Slump Loss Research Articles

Compatibility analysis between Portland cement type I and micro/nano-SiO2 in the presence of polycarboxylate-type superplasticizers

AbstractThis study, assessed the interaction between Portland cement type I and polycarboxylate-type superplasticizers. Five systems were analyzed with the cement-superplasticizer pair being selected from the viewpoint of its rheological behavior using the Marsh cone test. The rheological behavior was analyzed using plain and mineral additions of 5, 10 and 15 wt% and 1, 2, and 3 wt% of silica fume (SF) and nanosilica (nS), respectively. Mechanical and rheological validations were carried out in binary-concretes with nS or SF. The results showed that addition of amorphous silica in different particle sizes has very different rheological results. Particularly, in SF-concretes, the samples exhibited higher susceptibility to bleeding and segregation for higher SF amounts. This limited the application of high SP dosages, but this fact induced a premature slump loss even at the early age. In contrast, nS-concretes tended to have less bleeding, increased packing density and enhanced cohesiveness of the cement ma...

Investigation on the Compatibility of Cement Paste with SNF and PCE based Superplasticizers

Background/Objectives: Cement particles disperse due to the flow character of the cement paste which also controls the quality of concrete. Cement particles also disperse due to the addition and action of Super-plasticizers (SPs) and this influences the high fluid paste behaviour. In the development of High Performance Concrete the Super-plasticizers and mineral admixtures such as fly ash plays an important role. SPs are normally adsorbed on the cement particles and sometimes the adsorption will not be even and slightly erratic. This is due to the clinker composition of cement and the type of SP used. Various combinations of materials including mineral admixtures affect the behaviour of the cement–based system and become incompatible like slump loss, delayed setting of concrete etc. Methods: In this study an attempt is made to explore maximum benefits of the compatibility between cement, Fly-ash and super-plasticizers (SP). The Flow table and marsh cone tests were conducted to determine the optimum dosage of the mixture. The different combination was tried in the cement mortar and the improvements in compressive strength were studied. Findings: Results show that the cement with 20% Fly-ash has the better compatibility with Poly carboxylate ether with optimum dosage of 0.9% by weight of cement. Improvement: The investigation shows that the polycarboxylate type superplasticizer has better compatibility with the different types of cement considered in this study.

Thermal effects of activators on the setting time and rate of workability loss of geopolymers

A number of parameters influence the properties of both fresh and harden geopolymer concretes. Similar to the case of OPC concretes, the fresh geopolymer concrete must also exhibit desirable rheology and setting behaviours in order to be useful for field applications. These properties of geopolymer concrete cannot be controlled using traditional super plasticisers, water reducer or set retarders. Therefore, the significance of understanding alternative methods to adjust the properties of fresh geopolymer concrete is very high.Use of solid alkali activators in geopolymer mixes is less hazardous than the commonly used liquid activators and yields a “cement like” mix, where only water is added for its activation and hydration. The alkali activators used in solid form instead of a liquid form changes the kinetics of the reaction, as its dissolution occurs during the mixing process. This paper presents a study of the setting time and rate of slump loss of geopolymer binders based on fly ash and slag blends and activated with pentahydrate and anhydrous sodium metasilicate. Fly ash and slag were mixed at different ratios and activated with the two solid alkali activators mentioned above. Vicat needle test and calorimetric measurements were employed to determine the setting parameters and heat generation and sink effect of geopolymer mixes. The workability was measured using a flow table to examine the rate of slump loss. The calorimetric measurements showed that activation of the fly ash and slag blend by the pentahydrate activator is accompanied by negative heat flow (heat absorption) whereas anhydrous alkali activator dissolution is accompanied by release of heat. The additional heat released during the dissolution process accelerates the setting in anhydrous alkali activated geopolymers compared to hydrated alkali activated geopolymers. It was also observed that the strength of the geopolymers in later stage changes with changing calorimetric heat flow characteristics.

