analysis of the physical and technical characteristics

investigations in the VNIISTROM (Building Materials Research Institute) of the USSR

In 1990 in the USSR Scientific-Industrial Association of the Wall and Binding Materials (VNIISTROM named after P.L. Budnikov) physical and technical characteristics of the “hyperpressed” (or perhaps more appropriately called «tribopressed») bricks were thoroughly analysed. The bricks were made of the compression mixture of the following composition:

• limestone – shellrock screenings – 84%
  (limestone natural strength is 30 kg/cm²);
• gray portland cement – 7%
  (portland cement type 300 (30));
• potable water – 8%;

The results of the analysis of the physical and technical properties of the solid hyperpressed brick and its brickwork are listed below :

• resistance (according to the State Standard GOST 379-79):
  «According to resistance and bend, the bricks correspond to the type «250»;
• density (of the dry brick):
  «2,19 g/cm3 – 0,19 g/cm3” higher than the density of the silicate brick»;
• water absorption (according to the State Standard GOST 7025-78 ):
  «Water absorption: 4,7 – 4,8%, less than that of the ceramic and silicate brick»
• heat conductivity (according to the State Standard GOST 7076-87 ):
  «Heat conductivity: 1,08 – 1,09 V/m K-grade, higher than that of the ceramic brick, similar to the silicate brick »;
• structure (microscopic and X -ray phase analysis):
  «A porous brick, with isolated pores, the size of big pores: 0,2 – 0,3 mm, of the small ones: 0,03 – 0,07 mm; the main phase is calcite; the average size of the basic mass of the grains is: 0,1 – 0,3 mm».

The durability of the solid brick was estimated and the following results were received:

• frost resistance (according to the State Standard GOST 7025-78 – facing wall materials) :
  «It is determined that a brick made of the limestone screenings has resisted 150 cycles of the alternate freezing and defrosting without losing its weight and without visual damages. Frost resistance of this brick is characterized by the type FRN «150». Frost resistance of the tribopressed brick (hyperpressed) is much higher than that of ceramic and silicate bricks, that proves a high durability of this new type of wall materials».
• resistance to the alternate moistening and drying (complex test run in the climatic chamber FEUTRON – moistening, freezing, defrosting and drying – 50 cycles):
  «It is established that the loss of weight of the brick made of limestone screenings did not exceed 1%, water absorption practically did not change, the change in the compression resistance did not exceed 12% of the initial values. Hyperpressed brick has a high resistance to the alternate freezing and defrosting, moistening and drying, that proves its high durability».
• atmosphere resistance (after 50 cycles of complex impacts in the chamber FEUTRON – the carbonization of the bricks in the environment of 100% carbonic acid gas concentration during 3 days):
  «It was found out that a hyperpressed brick is highly resistant to the complex impact, that proves its high durability».

Physical and technical characteristics of the brickwork of solid brick with cement-and-sand mortar of three types, including: resistance, deformability and a deformation module were analysed. The main brief conclusions:

• «Tribopressed brick can be used for the brickwork of the suporting construction of the buildings with dry, normal and humid explotation conditions, including outside and inside walls of the living roms, basements and socles».
• «The Compressing resistance of the hyperpressed brickwork corresponds to the requirements SniP 11-22-81, for ceramic and silicate bricks».

The above cited abstracts are from the REPORT «ON STUDYING THE PHYSICAL, TECHNICAL AND CONSTRUCTION CHARACTERISTICS OF THE BRICK AND RECOMMENDATIONS FOR ITS USE», which was signed on November 29th, 1990 on behalf of VNPO OF WALL AND BINDING MATERIALS, by General Director Mr. GUDKOV P.V., Research Superviser, Deputy Director General, Doctor of Technical Science Mr. AHUNDOV A.A., Responsible Officer, Leading Research Assistant, Candidate of Technical Science Mr. HVOSTINKOV S.I.

Basing on the analysis results, Technical Conditions for the «BUILDING HYPERPRESSED BRICK» TU 21-0284757-3-90 were introduced in the USSR for the first time, it was registered in the State Standard of the USSR in the Ministry of Building Materials under the number of 005/023505, from 07.12.1990 (see «STATE STANDARDS (GOSTs)»).

quality of the traditional TRIBOPRESS laying

The comparative tests of the adhesion strength of the ceramic and hyperpressed bricks to the cement mortar, run in accordance with the State Standards GOST 24992-81 (Stone constructions. The determination methods of the cohesion strength in the stone laying), showed a higher cohesion of tribopressed bricks in comparison to the ceramic ones. (see. Construction in the seismic zones, CNiP-7-81, chapter 12.1).

