CEMENT HYDRATION AND MICROSTRUCTURE

what is stage 1 of cement hydration

initial hydrolsis (15 minutes) is the process which changes the pH from 7 to 12.5

label all stages in this photo

initial hydrolsis, domant/induction period, acceleration, deceleration, steady state

what is stage 2 of the cement hydration process

the dormant/induction period where the gel begins to interlock and form a weak framework

what is stage 3 of the cement hydration process

acceleration stage where the gel forms a stronger skeletal framework and particle movement stops

what is stage 4 of the cement hydration process

the decleration stage where the rate of early strength gain is determined

what is stage 5 of the cement hydration process

the steady state phase which determines the long-term strength and durability of the cement.

in stages 4 and 5 the reaction at the cement grain boundary, water must diffuse through the CSH gel to the reactive surface making…

the reation slows as hydration advances

what does the heat evolution graph look like for portland cement

C3S and C3A hydration are used in stages 3 and 4

disucss about the devlopment of microstructure from the inital mix to 90 days

the progression of the cement microstructure evolves significantly as hydration continues, transitioning from poorly connected flocs and unreacted grains at early ages to a denser, more interconnected network of hydration products by 90 days, enhancing mechanical properties and durability.

what does the delvopment of microstructure graph look like

this

what does the graph of strength vs. porosity look like

as porosity increases, the strength decreases

how is the inital proxmity of the cement grains in the concrete mixture measured

by the water/cement (w/c) ratio

can you draw the graph relating w/c ratio to the compressive strength

The graph typically shows that as the water/cement (w/c) ratio increases, the compressive strength of concrete decreases. It often exhibits a nonlinear relationship, indicating significantly reduced strength at higher w/c ratios.

can you draw the graph of w/c ratio vs. porosity or permeability

The graph illustrates that as the water/cement (w/c) ratio increases, both porosity and permeability typically increase, demonstrating a positive correlation between these two properties.

what is the effect of temperature on hydration

higher temperatures accelerate the hydration process, leading to increased strength devlopment

draw the effective moisture on hydration graph

what are the 4 components of hydrated cement paste to consider

1. CSH

2. Porosity (and water)

3. Calcium hydroxide

4. Ettringite

what are the physical features of CSH

not well crystallized materal and is compromised of extremely small irrecgular particles