The influence of temperature and time on fresh concrete and on the latent properties of hardened concrete

1990 ◽  
pp. 245-251
Keyword(s):  
Fresh Concrete ◽  
Hardened Concrete ◽  
Influence Of Temperature

scholarly journals Consistency and mechanical properties of sustainable concrete blended with brick dust waste cementitious materials

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
S. Y. Amakye ◽  
S. J. Abbey ◽  
A. O. Olubanwo
Keyword(s):  
Tensile Strength ◽  
Fresh Concrete ◽  
Environmental Benefits ◽  
Partial Replacement ◽  
Target Range ◽  
Hardened Concrete ◽  
Index Test ◽  
Demolition Waste ◽  
Concrete Mix ◽  
Brick Dust

AbstractThe reuse of waste materials in civil engineering projects has become the topic for many researchers due to their economic and environmental benefits. In this study, brick dust waste (BDW) derived from cutting of masonry bricks and demolition waste which are normally dumped as land fill is used as partial replacement of cement in a concrete mix at 10%, 20% and 30% respectively, with the aim of achieving high strength in concrete using less cement due to the environmental problems associated with the cement production. To ascertain the effects of BDW on the consistency and mechanical performance of concrete mix, laboratory investigations on the workability of fresh concrete and the strength of hardened concrete were carried out. Slump and compaction index test were carried out on fresh concrete mix and unconfined compressive strength (UCS) test and tensile strength test were conducted on hardened concrete specimen after 7, 14 and 28 days of curing. The results showed high UCS and tensile strength with the addition of 10% BDW to the concrete mix, hence achieving the set target in accordance with the relevant British standards. A gradual reduction in strength was observed as BDW content increases, however, recording good workability as slump and compaction index results fell within the set target range in accordance with relevant British standards. Findings from this study concluded that BDW can partially replace cement in a concrete mix to up to 30% igniting the path to a cleaner production of novel concrete using BDW in construction work.

scholarly journals Effect of Water Cement Ratios on Compressive Strength of Palm Kernel Shell Concrete

2019 ◽  
Vol 2 (Issue 1) ◽  
Author(s):  
A.O Adeyemi ◽  
M.A Anifowose ◽  
I.O Amototo ◽  
S.A Adebara ◽  
M.Y Olawuyi
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Fresh Concrete ◽  
Palm Kernel ◽  
Hardened Concrete ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Palm Kernel Shell ◽  
Compressive Strength Of Concrete ◽  
Palm Kernel Shells

This study examined the effect of varying water cement ratio on the compressive strength of concrete produced using palm kernel shell (PKS) as coarse aggregate at different replacement levels. The replacement levels of coarse aggregate with palm kernel shells (PKS) were 0%, 25%, 50%, and 100% respectively. PKS concrete cubes (144 specimens) of sizes 150mm x 150mm x 150mm were cast and cured in water for 7, 14, 21 and 28 days respectively. A mix ratio of 1:2:4 was adopted with water-cement ratio of 0.45, 0.5, and 0.6 respectively while the batching was done by weight. Slump test was conducted on fresh concrete while compressive strength test was carried out on the hardened concrete cubes using a compression testing machine of 2000kN capacity. The result of tests on fresh concrete shows that the slump height of 0.45 water cement ratio (w/c) increases with an increase in PKS%. This trend was similar to 0.50 and 0.60 w/c. However, the compressive strength of concrete cube decreases with an increase in w/c (from 0.45 to 0.60) but increases with respect to curing age and also decreases with increase in PKS%. Concrete with 0.45 water-cement ratio possess the highest compressive strength. It was observed that PKS is not a good substitute for coarse aggregate in mix ratio 1:2:4 for concrete productions. Hence, the study suggest the use of chemical admixture such as superplasticizer or calcium chloride in order to improve the strength of palm kernel shells-concrete.

