Papers by Rodrigo Antunes, Ph.D., P.E.
MIX Sustentável
More cement does not necessarily make better concrete or expedite construction schedules. In cont... more More cement does not necessarily make better concrete or expedite construction schedules. In contrast, concrete with lower cementitious content can reach sufficient strength on time to avoid construction delays and last longer. Standard specifications require concrete overdesign (OD) for decades, but studies assessing the actual OD magnitudes are rare. This experimental study aimed to identify the required cementitious materials content (RCC) to meet the OD based on 958 compressive strength tests (σ) representing 8200 m3 of ready-mixed concrete for threshold buildings. The actual OD in commercial concrete appears to be 7 to 21% higher than required. The cementitious materials content should be reduced between 6 and 17% so that concrete can reach the required compressive strength (f’cr) without cement overconsumption. The additional overdesign (AOD) increased significantly as the specified compressive strength (f’c) increased, indicating that concrete producers can be more cautious w...
CivilEng, 2022
This study investigates the high contents of cementitious materials in Portland cement concrete a... more This study investigates the high contents of cementitious materials in Portland cement concrete and assesses the required (f’cr) and actual (σ) compressive strength of concrete specimens. A linear optimization technique identifies the required binder content to reach f’cr. Standard specifications have required concrete overdesign (OD) for decades, but few studies have evaluated the actual magnitude of OD from field data. The compressive strength of 958 cylinders prepared in the field represented 8200 m3 of ready-mixed concrete with 300 and 450 kg/m3 of cementitious are analyzed. The actual OD appears to be 7 to 21% higher than required. The required 28-day compressive strength of concrete was achieved in less than seven days. Therefore, the content of the cementitious materials could be reduced by 6 and 17% so that concrete could reach f’cr without cementitious overconsumption. Reducing cementitious content is recommended to improve construction quality and optimize resource utiliza...
The addition of standard intermediate aggregate (IA) content may provide desired intermediate-siz... more The addition of standard intermediate aggregate (IA) content may provide desired intermediate-sized aggregate particle (ISA) content that can enhance the aggregate gradation and predictability of the aggregate packing (k) and Portland cement concrete consistency. This study evaluates the effect of the ISA on the average variation between traditional dry-rodded and vibrated aggregate packing (Δk) results. Gradation factors were determined and plotted on the Modified Coarseness Factor Chart (MCFC) seeking to identify Δk-ISA content correlations and to investigate a relationship between ISA and concrete consistency. The aftermath of 96 tests were grouped in three intervals determined by gradation curve resemblance. The results indicated that when ISA was between 25 and 27 % (by weight), Δk reached its lowest level: 1.7 %. Also, the optimized gradation (B6) displayed ISA = 26 % and fell right at the center of the MCFC’s Workability Box (WB). Lastly, aggregate blends with 10 < IA <...
Ciencia y tecnología de buques, 2017
This paper completes an exploration analysis of onshore ballast water treatment alternatives at m... more This paper completes an exploration analysis of onshore ballast water treatment alternatives at major ports. e authors had presented results for option (1) ballast water treatment onshore installed in two iron ore ports in 2012 applying the discrete events simulation model. Now, two more options are presented: (2) mobile and (3) desalination reception facilities. e previous simulation model developed called TRANSBALLAST, was adapted to consider these two new alternatives. is model was applied to the same ports presented in 2012 and this evaluation also includes one more port with 50 million tons annually (Mta) of iron ore transport capacity. e results uncovered that for (2) there is an increase of 1.90 days on the average waiting time of ships that moored at Port 1. In (3), the average waiting time and berth occupation rates were observed to remain the same presented in (1). One of the major differences between the systems consists in catching sea water to increase the desalination ...
