Concrete Age Research Articles

The effect of ferrophosphorus aggregate on physical and mechanical properties of heavy-weight concrete

The compressive strength of heavy-weight concrete specimens made with different percentages of ferrophosphorus and normal aggregates, steel powder, and Nano silica powder was examined. A series of 60 concrete specimens (dimensions of 150 × 150 × 150 mm) with different percentages of the mentioned materials were made and their compressive strength was measured at the concrete age of 28 days at the same loading velocities. After determining the compressive strength, the linear attenuation coefficient of the specimens was determined by radiation with gamma ray from a caesium-137 source. The results showed the most effective factors in increasing the compressive strength respectively were ferrophosphorus aggregates, Nano silica powder, and steel powder. The most effective factors in increasing the linear attenuation coefficient were ferrophosphorus aggregate, steel powder, and Nano silica powder, respectively. The highest compressive strength was obtained at the concrete age of 28 days by the specimen made with 100% ferrophosphorus, 20% steel powder, and 5% Nano silica and equaled 52(MPa). The lowest compressive strength was 25(MPa) obtained with 25% ferrophosphorus, 10% steel powder, and without Nano silica. Moreover, based on the results of the specimens’ linear attenuation coefficient test, the highest linear attenuation coefficient belonged to the specimens made with 100% ferrophosphorus, 30% steel powder, and 5% Nano silica and equaled 0.295, while the lowest linear attenuation coefficient was 0.1514 cm−1 obtained by the specimen made without ferrophosphorus and steel powder with 8% Nano silica.

Prediction of Compressive Strength of General-Use Concrete Mixes with Recycled Concrete Aggregate

This paper presents the mechanical behaviour of concrete mixes made with recycled aggregate by replacing the natural aggregate with crushed concrete from pavement demolition. The purpose of this study was to determine the feasibility of using recycled aggregate from pavement demolition to make new concrete for pavement applications. Considering a control mix without recycled aggregate (RCA0) designed for a compressive strength of 34 MPa, two types of concrete mixes with 50% (RCA50) and 100% (RCA100) replacement percentage of natural coarse aggregate by recycled aggregate were made. The resulting concrete specimens were tested at three different curing ages, 7, 14, and 28 days. The results of this study showed that the compressive and flexural strengths decreased for all two mixes as the recycled aggregate content increased, while the density was slightly affected. A new model based on multiple linear regression analysis of the data from this study and other 14 studies from the literature was developed. The model can be used to predict the compressive strength of general-use concrete mixes with recycled aggregate (20–40 MPa) considering both the recycled aggregate content and the curing age of concrete. A good correlation was found between the compressive strength and the two parameters investigated. Given the predictions of this model, it is recommended not to use more than 30% recycled concrete aggregate in the production of new concrete in order not to affect its strength.

Influence of water content investigation on GPR wave attenuation for early age concrete in natural air-drying condition

In this study, an efficient application to evaluate water content of concrete in a non-destructive way in natural air-drying conditions by time-lapse Ground-penetrating radar (GPR) measurements is described. This was achieved by carrying out time-lapse GPR measurements on a concrete block with 2 GHz shielded antenna in 24 measurement days between day three and the 150th day of concrete casting. The characteristics of the electromagnetic (EM) wave are directly influenced by the presence of water content in a material. Change in water content results in variations in dielectric properties, including dielectric permittivity and conductivity. The study focused on variation of EM wave attenuation, which is related to direct and reflected wave amplitudes due to decrease of water content in the sample. In order to obtain a reflected wave a reinforced bar was embedded at 10 cm depth. The ratio of the direct wave and reflected wave on each measurement day decreased with respect to the reflection amplitude, due to concrete desiccation. These results are a guide to determining the relationship between volumetric water content (VWC) and EM wave attenuation. The method has significant potential on freshly produced young concrete samples to monitor their quality. The suggested method may also have potential for practical on-site studies to determine possible corrosion risk due to water intrusion.

