Twin Towers’ Concrete Turned to Dust in Mid-Air

A striking feature of the Twin Towers’ destruction was the pulverization of most of the concrete into gravel and dust before it hit the ground. This is evident from the explosive mushrooming of the towers into vast clouds of concrete as they fell, and from the fact that virtually no large pieces of concrete were found at Ground Zero, only twisted pieces of steel.1  Estimates put the size of the particles, which also included gypsum and hydrocarbons, in the ten- to 100-micron range.2


Some idea of the volume of the dust clouds can be obtained by examining photographs taken shortly after each tower collapsed.

The researcher calling himself plaguepuppy articulated the thoroughness of the destruction and its incompatibility with the official explanation.

“In trying to come to terms with what actually happened during the collapse of the World Trade Towers, the biggest and most obvious problem that I see is the source of the enormous amount of very fine dust that was generated during the collapses. Even early on, when the tops of the buildings have barely started to move, we see this characteristic fine dust (mixed with larger chunks of debris) being shot out very energetically from the building. During the first few seconds of a gravitational fall nothing is moving very fast, and yet from the outset what appears to be powdered concrete can be seem blowing out to the sides, growing to an immense dust cloud as the collapse progresses.

The floors themselves are quite robust. Each one is 39″ thick; the top 4″ is a poured concrete slab, with interlocking vertical steel trusses (or spandrel members) underneath. This steel would absorb a lot of kinetic energy by crumpling as one floor fell onto another, at most pulverizing a small amount of concrete where the narrow edges of the trusses strike the floor below. And yet we see a very fine dust being blown very energetically out to the sides as if the entire mass of concrete (about 400,000 cubic yards for the whole building) were being converted to dust.

Remember too that the tower fell at almost the speed of a gravitational free-fall, meaning that little energy was expended doing anything other than accelerating the floor slabs.

Considering the amount of concrete in a single floor (~1 acre x 4″) and the chemical bond energy to be overcome in order to reduce it to a fine powder, it appears that a very large energy input would be needed. The only source for this, excluding for now external inputs or explosives, is the gravitational potential energy of the building. Any extraction of this energy for the disaggregation of the concrete would decrease the amount available for conversion to kinetic energy, slowing the speed of the falls. Yet we know that the buildings actually fell in about 9 seconds, only slightly less than an unimpeded free-fall from the same height. This means that very little of the gravitational energy can have gone toward pulverizing the concrete.

Even beyond the question of the energy needed, what possible mechanism exists for pulverizing these vast sheets of concrete? Remember that dust begins to appear in quantity in the very earliest stages of the collapses, when nothing is moving fast relative to anything else in the structure. How then is reinforced concrete turned into dust and ejected laterally from the building at high speed?”


Evidence indicates that the hundreds of thousands of tons of concrete in the Twin Towers was converted almost entirely to dust.

Both reports of workers at Ground Zero and photographs of the area attest to the thoroughness of the pulverization of the concrete and other non-metallic solids in the towers.3  An examination of 911Research’s extensive archives of images of Ground Zero and its immediate surroundings reveals no recognizable objects such as slabs of concrete, glass, doors, or office furniture. The identifiable constituents of the rubble can be classified into just five categories:

  • pieces of steel from the towers’ skeletons
  • pieces of aluminum cladding from the towers’ exteriors
  • unrecognizable pieces of metal
  • pieces of paper
  • dust

Despite the presence of 400,000 cubic yards of concrete in each tower, the photographs reveal almost no evidence of macroscopic pieces of its remains.

Energetic Ejections of Objects

Many of the photographs of the tower collapses show solid objects, such as sections of steel columns and aluminum cladding of the outer walls, being thrown ahead of the expanding dust cloud. This pattern is characteristic of explosive demolitions. According to Chapter 1 of FEMA’s own report pieces of the steel columns and plates of the perimeter walls were thrown over 500 feet from the towers. The distribution pattern they diagram suggests that, with both towers, perimeter wall pieces were thrown an average of about 150 to 200 feet outward. This is corroborated by the shape of the vertical holes in WTC 6.

High-Velocity “Demolition Squibs” Are Visible in the Twin Towers’ Collapses

Squibs are “blasting caps (initiators) used in the explosive industry to set off high explosives.”4  In discussions of the collapses of the WTC skyscrapers, the term has been appropriated to describe the physical appearance of puffs or jets of dust emerging from buildings during a demolition, caused by the detonation of explosive charges. Several such “squibs” can be seen in videos and photographs capturing the collapses of the North and South Towers.

Squibs in the North Tower

Some of the clearest visual evidence of squibs in the North Tower is found in a video bearing the KTLA 5 banner. It shows two very distinct squibs emerging from the North Tower’s northwest side, which is in profile on the tower’s right, at about two and five seconds into the collapse.

The photograph on this page shows two puffs of dust emerging from the walls well below the expanding dust cloud. The position and timing of the one on the northwest (right) face suggest that it is an early stage of the second squib seen in the KTLA 5 video.

3The puff in that photo on the northeast (left) side is also visible in the first photograph on this page, but the second squib on the northwest side has already been subsumed by the dust cloud.

The first photograph on this page shows a puff of dust to the right of the visible north corner of the North Tower. That appears to be the beginning of the first squib.

Most of the photographs of the North Tower collapse show it after the second squib has already been subsumed by the dust cloud.

Squibs in the South Tower

Broad dust ejections emerge from mechanical equipment floors of the South Tower.

Broad dust ejections emerge from mechanical equipment floors of the South Tower.

Squibs are also apparent in the South Tower’s collapse, though they don’t appear to be as energetic as the two North Tower squibs examined above. In this photograph a red arrow highlights a row of puffs of dust emerging from the southeast face of the South Tower about 10 floors below the bottom of the zone of total destruction.

*This “Pulverization & Ejection of Contents” primer is based on excerpts from three articles on “Concrete Pulverization”, “Explosive Events”, and “Squibs”. 

[1] Waste Industry, Others Help with Cleanup at World Trade Center Site,, 11/1/01

[2] World Trade Center Dust Analysis Offers Good News For New Yorkers,, 12/24/02 

[3] Sifting Through the Dust at Ground Zero, [cached]