Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : silica fume


Effect of Starch Powder on Behavior of Silica Fume Biopolymer Concrete

Samir M. Atia; Waleed A. Abbas

Engineering and Technology Journal, 2021, Volume 39, Issue 12, Pages 1797-1805
DOI: 10.30684/etj.v39i12.2103

The great economic development and the growth of modern means of construction have led to the spread of large quantities of chemical admixtures that we must be cautious of. As the world is turning towards environmentally friendly alternatives, finding locally viable solutions is becoming inevitable. The influence of using Nano starches of a biopolymer on certain properties of silica fume concrete in the fresh case (slump and fresh density) and in the hardened case (compressive strength, splitting tensile strength, and flexural strength) has been investigated. It has been added to silica fume concrete in various percentages of (0%, 0.25%, 0.5%, and 0.75%) by cement weight. The mix proportions of concrete mixtures were 1:2.3:2.3, with a fixed w/c of 0.47 and 15 % silica fume added by the weight of cement for all mixers. super plasticizer of 0.75% is also added by the weight of cement for all mixtures. According to the findings, slump increased by 19%, and fresh density increased by 3% when Nano starch was added at a concentration of 0.75%. The optimal level of Nano starch addition was 0.25%, which resulted in a 43% increase in compressive strength and a 34% and 26% increase in splitting tensile and flexural strength of concrete, respectively.

Mitigation of the Factors Affecting the Autogenous Shrinkage of Ultra-High Performance Concrete

Adil M. Jabbar; Mohammed J. Hamood; Dhiyaa H. Mohammed

Engineering and Technology Journal, 2021, Volume 39, Issue 12, Pages 1860-1868
DOI: 10.30684/etj.v39i12.2155

Ultra-High Performance Concrete (UHPC) is a new generation of concrete characterized by its high strength, high durability, and high stiffness. Autogenously shrinkage represents one of the issues of UHPC that occurred at early ages. It occurs particularly during the first 48 hours after casting. This paper focuses on the ways that can be depended on to mitigate the autogenously shrinkage and obtain the outstanding mechanical properties of UHPC. The results showed that the use of coarse sand and high dose of high range water reduced the admixture above 5% of cementations of materials weight, and high ambient temperature at the time of mixing and casting led to increasing the autogenously shrinkage. While using fine sand, silica fume at 25% of cement weight, and crushed ice at 50% of mixing water to control the mixing temperature can reduce autogenously shrinkage significantly.

Sand Column Stabilized by Silica Fume Embedded in Soft Soil

Hussein H. Karim; Zeena W. Samueel; Mohammed S. Mohammed

Engineering and Technology Journal, 2016, Volume 34, Issue 6, Pages 1047-1057

This research aims to study the behavior of the sand columns stabilized with silica fume (as an additive with different percentages) and driven in soft soil bed with undrained shear strength (cu) between 16 – 21 kPa. Holesin the shape of columns with diameter 50 mm and length 300 mm have been drilled in a soil bed and backfilled with sand mixed with several proportions of silica fume with 7-days curing. A rigid circular footing with diameter 64.6 mm was located on each column and loaded axially till failure. The results analysis of the model tests indicated an encouraging improvement in load carrying capacity of the columns and considerable reduction in the settlement compared to the conventional stone columns. The bearing improvement ratio and settlement reduction ratio exhibited by the sand columns are 1.18 and 0.71, respectively. The best possible addition of silica fume content in sand–silica fume columns is 7% giving bearing improvement ratio and settlement reduction ratio of 1.56 and 0.5 respectively.

Geotechnical Properties of Expansive Soil Treated With Silica Fume

Zeena Waleed S. Abbawi

Engineering and Technology Journal, 2013, Volume 31, Issue 17, Pages 3358-3370

Problematic soils such as expansive soil are those clay soils which exhibited
significant volume changes as results of soil moisture variation, when a dry mass of
clay is allowed to absorb water, the effective size of particles increases and therefore
the clay mass swells. This type of soil, upon wetting and drying, causes sever damage
to structures built on such soil.
A treatment of swelling/shrinkage using silica fume was studied in this work. The
soil selected for the present investigation classified as (CH) according to unified soil
classification system with liquid limit = 51% and plastic limit = 27%. Soil specimens
were mixed with various percentages of silica fume contents (10%, 20%, 25%, 30%
and 50%) to determine their effects on geotechnical properties such as Atterberge’s
limits, compaction, unconfined compression and swelling properties.
The results show that the silica fume played an important role in improving the
problem of swelling behavior in expansive soil. The silica fume decrease liquid limit
and changed compaction parameters of expansive soils the moisture content values
increased and the maximum dry unit weight values decrease. Also the silica fume
increased unconfined compressive strength, decreased the compressibility and the
vertical swelling percentages of clayey soil-silica fume mixtures.

