Papers by Keyword: Self-Consolidating Concrete

Abstract: In structural columns, honeycombs are very common in small and big works. This problem is caused by poor consolidation of the concrete that increases the probability of honeycombs (voids left in concrete). These imply costs incurred and affect the work schedule. An exhaustive search is carried out regarding methods in the scientific literature and materials with respect to their availability in the market related to the problem. In this way, it was found that the design of a self-compacting concrete using the ACI 237R-07 with the use of a supplementary cementitious material aims to be a solution to this problem. Rice husk ashes contain silicon oxide and aluminates. These elements improve or increase the strength of the concrete, offer workability and fluidity properties. It was found that with a 5% replacement, 735 mm and 730 mm of slump flow and J-ring were obtained, respectively. Additionally, the V-funnel time was 9.58 seconds. The use of RHA positively increased the values of the measured tests with respect to the standard, thereby improving the workability and stability properties.

Abstract: Self-levelling and self-consolidating concrete mixtures formed with the use of superplasticizers are worthwhile for the manufacture of reinforced concrete structures. It is important to evenly distribute not only the mixing water in the system, but also the dissociated plasticizer ions for cement dispersed compositions with plasticizing additives. It is established that the optimal sequence of loading and mixing of the components of a cement composition is not only a promising direction for intensifying the manufacture of concrete building structures, but also a tool for improving the mechanical properties of cement brick and concrete made on its basis, as well as for increasing its durability and reliability. When superplasticizers are introduced into the pre-ground cement paste, the rheological properties of the compositions are improved, as well as the structure of the hardened composites. The given article is devoted to the study of the effect of the procedural factor and the duration of mixing of highly concentrated cement compositions with the addition of a superplasticizer based on naphthalene sulfonic acid (SP C-3) on the phase composition of hardened composites during various periods of hydration. Experimental results were obtained using the X-ray phase analysis method. Tested are 15 series of samples of cement stone with W/C ratio range between 0,18 and 0,27 and SP C-3 between 0 and 1.0 % by cement weight. Comparing the phase composition of cement stone after 28 days of hardening with that of 4,5 years, it was found that at first the C₃SH₂ phase, particularly enriched with calcium oxide, is formed, which decays over time and disappears in the 4,5-year hardening amples.

Abstract: Supplementary cementitious materials such as fly ash, silica fume and ground granulated blast furnace slag (GGBS) have been used widely to partially replace cement in producing self-consolidating concrete (SCC). The production of cement is associated with emission of significant amounts of CO₂ and increases the human footprint on the environment. Fly ash, silica fume, and GGBS are recycled industrial by-products that also impart favorable fresh and hardened properties on concrete. This study aims to assess the effect of the amounts of fly ash and silica fume on strength and chloride penetration resistance of concrete. Rapid Chloride Penetration Test (RCPT) was used to assess the ability of SCC to resist ingress of chlorides into concrete. SCC mixes with different dosages of fly ash and silica fume were developed and tested at different curing ages. Test results showed that replacing 20% of cement with fly ash produced the highest compressive strength of 67.96 MPa among all fly ash-cement binary mixes. Results also showed that replacing15% of cement with silica fume produced the highest compressive strength of 95.3 MPa among fly ash-cement binary mixes. Using fly ash and silica fume consistently increased the concrete resistance to chloride penetration at the early ages. Silica fume at all dosages results in low or very low levels of chloride penetration at all curing ages of concrete.

Abstract: Sustainable self-consolidating concrete (SCC) is gaining popularity due to its contribution to reducing the environmental footprint of the construction industry. Sustainability of this type of concrete comes from the significant reduction in usage of ordinary cement and its replacement with reused minerals and industrial by-products such as fly ash, ground granulated blast furnace slag (GGBS), and silica fume. In this study, the correlation between the splitting tensile strength and flexural strength is investigated by studying published data in the literature. Splitting tensile strength is determined through a simple test and flexural strength is obtained from flexural beam test. A correlation between the two measures of tensile capacity is essential to determine the flexural design strength knowing the splitting tensile strength, especially for SCC. A correlation is proposed in this paper to relate flexural and splitting tensile strengths for concrete in which cement was replaced by sustainable minerals and industrial by-products.

Abstract: This paper demonstrates the application of Random Forest (RF) algorithm for prediction of compressive strength of sustainable self-consolidating concrete (SCC) in which significant amount of cement was replaced with minerals such as fly ash, ground granulated blast furnace slag (GGBS), and silica fume. SCC improves the quality of the finished concrete product and is considered an environmentally friendly alternative to conventional concrete. RF proved capable of predicting compressive strength with high accuracy. The ability of RF algorithm to predict compressive strength established confidence on the experimental data itself which can be used for further studies on properties of self-consolidating concrete. The high level of accuracy in predicting essential engineering properties of concrete through RF algorithms offers important opportunities to enhance quality in ready mix production industry.

