Durability Performance of One-Part Geopolymer Versus Two-Part Geopolymer and Portland Cement Mortar

The investigations in the field of geopolymer binders indicated that this new material has a great potential to be an alternative to cement to reduce the carbon dioxide emissions. On the other hand, it was found that the traditional geopolymer has multiple defects, including the presence of viscous corrosive solutions. Researchers were interested in solving this problem and the traditional type was developed into one-part geopolymer and the need for solutions became in its composition and it became possible for this material to be an alternative to cement. But until now there are unexplained issues about one part geopolymers. In this instance, this study aims towards the investigated the fresh and hardened properties of one-part geopolymer mortar versus two-part geopolymer mortar and PC. The fresh and hardened properties that include workability, compressive strength, sulfate resistance, acid resistance and heat resistance were studied for samples cured at 30 OC and compared to PC samples cured by immersing in water. Moreover scanning electron microscopy (SEM) was investigated to support the test results. The results showed that, workability of one-part geopolymer mortar was enhanced by adding fly ash (FA). Moreover, the results revealed that higher compressive strength was achieved by adding ground granulated blast furnace slag (GGBS) and one-part geopolymer mortar exhibited superior resistance to sulfate, acid and heat by compared to PC. According to a SEM test one-part geopolymer mixes including GGBS were found to be more homogenous and dense than those containing F

Durability Performance of One-Part Geopolymer Versus Two-Part Geopolymer and Portland Cement Mortar

The investigations in the field of geopolymer binders indicated that this new material has a great potential to be an alternative to cement to reduce the carbon dioxide emissions. On the other hand, it was found that the traditional geopolymer has multiple defects, including the presence of viscous corrosive solutions. Researchers were interested in solving this problem and the traditional type was developed into one-part geopolymer and the need for solutions became in its composition and it became possible for this material to be an alternative to cement. But until now there are unexplained issues about one part geopolymers. In this instance, this study aims towards the investigated the fresh and hardened properties of one-part geopolymer mortar versus two-part geopolymer mortar and PC. The fresh and hardened properties that include workability, compressive strength, sulfate resistance, acid resistance and heat resistance were studied for samples cured at 30 OC and compared to PC samples cured by immersing in water. Moreover scanning electron microscopy (SEM) was investigated to support the test results. The results showed that, workability of one-part geopolymer mortar was enhanced by adding fly ash (FA). Moreover, the results revealed that higher compressive strength was achieved by adding ground granulated blast furnace slag (GGBS) and one-part geopolymer mortar exhibited superior resistance to sulfate, acid and heat by compared to PC. According to a SEM test one-part geopolymer mixes including GGBS were found to be more homogenous and dense than those containing F

Performance of geopolymer mortars prepared by different alkaline solutions under elevated temperature

Fire has severe effects on concrete as it causes a significant deterioration in its properties. Geopolymers (GP) are considered as an emerging alternative binder to Portland-cement OPC). This paper presents an investigation of the performance of fly ash (FA) based GP-mortars made with different alkaline solutions after exposure to elevated temperatures (200, 400, 600, and 800 ℃).  The main investigated parameters were the type of hydroxide (NaOH and KOH), type of silicate (Na2SiO3 and K2SiO3), molarity levels of NaOH, Na2SiO3/NaOH ratios, alkaline-solution to FA ratio and sand to FA ratio. Compressive, flexural, and indirect tensile strengths were measured before and after exposure to elevated temperatures. Moreover, SEM analysis was conducted on GP and OPC mortars. The results showed that performance of GP mortars containing Na2SiO3 with KOH was better than GP mixes that contained Na2SiO3 with NaOH or K2SiO3 with KOH after exposure to elevated temperatures. A higher loss rate in mechanical properties after exposure to 800℃ was observed as the NaOH molarity increased. Increasing Na2SiO3/NaOH ratio up to 2.5 caused an increase in the mechanical properties, while increasing that ratio from 2.5 to 3 caused higher loss in the mechanical properties of GP mortars. After exposure to 800 ℃, sand to FA ratio of 2 and alkaline solution to FA ratio of 0.5 gave higher residual strengths than the other ratios. Behavior of GP mortar was found to be better than OPC mortar after exposure to elevated temperatures. SEM images showed that the structure of the GP mortar, after exposure to elevated temperatures, was denser than that of the OPC mortar. Empirical equations capable of predicting the residual mechanical properties of GP-mortars made using different alkaline solutions with good correlation have been proposed

Performance of geopolymer mortars prepared by different alkaline solutions under elevated temperature

Fire has severe effects on concrete as it causes a significant deterioration in its properties. Geopolymers (GP) are considered as an emerging alternative binder to Portland-cement OPC). This paper presents an investigation of the performance of fly ash (FA) based GP-mortars made with different alkaline solutions after exposure to elevated temperatures (200, 400, 600, and 800 ℃).  The main investigated parameters were the type of hydroxide (NaOH and KOH), type of silicate (Na2SiO3 and K2SiO3), molarity levels of NaOH, Na2SiO3/NaOH ratios, alkaline-solution to FA ratio and sand to FA ratio. Compressive, flexural, and indirect tensile strengths were measured before and after exposure to elevated temperatures. Moreover, SEM analysis was conducted on GP and OPC mortars. The results showed that performance of GP mortars containing Na2SiO3 with KOH was better than GP mixes that contained Na2SiO3 with NaOH or K2SiO3 with KOH after exposure to elevated temperatures. A higher loss rate in mechanical properties after exposure to 800℃ was observed as the NaOH molarity increased. Increasing Na2SiO3/NaOH ratio up to 2.5 caused an increase in the mechanical properties, while increasing that ratio from 2.5 to 3 caused higher loss in the mechanical properties of GP mortars. After exposure to 800 ℃, sand to FA ratio of 2 and alkaline solution to FA ratio of 0.5 gave higher residual strengths than the other ratios. Behavior of GP mortar was found to be better than OPC mortar after exposure to elevated temperatures. SEM images showed that the structure of the GP mortar, after exposure to elevated temperatures, was denser than that of the OPC mortar. Empirical equations capable of predicting the residual mechanical properties of GP-mortars made using different alkaline solutions with good correlation have been proposed

