curing period
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2022 ◽  
Vol 3 (1) ◽  
pp. 88-102
Author(s):  
Marc Quiertant ◽  
Claude Boulay ◽  
Laurent Siegert ◽  
Christian Tourneur

This article investigates the potential detrimental effects of cyclic load during the installation of externally bonded (EB) carbon fiber-reinforced polymer (CFRP) on a damaged reinforced concrete (RC) structure. Four RC specimens were tested in three point bending to study the consequences of crack cyclic opening-closure during epoxy-curing period. A first RC specimen (without bonded CFRP) was loaded monotonically up to failure to serve as undamaged control sample. The three other specimens were pre-cracked before being subjected to a fatigue loading procedure to simulate service condition of a damaged RC structure. Two of the three pre-cracked specimens were strengthened by EB CFRP. One specimen was repaired before the fatigue test while the other one was repaired during the fatigue test. Finally, remaining capacities of all three pre-cracked specimens were measured through monotonic bending tests until failure. It was found that, although bonding of CFRP reinforcement during cyclic load can induce some interesting features with regard to serviceability, cyclic crack opening and closing alters the cure process of epoxy located below the initial crack and decreases the effectiveness of the strengthening at ultimate state. Extended experimental studies are then needed to assess reliable safety factor for the design of repairing operations in which the bridge has to be maintained in service during CFRP installation.


2022 ◽  
Vol 12 (1) ◽  
pp. 526
Author(s):  
Zeyu Li ◽  
Xiuzhi Shi ◽  
Xin Chen

It is important and difficult to improve the tensile strength of backfill material to ensure the stability of goafs. In this study, rice straw (RS) in fiber form is used to improve the tensile properties of cemented paste backfill (CPB). An orthogonal experiment was designed, Brazilian indirect tensile strength tests were conducted to test the tensile performance of RS fiber-reinforced cemented paste backfill (RSCPB) under different fiber content (1, 2, 3 kg/m3) and fiber length (0.8~1, 1~3, 3~5 cm), and the microstructure of RSCPB was analyzed with scanning electron microscopy (SEM). The results showed that, compared with the conventional cemented paste backfill (CCPB), the increase in tensile strength of RSCPB ranged from 115.38% to 300.00% at 3 days curing age, 40.91% to 346.15% at 7 days, and −38.10% to 28.00% at 28 days., and the strain was slightly reduced during the curing period. The tensile strength, strain, and percentage increase of the RSCPB compared to the CCBP did not show a monotonic pattern of variation with the RS fiber content and length during the curing period. The RSCPB samples fractured under peak stress, showing obvious brittle failure. In addition, sulfate generated from S2− in the tailings inhibits the hydration reaction, and generates swelling products that form weak structural surfaces, which, in turn, lead to a 28-day tensile strength and strain of RSCPB lower than those at 7 days.


2022 ◽  
Vol 1048 ◽  
pp. 396-402
Author(s):  
H.C. Guruprasad ◽  
R. Sridhar ◽  
R. Ravi Kumar

Cement is replaced with Ground Granulated Blast Furnace Slag (GGBS), to produce a cost effective concrete and to gain effective compressive strength. It is produced in iron manufacturing industries. It has pozzolanic properties and has particle size less than 90μ. In this experimental study, cubes of size 150×150×150 mm and cylinders of 150 mm dia and 300 mm height were casted byreplacing GGBS from dosage of 8% up to 65% for curing period of 7days, 14days, 28days and 56days for M 40 grade concrete. Also, Alccofines were added in addition in varying percentage of 3%, 6%, 9% and 12% in order to gain high early strength and increase the workability. Hyper-Plasticizers were also added in order to reduce the water-content of the concrete. The results of GGBSCC were compared with that of normal concrete results.


2021 ◽  
Vol 23 (12) ◽  
pp. 262-269
Author(s):  
Dr. R L Ramesh ◽  
◽  
Dr. Nagaraja P S ◽  
Raghavendra R ◽  
Gobinath S ◽  
...  

The Concrete is one of the most important products which are efficiently and effectively used in the field of construction. The usage of natural aggregates in the process of production of concrete was high which lead to huge deficiency of availability of the natural aggregates. At the same time production of cements leads to more environmental pollution. Therefore, the production of concrete was altered by vast usage of admixtures and replacements for natural aggregates. In this paper M60 grade concrete is prepared by using GGBS as a partial replacement of cement which is a good strength building mineral admixture, the steel fibers were also introduced in the concrete to improve the strength parameter and for ease of work with concrete and addition of AUROMIX – 400 which is provided by FOSROC chemicals Bengaluru as super plasticizers. The concrete specimens like Cubes and Cylinders were casted and allowed to curing over a nominal curing period of 7, 14 and 28 days to know the basic mechanical properties of the concrete with the above replacements and at the same time RCC beams were also casted and cured, then post tensioned to know the flexural details of this special concrete.