Abstract: The adverse environmental impact of the construction industry may be mitigated through the partial replacement of cement with supplementary cementitious materials (SCM). SCMs such as ground granulated blast furnace slag (GGBS), impart many favourable fresh and long-term concrete properties. A study by Mohamed [1] assessed the splitting tensile strength of sustainable self- consolidating concrete in which up to 80% of the cement was partially replaced with ground granulated blast furnace slag (GGBS), and developed a prediction formula for the splitting tensile strength. In this paper, the tensile strength prediction formula developed by Mohamed et al. [1] is benchmarked against formulas proposed in different building codes and validated with additional test results obtained from the literature. The proposed prediction formula showed excellent correlation to experimental data obtained from the literature.

Abstract: Fly ash is a sustainable partial replacement of Portland cement that offers significant advantages in terms of fresh and hardened properties of concrete. This paper presents the findings of a study that aims at assessing the durability and strength properties of sustainable self-consolidating concrete (SCC) mixes in which Portland cement was partially replaced with 10%, 20%, 30%, and 40% fly ash. The study confirms that replacing Portland cement with fly ash at all of the percentages studied improves resistance of concrete to chloride penetration. The 40% fly ash mix exhibited the highest resistance to chloride penetration compared to the control mix. Despite the relative drop in compressive strength after 7 days of curing, the 28-day compressive strength of 40% SCC mix reached 55.75 MP, which is very close to the control mix. The study also confirms that adding 1%, 1.5%, and 2% basalt fibers, respectively, to the 40% fly ash mix improves the resistance to chloride penetration compared to the mix without basalt fibers.

Abstract: Self-consolidating-concrete (SCC) has gained wide acceptance in the construction industry given its ability to reduce construction duration and cost. All ready-mix concrete commonly used in hot weather countries, such as United Arab Emirates (UAE), is subjected to continuous agitation during hauling to construction sites. Prolonged mixing, especially at high temperatures can lead to loss of workability and increased difficulties for concrete placement and consolidation. This may result in lower mechanical and durability properties. In this paper, the mechanical and durability properties of self-consolidating concrete (SCC) under hot weather conditions were investigated. Mixing and testing were conducted outdoor at the construction material lab of Abu Dhabi University during last summer of 2014. The test results showed that the mixing time and hot weather adversely affected the fresh properties. The SCC mixtures were continuously mixed for 2 hours under a temperature ranged from 25 to 40 °C, to simulate concrete in a transit truck during transportation to a construction site under hot weather. Polycarboxylate-based high-range water-reducing admixture (PC) and fly ash were incorporated in the investigated SCC mixtures. The results showed that both the compressive strength and durability of SCC were highly affected by fly ash dosage and temperature.Keywords: Hot weather; hauling time, self-consolidating concrete.

Abstract: Every year, millions of cube meters are dredged from dams and restraints as an entertaining and prevention procedure all over the world. These dredged sediments are considered as natural waste leading to an environmental, ecological and even an economical problem in their processing and deposing.Nevertheless, in the context of the sustainable development policy, a way of management is opened aiming to the valorization of sediments as a building material and particularly as a new binder that can be industrially exploited and that improve the physical, chemical and mechanical characteristics of the concrete.This study is a part of the research works realized in the civil engineering department at the university of Mostaganem (Algeria), on the impact of the dredged mud of Fergoug dam on the behaviour of self-consolidating concrete in fresh and hardened state , such as the mechanical performance of SCC and its impact on the differed deformations (shrinkage). The work aims to valorize this mud in SCC and to show eventual interactions between constituents. The results obtained presents a good perspectives in order to perform SCC based in caclined mud.

Abstract: Due to its outstanding performance and merits, Self-Consolidating Concrete (SCC) has attracted a wide attention from scientists, researchers and engineers all over the world. At present, many research activities have been conducted in developing and evaluating SCC and its related technologies. However, existing performance evaluation methods of are mostly limited in the field of material, while structure performance evaluation methods of SCC are rarely reported. As we all known, the lifetime of the SCC structure is mainly subject to its material, structural and durability performances as a whole. Undoubtedly, it is crucial for us to study and develop a sound structural and durability performance evaluation method to complement the existing material performance evaluation methods. As such, the structural and durability performance evaluation method of SCC was studied in this paper.