Attention has been paid especially to reinforcement for earthquake resistance and repair (REFRETE/refresh method) of concrete structures in urban areas. We entered the field of frame reinforcement and repair earlier than any other competitor, capturing customers' confidence through fireproofing works to protect steel frames from collapsing due to fire, sales of the fireproofing material,"Rock Wool" and rust/corrosion proofing works for steel structures by means of the normal-temperature zinc-aluminum pseudo alloy spraying method (MS method). While needs for resource saving and recycling are increasing, we will make dynamic efforts for extension of the life cycle of structures.

Cracking in concrete occurs by retention of its volume change caused by drying shrinkage, Hydration heat, rapid change of temperature or humidity, etc. Furthermore, structural cracking caused by corrosion of re-bars which originates from carbonation of concrete, salt damage, etc. after construction, earthquakes, land dipping. These cracking spoil neither beauty nor leading to decline of performance, water leakage, and finally partial collapse of the structure.
The proposals on measures to cracking is to compensate cracking caused by drying shrinkage or Hydration heat, etc., and these are applied at building concrete structure.

1. The proposal on compensation of cracking on early-stage

Cracking in concrete or mortar occurs when the force for cracking is beyond the tensile strength of the concrete or the mortar, and the force for cracking occurs by the complex factors such as various kinds of temperatures, dissipation of water, difference of degree of retention, or volume change, etc. on the first stage of the occurrence of the force. According to previously setting up Hyper Net 60 at parts around openings, corners or ceiling where cracking is concerned, possibility of cracking remarkably reduces.

Hyper Net 60

Hyper Net 60

Hyper Net 60

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2. The proposal on compensation of cracking caused by drying shrinkage

Drying shrinkage cracking occurs by the combination between the transformations caused by dissipation of water according to the drying and the retention. There are two methods to compensate the drying shrinkage cracking; one is to dose and mix an expansive additive or a shrinkage reducing agent into concrete when it is produced, and the other is to apply a shrinkage reducing agent to the surface of the hardened concrete as soon as the concrete form is removed.

Method of dosing when concrete is produced (Ready mixed concrete)　

The following expansive additive or shrinkage reducing agent we propose can compensate the transformation of shrinkage, so that the occurrence of cracking caused by drying shrinkage reduces.

Expansive additive for concrete

Concrete mixed with Hyper Expan, an expansive additive for concrete, appropriately expands on the early stage, and compressive force is introduced into the concrete by retaining materials such as re-bars, which is called Pre-stress Effect. The tensile force generated by drying shrinkage of the concrete etc. is cancelled or deceased by the compressive stress according to the Pre-stress, so that the occurrence of cracking is compensated. Refer to the following figure.

As the family of the expansive additives, the following materials are available. Hyper Expan : Low Dosage Type N-EX : High Early Strength Type Expan : Standard Type

Shrinkage Reducing Agent

Tetraguard, a shrinkage reducing agent, can reduce the drying shrinkage itself according to weakening the tension caused by capillary that is one of main causes of drying shrinkage.

The Effect of Tetraguard

Method of applying a shrinkage reducing agent to the surface of the hardened concrete

By applying Crack Saver, a shrinkage reducing agent, to the surface of concrete of which the form is removed, the Crack Saver penetrates into clink of capillary, reduces the tension of the capillary that is generated by dissipation of water, and finally reduces the drying shrinkage.

Application of Cracksaver

Application Example (Pier of bridge)

Application example (Box Culvert)

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3. The proposal on compensation of cracking caused by heat generated by reaction of hydration

Recently, concrete structures are getting bigger or larger and the application like huge amount of concrete is rapidly cast increases, so that force of heat caused by the reaction of hydration in concrete generates cracking or gives concrete some bad influences which cannot be ignored on the design of concrete. Hyper Expan M can control the generation of the heat caused by the reaction of the hydration on the early stage and can gradually compensate the shrinkage generated at the decrease of concrete temperature with its expansion.

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4. Autogenous cracking

Autogenous cracking can be compensated by dosing an expansive additive for concrete or a shrinkage reducing agent to concrete with low ratio of cement quantity, in which the autogenous cracking occurs easily.

Expansive additive for concrete : Hyper Expan, N-EX, Expan

Shrinkage reducing agent : Tetraguard, Crack Saver

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