Effect of Mineral Admixture and Fibers on Shrinkage Crack of Sacrificial Concrete

The ferro-siliceous sacrificial concrete is an important protection material to Nuclear power plant, high density aggregate and high fluidity can lead to occurrence of shrinkage crack. In this paper, the early-age crack and restrained shrinkage crack of sixteen types of sacrificial concrete containing different content of cementitious materials and two kinds of fibers were researched. Results showed that the workability of sacrificial concrete decreased with increasing addition of fiber, and the slump loss resulted from polypropylene (PP) fiber was much higher than that of basalt fiber. The fibers had less influence on the compressive strength, while had greater impact on the flexural strength, which was improved by 10-20%. The reduction of total cementitious materials and replacement ratio increment of mineral admixtures including fly ash and Ground Granulated Blastfurnace Slag (GGBS) in sacrificial concrete could decrease its early-age crack obviously. The utilization of 1.0-1.5kg/m(3) PP fiber could extend the cracking time and reduce the crack width of sacrificial concrete and total cracking area. The improving crack resistance capacity of sacrificial concrete resulted by basalt fiber was weaker than PP fiber. The optimized mix proportion of sacrificial concrete mixture was 450kg/m(3) total cementitious materials, 50% replacement ration of mineral admixtures and 1.0kg/m(3) PP fiber.

서중 외기온도 조건에 따른 80 MPa 고강도콘크리트의 특성

Abstract This paper evaluates the effect of hot weather conditions on the fresh concrete characteristics of 80-MPa high-strength concrete. The slump flow, packing ability, setting time, hydration heat, and compressive strength wereevaluated under exterior temperatures of 20 ℃ , 30 ℃ , and 40 ℃ . The slump flow, arrival speed of 500 mm, and theirchanges with the elapsed time were found to bring the occurrence of rapid slump loss forward by about 30 minutes when increasing the temperature by 10 ℃ from 20 ℃ . The initial and final setting times of the concrete at 20 ℃ were7 hours and 12 hours, which were reduced by 1 hour and 3 hours at 30 ℃ and by 2 hours and 5 hours at 40 ℃ , respectively. The hydration heat characteristics at 20 ℃ and 30 ℃ were similar in terms of the highest temperature ofthe concrete casting depth and the time when the maximum temperature occurred. However, at 40 ℃ , the maximum temperature occurred about 4 hours earlier, and the highest temperature per the concrete casting depth increased by about 12

Compatibility issues of cement with water reducing admixture in concrete

Summary Multiple brand of cement and water reducing admixtures are available in the market, even though these cements and admixture comply with the respective codal provisions there performance are not same in the concrete for each and every brand of cement and water reducing admixture, even if quality and source of other ingredients of concrete is kept same. This has created a lot of confusion among the user about what type/brand of admixture is used with what type/brand of cement and what should be optimum dose of admixture. Common problem associated with incompatibility issue is flash setting, delayed setting, rapid slump loss, improper strength gain and cracking, these not only effect the strength of the concrete but also the durability of the structure. Hence, in the present study different brand/type of cement and water reducing admixture available in the market is used to find study the compatibility issue and optimum dose of admixture. To achieve this marsh cone test has been performed. Test results indicate that the optimum dose of admixture vary from 0.9 to 1.1% of the weight of cement with different type/brand of cement and type/brand of admixture.

Effect of Superplasticizer Dosage on Workability and Strength Characteristics of Concrete

The use of chemical admixtures in concrete is a common solution to achieve full compaction particularly where reinforcement congestion and shortage of skilled workers. The past researchers have been underscored the use of chemical admixtures imparts the desirable properties to concrete in both fresh and hardened state. This paper has been made an attempt to study the influence of superplasticizer dose of 400ml, 600ml, 800ml, 1000ml and 1200ml/100 kg of cement on performance of Concrete. The experimental tests for fresh and hardened properties of concrete for three mixes of 30 MPa grade are studied and the results are compared with normal concrete. The tests considered for study are, slump test, slump loss, flow table and compressive strength test The results show that for the constant water cement ratio, increase of superplasticizer dose in properties of concrete leads to gain of good workability. Moreover, there is also increase in compressive strength than that of normal concrete mix.

USING OF INDUSTRIAL WASTE AS A GREEN CHEMICAL ADMIXTURE IN CONCRETE

In the modern construction practices, industrial wastes or by-products are largely used as raw materials in cement and concrete. It imparts positive environmental effect because the waste materials are not released to the environment; therefore, this research study was conducted to investigate the effects of used engine oil on properties of fresh and hardened concrete. The main variables included the type and dosage of admixture (commercially air entraining agent, used engine oil, and new engine oil), consistency, rate of slump loss, setting time and compressive and splitting tensile strength. Results showed that performance of used engine oil and the new engine oil mixes were similar. Results of this study also showed that used engine oil acted as a chemical plasticizer by improving the fluidity and the slump of the concrete mix. The used engine oil decreases the initial setting time and increases the consistency and rate of fluidity loss of ordinary Portland cement concrete. Effects of engine oil on the concrete compressive and splitting tensile strength were negative with respect to the control/reference mixes. However, engine oil concrete has a higher compressive and splitting tensile strength than the corresponding concrete mixes containing dosage of commercial air entraining agent.