Grip of Mature and Fresh Concrete with Heat Treatment in Winter Conditions

2020 ◽  
Vol 992 ◽  
pp. 111-117
Author(s):  
V.V. Molodin ◽  
S.E. Sarafyan ◽  
D.S. Kasyanova
Keyword(s):  
Sea Water ◽  
Fresh Concrete ◽  
Protective Layer ◽  
Cement Clinker ◽  
Hardened Concrete ◽  
Climatic Zones ◽  
Winter Conditions ◽  
Sulfide Corrosion ◽  
Port Infrastructure ◽  
Mixing Water

Port infrastructure facilities, located in cold climatic zones in contact with sea water, are destroyed due to carbonation of concrete and sulfide corrosion. The restoration of the reinforcement protective layer by standard methods does not provide high-quality grip of the concrete structures that has undergone destruction and the repair concrete. The study of the “old” and “new” concrete grip using forced heating of the “new” one shows that mixing water with cement clinker components dissolved in it penetrates through the pores and capillaries deep into the “old” concrete to a depth of 60–70 mm under the temperature factor influence. After hardened concrete got its standard strength, it exceeds concrete grip, hardened under normal conditions by 30%.

Kansas Water-Cement Ratio Meter: Preliminary Results

1996 ◽  
Vol 1532 (1) ◽  
pp. 73-79
Author(s):  
Mustaque Hossain ◽  
James Koelliker ◽  
Hisham Ibrahim ◽  
John Wojakowski
Keyword(s):  
Fresh Concrete ◽  
Accurate Determination ◽  
Hardened Concrete ◽  
Cement Slurry ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Concrete Mix ◽  
Predominant Factor ◽  
The One ◽  
Strength And Durability

The water-cement ratio of fresh concrete is recognized as the one factor that affects the strength and durability of an adequately compacted concrete mix. Although water-cement ratio is the predominant factor affecting strength of hardened concrete, currently no widely used, reliable method is available for measuring water-cement ratio in the field. A prototype device has been developed to measure the water-cement ratio of a plastic concrete mix. The method is based on the measurement of turbidity of water-cement slurry separated out of a concrete mixture by pressure sieving. Consistent results were obtained for air-entrained and non-air-entrained concrete. Statistical analyses of the test results have shown that this meter can measure the water-cement ratio of fresh concrete with an accuracy of ±0.01 on the water-cement ratio scale for a single test at a 90 percent confidence interval. The equipment will cost less than $10,000. If the method works as well in the field as it does in the laboratory, accurate determination of water-cement ratio could dramatically improve the ability of the concrete industry to ensure the quality of concrete construction.

Impact of Steel Fibers on Workability and Properties of UHPC

2016 ◽  
Vol 249 ◽  
pp. 57-61 ◽  
Author(s):  
Milan Rydval ◽  
Tomáš Bittner ◽  
Jiří Kolísko ◽  
Šárka Nenadálová
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
High Performance Concrete ◽  
Volume Fraction ◽  
Fresh Concrete ◽  
Mixture Design ◽  
Steel Fibers ◽  
Hardened Concrete ◽  
Hardened Cement ◽  
The Impact

This paper is focused on properties of fresh and hardened cement-based composite Ultra-High Performance Concrete with regard to different volume fraction of short brass coated steel fibers BASF MASTERFIBER® 482. Workability of fresh concrete and basic mechanical properties (tensile strength in bending, compressive strength) of hardened UHPC were found out. The workability of fresh concrete was measured by small mortar Haegermann cone. Percentage differences at cost were obtained at hardened concrete, too. The aim of the first experimental part of the research was the impact of volume fraction of steel fibers according to workability of fresh concrete and also according to mechanical properties of hardened UHPC with the same volume fraction of each component of the mixture, only the volume fraction of the steel fibers was different at each mixture. The mixture design of UHPC was changed to maintaining the workability of fresh concrete at the second part of the research. The workability at mixture with dosage of steel fibers of 300 kg/m3 measured by Haegermann cone was around 300 mm. In the framework of grant project GAČR 15-05791S the basic mechanical properties of hardened fine-grained cementitious composite material UHPC at small beams size of 160/40/40 mm and beams size 300/70/70 mm were determined. The aim of the research project was not only the determination of basic mechanical properties for each mixture design but also workability assessment and costs linked with higher amount of the volume fracture of steel fibers.