Author(s):  
V. Sai Kumar ◽  
P. Hari Prasad Reddy ◽  
Ch. Rama Vara Prasad

Based on the strong evidence of case histories, this study focused on mineralogical and morphological changes of an artificial kaolinitic soil -Ball clay, when exposed to different concentrations of sodium hydroxide (0.1N, 1N, 4N, and 8N) under different curing periods (7, 28 and 100 days). Sediment volume tests are conducted on Ball clay with all combinations and results are analyzed with the help of analytical techniques. XRD and SEM studies are analyzed to understand the micro-level changes of alkali contaminated Ball clay. Mineralogical and morphological transmutations of Ball clay are investigated for 7, 28, and 100 days curing period. Results revealed new mineral formations like Sodalite under 4N and 8N concentrations of NaOH with 100 days interactions are well observed. The morphological transformation from needle shape to pellet shape is clear evidence of the rate of dissolution and precipitation of minerals under 100 days curing periods.


Foods ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2869
Author(s):  
Linjie Xi ◽  
Jing Zhang ◽  
Ruixiao Wu ◽  
Tian Wang ◽  
Wu Ding

Zhenba bacon (ZB), a type of Chinese traditional bacon with a long history, has attracted considerable attention in the Southwest of China for its unique flavor. To elucidate the changing course of aroma components during the process of ZB, four stages of process stages were assessed by GC–MS and GC–IMS coupled with multivariate data analysis. A total of 44 volatile compounds were identified by GC–IMS, including 5 esters, 8 alcohols, 12 aldehydes, 3 ketones, 1 furan and 2 sulfides; 40 volatile compounds were identified by GC–MS, 4 ketones, 7 phenols, 8 alcohols, 6 esters, 6 aldehydes, and 6 other compounds were detected. During the curing period, the amount and content of esters in Zhenba bacon gradually increased. Phenols appear in large quantities during the smoking period. The VOCs (volatile organic compounds) in the gallery plots were the most diverse in YZ samples, which are mainly esters. POV (peroxide value) and TBARS (thiobarbituric acid reactive substance) showed that lipid oxidation played an important role in the formation of volatile flavor components of bacon. This study provides valuable analytical data to explain the flavor formation of Zhenba bacon.


2021 ◽  
Vol 1197 (1) ◽  
pp. 012036
Author(s):  
Mohammed Khadeer ◽  
Umesh K Singh

Abstract The adverse effect of greenhouse emissions like CO2 leads to global warming. As per statistics, the global contribution of the cement manufacturing industry to greenhouse gas emissions is nearly 7%. To address these effects on the nature of the environment associated with cement manufacturing, it is necessary to explore sustainable binders for manufacturing concrete. Hence, extensive research is being conducted in the recent past to replace cement with various materials including waste generated from various sectors. Further, the replacement of fine aggregates and cement in concrete with various proportions of powdered glass is an engrossing topic among researchers for over a decade. The present study aims to the optimal use of glass powder in concrete as a replacement for cement and to enhance the characteristics compressive strength when compared to conventional concrete. Cement was replaced by various percentages of fine glass powder ranging from 10-50 % at an increment of 10%. The concrete cube specimens for 7 and 28 days were evaluated for their compressive strength after curing period, with that of conventional concrete. From the acquired results, it is perceptible that glass powder can be a suitable replacement for cement.


Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1291
Author(s):  
Jing-Shuang Zhang ◽  
Xiang-Gang Xia ◽  
Bin Ren

To study the influences of curing period and sulfate concentration on the dynamic mechanical properties of cement soil, this study used a split Hopkinson pressure bar device. Impact tests were conducted on cement soil specimens with different curing periods and different sulfate concentrations. The relationships between the dynamic stress–strain, dynamic compressive strength, and absorption energy of these cement soil specimens were analyzed. The test results show that with continuous loading, cement soil specimens mainly experience an elastic stage, plastic stage, and failure stage; with increasing curing period and sulfate concentration, the dynamic compressive strength and absorption energy of cement soil specimens follow a trend of first increasing and then decreasing. The dynamic compressive strength and absorption energy of cement soil specimens reached maximum values at a curing period of 14 d and a Na2SO4 solution concentration of 9.0 g/L. Increasing the dynamic compressive strength and absorption energy can effectively improve the ability of cement soil specimens to resist damage. This paper provides a practical reference for the application of cement soil in dynamic environments.


Ceramics ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 600-617
Author(s):  
Kong Fah Tee ◽  
Sayedali Mostofizadeh

In this study, the compressive strength and the permeation properties of fly ash-based Geopolymer were experimentally investigated. Type 2 Portland cement (T2PC) was partially or entirely replaced with 0, 10, 20, 30, 50, 70, and 100% of fly ash (FA). The laboratory tests were conducted for compressive strength at 7, 28, and 90 days, and permeation properties such as water absorption at 7 and 28 days. The main goal was to produce eco-friendly concrete with high strength and low permeability through blending cementitious materials including low Calcium (Ca) (T2PC and FA) for protecting concrete against sulphate attacks and other chemically destructive compounds in the environment. This study focused on the effectiveness of the curing period, combinations of chemical activators by varying the molarity of alkaline solutions between 4.16 and 12.96 M and keeping the sodium silicate (SS) to sodium hydroxide (SH) by the weight ratio of 2.5. Lab observations from this study demonstrated that the compressive strength was enhanced with the increment in fly ash content at all ages, with optimum being at 20% as the replacement of T2PC.


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