Ship Science & Technology, 2017
This paper completes an exploratory analysis of onshore ballast water treatment alternatives at m... more This paper completes an exploratory analysis of onshore ballast water treatment alternatives at major ports. The authors had presented results for option (1) ballast water treatment onshore installed in two iron ore ports in 2012, applying the discrete events simulation model. Now, two more options are presented: (2) mobile and (3) desalination reception facilities. The previous simulation model developed, called TRANSBALLAST, was adapted to consider these two new alternatives. This model was applied to the same ports presented in 2012 and this evaluation also includes one more port with 50 million tons annually (Mta) of iron ore transport capacity. The results uncovered that for (2), there is an increase of 1.90 days on the average waiting time of ships that moored at Port 1. In (3), the average waiting time and berth occupation rates were observed to remain the same presented in (1). One of the major differences between the systems consists of catching seawater to increase the desalination plant operational capacity. Among those three onshore ballast water treatment alternatives, (2) does not impact port terminals' infrastructure. Additionally, option (2) could be offered to port users as a ballast water treatment service, and shipowners might not need any onboard ballast water treatment system. (3) Might be feasible to ports regions without enough water supplies solving two issues: transfer of invasive species from ballast water and water recycling.
Mix Sustentavel, 2018
Based on the full-bodied scientific consensus that climate warming is occurring on Earth, signifi... more Based on the full-bodied scientific consensus that climate warming is occurring on Earth, significant environmental and economic benefits may be obtained from cement content reduction in concrete, naming reduction in CO2 emissions, energy consumption, and construction costs. In contrast, standard limestone aggregate may experience an increase in mining rate. The objective of this study was to propose the reduction of cement content in concrete framed by aggregate optimization as a viable alternative to reduce environmental effects from the cement industry. The study concludes that the higher the concrete volume in construction, the more environmental benefit can be obtained by reducing cement content in concrete. A 25 % cement reduction in a concrete pavement led to a decrease of 80.000 tons in CO2 emission, while a seaport construction displayed a decrease of 17.000 tons of CO2. The higher the designed cement per volume of concrete, the more budget savings in case of reduction in cement content. Port construction presented a reduction of 20.10 USD per m3 of concrete in cement costs against 11.04 USD per m3 in pavements. An 11.5 % increase in aggregate mining is expected when concrete contains less cement in its composition, targeting South Florida (U.S.A.) quarries.
Int. Journal of Engineering Research and Application, 2018
The addition of standard intermediate aggregate (IA) content may provide desired intermediate-siz... more The addition of standard intermediate aggregate (IA) content may provide desired intermediate-sized aggregate particle (ISA) content that can enhance the aggregate gradation and predictability of the aggregate packing (k) and Portland cement concrete consistency. This study evaluates the effect of the ISA on the average variation between traditional dry-rodded and vibrated aggregate packing (Δk) results. Gradation factors were determined and plotted on the Modified Coarseness Factor Chart (MCFC) seeking to identify Δk-ISA content correlations and to investigate a relationship between ISA and concrete consistency. The aftermath of 96 tests were grouped in three intervals determined by gradation curve resemblance. The results indicated that when ISA was between 25 and 27 % (by weight), Δk reached its lowest level: 1.7 %. Also, the optimized gradation (B6) displayed ISA = 26 % and fell right at the center of the MCFC's Workability Box (WB). Lastly, aggregate blends with 10 < IA < 11 % (by weight) translated into 25 < ISA < 27 % and surrounded the WB of the MCFC. The study concludes that adding IA to concrete can increase adherence between concrete design and placement, besides providing better consistency to concrete.
ASTM Advances in Civil Engineering Materials , 2018
Designing concrete based on aggregate packing and optimized gradations can result in 25 % less ce... more Designing concrete based on aggregate packing and optimized gradations can result in 25 % less cement content to reach a targeted compressive strength and less water-reducing admixture to obtain a required consistency. In this research, two studies were conducted: (1) an experimental analysis to determine the effects of aggregate packing on concrete strength and consistency; and (2) an investigation of the relationship between the traditional dry-rodded and the vibrated aggregate packing. Excellent correlation was found between 240 packing results, which can be applied to the modified mixture design method presented. Also, 40 slump and 120 compressive strength standard tests were performed to evaluate the effects of reducing cement content by 7.5, 15, 20, and 25 % to slump and compressive strength of concrete mixtures. The compressive strength of the optimized mixture demonstrated less susceptibility to variations due to cement content reductions when compared to nonoptimized mixtures. The Modified Coarse Factor Chart can be used to design an optimized concrete mixture efficiently in conjunction with aggregate gradation and packing, cement content, and concrete consistency.
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Papers by Rodrigo Antunes, Ph.D., P.E.