Experimental Investigation on Properties of Self-Compacting and Self-Curing Concrete with Silica Fume and Light Weight Aggregates

The influences of fibres originating from different waste materials on the fresh and hardened properties of self-compacting concrete (SCC) were investigated in this study. For this purpose, a total number of 13 mixes of wood (WF), polyvinyl chloride (PF), aluminium (AF), and iron filing (IF) fibres, with volume fractions (Vf) of 0.5%, 1.0%, and 1.5% were prepared. The investigated fresh properties of the prepared mixes were slump flow, T500, V-funnel as well as L-box tests, while the hardened properties were compressive strength, flexural strength, and ultrasonic pulse velocity (UPV). The findings indicated that although the majority of the prepared SCC mixes met the required self-compacting criteria, the inclusion of the waste fibres negatively affected the mix workability, particularly when Vf of 1.5% was used. Regarding the hardened properties, SCC mixes-containing IF exhibited a slight increase in both compressive and flexural strength compared with the reference mix without fibres, whereas mixes with AF fibres demonstrated a noticeable decrease in compressive strength, but with a comparable level of flexural strength. However, the flexural strength of WF and PF decreased as their Vf increased in the SCC mixes, although a slight increase in compressive strength was noted in the mixes with PF. Furthermore, there was no reliable relationship to be constructed between the compressive strength and UPV tests for all fibres used.

Self compacting concrete (SCC) is a concrete innovation that is carried out to overcome problems during casting that does not require manual compaction even in hard-to-reach places such as tight reinforcement. In this study, 3D Dramix steel fibers and bendrat wire were used as a mixture in SCC with volume fractions of 0%, 0.5%, 1%, 1.5%. The addition of this fiber aims to determine the effect of the two fibers on SCC on compressive strength, split tensile strength and flexural tensile strength. The sample in this study was a cylinder with a diameter of 150 mm and a height of 300 mm for testing the compressive strength and split tensile strength while the flexural tensile strength used a beam sample with a size of 100x100x400 mm. All samples of these specimens were tested when the concrete was 28 days old. The increase in the value of compressive strength, split tensile strength and flexural strength at the addition of 1.5% steel fiber were 26.39%, 64.71% and 111.88% respectively for concrete with 0% fiber. While the increase in compressive strength, split tensile strength and flexural strength with the addition of 1.5% bendrat wire was 20.31%, 60.74% and 76.18% for concrete with 0% fiber, respectively.

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.

This paper evaluates the workability and hardened properties of self-compacting concrete (SCC) containing silica fume as the partial replacement of cement. SCC mixtures with 0, 2, 4, 6, 8 and 10% silica fume were tested for fresh and hardened properties. Slump flow with T500 time, L-box and V-funnel tests were performed for evaluating the workability properties of SCC mixtures. Compressive strength, splitting tensile strength and modulus of rupture were performed on hardened SCC mixtures. Experiments revealed that replacement of cement by silica fume equal to and more than 4% reduced the slump flow diameter and increased the T500 and V-funnel time linearly. Compressive strength, splitting tensile strength and modulus of rupture increased with increasing the replacement level of cement by silica fume and were found to be maximum for SCC mixture with 10% silica fume. Further, residual hardened properties of SCC mixture yielding maximum strengths (i.e., SCC with 10% silica fume) were determined experimentally after heating the concrete samples up to 200, 400, 600 and 800oC. Reductions in hardened properties up to 200oC were found to be very close to normal vibrated concrete (NVC). For 400 and 600oC reductions in hardened properties of SCC were found to be more than NVC of the same strength. Explosive spalling occurred in concrete specimens before reaching 800oC.