Review: Age of Concrete: Housing and the Shape of Aspiration in the Capital of Mozambique

Book Review| June 01 2021 Review: Age of Concrete: Housing and the Shape of Aspiration in the Capital of Mozambique David Morton Age of Concrete: Housing and the Shape of Aspiration in the Capital of Mozambique Athens: Ohio University Press, 2019, 310 pp., 72 b/w illus. $90 (cloth), ISBN 9780821423677 Ana Tostões Ana Tostões Tecnico, University of Lisbon Search for other works by this author on: This Site PubMed Google Scholar Journal of the Society of Architectural Historians (2021) 80 (2): 235–237. https://doi.org/10.1525/jsah.2021.80.2.235 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Ana Tostões; Review: Age of Concrete: Housing and the Shape of Aspiration in the Capital of Mozambique. Journal of the Society of Architectural Historians 1 June 2021; 80 (2): 235–237. doi: https://doi.org/10.1525/jsah.2021.80.2.235 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentJournal of the Society of Architectural Historians Search David Morton's Age of Concrete is an amazing book recounting the story of the city of Maputo, Mozambique's capital, focusing on the development of its subúrbios—the spaces in which the city's inhabitants challenged colonial-era building rules and confronted the postcolonial circumstances surrounding the construction of an independent Mozambique. Morton's refreshing narrative reveals an inspired storyteller who delves deeply into facts regarding the people whose daily lives and environments shaped the country's history. Under colonialism, many African cities were divided into central urban cores and large, informal peripheries deprived of basic urban infrastructure. While city centers were often designed with Western settlers in mind, the peripheries became large slums for the native working classes. This stark spatial division has left permanent marks on contemporary African metropolises across the continent. Morton's work builds on this history in tracing Maputo's development from the 1940s under Portuguese colonial domination, through moments of revolution... You do not currently have access to this content.

Performance-Based Approach for Deciding the Age of New Concrete for Thin Epoxy Overlay Application

A thin epoxy overlay application is a capital preventive maintenance activity. Epoxy overlays reduce the rate of chloride ion ingress and extend bridge deck service life. Highway agency policies and manufacturer specifications require maintaining a 28-day curing period (7-day wet and 21-day dry curing) before the application of an epoxy overlay on bridge decks requiring new concrete for patches and repairs. Consequently, the contractors wait for 28 days to apply an epoxy overlay. Delaying application time increases project completion time and the cost of construction and mobility. The suitability of new concrete to receive epoxy overlays and the performance of overlays depend on several parameters including concrete strength, moisture, and tendency to crack. Such parameters depend on concrete mixture ingredients and wet and dry curing periods. This paper presents a performance-based procedure for evaluating the possibility of reducing the 28-day waiting period for a thin epoxy overlay application on new concrete. An experimental program was developed and executed to evaluate the impact of epoxy overlay application parameters and overlay performance using a tensile bond pull-off strength test. The results support developing a performance-based procedure for deciding on the suitable age of new concrete to receive a thin epoxy overlay. The pull-off bond strength of epoxy overlays applied at 7, 14, and 21 days, following a 7-day moist curing, shows the possibility of applying an epoxy overlay before the end of the 28-day curing period stipulated in the current specifications.

Condition Assessment of Induced Draught Cooling Towers Located In Different Climatic Regions of India

Induced Draft Cooling Towers (IDCT) are an important industrial structures, which removes the heat absorbed in the circulating cooling water systems of thermal power plants. The cooling tower in general comprises of RCC members’ viz. Column, Beam, Slab, Wall, Louvers, Fanstack Shell etc. The process of operation is itself an important factor which affects the durability of members of IDCTs, due to which the RCC members of IDCT are subjected to varying exposure condition, some members are continuous under water, some are partially submerged, some have alternate drying & wetting and some are completely dry. Due to different exposure conditions of RCC members of these structures generally shows very contrasting states of distress i.e. varying from apparently un-distressed to highly distressed state. Apart from process of operation of IDCTs, the other important factors that affect the durability of these RCC structures are presence of Chloride in water being cooled & Chloride in concrete present during the construction and carbonation due to aging of concrete. The RCC structures were assessed by various Non-Destructive evaluation techniques and deterioration mechanisms were established. The present paper highlights the findings of condition assessment studies of selected IDCTs located in different climatic regions of India.

Relationships among the Characteristic Tensile Strain, Curing Age, and Strength of Reactive Powder Concrete.

