scholarly journals Use of admixture effectiveness curves for prediction of the compressive strength of concrete

2018 ◽  
Vol 3 (21) ◽  
pp. 175-182
Author(s):  
Agnieszka Grzybowska ◽  
Łukasz Mrozik
Keyword(s):  
Compressive Strength ◽  
Bulk Density ◽  
Cement Paste ◽  
Water Demand ◽  
Laboratory Tests ◽  
Science And Technology ◽  
Individual Laboratory ◽  
Compressive Strength Of Concrete ◽  
The University

This paper presents the results of individual laboratory tests conducted in the Research and Experiment Facility of the University of Science and Technology in Bydgoszcz, in particular of tests conducted on pastes of low water-binder ratios (from 0.2 to standard water demand (Mrozik 2012)). The purpose of this document is to examine the effect of the applied admixtures (plasticizer or superplasticizer) and its amount on the bulk density of a cement paste, thus on the compressive strength of concrete (as shown in the paper (Neville 2012), properties of concrete can be estimated on the basis of pastes). Conclusions concerning the suitability of specific amounts of plasticisers and superplasticizers were formulated and effectiveness curves were established on the basis thereof.

scholarly journals Hydraulic Performance Analysis and Modeling of Water Supply Distribution System of Addis Ababa Science and Technology University, Ethiopia

2020 ◽  
Author(s):  
Chalchisa Milkecha ◽  
Habtamu Itefa
Keyword(s):  
Water Supply ◽  
Water Demand ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Addis Ababa ◽  
Science And Technology ◽  
Hydraulic Performance ◽  
Alternative Methods ◽  
The University

This study was conducted generally by aiming assessment of the hydraulic performance of water distribution systems of Addis Ababa Science and Technology University (AASTU). In line with the main objective, this study addressed, (1) pinpointing problems of existing water supply versus demand deficit (2) evaluating the hydraulic performance of water distribution system using water GEMS and (3) recommended alternative methods for improving water demand scenarios. The University’s water supply distribution network layout was a looped system and the flow of water derived by both gravity and pressurized system. The gravity flow served for the academic and administrative staffs whereas the pressurized system of the network fed the students dormitories, cafeteria’s etc. The study revealed the existence of unmet minimum pressure requirement around the student dormitories which accounts 25.64% below the country’s building code standard during the peak hour consumption. The result of the water demand projection showed an increment of 2.5 liter per capita demand (LPCD) in every five years. Hence, first, the university’s water demand was projected and then hydraulic parameters such as; pressure, head loss and velocity were modeled for both the existing and the improved water supply distribution. The finding of the study was recommended to the university’s water supply project and institutional development offices for its future modification and rehabilitation works.

scholarly journals Effect of ultrafine natural steatite powder, super plasticizer and VMA on the fresh and hardened properties of self-compacting cement paste and mortar

2021 ◽  
Author(s):  
S. Christopher Gnanaraj ◽  
Ramesh Babu Chokkalingam ◽  
G. Lizia Thankam ◽  
S.K.M. Pothinathan
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Water Demand ◽  
Construction Material ◽  
Setting Time ◽  
Mineral Admixture ◽  
Self Healing ◽  
Chemical Admixtures ◽  
Hardened Properties ◽  
Viscosity Modifying Admixture

AbstractFor the past few decades innovation in construction material has grown a lot. This leads to special concrete such as self-compacting concrete, geopolymer concrete, self-healing concrete, etc. To prepare a special concrete apart from regular concreting material some sort of special materials was also needed, like mineral and chemical admixtures. Hence it is necessary to study the effect of these admixtures in cement paste and mortar before studying the same in concrete. Hence an attempt is made to study the effect of mineral and chemical admixtures in the fresh and hardened properties of cement paste and mortar. For this study ultrafine natural steatite powder is taken as mineral admixture and polycarboxylic based superplasticizer and glenium stream 2 were taken as chemical admixtures. Ultrafine natural steatite powder was used as additive to cement in various percentages like 0%, 5%, 10%, 15%, 20% and 25%. Superplasticizer and viscosity modifying admixture were taken as 1.5% and 0.5%, respectively. Then various combinations were worked out. To study the fresh property of cement paste consistency, initial setting time and miniature slump cone test were done based on the results yield stress of cement paste also calculated empirically. To study the hardened property compression test on cement mortar was done. Based on the test results it is clear that the addition of ultrafine natural steatite powder increases the water demand hence reduces the workability. On the other hand, it increases the compressive strength up to a certain limit. Adding superplasticizer increases the workability and reduces the water demand and viscosity modifying admixture reduces the bleeding and segregation effects hence increases the compressive strength.