Durability of latex-modified concrete carried by ready-mix truck for concrete rooftops

This study was initiated to investigate the properties of latex-modified concrete (LMC) carried by ready-mix trucks. Generally, LMC used as an overlay in bridge projects is hardened much more quickly than normal concrete, and the LMC is fabricated by adding latex into the concrete mixture in a mobile mixer near the bridge construction site. LMC is particularly used due to its exceptional bond strength and durability. This study focused on the use of LMC for the overlay of a building rooftop, such as might be required when the concrete on a concrete rooftop exposed to severe weather in winter is beyond repair and thus needs to be replaced. However, for building repairs in a city, a mobile mixer may be unsuitable for use due to the associated loud noise and the restricted available area. In such a case, the LMC would need to be fabricated in a cement plant and then transported to site in ready-mix trucks. In this study, several experiments were conducted to verify whether transported LMC can work effectively and maintain durability. Slump test results revealed a little slump loss after LMC was carried for 60 min. The overall experimental results showed that LMC transported in ready-mix trucks could be an appropriate alternative method to repair deteriorated concrete on building rooftops in urban areas.

화쇄류 퇴적물을 혼입한 콘크리트의 기초특성 평가

The aim of this study was to investigate the fundamental properties of pyroclastic flow deposit (PFD), and evaluate the fresh and strength properties of concrete mixed with PFD by indoor tests. The fresh properties, strength properties, shrinkage properties, and durability of the concrete mixed with PFD were also evaluated by outdoor plant tests. the harmful alkali-silica reaction did not occur by mixing concrete with PFD. ages. Moreover, no difficulty was found to be associated with concrete manufacture in the plant because no change in air contents and noticeable slump loss occurred by mixing concrete with PFD. The strength properties, shrinkage properties, and durability of the concrete mixed with PFD were also compared with those of normal concrete. With a suitable temperature control and curing method of concrete, the concrete mixed with PFD is considered to be useful in the construction material field.

Methods for Inhibition of Fluidity Loss of Concrete Mixed with Superplasticizers

The slump loss of fresh concrete mixed with superplasticizers should be well controlled to ensure its transportation and pumping. In this paper, we describe a comprehensive overview of the mechanism of fluidity loss and then analyze the reason for the change. Researches show that the slump loss of fresh concrete is influenced by the mineral composition of cement clinker, the type and characteristics of aggregate, the species and dosage of admixture, the mix proportion and the construction environment, etc. Thus, a series of methods proven to be effective, such as adjustment of raw materials, adding methods of chemical admixture, synthesis of new types of superplasticizers, etc. have been proposed to solve the problems.

Adsorption properties of CFBC ash–cement pastes as compared with PCC fly ash–cement pastes

Circulating fluidized bed combustion (CFBC) ash can be potentially used as supplementary cementitious materials for concrete production due to its desirable pozzolanic activity. The adsorption properties of CFBC ash–cement pastes were studied, and ordinary pulverized coal combustion (PCC) fly ash–cement pastes were used as control. The water-adsorption and superplasticizer (SP)-adsorption properties of the pastes were evaluated by water demand and UV-visible absorption spectroscopy respectively. The results show that CFBC ash–cement system has greater compressive strength as compared with PCC fly ash–cement system at a given curing age, although the water demand of the former is significantly higher than that of the latter. CFBC ash–cement pastes possess higher adsorption ability of aliphatic SP than PCC fly ash–cement pastes and the adsorption amount increases with an increase in ash replacement ratio. CFBC ash–cement pastes exhibit lower workability with higher slump loss. It is concluded that CFBC ash can be potentially used as supplementary cementitious material in concrete production, but the mix design of CFBC ash concrete needs to be appropriately adjusted. It is suggested that CFBC ash is used for the production of the concrete needing low flowability.