The Influence of W/C Ratio and Superplasticizer Type on Porosity of Concrete with Air-Entraining Cement with Fly Ash

2018 ◽  
Vol 279 ◽  
pp. 266-270
Author(s):  
Beata Łaźniewska-Piekarczyk
Keyword(s):  
Fly Ash ◽  
Fresh Concrete ◽  
Air Entrainment ◽  
Hardened Concrete ◽  
Research Results ◽  
Concrete Mix ◽  
European Standards ◽  
New Generation ◽  
Air Entrained Concrete

The research results of stability of air-entrainment of concrete acc. PN-EN 480-1 in case of innovate air-entraining multi-component cement CEM II/B-V is presented in the paper. The influence of PCE, naphthalene and phosphonamidite based superplasticizers and w/c ratio: 0.45, 0.50 and 0.55 on air-entrainment and consistency of fresh concrete mix was investigated. The research results indicated that with increasing w/c ratio the air-entrainment of concrete increases. Moreover, in case of an increase in the degree of liquidity of the air-entrained concrete made of participation of the innovative, air-entraining multi-component cement CEM II/B-V, first and new generation superplasticizers based on modified naphthalene, and then modified phosphonamidite should be used. PCE based superplasticizer cause the too high air-entrainment of concrete. The research results proved, that the porosity of hardened concrete meets the European standards for frost-resistant concrete.

Performance of Concrete Made with Recycled Aggregates from Portuguese CDW Recycling Plants

2014 ◽  
Vol 634 ◽  
pp. 193-205 ◽  
Author(s):  
Miguel Bravo ◽  
Jorge de Brito ◽  
Jorge Pontes ◽  
Luís Evangelista
Keyword(s):  
Fresh Concrete ◽  
Penetration Resistance ◽  
Chloride Penetration ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Concrete Compressive Strength ◽  
Performance Loss ◽  
Experimental Campaign ◽  
Significant Performance ◽  
Chloride Penetration Resistance

The objective of this research is the production of concrete with recycled aggregates (RA) from various CDW plants around Portugal. The influence of the RA collection location and consequently of their composition on the characteristics of the concrete produced was analysed. In the mixes produced in this research RA from five plants (Valnor, Vimajas, Ambilei, Europontal and Retria) were used: in three of them coarse and fine RA were analysed and in the remaining ones only coarse RA were used. The experimental campaign comprised two tests in fresh concrete (cone of Abrams slump and density) and eight in hardened concrete (compressive strength in cubes and cylinders, splitting tensile strength, modulus of elasticity, water absorption by immersion and capillarity, carbonation and chloride penetration resistance). It was found that the use of RA causes a quality decrease in concrete. However, there was a wide results scatter according to the plant where the RAs were collected, because of the variation in composition of the RA. It was also found that the use of fine RA causes a more significant performance loss of the concrete properties analysed than the use of coarse RA.

scholarly journals Bond strength between stell-concrete and between concretes with different ages in structural rehabilitation

2015 ◽  
Vol 8 (5) ◽  
pp. 604-624
Author(s):  
M. R. DORIA ◽  
A. T. C SALES ◽  
N. F. de A. ANDRADE
Keyword(s):  
Bond Strength ◽  
Fresh Concrete ◽  
Tensile Tests ◽  
Bond Stress ◽  
Vertical Shear ◽  
Hardened Concrete ◽  
Pull Out ◽  
Steel Bar ◽  
Different Ages ◽  
Indirect Tensile

