The country held a day of mourning on Tuesday, with many flags flying at half mast.
Around 100 students gathered outside the university to protest that peace talks with the insurgent Taliban in Doha were not leading to a reduction in violence.
"Although we see these kinds of attacks on a daily basis, there are still ongoing peace talks with them, which is really terrible," said one protesting student, Zaryab Paryani.
The Taliban has denied any part in the attack, which follows a blast last month - also claimed by Islamic State - that killed dozens of students at a tutoring centre.
But some Afghan government officials, including First Vice President Amrullah Saleh, have accused the Taliban of involvement.
Taliban spokesman Zabihullah Mujahid on Twitter accused the government of "taking (the) public for fools".
Negotiators from the Afghan government and the Taliban are holding talks in Doha with the aim of brokering a peace deal as the United States withdraws troops.