CERAMIC WASTE POWDER AS SUPPLEMENTARY CEMENTING MATERIAL IN CONCRETE MIXTURES

Green environment is a challenging concern to accomplish in today’s world. This could be achieved through a beneficial recycling procedure by reusing solid waste materials. Ceramic tiles are widely used in most structures; its production creates waste powder. Concrete that contains solid waste is referred to as “Green” concrete. Using ceramic waste powder (CWP) as an alternative ingredient in concrete will have a positive environmental impact furthermore will help reserve natural resources. In this study CWP will be investigated as supplementary cementing material (SCM) in making concrete. The ceramic waste powder will be used as SCM with different dosages replacing cement. The effect of ceramic waste powder as SCM on the properties of fresh concrete will be investigated such as slump, slump loss and setting time. The properties of hardened concrete will be assessed through compressive strength development, drying shrinkage and durability characteristics was evaluated by rapid chloride permeability test (RCPT) and bulk electrical resistivity. Test results show that CWP can be used as SCM in making concrete. The outcomes of the study shed light on how CWP could be utilized effectively as an alternative ingredient of concrete and the optimum dosage for use which will result in an effective way for using solid waste and protecting the environment.

Effect of Mixing Time on Flowability and Slump Retention of Self-Compacting Paste System Incorporating Various Secondary Raw Materials

Good workability at construction site is most important aspect of self-compacting concrete. But long delivery times can cause slump loss, which is more pronounced when mineral additives are incorporated into the concrete system. The aim of this paper is to study the effects of prolonged mixing on the flowability and slump retention under action of a high-performance polycarboxylic (PEC)-based superplasticizer used in self-compacting paste systems (SCPs) incorporating various secondary raw materials (SRMs). Experimentation for this research paper was focused on mixing times and slump retention of SCPs incorporating ASTM Class F fly ash (FA), silica fume (SF) and locally available marble powder (MP). While experimenting with SCPs, total mixing time was first restricted to 3 min of mixing to achieve the target flow of 30±1 cm, which was then prolonged to total mixing time of 10 and 20 min keeping the superplasticizer content constant, which showed a more enhanced flow with reduced timing due to better activation of superplasticizer, or enhanced workability but showed some traces of bleeding in the formulations containing MP. The samples were thereafter prepared for strength measurement as per EN-196. Parameters like flow response, strength and microstructures were studied by varying two basic factors in progression: shear time and hold time. Hydration kinetics were also affected by prolonged mixing, and it also decreased the initial and final setting time. FA showed better rheological behaviour upon extended mixing regimes as compared to SF or any other SRMs.

Workability, mechanical properties and affinity of artificial reef concrete

A new artificial reef concrete (NARC) with sulphoaluminate cement, marine sand and sea water et al. was proposed. The effect of cement type, sand type and water type on the workability (namely slump, slump loss cohesiveness, water retention), mechanical properties namely compressive strength, splitting tensile strength and dynamic elastic modulus) and affinity (namely surface initial pH value and the leaching rate of alkaline material in concrete) of concrete was studied. The microstructure of concrete was detected by X-ray diffraction, scanning electron microscope and pore structure analyzer, respectively. The studies show that NARC has superior workability, mechanical properties and affinity compared to ordinary Portland cement concrete with river sand and fresh water. Therefore, the feasibility of NARC in artificial reef is verified.

혼화재 및 혼화제의 조절에 의한 서중 콘크리트의 효과적 관리

본 연구는 슬럼프 감소, 연행 공기 부족, 건조수축 균열, 강도감소 등 굳지 않은 콘크리트와 굳은 콘크리트의 성질에 대한 타설시 고온의 악영향에 대한 원인분석을 실시하고 이를 경감시키기 위한 감수제, 공기연행제, 지연제 등의 화학적 혼화제와 플라이 애쉬, 고로 슬래그 등의 무기질 혼화재의 다양한 적용이 검토되었다. 즉, 서중 콘크리트의 품질향상을 위한 다양한 콘크리트 배합이 설계되고 각 배합에서의 굳지 않은 콘크리트 및 굳은 콘크리트 에 대한 영향이 분석되고 몇 가지의 최적 배합이 도출되었다. The undesirable effects of elevated external temperatures at placement on the properties of the fresh and hardened concrete are discussed briefly, and the possible use of the mineral admixtures to mitigate them and the association with water-reducing and retarding admixtures in terms of the mix design which are critical for minimizing slump loss and entrained air loss are examined in this study. To investigate the effects of such the mineral and chemical admixtures on the fresh and hardened properties of concrete exposed to high temperature, a series of concrete mixtures subjected to the high temperature were carried out and then fresh and hardened properties of the mixtures were analyzed and evaluated. Based on the results, new guide lines concerning the appropriate admixtures for hot weather are suggested.

