The millionaire president, who retains vast business interests but swears by arrangements aimed at avoiding conflicts of interests, faced widening revolt this week after increasing numbers of labor union members and teachers threw their support behind students.
Protesters' representatives said their calls for general strikes across the country received greater attention than anticipated. As the protests grow, the lists of reforms demanded by those taking part in street marches and work stoppages are multiplying.
Rather than relent, Pinera said he was pained to see "those working so hard to paralyze Chile."
A central union of workers added to general calls for education reforms a longer list of changes, which includes a redrafting of the constitution and statutes to remove what critics see as vestiges of the past military dictatorial regimes, notably the highly controversial rule of Gen. Augusto Pinochet from 1973-90.
Pinera came to power in March 2010 after a democratic election that displaced hugely popular Michelle Bachelet. He pledged sweeping modernization and promised to bring Chileans into the 21st century with economic liberalization, state investment in gigantic development projects and transformation of a society bedeviled by sharp economic disparities.
Pinera saw his plans founder when an 8.8-magnitude earthquake struck the country in February 2010, causing tens of millions of dollars of damage and destruction. Pinera led a swift economic and social regeneration but the work used up cash reserves he hoped to use for the promised march to progress.
Critics question Pinera's style of government and claim he lacks communication skills necessary to engage with all strata of Chilean society.
The Unitary Central for Workers called for a nationwide strike for the second consecutive day Thursday and invited other unions to join the protest action.
Thousands of protesters barricaded roads and burned tires and debris as the strike went into full swing. Officials put the law enforcement agencies on alert to prevent a repetition of protests earlier in August that deteriorated into violent clashes between police and demonstrators.
Student protests against high tuition fees began about two months ago and focused on private academic institutions operating with impunity, alleged corruption and favoritism in the education system.
Both the Interior Ministry and law enforcement commanders faced angry charges that unarmed protesters received beatings, summary detentions and abusive treatment in police custody.
Protest leaders said they hoped to make the rallies "the biggest national strike of the last decade." It is the first 48-hour national strike since the Pinochet dictatorship.
Government spokesman Andres Chadwick said police defused some protests and claimed the situation was normal beyond traffic disruptions.
Finance Minister Felipe Larrain called the protest illegal and warned of a damaging impact on Chile's economic and social fabric.
The Chilean economy may be losing up to $200 million a day, officials said.
Analysts said Pinera's decision to fill his Cabinet with technocrats and business experts might be well-intentioned but the lack of public savvy political negotiators appears to be alienating many Chileans. A Cabinet reshuffle in July, the second since Pinera assumed office last year, failed to defuse tensions.
The outcome of the protests is likely to hinder the president's move to push through sweeping economic reforms, including plans to integrate Chile more comprehensively with the global markets.
Chile was badly hit by the 2008 economic crisis. Critics blamed the country's connectivity with international markets for the problems faced after the economic downturn.