Effect of GGBS and fly ash on mechanical strengthof self-compacting concrete containing glass fibers

In this article, attempt has been made to improve the performance of self compacting concrete using recycled coarse aggregate with adding of fly ash and glass fiber. Self compacting concrete has significant environmental advantages in compaction to the vibrated concrete. Absence of noise and vibrations during installing provides healthier working environment. In general, there is a scarcity of coarse aggregate throughout the world. Consumption of large amount of coarse aggregate affects the environment. For the purpose of reducing the consumption of coarse aggregate, a need for an alternative coarse aggregate arises. Recycled coarse aggregates are obtained from the demolition of buildings, culverts and also by-products from the industries. Hence, partial replacement of coarse aggregate by recycled aggregate is researched in this article, in view of consuming the ecological balance. SCC can also be used in situation where it is difficult or impossible to use mechanical compaction for fresh concrete, such as underwater concreting, cast in-situ pile foundations, machine bases and columns or wall with congested reinforcement. The self compacting concrete must meet the filling ability and passing ability with uniform composition throughout the process of transport and placing. Hence, Self compacting concrete demands large amount of powder (cementitious and pozzolanic materials) content and fines for its cohesiveness and ability to flow without bleeding and segregation. In this investigation, part of the cementitious material is replaced with pozzolanic material fly ash, and the properties of self compacting concrete in fresh and hardened states were studied. The increase of the percentage of the fly ash influences the bleeding and segregation in SCC. Hence, the addition of glass fibres can improve ductility, post crack resistance, energy absorption capacity and bleeding resistance. Taking these advantages into account a study was done. The various properties of the materials to be used in the experimental programme were determined. The specification of glass fibers and the advantages of using them along with concrete were studied. A detailed review of literature on glass fiber reinforced concrete was also done. The fresh and hardened properties of Self Compacting Concrete (SCC) using recycled coarse aggregate, fly ash with glass fibers were evaluated. The SCC mixtures are prepared with 40% of fly ash, 40% of recycled coarse aggregate and adding of 0.03% glass fiber. The strength test namely, Compressive Strength Test, Split Tensile Strength Test and Flexural Strength Test are carried out in this investigation. To test the characteristics of self compacting concrete, Slump cone test, J-ring test, L-box test were conducted to test the characteristic of self compacting concrete.

SCC (Self compacting concrete) can fill formwork and encloses reinforcing bars under gravity and maintains homogeneity without vibration. SCC shortens the period of construction, guarantees compaction in confined zones, moreover terminates noise due to vibration. The wide spread application of SCC is restricted because of the high cost for the production of SCC with high cement content and chemical admixtures. In order to make the production of SCC economical, and to reduce the high cement content the Ordinary Portland Cement in SCC can be blended with pozzolanic materials like rice husk ash and supplementary cementitious materials like fly ash. In this paper the fresh state properties and mechanical properties such as compressive strength, split tensile strength and flexural strength of SCC with ternary blends of rice husk ash (RHA) and fly ash (FA) were studied. For this purpose, different mixes were prepared by replacing Ordinary Portland Cement (OPC) with 5%, 10%, 15% and 20% of rice husk ash (RHA) and the percentage of addition of fly ash (FA) is fixed as 15% for all these mixes. It was observed that the specimen incorporating 10% of rice husk ash (RHA) and 15% of fly ash (FA) as ternary blend exhibits better mechanical properties such as: Compressive, split tensile and flexural strengths at 28 days of age as compared to traditional mix of SCC without RHA (Rice Husk Ash) and FA (Fly Ash). This research demonstrates that the ideal percentage for a mixture of rice husk ash (RHA) and fly ash as ternary blend is 10% and 15% respectively.

Palm fuel ash (POFA) and rice husk ash (RHA) are usually disposed to open areas and landfills without treatment, resulting in environmental problems. Both materials fulfilled the criteria as pozzolanic material, thus can be used as substitutes to cement. This paper presents the comparison in the fresh and hardened properties between self-compacting concrete (SCC) containing POFA and RHA. The SCC mixtures were produced based on water/binder ratio of 0.6. Both POFA and RHA were introduced in concrete replacing 0%, 10%, 20% and 30% of cement by weight. The fresh SCC was tested for three (3) fresh properties including filling ability, passing ability and segregation resistance. Meanwhile, the hardened properties of concrete were tested for its compressive strength. The fresh properties of SCC incorporating POFA and RHA fulfilled all the requirements of SCC which include the filling ability, passing ability and segregation resistance. Meanwhile, SCC containing RHA had higher compressive strength than the SCC containing POFA for all different replacement level. This is because RHA had higher SiO2 content than POFA, thus promote more pozzolanic reaction to improve the strength of concrete. Furthermore, the optimum replacement level of POFA and RHA in SCC are 10% and 20%, respectively. However, the compressive strength of both SCC containing POFA and RHA were still lower than the control SCC. It is suggested that the SCC containing POFA and RHA to be cured for longer period to achieve better or equivalent strength to the control SCC.

Use of Unprocessed Rice Husk Ash and Pulverized Fuel Ash in the Production of Self-compacting Concrete

Self-compacting concrete (SCC) is an extremely flowable, non-segregating concrete that fills every corner of formwork evenly and completely by its own mass and encapsulates reinforcement without vibrating, all while retaining homogeneity. SSC’s mechanical efficiency can be enhanced by using byproducts or waste materials as cement replacements. Rice husk ash (RHA) & fly ash stay very reactive byproducts. Because of its high silica content, Fly ash and RHA have strong pozzolanic properties, used as complementary cementations material in SSC. The automatic properties and Self-compacting concrete has a high acid resistance determined. Mainly the cement is replace by fly ash & rice husk ash with three different percentages variations (10%, 20%, and 30%). In each percentage of replacement, the fly ash and RHA has equal percentages. For example, in 10% of replacement 5% of fly ash and 5% of RHA is replaced. In frequently fly ash is industrial by-product and having the pozzolanic properties. And the RHA (rice husk ash) is also a pozzolanic reactive material. Compared to the adhesive, fly ash & RHA has more silica ingredient. The self-compacting concrete was calculated for M30, and specimens are cast. Compressive strength and split tensile strength, flexural strength, and durability (acid resistance) tests are performed for 7 days, 14 days, and 28 days.

In this study, an artificial neural networks study was carried out to predict the core compressive strength of self-compacting concrete (SCC) mixtures with mineral additives. This study is based on the determination of the variation of core compressive strength, water absorption and unit weight in curtain wall elements. One conventional concrete (vibrated concrete) and six different self-compacting concrete (SCC) mixtures with mineral additives were prepared. SCC mixtures were produced as control concrete (without mineral additives), moreover fly ash and limestone powder were used with two different replacement ratios (15% and 30%) of cement and marble powder was used with 15% replacement ratio of cement. SCC mixtures were compared to conventional concrete according to the variation of compressive strength, water absorption and unit weight. It can be seen from this study, self-compacting concretes consolidated by its own weight homogeneously in the narrow reinforcement construction elements. Experimental results were also obtained by building models according to artificial neural network (ANN) to predict the core compressive strength. ANN model is constructed, trained and tested using these data. The results showed that ANN can be an alternative approach for the predicting the core compressive strength of self-compacting concrete (SCC) mixtures with mineral additives.

A comprehensive review of partial replacement of cement in concrete

Self-compacting concretes (SCCs) are considered promising materials in the civil engineering field. Their main characteristic is the ability to compact only through gravitational force. Mineral additions such as rice husk ash (RHA) and fly ash (FA) are recommended to be used in SCCs during their mix designing, in order to increase fluidity and mechanical strength. These materials are also considered wastes from industry, without a certain destination, which contributes to environmental pollution. In this study, four mixtures of SCC were tested using RHA and FA with two different types of Portland cement, CEM CP IV and white CEM. For the fresh state tests, all of the SCCs mixtures showed satisfactory results. The SCCs with white CEM showed higher mechanical strength at 7 days than CEM CP IV. Analyzing the mineral additions, their use improved the mechanical strength of SCCs at 28 days, there is also observed a higher pozzolanic effect to RHA.

In this study, the age-dependent splitting and flexural tensile strength have been investigated by incorporating the various percentages of fly ash in the plain concrete mixes. The partial replacement of cement by fly ash was varied from 0 to 60% on an equal weight basis. Standard concrete specimens were cast for measuring splitting and flexural tensile strength at different ages, i.e., 7, 28, 56, 90, 150, and 180 days, for all plain and fly ash concrete mixes. Experimental results show that the fly ash produced a significant effect on the tensile strength of concrete mixes. It has been observed that the fly ash concrete mixes gain considerable tensile strength with respect to age beyond 28 days. In the low-calcium fly ash concrete mixes, the rate of development of tensile strength from 28 to 180 was observed higher in comparison with the plain concrete mixes. The assessment of the existing models for the estimation of age-dependent tensile strength recommended by design codes and researchers with experiments has also been done on various mixes of plain and fly ash concrete. New models to predict the age-dependent splitting and flexural tensile strength of concrete having different percentages of fly ash are proposed. The present experimental and analytical study will be helpful for the designers and practicing engineers for fixing preliminary dimensions of reinforced and prestressed concrete members and mix proportioning of low-calcium fly ash concrete mixes.

Decreasing our over-reliance on cement as an ingredient in the making of concrete due to its contribution to the CO2 emissions has led to numerous researches been conducted to find suitable replacement for cement in concrete mixes. Materials like fly ash, ground granulated blast furnace slag, silica fume, rice husk ash and metakaolin among others have been identified as materials that can at the very least be used as a replacement for cement in concrete mix. These materials are referred to as supplementary cementitious materials (SCMs). This paper reviewed the work that has been done on the use of fly ash and rice husk ash as partial replacements for concrete, its chemical composition and its effect on the compressive strength of concrete. Charts, tables and figures were employed as tools to study the various chemical compounds of fly ash and rice husk ash. It was seen that depending on how the coal or rice husk was initially processed the percentage of some of the minor compounds like Sodium oxide (Na2O), Titanium oxide (TiO2) and Phosphorus pentoxide (P2O5) were sometimes very low or not recorded as part of the final product. The data on the compressive strength of concrete after fly ash and rice husk ash had been added in percentage increments of 0%, 10%, 20%, 30%, 40%, 50% and 0%, 5%, 7.5%, 10%, 12.5%, 15% respectively analysed over a minimum period of 7 days and a maximum period of 28 days found out that the optimal percentage partial replacement of fly ash and rice husk ash for a strong compressive concrete strength is 30% of fly ash and 7.5% of rice husk ash.

Blending of a large amount of waste materials such as fly ash, silica fume, rice husk ash (RHA), etc. is being done in large extents in the manufacture of cement and cementitious products. A lot of work has been done on replacement of cement with fly ash and RHA, which have shown good results with respect to strength and durability. In addition, Limestone Powder (LP), produced as by-product of stone crushers in limestone quarries, is also used as partial replacement of Ordinary Portland Cement. High amount of powders is being collected and utilization of this by-product is a big problem from the aspects of disposal, environmental pollution and health hazards. The existing blending methodology of binary blending (mixing one Supplementary Cementitious Material (SCM) with cement) and ternary blending (mixing two SCMs with cement) has improved the performance of concrete. The objective of this study aims to characterize the optimum percentage of SCMs fly ash, RHA and LP in a quaternary mix, with respect to strength and durability. As expected, the quaternary mix is very effective in enhancing the compressive, tensile and flexural strength along with durability of the concrete.

This study was focused on the use of partial replacement of cement with glass powder in high strength concrete and also copper slag as a partial replacement of coarse sand in concrete. The high strength concrete was prepared with different mineral admixtures like silica fume, fly ash and rice ash husk in different proportions. An experimental investigation has been carried to study about the effect of glass powder on high strength copper slag concrete. The range of glass powder was 10%, 15% and 20% as a replacement of cement. The range of copper slag was 0%, 20%, 40% and 60% as a replacement of natural sand. In addition to the different percentage of fly ash, silica fume, and rice husk ash 5% and 10% was also studied in copper slag concrete. Thus, a total of 51 cubes were casted and compressive strength test was performed on them. The result of the study shows that the value of average compressive strength of concrete after addition of 10%, 15% and 20% of glass powder are 70.47, 72.01 and 73.31 respectively. The value of average compressive strength after addition of 20%, 40% and 60% copper slag as a replacement of sand are 72.18, 74.38 and 73.08 respectively. The value of average compressive strength after addition of 5% and 10% fly ash as a replacement of cement are 71.56 and 73.22. The value of average compressive strength after addition of 5% and 10% silica fume as a replacement of cement are 72.33 and 73.53. The value of average compressive strength after addition of 5% and 10% rice husk ash as a replacement of cement are 72.86 and 69.49. At the level of 20% replacement of cement by glass powder meets maximum strength as compared to that of controlled concrete and copper slag high strength concrete.

Influence of water/powder ratio on strength properties of self-compacting concrete containing coal fly ash and bottom ash

This study investigated the effects of using bagasse ash (BA) and metakaolin (MK) together as substitutes for cement in self-compacting concrete (SCC), together with the addition of glass fiber (GF), on the physical and mechanical characteristics of concrete. Eighteen SCC mixes were created, each containing different proportions of BA (0%, 10%, 15%, and 20%), MK (0%, 10%, 15%, and 20%), and BA and MK collectively (10% + 5% and 10% + 10%) as cement replacements with and without 0.1% GF. Using the results of the slump flow, T500 slump flow, V-funnel, and L-box tests, the performance of fresh SCC was determined. Furthermore, this study evaluated the strength, durability, and microstructural properties of the SCC samples. The SCC mix blended with 10% BA and 5% MK revealed better flowability as the slump flow increased from 692 mm to 715 mm. A strong linear correlation was discovered between the slump flow values (mm) and V-funnel duration (sec) and blocking ratio (H2/H1) with R2 = 0.8876 and R2 = 0.8467, respectively. Of all test mixes, the SCC mix blended with 10% BA, 5% MK, and 0.1% GF (SCC1B10M5) demonstrated the highest degree of strength. At 56 days, the 10% BA, 5% MK, and 0.1 GF mix had 12.8%, 25.7%, and 22.2% higher compressive, flexural, and splitting tensile strengths than the control mix, respectively. SCC, combined with BA, MK, and GF, outperformed the control mix. After immersion in a 3% H2SO4 solution, the SCC mix having 10% BA, 5% MK, and 0.1% GF experienced a minimum reduction in weight loss and ultrasonic pulse velocity of 1.01% and 3.1%, respectively. Additionally, there was a decrease of 29.4% in the percentage of charges passed. The ideal composition was achieved by incorporating 10% BA, 5% MK, and 0.1% GF into the SCC mixture, resulting in a dense structure without any visible pores or cracks during the microstructural analysis.

Nowadays, utilizing large amount industrial by-product fly ash (FA) as the alternatives for cement in self-compacting concrete (SCC) had attracted more attention. In this study, FA was employed in SCC at five levels (0 %, 20 %, 30 %, 40 %, 50 %). The mechanical behaviors, the water porosities, the transport properties, and the sustainability of FA series SCC were investigated. At the initial curing stage (3 days), the use of FA in SCC reduces mechanical properties and increases water porosity, water absorption and water absorption coefficient (sorptivity) of SCC. FA series SCC have the lower resistance against carbon dioxide attack and chloride ion penetration than cement-based SCC. The prolonging curing time is beneficial to improve the long-term behaviors of FA- blended SCC. After SCC made by 20 %, 30 %, and 40 % FA water-curing for 90 days, there are the reduction of 0.44-2.09 % in the mechanical behaviors and the increase of 0.082-0.41 % in the water porosity, compared to pure-cement SCC. Beyond the content of FA (40 %), the difference s of the mechanical properties and the water porosity between SCC with 50 % FA and fully cement SCC are below the value of 2.5 %. With the progress in the curing time, the largest reduction rates of the water absorption and the sorptivity in all SCC mixtures were found in 50 % FA-blended SCC. Utilizing 50 % FA in SCC reduces the total charge passed values of SCC. The manufacture of 50 % FA-blended SCC has the lowest energy consumption and released amounts of CO2, NOx, and SOx in all series SCC mixtures. The application of high-level FA to SCC is the positive assistance to prepare sustainable SCC with satisfying long-term behaviors.