The characteristic tensile strain of reactive powder concrete is a critical indicator of its resistance to cracking. In order to study its crack resistance performance, in this study, we investigated changes over time in the characteristic tensile strain patterns of reactive powder concrete. An axial tensile test was performed to obtain the stress–strain curves of reactive powder concrete after curing ages from 3 to 56 days, and then we identified changes over time in the initial and ultimate tensile strain patterns. An analysis was conducted to determine the correlation between the initial tensile strain and the ratio of tensile strength to elastic modulus. The correlations between the ultimate tensile strain and its curing age as well as that of the ultimate tensile strain with its tensile strength and its compressive strength were established, and an approach was proposed for calculating the characteristic age of reactive powder concrete.

4-Channel Concrete Temperature Data Acquisition System Using GPRS data Network

Objectives: To design a non-destructive, low-effort, low-cost device that can estimate the early age and compressive strength of in-place concrete in real time. The maturity protocol eliminates the need for on-site concrete cylinder break checks or hammer tapping test saving time and resources. Methods: Four different temperature sensors were used to measure the temperature of concrete in order to improve the system’s accuracy. As concrete structure monitoring with temperature sensors is a continuous process, the study includes automated data logging at regular intervals, storage of measured temperature data over time on an attached SD card, and transmission to a server through the SIM800L’s GPRS capability. Findings: The current work presents a low-cost (31 USD), low-powered (3.7v/2.8A), and portable temperature sensor and logger that will track and record temperature values so that values can be monitored remotely from anywhere on the planet. Data can be managed and tracked from any location and on any computer that has internet access. Communication between presented units with MQTT platform has been studied. Novelty/Applications: This device is a simple batteryoperated, small-size, compact, low-power data acquisition system with multiple sensors. With the support of GPRS, data can be sent to a server. Concrete testing delays are no longer a concern. It is possible to check the status of pour and receive updates anytime, wherever, on any computer with this method’s real-time data and 24/7 remote monitoring capabilities. This simple,trouble-free module is completely integrated and needs no wires or testing laboratories, allowing for quick onsite decisions and preventing unnecessary setbacks. Keywords: GPRS; DS18B20; ESP8266; MQTT (Message Queuing Telemetry Transport)

A study of compressive strength of concrete by using sugarcane baggase ash

Ordinary Portland cement (OPC) is widely as a construction material in the entire world. Since silica and lime being the basic components of the ordinary Portland cement therefore many industrial waste materials comprising of these elements are used as supplementary product in OPC. Sugarcane Bagasse ash is one such material which has high silica (SiO2) content that results in formation of C-S-H bond when operated with free lime. The basic idea behind the utilization of industrial waste is to reduce its abundance in nature and also to minimize the cost of concrete. The present study focusses on making a sustainable concrete and assessing its performance by using sugarcane baggase ash (SCBA) as replacement of cement with different percentages (0%,5%, 10%, 15%, and 20%). For the same M25 & M30 grade of concrete with water cement ratio of 0.45 was prepared by using this composition cube casted for testing purpose. The curing of these specimen was done in different environments and the strength was analyzed at various concrete ages i.e. 7, 28, 56, and 90 days. The study provided the evidence that utilization of SCBA as replacement with cement is highly advantageous up to an optimal limit without causing any reduction in strength. In addition, it revealed that SCBA concrete performs better when subjected to aggressive environment as compared to OPC even at later stage.

Experimental Research on Interfacial Bonding Strength between Vertical Cast-In-Situ Joint and Precast Concrete Walls

In the monolithic precast concrete shear-wall structure, the bonding property of cast-in-situ joints to precast concrete walls is important to ensure the entire structural performance. Aiming to the vertical joint of precast concrete walls, an experimental study was carried out considering the factors including the strength of precast and joint concretes, as well as the interface processing and casting age of precast concrete. The micro-expansion self-compacting concrete was used for the cast-in-situ joints. The interfacial bonding strength between joint and precast concrete was measured by splitting tensile test. Results show that the interfacial bonding strength was benefited from the increasing strength of joint concrete and the spraying binder paste on the interface of precast concrete, and unbenefited from the overtime storage of precast concrete. The washed rough surface with exposed aggregates improved the interfacial bonding strength, which increased with the increasing roughness. Based on the test results, the limits of the strength grade of joint concrete and the roughness of washed rough surface are proposed to get the interfacial bonding strength equivalent to the tensile strength of precast concrete. Meanwhile, the spraying of binder paste on precast concrete is a good choice, the storage time of precast components is a better limit within 28 days.

