Properties and microstructure of alkali-activated red clay brick waste

TLDR: In this paper, the properties and microstructure of alkali-activated cement pastes and mortars produced using red clay brick waste were investigated, and it was shown that the type and concentration of acid activator can be optimised to produce mortar samples with compressive strengths up to 50MPa after curing for 7 days at 65°C.

About: This article is published in Construction and Building Materials.The article was published on 2013-06-01 and is currently open access. It has received 241 citations till now. The article focuses on the topics: Demolition waste & Cement.

Figures

Table 1. Chemical composition of RCBW material.

Table 2. Mix proportions of alkaline activated mortars.

Table 3. Thermogravimetric total loss of weight in RCBW pastes cured at 65°C

Frequently asked questions

Q1. Why do zeolitic-like phases less likely to form in highly concentrated solutions?

4 According to Duxson et al. [13], this is because zeolitic-like phases are less likely to form in highly 5 concentrated solutions due to increased difficulties in phase transport and reorganization. 

Q2. How many pores were formed in the cement paste?

In Portland cement pastes C-S-H gel grows outwards from the 27 surface of hydrating cement grains, forming C-S-H g c28 pores, which are much larger and are the remains of originally water-filled spaces that have not 29 become filled with C-S-H gel [35]. 

Q3. What is the effect of the w/b ratio on the compressive strength of the mortar?

The 11 compressive strength increases as the w/b ratio decreases when the activator/binder and SiO2/Na2O 12 ratios are kept constant ( . 

Q4. Why is the pore size of the RCBW sample higher than the average?

higher durability alkali-activated RCBW samples with sodium silicate can 9be expected due to the reduced ability of aggressive chemical agents to penetrate the microstructure. 

Q5. How many molal of Na+ was used in the sample?

the concentration Na+ in the solution increased for 10 mixtures with w/b ratio of 0.40 (8 molal) and 0.35 (9 molal). 

Q6. What is the pore size distribution of the Portland cement paste?

After analyzing the hydration mechanisms of Portland cement 25 and inorganic polymer pastes, Lloyd et al. [34] also concluded that larger pores may be expected in 26 samples activated without silicate. 

Q7. How much weight loss did the reduction in the w/b ratio mean?

The reduction in the w/b ratio did not decrease 18 the total weight loss, suggesting that the water molecules and OH- groups bonded to the geopolymer 19 matrix are not related to the initial mix water.