International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 02 | Feb -2017
p-ISSN: 2395-0072
www.irjet.net
A STUDY ON SELF-CURING AND SELF-COMPACTING CONCRETE USING POLYETHYLENE GLYCOL 1Dadaji
B. Jadhav, 2Ranjana Ghate,
1Dadaji
B Jadhav Is Currently Pursuing Master Degree Program In Structural Engineering And Construction, BIT Ballarpur, Maharashtra, India. 2Ranjana Ghate Is An Astt. Prof. In Dept. Of Civil Engineering, BIT Ballarpur, Maharashtra, India. ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Self-curing is done in order to fulfill the water
requirements of concrete whereas self-compacting concrete is prepared so that it can be placed in difficult positions and congested reinforcements. This investigation is aimed to utilize the benefits of both self-curing as well as self-compacting. The present investigation involves the use of self-curing agent viz., polyethylene glycol (PEG) of molecular weight 4000 (PEG 4000) for dosages ranging between 0.1 to 1% by weight of cement added to mixing water. Two mixes with different w/c ratio were considered in the investigation. Workability tests i.e. slump flow, T50, V-funnel, J-ring, L-box were conducted on the fresh concrete whereas water retention and compressive strength were evaluated to determine the properties of hardened concrete. Comparative studies were carried out for water retention and compressive strength for conventional SCC and self-cured SCC. The compressive strength of self-cured SCC are comparable with traditional cured specimens at lower w/c ratio whereas does not provide satisfactory results at higher w/c ratio. Key Words: self-curing, polyethylene glycol (PEG), water retention, compressive strength.
1. INTRODUCTION This chapter deals with the introduction to different methods of curing and the difficulties in conventional curing. It also deals with the introduction of self-compacting concrete with its advantages and disadvantages. The chapter focuses on the need of self-curing along with self compacting along with its mechanism, materials and advantages.
1.1 Need for self–curing When the mineral admixtures react completely in a blended cement system, their demand for curing water (external or internal) can be much greater than that in a conventional ordinary Portland cement concrete. When this water is not readily available, due to depercolation of the capillary porosity, for example, significant autogenous deformation and (early-age) cracking may result. Due to the chemical shrinkage occurring during cement hydration, empty pores Š 2017, IRJET
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Impact Factor value: 5.181
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are created within the cement paste, leading to a reduction in its internal relative humidity and also to shrinkage which may cause early-age cracking. This situation is intensified in HPC (compared to conventional concrete) due to its generally higher cement content, reduced water/cement (w/ c) ratio and the pozzolanic mineral admixtures (fly ash, silica fume). The empty pores created during self-desiccation induce shrinkage stresses and also influence the kinetics of cement hydration process, limiting the final degree of hydration. The strength achieved by IC could be more than that possible under saturated curing conditions. Often specially in HPC, it is not easily possible to provide curing water from the top surface at the rate required to satisfy the ongoing chemical shrinkage, due to the extremely low permeabilities often achieved.
1.2 Mechanism of internal curing Continuous evaporation of moisture takes place from an exposed surface due to the difference in chemical potentials (free energy) between the vapour and liquid phases. The polymers added in the mix mainly form hydrogen bonds with water molecules and reduce the chemical potential of the molecules which in turn reduces the vapour pressure, thus reducing the rate of evaporation from the surface.
1.3 Potential materials for self-curing The following materials can provide internal water reservoirs: [1] Lightweight Aggregate (natural and synthetic, expanded shale), [2] LWS Sand (Water absorption =17 %) [3] LWA 19mm Coarse (Water absorption = 20%) [4] Super-absorbent Polymers (SAP) (60-300 mm size) [5] SRA (Shrinkage Reducing Admixture) (propylene glycol type i.e. polyethylene-glycol) [6] Wood powder
1.4 Concrete deficiencies that self-curing can address The benefit from self-curing can be expected when ISO 9001:2008 Certified Journal
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