Impact of Wet and Sealed Curing on Curling in Cement Paste Beams from Drying Shrinkage

2015 ◽  
Vol 112 (1) ◽  
Author(s):  
Amir Hajibabaee ◽  
M. Tyler Ley
Keyword(s):  
Cement Paste ◽  
Drying Shrinkage

Effect of Aggregate on Drying Shrinkage of Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 701-708 ◽  
Author(s):  
Ru Mu ◽  
Wen Ling Tian ◽  
Yong Gang Guo
Keyword(s):  
Cement Paste ◽  
Volume Fraction ◽  
Drying Shrinkage ◽  
Moisture Diffusion ◽  
Moisture Loss ◽  
Normal Concrete ◽  
New Model ◽  
Model Code

A modified version of an existing drying shrinkage model developed by the authors is proposed which incorporates the influence of the aggregate on the process of shrinking. Whereas it is traditionally thought that the aggregate restrains the deformation of the cement paste and hence the shrinkage of the concrete, in this paper, the effect of aggregate on shrinkage is better represented by considering the effect of the aggregate on moisture diffusion. It is suggested that the presence of the aggregate modifies the diffusion of moisture which governs the moisture loss and hence the drying of concrete. Also, as the volume fraction of the aggregate in a normal concrete is about 75% or more, the shrinkage of the cement paste is ‘diluted’ by the aggregate in the concrete. Taking into account these effects, this new diffusion based shrinkage model has been proposed. To assess the accuracy of the new model the shrinkage of two concrete mixes is predicted and compared with the measured shrinkage of these mixes. Comparisons are also drawn with the shrinkage predicted using the Model Code 1990 (MC90). It was observed that the new model proposed here predicts the shrinkage of the concrete mixes more accurately than the MC90 model, particularly at early ages.

scholarly journals PROPERTIES OF CEMENT PASTE AND CONCRETE CONTAINING CALCIUM CARBIDE WASTE AS ADDITIVE

2016 ◽  
Vol 36 (1) ◽  
pp. 26-31
Author(s):  
EN Ogork ◽  
TS Ibrahim
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Drying Shrinkage ◽  
Calcium Carbide ◽  
Linear Shrinkage ◽  
Hardened Concrete ◽  
Concrete Compressive Strength ◽  
Initial Setting Time ◽  
Standard Procedures

This paper assessed the effect of calcium carbide waste (CCW) as additive on the properties of cement paste and concrete. The CCW used was sourced from a local panel beating workshop. It was sundried and sieved through a 75 µm sieve and characterized by X-Ray Fluorescence (XRF) analytical method. The consistency, setting times and drying linear shrinkage of cement paste with CCW addition of 0, 0.25, 0.5, 0.75 and 1.0 %, respectively by weight of cement were investigated in accordance with standard procedures. The slump values of fresh concrete containing CCW as additive and of 1:2:4 mix ratio and water-cement ratio of 0.5 was determined. A total of sixty numbers of 150 mm cubes of hardened concrete were tested for compressive strength at 1, 3, 7, 28 and 56 days of curing in accordance with standard procedures. The concrete compressive strength was also modeled using Minitab statistical software based on linear regression technique. The results of the investigations showed that CCW was predominantly of calcium oxide (95.69 %) and a combined SiO2, Al2O3 and Fe2O3 content of 3.14 %. The addition of CCW in cement decreased drying shrinkage (100 %), initial setting time (78 %) and final setting time (57 %), but increased consistency (14 %) at 1.0 % CCW content. The addition of CCW in concrete also showed slight increase in slump (6.5 %) and increase in compressive strength with increase in CCW additive up to 0.5 % and decrease in compressive strength with further increase in CCW content. The 28 days compressive strength of concrete with 0.5 % CCW content was 6.4 % more than normal, while that of concrete with 1.0 % CCW content was 14.9 % less than normal. The compressive strength model of CCW-concrete was developed with R2 value of 0.830 and could be used to predict concrete compressive strength. http://dx.doi.org/10.4314/njt.v36i1.4

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