to attenuate γ-ray due to high density. These novel insights may be useful for various applications e.g., nuclear power plant and medical units.

Properties of Pervious Concrete Aiming for LEED Green Building Rating System Credits

Pervious concrete is a special type of concrete with high porosity. The use of pervious concrete may achieve many potential LEED green building rating system credits. The objective of this paper is to investigate the appropriate mix proportion which provides the high LEED points and also the good mechanical properties. Nine mix proportions based on possible LEED points were examined. The replacement of cement by fly ash (20% - 60%) and coarse aggregate by recycled aggregate (20% - 100%) were used. Properties of pervious concrete relating to LEED credits and design values such as permeability, void content, compressive strength and splitting tensile strength were evaluated. It was found that the proposed pervious concrete can achieve the stormwater design-quantity control, recycled content and recycled materials credits. According to the results, the mix proportions which cement was replaced by 40% and 60% of fly ash archived the highest LEED credit points and also provided the sufficient mechanical properties. Therefore, these mix proportions are recommended for green construction

Evaluating Damaged Concrete Depth in Reinforced Concrete Structures under Different Fire Exposure Times by Means of NDT and DT Techniques

After a severe fire, concrete structures are generally capable of being repaired rather than demolished. To determine whether the fire-damaged structure can be repaired, an assessment of structural integrity must be conducted. In this research, a laboratory assessment of fire-damaged reinforced concrete (RC) slabs was carried out by using Destructive Testing (DT) and Non-Destructive Testing (NDT) techniques. The study aimed to evaluate the depth of damaged concrete in RC slabs exposed to fire for different periods of time (30, 60, 90 and 120 minutes) based on the correlation between the experimental results of DT and NDT methods. The experiment was conducted with two concrete grades of 24 and 35 MPa. Limestone aggregates were used in this study.After a severe fire, concrete structures are generally capable of being repaired rather than demolished. To determine whether the fire-damaged structure can be repaired, an assessment of structural integrity must be conducted. In this research, a laboratory assessment of fire-damaged reinforced concrete (RC) slabs was carried out by using Destructive Testing (DT) and Non-Destructive Testing (NDT) techniques. The study aimed to evaluate the depth of damaged concrete in RC slabs exposed to fire for different periods of time (30, 60, 90 and 120 minutes) based on the correlation between the experimental results of DT and NDT methods. The experiment was conducted with two concrete grades of 24 and 35 MPa. Limestone aggregates were used in this study. The experimental results indicated that 30 minutes of heating time did not show severe effects on reinforced concrete slabs in comparison with the other cases. A damaged concrete layer of 30 – 45 mm was observed for slabs exposed to fire in 60 and 90 minutes. Besides, 24 MPa slabs also showed a lower damage level compared with 35 MPa slabs

Investigation of Fineness and Calcium-Oxide Content in Fly Ash from ASEAN Region on Properties and Durability of Cement–Fly Ash System

Fly ash is a ubiquitously used pozzolan in cementitious material. Its technical knowledge has been widely studied for several decades and seems very well-established. However, a practical challenge currently exists. Different fly ash, even in different batches produced from similar power plant, has a wide variation of properties. To better control the wide variation of properties, this study aims to assess the effects of cementitious mixtures containing different fly ash properties (degree of fineness and CaO content) on heat release, flow, compressive strength, chloride ion penetration resistance, and carbonation resistance. Results from statistical analysis of 270 tested data of fly ash in various ASEAN countries indicate that the fineness of fly ash particle influences on the compressive strength, chloride ion penetration resistance, and carbonation resistance. Whereas, the CaO content of fly ash only statistically impacts on the compressive strength, but not on the chloride ion penetration resistance and carbonation resistance. To reduce the current practical challenge of the wide variation of cement–fly ash composite properties, their durability properties can be improved by adding smaller fly ash particle in cement system. The control of fly ash production by delivering its optimal degree of fineness is more important than selecting the optimal CaO content of fly ash. The study offers a deep technical value differentiating between effects of its fineness and CaO content such that the fly ash producers and consumers can realize and offer the optimized fly ash for good product quality

Airborne Chloride Intensity and Chloride Ion Penetration into Mortar Specimen in Thailand

The Southern and Eastern parts of Thailand have long coastlines and are located in a hot and humid climate zone. A concrete structure in such environmental conditions tends to deteriorate owing to the corrosion of the steel reinforcement by airborne chloride. The concentration of airborne chloride varies by location and exposure conditions in each country. Thus, when designing concrete structures in such environments, the amount of airborne chloride and the concrete mix proportions should be carefully considered. However, the study of airborne chloride intensity and penetration in Thailand is still limited. This study examined the airborne chloride in the atmosphere in Phuket, Phang-Nga, and Chonburi Province. The amount of airborne chloride was checked every 1–3 months during the test period. Although the distances from the seashore are almost the same in all three locations, the airborne chloride intensity varied owing to the different exposure directions and environmental conditions. Additionally, analysis of mortar specimens with different sources of fly ash installed in Chonburi province to assess the airborne chloride penetration behavior showed that airborne chloride concentration varied with the breaking wave height, rainfall, and varied penetration rate based on the source of fly ash

Exploring ASEAN Fly Ash for Enhancing Cement Hydration and Service Life Prediction of Portland Cement Mortar