Mechanical Properties of Reactive Powder Concrete (RPC) with Various Steel Fiber and Silica Fume Contents

Lubna S. Danha; Wasan Ismail Khalil; Hisham M. Al-Hassani

Engineering and Technology Journal, 2013, Volume 31, Issue 16, Pages 3090-3108

An experimental work was carried out to investigate some mechanical properties
of Reactive Powder Concrete (RPC) which are particularly required as input data for
structural design. These properties include compressive strength, tensile strength
(direct, splitting and flexural), flexural toughness, load-deflection capacity and static
modulus of elasticity. The effects of three variable parameters on these properties were
carefully studied which are, the silica fume content SF (0%, 10%, 15%, 20%, 25%, and
30%) as a partial replacement by weight of cement, hooked macro steel fibers volume
fraction Vf (0%, 1%, 2% and 3%) and superplasticizertype(Sikament®-163N and
PC200).The diameter of the steel fiber is 0.5mm and its length is 30mm with aspect
ratio 60.The experimental results showed that as the silica fume content (SF) increases
from 0% to 30% the compressive strength significantly increases, while the increase in
tensile strength is relatively lower. The inclusion of steel fibers leads to a considerable
increase intensile strength, while the addition of steel fibers causes a slight increase in
compressive strength of RPC as fiber volume fraction increases from 0% to 3%.The
increase in the steel fibers volume fraction and silica fume content improved the loaddeflection
behavior and consequently gave higher ductility and fracture toughness of
RPC.

High Performance of Silica Fume Mortars for Ferrocement Applications

M. A. Mashrei; Gh. M. Kamil; H. M. Oleiwi

Engineering and Technology Journal, 2013, Volume 31, Issue 13, Pages 2477-2488

The current study deals with obtaining the high performance mortars to use in the
applications of ferrocement. The main problem that has greatly affected the
performance of mortar is the workability. A low water-cement ratio mostly resulted in
increases in the compressive strength and led to the enhancement of durability
characteristics, but decreases in the workability.
Workability becomes an important factors, as the mortar has to easily penetrate
between the layers of the mesh wires. A reasonably workable with high strength
cement mortar can be obtained by using a high cement content coupled with the use
of silica fume and superplasticizers. In this investigation a series of compression tests
were conducted on 50 mm cube and 150 ×300 mm, cylindrical specimens to obtain
the compressive strength and the stress-strain behavior of mortar with silica fume and
superplasticizers and flexural tests were conducted on 50 ×5 0 × 200 mm prism to
obtain the modulus of rupture. The results of this study indicated that the variation in
mortar strength depend on the water-to-binder ratio of the mix and percentages of
cement replacing. The effects of these parameters on the stress-strain curves are
presented. The best replacement percentage of silica is 3% was concluded in this
study. From the experimental results a mathematical model has been developed to
predict the 28-day compressive strength of silica fume mortar with different water-tocementitious
ratios and superplasticizers percentage

Studying some of the Geotechnical Properties of Stabilized Iraqi Clayey Soils

Ishraq Khudhair Abass

Engineering and Technology Journal, 2013, Volume 31, Issue 6, Pages 1117-1130

In many road construction projects, if weak soils exist, stabilization and improvement of their properties is necessary. The stabilization process aims at increasing the soil strength and reducing its permeability and compressibility. An experimental program was undertaken to study the effect of engineering properties of kaolin clayey soils ((the kaolin was supplied by the General Company of Geological Survey and Mining which originally obtains from Al-Dewiekhla near Aukashat district in the west of Iraq)) when blended with lime (L) and Silica Fume (SF). A series of laboratory experiments have been implemented for varieties of samples: 2.5%, 5.0%, 7.5% and 10.0% for (Lime) and 2.0%, 4.0% and 6.0% for(Silica Fume). These experiments are: consistency limits test, specific gravity test, compaction test, unconfined compression test and California bearing ratio test. For each test, the optimal quantity of Lime (L) and the optimal percentage of Lime Silica Fume (LSF) combination were determined. The results revealed that: the optimal percentage of LSF combination was attained at a (2.5%L+6.0%SF), which served as control in this study. This optimal percentage: decrease the liquid limit, plasticity index, specific gravity and maximum dry density; and raise the optimum moisture content, unconfined compressive strength and California bearing ratio. These results showed also, that the combination of LSF stabilization at (2.5% L+6.0% SF) is better than the optimal one which achieved by Lime alone: 2.5%L for plasticity index, 10.0%L for specific gravity, maximum dry density and optimum moisture content, 5.0%L for unconfined compression stress and 7.5%forCaliforniabearingratio. All of these results indicated that the engineering properties of clayey soils can be enhanced, by blending Lime and Silica Fume together.

Experimental Investigation of Shear- Critical Reactive Powder Concrete Beams without Web Reinforcement

Kaiss F. Sarsam; Ihsan A.S. Al-Shaarbaf; Maha M. S. Ridha

Engineering and Technology Journal, 2012, Volume 30, Issue 17, Pages 2999-3022

جرت عملیة استقصاء عملي على سلوك عتبات خرسانیة عالیة المقاومة مصنوعة من
المساحیق الفعالة. خمسة عشرة عتبة تحوي حدید تسلیح طولي تم صبھا وخالیة من تسلیح القص.
المتغیرات الرئیسیة التي تم دراستھا ھي محتوى الالیاف الفولاذیة, نسبة حدید التسلیح الطولي,
نسبة فضاء القص الى العمق الفعال ومحتوى السلیكا الفعالة. اعلى قیمھ لمقاومة الانضغاط كانت
110 میكاباسكال باستعمال نوع واحد من الالیاف الفولاذیة. تم اقتراح علاقات للتنبؤ بمقاومة اجھاد
القص لعتبات خرسانة المساحیق الفعالة الخالیة من تسلیح القص. العلاقات االمقترحة اظھرت
تطابقا جیدا لمقاومة اجھاد القص بالمقارنة مع النتائج العملیة.

The Effect of Addition of Carbon Fibers on Some Properties of Self Compacting Concrete

Engineering and Technology Journal, 2011, Volume 29, Issue 14, Pages 576-596

To Study the possibility of producing self compacting concrete (SCC), 10% by weight of cement of metakaoline and silica fume were used and carbon fiber with two volume fraction (0.1%, 0.5%) and two fiber lengths (6mm, 12mm) were add . the effect of these variables on most properties of SCC containing fibers has been studied.
Test results show that concrete mixes containing metakaoline and silica fume required higher superplastizer content to 9% and 10% by weight of cement compared with 8% by weight of cement for mixes without Pozzolanic materials to maintain the self compatibility of mixes .
A significant improvement was observed in the mechanical properties of mixes including compressive and splitting tensile strength, Moduls of rupture, static Modulus of elastisity, and impact resistance. the improvment percentage at 28 days were (6.74% , 5.37% , 4.5% , 3.2% , 6.07%) respectively for SCC with silica fume mixes and (8.43% , 7.6% , 6.08% , 4.03% , 30.30%) respectively for SCC with High
reactive metakaolin mixes. Test results indicate that the addition of carbon fibers led to reduce the workability of mixes and the reduction was increased with fiber length and fiber content. mixes
reinforced with carbon fibers, the compressive and splitting tensile strength, modulus of rupture, static moduls of elastisity, and impact resistance at failure were higher than the reference mixes by not more than (25.75% , 66.18%, 38.26% , 14.14% and 1195%) respectively .

Predicting Mechanical Properties of High Performance Concrete by Using Non-destructive Tests

Sura F. Al-Khafaji; Waleed A. Al-Qaisi; Shakir A. Al-Mishhadani

Engineering and Technology Journal, 2009, Volume 27, Issue 3, Pages 425-444

In this study, high performance concrete mixes were produced by using high
range water reducing agent and also by using 10% silica fume or 10% high
reactivity metakaolin as a partial replacement by weight of cement. Three cement
contents (350, 450, and 550) kg/m3 were used through this study. A total of 330
(100 mm) cubes, 132 (100×200 mm) cylinders, 132 (100×100×400 mm) prisms,
and 66 (150×300 mm) cylinders were casted and cured to the required age of test .
All specimens were cured in tap water except 165 cubes, which were submerged in
Cl ˉ + SO4ˉ ˉ solution at concentration identical to those present in severe
aggressive environment to study the effect of this solution on the compressive
strength of high performance concrete mixes. Compressive strength, splitting
tensile strength, modulus of rupture, static modulus, rebound number, ultrasonic
pulse velocity, dynamic modulus, initial surface absorption, density ,and total
absorption tests were investigated for all mixes at 7, 28, 90, and 120 days age.
Results of the destructive tests (compressive tensile strength, strength, splitting
modulus of rupture, and static modulus) and non–destructive tests (hammer,
ultrasonic pulse velocity, and dynamic modulus) are statistically analyzed by using
SPSS Ver.15 software to study the possibility of predicting the mechanical
properties of high performance concrete by using non–destructive tests. Simple and
multiple linear regression analysis of the obtained results leads to the proposed
statistical models for evaluating the compressive strength, splitting tensile
strength, modulus of rupture, and static modulus by using one or two or three of
the above mentioned non–destructive tests. Analysis of variance (ANOVA)
and t–test was also used to investigate the adequacy of the statistical models.