The Study of Physical and Thermal Conductivity Properties of Cement Paste Containing Nanosilica

2015 ◽  
Vol 659 ◽  
pp. 164-168
Author(s):  
Pongsak Jittabut ◽  
Prinya Chindaprasirt ◽  
Supree Pinitsoontorn
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Bulk Density ◽  
Cement Paste ◽  
Unit Weight ◽  
Particle Sizes ◽  
Cement Pastes ◽  
Insulating Material ◽  
Surface Probe ◽  
Nanosilica Particle

This research was presented the physical and thermal conductivity properties of cement pastes containing nanosilica by mixing three nanosilica particle sizes of 12, 50 and 150 nm, using nanosilica of 1-5 wt%. The water-cementitious ratio (W/C) was 0.5 for all samples. Thermal property coefficients were tested using a direct measuring instrument with surface probe (ISOMET2114). The influence of nanosilica on the physical properties were compressive strength, bulk density, XRD and SEM respectively. The results indicated that the use of nanosilica as an admixture can reduce the thermal conductivity and lowered the bulk density of specimen. The cement paste with nanosilica particle size of 50 nm with 4 wt% nanosilica at the age of 28 days showed the optimized properties. The thermal conductivity was lowest at 0.913 W/m-K, the compressive strength was highest at 51.62 MPa and the bulk density was 1,806 kg/m3respectively. The compressive strength increases more than 50% higher than that of pure paste. The cement pastes with nanosilica particle sizes of 50 and 150 nm, have lower unit weight and thermal conductivity than typical control cement paste about 9% and 15% respectively. The nanosilica mixed cement paste is very interesting for energy saving when used as wall insulating material.

scholarly journals A Qualitative Study of Thermochemical Degradation Related with Concrete and Mortar Strength

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
José Mora-Ruacho ◽  
Humberto A. Monreal-Romero
Keyword(s):  
Compressive Strength ◽  
Thermal Equilibrium ◽  
Laboratory Tests ◽  
Qualitative Method ◽  
Calcium Content ◽  
Mortar Strength ◽  
Reported Study ◽  
Compressive Strength Of Concrete ◽  
Best Parameter ◽  
Thermochemical Reaction

The nondestructive methods applied to the evaluation of concrete use different parameters to be related in the estimated resistance of concrete or other properties. The conducted study has evaluated a qualitative method of thermochemical degradation in concrete and mortar using a solvent acid whose chemical energy is capable of degrading the material. The reported study consisted in performing laboratory tests on mechanical compressive strength of concrete and mortar and thermochemical tests performed on little cores of concrete or mortar immersed in hydrochloric acid contained in a calorimeter system, obtaining several parameters as the time of thermal equilibrium, increase of temperature, degradation energy, and mass loss due to the thermochemical reaction. From the obtained results, these variables were analyzed and served as a parameter to be related with the concrete or mortar strength. The best parameter proved to be a good estimator was the increase of temperature and its degradation energy, whose value was inversely proportional to the strength of the material. Also, it is found that the most significant mechanisms that influenced the thermochemical reaction are the calcium content and the water chemically bound in the cement paste to perform the thermochemical test.

scholarly journals Microstructure of Structural Lightweight Concrete Incorporating Coconut Shell as a Partial Replacement of Brick Aggregate and Its Influence on Compressive Strength

2021 ◽  
Vol 13 (13) ◽  
pp. 7157
Author(s):  
Hamidul Bari ◽  
Md. Safiuddin ◽  
Md. Abdus Salam
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Lightweight Concrete ◽  
Coconut Shell ◽  
Partial Replacement ◽  
Dry Density ◽  
Sem Images ◽  
Air Content ◽  
Compressive Strength Of Concrete ◽  
Imagej Software

In this study, coconut shell aggregate (CSA) was used in brick aggregate concrete (BAC) to produce structural lightweight concrete. Various BACs containing CSA (CSBACs) were prepared based on the volumetric mix ratio of 1:1.5:3 (cement:fine aggregate:coarse aggregate). CSA was used substituting 0−15% of brick aggregate (BA) by weight. The concrete mixes were designed based on the weight-based water to cement (w/c) ratios of 0.45, 0.50, and 0.55. All the freshly mixed concretes were tested for their workability with respect to slump. In addition, the freshly mixed concretes made with the w/c ratio of 0.50 were examined for their wet density and air content. The hardened concretes were tested for their dry density, compressive strength, and microstructural characteristics (e.g., microcrack, micropore, fissure). The microstructure of CSBACs was investigated by a scanning electron microscope (SEM). In addition, the fissure width between the cement paste and CSA was measured from the SEM images using “ImageJ” software. The correlation between the compressive strength and fissure width of CSBAC was also examined. Test results showed that the air content of CSBACs including 5–15% CSA was higher than that of the control concrete (0% CSA). In addition, the density and compressive strength of concrete decreased with the increased CSA content. Above all, the most interesting finding of this study was the presence of fissures in the interfacial transition zone between the cement paste and CSA of CSBAC. The fissure width gradually increased with the increase in CSA content and thus decreased the compressive strength of concrete. However, the fissure width decreased with the increased curing age of concrete and therefore the compressive strength of CSBAC was enhanced at later ages. Moreover, a good correlation between the compressive strength and fissure width of CSBAC was observed in this study.