The durability of cementitious materials can be improved with the widespread utilization of fly ash (FA). Although FA has been available for use in cement and concrete industries for decades, there is still a practical barrier associated with its application. The difficulty stems from its wide variety and heterogeneity. The purpose of this research is to conduct both experimental and numerical investigations to achieve a better understanding of managing the variation of FA, which reflects its durability. The chemical properties and particle size distribution of FA from five distinct sources in ASEAN region were analyzed. In addition, the degree of reactivity, flow, toughened porosity, and apparent chloride diffusivity coefficients of blended FA-cement systems were studied (Da). The Life365 service life model was executed. Using analysis of variance (ANOVA) and sensitivity analysis using linear regression, the experimental outcomes were statistically examined. Having a 15% FA replacement level resulted in a roughly 70% decrease of the Da value, extending its serviceability by around 13%. The chemo-physical processes in multi-scale structures were shown to be the most important element by statistical analysis, and the degree of response in blended FA-cement systems and its toughened porosity were found to be among the most beneficial aspects affecting its durability

Verifying the Reliability of Impressed Current Method to Simulate Natural Corrosion in Reinforced Concrete

In order to accelerate the corrosion of steel reinforcement in the reinforced concrete structures for laboratory research, the impressed current method has been used widely regardless of the appropriacy of this method on the various aims of the studies relating to the deterioration of the reinforced concrete structures. The aim of this study is to characterize the influence of the impressed current method on the steel-concrete interface in the reinforced concrete to verify the reliability of this method on simulating the natural corrosion. The mill-scale of the steel reinforcement and the steel-concrete interfacial region were investigated using SEM-EDS. The results indicate that impressed current can induce the non-uniform and localized corrosion on the steel reinforcement. The corrosion products formed were likely to the natural corrosion induced by chloride environments. However, the oxidization of OH- at anode can inhibit the precipitation of corrosion products at steel-concrete interfacial region and then slowing down the formation of crack in concrete. This positively leads to an overestimation of load capacity of corroded structure and raises doubt on utilizing this technique to simulate the corrosion behavior

Relation between fibre distribution and post-cracking behaviour in steel fibre reinforced self-compacting concrete panels

In this research, the influence of the fibre distribution and orientation on the post-cracking behaviour of steel fibre 14 reinforced self-compacting concrete (SFRSCC) panels was studied. To perform this evaluation, SFRSCC panels 15 were cast from their centre point. For each SFRSCC panel, cylindrical specimens were extracted and notched either 16 parallel or perpendicular to the concrete flow direction, in order to evaluate the influence of fibre dispersion and 17 orientation on the tensile performance. The post-cracking behaviour was assessed by both splitting tensile tests and 18 uniaxial tensile tests. To assess the fibre density and orientation through the panels, an image analysis technique was 19 employed across cut planes on each tested specimen. It is found that the splitting tensile test overestimates the post20 cracking parameters. Specimens with notched plane parallel to the concrete flow direction show considerable higher 21 post-cracking strength than specimens with notched plane perpendicular to the flow direction.The studies reported in this paper are part of the research project LEGOUSE (QREN, project no 5387). This project is co-supported by FEDER through COMPETE programme ("Programa Operacional Factores de Competitividade"). The materials were supplied by Radmix and Maccaferri (fibres), SECIL (cement), SIKA and BASF (superplasticizers), Omya Comital (limestone filler), and Pegop (Fly ash)

Experimental study of the punching shear behavior of high performance steel fiber reinforced concrete slabs considering casting directions

© 2016 Elsevier Ltd This paper presents the results of an experimental study on the punching shear behavior of high performance steel fiber reinforced concrete (HPFRC) slabs without shear reinforcement, particularly considering the effect of fiber orientation. In recent decades, high performance steel fiber reinforced concrete (HPFRC) has been a new achievement in concrete technology. Due to its superior mechanical properties, civil engineers can address the problem of punching shear of thin slabs that are currently widely used in buildings. By processing some studies, researchers have found that the strength capacity of the material before cracking and the post-cracking resistance strongly depend on the orientation of the fibers, which heavily rely on the casting direction and casting method. While most previous studies focused on the effect on the behavior of beams, this research particularly considers how the casting procedures as well as the volume content of the fiber affect the punching shear behavior of flat slabs

Assessment of Air Pollution from Household Solid Waste Open Burning in Thailand

The purpose of this study was to assess household solid waste management in areas governed by local administrative organizations (LAOs). The obtained results would be used to assess the amount of air pollution emitted from household solid waste open burning. A survey was employed, through the use of questionnaires, to collect data from a random sample of 4300 households residing in areas governed by 96 LAOs. According to the results, it was evident that a total of 26.17 Mt of solid waste were generated per year, of which 6.39 Mt/year was not collected by the LAOs and was eliminated by households. Moreover, the percentage of waste burned on or outside the households’ property was 53.7%, or an equivalent of 3.43 Mt/year of solid waste burned in open areas. In addition, it was found that 0.66 Mt/year of solid waste collected by the LAOs was burned in open areas and was not eliminated properly. Hence, the total amount of solid waste from these two sources was 4.09 Mt/year, which resulted in the emissions of carbon dioxide equivalent, carbon monoxide, sulfur dioxide, nitric oxide, and particulate matter of 1247.3 kt/year, 103.0 kt/year, 1.2 kt/year, 7.4 kt/year, and 19.6 kt/year, respectively