The influence of the binder type & aggregate nature on the electrical resistivity of conventional concrete

Concrete has been largely used in civil engineering due to its interesting fresh and hardened state properties. The 28-day compressive strength is the most important concrete property, being frequently used as an indicator of the material's quality. In this context, early-age mechanical properties (e.g., compressive strength) are becoming more critical nowadays to optimize construction scheduling. Several advanced techniques have been proposed in this regard and among those, electrical resistivity (ER) has been showing promising results. Yet, recent literature data have evidenced that ER might be significantly influenced by a variety of parameters such as the supplementary cementing materials (SCM) type/amount and aggregates nature used in the mix. These factors can hinder the practical benchmark of concrete mixtures proportioned with distinct raw materials. This work aims to appraise the influence of the coarse aggregate nature and binder replacement/amount on concrete ER and compressive strength prediction models through ER measurements using 24 mixtures manufactured with two different coarse aggregates natures (i.e., granite and limestone), two water-to-binder ratios (i.e., 0.6 and 0.4), and incorporating two different SCMs (i.e., slag, and fly-ash class F) with different replacement levels. Three distinct ER techniques (e.g., bulk, surface, and internal) and compressive strength tests were performed at different concrete ages (i.e., 3, 7, 14, and 28 days). Results indicated that the binder type and replacement amount significantly affect ER and compressive strength. The coarse aggregate nature presented minor influence for “ordinary” quality mixtures, while showing important impact on refined microstructure mixes. Finally, ER techniques, especially internal ER, were found to be quite reliable to predict the compressive strength of conventional concrete made of single, binary, and ternary binder blends. • The electrical resistivity (ER) setup highly influences the test outcomes. • The SCMs type and replacement amount significantly impacts on ER results. • The coarse aggregate nature does influence on the ER of low-quality mixtures. • The coarse aggregate nature affects ER of mixtures with refined microstructure.

PENGUJIAN KUAT TEKAN BETON TERHADAP PENGGUNAAN CANGKANG KEMIRI PADA BETON RAMAH LINGKUNGAN

One of the factors of economic growth is the development of infrastructure to encourage the creation of various activities. Concrete becomes an important part in the process of infrastructure development. For the concrete mixture, gravel is the most important part for concrete constituents. The limitation of gravel in nature led to the creation of various studies to replacement solutions for the use of gracel in concrete mixtures.Candlenut shell is one of the waste is not getting attention in its uses. Department of Plantation North Sumatera Province recorded the candlenut production in North Sumatera in 2019 reached 13,529.40 tons. The study aims for replace some of the gravel in the concrete mixture by using a candle nut shell. The variety of concrete mixture with candle nut is 10%, 20% and 30%. Testing was conducted on concrete ages 7 days, 14 days, 21 days and 28 days aimed at finding the difference between normal concrete compressive strength without additional candlenut shells and concrete with additional candlenut shells. The result shows that there was a decrease in the values of concrete compressive strength for each group of test objects. The decrease is due to the candlenut shell having higher and water absorption compared to gravel.

PENGUJIAN KUAT TEKAN BETON TERHADAP PENGGUNAAN CANGKANG KEMIRI PADA BETON RAMAH LINGKUNGAN

One of the factors of economic growth is the development of infrastructure to encourage the creation of various activities. Concrete becomes an important part in the process of infrastructure development. For the concrete mixture, gravel is the most important part for concrete constituents. The limitation of gravel in nature led to the creation of various studies to replacement solutions for the use of gracel in concrete mixtures.Candlenut shell is one of the waste is not getting attention in its uses. Department of Plantation North Sumatera Province recorded the candlenut production in North Sumatera in 2019 reached 13,529.40 tons. The study aims for replace some of the gravel in the concrete mixture by using a candle nut shell. The variety of concrete mixture with candle nut is 10%, 20% and 30%. Testing was conducted on concrete ages 7 days, 14 days, 21 days and 28 days aimed at finding the difference between normal concrete compressive strength without additional candlenut shells and concrete with additional candlenut shells. The result shows that there was a decrease in the values of concrete compressive strength for each group of test objects. The decrease is due to the candlenut shell having higher and water absorption compared to gravel.

