Effect of Dewatering on the Strength of Lime and Cement Mortars

Abstract

This paper investigates the effects of dewatering on the strength and microstructure of mortars manufactured from Portland cement, hydrated calcium lime (CL90), and natural hydraulic limes of classification 2, 3.5, and 5 with binder/aggregate/water ratios of 1:2:0.78. Dewatering was achieved by placing the mortars on a high porosity brick. Dewatered and nondewatered specimens were exposed to an atmosphere containing 400 ppm carbon dioxide with a relative humidity of 65%, at 201C for periods of 14, 28, and 56 days. Following hardening for these periods, compressive strengths were compared with evaluate the mechanical performance. The structural morphology of the samples was determined using scanning electron microscopy and chemical composition by Raman spectroscopy. Results showed CL90 mortars are unaffected by dewatering. However, dewatering resulted in an increase in the compressive strength for the hydraulic limes and cement mortars tested.

Influence of supplementary cementitious materials on water transport kinetics and mechanical properties of hydrated lime and cement mortars

“…It has conclusively been shown that the rate of dewatering of a wet mix depends on both the suction of the absorbent substrate (the sorptivity, S) and the water retentivity of the fresh mix (the desorptivity, R) (2,3,12). The desorptivity, R, defines the water retaining ability of a wet mix which means that lower the value of R, the more water retaining the mix.…”

“…Equation [2] shows that t dw increases as the thickness of the mortar bed L increases, and decreases as the transfer sorptivity A increases. Time to dewatering also depends on α and definition of α is given in Equation [3]:…”

“…The measurement of volume fraction of water contents of the mix before and after dewatering is crucial for the calculation of α (Equation [3]). Knowing that the thickness of the mortar bed, L, is 20 mm, the time taken to dewater freshly mixed mortars when in contact with and absorbent substrates can also be calculated according to Equation [2].…”

“…This means in other words that CL90 mortars are becoming more water releasing with the replacement levels of FA and GGBS and hence resulting in a greater decrease in the volume fraction water content of the dewatered mix. The parameters α and t dw are calculated based on the Equation [3] and Equation [2] respectively. The presence of FA and GGBS resulted in an increase in both α and A in CL90 mortars.…”

Research on the modification of two traditional building materials in ancient China

“…This process is called self-repairing effect of hydraulic limestone [8][9][10][11][12][13][14] by European scholars. Although the carbonization of non-hydraulic constitute is slow, the whole process of carbonization begins from the surface and extends in depth.…”