Superabsorbent Polymer, an internal curing material, is a significant development in concrete technology. Self-compacting concrete is popular due to high flowability or pumpability. However, the higher quantity of cementitious materials required higher moisture consumption to complete the hydration. Further moisture unavailability leads to shrinkage increment. External curing cannot give proper moisture to cementitious material at higher depth. Hence, internal curing with super absorbent polymer is an economical solution for this problem. This study examines the impact of super absorbent polymer on the mechanical and durability properties of concrete. Laboratory tests were conducted to evaluate the workability, mechanical characteristics of the concrete, such as compressive strength and flexural strength. In addition, freezing-thawing tests and carbonation tests were conducted to investigate the durability performance of concrete. Scanning electron microscopy images were also used to observe the concrete's microstructure after freezing-thawing cycles. The findings demonstrate that Compressive strength and flexural strength values decreased in water curing while in air curing, those were increased. Additionally, it was discovered that the freezing-thawing cycles decreased the compressive strength of reference concrete in standard water curing. However, compressive strength increased after freezing-thawing cycles in air-curing super absorbent polymer mixes. Scanning electron microscopy images have confirmed that the microstructure of air-curing super absorbent polymer mixes was improved

The effect of silica fume (SF) on the compressive, flexural and tensile splitting strengths of hardened concrete is studied. Seven concrete mixes are prepared using Portland slag cement (PSC) partially replaced with SF ranging from 0 to 30%. The mix proportions were obtained as per the construction practice at the site with 10% excess cement when SF is used. The optimum doses of SF for the maximal values of compressive, tensile splitting and flexural strengths at 28 d are determined. The results of this study are compared with similar results associated with the Portland cement available in the literature. A correlation, in the form of simplified equations, between the compressive, tensile splitting and flexural strengths of SF concrete and PSC is obtained. Ultrasonic pulse velocity (UPV) tests are carried out on all concrete specimens at 28 d before conducting the compression test. A relationship between UPV values and compressive strengths is proposed for SF concrete with PSC based on the experimental data.

This study experimentally investigates the effects of varying nano-silica (nano-SiO2) contents on the mechanical properties of ultra-high-performance concrete (UHPC) hardened paste, focusing on compressive and flexural strength improvements. Nano-SiO2, owing to its high surface area and reactivity, has potential to enhance UHPC performance by filling micro-pores and promoting cement hydration. In this research, UHPC hardened paste specimens were prepared with nano-SiO2 dosages of 0 %, 0.5 %, 1 %, 1.5 %, and 2 % by mass of cement, and their mechanical properties were evaluated and statistical features were analyzed. The results indicate that incorporating nano-SiO2 enhances both compressive and flexural strength of UHPC, with the optimal improvement observed at a 1 % dosage. Specifically, UHPC with 1 % nano-SiO2 exhibited a 5.1 % increase in compressive strength and a 6.3 % increase in flexural strength compared to control specimens. These findings suggest that a moderate addition of nano-SiO2 can effectively optimize UHPC’s mechanical performance, offering a promising approach for high-strength, durable concrete in demanding structural applications.

Influence of artificial aggregate on mechanical properties, fracture parameters and bond strength of concretes

Multi-scale characterization of lightweight aggregate and superabsorbent polymers influence on autogenous shrinkage and microstructure of ultra-high performance concrete

Self – compacting concrete (SCC) is a high – performance concrete that can flow under its own weight to completely fill the form work and self-consolidation without any mechanical vibration. Green concrete is defined as a concrete which uses waste material as at least one of its components, or its production process does not lead to environmental destruction. Such concrete can accelerate the placement, reduce the labor requirements needed for consolidation, finishing and eliminate environmental pollution. One alternative to reduce the cost of self-compacting concrete is the use of mineral admixtures such as silica fume, ground granulated blast furnace slag and fly ash, which is finely, divided materials added to concrete during mixture procedure .When mineral admixtures replace a part of the Portland cement, the cost of self-compacting concrete will be reduced especially if the mineral admixtures are waste or industrial by-product. The various tests for compressive, tensile and flexural strength are determined for various specimens with certain percentages ( 10 % ,30 % ) of replacement like silica fume, fly ash and combination of both fly ash and silica fume. Admixture combination of fly ash and silica fume replacing 30 % results in maximum compressive strength. Admixture of fly ash replacing 10 % results in maximum tensile and flexural strength. In order to make SCC effective, trials can be made with partial replacement of combining silica fume and fly ash to achieve the higher compressive strength. Minimum replacement of fly ash can be investigated to achieve higher tensile and flexural strength .With respect to the above combination of replacement SCC can be dealt with its several specializations to make it effective.