Dynamic behavior of corroded RC slabs with macro-level stochastic finite element simulations

The reliability of reinforced concrete (RC) structures can be estimated based on the required capacity ratio. The structural demand increases with population growth and climate change, while the capacity is reduced by rebar corrosion and concrete deterioration. Several engineering structures (e.g., bridges deck and harbors) are susceptible to both corrosion and dynamic/impact loads. Therefore, the objective of this paper is to investigate the dynamic behavior of RC slabs with corroded reinforcement, and potential concrete deterioration. For this purpose, the RC slab is subjected to accelerated corrosion test using constant current technique. The corroded and sound slabs are then tested under the low-velocity impact load. A simple yet practical macro-scale finite element model is prepared which includes the concrete damage model, reduction in reinforcement diameter, and volumetric change in the rust. Global numerical responses show a satisfactory correlation with experiments, while the differences in damage pattern can be attributed to the heterogeneous deterioration in concrete and rebar. Subsequently, a large number of parametric and stochastic simulations are performed assuming different degrees of corrosion for rebars, various arrangements, non-uniform corrosion, homogeneous, and heterogeneous concrete deterioration. Results indicate that rebar corrosion, as well as concrete aging, has a crucial effect on structural capacity. Moreover, the random fields theory is an efficient technique to simulate the heterogeneity of concrete.

Experimental Investigations On Mechanical And Durability Properties Of Blended Concrete

Concrete is extensively used as a building material due to its low cost and versatility. We are expecting better results in the current construction scenario in a short time and to finish the work fast. So instead of using ordinary Portland cement here we use specially graded cement OPC 53-S cement which not only gives early age strength but also resists durability in addition to controlling the pollution emitted by cement manufacturing, we use GGBS as cementitious material which is a waste product from steel and iron manufacturing. Since GGBS setting time is slow, the OPC 53-S cement is used to compensate it. This project aims to know the mechanical properties such as compressive strength, size effect, flexural strength, splitting tensile strength and durability properties of concrete such as Sorpitivity, water absorption and carbonation by replacing GGBS in cement at different percentage (0%, 10%, 20%, 30%, 40%, 50%) levels by testing at different (3,7,14,28,56 and 90 days) age of concrete. And to know the micro structural and crystalline properties of (7 and 28 days) age of concrete by means of X-ray diffraction test.

Elements of Pathway for Quick and Reliable Health Monitoring of Concrete Behavior in Cable Post-Tensioned Concrete Girders.

The paper discusses the problems connected with long-term exploitation of reinforced concrete post-tensioned girders. The scale of problems in the world related to the number of cable post-tensioned concrete girders built in the 1950s and still in operation is very large and possibly has very serious consequences. The paper presents an analysis and evaluation of the results of measurements of the deflection and strength and homogeneity of concrete in cable–concrete roof girders of selected industrial halls located in Poland, exploited for over 50 years. On the basis of the results of displacement monitoring in the years 2009–2020, the maximum increments of deflection of the analyzed girders were determined. Non-destructive, destructive, and indirect evaluation methods were used to determine the compressive strength of concrete. Within the framework of the indirect method recommended in standard PN-EN 13791, a procedure was proposed by the authors to modify the so-called base curve for determining compressive strength. Due to the age of the analyzed structural elements, a correction factor for the age of concrete was taken into account in the strength assessment. The typical value of the characteristic compressive strength is within the range 20.3–28.4 MPa. As a result of the conducted tests, the concrete class assumed in the design was not confirmed, and its classification depended on the applied test method. The analyzed girders, in spite of their long-term exploitation, can be still used for years on the condition that regular periodical inspections of their technical condition are carried out. The authors emphasize the necessity for a permanent and cyclic diagnostic process and monitoring of the geometry of girders, as they are expected to operate much longer than was assumed by their designers.