Evaluation of consistency properties of freshly mixed concrete by cone penetration test

This study is directed to evaluate the ability of using cone penetration test as a simple method to investigate the consistency level of fresh concrete. A cone of 30° apex angle attached with different load values was used. Eighteen concrete mixes divided into three groups were conducted. Three types of coarse aggregate were tried. Crushed dolomite, round gravel, and crushed basalt all of 20 mm maximum grain size were investigated. For each type of coarse aggregate, six levels of concrete consistency calibrated by standard slump test were tried. For the investigated mixes and at a specified consistency level, the displaced volume values were directly proportional to the applied load. The inclination of this relation is termed as the displaced volume rate (D.V). The results of cone penetration were analyzed and compared to the corresponding slump test values. The displaced volume per unit mass, bearing strength, as well as shear yield strength were the evaluated properties. The results introduce the cone penetration test as a simple instrument that could be adopted either at a laboratory or at site to evaluate fresh concrete workability. Moreover, it is being more sensitive compared to the well known slump test. It can simply and clearly distinguish between stiff mixes as well as floppy ones. Very useful numerical limits for the evaluated properties controlling the workability levels of very low, low, medium, high and very high were proposed

Performance of Portland cement mixes containing silica fume and mixed with lime-water

This study is planned to investigate the properties of Portland cement mixtures containing silica fume and mixed with saturated lime water. The conducted Portland cement mixes included three groups; cement pastes, cement mortars and cement concrete mixes. The main parameters were; type of mixing solution (water or lime-water) as well as the percentage of Portland cement replaced by silica fume. Consistency level, times of initial and final settings, compressive strength development, existence and intensity of CH crystals with age, pozzolanic activity as well as efficiency of the investigated matrices to delay the corrosion of embedded steel bars were the investigated properties. Test results show that using lime-water in mixing enhances consistency degree compared to the corresponding control mixes. Furthermore, it delays both initial and final setting times compared with traditional water due to the common ion effect principles. Moreover, combined use of lime-water and silica fume enhances the pozzolanic reaction that was identified by the strength development at both early and later ages. The existence of CH crystals for higher percentages of silica fume (up to 30%) for further reaction at later ages was observed by XRD results. Moreover, combined use of silica fume and lime-water ensures a high alkaline media around steel bars from the moment of ingredients mixing as long as later ages despite of pozzolanic reaction that was identified from results of chloride attack

Fracture properties of self-compacting fiber-reinforced concrete

Self-compacting concrete (SCC) is an innovative concrete that does not necessitate vibration for placing and compaction. Nineteen concrete mixes were investigated including a control mix without fibers as well as eighteen SCC with fibers (SCFRC) mixes. Three types of fibers (polypropylene, glass and steel) were used. Slump flow, L-box, V-funnel as well as column segregation tests were conducted to assess the fresh properties. Whereas, compressive, splitting tensile and flexural strengths were measured to assess the hardened properties of SCFRC. Three point bending tests were performed for the purpose of assessing the fracture properties of SCFRC. Test results showed that the inclusion of fibers to produce SCFRC mixtures remarkably enhanced the fracture properties including fracture energy (Gf) and fracture toughness (K1c). Inclusion of steel fibers with 2% volume fractions showed an improvement with 26.9 times for Gf over the control mix. Whereas, 104% increase in K1c was recorded for the same mix over the mix without fibers. Adding fibers to SCC to produce self-compacting fiber reinforced concrete (SCFRC) will expand its advantages. However, the application fields still need to understand the properties of SCFRC

Properties of Portland cement concrete cast with magnetized water: a review

The water utilized in concrete manufacture plays an important role within the concrete mix, beginning from controlling the process of hydration of cement, besides appropriate curing to achieve the required strength, not to mention controlling the workability and durability of the concrete structure. The utmost significant challenge for concrete technology is to improve the properties of concrete. Nowadays, the engineering field needs to produce structures in harmony with the concept of sustainable development through the utilization of high-performance materials with an eco-friendly impact that is produced at a low-cost. The magnetic water (MW) provides one of the utmost towards this objective. The cost of magnetizing water is low because of the simple instruments used and the cost can be adapted to the scale of the work. In the last two decades, a new technology, so-called MW technology, has been extended to use in concrete manufacturing. Therefore, currently, the researchers are interested in the use of MW in the manufacture of cementitious materials helping to rationalize the cement usage and reducing reliance on chemical additives that have a negative environmental impact. Consequently, this paper presents the effect of the magnetization process in the structure of water molecules, the main properties of water. Additionally, the effect of using MW on the fresh and mechanical properties, as well as the durability characteristics and performance of cementitious materials have been reviewed. Moreover, the factors that affect the magnetization process of water, which highlighted discuss in this study. The results revealed that using MW significantly enhances the flowability and the characteristic strengths of cementitious materials as well as the durability properties

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially