Optimisation of mortar properties through the combined use of crushed limestone sand and silica fume

The Experimental Assessment of the Effect of Paper Waste Ash and Silica Fume on Improvement of Concrete Behavior

The potential stabilization of high calcium wood waste ash (HCWWA) derived from the wood biomass energy production for use as cementitious material using another industrial by-product, silica fume, was investigated. Throughout the study, both HCWWA and DSF were characterized in term of their respective chemical composition and mineralogical phases. Besides, physical characteristics of HCWWA and DSF in terms of particle grading and specific surface area were established in order to evaluate their suitability as for use as constituent material in blended cement. Additionally, compressive strength properties of high strength mortar produced using HCWWA and DSF blended cement were investigated. Results indicated that the use of HCWWA as a partial cement replacement did not have significant adverse effect on the workability of fresh mortar. The enhancement of the compressive of mortar was observed for mortar mixes containing DSF and HCWWA levels of cement replacement up to 16%.

In this study, the strength properties of alkali-activated silica fume (SF) mortars were investigated. The crushed limestone sand with maximum size of 0-5 mm and the sodium meta silicate (Na2SiO3) used to activate the binders were kept constant in the mortar mixtures. The mortar specimens using the replacement ratios of 0, 25, 50, 75 and 100% SF by weight of cement together with Na2SiO3 at a constant rate were produced in addition to the control mortar produced by only cement. Moreover, the mortar specimens using the replacement ratio of 4% titanium dioxide (TiO2) by weight of cement in the same mixture proportions were produced. The prismatic specimens produced from eleven different mixtures were de-moulded after a day, and the wet or dry cure was applied on the produced specimens at laboratory condition until the specimens were used for flexural strength (ffs) and compressive strength (fc) measurement at the ages of 7, 28 and 56 days. The ffs and fc values of mortars applied the wet or dry cure were compared with the results of control mortar. The findings revealed that the fc results of the alkali activated 50% SF mortars were higher than that of mortar produced with Portland cement only. It was found that the ffs and fc of alkali-activated SF mortars cured in dry condition was averagely 4% lower than that of alkali-activated SF mortars cured in wet condition.

In developed countries, use of mineral admixtures such as fly ash and silica fume has already been adopted in making concrete. This includes commercial application on a large scale either for addition or for replacement of cement. In India too such replacements have been readily accepted. With the introduction of ready mixed concrete, the process has been accelerated in recent times. An investigation was undertaken to study the effects of fly ash and silica fume in concrete. Compressive strengths at different levels of replacements were found. Silica fume from a local source and fly ash from Ramagundam thermal power station of the State of Andhra Pradesh were used. Maximum size of coarse aggregate was 12.5 mm. Water to cementitious materials ratio was 0.32 and aggregate-cementitious materials ratio was 3.2. Cement replacement levels by fly ash were 0, 10, 20, 30, and 40 percents and by silica fume were 0, 4, 8, 12, and 16 percents. Thus a total of 25 mixtures were studied. Strengths at the ages of 28 days and 56 days were found. The results are presented in tables and figures. It was found that the highest replacement level of 40% by fly ash and 16% by silica fume, simultaneously, i.e. a total replacement of cement to the extent of 56% gave a 10% increase in the 28-day compressive strength compared to that of control concrete. Maximum increase of 43% in the 28-day compressive strength was observed at a 32% level of cement replacement (20% by fly ash and 12% by silica fume).

A comparative study on the performance of sands rich and poor in fines in self-compacting concrete

The effect of curing conditions and silica fume replacement on the compressive strength and the initial surface absorption of high performance concrete is reported. The silica fume contents were 5, 10, 15 and 20%, by weight of cement. Four different curing conditions were used: air curing, control curing and two other curing conditions recommended by BS8110 and ACI308-81. The cementitious material (binder) content was constant (400 kg/m3); the water/cement (w/c) ratio was also maintained at a constant value of 0.35; while the water/binder (w/b) ratio ranged from 0.35 to 0.28. The addition of silica fume enhanced the compressive strength significantly up to 30%. The 28-day compressive strength was found to be 69.9 MPa without silica fume and it was determined to be 89.9 MPa with silica fume under the standard curing condition. The 28-day compressive strength results under the control curing condition were found to be higher than the compressive strength for specimens cured under other curing conditions. The surface absorption (ml/m2.s) was found to decrease as the percentage replacement of silica fume was increased. Control curing also decreases the surface absorption of water compared with air curing. Concrete with silica fume was less sensitive to drying than that without silica fume.

In this study, the significance of several factors in the performance of self-compacting mortar was statistically investigated. A screening design was used as a suitable design to identify the most important factors that can affect workability and compressive strength. The purpose of the study was to obtain the optimal conditions which can lead to optimal workability (slump flow, funnel time) and maximal compressive strength (2 and 28 days). Four experimental factors each at two levels, the type of supplementary cementitious material (SCM) as silica fume (SF) and metakaolin (MK); the amount of (SCM) at 5% and 15%; superplasticizer (SP) at 0.3% and 1.2% and viscosity modifying agent (VMA) at 0.05% and 0.2% were selected as potential candidates affecting the experimental outputs. The analysis of the data to obtain optimal values of the outputs was carried out by using MINITAB®. To establish the factor levels selected in this study in order to achieve optimal workability and maximal compressive strength, response optimization was applied. The predicted conditions for optimal workability were found to be 8.84% SF, 1.2% SP and 0.15% VMA. The solution proposed to maximize the compressive strength was 0.3% SP, 0.05% VMA and 9% or 9.75% SF for 2 and 28 days, respectively. By setting the factors at the specified levels, experimental values of the slump flow at 278 mm; funnel time at 8.3 s; 2- and 28-day compressive strength at 22.8 and 66.1 MPa were achieved. This resulted in the predicted and experimental values at the optimum conditions being in strong agreement.

Cement is importance as one of the strategic construction of any civilization depends, and its paramount significance in the construction of building, roads, bridges and infrastructure, which requires the use of cement with special specification and thus the use of polymers as additives to increase the compressive, flexural and tensile strength of the cement used in construction. Cement producing can possibility with high specification and for multiple uses, some studies be carried out on the use of some available additives in small quantities so as to give the cement high desirable specification in terms of color, compressive strength, tensile and permeability compared to ordinary cement. This research aims to know the extent to which some of the physical and mechanical properties of cement mortar, such as compressive strength, flexural and tensile strength, are improved upon weight substitution of specific polymeric materials with high efficiency, such as, silica fume .styrene-butadiene, styrene- acrylic in low weight ratio so that it does not add a high economic cost to the production of therequired concrete .for specific uses and sheds light on the effect of different temperatures on the properties where studied in this study . The study showed that the addition of polymeric materials (Glenium 51, silica fume, styrene –butadiene) with different weight ratio of cement weight at 20°C led to obtaining the highest compressive strength, flexural and tensile strength at the optimum level to the development and improvement of properties. Mechanical and physical cement mortar compared to the reference cement free of additives .As for the use of styrene –acrylic, it had a negative effect and led to a decrease in the compressive and tensile strength .especially in the later ages compared to the reference cement. The optimum ratio of Glenium51 was added to the optimum ratio of each material separately and the mixture was added to the cement mortar at different temperatures( 7, 20, 55 )°C .The effect of additives on the properties of the cement mortar was studied. Also, a mixture (Glenium51, silica fume, styrene-butadiene, styrene-acrylic) was added in the optimum proportions for each material to the cement mortar at different temperatures, and this addition led to increase on compressive, flexural and tensile strength at all temperatures compared with reference cement. Silica fume, styrene-butadiene rubber and styrene acrylic were added separately to the cement mortar without Glenium51, then a mixture of silica fume, styrene-butadiene, and styrene-acrylic was added to the cement mortar .The results showed that the compressive, flexural and tensile strength of cement mortar increase while styrene acrylic decrease these properties when compared with the reference mixture.In addition, the study showed the effect of temperature to the properties of added polymers with cement mortar, All experiments were performed at different temperatures (The temperature which Iraq's climate is exposed under natural conditions.All experiments were conducted at different temperatures (7, 20, 55)°C respectively, to show the effect of degrees on cement compressive strength, which the degree7 represents in winter, 20 in spring and autumn, and 55 in summer.

Plastic obtained from the discarded computers, televisions, refrigerators, and other electronic devices is termed as e-plastic waste. E-plastic waste is non-biodegradable waste. This paper focuses to investigate the replacement of fine aggregate with plastic aggregate obtained from e-plastic. The paper presents a detailed comparison of concrete properties (i.e.: compressive strength, tensile strength, flexural strength, density and workability) for normal concrete and concrete containing e-plastic fine aggregates. The testing was conducted according to the ASTM standards. 28-day Compressive, Flexural and Split tensile strengths were determined. In addition to the effect of e-plastic fine aggregate, silica fume is added as an admixture to find the effect on strengths. Authors have performed a compressive, flexural and tensile test of concrete mix with various percentages of e-plastic aggregates (i.e., 0, 5, 10, 15 and 20%) and silica fume (i.e.: 0, 5 and 10%) and concrete densities are also considered. It has been concluded that an increase in the e-plastic fine aggregate results in reduction in densities, compressive, flexural and tensile strength values. However, when we add silica fume to the concrete mixture it leads to strength values similar to the control mixture. The optimum obtained concrete blend contained 5% e-plastic fine aggregates and 10% silica fume. The addition of silica fume in concrete mixtures increases the 28-day compressive, flexural and tensile strengths. Moreover, the density of concrete decreases with the increase in the e-plastic aggregates.

Compressive strength and sulfate resistance of limestone and/or silica fume mortars

<p>Waste concrete is the most predominant constituent material among construction and demolition waste. Recycling of this material could minimize landfilled waste and mineral resources depletion. This study investigates, in laboratory scale, the production of upgraded recycled concrete aggregates, suitable for the replacement of primary (crushed limestone sand) used in cement mortars, by means of selective crushing and autogenous grinding. These particle size reduction techniques, compared to traditional crushing/grinding, have the potential to remove the brittle cement paste from the aggregates, thus significantly improving their quality. The granulometry, the density, the water absorption (EN 13755) and the flow coefficient (EN 933-6) of the produced upgraded sand was determined and compared to crushed limestone sand. Subsequently, cement mortar specimens were manufactured using upgraded aggregates for total replacement of crushed limestone sand. Specimens were tested for their compressive and flexural strength (EN 196-1), density and water absorption. Results indicated that the upgraded recycled sand produced through the selective crushing and autogenous grinding processes had improved properties compared to the one produced by conventional crushing processes (flexural and compressive strength of cement mortar specimens were increased by 29% and 7%, respectively). However, the quality of the upgraded sand is lower than that of the primary crushed limestone. To further explore the issue, it is planned to investigate in more detail the process of autogenous grinding and to investigate the use of other selective aggregate-cement paste liberation technologies.</p>