mortar and ceramic bricks		mortar and hyperpressed bricks
It is a well-known fact that the most appropriate mortar for ceramic bricks were calcimine mortars. The cement discovery and its wide use in construction, especially as a “liquid stone” – concrete, led to the total replacement of calcimine mortars by the cement ones. The adhesion of cement mortars to the ceramic bricks is about 1,45 kg/cm2, enough for the laying of the II category (normal cohesion with mortar is from 1,20 up to 1,80 kg/cm2). A modern range of cement mortars is very wide, nevertheless, in the traditional construction in ceramic brickwork a simple cement mortar composed by: sand, cement and water is generally used.		Tribopressed (hyperpressed) building materials are a deeply compressed “thin concrete” in which the “lack” of binding substance in comparison with a concrete stone is substituted by a “cold welding” of the filling material (raw material) under high pressure. The traditional filling materials (raw materials) of the tribopressed (hyperpressed) bricks are limestones. Chemical affinity between the mortar elements based on cement is higher with limestone than with ceramic. One of the components of tribopressed (hyperpressed) materials is cement that increases even more the adhesion of the mortars based on cement. The increased adhesion of cement mortars to the tribopressed brick is about 2,53 kg/cm2, more than enough for the I category brickwork (normal cohesion with the mortar is more than 1,80 kg/cm2).

Binding strength with the mortar SNIP P-7-81

In the Russian Federation in ROSTOVAGROPROMSTROY company, in 1996 the comparative tests of the binding strength of a ceramic brick and a tribopressed (hyperpressed) brick with a cement mortar, were run in accordance with the State Standards 24992-81 Stone Constructions. Methods of strength determination in the stone laying – at the age of 14 days. A cement mortar with a strength of 100 kg/cm2, at the age of 28 days was used.

Binding strength of the ceramic and hyperpressed bricks with a mortar

Thus, the binding strength of smooth tribopressed (hyperpressed) bricks to cement mortar is 75% higher than that of the ceramic bricks. The binding strength of tribopressed bricks with incisions to cement mortar is 98% higher than that of the ceramic ones. Conclusions of the ROSTOVAGROPROMSTROY:

• « Tribopressed brick based on shellrock according to the binding characteristics to the motar - 2,5 kg/cm2 (at the age of 14 days) can be used for the construction of any buildings in seismic zones including for the I category brickwork».
• « The use of tribopressed bricks with a ribbed suface increases a binding strength to the mortar up to 2,9 kg/cm2 (at the age of 14 days), which is 60% higher than required by SNiP-P-7-81 Construction in the seismic regions (see «State Standards»)».

strength of the brickwork made of the smooth TRIBOPRESSED bricks

The strength of the brickwork made of tribopressed bricks with a cement mortar is 50-70% higher than that of the ceramic bricks with the same mortar.

brickwork		vertical joint		horizontal joint

vertical brickwork joint		horizontal brickwork joint
adhesion surface of the contact: 481 cm2/brick The strength of the vertical joints in brickwork made of tribopressed (hyperpressed) bricks of the traditional geometry (smooth) is 1,7 times higher than that of the ceramic bricks of the same geometry and on the same mortar.		adhesion surface of the contact: 300 cm2/brick The strength of the horizontal joints in the brickwork of the tribopressed (hyperpressed) bricks of the traditional geometry (smooth) made with a mortar is 1,7 times higher than that of the ceramic bricks of the same geometry and on the same mortar.

Taking into account that tribopressed (hyperpressed) bricks are 50-70% stronger than the ceramic ones and their binding strength with mortar is 75-100% higher than with a ceramic brick, then the strength of tribopressed (hyperpressed) brickwork is 50-70% higher than that of ceramic bricks (see «State Standards»).

Strength of the antiseismic TRIBOPRESS brickwork

The joints in the antiseismic brickwork have a complicated relief and a bigger adhesion surface than the joints in the smooth brick laying.

brickwork		vertical joint		horizontal joint

vertical joint of the laying		horizontal joint of the laying
adhesion suface of the contact is 24% more than that of a smooth one It has a form of regularly repeated grooves that creates additional resistance to the interlayer shift of the antiseismic brickwork (super adhesing) equal to the strength of “splitting with a cut” of the grooves of the mortar joint in every layer of the brickwork.		adhesion suface of the contact is 15% more than that of a smooth one Together with a “male-female” system it creates additional resistance to the interlayer shift of the antiseismic brickwork (super adhesing) equal to the strength of “splitting” of the joint motar and the strength of the “cut” of the “male-female” system locks along the entire surface of every layer of the antiseismic brickwork.

Taking into account that antiseismic bricks are 2,5-3 times stronger than the ceramic ones, their brickwork strength increases 2,5-3 times at the corresponding increase of the mortar strength (see «State Standards»).

analysis of the physical and technical characteristics