Effect of the Combination of Calcined Shale and Pozzolanic Materials on Compressive Strength of Concrete

2013 ◽  
Vol 723 ◽  
pp. 298-302
Author(s):  
An Cheng ◽  
Wei Ting Lin ◽  
Sao Jeng Chao ◽  
Hui Mi Hsu ◽  
Chin Cheng Huang
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Water Demand ◽  
Test Results ◽  
Calcination Temperatures ◽  
Heat Treated ◽  
Compressive Strength Of Concrete ◽  
Pozzolanic Materials

This study investigated the influence of individual constituents of calcined shale or hybrid constituents of calcined shale and fly ash or silica fume on the workability and compressive strength. Calcined shale is heat treated in a kiln and then ground to a finer powder and the calcination temperatures of 800 °C were used. The test results demonstrated that the workability and compressive strength decreased with the inclusion of calcined shale increased and the compressive strength of the specimens containing calcined shale all lower than that of the control specimens. It might be due to the higher water demand and lower CaO value. However, the hybrid batches with calcined shale and fly ash or silica fume enhanced better performance on compressive strength than individual constituents of calcined shale. The combination of 10 % calcined shale and 10 % silica fume in concrete seemed to give superior compressive strength and gave the highest value in the testing series. Finally, the inclusion of calcined shale is help to reduce the emissions of CO2and revealed an ecological advantage for concrete containing a binder blend of cement and calcined shale.

The Interfacial Transition Zone: “Direct” Evidence on Compressive Response

1994 ◽  
Vol 370 ◽  
Author(s):  
David Darwin
Keyword(s):  
Compressive Strength ◽  
Transition Zone ◽  
Cement Paste ◽  
Direct Evidence ◽  
Indirect Evidence ◽  
Interfacial Strength ◽  
Interfacial Transition Zone ◽  
Compressive Response ◽  
Heterogeneous Nature ◽  
Compressive Strength Of Concrete

AbstractThere is little question that the strength of the interfacial transition zone (MTZ) between cement paste and aggregate affects the compressive strength of concrete. The key question, rather, is to what degree? It is difficult to directly measure the response of the overall composite to changes in interfacial properties, since it is difficult to isolate interfacial strength as the only variable.Research on the effects of interfacial strength on the compressive response of concrete that comes the closest to providing direct evidence is summarized. The studies, dating to the 1950's, include both experimental and analytical efforts aimed at isolating the effects of the ITZ, as well as experimental efforts that are considered to provide strong indirect evidence. The research shows that the ITZ plays a measurable role in the response of concrete to compressive stress, but that its role is overshadowed by the properties of the cement paste and aggregate constituents of concrete and the heterogeneous nature of the composite.

scholarly journals COMPORTAMENTO DO CONCRETO MEDIANTE A ADIÇÃO DE POZOLANA ARTIFICIAL

e-xacta ◽  
2013 ◽  
Vol 6 (1) ◽  
pp. 55
Author(s):  
Nathália Maria Assi Rabelo ◽  
Christianne Rodrigues Garcia
Keyword(s):  
Air Pollution ◽  
Compressive Strength ◽  
High Performance ◽  
Laboratory Tests ◽  
High Performance Concrete ◽  
Cement Ratio ◽  
Compressive Strength Of Concrete ◽  
Reduce Energy Consumption ◽  
Para Determinar ◽  
Mineral Waste

