water curing
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2021 ◽  
Vol 15 (4) ◽  
pp. 8469-8479
Author(s):  
M.A. Azed ◽  
D.S. Ing

Urban population of Malaysia is stated as 72.8% of its total population, and growing every year. Due to this growing number of population, the sewage sludge waste produce every year has also gradually increased. Malaysia itself produces 3.2 million m3 of sewage sludge annually. Normally all of this waste is disposed by landfill. Furthermore, usual production of cement and sewage sludge ash consumes a lot of energy by using incineration process with a very high temperature. Thus, microwave heating method was an alternatives use in this research to reduce the consumption of energy and time used to heat the sewage sludge ash. This research was conducted to investigate the optimum performances of different percentage (0%, 5%, 10%, 15% and 20%) by weight of cement of the Microwaved Sewage Sludge Ash (MSSA) concrete with different curing regime, which was air and water curing. The characteristic of MSSA was tested by X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The mechanical properties of MSSA concrete was examined by Compressive Strength test, Flexural Strength test and Modulus of Elasticity test after 180 days of curing. The MSSA samples were also tested with water absorption test to evaluate the quality of concrete in term of porosity and permeability. Water curing sample with 5% of MSSA (W5) had the best in results compared to other specimens. The mechanical properties of W5 content in concrete shows the most optimum samples due to the densification of pozzolanic reaction and filler effect of MSSA. The curing effect with better result was water curing, as it got highest value of strength in compressive test, flexural test and modulus of elasticity test. As conclusion, based on the results, it is shown the positive impact on using the MSSA as additional material to the cement mixture to improve the quality of the concrete. Thus, this will reduce the disposal of sewage sludge waste on dumping site and improves the quality performances of the concrete.


2021 ◽  
Vol 11 (2) ◽  
pp. 127-136
Author(s):  
Sadaf Noshin ◽  
M. Adil Khan ◽  
M. Salman ◽  
M. Shahzad Aslam ◽  
Haseeb Ahmad ◽  
...  

Abstract In construction industry, demolished construction waste is recently used as reprocessed aggregate to produce environmentally friendly concrete which is a good substitute to normal crush due to increased demand of ecological growth and conservation benefits. Though, the properties of recycled aggregate concrete are smallest as compared to concrete produced from natural aggregate and these properties can be enhanced by adding some materials having cementitious properties. Rice husk ash (RHA) is used as partial replacement of cement in recycled aggregate concrete to improve the properties as well as to conserve the natural resources. The elementary purpose of this investigation is to determine the compressive strength of concrete by the replacement of cement with different percentages of rice husk ash such as 0%, 7.5%, 10%, 12.5%, 15%, and 17.5% respectively with different curing conditions. For the experimental program approximate 198 cylinders (18 for rapid curing, 90 for normal water curing and 90 for acid curing) are casted with the mix proportion of 1:2:4 and water to cement ratio of 0.50 whereas curing is done at the ages of 3,7,14,21 and 28 days. Various experiments are performed on fresh and hardened concrete to determine the effects of rice husk ash on recycled aggregate concrete with different curing conditions. Linear regression analysis is carried out to determine the compressive strength of concrete. It is pragmatic from the slump test results that the workability of recycled aggregate concrete is decreased by increasing the quantity of rice husk ash. This reduction in slump is due to high water absorption of recycled aggregates and rice husk ash. Further, the compressive strength of recycled aggregate concrete with normal and acid curing is decreased by increasing the percentages of rice husk ash. It is also observed that at 28- days of normal water curing for mix M1,M2,M3,M4,M5 and M6 the compressive strength is increased by 0.96%, 2.74% 1.45%,4.50%,4.23% and 4.22% respectively as compared to the compressive strength values at 28 days of acid water curing. Therefore, it is concluded that recycled aggregate concrete with 10 to 12% of rice husk ash is suitable for properties of concrete. The acid water curing has negative impacts on hardened properties of concrete as it reduced the compressive strength of concrete as compared to normal water curing.


Author(s):  
Chidananda G

Abstract: This paper presents an experimental investigation on influence of different curing methods on the performance of M30 grade concrete. Different curing methods such as air curing, pond curing, intermittent curing, gunny bags curing, chemical curing and using Super Absorbent Polymer (SAP) by 0.3% of weight of cement are considered. Slump and compacting factor tests are performed to know the workability of fresh concrete. Compressive strength of hardened concrete is determined for concrete specimens cured by different curing methods. Durability in terms of carbonation resistance on hardened concrete is also performed as per IS 516 (Part 5/Sec 3, 2021) codal provisions. Depending upon the site conditions and availability of potable water, curing methods such as pond curing, intermittent curing, gunny bags curing, chemical curing and SAP curing can be adopted in site to achieve the expected strength and durability requirements. Keywords: Curing methods, Compressive strength and Carbonation resistance.


Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6630
Author(s):  
Jihun Park ◽  
Quang-The Bui ◽  
Jungwoo Lee ◽  
Changbin Joh ◽  
In-Hwan Yang

This work was designed to evaluate the interlayer strength of 3D-printed mortar with postinstalled interlayer reinforcement. Two methods of postinstalled interlayer reinforcement were considered according to the amount of overlapping. The first method did not include overlapping of the interlayer reinforcement, while the second method included overlap lengths of 20 and 40 mm. Additionally, two different curing conditions were considered: air-curing conditions and water-curing conditions. The compressive, splitting tensile, and flexural tensile strengths of 3D-printed mortar specimens with different reinforcement methods and curing conditions were investigated under three loading directions. The three loading directions were defined based on the three planes of the printed specimens. The compressive, splitting tensile, and flexural tensile strengths were dependent on the loading directions. In particular, the splitting and flexural tensile strengths decreased considerably when tensile stresses acted on the interlayers of the 3D-printed mortar specimens. However, when longitudinal interlayer reinforcement penetrated the printed layers, the flexural tensile strength or interlayer bonding strength of the printed specimens increased significantly at the interlayers. In addition, mortar specimens reinforced with overlap lengths of 20 and 40 mm were investigated in this study. The flexural tensile strength or interlayer bonding strength of 3D-printed mortar decreased after treatment under air-curing conditions because the interlayers of the printed mortar formed more pores under these conditions and were more vulnerable under loading. Finally, the findings of this study suggested that interlayer reinforcement is a potential method for improving the interlayer bonding strength of 3D-printed mortar.


2021 ◽  
Vol 921 (1) ◽  
pp. 012009
Author(s):  
P R Rangan ◽  
R Irmawaty ◽  
M W Tjaronge ◽  
A A Amiruddin ◽  
B Bakri ◽  
...  

Abstract This study aims to analyze the effect of curing on the compressive strength of geopolymer mortar made from straw ash, fly ash and laterite soil. This research is experimental in the laboratory. Geopolymer mortar was produced using straw ash, fly ash and laterite soil with a percentage ratio of 16.67: 41.67: 41.67. The alkaline activator used is sodium hydroxide (NaOH) with a concentration of 12 M. The compressive strength test of 5 × 10 cm cylinders is used to evaluate the geopolymer mortar mixture produced at the age of 3, 7 and 28 days with curing, namely air and water curing. The results showed that the compressive strength of the geopolymer mortar increased along with the increasing age of each curing. The compressive strength values produced in air curing 3, 7 and 28 days were respectively 1.64 N/mm2, 1.72 N/mm2 and 3.22 N/mm2. While water curing, the resulting compressive strength values for each curing are 1.03 N/mm2, 1.63 N/mm2 and 1.68 N/mm2. At the ages of 3, 7 and 28 days, there was an increase in the compressive strength values from water curing to air curing, which were 0.37%, 5.23% and 47.82%, respectively. It can be seen that the compressive strength of the geopolymer mortar made from straw ash, fly ash and laterite soil in air curing is greater than that of water curing.


2021 ◽  
Vol 53 ◽  
pp. 101714
Author(s):  
Bao Lu ◽  
Pingping He ◽  
Jianhui Liu ◽  
Ziyi Peng ◽  
Baixing Song ◽  
...  

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6091
Author(s):  
Hongbeom Choi ◽  
Jinman Kim ◽  
Sunmi Choi ◽  
Sungsu Kim

This study demonstrated the use of KCl separated from chlorine bypass dust (CBD) as an activator for plain concrete. The separated KCl was mixed with either ground granulated blast-furnace slag (BFS) alone, or a mixture of BFS and cement. The mixed paste of separated KCl and BFS set within 24 h, and exhibited a compressive strength of 22.6 MPa after 28 d. The separated KCl, cement, and BFS mixture exhibited a more rapid setting and a higher initial activity. Further, the compressive strength at 28 d was 57.7 MPa, which was 26.2% higher than that of the mixture without the activator. Water curing of samples with added separated KCl led to the generation of hydrocalumite, or Friedel’s salt. However, this hydrocalumite was decomposed while being cured under autoclave conditions at 180 °C. Overall, KCl was an effective activator for composite materials containing cement, and resulted in superior properties compared to mineral admixtures without an activator.


2021 ◽  
Vol 2 (4) ◽  
pp. 15-19
Author(s):  
Rashedul Haque

Disposal of plastic bottles made from Poly-Ethylene Terephthalate (PET) is a worldwide problem. Green concrete, made with one or more recycled items, is also a trendy concept in the sustainable construction sector. The current study is to investigate the possibility of using recycled PET waste bottles as a partial replacement of natural coarse aggregate in green concrete to get marginal effective compressive strength and workability. Two different sizes of PET fiber such as 10mm*10mm and 19mm*19mm are used. Four different replacement percentages such as 0% (control), 1%, 5%, and 10% of coarse aggregate are adopted with a fixed water-cement ratio of 0.42. A total of 42 cylindrical specimens are prepared and conventional water curing is done for 7 days and 28 days. Compressive strength for control specimen (0%) after 7 days and 28 days curing is found as 39.96 MPa and 53.42 MPa respectively. On the other hand, the compressive strength of specimens with 10mm*10mm plastic fiber is found to be 22.40 MPa, 16.14 MPa & 11.83 MPa after 7 days curing and 38.48 MPa, 25.81 MPa & 20.08 MPa after 28 days of curing for 1%, 5%, and 10% replacement of coarse aggregate respectively. For 19mm*19mm plastic fibers, these values are 21.22 MPa, 7.99 MPa & 4.29 MPa after 7 days of curing and 35.82 MPa, 11.36 MPa & 7.03 MPa after 28 days of curing for the same percentages. The findings of the study may serve as a guideline for deciding the replacement percentage and fiber size for preparing PET-based green concrete.


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