Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : silica fume

Performance of Self-Compacting Concrete Containing Pozzolanic Materials in Aggressive Environment

L.A. Zghair; Q.J. Frayyeh; M.M. Salman

Engineering and Technology Journal, 2017, Volume 35, Issue 5, Pages 439-444

The aims of this study is to investigate the resistance of different SCC mixtures to aggressive solutions. The investigation included the type of the cementitious materials (silica fume and high reactivity Attapulguite-HRA) and limestone powder (chalk powder and Al-gubra). The powder content of the mixes was kept constant, 500 kg/m3. The slump flow, L-box, and V-funnel were performed for mixes in there fresh state. In the present work, the specimens were immersed in sulfuric acid solution with a concentration of 0. 5% up to 289 days after normal curing for 28 days. After concrete has hardened, two types of test are performed. Firstly, destructive tests are conducted including (compressive strength, splitting tensile strength, and modulus of rupture). Secondly, a mass loss as non-destructive test is performed. The results obtained from this work, show that concrete mixes with chalk powder only, had the best resistance to sulfuric acid solution comparable with concrete made with Pozzolanic materials the reduction in compressive strength was 25. 9 %. In addition, concrete mixes with HRA had the worst resistance.

Mechanical Properties of High Strength Concrete Containing Different Cementitious Materials

Hisham K. Ahmed; Oday A. Abd

Engineering and Technology Journal, 2016, Volume 34, Issue 1, Pages 96-110

High strength concrete hasstrength significantly beyond what is used in normal practice. According to American Concrete Institute (ACI), high strength concrete revised the definition to cover mixtures with specified design strength of 55 MPa or more.
The main objective of this investigation isto study the effect of using different supplementary cementitious materials in binary blends on mechanical properties of high strength concrete.
The experimental work includes threestages: firstly, preparation of cementitious materials (metakaolin and pumice) from local materials,second involves conducting several trial mixes to choose the best of superplasticizer that satisfies the required properties and to specify the optimum water content which is designed in laboratory by 0.3 W/Cm ratio, to achieve workability with (60-80mm) slump and the best compressive strength which was 64.6 at 28 days.
Thirdly carrying out tests to find out the compressive strength, splitting tensile strength, modulus of rupture, on binary concretes including mixes containing silica fume as cement replacement at percentages of 8%, 10% and 15%, mixes containing metakaolin as cement replacement levels of 10%, 15%, and20% and mixes containing pumice at cement replacement of 10%, 15%, and 20%.These properieswere measured at ages ranging from7days to 180 days.
The resultsindicate that the silica fume performs better than other supplementary cementitious materials(metakaolin or pumice) in terms of the compressive strength, splitting tensile strength and modulus of rupture development at ages of 7,28,60,90and180 days where the average percentage of increase when using 8%,10% and 15% ofsilica fume was about(19%,23% and 18.7%) ,respectively, while when using 10%,15% and 20%metakaolin the average percentage of increase was (10%,12.6% and 4%) respectively, also when using 10%,15% and 20% of pumice the average percentage of increase was (2.6%, 6% and 1.5%), respectively.

Combined Effect of Silica Fume and Steel Fiber on Modulus of Elasticity of High Performance Concrete

Muntadher J. Taher; Maan S. Hassan; Zeyad M. Al-azawi

Engineering and Technology Journal, 2015, Volume 33, Issue 4, Pages 868-876

Concrete elastic modulus is a basic property required for the appropriatepredicting of its basic behavior and for its correct implementation in a variety ofconstructional and engineering applications. This study presents an experimental and analytical evaluation of elastic modulus of high performance concretes (HPC) produced bysteel fiber and silica fume. The aim of this study is to develop the elastic modulus propertyof HPC and to show the applicability of ACI models to predict the elastic modulus of HPC from compressive strength. Four volume fractions of steel fiber with an aspect ratio (fiber length/ fiber diameter) of 60 were used (0, 0.5, 1.0, and 2.0 %). Incorporations of silica fume into the concrete were 0% and 15% by weight as a cement replacement. Water/cement ratio was ranged (0.28-0.4) with different amount of superplasticizer, and the reference slump was 170 mm. Both compressive and elastic modulus tests were made on hardened concretes reinforced with steel fibers and then compared with control specimens at 14 and 28 days. The results showed that the presence of silica fume enhanced the compressive strength and modulus of elasticity of evaluated concretes. In addition, adding steel fiber slightly increased both strength and modulus of elasticity values. Also, results showed that the elastic modulus of HPC is relative to the compressive strength, the ACI 318 expression is predicting elastic modulus of HPC and HPC-SF superior than ACI 363, but ACI 363 equation seems to be better in prediction modulus of elasticity of HPC-SF0.5S, HPC-F1.0S, and HPC-SF2.0S in comparison with ACI 318.

Effect of External Sulfate Attack on Self Compacted Concrete

Zena K. Abbas Al-Anbori

Engineering and Technology Journal, 2013, Volume 31, Issue 6, Pages 1092-1106

Self-compacting concrete (SCC) is an innovative concrete that does not require vibration for placing and compaction. It is able to flow under its own weight, completely filling formwork and achieving full compaction, even in the presence of congested reinforcement. The effect of external sulfate attack was studied-Es (very sever exposure SO4>10000ppm) according to ACI 318-11.
The mix design method of SCC used is according to EFNARC 2002, and then must satisfy the criteria of filling ability, passing ability and segregation resistance. The experimental program focuses to study two different chemical composition of sulfate resistance Portland cement with different percentage of silica fume replacement by weight of cement and W/cm (0.3 and 0.35). The SCC mixes with cement type 1(C3S= 46.39 and C3S/C2S = 1.78) shows more resistance to Es than mixes with cement type 2 (C3S= 61.22 and C3S/C2S =4.44). The SCC mixes containing 10% SF as replacement of cement shows more resistance to external sulfate attack. The percentage of increase is 17.95% for SCC mixes with type 1 cement and W/cm =0.3 and 17.88% for SCC mixes with type 2 cement and W/cm =0.3 compared to reference concrete mixes

Improving the Compatibility between Polymer-, Pozzolanic Cement-Based Repairing Materials and Concrete Substrate

Qais J. Frayyeh; Maan S. Hassan; Tahseen D. Saadoon

Engineering and Technology Journal, 2013, Volume 31, Issue 4, Pages 661-676

In this study, the compatibility of five different cement based repair materials and substrate concrete was investigated in three stages. First stage includes studying the individual properties of repair materials, and also two types of concrete, such as compressive strength, flexural strength, and dry shrinkage using BS 1881: part 116, ASTM C78-06, ASTM C157 -06 test procedure respectively. Second stage includes evaluating the bond strength of composite cylinder for different combinations of repair materials and substrate concrete. Third stage includes investigating the compatibility using a composite beam of repair material and substrate concrete under third point loading.
The experimental results show that one individual property has no crucial effect on the success of concrete repair system. Bond strength and dry shrinkage however has a strong indication about the compatibility.