scholarly journals Effect of Formwork Removal Time Reduction on Construction Productivity Improvement by Mix Design of Early Strength Concrete

2020 ◽  
Vol 10 (20) ◽  
pp. 7046
Author(s):  
Taegyu Lee ◽  
Jaehyun Lee ◽  
Jinsung Kim ◽  
Hyeonggil Choi ◽  
Dong-Eun Lee
Keyword(s):  
Portland Cement ◽  
Concrete Strength ◽  
Raw Material ◽  
Temperature History ◽  
Unit Weight ◽  
Productivity Improvement ◽  
Study Materials ◽  
Removal Time ◽  
Early Strength ◽  
Time Required

In this study, we examined the effects of cement fineness, SO3 content, an accelerating agent, and chemical admixtures mixed with unit weights of cement on concrete early strength using concrete mixtures. C24 (characteristic value of concrete, 24 MPa) was used in the experiment conducted. Ordinary Portland cement (OPC), high fineness and SO3 OPC (HFS_OPC), and Early Portland cement (EPC) were selected as the study materials. The unit weights of cement were set to OPC 330, 350, and 380. Further, a concrete mixture was prepared with a triethanolamine (TEA)-based chemical admixture to HFS. A raw material analysis was conducted, and the compressive strength, temperature history, and maturity (D∙h) were examined. Then, the vertical formwork removal time was evaluated according to the criterion of each country. Finally, the time required to develop concrete strength of 5 MPa was estimated. Results showed that the early strength of concrete mixed with HFS and EPC was greater than that exhibited by concrete with an increased unit weight of cement with OPC. In addition, when HFS was used with EPC, its strength developed early, similar to the trend exhibited by EPC, even at low temperatures.

scholarly journals The Effects of Fineness and TEA-Based Chemical Admixture on Early Strength Development of Concrete in Construction Site Applications

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2027
Author(s):  
Taegyu Lee ◽  
Jaehyun Lee ◽  
Hyeonggil Choi ◽  
Dong-Eun Lee
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Concrete Strength ◽  
Raw Material ◽  
Strength Development ◽  
Type I ◽  
Chemical Admixtures ◽  
Chemical Admixture ◽  
Early Strength ◽  
Time Required

This study examines effects of cement fineness and chemical admixtures of early strength agents on the early strength development of concrete. Three cement types were selected, namely ASTM type-I ordinary Portland cement (OPC), fineness ordinary Portland cement (FOPC), and ASTM type-III early Portland cement (EPC), and the mixing proportions of concrete were set by adding a triethanolamine-based chemical admixture to FOPC. The evaluation items considered in this study included raw material analysis, compressive strength, and maturity (D∙h). The time required for the development of concrete strength of 5 MPa in the three cement types was estimated and compared. The results revealed that using FOPC enhances the strength development of concrete owing to its higher fineness and SO3 content compared to OPC. In addition, it has been observed that using both FOPC and TCA yields a similar performance to that observed using EPC, in light of the improved early strength development at low temperatures.

scholarly journals Improving Marine Concrete Performance Based on Multiple Criteria Using Early Portland Cement and Chemical Superplasticizer Admixture

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4903
Author(s):  
Taegyu Lee ◽  
Jaehyun Lee ◽  
Jaewook Jeong ◽  
Jaemin Jeong
Keyword(s):  
Portland Cement ◽  
Concrete Strength ◽  
Strength Development ◽  
Construction Productivity ◽  
Concrete Mix Design ◽  
Granulated Blast Furnace Slag ◽  
Chloride Resistance ◽  
Combined Use ◽  
Concrete Mix ◽  
Early Strength

This study sought to examine the performance design of concrete mix proportions to ensure chloride resistance and early strength with respect to C35 (35 MPa), which is the minimum compressive strength class of concrete used in a marine environment. For the proposed concrete mixture, C24 (24 MPa) was selected and binders for concrete were manufactured using a blend of OPC (ordinary Portland cement), EPC (early Portland cement), and GGBS (ground granulated blast-furnace slag). The results of the experiment confirmed that the combined use of EPC and GGBS greatly improve the early-strength development and chloride resistance of concrete. An analysis revealed that the time for removal of forms can be reduced by 5–9 h from the aspect of early concrete strength. Moreover, in terms of construction productivity, EPC and GGBS were reduced by up to 16.39 h/cycle compared to other concretes. Regarding economic and environmental impacts, EPC and GGBS were more effective than C35 concrete. This study is significant as its findings help make it possible to examine the most economical concrete mix design in relation to strength development according to the application of EPC, GGBS, and PC-based admixtures.

Labour Productivity in UK Manufacturing in the 1970s and in the 1980s

1990 ◽  
Vol 132 ◽  
pp. 71-91 ◽  
Author(s):  
Nicholas Oulton
Keyword(s):  
Growth Rate ◽  
Regression Analysis ◽  
Labour Productivity ◽  
Manufacturing Industries ◽  
Raw Material ◽  
Productivity Improvement ◽  
Impact Effect

What accounts for the productivity improvement experienced in manufacturing since 1979? Answers to this question are sought from a regression analysis of 93 manufacturing industries over the period 1971-86. The main findings are that when other influences, such as raw material prices and the shock of the 1980-1 recession, are eliminated, there has been an improvement in the 1980s in the growth rate of productivity whose impact effect averaged 4 per cent per annum. Between a quarter and a half of this is attributable to a decline in the disadvantages of unionisation.