Abstract: Self-curing concrete, a specialized solution, eliminates external curing for optimal performance in construction. It maintains internal moisture, reducing autogenous shrinkage and early-stage cracking. This innovative approach, promoting sustainable practices, is valuable for high-rise buildings and bridges. Self-Curing properties achieved in concrete through the incorporation of Sodium Polyacrylate and Formaldehyde. Extensive testing was conducted on diverse concrete samples to evaluate their properties, encompassing workability, compressive strength, tensile strength, and flexural strength. Sodium polyacrylate which is a super absorbent polymer is added to the concrete mix of M20 & M25 grade of concrete in variations (0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%) by weight of cement. Formaldehyde added to concrete mix used as shrinkage reducing agent is added 1% with water. Light weight aggregate like brick chips replaced 10% of coarse aggregate are used because bricks absorb and holds a large amount so water. So pre-saturated brick chips are also used to provide internal curing. Sand is replaced by wood powder by 5%, as it also absorbs water. The compressive strength tests were carried out on M20 and M25 grade concretes with different water-cement ratios (for M20 w/c ratio is 0.50 & for M25 w/c ratio is 0.40), adhering to BIS: 516 – 1959 standards. The results indicated that the addition of sodium polyacrylate by weight of cement up to 0.6% led to optimal compressive strength values, beyond which further additions resulted in a decline in strength. Similarly, the split tensile strength tests for M20 and M25 grade concretes showcased the highest values at 0.6% addition of sodium polyacrylate by weight of cement. Subsequent increases in the additive led to a decrease in split tensile strength. Finally, the flexural strength tests for both M20 and M25 grade concretes yielded their highest values at 0.6% sodium polyacrylate by weight of cement, with diminishing flexural strength observed with higher additive percentages. These findings offer valuable insights into enhancing the self-curing properties of concrete and optimizing its characteristics by utilizing sodium polyacrylate as an additive.

Despite its superior mechanical properties in the hardened state, ultra-high performance concrete (UHPC) is susceptible to high autogenous shrinkage compared to high performance concrete given the high binder content and low water-to-binder ratio(w/b).Such shrinkage can increase the risk of cracking at early age and cause impairment of durability, bond, and structural integrity. Based on previous research carried out by the authors on UHPC, optimal types of pre-saturated lightweight sand (LWS) used at 15% sand replacement, by volume, 0.6% super absorbent polymer (SAP), by mass of binder, and 2% shrinkage-reducing agent (SRA), by mass of binder,were used to investigate the individual and combined effects of these materials on UHPC performance. UHPC made with 0.18 w/b and 20% and 25% fly ash and silica fume replacements, respectively,were tested to compare the effect of different shrinkage-reducing methodologies on autogenous shrinkage (ASTM C1698), drying shrinkage (ASTM C596),and compressive strength (ASTM C109).In general, the incorporation of 15% LWS led to the best overall effect on autogenous shrinkage mitigating followed by UHPC made with SAP and SRA, as shown in Fig. 1. The incorporation of 15% LWS and 0.6% SAP was shown to reduce the loss of internal relative humidity (IRH). On the other hand, the addition of SAP increased the drying shrinkage compared with the reference UHPC made without any shrinkage mitigating materials. However, the UHPC incorporating with SRA had the lowest drying shrinkage. The three shrinkage mitigation methods had some adverse effect on compressive strength at 3d, which can attribute to residual pores left behind by the SAP and porous LWS, as shown in Fig. 2a and 2b. The use of SRA can hinder cement hydration, which had a reverse effect on the enhancement of mechanical properties due to internal curing. However, the use of LWS had a non-significant impact on compressive strength at later ages given the net effect of internal curing on reducing capillary porosity and densifying the transition zone at various interfaces. In order to control the negative effect of SAP on drying shrinkage, the combination of SAP and SRA was used. The hybrid system with a low dosage (0.3%) of SAP and a high dosage(2%)of SRA, by mass of binder, exhibited the lowest autogenous shrinkage, as the coupled materials had roles in maintaining high IRH and reducing surface tension. The interaction of SAP and SRA can be explained by two mechanisms: the interaction between SRA molecules and the functional groups on the polymeric network of SAP hydrogels, as well as the reduced chemical potential of water, as shown in Fig. 2c. The addition of SRA and SAP, in a hybrid system, lowered the water absorption capacity of the SAP. In addition, an increase in SAP dosage was not beneficial in lowering the surface tension of pore solution since this led to increased demand for SRA in the pore solution to maintain the surface tension at a constant level.