Properties of cold bonded quarry dust coarse aggregates and its use in concrete

In this study, artificial coarse aggregates are prepared by a cold bonding technique. The waste materials, namely, fly ash and quarry dust, are used for the preparation of the cold bonded artificial aggregate. Portland cement is used as the binder material. The independent variables considered for the preparation of the artificial aggregate are cement and fly ash contents. The properties of the artificial aggregate are determined and regression models are proposed for predicting these properties. The strength and workability of concrete containing artificial aggregate is determined. The slump loss of concrete containing artificial aggregate is found to be gradual. The concretes with strengths of up to 30MPa is prepared using artificial aggregates. The study promotes the use of waste material and supports sustainable construction practices.

The Influence of Extra Mixing Water on the Properties of Structural Lightweight Aggregate Concrete

Because of high water absorption capacity of lightweight aggregates, the workable concrete mixtures become stiff within a few minutes of mixing. Rather, many ready mix producers will typically pre-wet the aggregate, however this procedure may complicate the technological process. Extra water in structural lightweight aggregate concrete apart workability affects the degree of cement hydration as well as deformation properties of concrete. So, the main objective of this research is to determine the impact of volume of water per cubic meter of concrete needed to be supplied by LWA or by adding extra mixing water on the properties of SLWAC – workability, slump loss, relative humidity change, autogenous shrinkage, and compressive strength.

Use and Properties of Blast Furnace Slag as a Building Material- A Review

This paper aims at bringing a literature review on the uses and properties of popular industrial and mineral byproduct slag. At the present, most industrial slags are being used without taking full advantage of their properties or disposed rather than used. The use of slag in replacing Portland cement by GGBFS is not very common. The industrial slags, which have cementitious or pozzolanic properties, should be used as partial or full replacement for Portland cement rather than as bulk aggregates or ballasts because of the high cost of Portland cement, which is attribted to the high energy consumption for the production of Portland cement. The traditional way to utilize metallurgical slags in cementing materials is to partially replace Portland cement. The practice of using such mineral admixtures in construction will reduce the need of portland cement and its use in various parts of the world, thus greatly reducing the amount of pollution and pave a way for a cleaner and more economical construction material, of which India is in a great need.
 The literary investigation was carried out on different forms of slag used in construction, i.e. slag aggregates, ground granulated blast furnace slag (GGBFS) and slag mixed with clinker in cement production. Many different properties were examined during the literature review, all segregated into separate categories based on the type of usage, particle size, chemical composition and amount of usage. The base samples ranged from cement sample to concrete cubes. The properties investigated from various sources of literature were compressive strength, flexure strength, duability, abrasion resistance, drying shrinkage, reactivity, hydraulic power, hydration and slump loss. Also properties related to environmental effects like cabonation depth, chloride resistance, sulphate resistance, percentage of water absorption, heat resistance and resistance to freeze and thaw cycles. Its activation with innovative methods and certain reasons were found out which attributed to such behaviour such as glass content, microstructure, pH nature, pore size etc. 
 The behaviour of concrete samples were also investigated with some agents, i.e. samples with some extra chemical admixtures, air entraining agents, and several other mineral and pozzolanic admixtures like fly ash and Rice husk ash. The performance of Slag in different situations ( like its use in reinforced concrete ) and environment (like corrosive sea or marine environment ) was also found out and compared to control concrete. Also differentiation was done on the basis of formation of slag aggregates, i.e. the variation in properties of slag based construction materials vary when slag is created employing different techniques. The investigation will also explain the different problems faced by civil engineers in using slag as a major component in building materials. The review will also explore the future of polyblended cements constituting slag as the main constituent and its scope to be used with agricultural byproducts like Rice Husk ash, or surkhi and other industrial byproducts like fly ash.

Self-Compacting and Tiny Expanding Steel Tube Concrete Using in Large Span Bridges

The experimental studies on self-compacting and tiny expanding concrete filled in steel tube are introduced, which including the measurement of low ability of mixtures, the proportioning of the concrete filled in steel tube. The self-compacting and tiny expanding steel tube concrete has been applied in a large span bridge structure. The state of construction shows that the concrete have a good pump ability, a small loss of slump, a high strength early strength and a better self-compacting property.