A trial construction of high durability railway viaducts with local aggregates

2019 ◽  
Author(s):  
Kotaro Kawamura ◽  
Joe Takemura ◽  
Shigenobu Iguchi ◽  
Tsutomu Yoshida ◽  
Masashi Kobayashi
Keyword(s):  
Fly Ash ◽  
Side Effects ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
The Other ◽  
Strength Concrete ◽  
High Durability ◽  
Sound Barrier ◽  
Early Strength ◽  
Structural Measure

<p>We are carrying out a construction project of new railroad viaducts. These new railroad viaducts are constructing using about 110,000 m<span>3</span> volume concrete. In this construction place, it is difficult for us to get low ASR-reactive aggregates and it is expected to be supplied with snowmelt water on the viaducts in winter. Then we tested ASR-reactive these local aggregates and found an effective mixed ratio of fly-ash is 20% of cement. On the other hand, various side effects were also expected by using fly-ash. For example, initial cracking due to contraction, early strength concrete, bleeding, etc. Therefore, we repeated various tests and examined and carried out a method that could ensure the same construction method and quality as when using ordinary Portland cement, even with fly-ash. Also, we adopted a structure that is unlikely to be affected by rainwater as a structural measure. For example, the entire adoption of a ramen type viaduct that has eliminated bearings, adoption of FRP sound barrier, etc. Then we made it possible to build highly durable railway viaducts by these various measures of materials and structures.</p>

Preparation of Portland cement with sugar filter mud as lime-based raw material

2014 ◽  
Vol 66 ◽  
pp. 107-112 ◽  
Author(s):  
Haoxin Li ◽  
Wei Xu ◽  
Xiaojie Yang ◽  
Jianguo Wu
Keyword(s):  
Portland Cement ◽  
Raw Material ◽  
Filter Mud

scholarly journals Productivity Improvement by using Time Study Analysis and Modern Trends in Manufacturing Industry

2020 ◽  
Vol 4 (9) ◽  
pp. 75-79
Keyword(s):  
Material Handling ◽  
Manufacturing Industry ◽  
Manufacturing Sector ◽  
Maximum Efficiency ◽  
Maximum Output ◽  
Time Study ◽  
Work Study ◽  
Work Process ◽  
Productivity Improvement ◽  
Time Required

The productivity of any organization can be increased by optimizing the work process. Low productivity of workers is one of the reason behind the delay in delivery in manufacturing sector we know that in manufacturing sector labor is prominent thing. Improving the productivity means to make the best possible use of available resources and achieve maximum output. This paper focuses on the productivity of machine as well as labor by using fixtures, updated systematic layout and use of material handling equipment. This paper also covers the, what is productivity, which factors are affecting on productivity and efficiency. Maximum efficiency or productivity is trademark of any successful organization The objective of this paper is to identify the problem in medium scale industry due to time and effort required for any operations is high To tackle and understand a detailed analysis regarding processes using time study and work study. Due to implementation of all the measures the productivity of an organization is increases resulting in reduced effort and time required for operation and all operations done optimally.

scholarly journals Geochemical And Mineralogical Assessment Of Secondary Gypsum In Al-Najaf, Iraq And Employment As Raw Material For Cement Industry

2021 ◽  
Vol 72 ◽  
pp. 215-222
Author(s):  
Mohanad R.A. Al-Owaidi ◽  
◽  
Mohammed L. Hussein ◽  
Ruaa Issa Muslim ◽  
◽  
...  
Keyword(s):  
Portland Cement ◽  
Raw Materials ◽  
Chemical Properties ◽  
Quality Standard ◽  
Cement Industry ◽  
Raw Material ◽  
Insoluble Residue ◽  
Mineralogical Study ◽  
The Mean ◽  
Industry Success

The Portland cement industry is one of the strategic industries in any country. The basis of an industry success is the availability of raw materials and, the low extraction in addition to transportation costs. The Bahr Al-Najaf region is abundant with limestone rocks but lacks primary gypsum. An investigation had been carried out to identify the source of secondary gypsum as an alternative to primary gypsum. Twelve boreholes were drilled for a depth of 2 m, as the thickness of suitable secondary gypsum layer ranges from 1 to 1.5 m. The mineralogical study revealed the predominance of gypsum followed by quartz and calcite, with an average of 62.9%, 19.6% and 14.35%, respectively. The geochemical analysis revealed that the content of SO3 is appropriate and ranging from 41.92% to 32.89% with an average of 37.73%. The SO3 content is within an acceptable range. The mean abundance of the major oxides of the study area may be arranged as SO3 > CaO> SiO2> MgO> Al2O> Fe2O3. The insoluble residue was at an acceptable rate. The laboratory experiments for milling secondary gypsum with clinker has successfully proven the production of Portland cement that matches the limits of the Iraqi Quality Standard (IQS) No. 5 of 1984. Great care must be taken when using secondary gypsum; secondary gypsum must be mixed well to maintain the chemical properties before blending with clinker and utilizing in the cement mill in the cement plant.

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