<p align="justify">A utilização de resíduos minerais vem sendo empregada na indústria do concreto, trazendo vantagens em âmbitos técnicos, econômicos e ambientais. Ao substituir o cimento por esses resíduos, há a redução do consumo de energia e poluição do ar, gerados por sua produção e, ainda, contribui na busca por concretos de alto desempenho. Nesse contexto, o presente trabalho teve como objetivo adicionar pozolana artificial ao concreto e determinar a resistência à compressão, assim como a sua trabalhabilidade, além de estabelecer um comparativo entre o concreto adicionado de pozolana artificial e o concreto sem adição, contendo somente o cimento Portland. Através de ensaios laboratoriais, observou-se que a pozolana, devido a características específicas, não apresentou resultados favoráveis. Em sua adição ao concreto, observou-se que a quantidade de água necessária para a realização dos ensaios foi maior, alterando assim a relação água/cimento, sendo consequentemente necessário um aumento da quantidade de cimento. Observou-se, também, que houve uma queda na resistência à compressão do concreto, devido à presença da pozolana. Verificou-se que o material estudado necessita de modificações em suas propriedades para a sua utilização como insumo do concreto, portanto novas pesquisas, com um maior número de ensaios, foram sugeridas para determinar a sua viabilidade.</p><p align="justify">Abstract</p><p align="justify">Mineral waste has been used in the concrete industry, bringing advantages in technical fields, economic and environmental. By replacing the cement by these residues eventually reduce energy consumption and air pollution generated by their production and also help in the search for high performance concrete. In this context, the present study aimed to add artificial pozzolan to concrete and to determine the compressive strength, as well as its workability, and establish a comparison between the concrete and artificial pozzolan added without adding concrete containing only Portland cement. Through laboratory tests, it was observed that the pozzolan, due to specific features, showed no favorable results. In its addition in concrete, it was observed that the amount of water required for the tests was greater, thus altering the water / cement ratio, and is therefore required an increased amount of cement. It was also observed that there was a decrease in the compressive strength of concrete due to the presence of pozzolan. It was found that the studied material requires changes in its properties for use as an input of the concrete, thus further research, with a greater number of tests have been suggested to determine their viability.</p>

scholarly journals KUALITAS BATA BETON BERLUBANG DENGAN BAHAN LIMBAH TAILING PENAMBANGAN EMAS UPBE PONGKOR

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Amalia Amalia ◽  
Agus Murdiyoto
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Bulk Density ◽  
Gold Mining ◽  
Partition Wall ◽  
Weight Content ◽  
Concrete Blocks ◽  
Hollow Brick ◽  
Compressive Strength Of Concrete ◽  
Class Iv

ABSTRACTThis study aims to investigate the potential of gold mining tailings UPBE Pongkor as hollow concrete brick making material and investigate its properties. The study was conducted by making hollow concrete brick composition 1 PC: 8 aggregate, consisting of 4 variations of tailings as aggregate substitution, ie 0%, 25%, 50%, and 75% of the aggregate weight. The results showed that (1) the use of tailings as aggregate replacement in concrete hollow brick can reduce the compressive strength of concrete blocks, (2) can be used as a substitute Tailings aggregate up to 75%, wherein the composition produces hollow concrete bricks that still meets ISO standards for class IV concrete brick that can be used as non-structural partition wall, (3) the higher levels replace sand tailings, water absorption in hollow concrete brick is also higher, (4) weight content of concrete hollow brick using more and more tailings, bulk density is decreased.Key words : Hollow concrete brick, compressive strength, tailing of gold mining

Effect of Pakistani bentonite on properties of mortar and concrete

Clay Minerals ◽  
2011 ◽  
Vol 46 (1) ◽  
pp. 85-92 ◽  
Author(s):  
S. Ahmad ◽  
S. A. Barbhuiya ◽  
A. Elahi ◽  
J. Iqbal
Keyword(s):  
Experimental Investigation ◽  
Compressive Strength ◽  
Water Demand ◽  
Activity Index ◽  
Low Cost ◽  
Test Results ◽  
Sulphate Attack ◽  
Substitution Level ◽  
Wide Range ◽  
Compressive Strength Of Concrete

AbstractBentonite is composed primarily of montmorillonite and is useful in a wide range of applications. This paper presents the results of an experimental investigation carried out to evaluate the possibility of using a Pakistani bentonite (from Jehangira, Swabi District) as a cement replacement material in mortar and concrete. The cement in mortar and concrete was replaced with the bentonite at 0%, 20%, 30%, 40% and 50% by cement mass. The strength activity index of bentonite was determined ‘as received’ (20ºC) and ‘heated’ (treatment at 500ºC and 900ºC). The test results indicated that the strength activity index of bentonite conformed to the ASTM Standard C618 specifications, except for the ‘900ºC heated’ bentonite. The water absorption decreased for mortar containing up to 30% bentonite and then steadily increased at higher bentonite loadings. When immersed in 5% Na2SO4 and 2% MgSO4 solution, the greatest compressive strength was observed for mortar containing 30% bentonite. The water demand of concrete increased with increasing bentonite content. Although the compressive strength of concrete decreased progressively as the substitution level of bentonite was increased, the compressive strength of concrete containing 30% ‘as received’ bentonite was found to be 70% of the control concrete, whereas for concrete containing 30% ‘500ºC heated’ bentonite, the strength was found to be 79% of the control concrete. It can be concluded that this Pakistani bentonite can be used to replace up to 30% of cement to produce concrete with sufficient compressive strength for low-cost construction resistant to sulphate attack.

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