ABSTRACTIn inspections of buildings, it is common to find structures that, well before reaching its useful life longer require repairs and reinforcements. This study examined the bond strength between concrete of different ages and between steel and concrete, focusing on the recovery of reinforced concrete structures. To analyze the bond between concrete of different ages, trials with specimens receiving three different types of treatments at the interface between the concrete were performed: brushing; brushing and mortar equal to concrete of substrate and brushing and epoxy layer. Indirect tensile tests and oblique and vertical shear tests at the interface were made . The bond stress between steel and concrete was evaluated by pull out test under the conditions of the bar inserted in the still fresh concrete and when inserted in the hardened concrete with epoxy. Results showed increased bond strength by indirect tensile stress of 15% and 37%; 4% and 12% for the adherence test by oblique shear, and 108% and 178%, for the testing of vertical shear, respectively, for the specimens whose interfaces have received, in addition to brushing, layer of mortar and epoxy bridge, compared to those who received only brushing. Insignificant loss (about 0.52%) of bond stress was noticed for pull out test of steel bar when compared with test results of the specimens that had steel bar inserted in the concrete in the hardened state with epoxy adhesion bridge, with those who had inserted steel bar in fresh concrete.

Rice Husk Ash as Fine Aggregate Sustainable Material for Strength Enhancement of Conventional and Self Compacting Concrete

2016 ◽  
Vol 692 ◽  
pp. 94-103
Author(s):  
S.S. Samantaray ◽  
K.C. Panda ◽  
M. Mishra
Keyword(s):  
Rice Husk ◽  
Rice Husk Ash ◽  
Fresh Concrete ◽  
Partial Replacement ◽  
Hardened Concrete ◽  
Fine Aggregate ◽  
Self Compacting Concrete ◽  
Strength Enhancement ◽  
Slump Flow ◽  
Concrete Property

Rice husk ash (RHA) is a by-product of the rice milling industry. Near about 20 million tonnes of RHA is produced annually which creates environmental pollution. Utilization of RHA as a supplementary cementitious material adds sustainability to concrete by reducing CO2 emission of cement production. But, the percentage of utilization of RHA is very less. This paper presents the results of an experimental investigation to study the effects of partial replacement of fine aggregate with RHA on mechanical properties of conventional and self-compacting concrete (SCC). The fine aggregate is replaced by RHA in conventional concrete (CC) with six different percentage by weight such as 0%, 10%, 20%, 30%, 40% and 50% having w/c ratio 0.375 with variation of super plasticiser dose, whereas in SCC the replacement of fine aggregate by RHA is 0%, 10%, 20%, 30%, 40%. The design mix for CC is targeted for M30 grade concrete. The fresh concrete test of SCC is conducted by using slump flow, T500, J-ring, L-box, U-box and V-funnel to know the filling ability, flow ability and passing ability of SCC. As fresh concrete property concerned, the result indicates that the slump flow value satisfied the EFNARC 2005 guidelines upto 30% replacement of fine aggregate with RHA whereas 40% replacement did not satisfy the guideline. As hardened concrete property concerned, the compressive strength, split-tensile strength and flexural strength of CC and SCC are determined at 7, 28 and 90 days. The test result indicates that upto 30% replacement of fine aggregate with RHA enhances the strength in CC whereas the strength enhancement in SCC upto 20% replacement.

Preparation of High-Performance Concrete for Adjusting of Possibility of its Usage in Building Practice

2016 ◽  
Vol 722 ◽  
pp. 298-304 ◽  
Author(s):  
Matej Špak
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Fresh Concrete ◽  
Local Source ◽  
Hardened Concrete ◽  
Building Practice ◽  
Source Materials ◽  
Limited Possibility

Technology of High-Performance Concrete (HPC) presents one of advanced concrete technologies. In comparison to common concrete, HPC is characterized by much better qualitative parameters both for fresh and hardened concrete. However, utilization of adequate materials as well as specific processes of both the production and handling of fresh concrete is required to achieve the above standard parameters of concrete. Currently, limited possibility of utilization of local source materials with applicable parameters curtails wider production of HPC within the building practice. Results of experimental approval of HPC properties which was prepared from local aggregates are presented in the paper. Used aggregates have not appropriate parameters for application into HPC on its face. Therefore the achieved results show the potential of its applied utilization.

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