Volume Stability of Cement Paste Containing Limestone Fines

Abstract

The common cause of cracking in cement paste is shrinkage due to different reasons, such as loss of water and chemical reactions. Incorporating limestone fines (LF) as a cement replacement can affect the shrinkage of the paste. To examine this effect, five paste mixes were prepared with 0, 5, 10, 15 and 20% LF as a cement replacement and with a water-to-binder ratio (w/b) of 0.45. Four volume stability tests were conducted for each paste: chemical, autogenous and drying shrinkage and expansion. Chemical shrinkage was tested each hour for the first 24 h and thereafter every 2 days for a total period of 90 days. The drying shrinkage, autogenous shrinkage and expansion were monitored every 2 days until 90 days. The results showed that replacing 15% LF enhanced the chemical shrinkage of the paste. However, autogenous shrinkage of the paste was found to increase between 0 and 10% LF and decline sharply at 15 and 20% LF. Drying shrinkage was found to increase with the increase in LF content. Expansion exhibited little variation between 0 and 10% LF and an increase for replacement above 15% LF. These results are discussed in terms of the formation of hydration products and self-desiccation due to hydration.

Mechanical and Microstructural Properties of Composite Mortars with Lime, Silica Fume and Rice Husk Ash

“…Thus, water absorption was higher in the LRA and LSR mortars than LSF mortar. The SEM images of all lime composite mortars exhibits a maximum density of the spherical microstructure at both 7 and 28 curing days, while the SEM images of lime mortar do not have any hydrate growth and only the thick white calcium carbonate granules were viewed [47][48][49][50][51][52][53][54]. As per EDX, lime has an increasing content of calcium from 7 to 28 days as a result of carbonation.…”

“…Since carbonation is a slow process, the microstructure growth goes on developing at latter stages. Overall, the lime composite mortar exhibits the dense spherical hydrates (Type III -CSH) [14,18,[47][48][49][50][51][52][53][54]. There was no formation of acicular and hexagonal CSH morphologies found in the samples.…”

“…It was observed that the lime mortar bar exhibits higher shrinkage than others. Carbonation of lime is initiated after the hardening of lime mortar leads to surface voids [44][45][46][47][48][49][50][51][52][53][54]. Lime composite mortar undergoes less shrinkage due to the formation of hydration products as a result of pozzolanic activity and hydration.…”

“…Hence, small pores are created in the surface of mortar after the evaporation of released water. At higher curing ages, RHA absorbs less water because of the complete utilisation of active silica and therefore the reduction of permeable voids in it [47][48][49][50][51][52][53][54]. At a saturated condition, water penetrated through these pores and filled up the voids.…”

Optimization of rapid-repair material ratio and performance analysis based on orthogonal test

“…Cement-based materials have significant chemical shrinkage and self-shrinkage in the early stage. The autogenous shrinkage strains of the concrete with a high w/c ratio developed rapidly, even at earlier ages [82][83][84]. The limited expansion and contraction rate can reflect the microstructure of steel fiber and cement-based materials in a macroscopic way.…”