This project presents the experimental study on self-compacting concrete (SCC) with replacement of cement by various percentage of Silica Fume and Fly Ash. The main objective is to determine the Flexural strength, Compressive strength and Split tensile strength of Self compacting concrete by partial replacement of cement by Silica Fume and Fly Ash. The use of fly ash in concrete today is an important subject and is of growing importance day by day. Using fly ash in concrete many provide both economic advantages and enhanced properties in the production of concrete. The addition of super plasticizer increases the workability of concrete. The work involves making seven types of SCCs mixes. For each mix preparation, twenty-one cube specimens, twenty-one-cylinder specimens and twenty-one beam specimens are cast and cured. The specimens are cured in water for 7 days, 14 days and 21 days. The results show that SCC with 5% SF and 10% gives higher values of Compressive strength, Split Tensile strength and Flexural Strength compared to other percentages of Silica Fume and Fly Ash. According to the SCC result, various percentages of AR Glass Fiber (0.1% to 0.4%) added with the optimum SCC (5% of SF+ 10% of FA) and super plasticizer is mixed with optimum SCC. After each mix proportion, specimens are cast and cured for 28 days in water and hardened properties are determined. The results show that the higher the percentage of glass fiber, the higher the values of concrete Compressive strength, Split Tensile Strength and Flexural Strength.

Ultra-High-Performance Concrete (UHPC) is considered to be a new development of concrete technology with excellent workability, high compressive strength, toughness, and long durability, etc. These characteristics are achieved by the synthetic application of strength enhancements such as the use of mineral additives, optimum particle distribution and especially the use of fiber reinforcement which greatly enhances flexural strength and toughness for the UHPC. In this paper, the influence of basalt fiber content on some properties of UHPC such as workability, compressive strength, flexural strength, elastic modulus and shrinkage were investigated. The results of this paper show that use of basalt fiber with reasonable content will not affect the workability of the concrete mixture while increasing the flexural strength, compressive strength, and elastic modulus of the UHPC. The compressive strength of concrete reaches over 120 MPa, flexural strength is over 10 MPa. UHPC sample using 1.5% fiber content will give the highest compressive and flexural strength values, this value increased about 8.5% compared to the control sample without fibers.

Self-compacting concrete (SCC) is a relevant technology and an alternative to conventional concrete in complex structures due to its exceptional workability. The rheological parameters demonstrated by SCC provide high fluidity and cohesion, resulting in high mould-filling capability and segregation resistance, as well as optimising concreting processes and reducing costs. In view of this, self-compacting lightweight concrete (SCLC) has emerged as a possible alternative as it combines the benefits of SCC and lightweight aggregate concrete (LWAC). In the production of LWC, the most widely used lightweight aggregate in the world, and also in Brazil, is still expanded clay; however, Brazilian production is restricted to the southeast region. In this context, previous studies have verified the feasibility of producing lightweight aggregates from the sintering of industrial waste and regional raw materials (Rio Grande do Norte/Brazil), such as sugarcane bagasse ash (SBA), scheelite mining residue (SMR), and local clay. Therefore, this study evaluates the influence of three lightweight aggregates, analysing their performance in comparison with SCLC produced with commercial lightweight aggregate (expanded clay). The concretes studied were subjected to characterisation tests in a fresh state; fluidity, apparent viscosity, visual stability, and passing ability were assessed through slump flow tests, flow time (T500), visual stability index, and J-ring, respectively, as well as measurement of the fresh specific mass. In the hardened state, tests were carried out to determine the compressive strength at 7 and 28 days, the dry specific mass, the chloride ion diffusion coefficient, and the thermal conductivity. The new concretes had density values ranging from 1.94 to 2.03 g/cm3 and compressive strength values at 28 days between 26.11 and 36.72 MPa. The results obtained show that it is feasible to produce SCLC with unconventional lightweight aggregates based on sugarcane bagasse waste and scheelite mining waste.