Experimental and numerical studies of six small-scale continuous concrete slabs subjected to travelling fires

This paper presents the experimental results of six small-scale continuous reinforced concrete slabs with three compartments subjected to various compartment fire scenarios. The study investigates the influence of several key factors, including concrete age, thickness (span-thickness ratio), applied loads, and fire scenarios, on the fire behaviour of the continuous slabs. A nonlinear finite element program, Vulcan, was used to predict the fire behaviour of three tested slabs where spalling did not appear. The results indicated that increasing the slab thickness is one of the most effective methods for enhancing the fire resistance performance of continuous slabs subjected to any fire scenario. As the span-thickness ratio increased, the applied load had an increasingly significant effect on the deflection trend and maximum deflection of each span in the continuous slab. The conventional temperature failure criteria should be modified to consider the detrimental effects of fire-spreading scenarios, particularly the effects of a time delay and the direction of fire spreading. The numerical results revealed that, for any fire scenario, larger thermal straining leads to a larger mid-span deflection in continuous slabs subjected to various travelling fires.

Effect of high temperature on SCC containing fly ash

The effect of high temperature on self-compacting concrete, which contains different amounts of fly ash, has been investigated. By considering the effect of concrete age and increased temperatures, the optimum fly ash-cement ratio for the optimum concrete strength is determined using experimental studies. Self-compacting concrete specimens are produced, with fly ash/cement ratios of 0%, 20% and 40%. Specimens were cured for 28, 56 and 90 days. After curing was completed, the specimens were subjected to temperatures of 20°C, 100°C, 400°C, 700°C and 900°C for three hours. After the cooling process, tests were performed to determine the unit weight, ultrasonic pulse velocity and compressive strength of the specimens. According to the experiment results, an increase in fly ash ratio causes a decrease in the compressive strength of self-compacting concrete. However, it positively contributes to self-compaction and strength loss at high temperatures. The utilization of fly ash in concrete significantly contributes to the environment and the economy. For this reason, the addition of 20% fly ash to concrete is considered to be effective.

Enhancing Tensile Strength and Porosity of Self Compacting Concrete (SCC) with Glass Waste Powder

Utilization of glass waste powder is an alternative material as a substitute for some cement in SCC concrete because the element contained in the glass waste powder has similarities with cement. Research on glass waste powder as a substitute for some cement using percentage variation that is 5%, 10%, 15%, 20%, 25%, and 30%, with the age of SCC concrete 28 days. The study uses quantitative methods to obtain data on the tensile strength and porosity of the SCC concrete with glass waste powder as a partial substitute for cement. A tensile strength using a cylinder-shaped sample of 150 mm diameter and 300 mm in height with a sample amount per percentage of 4 pieces. The porosity test uses a cylinder-shaped sample of 150 mm in diameter and 300 mm in height with a sample number of each 4 pieces. The results of the study acquired a significant influence of the addition of glass waste powder to strong tensile and porosity of the SCC. Besides, it also obtained the optimal percentage value of the addition of glass waste powder to tensile strength concrete of 5.5% with a maximum value of tensile strength 3.422 MPa. For porosity obtained the optimal percentage value of glass waste powder at 8.583% with a porosity value of at least 9.806%.

Modified concrete mix design using Sikacim, Sika Bonding, Lumajang Sand and Silica Sand

The development of construction makes concrete a common and important building material used. Concrete is a composite material consisting of a mixture of aggregate cement, water with or without the use of added ingredients. In this era, concrete added materials are needed to meet construction needs. One of the added ingredients is Sikacim Concrete Additive and Sica Bonding Adhesive. Sikacim is able to accelerate hardening of concrete while sica bonding is able to increase adhesion. In addition to added materials, the quality of concrete constituent materials also influences the manufacturing of concrete. This study aims to modify the proportion of concrete mix using Lumajang sand and silica sand with the addition of added ingredients Sikacim Concrete Additive and Sica Bonding Adhesive. The test specimen used is in the form of a cube with a size of 15x15x15 cm. The method used is an experimental method with compressive strength testing carried out when the age of concrete reaches 3, 7,14, and 28 days. Compressive strength testing using universal testing machine. Testing results optimum obtained compressive strength value generated is 944 kg/cm2 in 28 days.