The purpose of this paper was to study the effect of use of Sudanese aggregate with supplementary cementitious materials silica fume and fly ash in high strength concrete mixes, and study the effect of water- cementitious materials ratio and concrete ingredients in compressive strength, workability and cost of high strength concrete. The concrete specimens were tested at different age levels, 7-days and 28-days for mechanical properties of concrete, namely, cube compressive strength, fresh properties, slump test. This paper presents a part of an ongoing experimental laboratory investigations being carried out for production and characterization of high strength concrete for heightening of an existing concrete dam in the south of Sudan. Brief description of the main features of the dam and concrete works are presented. Hundreds of specimens were performed and tested using local Sudanese aggregates with addition of supplementary cementitious materials (Silica Fume and Fly Ash) and Super plasticizers. Various percentages of silica fume and fly ash were added at different water/cementitious (w/cm) ratios. Thirty three trial mix designs of grade 80 MPa according to ACI 211.4, high strength concrete had been success fully produced and their mechanical properties were measured and documented. The results have offered an important insight for relationship and influence of components mixture in properties of high strength concrete and in cost. The effect of w/cm ratio on strength of high strength concrete was also highlighted. Optimum replacement percentage is not a constant one but depends on the w/cm ratio of the mix. It is concluded that local concrete materials, in combination with supplementary cementitious materials can be utilized in producing high strength concrete in Sudan, water/cementitious ratio (w/cm)is in inverse relationship with compressive strength and its effect is very strong in strength, silica fume had a positive effect in producing high strength concrete and contributed to both short and long-term properties of concrete, fly ash had inverse relationship with28 days compressive strength, fine aggregate had an inverse relationship with compressive strength and local Sudanese coarse aggregate had a strong positive effect in producing high strength concrete. Also the effect of concrete ingredients in slump and cost were studied. Keywords- Compressive strength, Fly ash, High strength concrete, Silica fume, Super- plasticizers

The crushed limestone sand is an abundant material in Tunisia, which induces many environmental problems. Indeed, available stocks of siliceous sand drastically decrease because of its massive use in hydraulic concrete. Some recent research works, carried out in Tunisia, concluded that crushed limestone sand may be used in concrete manufacture instead of siliceous sand traditionally used. In this context, an experimental study was achieved in order to quantify the influence of a partial or total substitution of siliceous sand by crushed limestone sand on hydraulic concrete performances. Preliminary chemical and physical tests on crushed sand indicated that it presented the minimum requirement for its use as aggregate in hydraulic concrete. 79 concretes were then prepared with siliceous sand, crushed limestone sand and a mix of the two sands. Their slump value and compressive strengths were measured on plain concretes. Complementary structural tests on reinforced concrete beam were also performed. The results proved that crushed limestone sand concretes showed workability and mechanical performances closed to those of siliceous sand concretes.

Use of high-performance concrete for structural applications has grown substantially in recent years. This paper focuses on studying the effect of different supplementary cementitious materials (silica fume, fly ash, ground granulated blast furnace slag, and their combinations) on strength characteristics of high-performance concrete. An experimental test programme was conducted to study the effect of such admixtures on compressive strength at 7 days and 28 days, splitting tensile and flexural tensile strengths at 28 days for high-performance concrete. A set of 60 different concrete mixtures were cast and tested with different cement replacement levels (0, 10, 20 and 30% by weight of cement) by various combinations of fly ash and ground granulated blast furnace slag with silica fume as addition (0, 2·5, 5, 7·5, 10 and 12·5% by weight of cement) for each combination. Super plasticiser was added at different dosages to achieve a constant range of slump for desired workability with a constant water–binder (w...

This study investigates the combined effect of steel fibers and silica fume on the workability, compressive strength, and flexural strength of concrete. Steel fiber content was fixed at 2% by weight of cement, while silica fume was incorporated at varying replacement levels of 0%, 5%, 10%, and 15% of cement weight. Workability was assessed using the slump test, while compressive and flexural strengths were measured at 28 days in accordance with Indonesian National Standards (SNI). The results indicate that silica fume content up to 15% has no significant adverse effect on workability, with all mixtures achieving slump values within the range of 8–12 cm, classified as good workability. The highest compressive strength was recorded for the 10% silica fume variation at 36.27 MPa, representing a 50.2% increase compared to the control. Flexural strength also peaked at 10% silica fume with a value of 3.97 MPa, corresponding to a 5.2% increase. The improvement in mechanical properties is attributed to the synergistic effect of silica fume’s pozzolanic reaction and matrix densification combined with the crack-bridging capacity of steel fibers. However, silica fume content above the optimum level resulted in a reduction of mechanical performance, likely due to increased viscosity and microcracking from autogenous shrinkage. The study concludes that a combination of 2% steel fibers and 10% silica fume provides the most balanced enhancement of mechanical performance without compromising workability.